DEC 1973

INTERNATIONAL

LABOUR

OFFICE

STUDIES AND REPORTS
Series F (Industrial Hygiene) No. 13

SILICOSIS
RECORDS OF THE INTERNATIONAL CONFERENCE
HELD AT JOHANNESBURG
13-27 AUGUST 1930

GENEVA
1930
Published in the United Kingdom
For

the

INTERNATIONAL

LABOUR

OFFICE

(LEAGUE

OF -NATIONS*

By P . S. K I N G & SON. L t d .
Orchard House, 14 Great Smith Street, Westminster, London, S. W. 1

PRINTED

BY ALBERT

KUNDIG

GENEVA

CONTENTS
Page
INTRODUCTION

L I S T OF M E M B E R S

L I S T OF O B S E R V E R S

PART I

REPORT

OF PROCEEDINGS

Opening Sitting, 13 August 1930, 10 a.m
First Sitting, 13 August 1930, 3.30 p.m
Second Sitting, 15 August 1930, 2.30 p . m
Third Sitting, 16 August 1930, 9.45 a.m
F o u r t h Sitting, 18 A u g u s t 1930, 9.30 a.m
Fifth Sitting, 18 August 1930, 2.30 p . m
Sixth Sitting, 19 August 1930, 9.30 a.m
Seventh Sitting, 19 August 1930, 2.30 p . m
E i g h t h Sitting, 20 A u g u s t 1930, 9.30 a . m
N i n t h Sitting, 20 August 1930, 2.30 p.m
T e n t h Sitting, 23 August 1930, 9.30 a.m
Eleventh Sitting, 25 August 1930, 9.30 a.m
Twelfth Sitting, 26 August 1930, 9.30 a.m
T h i r t e e n t h Sitting, 27 August 1930, 10 a.m

9
15
26
32
44
51
59
68
72
80
85
86
94
102

P A R T II

PAPERS

PRESENTED

T O T H E CONFERENCE

Historical Review of Mining Conditions on t h e W i t w a t e r s r a n d a n d t h e
Changes which have taken place since the E a r l y Days of the Fields.
B y A. E . P A Y N E , H A N S P I R O W a n d F R A N K G. A. R O B E R T S

107

The N a t u r e a n d Source of D u s t in Mine Air, together w i t h a Brief
Reference t o those Operations which produce Dust. B y A. F .
MCEWEN

and J. B U I S T

129

Methods for Determining t h e D u s t in Mine Air, as practised on t h e
Witwatersrand.

B Y JAMES BOYD

141

Measures for P r e v e n t i n g t h e F o r m a t i o n of Dust, a n d Precautions
designed t o P r e v e n t Persons Inhaling such D u s t as m a y b e formed,
and t h e Regulations relating thereto. B y MALCOLM FERGUSSON
and W A L T E R

SCOTT

151

The General Question of Mine Ventilation a n d Air Renewal, including
References t o t h e H e a t and H u m i d i t y Problems. B y G. A.
WATERMEYER

and

REES

172

A Review of t h e History of Silicosis on t h e W i t w a t e r s r a n d Goldflelds.
.

178

Aetiology of Silicosis (Dust-Phthisis). B y A. MAVROGORDATO. . . .
A Preliminary S t u d y of t h e Pathology of Silicosis as Seen on t h e Wit-

B y L. G. I R V I N E , A. MAVROGORQATO and H A N S P I R O W

209

w a t e r s r a n d . B y A. S U T H E R L A N D STRACHAN a n d F . W . S I M S O N

223

The Clinical Pathology, Radiology a n d S y m p t o m a t o l o g y of Silicosis.
I. — T h e Clinical Pathology of Silicosis. B y L . G. I R V I N E ,

249

W . SIMSON a n d A. S U T H E R L A N D

II. — The Radiology

STRACHAN

a n d Symptomatology

B y L. G. I R V I N E a n d W . S T E U A R T

251

of Silicosis.
269

CONTENTS

Page
Silicosis in Australia.

B y K E I T H R . MOORE

295

Silicosis in Belgium. B y Dr. D . G L I B E R T
Silicosis in Canada. B y J . G. CUNNINGHAM
Silicosis in G e r m a n y :
I. — P r e s e n t S t a t e of t h e Silicosis Problem in Germany.
B y Prof. A. B Ö H M E

II.—

313
317

339

Types of D u s t a n d Silicotic L u n g s : Comparative
Statistical a n d Clinical Roentgenological Researches in
B y Prof. K O E L S C H a n d D r . K A E S T L E . . .

369

Silicosis in Great Britain. B y E . L. M I D D L E T O N
Pneumoconiosis i n Italy. B y Prof. GIOVANNI LORIGA
Appendix : Pneumoconiosis in Marble W o r k s . B y Dr. GIACOMO

Bavaria.

384
481

BIANCHI

505

P u l m o n a r y Asbestosis. B y D r . D . LOVISETTO
Clinical a n d Radiological Notes on Pneumoconiosis d u e to
Asbestos.

B y D r . G. M U S S A

509

Radiological a n d Clinical Studies effected a m o n g s t t h e Carrara
Marble Workers. B y Dr. L. T U R A N O
Silicosis in t h e Netherlands. B y Dr. W . R . H. K R A N E N B U R G . . . .
Silicosis in t h e U n i t e d S t a t e s . B y D r . A L B E R T E . R U S S E L L
Appendix:
Inhalation of Asbestos D u s t s : I t s Effect upon P r i m a r y
T u b e r c u l o u s Infection B y L E R O Y
E. CUMMINGS

U. GARDNER and

509
512
535

DONALD

T h e Medical E x a m i n a t i o n of N a t i v e Labourers on E n g a g e m e n t a t t h e
Gold Mines of the W i t w a t e r s r a n d . B y A. I. GIRDWOOD . .
S a n a t o r i u m T r e a t m e n t of Miners' Phthisis P a t i e n t s . B y A. D . P R I N G L E
Personal Experiences of Miners' Phthisis on t h e R a n d from 1903 to
1916.

506

B y A. H . W A T T

563

566
572
589

T h e Functions of t h e Miners' Phthisis Medical Bureau a n d t h e General
System of Medical E x a m i n a t i o n s Conducted under t h e Miners'
Phthisis Act.

B y L . G. I R V I N E

597

T h e Functions a n d Experience of t h e Medical Board of Appeal appointed
under t h e Miners' Phthisis A c t . By M E M B E R S OF THE A P P E A L
BOARD

610

Statistical Account of the Incidence a n d Progression of Silicosis amongst
the Gold Miners of t h e W i t w a t e r s r a n d . B y D . S P E N C E F R A S E R
a n d L. G. I R V I N E

618

Review of t h e Development of Silicosis Legislation in South Africa,
with P a r t i c u l a r Reference to Compensation. B y A. B . D u T O I T ,
GEORGE E. BARRY and NORMAN P . DALE

The Actuarial Valuation of t h e O u t s t a n d i n g Liabilities under t h e
S o u t h African Miners' Phthisis A c t . B y D . S P E N C E F R A S E R . .
T h e W o r k of t h e Miners' Phthisis Board a n d of t h e Mining I n d u s t r y in
Providing E m p l o y m e n t for Silicosis Sufferers a n d their Dependants.
B y C. J . W I L L I A M S , C. S. R A A T H a n d B . G . O . O R P E N

648

675

687

INTRODUCTION

The International Labour Office has never under-estimated the
importance of the silicosis problem, in which it has manifested a
lively interest since its inception. It has in fact carefully followed
scientific research effected, as well as the reports of practical men
in the different countries, and it has made every effort to assemble
and collect the extremely scattered scientific data relative to the
subject.
Gradually, thanks to national and international meetings of doctors
or experts in industrial pathology, and thanks especially to results
obtained in those countries in which silicosis is legally compensated
as an occupational disease, it has been rendered possible for the
Office to tabulate completely the data obtained, and to draw up
a programme of activity.'
Simultaneously the workers' organisations affected have inscribed
the silicosis problem on the agenda of their meetings. Notably
is this true of the national stoneworkers' associations and in
particular their International Federation which, since 1921, has at
each of its meetings voted resolutions demanding that silicosis
should be considered as an occupational disease and compensated
as such. Other workers' organisations such as those of the miners,
pottery workers, etc., have also adopted motions in support of
this demand. In 1925 the international secretariat of the stoneworkers' organisation placed before the International Labour
Office a request for inclusion of respiratory diseases amongst those
entitling the worker to compensation.
On reception of this request the Hygiene Service of the Office
in January 1926 addressed to a certain number of experts a questionnaire accompanied by a note explaining the object of the
enquiry. The replies obtained were embodied in a report submitted
to the Correspondence Committee on Industrial Hygiene during
its meeting at Düsseldorf in 1928. The experts assembled by the
Office engaged in a lengthy discussion on the problem of silicosis
and adopted a resolution in which they requested the Office to
delay inscription of silicosis in the list of diseases to be compensated

INTRODUCTION

since, in their opinion, the problem in question was one which
presented special complication and difficulty. Two points especially
were said to call for further research, that is to say, precise diagnosis
of the disease, and determination of the indispensable elements for
establishing the degree of capacity of the worker to continue his
work. The Committee asked the Office to continue the enquiry
undertaken and to submit to it at a future session the data
assembled.
Meanwhile Mr. Butler, Deputy-Director of the Office, during
his journey in South Africa, discussed with those interested in the
question the suggestion made by Dr. Orenstein, of calling an International Conference on Silicosis in Johannesburg.
Thanks to the generous aid of the Chamber of Mines it was
possible to carry out this scheme, and the first proposal as to the
holding of such a Conference was made to the Governing Body in
June 1928. The Governing Body then agreed that a Conference
of experts should be convened to study the medical aspects of
silicosis and suggested that a Conference held at Johannesburg
would afford an opportunity for experts from other countries
to examine the remarkable work done by the Miners' Phthisis
Bureau on the Rand. The Governing Body also expressed the hope
that such a Conference might bring about closer international
co-operation in the study of the disease and that it would endeavour
to organise a programme of research on the subject.
In March 1929 the Governing Body approved a provisional agenda
for the Conference as follows:
(a) Medical aspects of silicosis (pathological and clinical);
(b) Preventive measures;
(c) Compensation.
Scientific investigations on the subject engaged in chiefly in
German and in English speaking countries, the work effected by
Committees appointed by the British Government in recent years,
the results of the discussion of the report submitted to the International Congress of Occupational Diseases at Lyons, 1929—a discussion which dealt chiefly with the research effected by the Medical
Research Bureau and the Miners' Phthisis Bureau in South Africa—
as well as research engaged in in Germany, all these contributed
naturally to paving the way for the calling of a Conference exclusively concerned with the problem of silicosis.
This Conference, in accordance with the decision of the Governing
Body, met in Johannesburg from 13 to 27 August 1930.

INTRODUCTION

In view of the length and cost of the journey to South Africa
the funds available only allowed of the appointment of a limited
number of experts. In the course of consultation with the Governments it, however, became apparent that certain Governments
were willing to pay the expenses of delegates chosen by the Office
in agreement with them, and it was therefore possible to issue an
additional number of invitations and to increase both the size
and the authority of the Conference. The Office is extremely
grateful to the delegates who accepted its invitation, to the Governments which bore the expenses of certain delegates, and to the
British Medical Research Council which undertook to defray the
expenses of Professor Kettle.
The Office records with interest and appreciation that the United
States, in accordance with its policy of participation in the activities
of the International Labour Organisation, was represented by
two delegates, the expenses of one of them being borne by the
United States Government.
In order that the Conference might secure the fullest possible
information on the work done in South Africa, there were also
appointed a number of South African observers, who were able to
be present at the meetings and to assist in the elucidation of
questions in regard to which they were specially competent.
As soon as the delegates had been appointed, each was asked
to write a paper either on the problem of silicosis or pneumonoconiosis in his particular country or on that particular scientific
aspect of the question with which he was specially competent to
deal.
Certain firms at Johannesburg also kindly assisted the Office
by the loan of microscopes, an epidiascope, and screens for the
showing of radiographs, required for the exhibition of the slides
and other specimens brought by the different experts to illustrate
certain phases of their work.
The firm of Kodak, South Africa, presented the members of the
Conference with an album containing photographs of anatomicalhistological preparations and radiographs prepared by the services
of the Miners' Phthisis Bureau and of the Medical Research Bureau.
The delegates were also given opportunities of visiting these two
institutions, as well as a gold mine and the sanatorium for fibrotic
patients, and of studying the system of medical examination in
force for native workers before they are passed for service in the
mines.
*

INTRODUCTION

Mr. Phelan, Chief of the Diplomatic Division, was appointed
by the Office to be in general charge of the organisation of the
Conference; Dr. Carozzi, Chief of the Industrial Hygiene Section,
as technical expert of the Office ; and Messrs. Weaver and Little
and Miss Macrae to assist in the secretarial work. The material
work of the secretariat was performed by members of the staff
of the Chamber of Mines who were generously placed at the disposal
of the Conference by the Chamber and who worked under the
direction of the secretarial staff of the Office.

LIST OF MEMBERS
Australia
Dr. CHARLES BADHAM, Medical Officer of Industrial Hygiene, New
South Wales Department of Public Health.
Dr. W. E. GEORGE 1, Medical Ofiicer-in-Charge, Bureau of Medical
Inspection, Broken Hill.
Dr. KEITH R. MOORE ^"Director of the Division of Industrial Hygiene,
Commonwealth Department of Health, Member of the Committee
on Industrial Hygiene of the International Labour Office, t' '""-'
Canada
Dr. GRANT CUNNINGHAM, Director of the Division of Industrial
Hygiene, Department of Health, Ontario. ^ - ., .
Germany
Professor Dr. BÖHME, Director, Augusta Hospital, Bochum.
Professor Dr. KOELSCH, State Industrial Medical Officer, Munich.
Great Britain
Dr. S. W. FISHER °, Medical Inspector of Mines.
Professor ARTHUR J. HALL, Professor of Medicine at Sheffield University, Chairman of the Medical Research Council Committee to
investigate pulmonary diseases from silica and other dusts.
Professor E. H. KETTLE, Professor of Pathology, St. Bartholomew's
Hospital Medical School, University of London.
Dr. E. L. MIDDLETON 3, Medical Inspector of Factories.
Italy
Professor Dr. GIOVANNI LORIGA, Chief Medical Inspector of Factories,
Member of the Committee on Industrial Hygiene of the International
Labour Office.
Netherlands
Dr. W. R. H. KRANENBURG, Medical Adviser to the Labour Inspectorate, Member of the Committee on Industrial Hygiene of the
International Labour Office.
1
2
8

Representing New South Wales Government.
Representing Federal Government.
Representing British Government.

LIST OF MEMBERS AND OBSERVERS

Union of South Africa
Mr. A. B. Du TOIT, Chairman, Miners' Phthisis Board.
Dr. A. I. GIRDWOOD, Chief Medical Officer, Witwatersrand Native
Labour Association, Ltd.
Dr. L. G. IRVINE, Chairman, Miners' Phthisis Medical Bureau.
Sir SPENCER LISTER, Director, South African Institute for Medical
Research.
Dr. A. MAVROGORDATO, Fellow in Industrial Hygiene, South African
Institute for Medical Research.
Dr. A. M. MOLL, Chairman of the Miners' Phthisis Medical Appeal
Board.
Dr. A. J. ORENSTEIN, Superintendent of Sanitation, Rand Mines, Ltd.
Dr. Hans PIROW, Government Mining Engineer.
Mr. F. G. A. ROBERTS, Technical Adviser, Transvaal Chamber of
Mines.
Dr. W. STEWART.

United States of America
Dr. L. V. GARDNER, Trudeau Sanatorium. '
Dr. ALBERT E. RUSSELL 1 , United States Public Health Service.

LIST OF OBSERVERS
Dr.

PETER ALLAN, Medical Superintendent, Nelspoort Sanatorium,
Cape Province.
Mr. G. E. BARRY, Legal Adviser, Transvaal Chamber of Mines.
Mr. JAMES BOYD, Secretary, Anglo-American Corporation of South
Africa.
Mr. J. BUIST, Senior Dust Inspector, Transvaal Chamber of Mines.
Dr. E. H. CLUVER, Department of Public Health, Pretoria.
Mr. NORMAN P. DALE, Secretary, Miners' Phthisis Board.
Mr. MALCOLM FERGUSSON, Chief Inspector of Mines.
Mr. D. SPENCE FRASER, Actuary to the Miners' Phthisis Board.
Mr. W. GEMMILL, General Manager, Transvaal Chamber of Mines.
Mr. G. R. HEYWOOD, Manager, Rose Deep, Ltd.
Mr. H. R. HILL, Consulting Engineer, Union Corporation, Ltd.
Mr. A. F. MCEWEN, Chief Chemist, Transvaal Chamber of Mines.
Dr. A. J. MILNE, Medical Officer of Health, Johannesburg.
Dr. ALEXANDER MITCHELL, Secretary of Public Health, Department of
Public Health, Pretoria.
Mr. B. G. ORPEN, New Consolidated Gold Fields of South Africa, Ltd.
1

Representing United States Government.

LIST OF MEMBERS AND OBSERVERS

Dr. A. D. PRINGLE, Medical Superintendent, Transvaal Miners'
Phthisis Sanatorium.
Mr. C. S. RAATH, Member, Miners' Phthisis Board.
Mr. J. P. REES, Dust and Ventilation Officer, Transvaal Chamber of
Mines.
Mr. F. G. A. ROBERTS, Technical Adviser, Transvaal Chamber of Mines.
Mr. WALTER SCOTT, Assistant Consulting Engineer, Rand Mines, Ltd.
Dr. F. W. SIMSON, Pathologist, South African Institute for Medical
Research.
Dr. J. M. SMITH, Miners' Phthisis Medical Appeal Board.
Dr. A. SUTHERLAND STRACHAN, Pathologist, South African Institute
for Medical Research.
Dr. R. M. TRUTER, Miners' Phthisis Medical Appeal Board.
Professor G. A. WATERMEYER, Professor of Mining, University of
Witwatersrand.
Dr. ANDREW H. WATT, Medical Officer, Rand Mutual Assurance
Company, Ltd.
Mr. C. J. WILLIAMS, Deputy Chairman, Miners' Phthisis Board.

REPORT OF THE PROCEEDINGS
OPENING
SITTING
Wednesday, 13 August 1930, 10 a.m.
Chairmen: Sir

WILLIAM DALRYMPLE

and Mr. E. J.

PHELAN

The opening sitting of the International Silicosis Conference was
held in the Selborne Hall, Mr. E. J. Phelan, Chief of the Diplomatic
Division of the International Labour Office, was introduced by Sir
William Dalrymple.
Mr. E. J. Phelan : My principal function this morning is to ask the
Minister, Mr. Sampson, to open formally this Conference; but it might
be interesting to you (and it would certainly be fair to him) if I first
indicated briefly why the International Labour Office of the League of
Nations in Geneva convened this Conference and what we expect it to do.
The International Labour Office is the executive secretariat of the
International Labour Organisation,. The International Labour Organisation is a society of fifty-five States. It is a purely official body which is
the result of fifty-five States in the world having entered into a contract
to collaborate for the improvement of conditions of labour. It began as
you probably know at the same time as the League of Nations, and its
Constitution is to be found in the Treaties of Peace. One of its original
Members is South Africa. The Organisation has to have a secretariat—
an executive to carry out its decisions; that executive is the International
Labour Office, which I have the honour to represent here to-day.
Now, the International Labour Office is, as I have said, an executive
body. It does not take decisions; decisions are taken by the International Labour Conference, which meets once a year and to which
every member of the Organisation—that is to say, every one of the
fifty-five Member States—sends a delegation composed of Government
representatives, representatives of the workers and representatives of the
employers. They compose the annual Conference in which is vested
what I may call the sovereign power of the Organisation and they alone
can formulate decisions, which later become international treaties.
I want to make that clear, because the conference which Mr. Sampson
is going to open in a few minutes is not that Conference; it is not the
General Conference of the Organisation which can adopt Draft Conventions and Recommendations.
Before that General Conference actually meets to formulate decisions
which Governments must take into consideration and which Governments, if they ratify, must observe, the function of the International
Labour Office is to see that it shall have the fullest possible information at
its disposal ; therefore, long before the International Labour Conference

REPORT OF PROCEEDINGS

considers the taking of any decisions, the Office in Geneva is busy
collecting, summarising and analysing information, translating laws
and regulations, and attempting to make as complete a survey as possible
of all the law and practice bearing on the question which, later, the International Labour Conference will discuss. This preparatory work of the
Office covers the whole area of labour problems. The programme of the
Organisation which is laid down in the Preamble to Part XIII of the
Treaty of Peace is of the most comprehensive character.
I am not going to discuss that programme this morning; but it does
contain, as you would naturally expect it to contain, a very specific
reference to industrial disease ; and therefore, among the studies which
the Office is constantly carrying on with the ultimate object of some day
or other going to the International Labour Conference for discussion
and a decision, is the question of industrial disease. One section of the
organisation of the Office is specially devoted to that work, and as its
head we were fortunate enough to secure ten years ago a very distinguished European authority, Dr. Carozzi, who is with me here in
Johannesburg to-day as the technical expert of the International Labour
Office. The very important work which the Office has already done in
the field of the study of industrial disease is due above all to Dr. Carozzi's
vision, energy and intelligence. He has, in the course of ten years, built
up a unique organisation; he has created a network of experts and
technicians scattered all over the world, with whom he is in constant
contact by correspondence; and, since science need not regard the
political differences which sometimes separate political units, that network of medical correspondence covers, not only the members of the
International Labour Organisation, but certain very important units
which lie outside it, like the United States of America and Russia.
Dr. Carozzi's work takes a material form in the publication every three
or four months of a bibliography of everything he is able to discover
which has been published on the subject of industrial hygiene. He is
able to supply the Government services of the different countries and
experts in industrial hygiene with some two or three thousand references
a year, so that each of them, in dealing with his own work, can keep
abreast of the work which is being done elsewhere. He has also been
able to undertake the immense task of compiling an Encyclopaedia of
Occupation and Health, the first volume of which will appear in a few
months. To give you some idea of the field covered and the amount
of work he has performed, it will be a volume of something like 2,200
pages.
You haAre now, I hope, some idea of the organisation which lies at the
origin of this Conference-—the International Labour Office, with its
general responsibility for securing better conditions of labour, and the
Industrial Hygiene Section with its particular interest in industrial
disease.
But the Office does not by any means work only on paper. We
have had the great advantage of having had at the head of the Office
a great international figure, Mr. Albert Thomas, a man with outstanding
qualities of leadership and a unique capacity for achievement. He
realised from the beginning the danger of the Office becoming a mere
Academy and the necessity that the officials of the Office, whenever the
occasion might arise, should get away from purely paper work and gain as
much direct experience of the problems with which we are dealing as possible. It was in pursuance of this policy that three years ago the DeputyDirector of the International Labour Office, Mr. Butler, undertook a
visit to South Africa in order to become familiar with the labour problems

OPENING SITTING

of South Africa, and with the object of intensifying relations between
South Africa and the International Labour Organisation. During his
visit here in Johannesburg, in conversation with Mr. Gemmili and
other representatives of the Chamber of Mines, and Dr. Orenstein, his
attention was drawn to the unique collection of material which had been
made by the Chamber and by the officials of the Government in connection
with silicosis. He saw at once the importance of making this knowledge
internationally available and he accordingly discussed with Mr. Gemmili
and Dr. Orenstein the possibility of discovering some method whereby
the scientists and the officials of the other countries might be able to
profit by the immense experience of that disease which is centred in this
city. Out of those conversations grew the present Conference: out of
those conversations grew the suggestion that it might be possible to
convene an International Conference of experts to study the medical
aspects of silicosis and the measures for its prevention.
The proposal was laid before our Governing Body, which is the
executive council of the International Labour Office, and was approved
by them; but South Africa being a very long way away from Geneva,
and the International Labour Office being a far from rich body, it would
have been difficult perhaps to have held this Conference if it had not been
for the generosity of the Chamber of Mines; and I should like to-day,
on behalf of the International Labour Office, formally to thank the
Chamber of Mines for the generous assistance which has made the holding
of this Conference possible. I should like also to ask Mr. Sampson to
convey to the Government of the Union of South Africa the appreciation
of the International Labour Office of the facilities which the South African
Government has given to us, and of the generous way in which, as soon
as it was consulted, it offered to give every assistance to the Conference
and to lay before it all the material which it has in its possession.
But before I ask Mr. Sampson formally to open the Conference, the
origin of which I have described, I would like to draw attention to an
aspect of it which is not purely medical. This Conference, distinguished
as it is by the scientists who have come from different countries in
Europe, Africa, Canada, Australia and the United States of America,
represents perhaps a more remarkable body of expert opinion than has
ever come together to deal with the question of an industrial disease;
but, important and remarkable as it may be in that respect, it is still
more important and more remarkable in another respect. We in Geneva
often feel that we are a long way from the distant countries, and I have
no doubt that South Africans often feel they are a long way from Geneva
and that Geneva is dealing with problems which are remote from South
African preoccupations and that, to put it quite frankly, the League of
Nations spends the greater part of its time discussing purely European
problems. That is only a half truth. It is true that the League of
Nations and the International Labour Organisation do spend a great
deal of time discussing problems which are of major European interest;
but it is not true that these problems, or the solution of them, has not
a direct interest to the more distant countries. It is unfair to make
these observations as a criticism of the League of Nations or of the
International Labour Organisation. The League of Nations is not an
international dictator; the League of Nations is not a super-State; the
League of Nations is not some Martian body which meets in Geneva and
decides what is good for France, or Italy, or South Africa or Australia.
The League of Nations is exactly like the South African Parliament or
the British Parliament or the German Parliament. It is in nowise different
from the members which compose it; and when it meets in Geneva, its

REPORT OF PROCEEDINGS

activities are dictated by the influence of its most active members. The
League of Nations does precisely what a Parliament would do when a
majority in the Parliament decides on a certain course of action, and
therefore it is not a just criticism of the League of Nations to say that
its activities are too European. But it is perhaps a regrettable fact—
a fact, however, for which the less active members of the League are
themselves responsible and not some super-body.
Now, what is the corrective to that ? What is the way in which the
League of Nations can be led to pay more attention to non-European
questions and to become really in its activities a more world-wide organisation ? The only way in which that can be done is for the non-European
States to bring their problems to Geneva and insist, as the European
States do, that their problems shall be dealt with. South Africa has
now taken the lead by furnishing an example of how this can be done.
The fact that this Conference is meeting in South Africa is therefore
a historic occasion. It is the first Conference convened by the League
of Nations which has met outside of Europe. It is true that the first
International Labour Conference met in Washington, in the United
States of America; but the first International Labour Conference was
not convened by the International Labour Organisation nor by the
League of Nations. It was settled in the Treaties of Peace, and it has
not met in Washington since, for the simple reason that the United
States did not join the League of Nations or the International Labour
Organisation; and with the disappearance of the United States of
America, the balance between the European and the non-European sides
of the League was perhaps weighted in favour of Europe, so that European problems have played a predominant part in the discussions of
Geneva.
To-day, for the first time, Mr. Sampson is going to open an International Conference officially convened by the International Labour
Office of the League of Nations, meeting outside Europe and having as
its object the study of a problem that is not by any means wholly
European in its interest. For that reason, I think that I may say that
this Conference marks a historic point in the development of the
League's machinery. It shows, I think, too, that the South African
Government has understood the real meaning of Membership of the
League. The Covenant is not a final nor an absolute guarantee of the
world's peace or of industrial progress or of anything else. The League
is, and can be, nothing more than its Members make it. But the
difference between the League world and the pre-League world is this:
that in the pre-League world every State guided its policy in its own
purely selfish interest. In the League world we hope that States will
more and more consider, not what they can get out of the League, but
what they can put into the League for the common good of the whole;
and this Conference is a gesture of that kind. South Africa has asked
these experts, through the intermediary of the International Labour
Office, to come to Johannesburg in order to see what contribution South
Africa can make towards the solution of a grave medical problem.
I cannot speak for the experts, but my impression is that South Africa
has more to give than she can hope to receive. She has had a longer
experience and she has accumulated a greater collection of material
going back for a longer period than perhaps any other country. But the
essence of South Africa's gesture is her desire to put at the disposal of
humanity as a whole the peculiar knowledge which she has to offer for
the solution of a very pressing problem in the industrial world. I can
assure Mr. Sampson that that gesture is appreciated in Geneva to its

OPENING SITTING

fullest; and though possibly South Africa may gain little direct benefit
from this Conference, her reward is that she will have contributed to the
good of humanity as a whole. I have now great pleasure in asking
Mr. Sampson to open formally this International Silicosis Conference.
(Applause.)
The Hon. H. W. Sampson, M.P. (Minister of Posts and Telegraphs) :
The problem of silicosis has been one of considerable gravity in South
Africa, and the Government of the Union has therefore special reason
to welcome thé assembly in Johannesburg of this International Silicosis
Conference.
Our Chairman, Mr. Phelan, has dealt very minutely with the particulars
of the preliminaries that led up to this Conference, and has saved me the
necessity of repeating those matters. I want to thank him very much
for his exposition of the reasons for which the League of Nations exists.
After all, as we get further and further from the war time of the past,
commercialism will sometimes ask: what do we get out of the League of
Nations ? It is well we have one in our midst this morning who has
explained to this assembly the spirit which led up to the formation of
that body and the spirit in which this work is to be carried on in the
future. I am quite sure that this audience is particularly interested in
that matter, and I am sure they realise the necessity of getting the world
closer together in dealing with world problems apart from the problems
in regard to their own special countries. He has explained very fully
how you, Gentlemen, come to be here this morning, and it is my duty to
extend to you all a very cordial welcome in the name of the Government
of the Union of South Africa. I welcome especially those who have
come long distances to attend this Conference. Their presence here is a
signal proof of the great international fellowship in scientific investigation and research which overrides all national boundaries, and affords so
hopeful a manifestation of that growing international spirit which the
International Labour Organisation embodies.
The presence of the representatives of so many countries and the high
standing of the members of the Conference affords also an indication
of the widespread distribution of the menace of silicosis and of the serious
light in which it is regarded by the health authorities of many countries.
Silicosis is indeed, I suppose, individually perhaps the most important
of all occupational diseases and one which, as we know, is a danger to
health and life in many industries besides that, of metal mining. The
problem of " silica risk " and how it is to be countered forms to-day one
of the most important preoccupations of industrial hygiene.
To the metal miner who works in certain kinds of hard siliceous rock
the disease has everywhere been a special danger, and we in South Africa
fully realise that our local problem is only part of a world-wide problem.
We realise that the prominence which the disease has attained in this
country has been due primarily to the great extent and unique geographical concentration of the great gold-bearing reef of the Witwatersrand,
and to the extraordinarily rapid development of the mining industry
which is based upon it, and the magnitude which that industry has
attained.
The problem has thus been with us at once larger and more sharply
concentrated and the deaths and suffering caused by that disease have
been more clearly apparent than might have under other circumstances
been the case.
It is impossible to state with any degree of définiteness what the entire
ramification of the disease here has been. Statistics (and many of them

REPORT OF PROCEEDINGS

not comparative) are only available since 1911. But the enormous
burden which the industry has to bear of nearly £1,000,000 per annum,
totalling, I believe, some £15,000,000 for compensation claims since 1911
and arising chiefly from an average of 21,000 to 30,000 whites employed
underground during that period, will convey to your minds the suffering
to the victims and loss to the industry.
It took a good many years before the gravity of the situation in respect
of silicosis was fully recognised in this country; but one may, I think,
fairly state that from the time that it was fully realised neither the
Government of the Union nor the mining industry have relaxed their
efforts to control the situation.
The Union Government definitely recognised " miners' phthisis " as
an occupational disease in 1911, and since that date no fewer than nine
Acts of Parliament have been passed dealing with the matter of compensation to miners affected by silicosis, or to the dependants of deceased
miners. From time to time also there have been incorporated in the
Mining Regulations a large and increasing number of detailed provisions
aiming at the prevention of the disease.
The mining industry has closely co-operated with the Department of
Mines in the investigation and trial of preventive measures, and this fact
has greatly facilitated the development of a systematic preventive policy.
For many years one seemed to see no very marked amelioration of the
situation, although one realises that with such a disease as silicosis it
takes a considerable time before changes in occupational conditions show
their full effect.
I am glad now to learn from the Chairman of the Medical Bureau
that the annual number of the cases of silicosis which are arising to-day
in only about one-third of the number that were arising fourteen or
sixteen years ago, and that a substantial improvement in the situation
has occurred within the last three years. This is very welcome news,
but we should wish for something even better, and if you, Gentlemen,
can help us to do better we shall be very grateful.
It is perhaps too much to hope for that your deliberations will lead to
any very great reduction in the incidence of silicosis; only a larger
expenditure in preventive measures than many of our older mines are
able to afford and continue to work can do that; but it will save many
lives and much suffering, besides being of great financial assistance to
the industry, if means can be found of arresting the disease or of preventing silicotic sufferers from infection with the tubercular germ. This we
have hitherto tried to do by the arbitrary method of forcing a man to
leave underground work; but the problem of finding him alternative
employment is a difficult one, ranking, as he does, among the unfit, and
leads to constant demands for more compensation.
I observe from the provisional programme of your discussions that
every aspect of the silicosis problem will be dealt with. I am sure that
this conjunction of the trained minds of many countries, each of you with
a diverse and varied experience of the question, may be expected to
have fruitful results. I have every confidence that this Conference will
advance the knowledge of the causation and prevention of silicosis to a
great degree. After all, it is prevention that counts most of all, and it is
to the medical experts that we look for wise counsel in that direction.
I wish you, Gentlemen, every success in your important task, the results
of which, I am sure, will mark an important stage in the ultimate solution
of this grave question. I have pleasure in declaring this Conference open.
(Applause.)

[

FIRST SITTING

The Conference was also addressed by Dr. Keith Moore (Australia),
Dr. Grant Cunningham (Canada), Professor Böhme (Germany), Dr.
Middleton (Great Britain), Professor Loriga (Italy), Dr. Kranenburg
(Netherlands) and Dr. Gardner (U.S.A.) who expressed their thanks to
the South African Government for the welcome which it had offered.
(The Conference adjourned at 12 noon.)

FIRST

SITTING

Wednesday, IS August 1930, 3.30 p.m.
Chairmen: MR. E. J. PHELAN and DR. L. G. IRVINE

Mr. E. J. Phelan: The first point is the election of the Chairman of
the Conference.
ELECTION OF CHAIRMAN

Dr. Middleton proposed the election of Dr. Irvine as Chairman.
Dr. Gardner seconded this proposal.
Dr. Irvine was unanimously elected Chairman.
The Chairman read the following telegram received from Mr. Albert
Thomas. Director of the International Labour Office:
Please convey hearty greetings to Delegates and warmest wishes
for a successiul and fruitful conference. ALBERT THOMAS.
He also read the following letter received from Mr. Thomas:
LEAGUE OF NATIONS.

INTERNATIONAL LABOUR OFFICE,
GENEVA.

SIR,

On this, the first occasion upon which the International Labour
Office has convened a Conference outside Europe, I venture to ask
you to convey to its members my warmest wishes for its success,
and to express to the Chamber of Mines my gratitude for the
assistance which is making the holding of the Conference possible.
I feel confident that the labours of experts drawn from four continents cannot but result in a substantial and valuable contribution
towards the solution of the problem of industrial silicosis. The
International Labour Office is happy to be associated with the
Transvaal Chamber of Mines in this attempt to increase the protection of mine workers and workers in other silicotic industries against
the dangers to which they are exposed from this disease.
I shall be grateful to you, Sir, if you will be good enough to
convey my greetings and good wishes to the members of the Conference and to assure them that I shall watch the progress of their
work with the deepest sympathy and interest.
I have the honour to be,
Sir,
Your obedient Servant,
(Sgd.) ALBERT THOMAS.
The President of the
International Silicosis Conference,
Johannesburg.

REPORT OF PROCEEDINGS

The Chairman proposed that this telegram and letter should be
inserted in the Minutes of the Conference. Dr. Orenstein moved that
receipt of this telegram and letter should be acknowledged and the thanks
of the Conference expressed by cable.
The Conference unanimously adopted this proposal.
ELECTION OF VICE-CHAIRMEN

Dr. Loriga proposed the election of Dr. Russell as Vice-Chairman.
Dr. Pirow seconded this proposal.
Dr. Russell proposed Sir Spencer Lister as second Vice-Chairman.
Professor Kettle and Dr. Loriga seconded this proposal.
Dr. Russell and Sir Spencer Lister were unanimously elected ViceChairmen.
PUBLICITY OF PROCEEDINGS

Mr. Phelan: The Conference should decide at once whether its proceedings were to be public or private. He believed that the medical
experts might prefer to conduct their discussions without the presence
of laymen, but they might consider whether the closing session at which
the suggestions and recommendations might be adopted should be
public.
Dr. Middleton proposed that all proceedings should be private.
Dr. Loriga agreed.
The Chairman asked whether medical men not members of the
Conference and representatives of the medical profession should be
excluded.
Dr. Middleton: He was of the opinion that all sittings should be
private unless the Conference otherwise resolved. It might at moments
be useful to hold their discussions before a wider public, but an ad hoc
procedure would allow this to be done.
Mr. Phelan asked whether Dr. Middleton had any objection to the
issue of Press communiqués to keep the public informed of the progress
of the Conference.
Dr. Middleton: Any communiques should be approved by the Conference before they were issued.
Mr. Phelan: It would be difficult to consult the Conference daily for
approval of communiqués, and he suggested that the staff might be
allowed to issue communiqués to inform the Press of the progress made,
but that where any references were made to differences of opinion, the
Conference should first be consulted.
Dr. Macrogordato suggested that a publicity committee be appointed.
Dr. Orenstein: The Resolutions Committee could fulfil this function.
Dr. Cluver: What would be the position of the medical Press ? He
was himself both an observer and the representative of the British
Medical Journal, and the Journal of Industrial Hygiene.
Dr. Orenstein proposed that this question be referred to the Resolutions
Committee.
The Chairman submitted the following text to the Conference:
1. The Conference as such should be regarded as private and
the meetings confined to members and observers, and any publicity

FIRST SITTING

given to its proceedings should be agreed to ad hoc by the Conference
with the exception that a short resume of the daily proceedings may
be issued to the Press by the Secretariat.
2. Dr. Orenstein's proposal that Dr. Gluver's proposal, " a
resumé of the proceedings might be drawn up on behalf of and for
publication in the medical Press subject to the approval of the
Resolutions Committee", be referred to the Resolutions Committee
for a recommendation, is accepted.
The Conference unanimously adopted these proposals.
NOMINATION OF REPORTERS AND OF RESOLUTIONS COMMITTEE

Mr. Phelan: He proposed that the Resolutions Committee should
consist of Dr. Irvine (Chairman), Dr. Russell and Sir Spencer Lister
(Vice-Chairmen), Dr. Moore, Dr. Kranenburg, Dr. Böhme, and
Dr. Orenstein.
He also proposed that reporters should be appointed for the three
groups into which the subject was most easily divided as follows:
(1) Prognosis, After Care and Compensation: Dr. Cunningham,
Dr. Koelsch, Professor Hall.
(2) Preventive Measures: Dr. Loriga, Dr. Badham, Mr. Roberts.
(3) Medical Aspects (to cover Pathology and other subjects separately
if necessary, but to submit a single report): Dr. Orenstein,
Dr. Gardner, Dr. Middleton, Dr. Steuart.
The Chairman put to the vote the appointment of a Resolutions
Committee constituted as proposed by Mr. Phelan.
The Conference unanimously appointed the Resolutions Committee as
proposed.
Dr. Cunningham proposed that South Africa should be represented
by a reporter upon " Prognosis, After-Care and Compensation ".
Dr. Fisher seconded this proposal.
Dr. Orenstein: The South African point of view was that it would be
better for the report to be drawn up uninfluenced by South African
opinion.
Dr. Cunningham: It would be serious to omit all South African
experience.
Mr. Phelan: The discussion would be open to all the members, and
all that was proposed by the South African members was that it should
be summarised impartially by overseas members.
Dr. Cunningham and Dr. Fisher withdrew their proposal.
The Conference unanimously appointed the reporters as proposed by
Mr. Phelan.
Dr. Orenstein: Dr. Steuart, who had been appointed one of the
reporters on " Medical Aspects ", was an observer and not a member
of the Conference.
Mr. Phelan : The International Labour Office was prepared to invite
Dr. Steuart to be a member of the Conference.
Professor Kettle moved that Dr. Steuart should be invited to become
a member.
The Conference unanimously adopted this proposal.
2

REPORT OF PROCEEDINGS
R E P O R T S OF THE P R O C E E D I N G S OF THE CONFERENCE

Mr. Phelan: A summary of the discussions of the Conference would
be prepared b y the Secretariat and roneoed, and members could h a n d
in any corrections which they desired to make. The reports submitted
to the Conference b y the reporters for the three groups would eventually
be published in a volume, which would include the various reports
submitted to the Conference beforehand, and an account of the proceedings. This volume would also be published in French at a later date,
and possibly in other languages. The non-technical discussions would
be reported by the Secretariat. For technical discussions he suggested
t h a t speakers should prepare a summary of their own observations and
hand it in to the Secretariat. In such cases delegates could hand in a
summary in their own languages.
The Chairman asked whether the Secretariat would prepare a s u m m a r y
when the technical discussion was more in the nature of a debate t h a n
of a series of speeches.
Mr. Phelan : In such cases a stenographic note taker would be provided,
and the Secretariat would also take notes. In this way a sufficiently
accurate report would be obtained, which delegates would also have t h e
opportunity of correcting.
Dr. Middleton asked whether the reporters would be required to t a k e
notes of the whole discussion.
Mr. Phelan: A distinction should be drawn between reports of the
discussion and the reports eventually drafted to summarise the discussion.
No disagreement was likely to arise over the summary of the discussion,.
b u t the reports themselves might be controversial. It was therefore
desirable t h a t the reporters should take some notes.
The Chairman suggested t h a t speakers' summaries should be handed
to the Secretariat within twenty-four hours.
PROGRAMME OF THE CONFERENCE

The Chairman: The programme proposed followed a logical sequence,
viz. (1) Preventive Measures, (2) Medical Aspects, (3) Prognosis, After
Care and Compensation. The South African reports were intended to
serve as starting points for discussion, and the relevant parts of other
reports would be taken at the same time. The subject m a t t e r rather
t h a n the papers themselves would be discussed. Papers 1 to 6 were
more occupational in character t h a n medical; anything bearing on t h e
medical aspect could be discussed under the second heading, and anything
bearing upon prognosis and compensation under the third.
T H E CHAIRMAN'S S P E E C H

The Chairman then addressed the Conference as follows:
Gentlemen, I have to thank you most deeply for the signal honour you
have been good enough to confer upon me in nominating me as Chairman
of this International Silicosis Conference. It is an honour which I am
very proud to accept because I view it as a recognition of the place which
the Miners' Phthisis Medical Bureau, whose work I have at the m o m e n t
the privilege to direct, has gained for itself as a pioneer institution in

FIRST SITTING

the field of industrial hygiene. I am only sorry that my predecessor
Dr. Watkins Pitchford, who founded and organised the Bureau fourteen
years ago during a time of stress and difficulty, and who directed its
activities for a period of ten years thereafter, is not here to occupy in my
place a position which he might so adequately have filled.
For myself I accept this honour with much diffidence. Although I
have been in contact with the silicosis problem for eight and twenty
years I am but a humble musket-bearer in the army of the Lord, and,
when I face as I do now this friendly but critical gathering of the chosen
experts in industrial medicine of many countries, I feel much like a
company commander in a battalion of the line who is suddenly called
upon to lead a composite force of all arms in a highly mechanised postwar army. Happily, little or no leading will be called for. But since
you have been good enough to place me here I shall do my best to
discharge the great privilege which you have conferred upon me, and
which 1 esteem most highly.
My first duty is to welcome our visitors in the name of the mining and
medical professions of South Africa as colleagues to meet whom is to us
a very great pleasure and a unique opportunity. The other day when
a solitary male hippopotamus which had wandered from Zululand along
the coastal margin of Natal into the native territories beyond, a lonely
tour of more than two hundred miles, reached a native kraal and rested
with the cattle, the headman of the village gave orders that an ox
should be slaughtered. This is the customary way in native circles to
honour a distinguished visitor. Gentlemen, we hereby figuratively
slaughter our ox in your honour. I hope that we shall establish at
our meetings a close and friendly contact with each other which will
make this Conference a landmark for each of us of good fellowship and
good work done, and will make it also a notable landmark in the history
of the silicosis problem.
That the International Labour Office has called this Conference to
meet at Johannesburg is to us a great satisfaction. But it is a chastened
satisfaction. For while we welcome the opportunity of having the
benefit in the consideration of our local problems of the advice of so
many trained minds, whose experience must in many respects have been
different from our own, yet that satisfaction is tempered by the knowledge that probably the main reason why you have come to us is, that,
owing to the magnitude and the unique concentration of the mining
industry of the Witwatersrand, and to its rapid and intensive development within the space of a generation, the problem of silicosis has been
with us at once of greater gravity, and has had results which have been
more clearly apparent than might have been the case in other countries,
in which the mining communities may be of older standing and individually perhaps relatively smaller and more scattered. Our satislaction
is tempered also by the fact that although after many years of intensive
effort we can claim a very considerable measure of success, we have as yet
reached no final practical solution of the difficult problem of the prevention of silicosis.
It is significant of the local attitude toward " miners' phthisis " that
the initial suggestion to hold this Conference at Johannesburg should
have come from Dr. Orenstein on behalf of the mining industry of the
Witwatersrand, and that the Transvaal Chamber of Mines has actively
co-operated with the International Labour Office and the Government
of the Union of South Africa in making this meeting possible. Since the
time that the gravity of the menace of silicosis was fully recognised there
has been manifest a close co-operation between the Department of Mines

REPORT OF PROCEEDINGS

of the Union Government and the gold mining industry in the investigation and application of preventive measures. This wholesome spirit
animated the work of the first Miners' Phthisis Prevention Committee,
to which we in this country look back as having set on foot a really
energetic and systematic policy of prevention. Our present meeting is
the outcome of the same spirit, which alone can render possible a
satisfactory solution of this grave question.
I do not wish to detain you overlong with preliminaries. You have
come here to see things for yourselves and not to listen. But perhaps
you will bear with me if I offer at the outset a few very general remarks
upon the subject-matter of our programme, as viewed particularly in the
light of our South African experience, inasmuch as this is the only aspect *
of the general problem of silicosis of which I have any direct knowledge.
The papers which have already been contributed to the proceedings of
the Conference are in your hands. Those prepared by local mining and
medical men may appear to bulk largely in the programme, but they are
designed to serve simply as an introduction to the general discussions
on the several aspects of our subject. They will be taken as read, and
will thus provide a short and happy method of disposing of the local
contributors, and of opening the way to discussions, which, as is plain
from the contributions from other countries which have already reached
us, will be enriched by the results of wide and intensive studies of the
general problem elsewhere.
The contributions already received from other countries, together with
others which may be forthcoming, will fit naturally and most profitably
into the course of the relevant discussions of the different aspects of our
subject, and will be of especial value in widening their scope. In South
Africa, so far, the silicosis problem has been practically a mining problem,
and the local contributions are accordingly practically confined to the
subject of the silicosis of the gold miner. The record of experience
derived from other industries and other countries will serve to correct
this apparent limitation. I trust, however, that you will forgive me if
the few remarks I have personally to offer may also appear to have an
unduly local colour.
§ 1. — The topics set down for our discussion follow a logical sequence.
The first main subdivision of our programme deals with the causation
and prevention of silicosis. The first six papers deal accordingly with the
physical and chemical characters of the gold-bearing conglomerate and
the contiguous country rock of the Witwatersrand reef, with the history
of local occupational conditions, the nature of the preventive measures
which have been adopted, and with the general history of silicosis on
the Witwatersrand.
The problem of what constitutes " silica risk " and of how it is to be
countered is obviously fundamental since if that can be solved the
pathology of silicosis becomes of no more and no less special significance
than that of any other disease, and the matter of compensation may be
left to look after itself. The question of the aetiology and prevention of
silicosis is plainly primarily a medical one, and I trust that this Conference
will be able to contribute to the formulation of some definite lead in this
respect, since without a well-informed and convincing lead from the
medical side, the mining engineer or the industrialist must remain at a
loss. As a world-famous engineer said at a recent Empire Mining Congress :
" Let the physiologists tell us plainly what they want done, and we shall
find ways of doing it for them. " Hitherto the physiologists and other
medical people have themselves been pursuing a painful process of
self-education. Are we now in a position to do better ?

FIRST SITTING

We know that certain dusts which contain free silica are phthisisproducing dusts, and that other dusts which also contain free silica are
not, and the accepted view at present is that the difference lies in the
presence in the latter kinds of dust of other constituents, which nullify
the harmful potentialities of silica. The facts are there, but their explanation is still somewhat obscure, although we can picture several
possibilities. And can the facts be applied in a practical way to the
prevention of silicosis, either in mining, or, if not in mining, in other
industries in which " silica risk " exists, and in which dilution with
other " antidote " dusts might be possible ? The line hitherto taken in
South Africa has led far away from any attempt in this direction,
although Dr. J. S. Haldane has more than once called our attention to
its possibilities.
The history of silicosis in South Africa, and indeed in all other countries,
makes sad reading, and to those who have worked in close contact with
the disease throughout, the personal experience has been more sad.
To the actual sufferers it has meant cases of disablement or death which
have run into thousands. I think that those of you who have read the
several local contributions to the history of the subject, to which I
have referred, must have been impressed by the manifest candour
of the writers. Our ten years of ignorance, our further ten years of
partial realisation, hesitation and tentative improvements, our eighteen
years of increasingly energetic effort to deal with the problem have
been set down without extenuation, and make up, I suppose, the common
story of such things the world over, except that with us that story has
been condensed into the period of one generation instead of being spread
out over several or many.
The slow awakening to the gravity of the situation and to the fact
that we have in silicosis a condition which is individually the most
important of all occupational diseases, and one most difficult to deal
with, particularly under mining conditions, is faithfully reflected in these
papers. At the outset this circumstance was due in part to simple ignorance of the character and extent of the danger, in part to the dominance
of the metal mining tradition of those days. The coal mining tiadition
stood then, as now, for ample ventilation to combat the danger of mine
gases. The metal mining tradition, exempt as most metal mines are from
any such obvious and immediate risks, was still content to rely upon
natural ventilation. And there is an immense inertia in tradition the
more so when it has become extensively.embodied in actual material
structure whether above or below ground.
The main lesson of the history of silicosis appears to be that in metal
mines which create a phthisis-producing dust there are just as cogent
reasons for ample ventilation as exist in coal mines, since in the last
resort we are dealing, in an atmosphere laden with impalpable silica dust,
with what is for practical purposes a dangerous gas, perhaps more
extensively dangerous to life in its remote effects than are fire damp or
black damp with their immediate and obvious risks. Had this been
generally realised thirty or forty years ago we should have been spared at
least a large part of our troubles. And although mine ventilation has
for many years received great and increasing attention on these fields
we are still to-day in this respect hampered and handicapped by the
heritage of the old tradition, as embodied in the original layout and mode
of working of the older mines.
It was not until the report of the Miners' Phthisis Medical Commission
was published in 1912 that the widespread character of the menace of
silicosis and the real gravity of the situation were recognised in this

REPORT OF PROCEEDINGS

country, and that year marks the beginning of the really energetic
measures for the prevention of silicosis which have since been taken.
Even so, medical men and engineers were still agreed that water was
the main remedy.
Since that date preventive policy has been increasingly systematised
in the measures summarised in several of the papers before you ; measures
which have incorporated and extended the many important preventive
methods which had already been introduced.
They form to-day a large and complicated system. There are the
" medical methods " of strict examination of recruits, and of the detection and removal of the subjects of active tuberculosis; and there are
the " engineering methods ", such as provision for adequate ventilation,
and the regulation of shifts and blasting and also those methods which
depend upon the use of water to prevent the escape of dust into mine
air, or to lay it when actually in suspension. The success of this combination of measures has undoubtedly been great. One may claim, I think
with truth, that the number of cases of silicosis which are arising annually
to-day is only about one-third of the number which were arising fourteen or sixteen years ago. During tbe past three years there has been
a continuous drop in the production rates of the disease. Nor do I think
that the potentialities of our " present day " methods are by any means
exhausted. Within the last ten years, to take one feature only, the whole
practice of rockdrill work has been completely and favourably revolutionised, and such things take time to show their full effect. The improvement attained therefore has been substantial, and there is reasoned hope
for further improvement in the future. But, although we are satisfied
so far, we are also disappointed. We have scotched the snake, but we
have not killed it. We realise in particular that although water will
take one a large part of the way, it will not take one all the way, and that
its use has certain positive disadvantages both hygienic and economic.
Hence the minds of medical men and engineers are turning to-day to the
question: have we not been overdoing water ? Could we not do better
with less water, and a greater extension of alternative methods ? On
this point the experience of other countries will be welcome.
§ 2. — The second main subdivision of our programme is concerned
with the strictly medical aspect of silicosis.
In this section discussion will be opened by the papers on the " Aetiology of Silicosis " and on " Experimental Silicosis " by Dr. Mavrogordato.
The pathology, radiology and symptomatology of silicosis as met with
in South Africa are dealt with in three further papers. The first of these,
contributed by Drs. Strachan and Simson, is written from the strictly
pathological standpoint. The same writers have co-operated with
members of the Medical Bureau in the preparation of the two succeeding
papers on " The Clinical Pathology, Radiology and Symptomatology
of Silicosis ", in which that condition is considered particularly from the
standpoint of its practical diagnosis as an occupational disease. These
two papers present the conclusions drawn from a careful correlation
of the results of pathological, radiographic and clinical examination
in a consecutive series of 400 individual cases of silicosis occurring
amongst European miners, in each of which a post mortem examination
was performed, and in each of which a radiographic and clinical examination had been carried out within the six months preceding death. It is
upon this triple correlation that the standards of diagnosis and classification adopted by the Medical Bureau are based. It forms at once the
front line and the last ditch in our trench system of diagnosis.
It is common ground that it is the high potential predisposition to the

FIRST SITTING

ultimate development of an active tuberculosis that is the chief factor
in making silicosis the serious condition which it in most cases is. The
relation between silicosis and tuberculosis has been repeatedly discussed,
and will, one presumes, be once more thoroughly discussed at this
Conference.
The view taken in these papers is that a non-tuberculous nodular
fibrosis of the lung due to the arrest of silica dust vvithin that organ is a
definite and distinct pathological process, and is the predominant feature
of the great majority of cases of what is clinically termed " simple
silicosis " particularly in its earlier stages, and further that that process
may advance as such up to a point, but to a very considerable degree
without the intervention of tuberculous or other infection, even although
the affected man is removed from underground work.
On the other hand, not only are a number of cases of silicosis obviously
complicated from the outset by active tuberculous infection, but pathological observation leads one to the view that there exists in many and
probably in most cases of clinically " simple " silicosis, from the time
that it becomes definitely detectable, some latent circumscribed focus
or foci of low-grade tuberculous infection in association with certain
of the silicotic lesions.
Some such infective lesions may originate from persistent active
foci dating back originally to a primary infection during early life:
some may be due to a limited re-infection occurring during and associated
with the early development of the silicotic process.
This feature forms one factor in the explanation of the tendency
to the ultimate development of active tuberculosis which is manifest
in so many cases of silicosis. The future history of the case will depend
on whether such foci remain inactive, or become active and progressive
or whether again a further infection occurs from a source outside the
lungs. Other features in the situation however heighten that predisposition. The sites of the silicotic lesions offer possible points of arrest of
bacteria in the lymphatic system of the lung. And probably the most
important factor of all is the circumstance, as has been shown in particular by Gye and Kettle, that finely divided silica acts as a soluble cell
poison and has in consequence a specific effect in determining the
selection by a tuberculous infection of sites where silica is aggregated.
The local toxic action of silica may also go far to explain the characteristic modification of the silicotic process by chronic infections, and
particularly by a chronic tuberculous infection, with the production
of slowly progressive infective lesions of comparatively low virulence,
accompanied by an excessive fibroid reaction, which form so striking
a feature of many cases of the disease. To this characteristic modification
of silicosis the general term " infective silicosis " or in the more restricted
sense " tubérculo-silicosis " has been applied.
It would appear that the typical effect of silica dust when inhaled in
excessive quantities over long periods is, generally speaking, first to
cause a " dust bronchitis ", then to produce the simple nodular "dust
fibrosis " which is " silicosis ", and finally to lead on to a condition of
" infective silicosis " and a true " dust phthisis ". But there are in
individual cases many variations in the course of this development,
determined mainly by the relative preponderance of the dust factor or of
the infective factor, and by the earlier or later manifestation of the
latter.
At this point I would call your attention to the photographic Atlas
of the Pathology and Radiography of Silicosis which lies beside each
of you. It contains a reproduction of the original illustrations to the three

REPORT OF PROCEEDINGS

papers I have just mentioned and has been prepared for and is presented
to the medical members of this Conference through the courtesy and
generosity of Kodak, South Africa. It will form, we hope, a useful
addition to the literature of the Conference, and I am sure you will
desire that the cordial thanks of the members of the Conference should
be conveyed to the donors, Kodak, South Africa, for their handsome
gift-book. To Dr. Steuart and myself it is especially pleasing, because
the endeavour to secure satisfactory reproductions of radiographic
negatives of chest conditions has hitherto been a standing heart-break;
the reproductions achieved by the printer conveying for the most part
nothing of any value, either to their authors or to other people. This
is particularly unfortunate in the case of such a condition as silicosis,
in the diagnosis of which radiography forms so essential an element.
But the Atlas in your hands has, I think, made good this deficiency
in a very satisfactory manner, so far at least as the material which it
contains is concerned.
If I may be so bold as to offer the suggestion, I should wish to see this
Conference consider particularly three points in connection with the
pathology and diagnosis of silicosis.
First: Can we agree from the fundamental pathological standpoint
upon a definition of what constitutes silicosis regarded as a definite
condition of disease, the presence of which renders the affected
man capable of being certified as suffering from a specific and
identifiable occupational malady, which may constitute a valid
basis for a possible claim for compensation in that respect ?
Second : Can we agree upon a terminology which will render a description of the characteristic lesions and varieties and possibly the
" stages " of silicosis mutually intelligible to observers in different
countries ?
Third: Can we agree upon a terminology descriptive of the various
types of radiograph found in cases of silicosis, or other conditions
of pulmonary fibrosis, which may similarly be mutually intelligible to different observers ? The Medical Bureau has in this
regard tentatively put forward its own private conventional
terminology for the consideration of the Conference. Suggestions
for improvement will be welcome.
I think it would be a matter of real value if some agreement could be
reached on these three points which would facilitate mutual
understanding in the future.
§ 3. — The third subdivision of our programme deals with the incidence
and progression of silicosis, with the legal aspect of the disease, and with
the question of compensation.
There are included here several papers, mainly from the administrative
side, on the work of the Medical Bureau and the Medical Board of Appeal,
on the sanatorium treatment of silicosis and on the examination of native
mine labourers.
Finally the programme concludes with three papers which deal with
the development of miners' phthisis legislation in South Africa, with the
question of compensation and of other ameliorative measures undertaken
by the Miners' Phthisis Board, and with the great monetary burden, past,
present and prospective which the disease has placed upon the mining
industry. Yet great as this burden has been it represents only a portion
of the very serious economic loss which has been occasioned in South
Africa by this " scourge of the metal miner "

FIRST SITTING

Miners' phthisis, we are told in these papers, has been in this country
the subject of five Government Commissions, the earliest having been
appointed in 1902, of ten Parliamentary Select Committees, and of nine
Acts of Parliament, the first of which was enacted in 1911 and the last, or
what is for the present the last, in 1925. The subject has thus occupied
a great deal of the attention and time of the legislature during the past
nineteen years. In general each successive Act has been marked by an
increase in the amount of the awards payable to fresh cases, and by
additional provisions for surviving beneficiaries under previous Acts or for
the dependants of deceased miners, and one cannot say whether finality
in these respects has yet been reached. Legislation on the subject has
in this way grown to be extremely complicated. I fear that those who
approach the study of the present Act will find in it an extraordinary
maze of " sage provisos, sub-intents, and saving clauses " which only
those who know its history can hope to understand without a guide.
Such a legislative history in itself proclaims that the problem of
compensation has proved to be a difficult one. And the standing difficulty
as you will well understand is, that, viewing silicosis as an industrial
" injury ", the " injury " inflicted is in the majority of cases not a
stationary one, but one which tends to get worse, yet which does so very
erratically and in general over a period of a good many years. As I have
said elsewhere the important point about an early case of silicosis is not
what he is at the moment but what he may become. Mr. Spence Fraser
has computed the average expectation of life of an early case of the disease
when first notified, to be about fourteen years, with a wide variation above
and below that average. In the earlier stages of silicosis in which disability may be absent and is at all events not serious, the real crux of the question is not so much medical as economic—it is almost wholly that of
securing alternative employment by the men affected. In the later stage
it is one of definite and permanent invalidity. The question of serious
invalidity has been met since 1919 by the payment of a life pension to
those who suffer grave incapacitation from the disease ; the earlier stages
are dealt with by single lump sum awards. The practical problem is
complicated by the fact that in this country, in which most of the unskilled
labour is done by the native, alternative avenues of employment especially
for partially disabled men are probably less easy to find than in other
more fully industrialised communities with a homogenous population.
It may be suggested also that the term " miners' phthisis " itself has
unfortunately acted as a deterrent in the obtaining of employment by
beneficiaries and has also had, perhaps, in a good many instances, a
subtle psychological effect in this and other directions upon the beneficiary himself. It seems unfortunate therefore that this term appears
to have become entrenched in the titles of the local Acts although it is
nowhere mentioned in their substance. This is not, one would suggest,
an example to be followed.
One word in conclusion. The Medical Bureau by the sanction of the
Minister of Mines has recently installed a new three-phrase X-ray
generator from which we hope for much and of which we invite your
inspection.
May I also venture to call your attention to the plans of the proposed
new Medical Bureau which adorn these walls. The Bureau hao long
outgrown the swaddling clothes generously presented at its birth by the
South African Institute for Medical Research and has indeed long been
hampered and even endangered by insufficient accommodation. These
plans are a vision of a larger future. They are an earnest of how seriously
the present Government of the Union regards the matter of silicosis in

REPORT OF PROCEEDINGS

South Africa and of the high standard of efficiency for which it is prepared
to provide the means and of which it expects to obtain the realisation in
the detection and investigation of the disease.
May I be permitted to offer a final suggestion, namely, that this
Conference should not terminate without making arrangements for
future international intercommunication upon this very important
matter of silicosis and allied dust diseases by the establishment and
maintenance for example of central libraries of the literature of the
subject under the relevant Government department of each country,
and possibly by formulating a provisional programme of future desirable
lines of research, and by endeavouring to secure a greater international
co-operation in carrying out such a programme than at present exists.
The experience of different countries and different industries differs in
important respects, and some systematic means of collating and
comparing that experience might be found.
And now, Gentlemen, I have done. I must thank you for hearing me
so patiently. I have attempted merely to offer you a very general
perspective of the silicosis question in South Africa. I am well aware
that this is but one of many aspects of the general problem which will
occupy our discussions, and that it has many other aspects. But it is
best to speak of what one knows.
VISITING MEMBERS' EXHIBITS

After some discussion it was agreed that the exhibits brought by
visiting members should be shown at 8.15 p.m. on Friday, 15 August.
(The Conference adjourned at 5.55 p.m.)

SECOND

SITTING

Friday, 15 August 1930, 2.30 p.m.
Chairman: DR. L. G. IRVINE

The Chairman proposed that the members of the Miners' Phthisis
Medical Bureau and the medical staff of the South African Institute for
Medical Research should be permitted to attend the sittings of the
Conference.
The Conference unanimously adopted this proposal.
OCCUPATIONAL CONDITIONS AND METHODS OF DUST PREVENTION

Dr. Middleton : The scheme prepared by him and circulated to members
of the Conference did not attempt to cover silicosis throughout the world,
but only as it occurred in Great Britain. By " œtiology " in the title
of his first heading he intended to cover all the factors in the causation
of the disease silicosis.
The first factor was exposure to silica dust, by which he meant dioxide
of silicon in a free state, and not chemically combined in the form of
silicate. British legislation was based on the view that disease was

SECOND SITTING

caused by silica dust, and a precise definition of what was silica dust was
therefore necessary. During his own investigations into silica processes
he had never been able to determine the standard of air dustiness which
produced silicosis. He was aware that in South Africa and in Sydney,
Australia, a figure was laid down in connection with preventive measures.
Tt was however impossible to discuss a figure until all the facts were
known. He suggested that the Conference might usefully lay down a
basis for the comparison of results.
In England the apparent exposure to silica dust necessary to produce
silicosis had been short; there was a case of fatal result from tuberculosis
with evidence that it had been produced by silicosis after two and a half
years' exposure.
A third factor which must be taken into account was the extent of
exposure period plus latent period, and the relation of these to each other.
The influence of intermittency of exposure by alternation of occupations had preventive bearing. When dust was reduced by certain
hygienic conditions silica was still present, but intermittent employment might save the worker from pulmonary disease or at least from
disablement. This had already been attempted in some factories in
Great Britain.
Another important aspect was the influence of the presence of other
dusts on the occurrence and course of silicosis. Some dusts were
referred to as restraining silicosis; this was said to be due to colloidal or
to chemical action. Other dusts had a physical action in preventing
inhalation by aggregation. Some rocks containing clay, for instance,
produced large aggregations of .particles too large to be carried to the
alveoli.
As regards dusts other than silica which might produce evidence of
lung change similar to silicosis, he pointed out that a worker might
worsen his condition by passing from one industry to another. Asbestos
damaged more rapidly than silica. Sandstone grinding was very
largely replaced by the new forms of grinding, such as by emery; there
was not yet sufficient evidence to indicate the effects on the health of the
workers of these processes.
Different industries produced different types of pulmonary disease.
Workers in the refractories industries and potters died alike of silicosis,
but the type of silicosis was different. Living conditions might have
some influence, but in highly skilled trades, such as that of stone masons,
where the standard of living was good, the mortality was high.
Finally, as regards the occurrence of infective processes, he asked the
Conference to express an opinion on the statement that silicosis was not
developed in a healthy lung, but must be preceded by inflammation.
Dr. Russell : In the United States the proportion of silica dust in various
industries varied from 1 up to 90 per cent. The medium between the
two was probably the average type of dust. Granite dust in the United
States contained less silica dust and a higher percentage of other
chemicals, to which its inhibitory action had been attributed. The
development of silicosis in the granite industry varied in direct proportion to the extent of exposure (30-35 per cent.).
Dr. Moore: The period of exposure necessary to contract silicosis
depended primarily on the individual. In the Bendigo mines the silica
content was over 90 per cent. On the West Coast of Tasmania it was
about 60 per cent, and in Kalgoorlie a little more. The Bendigo statistics
were not very trustworthy, since the miners were loth to be examined,
but about ten years seemed to be the average period to produce silicosis.

REPORT OF PROCEEDINGS

In Kalgoorlie it was nearer sixteen years. Silicosis seemed to depend
pretty accurately on the silica average in the country rock.
Dr. Böhme : German experience showed that sand blasters and grinders
had well-developed silicosis sometimes after three years. Generally
silicosis deve'oped after nearly ten years. Comparable statistics were
required in order to distinguish between various dusts. He did not
believe that coal dust had any inhibitory effect. There were cases of
workers employed on hard rock for three years and then working ten
years as colliers who were still developing silicosis and were no more
protected than those who had never worked as colliers.
Dr. Koelsch: In his short report just distributed, the question under
discussion had been already emphasised, as well as the decisive
influence of free silicic acid, and attenuation of the effect of silicic acid
by combination with other substances, etc. As regarded the period of
time required to develop the disease, he had seen two cases of severe
silicosis after two-and-a-half years of employment on sand-blasting;
the workers in question were aged twenty-five and thirty years
respectively. Timely suspension of work might in the earlier states bring
about retrogression of the silicotic changes. Yet in this instance, as
likewise in the development of silicosis, the individual constitution and
the resistance capacity of the tissues is of capital importance.
Dr. Fisher: Three factors were to be considered: (1) concentration of
dust; (2) time: (3) percentage of fne silica. It was desirable to use
the same konimeter throughout, preferably that which gave the most
de'icate results. In Great Britain there was up to 60 per cent, free
silica in mines. He would like to know whether this was a safe figure.
He also asked the Conference to express an opinion as to the best
konimeter. Two preventive measures were water and dust traps. He
would like to see an efficient mask invented; a mask which did not
obstruct respirati n would keep back half the dust, and this might
be sufficient if 300 particles per cubic centimetre was a safe count.
Dr. Badham : The air of parts of the Rand mines which he had seen
did not contain 4 milligrams of dust per cubic metre since dust was not
visible under that figure. At about 400 particles per cubic centimetre
(using Owen's konimeter) dust particles below 10 microns with a
size frequency ratio of 3 did not form a visible cloud.
The size frequency ratio of particles was important, for by its study
it could be seen that in a dust such as that referred to, though the 1 micron
particles were very numerous, the 2 micron particles contributed the
greatest percentage of surface; for this reason he did not subscribe to the
belief that ultra-microscopic particles were culpable in producing
silicosis. He thought that further work should be done in dust counting
to ascertain definitely the amount of silica which could produce silicosis.
It appeared that the average exposure on the Rand was |about 1 milligram per cubic metre, and if this was so then the prospects of their
attack on the disease by reducing the amount of dust inhaled seemed
rather hopeless.
He hoped that further attempts would be made in South Africa to
correlate the konimeter counts with the sugar-tube results. He thought
that Owen's konimeter was capable of doing all the work now being done
on the Rand with another instrument and stated that it produced a
record from which carbon particles and water-soluble salts could be
eliminated by selective counting.
He thought that more attention should be given to the particulate

SECOND SITTING

count and urged South Africans to try more recent methods of dust
estimation.
Dr. Kranenburg: It was necessary to know how much silica was
contained in different kinds of stone. In marble, for instance, silica
was always present. Italian marble had 6.7 per cent, free silica and
Belgian marble 1.2 per cent. The figures for samples of limestone were:
Belgian, 1.1 per cent., 1.5 per cent., 0.1 per cent., 0.5 per cent. ; French,
0.6 per cent., 0.4 per cent., 0.6 per cent.; German, 0.2 per cent.
Dr. Pirow (in reply to Dr. Fisher): The konimeter standard must
depend on the percentage of free silica present. He had found with the
Rand percentages that 300 particles per cubic centimetre could be taken
as a standard, but he was not convinced that it was safe. Water and
ventilation were the only preventives in South Africa. Dust traps had
been tried, but the general opinion was that they were much too
dependent on the personal element and could be applied only in isolated
cases. Up to the present no fool-proof and practical masks had been
produced. He did not agree with Dr. Badham on the relation between
microns and the count of particles per cubic centimetre; 400 or 500
particles per cubic centimetre could be found; it depended on the
fineness of the dust. Hand-drilling produced much coarser dust than
machine drilling. It was usual to state the percentage of coarse particles (those above 5 and 10 microns). Owen's konimeter was used by
the Mines Department as a check, but required too much care to be
practical for routine work.
He regarded the South African results
as only comparative. Efforts to correlate konimeter and sugar-tube
results had not been very successful. The concentration entirely
depended on the percentage of free silica in the dust. The present
concentration was known to be dangerous and attention was being given
to the highest concentrations. Attempts were being made to standardise konimeter practice.
Dr. Cunningham: In Ontario gold mines the exposure necessary to
produce ante-primary silicosis was nine to ten years. The percentage
of free silica was about thirty to thirty-five. This period seemed short
compared with South African experience. It was perhaps impossible
to correlate the various dust-counting instruments used in different
countries.
Sir Spencer Lister: There was some confusion in the term "silica
content ", which might refer to rock or to dust. Only the silica content
and amount of the atmospheric dust matte ed and the size of the particles. If very small particles were produced the weight standard was
of small significance since the large particles were innocuous.
Dr. Mavrogordato : He hoped the Conference would initiate an
epidemiology of silicosis. They needed to know where it occurred, what
was its comparative incidence, and what were the comparative conditions. Free silica in country rock was a very important factor, but
they must know the percentage of free silica in the air, and also what
other dusts were present. Of these dusts, which increased liability
to silicosis ? In Great Britain there were two kinds of firebrick with
the same silica content, but the incidence of the disease was very
different.
It was easy to remove all visible dust, leaving all the dangerous
dust, so that size frequency was of great importance. A method which was
effective for coarse particles might be useless for fine dust. Water
would keep down dust, but how was dust to be removed when it was

REPORT OF PROCEEDINGS

once in the air ? In rapid cases of the disease what part was played by
the size of the particles ?
Masks were most likely to be successful with a system of positive
pressure, but he did not believe that other types of masks at present
available could stop the dust without stopping the air when the svearer
was at work.
South Africans used a dark ground konimeter count and believed
that the results were as good as with oil immersion and a light ground.
He agreed that 500 particles per cubic centimetre with a dark ground
amounted to 1 milligram. When the count was down to 300 it meant
a dark ground count in South Africa.
Dr. Kranenburg asked whether it was possible to free air of invisible
dust by precipitation (flocculation).
Mr. Boyd: South African dust counts were regarded as empirical.
The sugar-tube method had been retained for purposes of historical
comparison. Finality had not been reached with the konimeter.
It had needed much experiment to reach the present method of counting,
which had now been in use for two years. A Committee was at present
sitting to investigate methods and to devise a standard. Owen's
konimeter was too delicate for routine work. In size classification the
largest particles were found in the ore-bins, next in hand-drilling, and
then in machine-drilling, which produced the finest dust except blasting.
Dr. Middleton: Working conditions in factories sometimes made
the use of water or exhaust draught impossible and masks were therefore required. No standard mask existed, and those on the market were
not of known value. The Home Office was investigating the possibility
of a mask to protect against fine silica dust, while at the same time providing for an air pressure which would allow a man to wear it some
time without fatigue.
He thought that the Conference should adopt a resolution of a progressive kind on the subject of correlating the results of dust counting.
The percentage of free silica seemed to be in relation to the silicosis
induced in the lungs, but this was an unproved assumption. He hoped
that the Conference would draw up a scheme for the exchange of views
and knowledge. The dust counts which he had reproduced in his paper
led nowhere. He had always used Owen's konimeter and found it
useful, but it was impossible to reach a standard for a safe dust figure.
In South Africa conditions from mine to mine were fairly comparable,
and it was therefore easier to arrive at a figure, though he was aware
of the difficulties, partly due to the change in instruments and underground conditions. He did not personally favour dark ground illumination, because it did not eliminate carbon particles, which were very
numerous in most dust samples in Great Britain. Silica dust tended
to remain discrete, but it was impossible to say how far the same
mixture of dust occurred in the atmosphere as in the smear. Where
moisture was used to lay dust the number of particles below two microns
in a droplet might be over 800. He urged that a uniform method
should be adopted so as to render results comparable.
Professor Hall proposed that a sub-committee should be appointed
to consider the possibility of standardising dust counts.
Mr. Roberts: A sub-committee would not have sufficient time to
reach a satisfactory conclusion. A Joint Committee of the Mines Department and the Chamber of Mines had been working at the question for
more than a year.

SECOND SITTING

The sugar tube had given good results, but it showed weight and
not numbers. An attempt was now being made to reduce numbers
with the help of Owen's and other konimeters. Mining engineers would
endeavour to carry out whatever the silicosis experts recommended.
It was possible that ventilation ought to be increased and humidity
decreased, even at the risk of more dust.
Dr. Loriga: He had nothing to add as cases of silicosis are rare in
Italy, and such as have occurred have not been recorded in detail.
He had therefore no communication to make in regard to the disease,
but would like to ask the members of the Conference, in view of the
fact that up till now exclusive mention has been made of silicosis:
were there not other dusts which produced forms of pneumoconiosis
other than silicosis ?
Reference has been made to the outbreak of the disease after a lapse
of ten, fifteen, and twenty years. How was it possible to measure such
periods with any accuracy ? Silicosis did not resemble an acute disease
occurring at a given moment, but it was a disease with slow progressive
evolution. What stage in the disease was considered to constitute its
commencement ? He believed it was when the lungs could no longer
eliminate the dust so that the disease either increased, was arrested,
or led on to death, but he would like to know what criterion was used
in stating that a worker was now no longer healthy but must be|regarded
as silicotic.
Firstly, what dusts favoured or retarded the action of silica ? And
what dusts could reach the lungs and get fixed there ? Neither the
Sub-Committee nor the Conference could solve these problems. It
would never be possible to say precisely what quantity of dust would
provoke silicosis since it was not absolute quantity or quality that
mattered but the relative quantity. One individual might resist a
proportion of 100 particles per cubic centimetre, while another would
react unfavourably to 50 particles per cubic centimetre; there was
further the whole question of the rate of inhalation. A medical inspector
who was inactive would inhale much less than a worker engaged in
heavy physical labour. Accelerated respiration would in the latter
case cause inhalation of particles which the former could not inhale.
The special pathological aspect seemed, therefore, incapable of solution,
but the general pathological side of the problem was already solved.
In each case it was necessary to direct attention to the size of the
particles, the rate of inhalation and possible penetration and fixation
—that was in each given case, but a general estimation of these to
meet all cases was impossible.
The Sub-Committee was therefore obliged to confine its attention
to the hygienic and practical issue, that was: (1) to determine the
standard amount of dust tolerable in the air of a mine for an individual
of average health; (2) to determine means of assuring reduction of dust
to this amount by analysing the air and to determine the best methods
of estimating the dust present in the atmosphere.
In regard to (1) the standard would depend on such factors as
quality and admixture with other dusts.
In dealing with the hygienic aspect secondary questions must be
left out of account. The problem was that of reaching agreement as to
a standard limit for all countries to be determined by future research.
Dr. Orenstein: Two different questions were answered by the dust
count: (1) in a given industry it determined how conditions varied
(where conditions, as on the Rand, were always comparable); and (2)

REPORT OF PROCEEDINGS

for critical scientific study an international standard could be laid
down.
About 100,000 samples were taken annually on the Rand, so that
a laborious procedure was impossible.
He added that " dark ground illumination " was not the true dark
ground of the microscopist.
He suggested that the reporters might co-opt one or two experts
to consider a recommendation for an international standard in dust
counts for scientific research, and the Resolutions Committee should
recommend the experts in question to the reporters.
The Conference unanimously adopted this proposal.
(The Conference adjourned at 5.10 p.m.)

THIRD

SITTING

Saturday, 16 August 1930, 9.45 a.m.
Chairman:

DR. L. G. IRVINE

PREVENTIVE MEASURES AND UNDERGROUND CONDITIONS

The Chairman suggested that the discussion should be broken into
specific subjects.
I. The Relative Value of the Use of Water and of Ventilation
in the Prevention of Silicosis.
Dr Mavrogordato: Water had three uses: (1) To keep dust out of
the air at the site where the stone was broken; water was very efficient,
but the finest dust would pass any form of water. (2) To give a "flypaper " effect ; this had been found less effective ; tests made on the Rand
in 1912 and 1913 proved that other preparations—e.g. Mr. Ussher's
treacle—were no better than water; it was doubtful how much had
been gained by keeping the place continually wet, since the air was
thus very greatly humidified; when a development end had dried for
two days it maintained 80 per cent, relative humidity, but when washed
it went up to 100 per cent, almost immediately; it would therefore
be desirable to revert to the " fly-paper " effect with some other preparation than water. (3) To remove dust from the air. Lord Lister had
said at Berlin in the early eighties that he was ashamed of ever having
suggested that spray could affect objects of the size of micro-organisms
in the air. The Commission on the ventilation of the House of Commons
•came to the conclusion that fine particles could be blown through any
"water-screen. With a high temperature high relative humidity was
a great inconvenience; organisms kept alive more easily in a wet
atmosphere and this was very disadvantageous as regards infective
silicosis. Even though the dust was not highly concentrated in the air,
•silicosis was still produced in a virulent form. The infective element,
therefore, played a considerable part.

THIRD SITTING

The effect of dust did not end with inhalation. He had produced a
microscopic fibrosis in seven months with fine silica dust (flint).
Progress continued over nine years, however, must be due to some
element superimposed on the dust. The droplet of 800 particles to
which Dr. Middleton had referred was bombarding the lung with
shrapnel instead of rifle fire. It was difficult to infect an animal by
blowing dry organisms, but 90 per cent, positive results were obtained
from spraying. Water facilitated the entry into the lungs of particles in
the air and it was therefore preferable to deal with dust by ventilation.
He doubted whether an effective ventilation system was possible.
Silicosis was made in twelve years on the Rand, and in about ten
years in Canada and Australia. But in English potteries and grinding
a twenty-five year exposure was found. Dry methods of control
therefore made silicosis much more slowly. In English collieries there were
probably many abnormal lungs, but they had been at work twenty-five
years or more. Wet surfaces should be kept down as much as possible
and there should be all possible ventilation. Mines with a concentration
of dust like the Rand would be much more healthy if this concentration
were secured by dry methods. It was however impossible to avoid the
use of water on the Rand and therefore the surface must be kept down
by avoiding leaks in drills and diminishing all spraying; water would
keep dust out of the air without great surface.
Dr. Middleton: In factories water and localised exhaust draught
were the two main methods of dust prevention. Water should be used
for the suppression of dust at its point of origin, and in some processes
could be effectively used upon this principle. If sufficient water was
used dust never arose, but ample water supply was essential. If no
water could be used at the actual moment of fracture of rock steam
had been found efficient, but it must be in a saturated condition. If steam
was allowed to fall on a dust cloud at its point of formation, the dust
would form aggregates and fall. Argillaceous matter in the dust
facilitated the formation of aggregates.
The problem of high temperatures did not arise in factories, so that
humidity and dissociation did not occur. Grinding with sandstone
wheels of 2 to 7 feet diameter gave working faces of 2 o r 3 t * 18 inches.
The idea at one time prevailed that dust was not produced at wet
grinding but that if sparks escaped into the atmosphere dust would
also. In Great Britain the revolving stone often dipped into a water
trough, but Owen's konimeter had proved that the metal cut through
the wet surface and gave rise to fine dust from the stone.
Dry grinding had once been the most dangerous industry, Calvert
Holland, of Sheffield, had shown that no dry grinders in the
middle of last century reached forty-five years of age. It was still
carried on, but with an exhaust draught and the incidence of silicosis
was now much less than among' wet grinders. There was thus a strong
argument for the use of exhaust draught.
British regulations required the suppression of dust as near as possible
to its point of origin, either by water or by localised exhaust draught.
The dust figure was sometimes very little reduced by exhaust draught
—perhaps by 25 per cent. The failure of the localised exhaust draught
was due to the idea that it had some selective effect. This was not
the case. The system ought to be such as to remove a sufficient volume
of air from the point of origin of the dust and to ensure a directional
current. The addition of baffles at the sides of the workplace would
enormously reduce the amount of air to be removed. It was a special
3

REPORT OF PROCEEDINGS

engineering problem to correlate the size and speed of the fan, the
capacity of the duct, and the volume of air to be moved.
Processes were sometimes improperly carried on between the point
of origin of the dust and the exhaust system. General ventilation
should never be combined with a localised exhaust draught system
unless the two could correlated by some means. The pull of the fans
caused directional currents towards them and the two systems together
always produced eddies. Dust commonly escaped from the hood and
passed directly upwards and was then diffused generally throughout the
room, so that high concentrations could be counted.
It was hard to determine the relative value of water and exhaust
draught; there was a place for each. Water was efficient where it
could be easily and sufficiently used, generally outside the workroom;
otherwise exhaust draught was necessary. It was impossible to lay
down figures for efficient local exhaust draught; a linear velocity
of 200 feet at the throat of the duct was usually enough to remove
80 per cent, of the dust. Where the source of dust was a rapidly revolving object, as in towing earthenware, there was much more difficulty
in collecting all the dust. Water could not be used in the vast majority
of factory processes.
He had been much impressed by the humidity in the Crown Mines.
If even with the use of water minute particles of dust could still be
determined in the atmosphere this was a definite argument against
the use of water in confined spaces.
Dr. Badham: In textile mills one sees the use of various methods
of securing humidity and among the methods used the value of
conveying the air along wet tunnels has been recognised and applied,
in fact he thought it is even more efficient than water atomizers. One
can appreciate therefore the Rand humidity problem.
He agreed with Dr. Mavrogordato that water is of value at the sites
of percussion or fracture—drilling, blasting, and breaking ore. He had
no data bearing on the important question of whether the use of water
increases infectious conditions.
He found some years ago that the use of the water blast did not
reduce the number of particles of dust of micronic size in the air and
Drinker of the U.S.A. has also shown this.
He was looking forward to getting useful data as to the parts played
by infection and by dust in the production of silicosis. He had a group
of sandstone masons who work in open air conditions, and are exposed
to 4 milligrams per cubic metre or 400 particles per cubic centimetre
of sandstone dust. From a recent investigation the incidence of silicosis
among these stone masons did not differ much from that found in
quarry men and sandstone miners. He was hopeful that future dissection
of these figures may show how far the factor of infection comes into
play underground in humid conditions. He came into daily touch
with the problems described by Dr. Middleton and could appreciate
his remarks. At the present time spray painting and the use of silica
dust in paints used in spraying was providing them with a new industrial
hazard.
Dr. Moore : The lead-smelting works at Port Pirrie received concentrates (slimes) from Broken Hill. They were shovelled from trucks into
dumps in the open air. Hoses had been used to lay the dust, but the
main result was to raise clouds of dust, and eventually the dumps
were plastered with whitewash.
Dr. Böhme: The German Mines Safety Office has recently offered

THIRD SITTING

a prize for protective measures against injury by stone dust, anu many
suggestions have been received and examined.
The formation of dry dust in drill holes can be diminished by the wellknown methods of wet-drilling, but these methods cannot always be
used.
Many methods of precipitating the dust which is diffused from the
drill-holes in dry drilling have been proposed. Sprinkling with water
has no effect in the case of the dangerous fine dust. On the other
hand, previous trials have shown the value of a new method; dust
from the drill-holes is caught at the mouth of the hole by newly formed
soapsuds. Absorption of dust at the mouth of the drill-hole has also
proved successful. In using this method it has been found valuable
to draw off the particles of stone separately from the dust.
Amongst the masks which were sent in for examination, one model
is especially worth mentioning. In this model the filtering surface
is much enlarged by using the form of a sack, and at the same time the
resistance to inhalation is greatly reduced.
Good ventilation at the place where drilling is going on is also of
great importance.
The Mines Safety Office is continuing its investigations.
Dr. Cunningham: Granite cutters, moulders and grinders usually
took twenty-five to thirty years to develop silicosis. These were dry
operations, while under wet conditions miners develop the disease in
between ten and twelve years. In some of these operations the dust
exposure is roughly comparable.
Dr. Kranenburg : In 1912 Dutch stone masons wetted the working
place where possible. He personally preferred exhaust draught.
The Chairman: No reference had yet been made to the very fine
dust caused by blasting, for which water was ineffective, and ventilation
was therefore the important alternative. The single shift system and the
limitation of blasting to once in the twenty-four hours gave in conjunction with ventilation an important measure of protection against
the risk of inhalation of dust from blasting.
The Miners' Phthisis Prevention Committee in 1916 had shown
that 97 or 98 per cent, by weight of the dust could be removed after
blasting or in drilling, by means of water, but their standard of dangerous
dust was 12 microns, which was now known to be too large. A Joint
Committee on Ventilation and Dust definitely reported in 1922 that
the water blasts in use were ineffective in laying the fine dust produced
by blasting. He did not believe, however, that the possibilities of present
methods had been exhausted. The exclusive use of drills with axial
water feed had not been made obligatory until 1926, but he agreed
with Dr. Mavrogordato as regarded the disadvantages of water.
Mr. Roberts: While the water blast did not necessarily catch fine
dust at the time of blasting, it did wét the ground while in process of
being broken and thus tended to prevent the formation of dust when
the broken ground was subsequently handled, e.g. shovelled into
trucks; it also dissolved the noxious gases formed by the blast. Its
present use was confined to development ends, and ventilation was
arranged so as to replace after blasting all the air between the development face and the next through-ventilation connection.
Dr. Kcelsch: He desired to draw attention to a question of fundamental importance. Research undertaken by Teleky (Düsseldorf)
in Solingen—the German Sheffield—has revealed the fact that cases

REPORT OF PROCEEDINGS

of silicosis occur amongst wet grinders there with considerably greater
incidence and of a more severe type than those affecting dry griuders.
He thought he was in a position to confirm these observations from
his own experience. The causes are to be sought, in fact, in the varying
biological reaction of the system to wet dust imprisoned in the finest
droplets of water, or to dry dust as the case may be; in the varying
reaction, in other words, of the tissues in a damp or dry atmosphere.
Dr. Russell: There was a high incidence of silicosis and tuberculosis
in grinding in Connecticut. The abandonment of wet grinding and
substitution of dry grinding with an exhaust system had reduced the
incidence materially, and much reduced the dust count.
Dr. Loriga: In regard to the use of water in mines he believed it
was impossible to pronounce either a favourable or unfavourable verdict.
It was essential to study carefully the conditions under which water
is applied. In the various operations, which they saw yesterday and
which were practically similar in all mines, the first in which the dust
problem arises was that of drilling, when done by hand or by machinery
utilising the dry method, in which case the amount of dust produced
was great. With the use of waterfed drills the quantity of dust produced
was reduced to a minimum. He believed there was no atomisation
of water or projection of water droplets with dust in suspension, because
the drill worked within a tube the wall of which prevented the atomisation
of the water and the water left the tube in a liquid state ; he considered
the use of water not only necessary but indispensable.
The second phase of the work in which much dust was produced
was blasting. Here the worker had to be protected not against dust
alone, but especially against injurious gases. The workers were always
removed to a distance, but the air currents from the blasting might arrive
in other parts of the mine. What could be done to prevent this air
laden with dust and injurious gases from reaching the parts of the
mine in which workers are situated ? Dry ventilation would not suffice.
Ventilation alone was therefore inadequate except when the plan of
the mine permitted of the air current being led off in another direction.
A water curtain at the end of the blasting area was useful to condense
the gases and allay the dust, as Mr. Roberts had said, and would
prevent poisoning as well as diffusion of dust.
The third very dusty operation was the handling and transport of
rock debris and dusty material from the blasting, etc. It was necessary
to discuss the utility of projecting water on to the material and walls
of the mine and into the atmosphere. He was here in agreement with
several of the previous speakers as to the danger of undue humidification of the air. It encountered various obstacles. It was likely to
render the temperature conditions more harmful. Humid air, as was
well known, was less tolerable than dry air at equal temperature, and
humid heat was more likely to cause heat stroke than dry heat. Water
spraying would prevent the dust from settling, it was true, but constant
humidification of the ground favoured the evolution of certain disease
germs, such as those of ankylostomiasis. While therefore is was advisable to use water for dust removal, recourse must also be had to
ventilation and' to those means of handling and transporting material
least likely to raise dust.
In conclusion, it was impossible to express a decided opinion for
or against the use of water. At certain moments it was extremely
necessary—i.e. in drilling and in the elimination of noxious gases after
blasting—but in addition it was essential to have air in large quantities

THIRD SITTING

to provide at the same time for air renewal and removal of the dust
and gas laden air.
The Chairman: The reporters might summarise the feeling of the
Conference on this point and draw up suggestions for further research.
Dr. Orenstein: Data were of more value than opinions. What
data were available on the reduction of small particles at the point of
contact ? Many localised exhaust draughts were applied in a very
amateurish way. The speed of the rotating body and its situation
in relation to the hood was important, because the rotating body acts in
certain ways as a fan. The dust reduction was much smaller than it should
be. He asked whether Dr. Russell could put on record the experience
of his Department with two neighbouring sets of mines in Missouri.
In one set of mines the lay-out made ventilation poor; in the other it
was relatively good. Both worked quite dry, but in the better ventilated
mines the incidence of silicosis was very low.
He was much impressed by the reduction of visible dust by water,
but he doubted whether water did not do more harm than good.
It was noteworthy that silicosis had become much more virulent
and that, except on the Rand, it was contracted only after many years.
Was water or something else responsible for the situation on the Rand ?
He was much interested by Professor Kettle's investigations into
the solubility of silica. Only the nebula was dangerous and water
could not wash those particles out of the air or make them settle on
the walls. A film which had been made of drilling without water
recorded an enormous amount of dust which was invisible to the naked
eye.
Dr. Middleton : The Medical Research Council had set up a Committee
to investigate pulmonary disease due to dust in industry. The speed.
of the sandstone wheel and the direction of the air current were very
important factors. Wet grindstones in England turned in the direction
opposite to their direction for dry grinding in Germany, while in
Germany more stones were sometimes found in one room than in
Great Britain. In dry grinding very rapid revolution of the grinding
wheel needed much more closely localised exhaust draught.
Dr. Russell (in reply to Dr. Orenstein): The Missouri mines were
worked out. Similar investigation, however, was proceeding in Oklahoma.
Dr. Kranenburg: There was a danger of heat stroke from radiant
heat in tunnels in the Netherlands where there were temperatures of
90° and 124° F. If the men protected their heads there was no danger
to health from dry heat.
II. Possible Rôle in the Prevention of Silicosis of an Admixture
of Adulterant Innocuous Dusts with Silica Dusts
Dr. Mavrogordato: Adulterant dust might help the aggregation of
fine particles in the air or might facilitate the exit of dust after inhalation.
Phthisis dusts were those which overcame the lung's ability to get rid
of them. Coal, limestone and other dusts retarded the accumulation
of phthisis dust in the lungs, while other dusts, such as abrasive powders,
encouraged silicosis. Metallic mineral dust would modify the behaviour
of any free silica which was present in the air at the same time. It must
therefore be decided whether artificial dust was to be used to cause
aggregation or to assist expulsion from the lungs.

REPORT OF PROCEEDINGS

Dr. Kranenburg: A dust of voluminous particles, light in weight,
should be introduced as high up as possible in the air, over some distance
in the development end, subsequent to blasting. This dust must be such
that it remains suspended in the atmosphere long enough to enable it
to bring down any fine silica dust which may be in the air. What the
nature of this dust should be was another question.
Dr. Böhme: Miners who have worked for several years as rock
drillers and who later change over to hewing, contract silicosis in the
same way as miners who continue to work as rock-drillers. It is not
therefore possible to prove that the inhalation of coal dust has a
favourable influence on the development of silicosis.
Dr. Mavrògor'dato : Any dust which assisted expulsion from the
lung must be inhaled at the same time as the silica. In his experience
the filling of the lungs with other dusts, whether before or after exposure
to silica dust, did not favourably influence the accumulation of silica.
Professor Hall: This was a suitable subject for research. It seemed
an extraordinary procedure deliberately to put a second foreign body
in the lungs. He asked whether the effect of metallic mineral dust
was favourable or not.
Dr. Middleton: Aggregation outside the body was very important
and deserved investigation.
Dr. Gardner asked whether the accelerating effect of abrasive powders
was chemical or not.
Dr. Fisher: Goal was dusted with shale which often contained
60 per cent, free silica. This was inhaled simultaneously with coal
dust, but colliers nevertheless got solidified lungs. He always advised
coal owners not to use dust containing free silica.
Dr. Badham: Autopsies and pathological study must clear up the
causation of fibrosis.
Professor Kettle: It had been suggested that acute silicosis was due
to alkali mixed with silica which aided the solubility of the silica. He
did not understand how this could happen without acute damage to
the lung tissue. The only case of acute silicosis alleged to be without
tuberculosis which he had been able to examine proved to be definitely
tuberculous. Judgment must be suspended upon the fixing action
of alkali allied with silica dust.
Mr. Roberts: No precautions were taken against dust in the Mysore
goldfields, but a man who had been employed there was found to be
free from silicosis.
Dr. Orenstein: Professor Haldane's guarded proposal concerning
the admixture of dust was intended not necessarily to prevent silicosis,
but to prolong the period of useful work and render the disease less
disabling. It was claimed that there was no disabling silicosis in
Mysore or in Cripple Creek, U.S.A., although dust samples showed a
considerable content of free silica in the vein and in the country rock.
The U.S. Public Health Service reported, however, that there was
considerable silicosis at Cripple Creek, and he was not convinced that
the situation was not similar in Mysore.
Dr. Kodsch: Observations made in regard to workers on shell
limestone, who had between times also worked on sandstone, revealed
the fact that marked silicosis occurred, that is to say that the effect of
the silica was predominant. It was not possible to establish a clearly

THIRD SITTING

marked retarding effect due to the limestone dust. In any case the
question of the prophylactic application of relatively harmless dust
during work in an atmosphere laden with silica dust is one which
must be approached with the utmost caution.
Dr. Gardner: Guinea-pigs dusted with marble dust showed no
damage; quartz dust given later gave the same results as when no
marble dust had been given,
Dr. Kranenburg: In the Netherlands the simultaneous inhalation of
sand tone and limestone gave apparent protection.
Dr. Middleton: There was no evidence of silicosis from limestone
alone.
Dr. George: At Broken Hill the ore is of extremely complex composition. It contains only 14 per cent, of free silica on an average, the other
constituents being chiefly manganese silicate, lead sulphide and zinc
sulphide. The country rock contains no free silica. In spite of this
we find silicosis, and this, as you have seen, shows exactly the same
radiographic picture as your silicosis on the Rand.
TABLE OF MINERALOGICAL COMPOSITION OF MINE ORES
(PERCENTAGES)

North

Silica free
Silicates
Galena
Blende
Sulphides
of copper
Sulphides
of arsenic
and antimony
Calcium
carbonate
Calcium
fluoride
P y r i t e or
marcasite
Pyrrhotite

Junction
North

1.62
15.16
39.57 66.41
17.69 14.34
22.03 14.05
0.22
0.09
5.24

0.25
0.07
3.02
0.20

British

Block
Block
14 B . H . P .
10

Central

South

Zinc

15.20
48.77
13.69
19.64

11.74 12.00
47.43 46.28
16.88 14.64
21.48 23.74

7.01
57.25
12.76
20.07

12.24
37.81
16.87
29.20

17.73
24.37
18.38
26.95

17.40
33.28
18.21
19.92

0.22

0.19

0.22

0.21

0.27

0.07

0.09

r 0.06
\ 0.04

0.12

2.73

2.60

3.79

11.15

10.80

0.22

0.39

0.30

0.32
0.40

0.10

0.22

1.70
0.19
2.57

0.04

0.21
0.28

0.15
0.20

100.00 100.00 100.00 100.32 100.00 100.00 100.65 100.00 100.00

An examination of the figures in the above table gives the following
information. The figures in the table are arranged in the order of the
mines from north to south.
The percentage of free silica in the average ore samples varies from
1.62 to 17.73. The ore is thus nowhere rich in silica, and in one mine
the percentage is very low indeed.
The samples of country rock were obtained partly from the walls
of stopes and partly from development drives. A number of samples
were taken in each mine, the places sampled being chosen to give, in

R E P O R T OF

PROCEEDINGS

the opinion of the mine managers, fair specimens of the general type
of country rock encountered in the different mines.
Complete analyses were made of these samples. The results are
given in the following table:
COMPOSITION OF COUNTRY ROCK FROM D E V E L O P M E N T D R I V E S AND
HANGING AND FOOT-WALL OF BROKEN HILL LODE

Silica, SiO s
Alumina, A1 2 0 3
Ferrous oxide, F e O
Ferric oxide, F e 2 0 3
T i t a n i u m dioxide
Ti02
Manganous oxide,
MnO
Lime, CaO
Magnesia, MgO
Potash, K 2 0
Soda, N a 2 0
Sulphur, S
W a t e r hygroscopic
W a t e r combined

Juncttion
North

British

Broken
Hill
Pty

Block 10

South

Zinc
Corporation

63.90
15.22
7.43
0.15

64.34
15.58
5.74
0.20

59.64
16.82
7.25
0.15

59.10
18.20
7.25
0.40

64.66
14.88
5.98
0.10

60.26
17.97
7.25
0.08

2.34

0.98

1.96

2.50

2.46

2.10

2.33
1.30
1.09
4.04
1.08

2.46
2.60
0.76
2.31
1.14
0.54

3.25
0.85
0.73
3.56
1.03

2.40
0.66
1.25
4.76
1.13

2.56
1.32
0.84
3.77
1.60

1.74
1.01
1.44
4.78
0.95

0.20
1.47

2.14

0.35
3.65

0.15
2.27

0.06
1.42

0.20
2.29

100.55

99.66

99.24

100.07

100.00

100.07

These figures show a striking contrast to those obtained for the
various ore samples. The composition of the ore samples from different
parts of the lode showed very considerable variations. The composition
of the country rock from different parts of the lode, on the other hand,
shows a surprising uniformity. About 80 per cent, of this rock, in all
the samples, is made up of aluminium and iron silicate. The bulk of
the remainder is made up of silicates of potash and manganese. The
only acid radical present in any quantity is silica.
Dr. Russell: Workers in the U.S.A. had lost cases in the Compensation
Courts because the question of other dusts had been introduced. In
U.S.A. silicosis seemed to develop in direct proportion to the silica
content and the dust concentration. At Cripple Creek miners who
developed silicosis left as soon as the altitude began to trouble them.
Silicosis undoubtedly developed there.
Dr. Cunningham described two cases: the first a stone-cutter, who
was employed for fifteen years on sandstone and then fifteen years
on marble. The post-mortem showed the ash of the lung to contain
5 per cent, silica. The second, a miner who developed silicosis, left
the industry and eight years later developed tuberculosis. The ash
of the lung contained 45 per cent, silica.
While there is some evidence that with cessation of exposure to
silica, in, the absence of tuberculosis, much silica finally leaves the
lung, marble dust may expedite this.
There have come to one's attention some cases in which silicosis
developed in grinders who had worked for a short time on sandstone

THIRD SITTING

and later for many years on artificial grindstone. Some miners with
ten to twenty years' exposure to dust very low in free silica developed
silicosis rapidly when they moved to an area with much higher silica
exposure.
Some interest attaches to one case of pneumonoconiosis in a worker
with dust exposure limited to nine years' milling talc (magnesium
silicate). The industry as a whole has not yet been investigated.
Dr. Russell : Italian workers who had been exposed to Carrara marble
dust developed silicosis when working on granite in the U.S.A. as fast
as the Scottish workers employed there.
Dr. Badham : Other dusts than silica could produce fibrosis. Cement
workers in the United States had been known to suffer from diffused
generalised fibrosis. Fibroses resulting from dusts containing little
or no free silica should be put on record. Asbestos, talc, ashes, and
certain silicates produced fibrosis.
Dr. Mavrogordato : Professor Haldane had added metallic dust to
silica. Silica alone was not intense but acted by accumulation; metallic
dusts gave inflammation; cobalt and manganese gave the more intense
immediate reaction.
III. Dust Trapping and Dust Masks
Dr. Fisher: In dealing with this subject he would, of course, only
speak of his own experience. The boring in and blasting of rock in a
coal mine is an occasional and not a continuous process. The danger
to the workers' health due to dust inhalation having been established,
attention was focussed on ways and means of preventing this inhalation
from taking place. His only remark about water was that a waterspray, as distinct from water passing down the drill is ineffective and
it must be remembered that some dusts have a greater affinity for water
than others. Water could not always be made use of, so dust traps
were tried—there are several of them either in use or being tried out;
two have definitely been approved of as efficient for their purpose.
They all work on the same principle, namely a jet of compressed air
coming from the air supply to the drill draws off the dust and deposits
it in a bag-container, made of a specially selected flannel, which allows
the air to pass but retains the dust.
The weight of the trap shown is 26 lb. only, including the upright
support which is telescopic, and which grips the roof and iloor in virtue
of a spring. It all fits into a long box; bags may be protected by being
in some kind of cage.
Dust traps undergo a severe test—they are taken underground and
to the actual face being worked. They are fixed up by an employee
of the mine and numerous dust slides are taken while the drill is in
operation, on many occasions Kotze or Zeiss and Owen's konimeters
being used simultaneously.
The standard adopted was an indication of safety, being 300 particles
per cubic centimetres with a Kotze konimeter, the slide being untreated
in any way.
Whether ultra-microscopic particles pass through the back is of
course a question he could not answer.
He wouli ike to remind them that the Various Industries (Silicosis)
Scheme, 1928—in force 1 February 1929—applies to coal mines and
repeat what he mentioned yesterday, that the demand for these compact,
and as far as he could test, effective dust traps exceeds the rate of supply.

REPORT OF PROCEEDINGS

He should think that with the serious problem of humidity and tuberculosis the use of dust traps could be reconsidered on the Rand.
As far as masks are concerned workmen have for many years
tried to improvise a barrier of some kind that would prevent the dust
from entering their lungs. These were practically useless-—invariably
the nose was exposed and most of the breathing done by the nose. He did
not agree with the sweeping c ndemnation of all masks. There are
processes in which the exposure risk is slight—men working on stone
in the open, for instance—where a mask would so render the amount
of dust breathed in negligible, and where it is not possible to draw off
dust by exhaust. A mask made by Messrs. Siebe Gorman is being
tried at a quarry where a man worked who died of silicosis. The mask
is probably known to you all; it consists of a light rubber face piece,
inhaled air has to pass through numerous wafer-like cotton filters, the
expired air passing out by means of mica valves. He had worn one
in an intense concentration of dust made by throwing it on his face
and the back layers of the filters have, as far as ordinary observation
goes—which he admitted is not far—been perfectly clean.
A mask which will mean the man being connected by a length of
tubing to a main air supply will be limited in its application.
Dr. Cunningham described a mask of positive pressure type consisting
of cloth covering the face, to which air is delivered, sufficient to keep
the mask ballooned. The air escapes from the sides and front due to
an air pressure inside, high enough to prevent ingress of air containing
dust or fumes.
Dust counts in samples of air from inside were very low.
Granite cutters are wearing the mask without complaint except for
the low temperature of air delivered during the first fifteen minutes
of operation in winter time.
The mask is comfortable, inexpensive and effective, but limited in
use to those who are relatively stationary at their work.
Dr. Böhme: Masks were objectionable because of the resistance to
respiratory air. Masks were, therefore, being introduced presenting
a large surface of small mesh which gave a higher resistance to dust
and a smaller resistance to air.
IV. Adhesion of Dust by Hygroscopic Methods
The Chairman : These methods had shown no advantage over
water, and since at that time the disadvantages of water had not been
fully realised no further action was taken.
Dr. Orenstein suggested that Professor Hall might consider research
into the question of masks on a labyrinth system without a filtering
medium.
The Chairman read the following letter received from Mr. Ussher:
USSHER AND HALL INVENTIONS, P T Y . L T D .

P.O. Box 3450, Johannesburg, 14 August 1930.
W. Gemmili, Esq.,
Chamber of Mines, Johannesburg.
DEAR MR. GEMMILL,

Re Silicosis.
As you may remember, I spent over a year underground in
research re dust laying.

THIRD SITTING

When a solution of crude treacle was used during blasting, no
dust could be blown off the drive walls, etc., either a few minutes
after blasting, or next morning.
When drives were sprayed twice within five or six weeks, the
rock faces remained wet and sticky for over a year in places where
water dried up in less than an hour.
Dust laid once by treacle was apparently laid for years—if not
permanently. The cost of the process was only a fraction of the
cost of dust-laying with water.
The then Government Mining Engineer reported to Parliament
that " water would do all that treacle did, but that the effect
of treacle was apparently permanent ".
In a second report he claimed, as a proof of the efficiency of
water, that in a series of thirteen tests on the City Deep, the average
dust content of the samples taken was only 1.6 milligrams, but
this result was almost entirely due to treacle and not water.
I was informed that the Medical Officer on the City Deep
reported that the death rate for the year had gone down from
the highest on the Rand to the lowest, and that the number of
cases of pneumonia among the natives had decreased by 50 per cent.
After considering all the reports of the experts and their tests,
Sir Lionel Phillips decided to introduce my process in all mines
controlled by the Central Mining and Rand Mines Corporations.
The Chamber of Mines opposed my patent, but Mr. Justice
Wessels decided, after hearing the evidence, that I had proved
the efficiency and novelty of my process, and ordered the patent
to be issued.
The then Government Mining Engineer, having insisted that the
Regulations as to the use of water must be carried out strictly,
it was useless to proceed to lay dust with treacle, only to wash
it all away next day.
Where treacle is used, no water-sprays are necessary, and no
miner need get wet or work in over humid atmosphere from that
cause. The relationship of the quantity of water used to eliminate
the dust is roughly 500 gallons of water only, as against 1 gallon
of treacle solution.
Even Mr. Stuart Martin, who was at first rather hostile to the
process, afterwards said that in his opinion the use of my process
would become more essential and inevitable as our mines increased
in depth.
My patent has expired and I have no financial interest in the
use of my process, but I would be glad of an opportunity of giving
the results of my former labours to the Conference, and of answering
any questions they care to ask me.
Yours faithfully
(Sgd.) Lancelot Ussher.
Dr. Orenslein: Treacle and other fluids had already been tried.
The fall in the incidence of pneumonia was universal all over the reef,
but it had not been sustained. A hygroscopic substance retained the
large dust but minute dust did not settle on treacle, and even with
the use of water treacle would be washed away.
The Chairman: The advantage of treacle was that it might reduce
the use of water and thus reduce the humidity.

REPORT OF PROCEEDINGS

Mr. Roberts: The Mining Regulations required the use of water in
quantity, and it was, therefore, impossible to experiment with hygroscopic substances.
Dr. Orenstein: The reporters should bear in mind the possibility
of experimenting with hygroscopic and other sticky substances.
Mr. Phelan: The discussion had seemed to show that the dangerous
dust might consist of particles so small that they were invisible. He
had considerable diffidence in venturing anything in the nature of a
suggestion to experts of such recognised competence as the members
of the Conference, but the methods of counting dust particles to which
reference had been made were apparently not applicable to the counting
of particles of this minute size. He wondered, therefore, whether it
would not be possible to adopt for the purposes of a dust count the experimental method used by J. J. Thomson for the counting of the number
of ions in an ionised gas. The method followed was a simple one. A
known volume of the gas was enclosed in a bell jar and ionised. The gas
in question was given a degree of humidity and was ionised for example
by exposure to X-rays. A sudden reduction of pressure caused the
formation of a fog, the water condensing on the ionised particles. The
fog wa? allowed to settle in the bell jar and the rate of fall of its upper
surface was observed.
A formula discovered by Stokes established a relationship between
the size of the drops and the rate of their settling and the diameter of
the drops could, therefore, be calculated. If the total amount of condensation were measured, i.e. the volume of water condensed, the number
of drops could then be calculated. It seemed to him that this method
could be applied to air containing minute particles around which the
water would condense instead of round the ions.
Dr. Orenstein : He believed that the British General Electric Company
were experimenting with a method of this kind but he had been unable,
as yet, to obtain their apparatus. Photographic and photo electric
methods of dust determination were being tried.
(The Conference adjourned at 12.50 p.m.)

FOURTH

SITTING

Monday, 18 August 1930, 9.30 a.m.
Chairman:

DR. L. G. IRVINE

AETIOLOGY AND PATHOLOGY OF SILICOSIS

Dr. Mavrogordato : Some dusts acted favourably and others unfavourably on silica. Very little was known about their particular
behaviour. Any inert, relatively insoluble dust which got into the lungs
in sufficient quantity favoured fibrotic conditions; silica was only relatively insoluble.
A dusty lung was a wounded lung and its cleanliness or dirtiness,
in the surgical sense, was of great importance. The terminal bronchioles
and vestibules were the first places attacked and if they were damaged

FOURTH SITTING

the dust which had once passed the terminal bronchiole stayed where
it was.
Observation had shown that the smaller incidence of silicosis among
natives, as compared with Europeans was due to intermittent employment; natives who were employed continuously developed silicosis
more rapidly than Europeans. The sputum of broncho-pneumonia
cases indicated that a good deal of dust and pigment might be got rid
of during broncho-pneumonia. The natives braved exposure to silica
dust and subsequent rest enabled the bronchiole epithelium to recover
and eliminate much of the dust by the same way in which it entered
the lung.
As regarded the infective element, practically every fatal case in the
Witwatersrand fields died with tuberculosis. But tuberculosis was not
the only infective factor. Experimentally he had had no difficulty in
producing chronic unresolving pneumonia by intra-tracheal injection of
an animal that had previously been exposed to silica dust. There must
be a definite infective element if simple silicosis progresses. One problem
was to find out whether silica rock, like certain other inorganic material,
set up an allergic state in the tissues and whethe tissues which were
a'lergic to silica were also allergic to tubercle. The relation between
certain dusts and a subsequent tuberculosis might be explained if the
dust which affected the same tissue as the tubercle toxin not only
rendered it allergic to itself, but also allergic to tubercle without any
secondary immunity to tubercle. He asked what intractable silicates
would do in the absence of free silica and what certain other dusts
would do which had been retained in the lungs of the silicotic, in the
absence of silica ?
Professor Kettle: Nowhere was there such an abundance of pathological material as in Johannesburg and he hoped to learn a great deal
during the Conference. He was particularly anxious to hear more about
the dry bronchiolitis which was apparently an early manifestation of
silicosis. This condition might influence the deposit of silica in the
lungs in several ways. Because of the destruction of the bronchial
epithelium there might be a deficiency of mucus in the air passage,
and dust might therefore pass more easily into the pulmonary tissue ; or,
because of the breaking down of a cell barrier dust-containing phagocytes
might pass more easily into the peribronchial and pulmonary tissue;
or the natural elimination of the dust from the lung might be interfered
with. He would be glad to know in which direction this lesion was
regarded as being particularly important.
He also hoped to have an opportunity of seeing more of the available
material, and learning more about the histology of infective,
especially, tubérculo-silicosis.
The suggestion had been made that silica might damage the tubercle
bacillus as it did the tissues. This was to him a new conception because
all his observations lead him to believe that silica aided the growth of
the bacillus. This certainly appeared to be so in vivo, and he had a
certain amount of evidence to show that silica added to culture media
aided the growth of the organism in vitro.
How the silica acted in influencing the growth of the tubercle bacillus
was still unknown, but it appeared likely that it was a metabolic
phenomenon. He thought it was generally agreed that the action
wa a chemical r ne in that the silica und ubtedly was soluble in the
tissues. This could be demonstrated by placing a suspension of
silica in sealed collodion capsules embedded in the subcutaneous

REPORT OF PROCEEDINGS

tissues of rabbits. In two or three weeks the silica was dissolved
and produced its effects on the neighbouring tissues.
He was also anxious to hear the opinion of the Conference on the
animal of choice for experimental work on pneumonoconiosis. From
the anatomical peculiarity of its lungs, the guinea pig, which was so
commonly used, appeared to him to be definitely unsuitable.
Dr. Gardner: Commenting on Dr. Mavrogordato's statement that
ingested silica particles, in contradistinction to other types of ingested
material, exert a preservative effect upon the phagocytes, he would
like to call attention to the following observations.
Haythorn produced a limited degree of fibrous reaction in the ear of
a rabbit by the injection of large amounts of coal dust. After the
lapse of several months the injected particles are found in elongated
compressed cells which resemble fibroblasts. If however an oedema
is produced by constriction of the base of the ear or by immersion in
very hot water the fibroblasts separate and the phagocytes again
assume an ovoid or spherical form. This experiment demonstrates
that the dust is still retained by monocytes and that it is not transferred to fibroblasts.
In the Saranac laboratory a variety of dusts, silica in various forms,
granite, carborundum, aloxite, emery, etc., have been injected into the
peritoneal cavity of guinea-pigs. At various intervals up to nine
months thereafter samples of the peritoneal fluid when withdrawn still
exhibit free phagocytes containing large quantities of ingested dust
particles. If any of these cells are stained supravitally, with neutral
red, a delicate indicator of cell injury, there is no evidence that they
have been damaged. Furthermore there is no evidence of disintegrated
cellular debris in the exudate. However there is no way of marking the
original host cells so that one cannot be sure that the dust particles
may not have been taken up by a successive series of phagocytes.
Nevertheless, as far as can be demonstrated, he has produced no evidence
to show that ingested silica particles are more protective than any
other type of dust. This line of investigation is still being pursued.
Professor Kettle had mentioned effects produced by silica dust upon
the tubercle bacillus. He has been conducting a series of experiments
to determine whether the development of a silicosis will alter the
virulence of the bacilli of a superimposed tuberculous infection. For
this purpose he has infected guinea-pigs by the inhalation of tubercle
bacilli of an attentuated strain known in the laboratory as R. 1. In
normal guinea-pigs such infection regularly produced isolated subpleural
tubercles in the lung together with a massive involvement in the
tracheobronchial lymph nodes. Macroscopic tubercle in the othe" viscera
practically never occurs. Multiplication of the bacilliinthe pulmonary
tubercles brings about caseation after some four to six weeks. The
bacilli then die off and healing of the focus by resolution within a period
of eighteen months to two years is the result. The tubercle in the
mediastinal lymph nodes likewise heals although there is often some
residual fibrosis. Death from this infection almost never occurs.
If an animal, infected in this manner, be subjected to eight hours'
daily inhalation of quartz dust over a period of two or more years
it can be shown that after the elapse of three to five months the bacilli
in the primary foci of infection do not die but apparently quite suddenly
take on a new capacity for growth. The lesion ; spread ; at first locally
and latterly by ulceration into the bronchi the organisms are distributed
into all parts of the lung. The result is a generalised pulmonary
tuberculosis, chronic in its course but usually fatal in outcome. The

FOURTH SITTING

pathological lesions are quite comparable to chronic tuberculosis in
man, often with large trabeculated cavities. Macroscopic tuberculosis
of the liver, spleen, and abdominal lymph nodes is the rule.
, In order to determine if possible the cause of this renewed growth
capacity of the attenuated tubercle bacilli in the silicotic lung, animals
have been killed at intervals of one month after infection. Under proper
aseptic precautions, portions of the lung, spleen and lymph nodes
have been removed for culture and subinoculation into other animals.
This experiment is not yet completed but in the majority of the subinoculated guinea-pigs the infection produced has been comparable to
that produced by subcutaneous inoculation of cultures of the R. 1.
strain, i.e. a non-progressive infection confined to the lymph nodes
adjacent to the site of inoculation. In a certain number of sub-inoculated guinea-pigs the spleens have also been involved but such an effect
can be produced by very large doses of this strain of tubercle bacilli.
At the present time it would appear that the silicotic process in the
lungs of the original series of animals has not increased the virulence
of the bacilli used for infection but that a temporary alteration in environment has been produced which favours the continued multiplication
of the organisms. Removed from this altered environment the bacilli
again revert to their original state.
From the cultures obtained from the silicotic lung a study is in progress
to learn whether bacterial dissociation is favoured by silicosis. No
definite results are as yet forthcoming.
In vitro, bacteriological studies are in progress to discover whether
the addition of silica in various forms to various culture media will favour
the growth of the tubercle bacillus. Like Professor Kettle he had
observed a definite reduction in the initial lag period after transplants
have been made.
Professor Kettle had asked for an expression of opinion as to the most
suitable animal for the experimental study of pneumonoconiosis. At
the Saranac Laboratory he had used guinea-pigs because of their
cheapness and because large numbers may be kept [in a relatively
small space. As he would show in the lantern slides it is possible to
produce quite typical silicotic lesions in this animal within a period of
two years. However the rabbit has certain advantages. Its lung
normally contains large amounts of tonsil-like lymphoid tissue located
directly beneath the epithelium of the bronchi and bronchioles. If
serial sections be cut through these areas it will be found that the
general cuboidal or columnar epithelium lining the bronchi and bronchioles becomes attenuated and flattened over the centres of the lymphoid nodes. Such an arrangement permits a direct and rapid passage
of dust-laden phagocytes from the air passage into the lymphoid tissue.
As a consequence large quantities of dust soon collect in these regions
which ultimately brings about the formation of silicotic nodules much
more rapidly than in the guinea-pig.
He had unreported experiments on monkeys, two baboons and six
rhesus monkeys exposed to the inhalation of granite dust. While far
advanced fibrosis was produced after periods of one to two years, in
every case accidental death from spontaneous tuberculous infection
introduced a disturbing complication.
Before definitely deciding upon the most favourable animal for use
in pneumonoconiosis experiments he thought that other non-rodent
mammals (cats, dogs, sheep and swine) less susceptible to spontaneous
infection with the tubercle bacillus should be tried.

REPORT OF PROCEEDINGS

Dr. Strachan: As the result of observations made with Dr. Simson
on the sputa of asbestos workers, they had come to the conclusion
that the phagocytes had the power of elaborating a substance or
substances, usually iron-containing, with which ingested particulate
matter was isolated in the cell, and so the cell was protected against
the action of this particulate matter.
In time the ingested particulate matter might be dissolved as could
be demonstrated in the case of " asbestosis bodies ".
Professor Loriga: In his opinion there was no material difference
between the reaction of cells to various dusts; it belonged to the
category of reaction by irritation. He did not believe in the chemical
theory and considered that silicosis was not a different pathological
entity to other pneumonoconioses.
Sir Spencer Lister suggested the use of B.C.G. culture in experimental
work on silicosis developing in dusted animals.
Dr. Gardner: Such experiments were being made in his laboratory.
Dr. Strachan (in introducing the discussion on the Pathology of
Silicosis): In Dr. Simson's and Dr. Strachan's Report, they accepted
as correct Miller's work on the lymphoid tissue of the lung, but subsequent investigations have led them to modify that acceptance.
They have examined a relatively large series of cases of status
lymphaticus and have noted the distribution of the lymphoid tissue
in the lung. There were no complicating lung lesions to obscure the
picture. A series of photographs demonstrate that the lymphoid tissue
in the lung is essentially and functionally related to the air-passages
and to their terminations. The photographs show the absence of the
tissue in the blood-vessel walls and also that where lymphoid aggregates
occur in contact with pleura or trabecular the essential relationship
is to the adjacent air-spaces. All the lymphoid tissue in the lung is
functionally related to the air-passages and to their terminations.
Any other apparent relationship is only accidental.
In cases other than those of status lymphaticus lymphoid tissue is
present in the same situations though to a less degree. Any condition,
such as silicosis, which may stimulate hyperplasia of lymphoid tissue
will make it more manifest and they have frequently seen this in
cases of silicosis.
The importance of the lymphoid tissue can be demonstrated from
the atlas and from the series of large photographs elaborating the
atlas. The dust cells accumulate in and around the sites where normally
lymphoid tissue is present, but only round the smaller bronchi and
the bronchioles and their terminations. They have never seen a true
silicotic lesion in relation to the large cartilagenous bronchi.
There occurs a cellular fibroblastic reaction which terminates in a
dense ball of hyaline fibrous tissue.
These lesions show first in the tracheo-bronchial glands, then in the
pleural and finally in the lung substance.
There is a definite entity—simple silicosis—i.e., silicosis uncomplicated by infection, particularly tuberculous infection. This condition
can progress to a considerable degree—even to massive fibrosis and
in these case-' biological tests for the presence of tubercle bacilli have
proved negative.
In contra-distinction to simple silicosis there is a type in which
infection plays a part and to which the term " infective silicosis " can

FOURTH SITTING

be applied. The chief type of infection is tuberculosis and then one
may use the term tubérculo-silicosis.
The nodules are more exuberant in their fibrous tissue and more
rapid in growth and central necrosis occurs early.
Degenerative changes of fatty nature sometimes followed by calcification are seen in simple silicosis but only very rarely is there necrosis.
Necrosis may be taken as an indication of infection.
In the progress of the disease, in the simple type structures are displaced
whereas in the infective type they are infiltrated and destroyed.
His experience during the last six years suggests that remote effects
involving heart, liver and kidneys were not common in simple silicosis,
and his impression is that such lesions are not any commoner in miners
than in the general population; in infective silicosis where there is
massive destruction and fibrosis associated with emphysema there may
be however right-sided cardiac failure as a terminal phenomenon.
The picture of the " classical type " of miners' phthisis is in his opinion
that of an infective silicosis.
Dr. Simson: Macroscopically, it is often difficult to distinguish
between simple silicosis of massive type and tubérculo-silicosis.
Microscopically, some cases of tubérculo-silicosis show evidence of
active tuberculosis in the lung tissue intercalated between the adjacent
silicotic nodules. In other cases the usual signs of tuberculosis as
evidenced by small round mononuclear cells, endotheloid cells, and
giant cells are absent. Definite necrosis in the nodules, however, is
present. In such cases, although tuberculosis might be suspected
from the microscopical evidence, a biological test is the only reliable
means of diagnosis.
He would add that in tubérculo-silicosis the tubercle bacillus is
living on a medium mainly composed of fibrous tissue, and that this
probably accounts for the slowly progressive nature of the lesion.
In the lung tissue outside the limits of the silicotic nodules the disease
advances much more rapidly as here the bacillus is living on a good
medium which includes blood plasma.
The Chairman: It was a well-known fact that in tubérculo-silicosis
infection was not readily communicable to members of the patient's
family.
Dr. George asked the Chairman how he would decide whether
death was due to or accelerated by silicosis and/or tuberculosis in the
following cases:
(1) When the cause of death is lobar pneumonia and simple silicosis
is present.
(2) When the cause of death is broncho-pneumonia and silicosis is present.
(3) Death due to heart failure, with simple silicosis present.
The Chairman: He agreed with Dr. Strachan that the classical
silicosis of former days had an infective element. Many of the miners
then employed were Cornishmen who went home when their health
began to fail and the majority of these were shown by post mortem
to have died of tuberculosis. In miners who broke down suddenly
and died, often within three months, there was rapid necrotic silicosis.
But on the other hand many at that time died of heart failure with
cyanosis and ascites and with no clinical signs of tuberculosis.
At the present day there was earlier manifestation of the tuberculous
element, but there was enough normal lung left to place the patient
in a better condition to control a tuberculous infection. The cases
nowadays lived longer.
4

REPORT OF PROCEEDINGS

In reply to Dr. George he said that a certain rough justice had to be
adopted. If a man had a well-marked silicosis and died of a primary
cardiac lesion the Bureau would allow that silicosis had been contributory
and the same applied to acute respiratory diseases.
Dr. Truter: At the time of the influenza epidemic of 1918 it had
been impossible to differentiate between the case mortality of a man
with a slight degree of silicosis and of a man with no silicosis at all.
Dr. Pringle : At Springkell Sanatorium and Wedge Farm Sanatorium
it had been definitely concluded that fibrotic obstruction was an element
in the cause of death; but these cases were not very numerous. The
more impressive cases were those of simple silicosis suddenly breaking
down. Post mortems had shown that the cause of the rapid breakdown
was always the breaking down of a tuberculous infection.
Dr. Watt: In the influenza epidemic some men affected with a slight
degree of fibrosis died, while others did better than the general population. He could not say whether the latter had acquired immunity
in a previous epidemic.
Dr. Strachan: It might be worth while for the reporters to draw
up a definition of silicosis and infective silicosis. A fresh report on the
incidence of cancer of the lung should also be asked for.
Professor Kettle asked Dr. Simson for information on his experiments in inoculation, because it was well-known that tuberculosis in
the guinea-pig was very variable in its manifestations.
Professor Böhme: There were a considerable number of cases of
advanced silicosis in Germany which died of heart failure, with dilatation
and failure of the right heart. These symptoms are due to fibrosis and
emphysema of the lungs. The combination of silicosis and cancer was
found only in the Schneeberger district, and was believed to be due to
the inhalation of radioactive dusts.
Dr. Orenstein asked whether there was any experimental or pathological evidence to determine whether dilatation of the heart, and
particularly liability to respiratory disease, was associated with pneumonoconiosis.
Dr. Middleion referred Dr. Orenstein to the mortality data in the
Decennial Supplement for 1921-1923 of the Registrar-General in
Great Britain.
Dr. Kranenburg asked whether a person with a negative von Pirquet
reaction was allowed to be employed in the mines. If so, was he treated
with the Calmette vaccine ?
The Chairman: It was impossible to make von Pirquet tests on the
large number of men examined.
Sir Spencer Lister: Examinations carried out at the Institute for
the past three years showed that 60 to 70 per cent, of the natives gave
a positive von Pirquet reaction. The tests had been followed up in
many cases and post mortems correlated with the results of the von
Pirquet tests. It was found that a much larger percentage of deaths
occurred amongst those natives who originally showed a positive von
Pirquet reaction than amongst those whose reaction was originally
negative. The Institute was at present experimenting with B.C.G.
vaccine as a prophylactic in adults.
(The Conference adjourned at 12.50 p.m.)

FIFTH SITTING

FIFTH

SITTING

Monday, 18 August 1930, 2.30 p.m.
Chairman: DR. L. G. IRVINE

Profesor E. H. Kettle showed microscopic preparations illustrating
the modification of an artificial miliary tuberculosis by silica.
In the first series of experiments rabbits received four to eight intravenous doses of amorphous silica or of mine dust over a period of ten to
fourteen days. They then received an intra-venous inoculation of living
tubercle bacilli as did a control series of animals. In the animals prepared
with silica, miliary tubercles were much more numerous than in the
control animals, and bacilli were much more numerous in the lesions.
The limitations of the experiment were discussed.
In the second series interstitial lesions were produced in mice by
silica and other agents, particularly calcium. The mice then received
tubercle bacilli intravenously. Tubercle bacilli are found in the silica
lesions in much greater numbers than in the lesions produced by calcium.
A further series of sections illustrated preliminary experiments in
the production of pulmonary lesions by the intra-tracheal injection
of different forms of silica.
GENERAL TECHNIQUE

OF DUST

EXPOSURES

Dr. Gardner: Guinea pigs and rabbits are kept in cages along the
walls of a room 6 by 8 feet in diameter and 8 feet high, provided with
two windows 3 by 5 feet in diameter. A cloud of dust is maintained
in the atmosphere of the room by apparatus located in an alcove,
6 feet from the nearest animal.
This apparatus consists of a horizontal
drum 2% feet long and 1% feet in diameter, placed 8 inches above the
floor. Its top is open and in it rotates a metal paddle whose shaft
projects from the end of the drum and then through the partition into
an adjacent room in which is located an electric motor. By properly
selected pulleys and counter shafting, the speed is so regulated that
the desired dust concentration can be maintained. Ventilation is
secured by opening one of the windows an inch or more from the top.
The animals are kept, generally in pairs in 12 by 12 by 12-inch wire
cages set on racks at the back and sides of the room. While it will be
shown that the dust concentration progressively decreases from the
floor to the ceiling, this factor is compensated by frequently changing
the position of the cages on the racks.
As measured by the operation of the motor, the daily period of
exposure is eight hours, but since the animals remain in this room
during the night, the actual exposure is much longer, a considerable
time being required for all the dust in the atmosphere to settle. In
warm weather the period is somewhat shortened by opening the windows
when the motor is stopped during the evening.
The dust concentrations employed for this work have approximated
those of the worst industrial conditions. For asbestos dust we have
maintained an average concentration of 46.5 million particles, 10 to
0.5 miera in diameter per cubic foot of air. Recently this concentration
has been increased approximatly ten times. In granite dust experimentation the concentration was much higher (288 million particles

REPORT OF PROCEEDINGS

per cubic foot). The figures for quartz and carborundum dust concentrations he neglected to bring with him but if his memory had not
failed they are of the order of those mentioned for granite dust.
Marble Dust
The first experiments were made with marble dust from Proctor,
Vermont. This substance contains less than 1 per cent, free silica.
Exposure of normal guinea-pigs for periods as long as two years
produced practically no changes other than a hyperplasia of the
lymphoid tissues in the periphery of the lung, together with some
dilatation of the deep lymphatic vessels.
Guinea pigs infected by inhalation of the low irritant strain of tubercle
bacillus R. 1 did not develop a generalised pulmonary tuberculosis.
But there was, however, a well-marked failure of the normal process
of resolution in many of the tubercles associated with the development
of calcification of their caseous centres. In the light of subsequent
experiences with other dust this calcification is now ascribed to the
fact that resolution was retarded and caseous matter was retained in
the lung for a sufficient period for calcareous deposit to occur. A similar
finding in carborundum dusted animals strongly suggests that the
excess of calcium supplied by the inhaled marble was not the determining factor.
Granite Dust
The action of this dust upon the lung tissues is too slow to exert its
maximum effects during the exposure periods possible in guinea-pigs.
Inhaled particles are ingested by alveolar phagocytes which tend to
accumulate in the air spaces along the terminal bronchioles and
alveolar ducts. No evidence of fibrosis has been observed in the
walls of such passages but only a slight chronic inflammatory infiltration. Considerable amounts of dust are carried by phagocytes
into the lymphatic system. A certain number of dust cells can be
found in hyperplastic nodules of lymphoid tissue in the periphery of
the lung but no evidence of fibrosis is discoverable. Much more dust
is accumulated in the tracheo-bronchial lymph nodes and here a true
fibrosis of the silicotic type has been observed in animals exposed for
two or more years. The lymph vessels in the lung are widely dilated
from the hilum to the pleura but evidence of thrombi of dust cells is
lacking. The cause of this dilatation was temporarily at least ascribed
to the production of an obstructive fibrosis in the lymph nodes of the
mediastinum.
Carborundum Dust
Inhalation produces in the normal guinea-pig a reaction similar
to that of granite. Great masses of dust laden phagocytes are discovered in the terminal bronchioles and their alveoli. No nodular fibrosis
has developed within a period of four years. In the tracheo-bronchial
lymph nodes where much greater amounts of dust have collected
there is true fibrosis which tends to be somewhat nodular in type. More
marked than in any other dust studied are the changes in the connective
tissues of the bronchi and large blood vessels. They are definitely
thickened by the formation of extremely vascular granulation tissue
which is infiltrated with numbers of lymphoid and phagocytic cells.
Through this tissue course many greatly dilated lymph vessels.

FIFTH SITTING

Quartz Dust
The phagocytes which have ingested quartz particles exhibit a much
greater degree of activity than those containing any other type of dust
yet investigated. Instead of remaining for long periods in masses along
the terminal bronchioles as in the case of granite and carborundum
dust the quartz-filled cells which are present in great numbers actively
migrate along the walls of the alveoli, atria, etc., until they reach
the small terminal collections of lymphoid tissue. They surround these
structures and rapidly invade them. The lymphoid demerits at first
undergo hyperplasia, but very shortly the newly formed lymphoid
cells appear to decrease in number and are finally completely overshadowed by the mass of large clear-stained dust containing phagocytes.
This collection of cells is then surrounded by a layer of cuboidal epithelium which sharply demarcates it from the surrounding tissues. Thus
far no fibrosis is present but only a nodule perhaps similar to that
which Dr. Mavrogordato has called a " pseudotubercle ". In the centre
of this area where innumerable particles of quartz have been concentrated fibroblasts begin to make their appearance. Their source has
not been determined; they may have come from the original reticulum
of the lymphoid nodule. A cellular fibrosis gradually replaces the
entire nodule of phagocytes. Degenerative changes make their appearance at its centre and later the structure assumes the characteristic
hyaline appearance of the fully formed silicotic nodule seen in the
human being. Presumably the majority of the larger lesions form in
the manner described about nodules of peripheral lymphoid nodules.
Some may also develop within the alveolar septa or at least these
become greatly thickened and often encroach upon and ultimately
close the adjacent air spaces.
More rapidly than with other dusts, quartz particles are carried into
the tracheo-bronchial lymph nodes and there provoke nodular fibrosis
even earlier than occurs in the lungs.
The lung of the rabbit presents peculiar anatomical conditions which
favour an early development of well-marked silicotic nodules. The
lymphoid tissue being directly under the thinned-out bronchial epithelium can apparently " collect " phagocytes from fair-sized air passages
with great rapidity. A case of extensive silicosis in the rabbit is illustrated in which dust exposure was continued for 6 months followed
by a period of one year in a normal atmosphere. In rabbits killed at the
end of the dust exposure there were great numbers of dust cells in the
lymphoid tissues but fibrosis had barely begun to occur. After the
elapse of the following year little or no elimination of the dust apparently occurred but on the contrary fibrosis had progressed at a rapid
rate. The tracheo-bronchial lymph nodes, 18 months after beginning
the exposure, are almost completely replaced by hyaline fibrous tissue.
Asbestos Dust Inhalation
The.reaction to this dust has differed markedly from that of any
of the above-described particulate dusts. Instead of coming to rest
in the terminal alveoli as is the case with these types, asbestos particles
and fibres are apparently largely caught in the irregular walls of the
respiratory bronchioles. There, phagocytes engulf the dust particles
but they do not, in the guinea-pig, migrate with them to the lymphoid
tissues. Instead they remain in situ and as more particles are inhaled
they tend to accumulate in the same location. Some of the material

REPORT OF PROCEEDINGS

is carried by the phagocytes directly into the walls of the near-by air
passages. Solution of the dust takes place as indicated by the development of " asbestosis bodies ". Possibly stimulated chemically by
the dissolved silicate of magnesium, the fibroblasts in the walls of the
respiratory bronchioles begin to proliferate and ultimately a tube-like
formation of delicate fibrosis envelopes these structures. Contraction
of this connective tissue constricts the air spaces so that their epithelial
lining assumes the cuboidal forms of the atelectatic lung. This gives
the involved area a gland-like appearance. The development of
asbestosis bodies is thought to be a result of hydrolysis and solution
of the magnesium silicate of the asbestos molecule. A theory of their
formation is discussed. The reaction to inhaled asbestos dust within a
period of two and a third years is strictly localised to the respiratory
bronchioles. Intra-pulmonary and mediastinal lymphoid tissues play
no obvious part in the defence against this dust.
The reaction of the rabbit's lung differs from that of the guinea-pig
in that phagocytes do carry the inhaled asbestos into lymphoid tissues
in this animal. Furthermore no typical abestosis bodies have been
discovered in this animal; evidence of fibrosis is likewise lacking.
However the observations in the rabbit have only been carried over a
period of 330 days.
Albino rats have also been employed and in them it has likewise
proved impossible to discover an appreciable number of asbestosis
bodies. The high frequency of pulmonary abscess in these animals
may have been responsible for preventing the inhalation of an effective
quantity of dust.
Radiograms of the silicotic and asbestosis guinea-pigs, taken both
during the life of the animals and again after the lungs had been removed
from the body have been shown. They demonstrate that much greater
evidence of disease can be detected in the somewhat over-distended
lung which has been removed from the thorax. The appearances are
comparable to those encountered in human disease. In the discussion
it would appear that the reaction to inhaled asbestos and to a lesser
extent to granite and carborundum is analogous to the condition
described as bronchiolitis by the South African observers.
From these studies of the effects of various types of inhaled dust it
will be noted that connective tissues react to produce fibrosis in various
portions of the lungs or their lymphoid tissues. With granite and
carborundum fibrosis has been observed only in the tracheobronchial
lymph nodes; with asbestos dust the reaction is confined to the walls
of the respiratory bronchioles; with quartz dust reaction occurs both in
intra- and extra-pulmonary lymphoid tissues as well as in the fine
alveolar septa. It is believed that the difference in localisation of
various dusts is a function of the action of these dusts upon the phagocytes which ingest them. Possibly this may be due to the degree to
which the cells become filled with dust particles. Overloading would
mechanically impede the migration of the phagocyte. In the case of
asbestos dust the size of the ingested particles may also hinder transportation. As a working hypothesis it is proposed that any dust
possessing the necessary chemical composition will provoke fibrosis
when and where the phagocytes concentrate it in sufficient quantities
in contact with pre-existing connective tissue cells.
Sir Spencer Lister: It was essential for the Conference to reach a
conclusion on the question whether silicosis developed as a primary
condition or was always dependent on a prior infective process, usually

• FIFTH SITTING

tuberculous in nature. The animal experimentation seemed to point
to the former conclusion.
Dr. Gardner: Care was taken to eliminate tuberculosis as a spontaneous infection.
Dr. Strachan: Dr. Gardner had shown how investigation into the
«ffect of dust on the lungs should be carried on, and the difference
between phthisis and non-phthisis dusts, viz. whether they were brought
into contact with the connective tissues or not.
Dr. Moore: The necessity for dependence on radiographic findings
in the diagnosis of silicosis and industrial pulmonary fibrosis in general
has led to the use of diagnostic standards which must be regarded as
very largely arbitrary in nature.
With this fact in view, a series of experiments has been undertaken
at the Commonwealth Health Laboratory, Bendigo, with the object
of correlating the radiographic with the histological findings in experimental animals subjected to conditions calculated to reproduce those
experienced by miners working underground on a quartz reef.
The following report represents an interim statement of work accomplished to date, and the research is still proceeding.
Choice of animals. — The animals chosen for the experiment were
Australian rabbits which were in the wild state at the commencement
of the experiment. Many of them were not fully grown at the time of
capture. Very little difficulty was experienced in keeping them in
good condition during experimentation, and only three out of 120 died
from illness or injury during the course of over six months. The normal
life of these animals is three years.
Scheme of investigation. — In order to reproduce underground conditions of dusty atmosphere as closely as possible, boxes were constructed
approximately 10 by 11 inches in area and 9 inches deep, provided
with an inlet vent about three inches from the floor at one end, and
an outlet vent near the lid at the opposite end. These vents were
y2 inch in diameter.
For the purpose of convenience in handling, these boxes were
constructed in rows of ten and provided with a hinged lid over the whole
length of the row, sawn at intervals to enable one box to be opened
at a time. The interior of each box was fitted with a glass jar into
which dipped a short length of curved piping connecting the interior
of the jar to the inlet vent. In each jar was placed finely-powdered
dust to a depth of 1 or 2 inches.
The animals were placed one in each compartment for one hour
daily six days in each week, and, by means of a bellows, a dusty
atmosphere was maintained in the box throughout that period. This
atmosphere was sufficiently dust-laden to cause a readily visible haze
in the box, and was maintained by blowing at five-minute intervals.
During the rest of each day and at the week end,, the animals were
allowed to feed and rest in the pens.
The animals were weighed each week and weights recorded.
Variations in treatment. — The rabbits were divided into series for
the purpose of representing the possible phases of simple silicosis and
silicosis complicated by tuberculosis.
Series 1 comprised animals treated by quartz dust only.
In Series 2 the animal-i were treated throughout the experiment bv
quartz dust mixed with killed B. tuberculosis.

REPORT OF PROCEEDINGS

In Series 3 the animals were treated for three months with qua tz
dust only and after that with dust mixed with killed B. tuberculosis.
Series 4 is represented by animals subjected to the inhalation of
killed B. tuberculosis for five minutes daily for seven days; then, after
a fortnight's interval, subjected to daily dusting with unmixed quartz
dust.
A fifth Series was treated by intra-pulmonary injection of 1 milligram
of bacillo-casein1, and then by daily dusting with unmixed dust.
These series were controlled as follows:
Series 1, 2, and 3 were controlled by rabbits to which no treatment
was administered. Series 4 and 5 received treatment by killed bacilli
and bacillo-casein respectively, but no further dusting.
The treatment of the series has been continued to date for a period
of over six months in the case of Series 1.
Preparation of dust. — The dust used was obtained from mine dumps
in Bendigo and was crushed to pass through a 200-mesh screen. The
analysis of the dust is as follows:
Silica Si02
Ferric oxide Fe2Os
Alumina A1203
Loss on ignition
Undetermined

Per cent.
92.46
6.27
0.53
0.36
0.38
100.00

The dust concentration maintained in the boxes during the experiments has been estimated by the Owen's dust counter and has averaged
5,300 particles per cubic centimetre within half a minute of blowing,
2,200 within five to five and a half minutes of blowing and 2,000 within
ten to ten and a half minutes. Thus a high dust concentration has
been maintained in the boxes throughout the experiments.
Preparation of bacilli. — A human strain of B. tuberculosis obtained
from the Commonwealth Serum Laboratories was cultured on glycerin
bouillon medium for six weeks, then autoclaved at 120° C. for fifteen
minutes. The culture was then filtered through paper, washed with
saline, and the residue dried in a hot-air steriliser for three hours at
120° C. The dried killed bacilli were then ground in a mortar and
bottled.
As required this bacilli dust was mixed with the quartz dust in a
proportion estimated to subject each animal to a daily dose of 0.06
milligrams. The quartz dust was baked to destroy other infective
agents prior to mixing.
The process described, according to Calmette 2 , should not affect
the toxicity of the bacillary endotoxins. Accordingly, this method
was used to provoke a tissue response in the experimental animals
with a view to providing a parallel to an exceedingly mild or unobservable tuberculous lesion in human beings.
For animals in Series 4 who were subjected to the inhalation of pure
killed bacilli prior to dusting, a special box was made with glued and
1

CALMETTE: Tubercle Bacillus Infection in Man and Animals, p. 53. 1923,
English
edition.
2
Op. cit., p. 70.

FIFTH SITTING

morticed joints. This box was divided into two compartments, a
small one which contained the bacillary dust communicating with a
larger one for the body. Two small observation windows were provided.
General procedure. — The rabbits were identified by numbered leg
bands and were weighed weekly and the weights recorded.
Those
receiving infected treatment were segregated from the others, and
boxes used for this treatment were not used for other animals.
From the commencement of dusting, animals from each series
and control group were killed at stated intervals, a post mortem examination made with particular regard to the condition of the lungs, the
lungs and heart weighed, the lungs radiographed by a special method
and macroscopic preparations and microscopic sections prepared.
In Series 1 and 2 one rabbit from each was killed weekly for eight
weeks, then one fortnightly for a further eight weeks; since then
animals have been killed at four-weekly intervals. In Series 3, five
rabbits were killed at intervals during sixty-seven days' dusting with
infected dust, after two to two and a half months' dusting with simple
quartz dust. In Series 4, the dusting period extended from seven to
sixty-eight days in different rabbits, and in Series 5, from seven to
thirty-nine days. Normal controls were killed at four-weekly intervals
and controls to Series 4 and 5 at intervals of two or three weeks.
Method of killing animals. — At the commencement of the experiment, chloroform was used to kill the rabbits, but this was found to
produce intense pulmonary congestion and was abandoned in favour
of electrocution. It is not certain that this method is ideal, as in
certain of the normal control animals a good deal of pulmonary congestion was observed. The first and second series of dusting were repeated
on a fresh set of animals up to the eighth animal, using electrocution.
Examination. — At the post-mortem examination, after inspection
of the lungs in situ the larynx was severed and the heart and lungs
removed together. The heart was then removed and weighed, and the
lungs were weighed also. One lung was then tied off at the bronchus
for histological purposes and cut off.
Radiography. — The remaining lung with the larynx was then placed
in a specially constructed vacuum box and inflated by negative pressure
therein. Radiographs were then taken by a special technique for soft
tissues.
Preparation of specimens. — The remaining lung was then dissected
for the preparation of macroscopic colour specimens and for microscopic
sections.
Results of examinations. — At this period, after six months' observation in the case of Series 1, and somewhat shorter periods in the
other Series, the microscopic sections and radiographic films have
been examined and the-weights of the heart and lungs compared with
the body weights.
Weights. — Comparison of the weights of the hearts freed from the
vessels and the lungs and bronchi with uniform portions of the laryngés
with the body weights at death has failed to reveal any constant ratio.
This is probably due to several factors amongst which varying stages
of maturity of the subjects and the varying presence of acute infections
and congestion are probably the most important. No constant growth
curve has been obtained either, probably largely on account of the
second factor mentioned above.
Microscopic sections. —The examination of these sections has hitherto

REPORT OF PROCEEDINGS

revealed few evidences of chronic change in the lung tissues although,
in the later sections, an increase in the amount of fibrous tissues appears.
The characteristics observed relate to acute changes typified by
peribronchial and sub-pleural vascular engorgement with patchy
areas of pneumonia. Pleural thickening has been observed in some
sections. These acute manifestations appear to come in waves, although
there is a wide variation among individual animals in response to the
treatment. Reaction appears to be more general in animals receiving
tuberculous treatment.
Radiographs. — Certain films of the series show evidence of patchy
pleural thickening, others show an increase in the strength of peribronchial markings, while others again show a general clouding of the
tissues, in some cases approaching a mottled appearance. The typical
picture of radiographic silicosis has not yet been obtained.
Correlation of radiographic with histological results. —• Comparing
notes from the microscopic sections, it becomes evident that the cloudy
appearances on the films are due to acute pneumonic and congestive
areas in the lungs. The chronic effects of dust inhalation are not so
far evident radiologically.
Discussion. —• At this stage in the experiments few conclusions can
be drawn, but advantage has been taken of this unique occasion to
present a progress report. Underground conditions have been fairly
paralleled by the experimental conditions, and accordingly, it is hoped
that the near futu e will show us the development of a chronic fibrotic
pulmonary condition.
The observations completed so far, however, are not without interest
in view of the greatly increased incidence of pneumonia among miners
on new fields where a large proportion of the workers are young men,
new to the occupation. This incidence and the mortality rate, are
found to decrease as the years advance.
This feature has been discussed at length in the Report of the Royal
Commission on Pulmonary Disease amongst Miners in Western
Australia, 1911 (J. H. L. Cumpston), and the case is cited in this report
of a young man, killed by an explosion while at work, whose lungs
revealed at post-mortem examination, a pleuritic patch, and an apical
area of pneumonia. This man had been employed underground for
one year.
The incidence of pneumonia during the early days at Broken Hill
(Australia) was pointed out by Armstrong and the South African
experience in this direction is well known.
It is noteworthy that practically none of the animals killed showed
emaciation or poor physical condition. The few exceptions were
those suffering from hydatid infestation or from injuries inflicted by
the other animals.
At the present time a few animals of Series 1 and 2 remain. Dusting
has been suspended for the present and these animals will be killed
and examined a later date.
(The Conference adjourned at 5 p.m.)

SIXTH SITTING

SIXTH

SITTING

Tuesday, 19 August 1930, 9.30 a.m.
Chairman:

DR.

A. E.

RUSSELL

A letter from Messrs. Kodak (South Africa), Ltd., was read, in reply
to the Chairman's letter of thanks for the albums presented by Messrs.
Kodak to the members of the Conference.
The Chairman requested Dr. Russell to take the Chair, as he was
himself partly responsible for some of the papers now to be discussed.
Dr. Russell took the Chair.
THE DIAGNOSIS OF SILICOSIS AS AN OCCUPATIONAL DISEASE

Dr. Irvine: The practical diagnosis of silicosis as an occupational
disease was of great importance from the medico-legal point of view.
It appeared to him also to be a subject upon which a considerable
measure of agreement might be reached by the Conference. Although
there were minor variations in the type of the disease met with in
different countries the evidence adduced showed that it was everywhere
substantially the same disease. Its general type for example was the
same at Broken Hill in Australia as in South Africa despite the difference
in the silica percentages in the respective rock dusts.
The standard of diagnosis which was needed was that of a condition
of silicosis which either caused slight incapacity at the moment or
which was of such a nature as to be a potential cause of incapacity
in the future. It had to be a standard which was fair to both parties
concerned, the workman and the employer.
It was claimed that such a standard could only be reached by a careful
correlation of the results of pathological, radiological and clinical
examination in a large series of individual cases. The Medical Bureau
working together with the pathologists who carried out the routine
pathological work on its behalf had been able to carry out such a
correlation in a series of 400 cases.
The practical result was to show that when interpreted in the light of
such a correlation a technically perfect radiograph taken instantaneously
formed the most reliable single criterion in diagnosis. It was necessary,
however, to supplement the radiological examination by a thorough
clinical examination, including an investigation of the examinee's
industrial and medical history before a final decision could be reached
in any individual case.
The evidence obtained of the effect of the inhalation of silica dust
in excessive quantities over prolonged periods was to show that it
had in general the following phases:
1. A " bronchial phase " consisting mainly of the production
of a dry bronchitis and bronchiolitis. This phase when fully
developed appeared to give the radiographic picture of a generalised
ramifying " fibrosis " or " commencing generalised fibrosis ".
There were already in this phase aggregations of pigment-bearing
phagocytes.
But it appeared to him that the question of what was happening
in the lung and respiratory passages during the long period of

REPORT OF PROCEEDINGS

exposure prior to the development of actual silicosis required
further investigation, both experimental and by observation in
the human subject.
" 2. A simple " nodular phase " based anatomically mainly
upon the small aggregations of lymphoid tissue in the lung. This
condition was actual " silicosis ". It was a distinct and definite
pathological entity characterised by a palpable miliary nodulation
under the pleurae and in the lung substance, with fibrosis of the
root glands. This condition dominated the picture of a clinically
" simple " silicosis, and was progressive up to a point even in the
absence of infection. But probably only in a minority of cases
did it constitute the whole picture even in a clinically simple
silicosis, since in a majority of cases of that condition some small
latent focus or foci of tuberculous infection was commonly already
present.
3. Ultimately in most cases of silicosis there arose an " infective
phase " in which the silicotic process was modified by the presence
of chronic infections and particularly by a chronic tuberculous
infection with the production of areas of " massive fibrosis ".
Extensive massive fibrosis in a silicotic lung was usually of infective
origin and the infection was most commonly tuberculous. Such
lesions were apt to be slowly progressive, but might undergo
prolonged arrest and might cause no constitutional symptoms.
There was applied to them in a general sense the term " infective
silicosis " or in a restricted sense the term " tubérculo-silicosis ".
But one did not classify cases as " tuberculosis with silicosis " unless
an active clinically detectable and deteriorating tuberculosis was present.
In individual cases of silicosis there were many variations in the course
and type of the disease dependent mainly on the relative preponderance
of the dust factor or of the infective factor, and on the earlier or later
manifestation of the latter.
Tuberculous infection might affect a silicotic lung before silicosis
developed, or secondly a limited reinfection of the lung might occur
simultaneously with the development of the silicotic process, or thirdly,
reinfection might occur after the silicotic process was established. The
development of a limited area of tubérculo-silicosis at the site of an
old persistent focus of primary infection was shown to the Conference.
There was accepted the importance of the view that silica was a
soluble cell poison and that this circumstance is a factor in creating
a predisposition to tuberculous infection, but this factor did not appear
to enhance the virulence of the infection. One would emphasise the
feature that a tubérculo-silicosis, as defined, was generally a process
of low virulence, with frequently long periods of arrest, with a slow
spread in the lung and to other organs, and with a low transmissibility
of infection to other people.
As regards the practical definition of silicosis, a sparse palpable miliary
nodulation of the lung was the South African definition of a slight
degree of silicosis. In some cases of slight tubérculo-silicosis however
there might be no disseminated miliary nodulation but merely a few
limited areas of massive fibrosis in the apical or sub-apical regions with
a scattering of infective nodules in their neighbourhood. Either
condition would be shown in a good radiograph.
(A number of cases illustrating the correlation between the radiographic
appearances and the actual pathological condition present in cases of
silicosis were then demonstrated.)

SIXTH SITTING

In arriving at a standard of diagnosis for purposes of compensation
it would be wise to rely as a general standard on the type of radiograph
which showed indications of commencing nodulation, since this was
definitely representative of a slight degree of silicosis. A certain amount
of deviation from this standard might be allowed but only to expert
examiners. The Bureau for example, as the result of its experience
of the correlation described, recognised cases showing the radiographic
appearances of a simple generalised arborisation, especially if accompanied by evidence of an infective element, as indicative of silicosis,
provided these appearances had arisen in a miner under observation
and were accompanied by definite evidence of respiratory disability.
He had no personal experience of any other type of silicosis than
that produced on the Rand.
The South African Act recognised two conditions, " silicosis " and
" tuberculosis with silicosis ". " Silicosis " however might be predominantly " simple " in type without any indication of infection, or
" partly infective " in type, in which group indications of latent infection
were present. But one did not speak of " tuberculosis with silicosis "
unless an active clinical deteriorating tuberculosis was present.
Some practical definition was needed from the pragmatic standpoint
of what constituted silicosis, and he would also like to see the Conference
come to some agreed classification of radiographic films.
Remarking on the tabulation in Paper 10 of the causes of death in
cases of silicosis, he called attention to the preponderant role played
by tuberculosis as the immediate cause of death and the relatively
minor role played by acute respiratory diseases. In this connection
however it was to be noted that in all cases in which active tuberculosis
was demonstrably present that condition was returned as the cause of
death although in some cases it was not the immediate cause.
He briefly called attention to the observation that the original
physical type of the affected man has an important bearing on the
type of the disease which is contracted and upon its clinical course.
Extensive investigations into physical tests had been carried out in
the mining districts of Western Australia. A limited investigation of
this nature had been made at the Bureau. These were the tests applied
in the Air Force and similar organisations. In these institutions the
man was bent on doing his best, as his job depended on his physical
condition, but in the class of man whose financial outlook would be
governed to a large extent by his doing his worst, he did not think
that this means was helpful in estimating disability.
Disability was estimated from a clinical examination, the history
of the man, and the general impression he made. In ordinary routine
work the disability was estimated by common sense clinical methods.
In the ante-primary stage the disability might be nil and did not exceed
25 per cent. In the primary stage disability due to the disease ranged
from 25 per cent, to 50 or 55 per cent. More than 60 per cent, disability
justified inclusion in the secondary stage.
Dr. C. Badham : He wished to draw attention to the fact that, although
they found in certain industries, such as the Broken Hill silver mines,
radiographic appearances which closely resembled those found in South
Africa, nevertheless, remembering that they were dealing with a dust
containing certainly not more than 15 per cent, of free silica, the rest
of the dust being composed of intractable silicates, he was in no way
convinced that the disease which they found in Broken Hill was the
pure type of silicosis found in Johannesburg. The difficulty in their
case was that they had in their State an Act which excluded from

REPORT OF PROCEEDINGS

compensation men who had been affected by silica dust. Many of these
men had worked in dusts containing percentages of silica ranging up
to 35 per cent., and from observations he was by no means convinced
that the silica was the whole story of their disease. He found confirmation of that view in the fact that where they had, as in Broken
Hill, 85 per cent, of silicates, most of them intractable, they found in
the lung after death intractable and. other silicates. It was therefore
reasonable to assume that silicates had a considerable effect on the
production of fibrous pneumonoconiosis.
In regard to the inoculation of guinea-pigs with simple silicotic
nodules, if the tubercle bacilli were of only low virulence, as those
described by Dr. Gardner, he took it that such slight reaction would
not be overlooked by the pathologists in the inoculation in Johannesburg
of the simple silicotic nodules.
Dr. Gardner: The reaction was slight as far as generalised tuberculosis was concerned. This low virulent strain of bacilli injected into
the guinea-pig often produced an enlarged, firm, palpable nodule,
which could not be overlooked. He doubted very much whether the
lesions produced by a human silicotic tubercle bacillus would be as
slight.
Dr. Middleton: In Great Britain they had a series of conditions
ranging from the inhalation of silica dust, containing about 98 per cent.
free silica, down to dusts which contain a negligible quantity of free
silica, or none at all. Medical examinations with radiological examinations had been made, and showed that the effect on the lung seemed
to bear a relationship to a true silicosis in so far as the dust to which
the sufferer was exposed contained free silica. By that was meant a
type of silicosis produced by free silica dust similar to the dusts produced
in South Africa. All the granites in Great Britain were not like the
true granite of Vermont. They varied chemically, from about 33 per
cent, of free silica to a low free silica percentage. In cotton and other
textile workers there was a peri-bronchial type of fibrosis, which approximated to the fibrotic picture obtained in the low silica containing
dusts. It was necessary to have names for other conditions which
arose, because if compensation was made in respect of them, the
awarding of such compensation would depend on the definitions and
the indications given for making the diagnosis.
Dr. Russell: Vermont granite had a fairly consistent composition
of silica. The average temperature half the year round was 36° F. The
workmen worked in closed places, and they had very high percentages
and a fairly consistent type of silicosis developing pneumonia. That
was directly comparable to other parts of the States, where the men
worked in the open, and did not require heating, and were also not
in close proximity. In the South they had completed a study in the
cotton industry, and found that the X-rays from these cotton workers
were quite different.
Dr. Böhme: Edling in Sweden has described pneumonoconiosis
amongst miners in the Swedish coal mines. The coal worked in these
mines is very soft and free from mineral impurities. The Röntgen
picture resembles that of silicosis. Anatomical examination has,
however, revealed that no fibrosis of the lung occurs, merely filling
up of the alveoli and bronchioles with coal dust, together with atelectasis and congestion of the contiguous portions of the lung. Very
varying anatomical processes may produce similar Röntgen pictures.

SIXTH SITTING

The forms of pneumonoconiosis caused by silicates and coal require
to be subjected to profound anatomical examination before the Rontgen
picture can be accurately interpreted.
Professor Kettle: What was the exact anatomical lesion in the
X-ray plates of ramifying fibrosis ? In fig. 5 of the paper entitled
" The Clinical Pathology, Radiology and Symptomatology of Silicosis ",
he could not see anything in the microscopic picture to correspond
with -the cases pictured there.
Dr. Fisher: He had been impressed by the small variety and amount
of exposure to silica dust, and the gross changes found in the lungs
after death. He had also been struck by the fact that although large
cavities appeared in the lungs, the pathologist always insisted that
there was absolutely no sign of tuberculosis. He thought that in
future cases they should try to get biological tests carried out in some
of these lungs.
Dr. Cunningham:
The South African classification described by
Dr. Irvine was in use in Canada. The cases among miners and granite
cutters were divided into these stages for practical purposes. In addition
however there was at least one other group of cases which had a mixed
fibrosis, which the pathologist described as being due not to silica
alone nor to tuberculosis alone, with little or no nodulation.
Professor Hall: Perhaps the most important point discussed was
the attempt to come to some general agreement on the definition of
silicosis, the definition of how it was to be recognised, and how some
lead could be given to countries which had to consider the question of
legal arrangements. There were one or two points on which he would
like information. Was bronchiolitis one of the early conditions which
arose in these miners ? A great difficulty was to understand the
position as regards tubérculo-silicosis. In considering the nomenclature,
they had to consider the difficulty of the layman, who rather objected
to the term " ante-primary ". He would like to know if there was a
simple silicosis of any importance apart from tubérculo-silicosis and
silicosis with tuberculosis. Was it to be supposed that persons who
became infected with tubercles and died of open tuberculosis later,
had gone through a stage of tubérculo-silicosis which eventually had
come into a stormy condition, or had they had a simple silicosis
throughout until they got a late infection ?
Dr. Irvine : To label a case " tubérculo-silicosis " and not a case
of " tuberculosis with silicosis " was in a sense illogical, but there
was a clinical and pathological distinction, and that was why the
term " tubérculo-silicosis " was used. There were men who continued
with their work, showing no constitutional disability who had a
quite massive consolidation in their lungs. It would probably be wiser
in the medico-legal aspect not to apply the term " tubérculosilicosis " to such cases, but simply to say that they showed a silicosis
or fibrosis of infective type.
Dr. Simson: During his stay in Sheffield he had quite an extensive
experience with tuberculous guinea-pigs after inoculation, doing about
forty or fifty a week. Tubercle bacilli of low virulence or in very minute
doses might not give rise to any lesion. In such cases the body
reactions were sufficient to destroy the bacilli.
In the experimental work carried out conjointly, with Dr. Strachan
the site of inoculation was carefully examined. Films were made

REPORT OF PROCEEDINGS

from any glands showing the slightest enlargement and examined in
the usual way.
If there had been any doubt about enlarged glands they would have
been reinoculated.
Dr. Strachan: There was no possibility of their having missed any
lesions whatever. Negative results were obtained in every case, which
showed that none were missed.
Dr. Gardner: In the older literature on silicosis a great point was
made of lymphatic obstruction. It had always impressed him that
probably this had played a very important part. In dusts such as
carborundum they had been able to detect the presence of well-developed silicotic lesions in the bronchial lymph nodes, which were probably
responsible for the development of a stasis in the affluent lymph vessels.
What physiological activity or lack of activity might result in such
a lymph stasis was something to be determined. With such a stasis
the channel for the elimination of dust was obliterated. They had not
found any dust containing phagocytes, except very rarely, in these
dilated lymph vessels. This seemed to indicate that this process of
lymphatic obstruction should be given a more prominent part
There were apparently two types of disease in which silicosis and
tuberculosis were co-existent. In one the tuberculous processes were
atypical and did not conform to those encountered in uncomplicated
cases. In another type lesions comparable to those found in simple
tuberculosis could be identified.
The usual lesions of uncomplicated pulmonary tuberculosis are
generally divided into three main groups:
(a) Lesions of infection, the " primary complex " ;
(b) Apical tuberculosis, a lesion of reinfection of endogenous or
exogenous origin which tends to heal but may be re-activated
and may spread at any time;
(c) Acute and chronic involvement of the lower portions of the lung
generally due to broncho-genic extensions from the apical focus.
Blood stream dissemination is more or less accidental in nature and
plays little part in the evolution of chronic pulmonary tuberculosis.
In the radiographs exhibited to the members of the Conference
there was one beautiful illustration of a " primary complex " in the
process of activation by inhaled silica dust. Another series of films
illustrated a definite picture of tuberculosis in the apex of a lung which
under the influence of inhaled silica dust was actively spreading to
involve the lower portions of the lung.
In his own experience the speaker had also seen several cases,
chiefly in granite workers, in which an apical tuberculosis was spreading
downward through the lung simultaneously involved with silicotic
changes. In a series of six lungs from Barre, Vermont, two showed this
type of change
But in many of the radiographs exhibited to the Conference the
specific evidence of typical tuberculous lesions were obscured by the
silicotic changes.
The question arises whether the combination of tuberculosis with
silicosis generally creates a new pathological condition in which the
tuberculous elements are no longer typical in their appearance and
mode of progression or whether these are only obscured by the concomitant reaction to the inhaled silica.
In attempting to answer this question it would be desirable to obtain
exact information as to the incidence of detectable apical tuberculosis

SIXTH SITTING

both active and inactive in silicotic individuals and as to the frequency
of spread of the infectious process into the lower portions of the lungs
by aspiration from the bronchial tree.
The speaker also enquired whether it was possible to discover the
source of infection in the atypical combinations of tuberculosis and
silicosis. If such forms resulted from the combined action of the two
irritants, the tubercle bacillus and the silica dust, were each necessarily
present within a given tuberculo-silicotic nodule ? If so by what
pathway did the tubercle bacilli reach the site of reaction ?
To mention an entirely new question—is the radiographer correct
in ascribing all shadows seen in an X-ray film to the presence of fibrosis ?
A shadow is cast on the film by any substance which obstructs the passage of the ray through the normally air-containing lung. A pneumonic
exudate or even congested and engorged blood vessel may exert such an
effect. Why then in dealing with a chronic disease should any area
of increased density in the radiogram be called fibrosis ?
Dr. Strachan: There was a considerable body of opinion in South
Africa agreed in involving lymphstasis as a factor in the development
of silicosis. He was of opinion personally that lymphstasis, at least
in the simple non-infective silicosis, played no part. Certain workers
had shown by experiment that when the lymph glands were blocked
with carbon there was no lymphstasis at all. There was, as Dr. Gardner
had demonstrated, dilatation of the lymphatics, but there was no
apparent interference with the flow of lymph in these dilated lymphatics.
The dilatation of the lymphatics might be simply a part in the establishment of a collateral circulation, or opening up the circulation
to permit of the further lymph glands being reached. That was their
interpretation of the causes in the early simple silicosis. That would
not account for the absence of dust cells in Dr. Gardner's cases, but
their interpretation of their sections would indicate that there was no
lymphstasis. Presumably there would be further findings of oedema,
or something of that nature. The point of lymphstasis was important
in relationship to the interpretation of the general ramifying fibrosis.
It had been raised in that connection because in certain sections of
lungs, particularly in the later stages, the lymphatics were filled with
pigment and pigment-laden cells, but there were on the other hand
cases which showed the typical general ramifying fibrosis in which
there was no evidence of dilatation of lymphatics or of pigment-laden
lymphatics. To reach a definite conclusion in regard to this condition,
much more material would have to be examined.
As regarded statistics on the foci of the typical types of tuberculosis,
he could state quite definitely that there were cases of these foci in South
African silicotic cases.
Aspiration manifestation of silicosis in the silicotic cases occurred
only in the infective cases, and in these only when the infection had
gained the upper hand.
Infection elsewhere was a point which had not been emphasised
sufficiently. Both in natives and Europeans there were certain cases
in which the manifestations in the lung were minimum, if not absent,
but in the lymph glands there was evidence of gross tubérculo-silicosis,
and a not infrequent sequence of events in these cases was a dissemination
of tubercle to other organs.
Dr. Gardner: He had found non-progressive tubercle in' the abdominal viscera of about 25 per cent, of cases of simple chronic pulmonary
tuberculosis. He did not feel however that the blood stream played
5

REPORT OF PROCEEDINGS

an important part in the dissemination of tubercle bacilli within the
lung in the chronic stages of pulmonary tuberculosis. With regard to
lymphstasis, a dilatation of the peripheral lymph vessels of the lungs
appeared in the absence of an obstructive lesion in the tracheobronchial
lymph nodes. In this case, the dilatation could only be related to
intra-pulmonary irritation. He was anxious to discover whether this
appearance was indicative of any change in the rate or direction of
lymph flow.
Professor Kettle: He would still like an answer to his question about
the bronchiolitis. He would like to know what was the significance
of the pathological process. Was it because of atrophy of the epithelium and a defect of secretion, and therefore a matter of holding up
of the dusts, or was it because of the lack of the mucous membrane
that the dust got through so rapidly ? Was there any evidence of an
increased phagocytosis in these circumstances, or was it a question
of an interference with the exit of the dust once it had been inhaled?
In experimental work he had been very much impressed by the
determination of the dust in the phagocytes to the lymphatic vessels'
system. It seemed that the lymphatic must enter into this process
rather more than had come out in the various discussions.
Dr. Strachan: He did not deny that the lymphatic apparatus played
a very important part in this condition, but it had an active and not
a static part.
Professor Kettle:
If the lymphatic glands were obstructed and
filled with silica, there must surely be obstruction of the lymphatics.
Dr. Strachan: In the specimens at the Institute there was no
difference from the normal lung. He thought the glands were enlarged
and there was a certain amount of obstruction in the glands. If there
had been stasis, and stasis of any degree, the pigment and the dust
would remain in the lung.
Dr. Gardner: He considered that the abdominal lymph glands were
involved. The individual abdominal viscera simply passed these dust
cells through to the lymph nodes which drained them.
Dr. Strachan: If there was a blood stream infection one would
naturally expect to find manifestations of the lesions in the spleen.
These were extremely rare.
Bronchiolitis was put forward simply as an observed fact. As regarded
the question of exit, it seemed that the bronchial epithelium was active
in the process of carrying away material. What mattered was not so
much the interference with the exit of the particles as the possibility
of their increase. The bronchiolitis of asbestosis threw a considerable
light on the subject in relation to the X-ray picture. The degree of
bronchiolitis in silicosis was less than in the asbestosis. The reaction
in asbestosis was much greater, and so great as to prevent the involvement directly of the terminal alveoli.
Dr. Mavrogordato : One of the difficulties the Conference would have
to face would be the distinction between a silicosis and a pneumonoconiosis. The problem was to get at silicosis as a specific occupational
disease and define it. It was much more difficult to spread it to other
types of pneumonoconiosis. If a man was going to get a silicosis he
would precede his silicosis with fibrous ramification. He had seen a
number of workers getting on for sixty who would yet show lung
fibrosis of that kind. They were apparently physically fit, as men inthe neighbourhood of the sixties go.

SIXTH SITTING

Personally he did believe that lymph played a part. He looked at
the spread from the lungs somewhat differently from Dr. Strachan. He
thought that the fact that the pigment cells passed so rapidly up into
the neck and down into the abdomen tended to support the supposition
that the normal lymph flow was interfered with. An acute infection
of the lung in a man who had not been exposed to dust for several
months would show the alveoli filled up with pigment-laden cells. That
suggested that the pigment-laden cells had been retained somewhere,
not necessarily in the lymphatics. In his experience there was in these
cases plenty of pigment-laden cells held up in the distended lymphatics.
It seemed that at first there was an interference with the normal lymph
flow, then a pretty ready passage in an abnormal direction, and then a
holding up of the pigment-laden cells somewhere where they could get
back into the lung.
Professor Hall: Whilst it was quite true that general fibrosis might
go on to silicosis, yet quite a number of cases did not go on to simple
silicosis.
Dr. Irvine: The radiographic picture of general ramifying fibrosis
was a definite pre-silicotic phase. At post-mortem something like
50 per cent, of such cases showed slight silicosis in the sense defined.
The practical working test was that if a man in that condition with a
long service had developed the condition underground in the course
of his service, and there was disability, generally with some emphysema,
they were inclined to compensate at that stage, under these restrictions,
but not in general. He would not for a moment say that any worker
who showed that type of plate was entitled to compensation. A number
of miners could go on for several years in that condition without progressing further, but if a man continued in his occupation, a definite
silicosis usually followed in a year or two. A man might however
develop that condition and remain in it practically indefinitely if he
was removed from underground work. It was necessary to get at the
facts of the " actual generalised ramifying fibrosis ", which did not
necessarily spell fibrosis.
Dr. George : A few figures with regard to Broken Hill miners may be
interesting. In eight years, out of 160 mine workers withdrawn as
suffering from simple silicosis 76, or 47.5 per cent, developed or died
of pulmonary tuberculosis. A total of 66, or 41.2 per cent, died of all
causes. The average age at death of those dying of pulmonary tuberculosis was forty-eight years; in those dying of other causes the average
age at death was fifty-eight years. In eight years, of 101 men classified
originally as suffering from silicosis plus tuberculosis there were living
only 15—86 per cent, had died. In all but eight cases the cause of
death was pulmonary tuberculosis. The average age at death of those
dying of pulmonary tuberculosis was 49.7 years, and in those dying
of other causes 51.6 years.
The chief causes of death in these two groups of men who did not
die of pulmonary tuberculosis were: lobar or broncho-pneumonia 8,
other respiratory disease 7, heart failure 8, chronic nephritis and/or
cerebral hemorrhage 11, malignant disease 4, surgical emergencies 2,
suicide 2. With regard to the number of deaths from chronic nephritis
and its complications, it must be remembered that many of these men
had suffered from lead poisoning in addition.
Dr. Moore: In our experience at Kalgoorlie (Western Australia) and
in Tasmania the performance of physical tests and the estimation of
vital capacity was of very little aid in the diagnosis of silicosis.

REPORT OF PROCEEDINGS

Dr. Kranenburg: The X-ray of the sandstone workers showed,
for 16 persons, mottling in 2 cases and snowstorm type in 5 cases. The
X-rays of 74 Belgian limestone workers showed mottling in 5 cases.
Dr. Watt: The branching shadows in an X-ray film were caused by
the blood vessels, by the lymph vessels, and by the supporting
connective tissue.- In heart disease, where there might be some
increase in the vessels in the lungs, there were ramifying shadows,
which might also be caused by the dilatation of the lymph vessels.
The air-containing tubes threw a negative shadow. It was conceivable
that the dilatation and blood vessels would give those shadows without
necessarily a marked fibrosis.
(The Conference adjourned at 12.30 p.m.)

SEVENTH

SITTING

Tuesday, 19 August 1930, 2.30 p.m.
Chairman:

DR.

A. E.

RUSSELL

DIAGNOSIS (continued)

Dr. Böhme: He had heard that 70 per cent, or more of the natives
had a positive von Pirquet reaction; he thought therefore that the
conditions were not so very different from those in Europe. Most
of the natives had a tuberculous infection in their youth; why were
they so liable to contract tuberculosis when they came to the mines,
or into contact with European people ?
Dr. Mavrogordato : Very weak solutions had been used for testing
purposes. Were they to use the same strength as in Europe, the positive
reactions would probably be about 90 per cent. But whereas in Europe
a positive reaction was regarded as related to a localised tubercle of
a more or less chronic type, in South Africa the fact that a native had
a positive tuberculin reaction did not make the least difference to his
after-coming type of tubercle. It was at death generalised. In fact
the natives who got the least tubercle were those who had a negative
reaction. This was the exact reverse of the European experience.
Dr. Badham: It has been suggested by speakers that the appearances
seen in the radiographs showing diffused generalised fibrosis are due
to bronchiolitis or effusion.
He desired to point out that in certain of these cases there is no
increase of sputum and the radiograph remains unchanged for three
years after leaving dusty work.
The condition appeared to him to resemble closely the radiographic
appearance of asbestos and he thought that he would find the pathology
of these lungs to resemble that found in asbestosis.
He had not found this condition in individuals not exposed to dust.
Dr. Cunningham:
It appeared that cases showing more general
ramifying fibrosis did not get tuberculosis to anything like the extent
that ante-primary cases did. Having in mind the fact that the amount

SEVENTH SITTING

of simple tuberculosis was comparatively low, something must happen
just short of ante-primary to make tuberculosis much more serious or
much more frequent in these miners than earlier.
Dr. Irvine: Tuberculosis in a silicotic lung might arise from a persistence of a primary infection, or it might come along with the dust and
develop practically simultaneously. He thought these latent foci either
remained inactive, in which case the condition did not advance to an
obvious condition, or, on the other hand, these foci became active,
either rapidly or over a period of years. They became active and
progressive either locally, or spread by inhalation, or through the
blood stream and caused a definite tuberculous infection. There was
the further possibility of reinfection from outside the lung after the
silicotic process had become definitely established.
Professor Loriga: After the Lyons Congress, the Medical Labour
Inspectorate in Italy had asked for collaboration from various experts
in the study of the pathology of marble workers. Investigations were
made by Dr. Turano at Carrara, and Dr. Bianchi at Massa, the chief
centres of the marble industry. Further enquiries were carried out
by Dr. Lovisetto, of Turin, and by Dr. Mussa. Their conclusions had
already been submitted to the Conference. He exhibited various
radiographs of the results obtained by these investigators.
Dr. Russell: Having regard to the apparently fairly long period of
occupation in the marble industry, it appeared that in Italy it was the
practice to teach school children a trade as part of the school curriculum. Children commenced learning in the marble industry from
the age of ten years.
Dr. Gardner: He had had the good fortune of seeing a series of
asbestosis films, which Dr. Lanza had in his possession. The majority
of these cases were much like those Professor Loriga had shown, in
that there was an accentuation of the linear markings in the chest
film, with relatively little of the fine mottling. Dr. Irvine had shown
a film that morning which showed more of the mottled appearance,
which was perhaps a little more comparable with the picture obtained
by the experimental disease in guinea-pigs.
Dr. Russell : Dr. Lanza was particularly interested in the incidence
of tuberculosis in his people. He was of the opinion that they had
more of a chronic bronchitis than a tuberculous complication.
Dr. Middlelon: He had been recently associated with Dr. Merewether,
of the Factory Department, in an enquiry on workers actually
employed in asbestos factories at the time of the examination.
The general result was to show that asbestos dust gave rise to pneumonoconiosis of a fine type, distinct from the silicosis. A number of fatal
cases had occurred in Great Britain, and he had been present at one
or two of the post-mortem examinations. The findings were that the
appearance of the lung corroborated the X-ray appearance, so far
as the absence of the large nodules was concerned. There was a general
fibrosis throughout the lung. Usually the end of the case was either
tuberculosis or a broncho-pneumonia. The remarkable thing about
asbestos disease was the apparent small involvement of the lungs
when examination, either clinical or radiological, was carried out.
The patient lost condition and went down hill fairly rapidly, when the
clinical and radiological signs were scarcely to be made out. The
incidence of tuberculosis in such cases was interesting.
Intensive study was being made with regard to prevention to ascertain

REPORT OF PROCEEDINGS

how far the dust could be eliminated from the industry and with regard
to further legislation and compensation. A Bill had been before Parliament in the last few months to provide compensation for persons disabled
by the pneumonoconiosis due to asbestos dust.
Dr. Badham: No asbestosis disease had so far been found among
Australian workers.
Dr. Orenstein: Asbestosis had been studied for some time by one of
the medical men in South Africa in the mines of the Eastern Transvaal.
Dr. Slade claimed to have found a number of cases of asbestosis with
incapacity.
Dr. Irvine: Dr. Slade had sent up one man who had been in an
asbestos mill for six and a half years, and showed quite a definite
generalised arborisation in the radiogram, not quite of the silicotic
type. It resembled it, but was a little more diffuse. Dr. Slade had
been sending up to Drs. Simson and Strachan a large number of sputa
from natives in which they had recovered asbestos bodies.
Dr. Simson: He had had the opportunity of examining material
from six cases of pulmonary asbestosis from a mine in Southern Rhodesia.
All showed definite fibrosis and two were complicated by active tuberculosis.
In a case with a history of exposure to dust for two months asbestosis
bodies were found in the lung alveoli, but there was no evidence of
fibrosis.
He was interested in the examination of sputa for asbestosis bodies
with a view to determining whether their presence was an indication
of pulmonary fibrosis. Dr. Strachan and he had examined sputa from
fifty subjects who had worked in an asbestos mill. Asbestosis bodies
were demonstrated in the sputa of forty-eight of these, and in most
of them by the direct film method. The shortest exposure was five
months. Another case had a history of four months' exposure to the
dust of the mill and three months' exposure to underground conditions.
Dr. Strachan and he were informed that underground conditions are
not likely to cause fibrosis as there was no excess of injurious dust.
Professor Hall: One of the objects of the Conference was to arrive
at some international standard which would be applicable to all countries for future investigations. He therefore moved the following
resolution :
There is a pathological condition of the lungs due to the inhalation
of free silica dust. It can be produced experimentally in animals.
It can be detected by clinical, radiological and pathological means
with sufficient accuracy to separate it from other pneumonoconioses and to afford a fair basis for legislative measures.
Dr. Böhme seconded the resolution.
After some discussion, it was resolved unanimously, on the motion
of Dr. Orenstein, that the resolution as amended by Professor Hall
should be referred to the Reporters. The resolution as amended was
as follows:
There is a pathological condition of the lungs due to the inhalation
of free silica dust. It can be produced experimentally in animals.
It can be detected by clinical and radiological means, which can
be confirmed with the above pathological condition with sufficient
accuracy to separate it from other pneumonoconioses. It also
affords a fair basis for legislative measures.

SEVENTH SITTING

Professor Hall: The next step was to come to some general agreement, based upon the lines of the South African experience, on a
definition of the three stages of silicosis. He moved the following
resolution:
The first stage shall be defined as characterised by:
(a) appearance of the earliest detectable physical signs of the
disease;
(b) radiographic appearance not less than the presence of nodular
shadows together with an increase of hihrm shadows, linear
shadows and pulmonary reticulum, and
(c) with or without impairment of capacity for work.
The second stage is characterised by:
(a) the further development of the physical signs found in the
first stage;
(6) radiologically an increase in the area of the nodular shadows
with a tendency to confluence of the individual nodules, and
(c) the presence of symptoms with some degree of impairment.
The nomenclature classifying fibrosis in various degrees should be
replaced by the terms "slight", "moderate" and "well-marked"
linear radiation.
Dr. Orenstein seconded the resolution.
It was unanimously agreed to refer this resolution to the Reporters.
Professor Hall: He felt that the so-called infective silicosis, whether
tubercular or not, would be much better left out altogether. There
should be a separate heading " tuberculosis " with silicosis as a distinct
condition.
Dr. Middleton : Tuberculosis should be recognised as an entity, and
should be placed parallel with or alongside the three stages of silicosis.
Dr. Orenstein: In connection with silicosis it was necessary for the
Conference to express an opinion as to whether tuberculosis was a
disease which was accelerated by the presence of silicosis, or whether
silicosis accelerated existing tuberculosis. He took it that the general
opinion of the Conference was that the two were unconnected. If
that was the case, he entirely agreed with Professor Hall's suggestion
that tuberculosis should be dealt with as an auxiliary entity to
silicosis, but before he would commit himself to that view he would
like to know whether the delegates from other countries agreed.
Dr. Cunningham asked whether if silicosis and tuberculosis were
defined as distinct conditions the " infective " type of case would be
labelled " tuberculous ".
Dr. Hall: No.
Dr. Irvine:
The South African definition of tuberculosis was as
follows :
That a man shall be considered to be suffering from tuberculosis
if either he is expectorating the tubercle bacillus or is suffering
from closed tuberculosis to such a degree as to seriously impair
his working capacity.
They introduced the term " infective silicosis " because that was
a pathological entity and because it was necessary to describe it in
describing silicosis at all. They did not recognise tuberculo-silicosis
as tuberculosis for the purposes of the Act until it was active and
progressing and causing constitutional deterioration.

REPORT OF PROCEEDINGS

Dr. Orenstein: The Reporters could take it that the Conference
agreed to the view that tuberculosis in relation to silicosis should be
dealt with as a condition parallel to it and adding to the disability.
Dr. Moore: The question of radiographic technique had not yet
been mentioned.
Dr. Russell agreed that it was essential to make some reference to
radiography.
Dr. Orenstein asked if he was right in understanding that the Conference had accepted Professor Hall's proposal that in the present state
of knowledge of the pathology of the disease the view was not considered
justified that silicosis was essentially tuberculous, at least as seen in
South Africa.
Dr. Russell replied in the affirmative.
(The Conference adjourned at 5 p.m.)

EIGHTH

SITTING

Wednesday, 20 August 1930, 9.30 a.m.
Chairman:

DR. L. G. IRVINE

DIAGNOSIS

(continued)

Dr. Simson: In the lungs of subjects exposed to the influence of
injurious dust there might be condensation of the tissues in and about
the bronchioles, and these areas of condensed tissue might be responsible
in part for the radiographic appearances known as linear radiations.
Somewhere in the site of the condensed tissue, in silicosis the nodule
of fibrosis developed.
In 1916 Drs. Watt, Irvine, Pratt, Johnson and Steuart demonstrated
nodules appearing on the linear radiations, and defined this phenomenon
as " segmentation of the linear shadows ". Dr. Böhme likened it to
beads on a string.
Dr. Gardner, when demonstrating cases of experimental asbestosis,
showed radiographs of the chest of a living guinea-pig and of the lungs
in a state of over-expansion from the same pig after death. In the
living pig the radiograph showed radiating linear shadows, but in the
over-distended lungs the radiating linear shadows had become segmented
and appeared as a fluffy kind of mottling. This might account for the
shadows seen in the peripheral part of the lung. Thickening of the
bronchi, dilatation of bronchial lymphatic and blood vessels might
account for the increase in the shadows near the root of the lung.
The Chairman: He agreed that in the bronchial phase "fibrosis"
was a compromising term. Fibrosis or potential fibrosis did, however,
occur in many cases which showed a radiograph of generalised arborisation, because this picture persisted afterwards, as if there were
slight but definite fibrosis.

EIGHTH SITTING

Dr. Gardner: Carborundum dust inhalation gave an example of
increased vascularity. X-ray films of human cases exposed to carborundum dust showed a definite accentuation of the linear markings.
Dr. Watt: Stereoscopic films would show the nature of the shadow
very much better.
PROGNOSIS

AND

AFTER-GARE

Professor Hall asked Dr. Pringle if he would elaborate the statements
made in his paper (page 583) that " the amount of dust a patient may
have and the degree of tubercular infection do influence prognosis,
it is true; but I hold that the factor of individual resistance to tubercular disease is very great " and " the non-miner with pulmonary tuberculosis stands no better chance than a miner with silicosis complicated
with tuberculosis". He would have thought tuberculosis complicated
with silicosis had a very much diminished chance of recovery.
Dr. Pringle: The second statement quoted was qualified by the
words " but in some of these cases the illness probably was contracted
earlier in life ". Non-miners seemed to die as early as miners. Where
the patient was originally certified as in the ante-primary, primary or
secondary stage of silicosis, silicosis did not seem to influence the period
of life; it seemed to depend entirely on individual resistance to secondary (tubercular) infection. There were patients at the Springkell
Sanatorium between sixty and seventy years old, which showed that
individual resistance to tuberculosis was a considerable factor.
The Chairman: The figures of the Medical Bureau showed that
silicosis with active tuberculosis at the outset led to earlier death than
simple tuberculosis. The average silicotic had a much longer expectation of life. Infective silicosis meant not necessarily active tuberculosis but a chronic condition of tuberculous infection with silicosis,
sometimes arrested, sometimes progressing. There were two legal
groups: (1) silicosis which was predominantly simple or " partly infective " unaccompanied by obvious active tuberculosis, and (2) silicosis
with obvious active tuberculosis. Dr. Pringle's remarks evidently
referred to the second group.
Sir Spencer Lister : Dr. Pringle and the Medical Bureau's views seemed
to be in conflict.
Dr. Orenstein: In his opinion the probability of survival of nonminers with tuberculosis was no better than for miners with silicosis and
tuberculosis; the factor of age distribution entered largely into the
picture; greater age meant greater survival, and miners were generally
older than non-miners.
The Chairman: He agreed. Dust phthisis was a disease of later
life than was tuberculosis, because of the fact that time was necessary
for the predisposing condition of silicosis to develop.
Dr. Pringle: A large number of miners were certified as suffering
from tuberculosis, but the tubercular element did not seem very active.
Dr. Badham: If silicosis and overt tuberculosis developed together
the prognosis was very unfavourable. He asked whether Dr. Pringle
referred to that type or to silicosis with a later development of tuberculosis. The expectation of life in these two groups was quite distinct.
Dr. Pringle : Cases were sent to Springkell by the Bureau as suffering
from silicosis with tuberculosis, but the certificate did not distinguish

REPORT OF PROCEEDINGS

between chronic and active tuberculosis. The case in which the
tuberculosis factor was not very active and the sputum negative tended
to live a long time while the second type lived only a short time.
The Chairman: The Bureau's report showed that the maximum
mortality for tuberculosis with silicosis fell between forty and fifty
years of age. The numbers of deaths" from tuberculosis in each year
subsequent to the year of detection was fairly equally distributed.
Dr. Simson: In tuberculosis with silicosis the organism was living on
a medium composed mainly of fibrous tissue which was not very nutritious as compared with the other type which was living outside the
silicotic nodule.
Dr. Middlelon : The age incidence of the disease was a very important
factor. There were two crests in tuberculosis in the adult: (1) between
twenty-five and thirty-five, and (2) between forty-five and fifty-five
years of age. In the first group there was progressive tuberculosis
with acute phenomena while the second group was remarkably free
from these phenomena and the disease was much more chronic.
Active tuberculous foci outside the fibrous nodules tended to march
alongside silicosis. Silicosis with tuberculosis improved with hospital
treatment but there was a tendency to relapse later.
Dr. Böhme: Silicosis with overt tuberculosis in rock drillers generally went faster than tuberculosis alone. Most of the cases which
he had seen were between 40 and 50 years of age.
The Chairman : The amount of fibrosis in the lung was a very important factor. Once a tuberculous infection had become manifest, the
old type of silicosis progressed very rapidly, while the infective cases
to-day ran a more chronic course.
Dr. Orenstein: The attempt to correlate the evidence statistically
had shown the age distribution among miners to have shifted enormously during the last few years.
Dr. Russell : In the granite industry two types of tuberculosis occurred :
(1) between the ages of twenty-four and thirty-eight which responded
fairly well to sanatorium treatment, and (2) after twenty-five years'
exposure to dust at an average age of forty-nine years; in this group
the tuberculosis had a greater tendency to pulmonary haemorrhages
and the course of the disease was unaffected by sanatorium treatment.
The type of tuberculosis which did not respond to sanatorium treatment
was also found among silicotic potters.
Dr. Gardner: He had carried out experiments on the same kind
of animals of the same age and with the same doses. In the first experiment the infection was coincident with the exposure to dust. After
three months the infection spread, ran a sub-acute course and ended
in death from acute and chronic tuberculosis. In the second experiment
the animal was exposed to quartz dust when tuberculosis had already
been established. In this case there was a much greater tendency
to fibrosis. In the third case silicosis preceded the tuberculosis infection.
A very active tuberculosis was produced which in the majority of
cases ended in death within 60 days.
Dr. Watt: The racial factor was also very important. The mining
population had been drawn first from the densely populated areas of
Great Britain and secondly from the country population of the Rand.
The Bureau's examinations were so strict that the mining population

EIGHTH SITTING

was now A 1. He had seen cases improve under sanatorium treatment, but ultimately the end came rapidly.
The Chairman: There was a slightly higher rate of progress among
South African miners as compared with miners from overseas. Seventy
per cent, of the silicosis cases were among the old Rand miners, and
only 8 per cent, among the new Rand miners. The new Rand miners
produced as little pure tuberculosis as the Royal Air Force. The present
mining population was over 70 per cent. South African.
Dr. George: The Broken Hill statistics showed that in 1920: (1) 102
miners were withdrawn with silicosis with tuberculosis, and (2) 107
miners were withdrawn with uncomplicated tuberculosis. Of the first
group only 15 were now alive, while 55 were alive in the second group.
The average age of death from tuberculosis in the first group was 49.7
and in the second group 45.5. The average age of those still alive in the
first group was 53.5 and 54.5 in the second group. He asked what
percentage of Rand miners who obtained certificates actually got work.
The Chairman: All comers on the Rand were eligible for initial
examination and some of these came up year after year. The actual
number of examinees was at least 16,000. The new Rand miners who
entered upon their fifth year of work did not amount to more than
50 per cent, of those of that group who had started work underground.
Dr. Cunningham : We would like to hear the opinion of the Conference
on the subject of sending men compulsorily to sanatoria.
The Chairman: There was no compulsion in South Africa and there
was no systematic feeding of the sanatorium. A tuberculosis dispensary
had been established in Johannesburg, but it was closed down because
so little use was made of it.
Mr. Spence Fraser: Dr. Pringle's statement was based on the fact
that cases of silicosis with tuberculosis died at a later age than cases
of uncomplicated tuberculosis. This, however, was to be expected,
since they contracted the disease at a later age. In order to measure
the rate of progression it was necessary to calculate the average time
from the detection of the disease until death. Table IV in Dr. Pringle's
paper appeared to show that the rates of mortality among non-miners
were rather lower. He did not think that any case had been made
out to show that non-miners had a shorter lifetime.
Dr. Orenstein: Statisticians and medical men were unable to draw
any conclusion from vital statistics unless they could use them biometrically. Table IV had no particular meaning because it was not carried
to finality. Owing to lack of data it was impossible to reach comparative figures of deaths from tuberculosis in the general population and
the mining population. The economic factor had also to be considered,
since the economic conditions in which the men found themselves
before the disease might not be the same as when they had lost their
employment owing to the disease. Statistics were available to show
that the higher class of officials did not progress so rapidly as the
ordinary worker. It was also necessary to measure the rôle played
by physical and racial selection, which was becoming increasingly
important; in that should also be included the role played by individual
resistance to tuberculosis, which differed racially and individually.
In 1918 to 1919, 9.6 per cent, of European underground workers had
been employed ten years or more ; in 1925 to 1926, 36 per cent, had been
employed ten years or more. In 1918 to 1919, the silicosis peak occurred

REPORT OF PROCEEDINGS

at nine years, while in 1925 to 1926 it occurred at twelve years. It was
of the utmost importance to have a biometrie examination made of
the material in order to discover whether miners' phthisis had been
reduced or not.
Dr. Koelsch: The problem of the connection between tuberculosis and
silicosis and of prognosis was very difficult and depended on numerous
subsidiary factors—for instance that of early or late tubercular infection,
of the spread of localised tuberculosis, of individual susceptibility, etc.
By means of very extensive statistical investigation it was possible to
gain some ideas on the subject. He had analysed the relative morbidity
and mortality returns for well over 100,000 workers in dusty trades
and compared them with similar figures for the local population. He was
able to establish two critical periods:
The first at the age of about 20-25 years (= 5-10 yrs. of employment).
The second at the age of about 45-55 yrs. (= 30-40 yrs. of employment).
In the first group they had irritation due to dust and tuberculosis
which causes death relatively rapidly. Amongst those of the second
group conditions depend to a certain extent on the trend of dust—that
is, on the silica content of the dust: amongst sandstone workers, for
instance, there occurred severe tuberculosis with silicosis which relatively
rapidly becomes fatal, while in the case of pottery workers for instance
the disease followed a more protracted course.
In regard to sanatorium treatment he had not very much faith in it.
As long as the workers remained in the sanatorium they were well,
but as soon as they returned to work in a dusty atmosphere they went
from bad to worse. The insurance society, therefore, undertakes, in
the case of sandstone workers for instance, the application of sanatorium
treatment only when the patient gives a written assurance that he
will exchange his occupation for work in a dust-free industry.
Dr. George: In 1922 and 1923, thirty-four ex-Broken Hill miners
suffering from uncomplicated silicosis were placed on irrigation blocks
at Griffith, New South Wales. These blocks were situated on virgin
country, they cleared the land, erected their dwelling houses with
new timber and lived there with their wives and families. Compensation was paid throughout fortnightly, and advances of money and
material were made by the Irrigation Commission. Grapes, apricots
and citrus fruits were grown, the former two for sale after drying. The
climate wa< cold, 2,000 feet high and in winter rather damp and the
work necessitated fairly frequent work in wet conditions. The men
were told that as they had no incapacity they would make a success
of their new lives and were eager to take up the work. The men sent
were selected after a special medical examination to ensure that they
were suitable for the work. Almost from the commencement the scheme
was a failure. The men could not stand up to the harder work—
ploughing, hoeing, etc.—and soon several men abandoned their farms.
Up to the present, of these 34 men 17 had developed or died of pulmonary tuberculosis, 1 had died of sudden cardiac failure and 1 of cerebral
haemorrhage. There were about 9 of the men still on their farms,
some of whom have definite tuberculosis. They owe sums varying
from £2,000 to £3,000 on their farms. Repayments are due, but they are
able only to keep going by using their fortnightly compensation payments
to pay labourers to do the hard work. He had re-examined these
men once yearly and was convinced that the symptoms of which they
complain—dyspnoea on exertion, precordial pain, palpitations, etc.—•
are genuine and that the miner with fully developed silicosis has a

EIGHTH SITTING

definite disability for work of this nature. At the age of forty to
forty-five a man who has been a miner all his life is unsuited to take
up entirely different work which is entirely new to him. He is too old to
educate different work muscles and in the attempt to do so develops
fairly quickly symptoms and signs of cardiac strain. As the majority of
these men have young families, from the point of view of their children
no doubt this scheme justified itself to some extent.
Dr. Pringle : The experience at Springkell and Wedge Farm Sanatoria
corroborated Dr. George's experience. Men certified as silicotics would
not and could not do agricultural work. It was suggested that there
was nothing to be gained by warning men to leave the mines because
men who did so and received lump sum compensation, although excluded
from the scheduled mines, could find employment in Rhodesia and in
the asbestos mines in Barberton and elsewhere. He asked whether
any special hospital provision was made for silicotics in other countries.
Dr. Middleton: No special provision was made for silicosis in Great
Britain, but silicotics with tuberculosis were eligible for sanatorium
treatment under the National Health Insurance Act.
Professor Hall: When considering the factor of economic conditions
it might be taken into account that managers and other officials were
perhaps less exposed to dust.
The Chairman : After a man had received a notification that he was
silicotic he forfeited the right to any increase in compensation if he
did not leave work within three months; but the number of silicotics
who did not leave underground work was small. They progressed no
worse than the men who did leave, but they were of a robust type and
the majority were mine officials with better economic conditions and
less exposed to dust. The Medical Bureau believed that men who
continued underground work would be prejudicially affected, but only
about 25 per cent.
Mr. Du Toit: The Miners' Phthisis Board had tried to make comparisons between silicotics established in the Cape Province as compared
with silicotics at 6,000 feet altitude in the Transvaal. The Cape silicotics
had not been able to remain long and had had to return to a higher altitude.
The Transvaal silicotics, owing to the difficulties of the work and the
extreme cold in winter, were not able to last long on a farm. These
men nevertheless had originally come from rural districts. In both
groups silicosis had progressed. About £3,000 per man had been
expended unsuccessfully.
Dr. Russell: The experience with granite workers in the United
States had been similar. The North Italians who had migrated to
California to take up grape farming had failed and other granite workers
had also failed at farming. They were unable to adjust themselves
to new occupations.
Dr. Orenstein asked whether there was any other organisation
elsewhere in the world established by private industry comparable
to the South African institutions for the care of miners' phthisis cases.
Professor Böhme: Miners suffering from tuberculosis or tuberculosis
and silicosis in Germany have for years back been treated in the phthisis
hospitals of the Miners' Association (Knappschaftsverein). This Association is an insurance society against illness, invalidity and old age.
The cost of insurance is borne partly by the employers and partly by
the miners. Tuberculosis occurring in other occupations is treated at

REPORT OF PROCEEDINGS

the expense of the district insurance societies (Landesversicherungsanstalten). The expenses of this society are likewise borne partly by
the employers and partly by the exployees.
Professor Hall asked what was the effect of silicosis and tuberculosis
on natives.
Dr. Orenstein: The incidence of silicosis, simple or not, on natives
was relatively low, but it should be remembered that the mines
population changed 100 per cent, per annum. The recorded mortality
of 8 per cent, was much exaggerated and it could be assumed that
intermittent employment gave considerable protection. Natives were
more susceptible to tuberculosis, but racial immunity was being rapidly
acquired.
The Chairman: Simple silicosis had been shown by radiographic
examination to be much less frequent among natives, but the comparative incidence as between Europeans and natives was much the same,
given similar conditions.
Dr. Watt: The natives did not breathe through their mouths and,
therefore, were protected by a better filter than Europeans.
STATISTICS OF SILICOSIS

The Chairman: The figures showed that silicosis was definitely on
the decline, especially among the new Rand miners.
Dr. Orenstein: Without casting any reflection upon the statistical
work being done, it must be realised that it was very difficult to visualise
all the factors without biological and engineering knowledge. The present
statistics were perfectly reliable, but did not reflect the whole picture.
It was impossible to say whether the real production of silicosis was
more or less than that shown by the figures. Improved radiological
technique was now more important than clinical diagnosis, and more
diagnoses were now made.
He suggested that the money now set aside for compensating cases
of the disease might be better spent upon rehabilitation methods. A pension for a disease which tended to progress might not be doing full
justice to a man. South Africa spent about £800,000 a year on compensation and there were liabilities of £9,000,000. Under the present
system in the ante-primary stage of silicosis a man was penalised if
he did not leave the mine at once, and about £500 was given to a man
thus thrown out of employment. He thought it might be better to
wait until a marked degree of incapacity was reached and that search
should be made for other avenues of employment. The farming experiments had not perhaps been efficiently conducted. There was
room here for further investigation and research.
Professor Hall: The statistics of South Africa were so unique and
of such importance to all countries which had to initiate legislation
and compensation, that every step should be taken to make them as
clear as possible. Biometrical statistics involved many other factors
and it was desirable that all the material should be handled by the
greatest biometrician obtainable.
Mr. Spence Fraser : A biometrician might obtain valuable results
from the statistics, but it was very difficult to obtain an all-round man ;
a mixed Committee might perhaps be necessary. It was doubtful if
the data existed to enable a biometrician to produce useful results.

EIGHTH SITTING

If compensation for ante-primary silicosis had existed from the
beginning the figures to-day would appear better to-day because more
miners would have been excluded from employment in the earlier years.
The duration of work was shown in the statistics as the main factor. The
age figures published by the Bureau showed that the factor of age was
of little importance; it did not, for example, affect mortality in the
secondary stage. The ante-primary stage had not been constant
owing to improved technique and other factors, and the production
rate had consequently increased for some years, though that had been
foreseen. The liability of the miner differed greatly according to the
character of his occupation, but for purposes of compensation no
distinction was made between the various occupations. The proportion
of miners in the different occupations had not, however, changed to any
marked extent. He thought that the statements in his and Dr. Irvine's
paper of the decrease of production was a fair statement of the conditions.
Professor Kettle : The statistics were beyond criticism, but he hoped
that a biometrician could carry out the widest possible survey.
Dr. Mavrogordato: Two factors were at work: (1) the change from
a migratory to a fixed population, and (2) improvement in conditions,
in which must be included the initial examination. He believed that
as much ante-primary silicosis was made as ever, but it now took
thirteen years instead of eight to nine years. This was probably due
in part to selection of miners and the production rate would fall as the
number of picked men increased. If the time taken to produce a
clinical silicosis could be pushed up to twenty years silicosis could be
considered as eliminated on the Rand from the social point of view.
The Chairman; From 1912 to 1916 compensation was awarded to
men at quite as early a stage as at present. A large class of the miners
now detected had begun work about 1912 and 1914. Diagnosis was'
based on the correlation of radiological and clinical evidence with
the post mortem, and improved radiological technique alone could
not, therefore, upset the balance. 256 cases were detected in 1930 as
against 800 to 900 cases in 1912 to 1916. He did not believe as many
ante-primary cases were now being made. The old Rand miners still
accounted for 70 per cent, of the silicosis, but there was an improvement
in the value of their production rates of 30 per cent. He did not agree
that as much silicosis was made as ever but taking longer. Nor did he
consider that the potentialities of their present methods had been
exhausted.
Mr. Spence Fraser: The number of ante-primary cases last year
was the same as the average for 1920 to 1923. The rates had decreased,
which meant that the duration of working life was much greater, and
that a larger number of miners got silicosis in later years. The mining
population was much steadier and although there was the same number
of cases the production of them was deferred. He thought that an
improvement could be deduced from the figures given in his. and
Dr. Irvine's paper.
(The Conference adjourned at 1 p.m.)

REPORT OF PROCEEDINGS

NINTH

SITTING

Wednesday, 20 August 1930, 2.30 p.m.
Chairman:

DR. L. G. IRVINE

Dr. Mavrogordato showed lantern slides illustrating silicosis and
tuberculosis in guinea-pigs and human beings.
STATISTICS OF SILICOSIS

(continued)

Mr. Spence Fraser: The method of measuring silicosis production
could be compared with the method of measuring mortality in a
population. In the latter case the rate of mortality at any age was
derived by comparing the deaths at that age with the population living
at that age. In dealing with silicosis the number of miners working
in each respective year of underground service was substituted for
the population existing at each age, and certifications in the anteprimary stage were substituted for deaths. The methods were analogous.
If the rates of mortality in a population were lower in any period than
during a previous period, it was recognised that the mortality had
fallen and that there had been an improvement in the position. In
the same way, they found in South Africa that the rates of production
of silicosis were lower to-day than at any previous period, and they
had no hesitation in saying that the position had improved.
It was true that the annual number of new cases of silicosis to-day
was about the same as in 1920-1923. A similar phenomenon was found
in mortality statistics; the death rates could decrease, while the total
number of deaths actually increased, because there was a different agedistribution of the population, many more being alive at old ages where
the death rates were highest. The same thing had happened with
regard to silicosis, since there had been a large increase in the number
of miners working after long periods of underground service where
the rates of production were highest. The true measure of the production
of silicosis lay in the production rates showing the proportion of miners
contracting silicosis in each year of underground service, and these rates
showed a very substantial reduction in the incidence of silicosis.
Dr. Orenstein : The discussion had shown that the statistical methods
of the Rand were not sufficient to give the facts which practical hygienists
wished to know. Professor Hall's resolution aimed at closer and more
detailed study in order to find out which factor contributed most to
reduction. The present statistics did not give the fundamental data
and he was not satisfied that they demonstrated a reduction in silicosis.
Dr. Cunningham requested information as to the number of cases of
ante-primary silicosis among miners employed since the beginning of
rigid initial examination, in whom tuberculosis had developed. If the
numbers were large enough it might give some indication of the value
of the initial physical examination.
The Chairman: Professor Hall's motion would be referred to the
reporters.

NINTH SITTING

LEGISLATION

AND COMPENSATION

The Chairman: South African legislation had the peculiarity that :
(1) the duration of time to render a miner eligible for a claim was
very elastic; it was two years, with the reservation that the Board
might allow a shorter period to count; (2) there was no restriction as
to the date when the work had been carried out; (3) there was no restriction as to the amount of work done in other mines in South Africa
or elsewhere before or after the work on the Reef.
Cases of ante-primary and primary silicosis received lump sum compensation, while grave incapacity or tuberculosis was pensionable. The anteprimary cases sometimes had disability up to 25 per cent. Primary
cases could do moderate physical work and the secondary cases light
work or none.
Dr. Middleton: While South African legislation made no provision
for suspension in the early stage, under certain schemes in Great Britain
any degree of silicosis was liable to immediate and total suspension,
whether there was disablement or not. He asked, however, if this was
justified or whether suspension would arrest the development of the
disease. In some highly skilled industries, provision was made under
special schemes to allow men with more than twenty years' work, or
who were over forty years of age, to remain at work ; this was done for
economic reasons. The special schemes for silicosis were not all the same.
Under the Refractories Industries and Sandstone Industry Scheme
there were periodical examinations with compensation for partial or total
disability or for death. Under the other schemes there was no periodical
medical examination, but they followed the procedure under the Workmen's Compensation Act for occupational diseases, though they covered
only total disablement or death, owing to the difficulty of recognising
the disease in the earlier stages.
The Chairman: The ante-primary stage had been introduced in
1919 to secure the suspension of silicotic workers, at the earliest detectable stage of the disease in the hope that such cases would be nonprogressive. That hope had not been realised. It was impossible to
say that ante-primary cases would not progress; although they lived
longer they reached the second stage faster than did the old primary cases.
Dr. Truter: Suspension from work lowered the worker's standard
of living, and he therefore deteriorated more rapidly. A miner who
continued to work lived as long or even longer.
Dr. Orenstein : Other employment could be found in an industrialised
country but was impossible in South Africa. The ante-primary man had
to choose between continuing at work with no increased compensation
and receiving a lump sum (about £500) and finding other employment,
which was difficult to discover at a wage equivalent to that gained by
a miner. Their economic status was therefore lowered. He asked
whether compensation really discharged the onus which lay upon
society and whether the expenditure on compensation was applied to
the best advantage.
Dr Badham: He hoped the Reporters would frame resolutions to
give guidance on the framing of compensation legislation.
Professor Hall: No single line of legislation or compensation could
apply to all classes. In Great Britain, if there was no trade depression,
a suspended man was able to find equivalent employment in some
6

REPORT OF PROCEEDINGS

other trade. Cases in the ante-primary stage which had been followed
up had been able to carry on at work for five years. Skilled workers
such as potters who had primary silicosis, with some degree of incapacity,
were capable of doing their full work. Potters could not be treated in
the same way because if they were suspended they could not find other
work which was economically as good.
Mr. Du Toit: A number of South Africans had worked underground
for two years or less in the scheduled mines and had subsequently been
engaged in agricultural work. These men had never been out of South
Africa and subsequent to their underground service in the gold mines
had never done any other underground work, but nevertheless developed
silicosis. For this reason the elastic period of two years' underground
service, referred to by the Chairman, had been introduced in South
African legislation. These men obviously had to be compensated. A
number of men who had previously been miners in South Africa
had during the past five years benefited under the South African Miners'
Phthisis Act. These men had also done mining work elsewhere. It
was an exceedingly difficult matter definitely to say where the disease
had actually been developed. Then again, numbers of silicotic beneficiaries had left South Africa and had entered other mines and dusty
occupations outside the Union of South Africa.
Silicosis had been found in men who worked in the Cornish tin mines,
in the Welsh coal mines, the Cumberland iron ore mines, mines in Canada,
in Australia and New Zealand. Miners and beneficiaries who had been
employed there should have no claim on the funds of South Africa.
Attempts were now being made to restrict South African ex-miners
and beneficiaries under the Act who had subsequently engaged in
mining work elsewhere from having any claim for compensation or
further compensation, as the case might be, on South African Funds.
In regard to the question of rehabilitation, this was a most difficult
matter because South Africa was a young country with few industries
and it was not easy to find other employment for silicotic beneficiaries.
South Africa was not essentially a great agricultural country in spite
of what people might say. It was highly mineralised, and base metal
mines absorbed a certain number of silicotics.
Then there was another important factor in South Africa with which
other older countries had not to contend, namely, the enormous native
and coloured population. This also made it very difficult to draft
silicotics into other suitable occupations. It was impossible for silicotics
to make good on the land as agriculturists since they could not stand
exposure to all kinds of weather. He believed this had also been the experience in Australia, Canada, the United States and the United Kingdom.
Road construction was also unsuitable. Asbestos mining was now
known to be fatal and, in South Africa at all events there were very
few other outside mines which could absorb all their silicotics. On the
one hand, if silicotics were allowed to remain in their underground
occupations without any restrictions, the position might be reached
after a period of years when the gold mining industry would be entirely
run by employees who were silicotics and this in the end was bound to
affect efficiency. On the other hand, no State could be expected to
legalise what amounted to slow suicide.
If continued employment underground was not dangerous to silicotics,
then the South African legislation should be altered, but in the absence
of reliable data there was no conclusive evidence either one way or the
other.

NINTH SITTING

A large number of South African silicotics had been placed in other
suitable employment, but such employment was not always of a permanent
nature. Then there were some beneficiaries who were unemployable.
This class one naturally found in all sections of the community; it
was a class which might be ruled out as not fit for employment. This
class the South African Legislation never intended should be given
employment unless of a very light nature and it consisted of men in
the worst stage of silicosis or suffering from silicosis with tuberculosis.
Beneficiaries belonging to this class were in receipt of monthly life
pensions with inclusive allowances for their wives and children. After
the death of a life pensioner no post-mortem or certificate as to the
cause of death was required. The dependants were entitled to life
pensions ipso jacio.
Dr. Fisher: Alternative employment was impossible for coal miners.
Colliers lived in small villages, and if they were unemployed their condition tended to become worse in a general way, as miners' nystagmus
had shown, although of course neurasthenia was not part of silicosis
as it was in miners' nystagmus. Light employment such as repairs on
the main haulage roads at an agreed standard living wage was desirable.
Dr. George: At Broken Hill the medical authority was a Board
which consisted of an independent chairman appointed by the Government, one doctor appointed by the employers, and one doctor by the
workers. Medical benefits were given for pneumonoconiosis and/or
tuberculosis up to £125 per man. The Act was administered by a joint
committee, two of whom were appointed by the workers and two by
the employers, with an independent chairman, who was usually a
stipendiary magistrate (a Government official). This committee had
no power to interfere with the medical certificates. The condition of
the miner had to be certified as reasonably attributable to employment
in the Broken Hill mines. They were withdrawn in the ante-primary
stage, but the Committee had to find work for them. Up to the present
it had never yet been done, and silicotics therefore drew a full pension
in many cases with no incapacity. At Broken Hill in case of death
from any cause whatsoever the widow received a pension of £2 10s. a
week, and children under the age of sixteen of 8s. 6d. per week.
At the start many men had not sustained injury from Broken Hill
and the State therefore contributed half the amount, and the employers
the other half. When injury was attributable to Broken Hill, the
employer found the whole sum. Upon leaving the industry a man
had to be examined by the Medical Bureau, and he could come up for
examination at any time within the five years following.
Dr. Badham: In New South Wales there were three Acts, namely:
(1) the Broken Hill Act which dealt with a special mining district; (2) the
Workmen's Compensation (Silicosis) Act, which dealt with Sydney
sandstone workers—a beneficiary might receive a maximum of £3
a week up to a total of £750, but there was no payment to dependants
except in case of death; (3) the Workmen's Compensation Act (1926),
which granted compensation for fibrous pneumonoconiosis except at
Broken Hill, with amaximumof£5 a weekupto a total of £1,000. Diseases
caused by silica dust were however excluded and despite the three Acts in
New South Wales dealing with compensation for dust diseases of the
lungs there was still a number of workers who were not protected.
Dr. Moore:
In Queensland the Workmen's Compensation Act
covered pneumonoconiosis and silicosis. In Victoria and South Australia

REPORT OF PROCEEDINGS

silicosis was not included. In Tasmania, a few shillings a week were
paid for silicosis. In Western Australia the Miners' Phthisis Act
excluded tuberculosis or silicotic men from employment in the mines,
but granted no compensation for silicosis. The Commonwealth
Government paid a pension of £1 per week for total incapacity.
Dr. Cunningham:
Disability and expense might be reduced if it
were possible in industries in which silicosis develops rapidly, to remove
men from exposure to silica without waiting for specific indications of
silicosis and therefore without compensation, at some unknown point
before the ante-primary stage is reached.
It would be worth a considerable expenditure to determine when
tuberculosis becomes a more serious menace in a lung containing silica.
A reduction of two or three years below the average exposure necessary
for the development of silicosis would not materially increase labour
turnover.
Mr. Barry: Silicosis in South Africa had given rise to nine Acts,
four commissions, and many select committees. The average amount
of compensation paid to a married man was £3,500. Up to October
1929, 7,633 beneficiary miners were alive; 2,271 of these were in the
ante-primary stage, 2,306 in the primary stage, and 2,184 in the secondary stage. There were 2,014 widows and 3,538 children in receipt of
pensions.
All this legislation was unfortunately retrospective, and it laid a
heavy burden on employers, since many mines had shut down, and paid
no retrospective compensation. The legislation contained anomalies
such as the semi-compulsion upon a miner to give up underground
work, but the lack of any regulation to prevent him taking up mine
work elsewhere. Any miner who had been employed two years
underground could work in another silicotic occupation and yet receive
benefits. Two years' service at any date counted.
It was generally agreed that underground conditions had enormously
improved in the last twenty years. The working life which had once
been seven or eight years was now twenty years. The new Rand miner
had a working life of about twenty-three years, notwithstanding which
claims upon the Fund had increased. This was said to be due to the
large number of old Rand miners, and to improved methods of diagnosis
which kept the cases lower. It was also said, however, that the disease
had become more progressive.
Under the Act of 1919 some mines closed down and were compelled
to pay only a small portion of their liabilities. The Board collected
about £1,000,000, all of which was given to old cases under the 1925
Act. The real cost of miners' phthisis was said to be £1,000,000 per
year. The Government Actuary estimated the outstanding liability
of the mines at £6,400,000.
When the 1925 Act was passed provision was made for each mine
to set aside a sum annually to meet these liabilities. The cost to the
mines of miners' phthisis was 7s. 6d. per underground European shift.
The South African Act was the most liberal in the world, and the only
Act that could be compared with it was in Ontario, where £100 was
paid for ante-primary silicosis, £200 for primary silicosis and a
pension of about £15 per month. It was impossible to alter the South
African legislation without upheaval, because any new benefits granted
produced thousands of retrospective claimants.
The Chairman:
In South Africa there was no general national
insurance Act for invalidity, and there was therefore a tendency to

TENTH SITTING

treat the Miners' Phthisis Act as a kind of substitute for the Poor
Laws. The question of compensation for simple tuberculosis might
be referred to the Reporters. The cases which the Medical Bureau
had certified as " simple tuberculosis " and which came to post-mortem
were found in 50 per cent, of the cases to have a silicotic element. It
was also desirable to remove simple tuberculosis cases from the mines,
because of the risk of communication of infection to others.
Mr. Du Toit : The question whether compensation should be computed
on a wage basis or on a flat rate should be referred to the Reporters.
Dr. Orenstein: Legislation had to differ according to the industrial
conditions of various countries. The South African situation was quite
peculiar, because the gold industry was not subject to the fluctuations
of other industries, but was handicapped by the mental attitude of
legislators to gold. The legislation on pneumonoconiosis was extraordinarily illogical. The Reporters might consider whether any standard
conditions could be applied to this disease throughout the world. Great
weight was given in legislation to the necessity of fixing compensation
for silicosis sufficiently high to stimulate prophylactic measures. The
Reporters might consider whether silicosis could be called preventable.
It was a misconception that removal from work in the earliest possible
stage would prevent further development; if it was true that continued
employment was really slow suicide, no man should be allowed to
work in any dusty occupation at all. He proposed the following resolutions :
1. That endeavour should be made to deal with silicotics by
rehabilitation, diverting for that purpose a portion of the funds
made available under present conditions for compensation. Such
rehabilitation schemes to be directed by specially constituted
governing bodies.
2. That there appears to be reason to consider that there are
no good grounds for compulsory removal of silicotics from their
customary employment, unless such removal does not tend to
lower markedly the economic level of livelihood of the silicotic
or until his earning power has reached the level approximating
that of the compensation.
3. That removal from employment of men in the fifth and
sixth decades of life is generally inadvisable, until a high degree
of incapacity is present.
(The Conference adjourned at 4.50 p.m.)

TENTH

SITTING

Saturday, 23 August 1930, 9.30 a.m.
Chairman:
DRAFT

REPORT

DR. L. G. IRVINE
ON PREVENTIVE

MEASURES

The Conference considered the Draft Report on Preventive Measures
and adopted it with the exception of Recommendation 4, after making
various amendments.
(The Conference adjourned at 1.35 p.m.)

REPORT OF PROCEEDINGS

ELEVENTH

SITTING

Monday, 25 August 1930, 9.30 a.m.
Chairmen:

SIR SPENCER LISTER

(Vice-Chairman) and

DR.

L. G.

IRVINE

ARRANGEMENTS OF BUSINESS

Mr. Phelan proposed that the closing sitting of the Conference on
Wednesday, 27 August, should be open to the Press after a certain
hour, and that the recommendations adopted by the Conference should
be communicated to the Press.
The Conference approved of this procedure.
T H E MEDICAL ASPECTS OF SILICOSIS

The Conference proceeded to discuss the Report upon the Medical
Aspects of Silicosis, including /Etiology, Pathology and Diagnostics,
submitted by Drs. Gardner, Middleton and Orenstein. The Report was
as follows:
The Reporters, Drs. L. U. Gardner, E. L. Middleton and A. J.
Orenstein 1 , beg to submit the following:
1. The Conference confined its discussion almost entirely to silicosis,
as the other pneumonoconioses are, with the possible exception of
asbestosis, in the present state of available information, of less importance,
and furthermore have not been subjected to sufficiently detailed study.
2. Silicosis is a pathological condition of the lungs due to inhalation
of silicon dioxide. It can be produced experimentally in animals.
3. To produce the pathological condition, silica must reach the
lungs:
(a) in a chemically uncombined condition, although the dust
inhaled may be either a natural mixture of silicon dioxide with
other dusts, such as occurs in granite, or an artificial mixture,
such as scouring powder;
(b) in fine particles of the order of less than ten microns. There
is no evidence as to the lowest limit of size in which the particles
may be capable of producing the disease;
(c) in sufficient amount, and over a certain period of time; these
two factors are reciprocal variants. The minimum of these
two respective factors has not yet been determined.
4. Silica dust plays the dominant role in the production of silicosis,
admixture of other dusts tending to modify the picture in the direction
of that of other pneumonoconioses, in some relation to the proportion
of free silica inhaled.
5. There is experimental evidence that the solubility of silica in
the tissues is an essential factor in the causation of silicosis.
1
Dr. W. Steuart was unable to participate in the preparation of this report.
He submitted a memorandum which is reproduced later as an Appendix.

ELEVENTH SITTING

6. Infection of the lung with B. tuberculosis or other pathogenic
organisms, whether it occurs before, simultaneously with, or subsequent
to the development of silicosis, alters the disease and influences it
unfavourably, tuberculous infection being particularly unfavourable.
7. The establishment of a silicotic process in a lung renders the
subsequent inhalation of other dusts, in themselves relatively innocuous,
capable of producing serious pneumonoconiosis.
8. It was suggested that intermittency of employment retards the
onset of silicosis, but the evidence adduced in support of this, though
suggestive is not conclusive, when the total period of exposure is not
affected.
9. It was agreed that the microscopic pathological changes which
may be produced by the prolonged inhalation of silica dust are:
(a) The development of a condition designated in South Africa as
a dry bronchiolitis, characterised by an accumulation of dust
filled phagocytes in or in relation to the terminal bronchioles,
with possibly some desquamation of their epithelium.
{b) The accumulation of dust-containing phagocytes about and
in the intra-pulmonary lymphoid tissue, and their transportation through the lymphatics into the tracheo-bronchial lymph
nodes.
(The conditions described above under (a) and (b) do not constitute the disease silicosis.)
(c) The gradual development of fibrous tissue within such accumulations of phagocytes and the formation of characteristic nodules
of hyaline fibrous tissue.
(d) Degenerative changes in these foci.
(e) The hyaline nodules increase in size by extension at their
periphery.
Coalescence of adjacent nodules takes place and brings about
involvement of further areas of the lung.
(The conditions described under (c), (d) and (e) constitute the
disease silicosis.)
10. Macroscopically the changes observed in silicosis are:
(a) In the early stage. A variable number of palpable pearly-white
nodules up to 2 or 3 mm. in diameter on the pleural surface
of the lung. On section, the cut surface of the lung is studded
with pigmented foci, widely scattered, a moderate proportion
of which are only just palpable. The tracheo-bronchial lymph
nodes are slightly enlarged and deeply pigmented, and may
exhibit foci of fibrous induration.
(b) Later stages. The fibrotic nodules are increased in number,
size and density, and coalescence of these may be found. The
portion of the lung between the fibrotic nodules may be emphysematous. The tracheo-bronchial lymph nodes may be smaller
in size than those seen in the early stage and are fibrosed.
11. The presence of tuberculous infection usually modifies the
pathological appearance. Special attention was drawn to the three
following types:
(a) In which the picture of silicosis above described may be little,
if at all, modified, but in which only a biological test can
demonstrate the presence of B. tuberculosis.

REPORT OF PROCEEDINGS

(b) In which the coexistence of silicosis and typical tuberculosis
lesions is easily recognisable.
(c) In which the presence of tuberculosis is easily recognisable,
but the existence of silicosis is more difficult to determine.
12. There is evidence that with B. tuberculosis, in vitro the period
before growth becomes apparent is shortened in the presence of silica,
and that in vico an environment favourable to the continued growth
of the bacillus is produced in the presence of silica, but the virulence
apparently remains unaltered.
13. In massive silicosis cardiac hypertrophy and subsequent dilatation may occur. In silicosis with infective processes, cardiac changes
may also occur.
14. No evidence was adduced in regard to involvement of kidney
or liver.
15. For the diagnosis of silicosis as a disease it is necessary to take
into consideration:
(a) the employment history;
(b) the symptoms and physical signs;
(c) the radiological findings.
16. The disease can conveniently be divided into three stages,
designated " first ", " second ", and " third " stages.
17. In the differential diagnosis of silicosis from other pneumonoconioses a history must be established of exposure to inhalation of
silica dust in a quantity reasonably commensurate with the clinical
and radiological findings.
18. In the " first stage " symptoms referable to the respiratory
system may be either slight or even absent. Capacity for work may
be slightly impaired. There may be a departure from the normal in
percussion and in auscultatory signs, and the radiograph must show
an increased density of linear shadows, and the presence of discrete
shadows, indicative of nodulation.
19. In the " second stage ", there is an increase of the physical
signs observable in the " first stage ", and the radiograph shows an
increase in the number and size of the discrete shadows indicative of
nodulation with a tendency to their confluence. There must be some
degree of definite impairment of working capacity.
20. In the " third stage " all the above conditions are grossly
accentuated and indications of areas of massive fibrosis are usual. There
is serious or total incapacitation.
21. Pulmonary tuberculosis may be present in any of the above
described " stages " of silicosis, altering the symptoms, physical signs
and radiographic appearances, and the degree of working capacity.
Its presence must therefore influence the " stage " classification of the
individual, which classification must in these circumstances be based
more on the degree of loss of working capacity than on physical signs
and radiographic appearances.
22. Radiographs may frequently be met with which show a slight,
moderated, • or well marked increase beyond the normal in radiating
linear shadows. These may or may not be due to fibrosis.

ELEVENTH SITTING

23. The inhalation of asbestos dust produces a definite pneumonoconiosis, which may occur also in association with tuberculosis, and
deaths have been recorded.
This pneumonoconiosis is associated with the presence in the lungs
of " asbestosis bodies ", but the mere presence of these bodies in the
lungs or sputum does not constitute evidence of the disease.
For the diagnosis of this pneumonoconiosis the same criteria as
described for silicosis should be applied, mutatis mutandis.
There is not at present sufficient evidence to show definitely to what
extent tuberculosis and this type of pneumonoconiosis react upon
one another.
24. There are other dusts, such as those from marble, coal, carborundum, etc., which may contain small quantities of silica and which
produce demonstrable lung changes, radiographically resembling in
some cases the appearances observed in early silicosis.
There is not a sufficient body of evidence available to enable a definite
statement to be made of pathological changes in man. In animal
experiments, the inhalation of carborundum dust over a period of four
years has produced fibrosis only in the tracheo-bronchial lymph nodes;
the lungs were entirely free of fibrotic changes. This, and collateral
observations on inhaled granite and asbestos dusts suggest the hypothesis
that to produce pulmonary fibrosis a sufficient concentration of a
relatively insoluble dust must be brought by the activity of phagocytic
cells into intimate contact with connective tissues. With the dusts
last mentioned the migration of phagocytes, for at least a prolonged
period, is ineffective in establishing such contact in the lung. Only
in the tracheo-bronchial nodes are these conditions realised during
a period of four years.
25. The Reporters beg to recommend that appropriate action be
taken :
(a) To establish an international classification of silicosis on the
lines indicated in paragraphs 16 to 21 inclusive.
(b) To enquire into the possibility of establishing an internationally
comparable technique of radiography, and terminology of
radiographic findings.
(c) To institute further studies in the correlation of radiographic
appearances, morbid anatomy and symptomatology of silicosis
and silicosis with tuberculosis.
(d) It is desirable that further scientific research into the aetiology,
pathology and diagnosis of silicosis and other dust diseases
should be undertaken on an international basis, at an early date.
APPENDIX

Memorandum on Radiography of Silicosis
By

Dr.

STEUART

With a view to obtaining uniformity in films of the thorax in cases
of silicosis a description of the technique used at the Miners' Phthisis
Bureau is given in detail.
The transformer receives three phase current and the secondary
current is rectified by means of six valve tubes. Its output is much
in excess of the capacity of present X-ray tubes.
The X-ray tube used is a metallic DN type. The distance from
focus to film is 48 inches.

REPORT OF PROCEEDINGS

The length of exposure and penetration vary with the antero posterior
thickness of the examinee according to the following table:
Depth of thorax in inches

Time in seconds

Kilovolts

0.1
0.11
0.12
0.15
0.175
0.2
0.22
0.23
0.24
0.25
0.26
0.26

61
61
61
62
62
63
63
64
64
65
65
66

m
8
8%
9
9%
10
101/.
11
i i y2
12
12 %
F i l a m e n t current
4.3 amperes

Current through tube 200 M.A.

The man lies in the prone position on the casette with the tube
above him.
Kodak films and Agfa intensifying screens are employed. If other
makes of screens and films are preferred allowance should be made
in exposure and penetration as films and screens differ considerably
as regards speed.
Casettes are such that uniform contact between films and screens
is secured.
The developing solution is made up according to Kodak's formula,
but to every 5 gallons 4 lbs of sodium carbonate and 4 lbs of sodium
sulphide are added.
The temperature of the developer is 65° F. and the time of development is five minutes.
Terms used in indicating the diagnosis on X-ray report form:
1. Normal thorax. •—• This is taken as that of a healthy youth of
about eighteen.
The heart occupies a left medial position and is approximately
triangular in shape, its shadow accounts for about one third of the
area of the thoracic shadow. Its size and shape vary.
The right hilus is seen as a faint rather small shadow but the left
is hidden by the heart.
The diaphragm is dome shaped on each side, the right being higher
than the left. Its level is variable.
The pulmonary tissues throw no shadows so that between the ribs
the skiagram should be uniformly clear.
Radiating from each hilus faint shadows can be made out due to
the roots of the bronchial tree of bronchi vessels and supporting tissues.
The costal cartilages are transradient.
2. Rather more fibrosis than usual. — This is really the normal
thorax and is seen in healthy adults, but through the continuous
inhalation of dust, smoke, etc., the hilus and bronchial tree shadows
become accentuated, otherwise the picture is that of a normal thorax.

ELEVENTH SITTING

3. More fibrosis than usual. — This is an extension of the previous
condition. The hilus shadows are denser and the bronchial tree shadows
are more numerous and found throughout the thorax. It is seen in
old people, in cases of chronic bronchitis, asthma, and in old healed
infections. Though not an absolute bar to underground work it is
a factor that goes far in deciding the rejection of an applicant for
mining work.
Then come a series of classifications of conditions that arise from
gold mining, viz.:
4.
5.
6.

Commencing generalised fibrosis.
Moderate generalised fibrosis.
Well marked fibrosis.

Very well marked fibrosis.

8. Gross fibrosis. The commencing generalised fibrosis shows itself
on the Witwatersrand after five or more years depending on the particular work done and the idiosyncrasy of the miner. It is a further
accentuation of " more fibrosis " than usual and here and there small
pin head shadows can be made out, the first indication of the typical
" mottling " of silicosis.
Thereafter the mottling is common to all the others, the chief indication of the amount of fibrosis being the size of the nodules.
The nodule or unit of mottling varies from about one twentieth of
an inch (1.25 mm.) in diameter in moderate generalised fibrosis to
about a quarter of an inch (7 mm.) in gross fibrosis. These figures
are of course merely approximate and not absolute.
9. Fibrosis partly or mainly silicotic in type. — This is deduced
when the nodules are clearly cut in outline and uniform in distribution
throughout the lung.
10. Fibrosis partly or mainly infective in type. — A slow infective
process has the effect of increasing the size of the nodules in certain areas
so that there is no uniform distribution as in pure silicosis. The outline
of the nodules becomes fluffy instead of sharply defined. The usual
infection is tuberculous, but syphilis and other chronic infective process
may cause the same appearances.
11. Appearances suggestive of tuberculous, r-yr- lung. — A sudden
increase in the density of the hilus shadows, increased apical density
or patchy shadows in other lung areas lead to the initialing of this
item in the report.
12. Apparently definite tuberculosis, r-j~ lung. — Tuberculosis is
often so well established in periodical cases that there is practically
no doubt as to the meaning of the shadows shown. The appearance
can best be described by imagining some French chalk being thrown
on the film and then ruìbbed round with the fingers. In the shadows
produced dark areas of varying size may possibly be seen due to
cavities.
The word " apparently" is retained because occasionally syphilis
causes much the same kind of shadow.
13. Peribronchial thickening; hilus thickening. — From the experience obtained since the commencement of examining individuals

REPORT OF PROCEEDINGS

who wished to take up mining, it has been found that the accentuation
of the shadows cast by the larger branches of the bronchial tree (called
by the Bureau "Peribronchial thickening") and of the hilus shadows
is a definite indication of tuberculous susceptibility and examinees are
frequently rejected on this account.
14. Pleural thickening ^— side.
°

15.

left

Pleural effusion —- side.

Both of these conditions are readily noted by a radiographical examination and are considered important on account of their possible
association with tuberculosis.
16. Consolidation -~- side. —• This diagnosis is given in the case
of any dense shadow that does not alter its size and shape in different
positions of the subject. The causes of consolidation are so numerous
that unless there is some special indication in size, shape or position
no diagnosis is attempted except possibly a query.
17. Heart, asthenic or vertical in type. — Although the heart shadows
vary to a considerable extent within normal bounds, individuals having
a tubular shaped heart or one casting a very small shadow, are regarded
as " suspect " by the members of the Bureau for the same reasons
noted in 13, 14, and 15.
18. Heart enlarged. —• In most cases of cardiac disease and pericarditis the heart shadow usurps more than its normal share of the
thoracic space, and attention is always drawn to this variation, as
cardiac disability is often ascribed by outside medical practitioners as
being due to silicosis.
19. Aorta enlarged and aortic aneurysm. —• These items have frequently to be initialed and are often associated with patchy shadows
suggestive of tuberculosis which however disappear after a course of
appropriate treatment for specific disease.
20. Other changes, viz.:
(1) Aerophagy. —• Occasionally at the left base it will be found that
the phrenic shadow is pushed up into the thorax and that below it
a negative shadow is shown. This is due to the subject swallowing
air which distends the stomach and may cause discomfort.
(2) Aneurysm of heart. — The condition is very rare, only one case
in 80,000 persons having been noted at the Bureau.
(3) Atelectasis. — Due to obstruction of a bronchus, gives a fanshaped shadow radiating from direction of lung root which is as dense
as a consolidation shadow.
(4) Azygos lobe. —• In about one case in twenty thousand there
is an abnormal azygos vein which leads to a shadow in the upper lobe
of the right lung.
(5) Bronchiectasis. —• This is indicated in skiagrams by No. 13,
" peribronchial thickening ". A definite diagnosis however can only
be given after a lipiodol injection.
(6) Bronchitis. — Chronic bronchitis gives the picture described in
No. 3, " more fibrosis than usual ".

ELEVENTH SITTING

(7) Calcification. — Calcium is deposited in old inflammatory foci
and in costal cartilage. It is often deposited in silicotic nodules and
in lymphatic glands at the root of the lung. Its presence is indicated
by an increased density of the shadow.
(8) Carcinoma. — Carcinoma may occur as a primary or secondary
condition.
In the former case it leads to a consolidated area which increases
in size. In the latter several shadows are seen which are circular and
become larger and larger in diameter until the patient succumbs.
(9) Emphysema. — The lung tissue becomes more transradient so
that other shadows are accentuated owing to the increased contrast.
(10) Empyema. — The shadow is very dense and may occupy any
part of the lung field.
(11) Hodgkins disease. — The thoracic involvement causes a dense
mediastinal shadow.
(12) Hydatid cyst. — This is indicated by a dense oval shadow
with a uniform contour.
(13) Liver and subphrenic abscess normally occur on the right side.
The diaphragm is pushed up into the thorax.
(14) Miliary tuberculosis. — The appearance is practically the' same
as a moderate generalised fibrosis mainly silicotic in type.
(15) Pneumonia. — The shadow is dense and varies in size according
to the severity of the disease.
(16) Pneumothorax. — The collapsed lung can be seen in the root
area. It is surrounded by a uniform negative shadow stretching to
the periphery.
The Conference adopted the Report.
The Conference decided that the Memorandum submitted by Dr. Steuart
should be appended to the text of the Report.
Dr. Loriga dissented from the proposal which the Conference adopted
to describe paragraph (a) and (b) of Clause 9 as conditions which did
not constitute the disease silicosis, and paragraphs (c), (d) and (e) as
constituting the disease silicosis, on the ground that these notes should
properly be inserted in the Report on Compensation, since arbitrary
legal limits might be laid down between the various pathological stages,
while pathology must insist on the progressive nature of the evolution
of the disease and could not properly indicate hard and fast divisions
between its different stages.
The Chairman thanked the Reporters for the work which they had
so ably performed.
(The Conference adjourned at 12.45 p.m.)

REPORT OF PROCEEDINGS

TWELFTH

SITTING

Tuesday, 26 August 1930, 9.30 a.m.
Chairman: DR. L. G. IRVINE

PREVENTIVE MEASURES

The Conference considered the Revised Report of the Sub-Committee
on Preventive Measures and adopted it. The Report is given below.
The Sub-Committee, consisting of Dr. Loriga, Dr. Badham and
Mr. Roberts, appointed to deal with questions raised under this heading,
begs to report as follows:
1. The Conference dealt with the matter of prevention at its sessions
held on Friday afternoon and Saturday morning, 15 and 16 August
1930.
The first six papers and the papers presented by the visiting members,
were taken as read, and discussed on broad lines, members having
remarks to make calling freely upon their experience in regard to one
or other of the various aspects of the question.
The feeling of the Conference was that the present opportunity
should be used for an interchange of ideas with a view to mutual
inspiration which would be of value in future research, rather than
that it should be used for the purpose of arriving at conclusions and
the making of recommendations.
2. It was generally agreed that so far as the present heading is
concerned, the disease which it is sought to prevent is that which
arises from the inhalation of free silica (Si02) as distinct from silica
in chemical combination with other substances.
3. From the information supplied by various members, the disease
becomes noticeable after widely differing periods of exposure to siliceous
dust, depending apparently, upon:
(a) The amount of dust inhaled;
(b) the percentage of free silica contained therein;
(c) the size-frequency (or fineness) of the particles inhaled;
(d) the nature and sort of such other substances (including vapours
and gases) as may be inhaled simultaneously, or otherwise;
(e) the powers of resistance of the individual concerned;
(/) the presence or absence of a complication by an infective process.
In regard to (a), it was agreed that by the use of water and other
preventive measures the dust contents of air can fairly readily be
reduced to ordinarily invisible amounts. In Australian experience
this represents something in the neighbourhood of 4 or 5 milligrams
per cubic metre, or say 400 or 500 particles per cubic centimetre when
the particles are from 1 to 10 microns with a size-frequency ratio
of 3. It was, however, evident from the discussion that it is impossible,
under existing conditions, properly to correlate dust determinations
made in different countries, in different industries and for different
purposes, as well as for different immediate objects.
With regard to (b), it appeared from the information placed before
the Conference that silicosis can be contracted through inhaling for

TWELFTH SITTING

a sufficient period dust containing percentages of silica varying from
say 95 per cent, down to from 30 to 35 per cent, and even lower.
In regard to (c), it was pointed out that with existing preventive
measures carried out in certain mining areas there are now relatively
few large particles in the air; and it appeared from the discussion
that the greatest amount of harm is done by particles of less than
say 3 microns in size. Some of the evidence seemed to suggest that
particles of an ultra-microscopic size are factors in the causation of
the disease, but evidence in this direction was not conclusive.
In regard to (d), the experience on the subject of certain members
went to show that while exposure to various other dusts simultaneously
with silica might affect, the development of silicosis, the suggestion
that other dusts might be used as an antidote against silica should
be treated with great caution and reserve. Further research in this
direction is urgently called for. It was pointed out that experimental
evidence and practical experience under working conditions had shown
that prior or subsequent inhalation of other dusts in no way delayed
the development of silicosis.
In the course of the discussion under this heading some reference
was made to the alleged immunity from silicosis in some districts where
quartz in company with non-siliceous rock is mined, but it was pointed
out that further investigation had shown in the one case that the
allegation was unfounded in that the existence of silicosis had been
obscured by the migratory nature of the working population; while
in other cases it appeared that by reason, possibly, of the absence
of laws relating to compensation, the medical evidence is not so complete
as it might otherwise be, and there is sufficient room for doubt as to
the exact position of the workers vis-a-vis silicosis. In all cases where
there are laws relating to the compensation of silicotics it is but natural
that the examination of the workers will be more thorough.
In regard to (e), it was generally agreed that this is an important
feature, and there was a certain consensus of opinion that alternative
employment and periods free from exposure to siliceous dust tended
to increase the resistance and thereby delay the development of silicosis.
4. The discussion on methods for the prevention of dust and the
inhalation thereof fell, on broad lines, under the following headings:
(a) the use of water;
(b) exhaust draught applied at or near the point of origin of the
dust;
(c) dust traps and masks;
(d) ventilation ;
(e) other methods.
There was something said in favour of each of the methods referred
to. It was agreed that no one method is applicable in all circumstances,
but that in most cases, and especially in mining, there should be a
combination of methods.
With regard to water, it was pointed out that as far as the
Witwatersrand was concerned, it is used in three different ways, namely:
(1) to prevent the formation of dust during the drilling of holes, in
blasting, and the handling of broken rock;
(2) for the wetting of all surfaces with a view to securing a " fly
paper" effect in retaining dust which might settle on those
surfaces ;
(3) for spraying into the air in order to allay dust which had been
formed.

REPORT OF PROCEEDINGS

In regard to (1) it was generally agreed that the application of water
at the site of percussion or fracture tends to minimise the formation
of dust, but attention was drawn to the fact that in several operations,
e.g. rock drilling, stone cutting, grinding, etc., sparks accompanied by
dust escape even when the surfaces concerned are actually under a
film of water.
In regard to (2), the view was expressed that since there is no particular reason why dust particles of the order of less than 3 microns
should settle on the roof and sides of working places, and that they would
settle on the floor only after many hours, the value of these wetted
surfaces as dust catchers is probably small.
With regard to (3), it was pointed out that the dust particles with
which the Conference was concerned are of the same order in size as
micro-organisms, and that no one nowadays would expect to catch
micro-organisms by means of a spray. In this connection it was
mentioned as a matter of interest that Lord Lister, in his famous address
delivered at Berlin, had stated that he felt ashamed of ever having
suggested such a possibility in surgery.
The consensus of opinion was that as sprays are of little value for
removing fine dust from the air and that since, further, a humid atmosphere and the presence of droplets had been shown experimentally to
increase the risk of various infections their use should be restricted.
This view, however, does not necessarily apply to water blasts used
on the Witwatersrand when firing in development ends, since while such
blasts might not catch much of the finer dust (except by the subsequent
condensation of water vaporised by the heat generated in blasting) they
put into solution some of the noxious gases and wet the broken rock so
as to prevent the escape of the dust when that rock comes to be handled.
In regard to (b), it was mentioned that exhaust draught was of great
value in those processes of manufacture where there is an objection
to the use of water. In some cases water cannot be used for fear of
spoiling the material, and in other cases the workmen at times turn
it off because it makes them wet. In all such cases, exhaust hoods should,
if applicable, be used. It is necessary, however, that these hoods should
be placed in close proximity to the work, and that regard should be had
to the direction and speed of rotating objects. As an example of what
could be done in manufacturing processes by the use of exhaust draught,
cases were mentioned of a decrease in the incidence of silicosis which
had followed the abandonment of wet grinding in favour of dry grinding
with suitably applied exhaust draught. It was also pointed out that
before exhaust draught was used for the dry grinding of metals this
process was much more dangerous than wet grinding, but that since the
introduction of efficient exhaust draught with dry grinding the position
had been reversed.
(1) Dust traps. — As an example of the application of this method to
the drilling of holes in mines, mention was made of an apparatus (such
as is referred to below at the bottom of page 114) wherein the
drill steel operates through an artificial collar held against the face of
the rock; and through which ejector induced suction led the dust produced in drilling into a dust trap or filter. This apparatus was said to be
very effective and popular in certain collieries to which laws relating to
silicosis had recently been applied.
(2) Masks. — It appeared from the experience of members that
workmen submit readily to their use only when discomfort from the
inhalation of noxious dust could thereby be avoided.
In some circumstances loose fitting masks of the pressure type wherein

TWELFTH SITTING

a constant supply of fresh air under positive pressure is led in through
a flexible tube, have proved very efficacious. Such masks, however, are
useful only when the wearers can perform their work without the necessity of moving from place to place. The same applies to tightfitting masks supplied with air at normal pressure through a tube from
a distant source.
Other masks wherein air was inspired through a filtering medium
such as cotton wool, sponges, etc., and expired through a light non-return
valve, were also described.
• Reference was also made to masks in which the air to be inspired is
made to pass through a tortuous path and impinge on damp surfaces
which will retain the dust.
The feeling of the Conference was that while the masks at present
available may be of some value in special circumstances, and particularly in those cases where the formation of dust (and the consequent
necessity for precautions) is intermittent; they are so unwieldy or
interfere so much with respiration that their constant use is
impracticable during hard work and especially in a hot and humid
atmosphere.
In regard to (d)—Ventilation—there was but little direct discussion,
it being agreed that good fresh air ventilation was desirable, and indeed
essential. It was emphasised, however, that to be effective the ventilation
currents must be properly split and directed so as to sweep all dust-laden
air out of the mine or works, as the case may be, in much the same
way as dangerous gases are swept out of collieries.
With regard to (e)—Other Methods—mention was made of the fact
that some years ago an endeavour had been made on the Witwatersrand
to prevent the roof and sides of main intake airways from drying up
(and, incidentally, to secure the " fly paper " effect referred to in 4 (2) and
in the remarks thereon) by spraying those surfaces with solutions containing molasses, calcium chloride, and other hygroscopic substances, but
it had been found that these preparations absorb moisture so readily
that they soon trickle down into the gutters.
In discussion on this matter it was pointed out that if there really
are any advantages to be derived from the " fly paper " effect, these
solutions, and other sticky substances, could again be tried in the event
of it being found possible at a later date materially to reduce the humidity
of the ventilating currents. It was also suggested that these solutions
might be used instead of plain water, for preventing the formation
of dust in drilling, blasting, and the handling of rock.
In dealing with the dust formed by blasting, especially by blasting
in development ends, a suggestion was put forward that it might be
possible to project into the air at the time of blasting relatively large
particles of some innocuous flocculent dust which in its settlement or
progress through the mine would catch the harmful dust in much the
same manner as micro-organisms are caught in water purification plants.
A further suggestion put forward was that saturated steam might be
of some value, it having been found effective in industry in certain
special circumstances.
A still further suggestion put forward was that the escape of dust from
drill holes might be prevented by the use of a preparation producing
a foam.
5. During the course of the discussion, reference was made to the
difficulties experienced by investigators in the different countries in
properly appreciating each others findings. Some of those difficulties
arise from there being no accepted standards for comparisons in regard
7

REPORT OF PROCEEDINGS

to various conditions, dust counts, and so on; and others, through lack
of a uniform terminology. The Conference, therefore, decided to put
forward the following suggestions in the hope that those investigators
who were in a position to do so, and particularly the Research Division
of the International Labour Office, would take them up so as to pave the
way for some decisions and recommendations at a future Conference.
(1) While the methods of conducting and other details relating
to. the routine sampling of air are best left to each local authority,,
it seems highly desirable that for certain special critical and scientific studies of dust particles in air and their effects, there should
be established some standard method which for this special purpose
would permit of inter-industrial and inter-national comparisons;
in this connection it is suggested that the instruments at present
approved by the various experts should be taken into consideration.
The results of these investigations should be communicated to the
Research Division of the International Labour Office for
correlation.
(2) That as photographic and photo-electric cell methods of
dust determination have been successfully applied in certain
special circumstances, research should be undertaken with regard to
such methods, with a view to ascertaining their adaptability
in other circumstances.
(3) In view of the chemical theory of the causation of silicosis,
the importance of estimating the size frequency of particles has
increased owing to the fact that the surface exposure (which varies
greatly with different sized particles) is the chief factor in the amount
of silica which goes into solution. It is suggested, therefore, that
investigators should include in their work determinations of the
size frequency of particles.
(4) (a) The Conference urges that the investigations suggested
in paragraph (1) should be undertaken with the least possible delay
in all countries which are interested in the problem.
In view of the thoroughness and outstanding work of research
already carried out on the Witwatersrand, and in view of the special
facilities which exist in that area, the Conference attaches special
importance to the investigations which may be undertaken on the
Witwatersrand and ventures to express the hope that they will
be initiated at the earliest possible moment.
(b) The Conference recommends that as soon as the standard
method referred to in paragraph 1 has been perfected it should
be applied for the purpose of making at least one complete survey
of the dust concentration in dusty industries throughout the world.
The results of this survey should be communicated to the International Labour Office.
(c) The Conference considers that the survey recommended
in (b) should include an investigation into the relative size frequency
of the dust particles.
Every effort should be made to emphasise the fact that the
prevention of silicosis must be achieved by means of a whole series
of provisions relating to hygiene in mines—viz. chiefly by reducing
production and diffusion of dust, by maintaining the purity of the
air, and by means of personal hygiene;
(5) That no opportunity should be lost of stressing the importance of general and localised ventilation as one of the best hygienic
measures in dustv industries.

TWELFTH SITTING

(6) That the personal protection of the workers should not
be exclusively confined to such protective measures as, for instance,
the wearing of masks, but should be supplemented by secondary
measures such as the provision of suitable change houses and
shelters, and by the regulation of working hours, etc.
(7) That many of the points raised in the prevention and
control of dust call urgently for investigation by the physicists.
Note. — The present Report does not concern itself with medical
methods of prevention of silicosis.
PROGNOSIS, AFTER-CARE AND COMPENSATION

The Conference considered the Report on Prognosis After-Care and
Compensation and adopted it, after making various amendments.
The Report is as follows:
Reporters: Dr. Cunningham, Professors Hall and Koelsch, together
with Dr. Badham (co-opted).
In presenting our report it has seemed best to deal with each subject
separately.
Prognosis
This subject may be considered under four headings:
Question 1 : What is the prospect of a man exposed to free silica dust
as regards acquiring silicosis ?
This has been considered to depend on various factors :
(a) The nature, silica-content, size of particles, and concentration
of the particular dust to which he is exposed.
Concerning many of these points exact information is not forthcoming and it is desirable that further scientific investigations should
be carried out and the results carefully compared with the incidence
of silicosis amongst the workers.
(b) Period of exposure to dust.
(i) Length of service.
That this is a factor of importance is in accordance with the
views expressed by members of the Conference from every country
represented.
The length of service necessary to acquire silicosis may be
considerably prolonged by improvement in other factors.
(ii) Intermittence of exposure.
On this point the evidence forthcoming was not conclusive.
(c) Age of worker.
There is no evidence that per se this plays any important part.
(d) Physique of worker.
This is a factor of primary importance. An initial medical examination to ensure a certain standard of physique should be generally
adopted in those industries in which the risk of exposure to silica
dust is great.
Periodic medical examination of such workers is also essential.
(e) Race.
There is no evidence that this is a factor of importance.

100

REPORT OF PROCEEDINGS

Question 2: What is the prognosis in a case of silicosis if the affected
man leaves the industry at the first stage of the disease (ante-primary
stage of South African legislation) ?
The evidence on this point as regards various industries and from
different countries is somewhat conflicting.
In South Africa on the whole the evidence shows that the downward progress of the disease is in most cases riot arrested on leaving
the industry.
In this connection the questions of so-called infective cases, of reduced
economic conditions of life, and of the associated mental worries
probably play no inconsiderable part.
The view taken by the Medical Bureau in regard to the so-called
" infective types " of silicosis is that they do not come under the
classification of tuberculosis with silicosis unless the conditions in respect
of tuberculosis as laid down in the Act are complied with. The prognosis in such cases of infective silicosis is much less serious than in
cases of tuberculosis with silicosis as the term is used in the Act. Such
cases may live for many years in comparative comfort unless active
tuberculosis intervenes. The preceding evidence points to the urgent
necessity of further experimental study of the exact conditions connected
with silicosis of infective type.
Question 3 : What is the prognosis in a case of simple silicosis if he remains
in the industry after the first stage (ante-primary) declares itself ?
The evidence from South Africa suggests that in so far as mining
is concerned the continuation in underground employment of sufferers
from silicosis will aggravate the progress of the disease, except in
certain selected mining occupations.
As, owing to economic factors connected with compensation, only
a very small number of the silicotics in South Africa do remain at
work underground after the disease has declared itself, the evidence
on this point is somewhat indefinite. It is stated, however, that there
are at present about 150 men in this position, and it is said that their
progress is no worse than those who have left the mines. Among these
150 men, however, are included a considerable number of higher officials
whose duties do not now expose them considerably to dust and whose
economic position remains as good as before.
It is desirable to obtain exact information as to how far continuation
at work in occupations involving exposure to silica dust will influence
the progress of the disease.
Question 4: What is the prognosis in a case of silicosis with tuberculosis ?
(N.B. Before attempting to summarise the views of the Conference
on this point it is desirable to make clear exactly what we mean.
According to the terminology used in South African legislation " tuberculosis, means tuberculosis of the lungs or of the respiratory organs "
and is deemed to be present " wherever it is found by the Bureau
either (a) that such person is expectorating the tubercle bacillus, or
(b) that such person has closed tuberculosis to such a degree as seriously
to impair his working capacity and render prohibition of his working
underground advisable in the interests of his health ".)
This is always serious.
It is worse:
(i) when the tubercular infection occurs at the outset of silicosis;
(ii) in younger than in older subjects;
(iii) than in cases of tuberculosis alone.

TWELFTH SITTING

101

Recommendations
Prognosis of Silicosis
1. Exact information is not forthcoming concerning many of the
points relating to the nature, silica-content, size of particles and concentration of dust to which a man may be exposed and it is desirable that
further scientific investigations should be carried out and the results
carefully compared with the incidence of silicosis amongst the workers.
2. The physique of the worker is a factor of primary importance.
An initial medical examination to ensure a certain standard of physique
should be generally adopted in those industries in which the risk of
exposure to silica dust is great.
Periodic medical examination of such workers is also essential.
3. The evidence points to the urgent necessity of further experimental study of the exact conditions connected with silicosis of infective
type.
4. It is desirable to obtain exact information as to how far continuation at work in occupations involving exposure to silica dust will influence
the progress of the disease.
Compensation from the Medical Point of View
1. Silicosis complicated or not by tuberculosis constitutes an
occupational disease which may involve reduction of working capacity.
2. It should be left to competent authorities to decide, in accordance
with their particular conditions, whether other forms of pneumonoconiosis should be regarded as occupational diseases.
3. In establishing the amount of disability, account should be taken
of the clinical and functional condition as a whole.
4. The determination of disability should be entrusted to an independent medical expert, or body of experts, possessed of the requisite clinical
and technical knowledge, and having at his or their disposal suitable
apparatus for effecting the examination.
5. It is suggested that removal from all industrial occupations
involving exposure to noxious dust should be enforced in all cases of
open tuberculosis.
6. Where legislation provides for the compulsory removal from
occupations involving exposure to silica dust of workers affected by
silicosis, it is suggested that such compulsory removal should not
necessarily be applied to workers who have been in the same industry
for a period of not less than fifteen years and have reached the age of
forty-five years.
A iter- Care
1. Sanatorium treatment should be provided for suitable cases.
2. Hitherto most of the rehabilitation schemes have been unsuccessful.
Further investigation into this problem is urgently called for.
(The Conference adjourned at 12.45 p.m.)

102

REPORT OF PROCEEDINGS

THIRTEENTH

SITTING

Wednesday, 27 August 1930, 10 a.m.
Chairman: Dr. L. G. IRVINE

The Chairman : The minutes of the previous Sittings, with the
corrections made by members, would be taken as adopted. Any further
corrections which members had to make could be sent to the International
Labour Office in Geneva.
Mr. Phelan: The Conference might hold an informal conversation
on the next steps to be taken in the question of silicosis.
The Chairman: The Government Departments concerned should
maintain libraries on the question of silicosis.
Dr. Badham : The text of Recommendation IV (6) was incomplete.
It was decided that the corrected text should be distributed
immediately.
Sir Spencer Lister: The Conference might make a recommendation
regarding the safe storage of X-ray films.
After some discussion, it was decided that this suggestion should be
mentioned in the Minutes.
(At this point the representatives of the Press were admitted.)
Mr. Phelan: On behalf of the International Labour Office, he thanked
the delegates for the work which had been brought to a successful
conclusion. He realised that they had sacrificed their time and convenience in coming to this Conference. The special thanks of the Office
were due to Dr. Russell and Dr. Gardner, who had recorded yet another
proof of the unstinted scientific collaboration of the United States of
America. The thanks of the International Labour Office were also due
to the Chamber of Mines, and in particular to Mr. Limebeer and the Staff,
without whose help the small Geneva staff could not have coped with the
work. The thanks of the Conference were due to Messrs. Owen ¡Jones,
Ltd., for the loan of epidiascopes and microscopes; to the South African
General Electric Company for the loan of X-ray stands, and to Messrs.
Kodak (South Africa) for the album which they had presented to members. This was the first Conference which the League of Nations had
convened outside Europe, and a certain risk was involved, for Conferences had been known to fail in Geneva. This Conference, however, was
an unqualified success, largely due to the hard work of the delegates,
and in particular to the Chairman, who had conducted a highly technical
discussion with charm and fairness.
He presented the Chairman with a photograph of the members of the
Conference.
Professor Hall moved a vote of thanks to the Chairman, to whose great
clinical experience and to whose advice and help it was entirely due that
the Conference had performed its work punctually and unanimously.
Professor Böhme seconded the vote of thanks and said that all the
members of the Conference had admired the Chairman's expert knowledge
and tact.
The cote of thanks to the Chairman was unanimously adopted.

THIRTEENTH SITTING

103

The Chairman: He thanked the Conference for the honour which
they had done him. His original trepidation at taking the chair had been
replaced by a feeling of increasing pleasure in his task because of the
extraordinary spirit of goodwill and co-operation which the Conference
had shown throughout. He was much encouraged by the spirit of good
fellowship shown between scientific workers of many scattered nationalities.
South Africans did not always realise that the problem of silicosis
was world-wide and ramified into many other industries. The Conference
had largely recognised and accepted South African experience, but
equally valuable contributions had come from other countries. A large
measure of agreement had been reached on the causation and nature of
silicosis, but they had also been led to realise how much material was
not yet known. For these reasons, the Conference had laid down
lines for future investigation and research. He hoped the International
Labour Office would keep the spirit of international co-operation alive.
On behalf of the Conference he expressed his thanks to Mr. Phelan and
the Staff of the International Labour Office, to the Chamber of Mines,
to Dr. Orenstein, and to the various reporters.
Dr. Middleton moved a vote of thanks to the Vice-Chairmen.
Professor Hall seconded this vote of thanks.
The vote of thanks to the Vice-Chairmen was unanimously adopted.
Sir Spencer Lister thanked the Conference. Their duties had been
light because the Chairman had borne the greater burden.
Dr. Russell also thanked the Conference and the International
Labour Office for inviting him to be present. He was especially grateful
to the Chairman and the South African members for their hospitality
and friendship.
Professor Loriga: He had been more an observer than a collaborator.
He had thought that some of the conclusions in the papers submitted
to the Conference were exaggerated, but he was now convinced that
South African scientists had a very profound and accurate knowledge
of silicosis.
Dr. Kranenburg: The thanks of the Conference were due to
Dr. Orenstein, to Dr. Carezzi, and to the members of the Staff of the
International Labour Office.
The Chairman declared the Conference closed.
(The Conference adjourned sine die at 11.50 a.m.)

PAPERS
PRESENTED TO THE CONFERENCE

HISTORICAL REVIEW OF
MINING CONDITIONS ON THE WITWATERSRAND
AND T H E CHANGES WHICH HAVE TAKEN
PLACE SINCE THE EARLY DAYS OF THE FIELDS
BY A . E . P A Y N E , A.R.S.M., M.INST.M.M., GENERAL MANAGER, VAN RYN
DEEP, L T D . ;

HANS PIROW, D . S C , D.I.C. (LOND.),M.I.M.M., GOVERNMENT

MINING ENGINEER; AND

FRANK G.A. ROBERTS,

M. AND P.P., S.A.J.E.,

TECHNICAL ADVISER, TRANSVAAL CHAMBER OF MINE?

A review of mining conditions on the Witwatersrand from its inception
to the present day is chiefly interesting on account of the rapid change
which has taken place in these conditions and on account of the successive
steps for the prevention of miners' phthisis which the change in conditions
has necessitated.
At no time in the history of the Witwatersrand was the eventual
development of the industry fully foreseen. As new problems arose, new
methods were called for, and the dust prevention campaign led to
sustained effort and continuous research.
In order, therefore, to present a complete picture of the changes
which have taken place in mining conditions generally on the Witwatersrand, it is necessary to describe step by step the various phases through
which the industry has passed.
Mining may be said to have started on the Witwatersrand in
1886, and the first stamp mill was started in the following year.
From this time up to the outbreak of the Anglo-Boer War in
October 1899 it is estimated that an approximate total of 36 million
tons was crushed, or a little more than is crushed per annum
to-day.
The industry progressed slowly at first, and we find that the
State Mining Engineer of the South African Republic in his report
for the year 1898 records that there were employed only 9,854
whiteß and 73,354 natives in the mining industry; whilst the
Government Mining Engineer öf the Union of South Africa reported
in 1928 that there were in the service of the mines of the Witwatersrand for that year 21,341 whites, 176 Asiatics and 194,362 natives

108

PAPERS PRESENTED TO THE CONFERENCE

and other coloured persons. An analysis of the occupations of
these employees would indicate that approximately 53 per cent.
of the whites and 78 per cent, of the natives and other coloured
persons were employed underground.
At first the workings were of course shallow, and in the oxidised
or " free milling " zone, where the rock was relatively soft, friable
and damp. The average depth to which this zone extended varied
from place to place, but rarely exceeded 300 feet, and in some
places was as little as 100 feet. From near the bottom of this zone
the rock gradually became harder and more pyritic, until at vertical
depths averaging in the neighbourhood of, say, 500 feet it had
much the same characteristics as that which is being mined to-day.
By the year 1892 extensive deep-level companies had been
formed, and drilling by machines had been introduced, principally
at first for development work, and we find that the number of
machine drills at work in 1896 was just over 1,000, increasing in
1899 to over 2,000 in number. These machines were of the rigged
reciprocating type, and weighed up to 350 or even 400 lbs. each.
They were operated mostly by miners from overseas with the
assistance usually of two or three natives, but it was not until
some years later that it became the practice for the natives themselves to operate the machines.
Though the " reef " had been intersected in deep boreholes,
e.g. Rand Victoria Borehole in 1893, at a depth of 2,343 feet, and
1895 in the Bezuidenville Borehole at a depth of 3,127 feet, there
had been very little thought for the ventilation of the mines as
the depth and extent of workings increased, nor had the health
of employees caused any anxiety in the minds of the managements
or Government.
As long as the mines were working in the free milling zone very
little dust was produced, and since the mines were shallow, and
in consequence well ventilated, it is unlikely that the men came
to any harm through dust.
We find that following the disturbances which gave rise to the
Jameson Raid in 1895 the Government of the South African
Republic appointed in April 1897 an Industrial Commission of
Enquiry to look into the position of the mining industry. The
records of that Enquiry can be searched in vain for any grievance
as to conditions of health, or suggestion as to disability arising
from the method of mining the banket.
It may be said that before the Boer War no one, or at least very
few people, suspected that the mine dust was in any way injurious

WITWAT.ERSRAND: HISTORICAL REVIEW

109

to health. The few who did complain were mostly surveyors who
had difficulty in taking some sights on account of the bad visibility
caused by the dust, and they were laughed at and told that
" everyone must eat a peck of dust before he died ".
The conditions in those days, however, if compared with present
standards, would appear to be very bad. Much of the drilling,
especially in development ends, was done dry; blasting was
permitted at any time during the shift provided it did not interfere
too seriously with work, and cases of gassing were frequent. Broken
rock was shovelled in a dry condition, and, generally speaking,
the mines were so dusty that workmen at the end of their shift
looked like millers. The shifts were materially longer than at
present, the average being in the neighbourhood of ten hours.
Night shift for ordinary work was common practice and the interval
between shifts was very short ; indeed, on development work there
was no interval at all in some cases, the common practice being
for the miner to drill over the round, turn on the compressed air
and blast the cut, returning in about half an hour to blast the
round, having in the meantime sent word to his mate on the
surface that it was time for him to come down. These men thus
worked no regular shift, but relieved each other whenever they
happened to finish a round.
The conditions under which they lived would also be described
as bad in comparison with those of the present day. There were
but few change-houses, and where these were provided the tendency
was for the men to refuse to use them. Most of the men lived in
single quarters provided by the mining companies, two, and
sometimes three, in a room which, while perhaps adequate in size,
would be said to-day to be insufficiently ventilated. In the earlier
days these rooms were made of wood and iron, and the variations
in temperature were considerable. As time went on, however, it
became customary to line such rooms, first with matchboarding
and afterwards with sun-dried brick and plaster.
In regard to social amenities, places of amusement, recreation
facilities, etc., it could be said that these were non-existent, meagre,
or confined to the towns, with the result that many of the men,
and especially the single ones, tended to congregate in bars and
to indulge in month-end orgies.
On the medical side, the conditions on the Witwatersrand have
never been very bad, except perhaps in the earlier days and during
outbreaks of what was commonly called in those days " camp
fever". Men were quick to realise the advantages of sick benefit

110

PAPERS PRESENTED TO THE

CONFERENCE

societies, and these were brought into being at a comparatively
early date, and it can be said that, generally speaking, they were
functioning with some success, especially on the larger mines, as
far back as 1895-1896.
It is not until the Government Mining Engineer of the Transvaal
Mines Department, in his report up to June 1902, introduces the
subject of the health of workmen t h a t any appreciation seems to
have been given, to the matter. In his report first mention is
made of " miners' phthisis " as a disease " which seems to be
peculiar to men employed in rock drill work ". It must be understood that up to this time the breaking of ground in stopes was
almost entirely done by hand labour, i.e. by native labourers
drilling single handed. Machine drilling was confined to development work. Careful enquiry at this time elicited the fact t h a t out
of the 1,177 rock drill men employed on the Rand prior to the
Anglo-Boer War, 225 or 16.75 per cent, were known to have died
from miners' phthisis. The actual number may have been greater.
It is certain, however, t h a t if it had not been for the break in the
working of the industry due to t h a t war the mortality rate would
not have been so fully realised. In considering this rate, however,
it must be borne in mind t h a t most, if not all, of the men concerned
had worked previously in overseas mines in Cornwall, Australia,
and elsewhere, and may have laid the foundation for their disease
in these.mines.
In 1902 the Governor of the Transvaal.appointed a Commission
to enquire into and report upon the prevalence and causes of the
disease known as " miners' phthisis " and to make recommendations
as to the preventive and curative measures which should be adopted.
One outstanding result of their enquiry, which was made known
in 1903, was t h a t :
Although the incidence of the disease appears to be more marked
in miners who have been working rock drills for some years, yet it is
also found to prevail amongst miners who have never worked them;
and the Commission recommended, amongst other things, t h a t :
(1) The discharge of minute angular particles of dust in the mine
air should be prevented;
(2) The working places should be supplied with air in sufficient
quantities to render harmless and sweep away all vitiated
atmosphere.
The fact that other than rock drill miners were affected by this
disease gave a spurt to improvements in the ventilation of workings

WITWATERSRAND : HISTORICAL REVIEW

111

and in the use of respirators for those actively engaged in rock
breaking.
Early development work was done by hand drilling, and headings
were consequently on the small side. Practically all the early
shafts were inclines with three relatively small compartments ; and
the drives were about 6 feet by 4 feet. When rock drills were
introduced these dimensions were increased somewhat, but as a
general rule the headings still remained small, namely, about
6 feet 3 inches by 5 feet 6 inches.
It can be said that most of the mines turned out to be poorer
in depth than was expected, and this, together with heavy capital
expenditure and other causes, necessitated increases in capacity
materially beyond -what the mines were originally laid out to
produce, and brought about a congestion in the matter of handling
rock, men and material.
In the year 1903 it was realised that, owing to the increasing
average depth of the mine workings, it was no longer possible to
allow the European miners to come up for their midday meal, and
the fact that these men must in consequence remain in the mine
for the whole duration of their shift was an additional urge towards
the improvement in the distribution of the ventilating current,
hitherto only due to the difference in pressure of the atmospheric
conditions. Steps were taken to improve this pressure by various
means, such for example as building up one or more of the compartments of the up-cast shaft; erecting drill sharpeners' furnaces at
the bottom of the up-cast, and to a small extent in carrying light
pipes from the face of drives to an up-cast shaft or raise.
Arising from the congestion referred to above, it was common
practice for persons, and especially natives, to walk up long
distances to get out of the mines. This position was gradually
improved by the sinking of new shafts and the installation of
larger and more powerful hoists, and in 1917 the Mining Regulations
laid it down that the manager should provide arrangements for
hoisting all persons when the height exceeds 500 feet measured
vertically. (See Regulation 158 (25).)
In addition to the purity of the air, and freedom from gases due
to the quantity of explosives used, attention was now first paid
to the quality of the lubricating oils used in compressing air for
the machines, through the exhaust from which it had been proved
that in some cases dangerous gases had been disseminated into
the mine atmosphere. At the same time attention was called to
the use of damp and weak detonators, as well as to both the

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overcharging and the undercharging of holes with nitro-glycerine
explosives which result in the production of noxious fumes. In this
same year (1903) the Chamber of Mines, a body formed in 1889 to
represent the joint activities of the mining industry, offered prizes
for the best method of allaying dust caused by machine drilling.
The first prize was won for a water-spray or atomiser, and the
second for a patented water-fed drill.
About this time improvements in machine drills designed to
increase the speed of drilling began to make their appearance. The
heavy old-fashioned type of reciprocating machines were gradually
replaced by lighter and faster drilling ones, and a few machines
of the Leyner hammer-drill type were introduced. These lastmentioned machines, however, employed hollow drill steel through
which compressed air was blown in order to keep the drill bit free
from chips, and they were thus, as dust producers, much worse
than any of the machines which had hitherto been used. Indeed,
they produced so much dust that it was usually impossible in
development ends clearly to discern the operators. Dry air blowing
machines of this type, however, did not remain in vogue for more
than a few years.
It is at this stage that the industry was first confronted with
the extreme conservatism of the operatives in the use of any
dust-preventing devices. They objected to sprays designed to
prevent the escape of dust formed in drilling and operated from
the exhaust of the machine, on the ground that it made them
too cold. They objected to sprays and the use of water generally,
on the ground that it gave them rheumatism, and so on, and that
they would just as soon die of miners' phthisis as of those other
diseases which wet working places might cause; and they objected
generally to any of the precautions which by occupying time
tended to decrease their earnings. The Government, and indeed
the industry itself, were forced therefore to recognise that outside
the improvements in devices for dust allaying there would appear
to be need for special legislation to enforce the use of any recognised
means for the prevention of silicosis.
Act No. 54 of 1903, and the Mines and Works Regulations
promulgated thereunder, is the first step of a long series of legislative measures to control the conduct of mines in the direction
of the use of the best form of preventive measures, which continuous
research in the cause and prevention of miners' phthisis showed
to be desirable.
Starting with Chapter VI of the 1903 Regulations, containing

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four regulations on ventilation, and one reference, Chapter IX,
Regulation 97 (8), that the ganger shall be responsible that no
person enters the working place " until the fumes caused by the
explosives shall have been sufficiently dissipated ", we have to-day
Regulations in great number designed to control the ventilation;
chemical analysis of air; limitation of blasting operations; exposure
of persons to dust and fumes after blasting; the replacement of
vitiated air by a certain volume of fresh air after blasting; the
conditions for working in back stopes; the entry into working
places; the use of water under adequate pressure in all working
places; the use of water when tipping and handling broken ore;
the use of water in drilling any hole; the clearing or blowing out
of any hole after drilling; the use of tamping material in charging,
and the quality of the lighting torch; the interval between blasting
shift and return to work in the mine; the control of water blasts
and auxiliary ventilation in development ends after blasting; etc.
To ensure the proper observance of these precautions, responsibility
is laid upon miners and officials of all grades from manager downwards. Tn a Code of Regulations, which twenty-five years ago
could be comprised in a volume of 52 pages, we find now detailed
Regulations for the health and safety of the mines comprising a
volume of over 200 pages, of the same size, under Act No. 12 of
1911 and many subsequent revisions of the same under Government
Notices.
It will be interesting to return to the history of the investigation
into the disease of miners' phthisis, now bearing in mind that
every relevant factor in prevention has in one way or another
found its corollary in legislative injunction.
In 1907 the Government of the Transvaal appointed a Commission
known as the " Mining Regulations Commission " to report on the
working of the Mines, Works and Machinery Regulations, with
special reference to (amongst other things) ventilation and the better
protection of the health and safety of persons working in mines.
This Commission extended its enquiry over the years 1907-1910,
and laid the foundation for the scientific investigation into the
disease of miners' phthisis. We gathered that all true cases of
miners' phthisis are primarily cases of silicosis, and that finally a
tuberculous infection commorly becomes superimposed upon this
condition and the symptoms and course of the disease alter
accordingly. The suggestion arose also as to whether the exposure
to noxious fumes might be a predisposing cause of miners' phthisis,
and we were told that medical opinion was against exposure
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to such fumes and that preventive measures should follow t h e
lines of:
(1) The prevention of dust inhalation;
(2) The prevention or removal of noxious fumes resulting from
explosives ;
(3) The prevention of silicosis.
By amendments to the 1903 Regulations the responsibility of
the manager had already been extended to the compulsory use of
water with machine drills, and to the prohibition of the removal
of dry and dusty rock unless it had been wetted so as to prevent
the escape of dust into the air. It was now for the first time
recommended t h a t responsibility should be placed on the manager
for supplying the necessary water and on the miner for its use ; and
t h a t inspectors of the Mines Department were to be instructed t o
pay special attention to its use (24 December 1908). On t h e
adoption of these recommendations, the supply of water had to be
made continuous, and all places where development work was
carried out and every dry and dusty stope (when the natural
strata are not wet) had to be kept damp. Blasting had to be so
arranged that men working in other places were exposed as little
as practicable to dust and smoke. The use of water by the miner
was tightened up, and in drilling holes with any percussion machines
he was enjoined to use a water jet or spray, and he was not allowed
to enter a working place after blasting until the fumes had been
sufficiently dissipated, unless he was wearing an effective respirator
or other apparatus to prevent the inhaling of fumes or dust.
The next step was to enact t h a t the miner should keep the floor
and sides of his working place within a distance of 10 feet sufficiently damp to prevent dust being raised by the exhaust from
his machine. Further, t h a t rock to be shovelled should not only be
superficially damp but should be kept damp in the process of
shovelling. To ensure t h a t these precautions were being carried
out, and to combat the seeming indifference of rock drillers, it
was laid down t h a t a shift boss should report to the manager daily
whether the requirements of these Regulations were being observed
or not.
At about this same period (1908) attention was directed t o
contrivances for the catching of dust caused by the drilling of
holes. Some of these had been used in Western Australia and in
Cornwall, as substitutes for water jets and sprays which in the
drilling of steeply inclined holes caused discomfort to the workmen,.
added humidity to the atmosphere, and were thought to tend

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towards the production of ankylostomiasis and other diseases.
These devices took the form of flexible collars fitting tightly against
the rock, and through which the drill steel operated. In some
cases the dust was caught in a bag, and in other cases it was sucked
away by an air jet ejector and led into some form of dust trap.
None of these devices, however, were successfully adopted.
In most mines in those days, and especially in those mines where
the capacity of the reduction plant had been increased, there was
an inadequate number of working places from which to obtain the
necessary amount of ore. This shortage of working faces necessitated
a heavy development programme, and a double shift method of
working with blasting at least twice every twenty-four hours.
At about this same time and with a view to reducing the danger
arising from the dust and fume caused by blasting, experiments
were made with various methods of projecting into the air at the
time of blasting in development ends a volume of finely divided
water, and these experiments led ultimately to the general adoption
of an apparatus known as a water-blast, which has now by
regulation to be used at blasting time in all development ends and
again before persons are permitted to re-enter.
When, as a result of the increased amount of development
work, the number of working places became adequate, the custom
of miners returning to their working places too soon after the blast
was abandoned and single shift blasting introduced.
The consideration given to the incidence of tuberculosis by the
Commission of 1907-1910 revealed the prevalence of this disease
in particular amongst the native workers, and gave rise to the
promulgation of preventive measures already known to be effective
in combating this disease elsewhere than in mining. It initiated
the examination of natives prior to engagement for mine work, and
contemplated the possibility of having to take similar steps in the
case of white workers. In both cases it was urged that infected
workers should be excluded from the mines as soon as the disease
had been diagnosed.
The sanitary arrangements underground were very bad in the
early days. Indeed, it could be said that they were bad up to
less than twenty years ago. At first no sanitary conveniences of
any description were provided, and persons wishing to relieve
themselves had no option but to walk out of the mine or to go into
some disused workings. Afterwards it became customary for
persons to use the rock boxes, so that the faeces would be hoisted
with the ore. Later on, after the necessary provision of an adequate

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number of latrines had been made, it was very difficult to break the
natives of their bad habits and to educate them to use the latrines.
It was not until well after the Boer War that the mines began to
provide drinking water underground. Prior to this the men made
their own arrangements and either took water down with them or
drank from one or other of the numerous water-bearing fissures.
Attention was now first drawn to the need for cleansing shaft
stations and such waiting places as workmen were in the habit of
using in the mines, whilst the housing conditions of both black
and white were thoroughly reviewed. Change-houses for the white
miners were made compulsory. Medical inspectors for the mines
were recommended, and in the Johannesburg District this duty was
taken over by the Medical Officer of Health of that town, and has
been carried out very thoroughly ever since.
Another important consideration of the Commission was the
duration of the working hours of mine employees. The chief ground
for the reduction of working hours claimed by employees was that
of health. The Commission found that there was no reason why
work underground should be" more unhealthy than work on the
surface. In practice, however, this was found difficult to ensure.
On the other hand, it was found that miners were not being
employed more than eight hours a day at their work, the rest of the
time being occupied in taking their meals, in getting to and from
their working places, and in other ways. Recommendations were,
however, drafted and later brought into force in Act No. 12 of 1911,
limiting the hours of work to forty-eight hours per week, and the
hours of certain employees to not more than ten per diem. The
erection of underground drill sharpening shops was prohibited
except under conditions controlled by the Mines Department.
This Commission, in investigating the quantity standard of air
to be supplied in accordance with the 1903 Regulations, found that
without detailed Regulations it was difficult to enforce. It turned
its attention also to the quality of the air. It laid down a legal
maximum for certain noxious gases, e.g. C0 2 , CO, and nitrous
oxides. It pointed out that suitable mechanical appliances should
be erected and operated to direct the ventilating currents when
natural ventilation failed to operate; that old workings should be
closed off, and plans should be kept to show the necessary stoppings
and methods of control. In development work where machines
were operated suitable arrangements were to be furnished for
removing the dust, smoke and gases after a blast, and no man
should return until the air was clear of such.

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Undoubtedly a great deal of valuable ground was covered
by this Commission, and the book of Regulations which, as above
referred to, had been contained in 52 pages, was extended to
136 pages of the same size. The responsibility of the mine managers
was extended to include the supply of clean water and suitable
waiting places for native workmen and causing them to wait there,
and powers were given them to take such disciplinary steps to enforce
the requirements of the Regulations as the Inspector of Mines
might direct or approve.
During the period covered by the 1907 Commission the mining
industry had passed from the control of the responsible Government
of the Transvaal to that of the Union Government of South Africa.
A greater change was, however, taking place in the personnel of the
operatives. In the early days of the industry the skilled white
miner was almost entirely recruited from overseas, either from
Europe, and principally from England, or from Australia. Owing
to the incidence of the disease of miners' phthisis amongst these
men, and to other causes, the mining field was ceasing to be
attractive, and during the industrial trouble which arose in the
industry in 1907 a large number of South African nationals were for
the first time engaged by the mines and drafted into the occupation
of mining, very largely as supervisors of the native gangs, and
primarily, of course, in the less skilled operations of tramming,
shovelling and other underground work. The South African
national naturally lacked the mining knowledge of the overseas
miner who had been brought up to mining since his childhood, and
hence at first a great deal of care and training was necessary. In
the course of time, however, the South African national began
to get educated in this work, and at present over 60 per cent.
of the employees of the mines are South African born, whilst a
much larger percentage of those working underground are of
that class.
The Union Government in February 1912 appointed a îMiners'
Phthisis Prevention Committee " to enquire into, by experimental
and other investigation, and to report from time to time upon
the improvement of, the methods for the prevention of miners'
phthieis in the Witwatersrand gold mines, and to advise upon the
introduction of a systematic and uniform policy and the amendments to the Mining Regulations which may be necessary for
combating the disease ". This Committee reported in March 1916
on its work up to the end of 1915, and finally in January 1919 on
its conclusions. There were throughout this period preliminary

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and special reports, as well as many memoranda submitted to
the Government. Parallel with the growth of knowledge came
legislative steps to enforce prevention, all the more necessary
because of the change in the personnel of the miners and of the
ignorance of the subject amongst them, now allied to the natural
conservatism of the individual.
The material knowledge of the disease gained by this Committee
was very great, but it may be said that in its conclusions it endorsed
the already known fact that avoidance of the inhalation of air
charged with injurious dust was the most important line of action
towards the elimination of the disease amongst the operatives.
With this fact in view, it was recommended that single shift
blasting should be introduced ; and the legal and moral responsibility
of all mine employees was stressed as to the proper use of water
for dust allaying purposes.
The Committee gained accurate knowledge of the incidence of
the disease by medical examination oi miners and a careful analysis
of the silicotic condition of such men. Examination of the lungs
of deceased miners gave rise to a knowledge of the size of the
dangerous dust particles, and this led to the introduction of apparatus for the measurement of dust in the mine atmosphere.
At the same time it was first mooted that a careful selection of
the recruits amongst the white miners would be an important
preventive measure. It was also first suggested that main travelling
shafts should be downcast and men should be kept out of upcast
shafts after blasting " until the air is free from dust and fumes ".
The Regulations drafted to carry out the preliminary recommendations of this Committee were coded in an issue of the Mining
Regulations of 1913. Briefly, the use of water for dust allaying
purposes was extended and its use detailed. For example, the area
round a working place to 25 feet instead of 10 feet had now to be
kept wet. No one should enter, or permit anyone to enter, a close
place after blasting within thirty minutes, and then only if the air
was free from dust, smoke and fumes perceptible by sight, smell
or other senses. The manager was called upon to arrange the time
for blasting operations so that workmen should be exposed " as
little as practicable " to the fumes and dust from blasting. The
manager should supply a constant supply of " clean and odourless "
water in pipes of not less than a certain size and not less than a
certain pressure, such pipes to be carried to not less than a certain
distance from the face. Water blasts were to be installed in every
development end. No person should be allowed to remain in the

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mine if the air contained dust, smoke or fumes perceptible by sight,
smell or other senses. The cross ventilation of miners' back-tohack quarters was provided for. Miners must acquaint their native
workmen of the requirements of the dust-preventing Regulations.
The manager shall keep all main travelling ways wet as far as
practicable; shall cut off from the ventilating currents old stopes;
shall place ring sprays in downcast shafts not naturally wet. After
1 January 1915 no one shall be permitted to blast the cut and round
separately in the same shift in the same development end. Finally,
provision should be made for recording the measurement of dust
in the mine air as periodically determined. The use of a water jet
with a percussion machine should be coupled with " or the use of
a drill with axial water feed ". The collaring of holes with machines
should have a special volume of water used in the process of collaring. The tube used for drilling holes should be inserted in the hole
so that the water might be brought to the cutting edge of the drill.
After a certain date only an axial water feed machine should be
used for raising. The Inspector of Mines should fix an interval of
time for each mine between the time of blasting and the next
on-coming shift of workmen. An official should be appointed
to each mine to report upon the water service, ventilation and
prevention of dust.
It is useful to record the improvement over this long period of
the conditions in the mines in the direction of dust prevention as
reflected in the opinion of Mr. J. E. Vaughan, who had been away
from the Rand as Inspector of Mines in Natal for some years and
returned to note the marked improvement, and reported to the
Government Mining Engineer under date May 1918 (vide Appendix
No. 8, page 97, Final Report of the Miners' Phthisis Prevention
Committee, Johannesburg, 10 January 1919). Improvement was
noticeable in the attitude of the operatives to the many increased
Regulations and the observance of them. There were improvements
also in the water supply, dust sampling, and general cleanliness of
the mines and working places. Water was everywhere being used;
the air of the mines was free from visible dust ; no dust was noticeable
in the nostrils of the operatives. Improvements could still be made
in the direction of the ventilating currents.
During this period there had been a further revision of the Mining
Regulations. In 1913 the book was enlarged from 136 pages to
177, and in 1917 by a further addition up to 194 pages. There
were of course additions for safety purposes other than those for
the prevention of miners' phthisis.

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The principal alteration in connection with Chapter VI on
ventilation was that the amount of fresh air to be supplied for
every person employed underground should be not less than 30
cubic feet of air per minute during the full period of twenty-four
hours. The current should be suitably split and each ventilating
district should receive its standard. Determinations of the quantity
actually circulating should periodically be made. The replacement
of air after blasting in dead ends was regulated and no working
in back stopes was allowed without conditions imposed by the
Mines Department. Provision was made for the duties of the ganger
(Chapter IX) to wash over the face and immediate vicinity with
water under adequate pressure before work was commenced. He
was not allowed to use a percussion machine other than an .axial
water-fed machine without an additional water hose, nor a hand
drill without a wet swab. Nor could he blow out a hole with compressed air unless he had first applied sufficient water to prevent
the formation of dust. No person should allow water to run to
waste. He shall report any cases of gassing, however slight.
It must not be supposed that all this time progress in the combating of the disease of miners' phthisis was confined only to such
bodies of men as were working on the Government Miners' Phthisis
Prevention Committee. The Chamber of Mines in 1914 appointed
a Standing Committee on Dust Sampling. This Committee
undertook the standardisation of methods for the determination
of dust in the mines. It carried out periodic dust surveys of all the
mines and created a laboratory for accurately determining the
samples. At the same time it embarked upon a considerable field
of research work, as well as being available for testing any dust
preventive devices submitted to it or to the industry. Some of
this work is carried on to-day by this Committee, and some has
devolved upon the dust inspectors appointed on each mine according
to the Mining Regulations. A ventilation expert attached to the
Committee lectures to these mine dust inspectors, and the standard
of knowledge is improving.
When water was first used for dust prevention and allaying, little
or no effort was made to ensure its suitability for that purpose, and
the nearest water available was used irrespective of whether it was
clean or otherwise. As time went on it came to be recognised that
dirty water when atomised might actually put dust into the mine
air rather than allay it. The practice for some years past has been
to use only clean water free as far as possible from fine silica
particles, and approved by the Committee.

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Through the chemical analysis of mine waters; of different
kinds of mine rock; through the analysis of the dust produced
by different kinds of machines; the analysis of air samples and
the constant improvement of sampling methods, whether by
sugar tube or konimetry, this Committee has a fine record of
close and conscientious observance of the dust conditions of
the mines. It is dealing to-day with dust particles both in
quantity and magnitude of such small dimensions that the dust
in the atmosphere of the mine can be compared to a possibly
noxious gas which must be swept away and replaced by fresh air,
rather than that any further means of allaying it could be attempted
with success.
The Chamber of Mines also in December 1915 introduced on its
own initiative a scheme for annual holiday leave, where under
all mine employees, subject of course to certain conditions,
receive an annual holiday on full pay (not exceeding 22s. per day).
Under this scheme underground employees receive fourteen
consecutive days' leave (of which the twelve weekdays are on
pay) after one year of continuous employment; twenty-one days'
leave after two years of such employment, and twenty-eight days'
leave after three years, and there can be no doubt that this welcome
break is of considerable value in preserving the health of mine
employees.
The managers of the mines, several of whom had contracted
the initial form of the disease of miners' phthisis, i.e. silicosis,
were as a body very active in their insistence upon the best-known
methods of dust prevention being strictly enforced. The method
of single blasting has already been referred to, and was undoubtedly
a most important factor introduced on the initiative of the managers
themselves. Another important innovation was their recommendation in July 1915 (vide Time and Labour Saving, Association of
Mine Managers, 1916) that a Central Bureau for the systematic
examination of the physical fitness of men engaged in underground
work should be established. This suggestion was adopted in 1916
by the Union Government, who in 1912 had framed legislation
for the compensation of persons suffering from miners' phthisis.
The trend of the Union Government's legislation in the matter of
compensation for miners' phthisis does not come within the scope
of this historical review of mining conditions on the Witwatersrand,
and is therefore being dealt with under another heading. It must,
however, be remarked that there is but little doubt that, following
the increases in the amount of compensation awarded under the

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Miners' Phthisis Acts, a number of persons, not realising the seriousness of silicosis and its tendency to progress into miners' phthisis,
carelessly or deliberately and to the danger of others exposed
themselves to dust and fume with a view to obtaining compensation.
This particular phase lasted for some time, but it is not suggested
that anything of the kind has been done in more recent years.
Following the efforts of the Miners' Phthisis Prevention Committee
(1912-1918) previously referred to, the Mines Department instituted
a systematic survey of the mines to ascertain in what way the provisions of the Regulations were being observed. This was found to
be helpful to individual managers, and attention was particularly
directed to ventilation, water blasts, night shift work, machine
drills, shaft sinking and organisation, which still left room for
improvement. In the matter of machine drills the Leyner type and
axial water feed machines were rapidly replacing the reciprocating
type of machine, and it was noticed that whilst the speed of
drilling operations was increased by the application of water through
the hollow-drill steel to the cutting edge, large quantities of dust
were created by these machines through the passage of air down the
hollow steel and the blowing up of small bubbles of air containing
dust through the sludge discharged in drilling. These bubbles
burst and, though containing exceedingly fine particles of dust,
created a dangerous atmosphere for the operatives. It was found
that, even in shaft sinking, where the shaft bottom was covered with
water, the atmosphere at the shaft bottom contained dangerous
quantities of dust when this type of machine was in use.
A long investigation commenced into the use of the Leyner
type of machine and into the nature of the dust produced by it.
It was found that by the use of a long piston the excess air could
be prevented from passing down the drill to the cutting edge, and
legislation was introduced to prohibit the use of any other than
this type of machine, at first only in development work, and
subsequently in all kinds of work, unless the machine was fitted
with a front head release ring for the escape of air.
It followed from this investigation that the Government Mining
Engineer should have power to prevent the introduction of any
type of machine which might be dangerous to the operatives in
its dust-creating properties, and also that for similar reasons he
should have power to prohibit after due notice any type of machine
already in use. Such powers were accordingly taken by the
Government Mining Engineer under the Mining Regulations in
1922.

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At this stage it will be of interest to point out that the heavy
reciprocating drills of the early days drilled holes averaging from
6 to 7 feet in length with a diameter of about 2% inches at the
collar and about l 3 / 8 inches at the bottom. These machines in
stoping rarely drilled more than four or five such holes during a
shift.
The present-day hand-held jackhammers drill holes averaging
from 3 to 4 feet in depth with a commencing diameter of about
l1/* inches and a bottom diameter of about 1 inch, and it is a
common thing for these machines to drill as much as 120 feet in a
shift; the average for the whole Rand being in the neighbourhood
of 75 feet per machine shift.
Another point which may have some bearing on miners' phthisis
is that prior to the outbreak of the Great War in 1914 the mines
used blasting gelatine almost exclusively for development work,
and 60 per cent, gelignite for stoping, the average strength of the
explosives used being in the neighbourhood of the equivalent of
81 per cent, nitro-glycerine, whereas to-day the average strength
used is in the neighbourhood of 55 per cent, nitro-glycerine.
Another way of illustrating this change would be to say that prior
to 1915, 0.83 lb. nitro-glycerine was used to break a ton, whereas
the average consumed now is in the neighbourhood of 0.58 lb.
nitro-glycerine per ton broken.
The so-called " contract " system has been a feature of mining
on the Witwatersrand since the early days of the fields. It has
been alleged that this system, which is in reality a method for
paying European miners at piece-work rates, was to some extent
responsible for the causation of miners' phthisis, in that men were
induced under it to neglect precautions for the prevention of dust
for the sake of additional gain. This matter of underground
contracts was enquired into by a Government Departmental
Committee in 1917, and this Committee found that the " contract
system is not necessarily deleterious as regards the health or safety
of those concerned, or morally unsound and against the public
interest ". (Conclusion No. 2.) (See paragraphs 32 and 33 of the
report of the Committee.)
A further Miners' Phthisis Commission was appointed in 1920,
primarily to deal with legislation for compensation. It went
also fairly thoroughly into the preventive measures in use at the
time. We find in this Commission's interim report the first
reference to the suggestion that " the use of water for dust allaying
is nearing the limit of its effectiveness and that therefore additional

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methods, amongst which ventilation ranks foremost, will have to
be relied upon for further progress in this direction ". This
knowledge was given to the Commission by the work of a Joint
Committee of members of the Mines Department and the Chamber
of Mines Dust Sampling Committee, who in particular investigated
the efficiency of water blasts in development ends and the amount
of air required after the blast to clear the end of dangerous dust
particles (Reports 13/10/1922). This arrangement for attacking
problems in ventilation was found to be useful, and was extended
during the year 1923 to testing the best method of ventilating a
close end when work was being carried on, especially drilling by
machines. The quality of the intake air was thoroughly
investigated and much knowledge obtained as to the direction in
which improvements in the health conditions of the operatives could
be made.
In improving the Leyner type of machine and reducing its
dust-producing properties when air was allowed to pass down
the hollow-drill steel, it was noted that the size of hole in the drill
steel and the pressure of water were important factors in dust
control. Whilst the long piston type was compulsory for use in
close ends, the Government Mining Engineer intimated to the
industry in April 1925 that he thought the time had arrived for
prohibiting all machine drills passing air down the hollow jumper
and that only machine drills approved by him should be permissible
in all classes of work. He agreed to tests being made as to the
relative importance of the many variables in the matter, but
hinted that the adoption of a front head release to all machines
immediately would appear to be justified, and arrangements to carry
out this were made law as from 23 October 1926.
The tests conducted extended over a period of about two years,
and were made in a test chamber at the Consolidated Main Reef
mine, under the control of an Investigating Committee composed
of members of the Central Mining and Investment Corporation's
engineering staff and the Chamber of Mines Dust Sampling Committee. A report issued in July 1927 demonstrated that with
release ports, maximum bore water tube and an extra hose for
collaring, the dust produced by rock drills would be reduced to such
a small amount as to render it a very minor factor in the production
of silicosis.
This conclusion is of importance when it is considered that
from 1923 onwards the number of jackhammer machines introduced
into the mines increased, until to-day in many mines all ground is

WITWATERSRAND: HISTORICAL REVIEW

125

broken by machine drills of this type. The care of the water tube
is an important factor and has been very largely brought under
control by the increase in length of the front head bushing and
shank of the machine drill by which, primarily, better alignment of
the drill steel is obtained.
Under the provisions of the Miners' Phthisis Acts Consolidation
Act, No. 35 of 1925, a permanent Committee was appointed to
watch the methods of preventing miners' phthisis already in force
and to investigate any new ideas. Representation on the Committee
is given to all bodies of workers, and it is hoped that the improvements in the future may come from such a body. For the present
the Committee is chiefly concerned in the standardisation of methods
of measurement of the dust contents of the air by the method of
konimetry. It has also conducted certain investigation into the
quantity of dust present in the intake air of the mines and the
increase in dust contents of this air in its passage through the mine.
Difficulties in the maintenance of proper water tubes in machines
have caused the Government Mining Engineer to give notice to the
industry in June 1928 that the development of external water feed
devices should be advanced as rapidly as possible and that the use
of internal water tubes would be prohibited after some future and
possibly early date.
The most recent difficulty is to combat the incidence of tuberculosis, and a Tuberculosis Research Committee is now sitting. It
has promulgated the opinion that " the excessive use. of water
underground may do more harm than good in the efforts towards
the prevention of this disease, and that it certainly is liable to
produce deleterious effects on health in other directions, especially
in the production of tuberculosis, a disease intimately associated
with silicosis ".
To sum up, it may be said t h a t the steps taken to combat miners'
phthisis on the Witwatersrand have been as follows:
1.
2.
3.

The prohibition of promiscuous blasting during the shift.
The prohibition of blasting the cut and round separately on the
same shift in the same development end.
The limitation of blasting (except in a few special circumstances)
to one period only in each day, and the provision of a period of
several hours (from three to seven depending on circumstances)
after each blast during which persons are not allowed in working
places, and the dust and fumes caused by blasting can be swept
away.
The provision of waiting places which can be kept free from dust
and fumes, so that at the end of the shift all workers can be
hoisted without coming into contact with such dust and fumes.

126

5.
6.
7.

PAPERS PRESENTED TO THE

CONFERENCE

The provision of improved water feed drills designed to prevent
the formation of dust in drilling.
Improved ventilation and better distribution of the air available
so as to first dilute and then remove the vitiated atmosphere.
The use of water in all cases for the prevention of the formation
of dust, and for the allaying of such dust as may be formed in
the various operations.

There is also another feature which must have had a most
important effect on the mines of the Witwatersrand, namely, the
establishment of the Miners' Phthisis Medical Bureau for the initial
examination of all persons who wish to commence mining, and for
the periodical examination of those who are engaged in t h a t pursuit.
This matter, however, falls under another heading and will not be
dealt with in this historical review.
In regard to 7 above, namely, the use of water, it may be said
that one of the outstanding features of the preventive measures
which have been adopted on the Witwatersrand is the extent to
which the use of water has been carried. Only a comparatively
short time ago the mines were most prodigal in the use of water,
which, without being exactly wasted, was " slopped about "
everywhere, and no effort made to prevent the mine air becoming
saturated, or nearly so, with water.
Recently, however, and
especially in the hotter and deeper mines, it has been borne in
upon those responsible for their management that water in excess
of t h a t which served a useful purpose was being used, and t h a t
some of the ventilation and other problems connected with deep
level mining were thereby being accentuated, and efforts were
commenced to reduce excessive and unnecessary use of water.
Great care will be necessary in introducing any changes ; for having
educated all operatives in the use of water; having provided the
water at suitable pressure in every working place; and having
encouraged its use by many contrivances, it will not be an easy
problem to limit its use without endangering the effectiveness of
the present organisation. The operatives do, however, require relief
from the lack of cooling power in the ventilation currents of air in
mines working at great depths. Any reduction in the saturation
of the air will be beneficial in this direction. New legislation is
being considered to impose a katathermometer standard on the
management, and methods of mining are already being adopted
which will facilitate the sweep of air up the working place, and
if such a practice can be made general it is possible that the
excessive use of water can be limited without re-creating the dust
evil. A review of the history of the incidence of miners' phthisis

WITWATERSRAND: HISTORICAL

127

REVIEW

cannot close with a claim t h a t it has been overcome. That the
dangers are much lessened is readily acknowledged, but much
yet remains to be added to the sum of human knowledge, and
perhaps not least is the desire to find immunity from this disease
for the operatives, white and black, of the Witwatersrand mines.
This historical review in the changes which have taken place in
the mining conditions on the Witwatersrand would not be complete
without some further reference to the changes which have taken
place in the methods of working vis-à-vis their possible bearing on
the matter of miners' phthisis. The more important of these
changes may be summarised as follows:
1.
2.
3.

5.
6.

The introduction of heavy rigged reciprocating machines operated
by Europeans to replace native hand drillers in the wider and
harder stopes.
The change-over to similar machines of a lighter type operated
by natives under the close supervision of Europeans.
The change-over to machines of the hammer drill or Leyner
type, including the change-over to air-fed hand-rotated hammer
drills. Some of these machines used air only through the drill
steel; others air and water, and some, especially the last mentioned,
solid steel.
The elimination of machines which used air only through the
drill steel and the substitution of machines using air and water
or water only, with the simultaneous introduction of hand-held
hammer drills.
The elimination of all forms of reciprocating drills and drills
using solid steel, and the more general adoption of hand-held
drills of the jackhammer type.
The introduction and general adoption of the cradle as well as
hand-held machines designed to minimise the amount of air
passing down the drill steel and to use as far as practicable
water only.

Simultaneously with the changes enumerated above there has
been a change over from hand drilling to machine drilling. This
change Ì3 illustrated in the following tabulation:
Fathoms broken in straight stoping:
Period : six months ending

31
31
31
31

December
December
December
December

1914
1924
1926
1928

by hand

by machines

52 per cent.
22
12
7

48 per cent.
78 „
„
88 „
„
" "

128

PAPERS PRESENTED TO THE CONFERENCE

There have, of course, been a large number of other important
changes of far-reaching effect, other than the ones referred to
herein, but with the exception of the fact that the mines have
become more extensive, deeper and consequently hotter, these
other changes can have but little, if any, bearing on the miners'
phthisis position.
CONCLUSION

The dust and ventilation problems on the Witwatersrand to-day
can be said to be totally different from those prevailing at the
beginning of this century. The systematic efforts which have been
made since 1911 have resulted in the disappearance, for all practical
purposes, of visible dust underground. Similarly, it can be claimed
that, owing to improved organisation and mechanical ventilation,
exposure to fumes or gases rarely occurs on these fields. Yet the
main problem is far from being solved. The greatest obstacle to
improvements at the present day lies in the fact that the workings
are so far flung and so extensive as to make the cost of adequate
ventilation for sweeping out the remaining invisible dust prohibitive
on most mines.
The natural limitations consisting of the great depth of workings,
narrow reef and large blocks of unpayable ground (particularly
on the Far East Rand) in turn prevent any radical changes in
mine layout.
It must, therefore, be realised that further improvements can
only be gradually introduced. The definitive progress shown in
the past, however, gives rise to the hope that such improvements
will be effected and that thereby the incidence of miners' phthisis
will be further reduced.

THE N A T U R E AND SOURCE OF D U S T
I N MINE AIR, TOGETHER WITH A BRIEF
REFERENCE TO T H O S E O P E R A T I O N S
WHICH PRODUCE D U S T
BY

A. F. McEWEN

(CHIEF CHEMIST AND SECRETARY TO THE TRANSVAAL

CHAMBER OF MINES STANDING COMMITTEE ON DUST), AND J .

BUIST

(SENIOR DUST INSPECTOR, TRANSVAAL CHAMBER OF MINES)

NATURE OF ROCK FROM WHICH DUST IS FORMED

The Witwatersrand System in which the gold mines are situated
consists of a thick body of sediments which are said to have been
derived from the waste of the Swaziland System.
The gold occurs in what are known locally as banket reefs.
These reefs, of which the three principal ones are the Main Reef,
Main Reef Leader, and South Reef, are conglomerate beds of
closely packed vein quartz pebbles having a mean diameter of, say,
from 2 to 3 centimetres, and bound together by a hard siliceous
matrix.
These beds vary in thickness from a few inches to 6, 10 and
even more, feet, and in the main they lie conformably with the
adjoining strata, which may be described as a hard silicified
quartzitic sandstone.
On the Central and West Rand the characteristics of the strata
are much the same on both sides of the reefs. On the Far East
Rand, however, the strata upon which the reef lies is of a finer
grain and less siliceous than elsewhere, and is known locally as
footwall shale.
The matrix of the banket contains a number of minerals, etc. 1 ,
including osmiridium, and, as a curiosity, diamonds, but the most
plentiful mineral is pyrites. The amount of pyrites contained in
the reefs varies from place to place from about 1 per cent, to about
5 per cent., and averages in the neighbourhood of 3 per cent.
1
Cf. R. B. YOUNG, Professor of Geology and Mineralogy at the University
of the Witwatersrand: The Banket of S.A. Gold Fields.

130

PAPERS PRESENTED TO THE

CONFERENCE

The following are typical analyses of the reef and country rock
at various places on the Rand :
FAR EAST RAND
Hanging Wall
(quartzite)

Reef
(banket)

Footwall
(shale)

Per cent.

94.62
2.37
1.14

Si02
A1 2 0 3
Fe203
FeS2
GaO
MgO
Water

88.54
4.31
1.55
1.31
0.57
0.61
-(a)
96.89 (c)

—

0.56
0.15
0.77
99.61 (c)

(o) Water not determined,

(b) Loss on ignition,

62.13
15.24
9.14

—

0.45
7.85
4.27 (b)
99.08 (c)

CENTRAL RAND
Country Rock
(hanging and foot)

Reef
(banket)

Per cent.

Si02
A1 2 0 3
Fe203
FeS 2
CaO
MgO
Water

76.27
14.09
4.71

—

0.23
1.64
2.25
99.19 (b)

(a) Water not determined.

86.22
5.85
1.97
2.19
0.90
0.78
— (a)
97.91 (b)

(¡>) Alkalis not determined.

WEST RAND

Si02
A1 2 0 3
Fe203
FeS 2
CaO
MgO

Water

Country Rock
(hanging and foot)

Reef
(banket)

Per cent.

86.18
5.27
5.00

—

trace
1.07 •
1.54
99.06 (a)
(a) Alkalis not determined.

88.86
2.51
2.13
1.53
1.02
1.06
1.53
98.64 (a)

DUST IN MINE AIR

131

NATURE OF DUST IN MINE AIR

The following is an analysis of the dust accumulated in the
Transvaal Chamber of Mines laboratory from thousands of routine
sugar tube samples of air taken in various parts of every mine on the
Witwatersrand (after treatment with hydrochloric acid to dissolve
out the filter paper ash) :
Si02
A1 2 0 3
Fe203
CaO
MgO
Loss on ignition

Per cent.
80.69
8.58
0.50
2.78
1.40
2.93 (a)
96.88 (b)

(a) Includes organic matter, e.g. hairs from camel hair brush.
(b) Alkalis not determined.

The above analysis does not reflect the presence of certain other
constituents usually found in mine air, as revealed on konimeter slides
under the microscope—for instance, water residue salts and carbon.
The water residue salts are derived from the atomisation of the
mine water used underground, and the carbon particles from the
candles and acetylene lamps.
In the case of a sugar tube or gravimetric sample the water
residue salts are washed out, and the carbon particles are eliminated
by the subsequent ignition, along with the organic matter of the
filter paper used.
A konimeter spot, on the other hand, when viewed under the
microscope shows up all the particles of whatsoever nature which
were in the air sampled, and which were caught on the slide.
Until quite recent years, and before means had been devised for
the elimination of such contaminating particles, the counts of konimeter spots were liable to serious error. Accurate counting of the
silica particles was oftentimes impossible. This matter, however,
will be referred to elsewhere.
SOURCES OF DUST

The principal operations which cause dust underground are:
1.
2.
3.
4.
5.

Blasting.
The shovelling of broken rock.
The movement of rock in ore passes, ore bins, and the like.
Machine drilling.
Hand hammer drilling.

132

PAPERS PRESENTED TO THE CONFERENCE

PHYSICAL NATURE OF DUST ARISING FROM THE ABOVE-MENTIONED
SOURCES

1. Blasting
Blasting produces large quantities of dust of all sizes. The
larger particles soon settle and are caught by damp surfaces or by
water blasts in development ends. Most of the other particles are
swept away by the mine ventilating currents during the interval
which elapses between blasting time and the time for resuming
work, and it may be said the residual dust which may be left in the
mine air currents is chiefly fine dust of the order of about one
micron.
2. Shovelling
This work produces some coarse particles of dust, but the average
size of the particles is from 2 to 3 microns and under.
3.

Ore Passes, etc.

Dust from these sources is readily recognisable under the
microscope, since it is usually made up of particles of from 3 to
5 microns and over, mixed with but little fine dust.
4.

Machine Drilling

The dust from this source is usually fine, that is to say up to
only 2 microns, with a few coarser particles.
5. Hand Drilling
The dust from this source is similar in appearance to that
produced by machine drilling, but konimeter counts are usually
lower.
AMOUNT OF DUST IN MINE AIR

The following tabulations (A, B and C) show the amount of
dust in various places, and in different years, as determined in the
manner stated :

TABULATION A. — SHOWING THE AMOUNT OF DUST IN MINE AIR, EXPRESSED IN MILLIGRAMS PER CUBIC METRE, AS
DETERMINED FROM SAMPLES TAKEN THROUGH THE MEDIUM OF SUGAR TUBES BY THE DUST INSPECTORS OF THE
TRANSVAAL CHAMBER OF MINES IN VARIOUS PLACES IN EVERY MINE

Place

1915

1916

1917

1918

1919

1920

1921

1922

1923

1924

1925

1926

1927

1928

1929'

Main travelling ways

2.8

1.7

1.6

1.2

1.4

0.8

0.9

0.7

1.3

0.7

0.6

1.1

0.9

0.5

Development ends

6.9

5.8

5.4

4.4

3.5

2.9

2.3

2.4

1.9

1.2

1.0

1.1

1.2

0.8

Shafts

3.6

4.7

3.7

2.9

4.8

4.9

2.5

2.8

2.1

0.4

0.8

1.3

1.2

0.9

0.7

Stopes

3.4

2.7

2.9

2.2

1.9

1.7

1.3

1.2

0.9

0.7

1.0

0.9

0.6

0.7

Ore passes and bins

4.4

4.0

4.2

3.7

2.9

2.7

2.1

2.2

1.8

2.0

1.6

1.8

1.9

1.5

2.0

Sundry

3.7

5.0

4.0

3.0

2.5

2.0

1.4

1.3

1.2

1.4

0.8

1.0

0.6

4.9

3.9

3.8

2.9

2.4

2.0

1.6

1.3

1.1

0.9

1.2

0.8

1.0

2.6

1.4

1.9

1.4

1.2

0.7

0.6

0.8

0.5

0.8

0.4

0.5

1.4

1.6

1.3

1.1

0.9

1.0

0.6

0.7

0.6

0.5

1.0

0.7

0.3

0.6

General average
Upcast
Downcast
Total number of
samples analysed

1,860

5,155 6,359 7,547 7,641 7,206 6,885 4,632 4,855 1,071
1

Jan. to Aug. Inclusive.

2,390 2,587

2,843 2,663 1,351

TABULATION B . — SHOWING THE AMOUNT OF DUST IN MINE AIR, EXPRESSED IN MILLIGRAMS PER
DETERMINED FROM SAMPLES TAKEN THROUGH THE MEDIUM OF SUGAR TUBES BY THE MINE

CUBIC METRE, AS
DUST INSPECTORS

IN VARIOUS PLACES IN EVERY MINE AND ANALYSED IN THE LABORATORY OF THE TRANSVAAL CHAMBER OF MINES

1916

Place

1917

1918

1919

1920

1921

1922

1923

1924

1925

1926

1927

1928

1929

•13

>
13
M
58

Main travelling ways

—

2.3

2.0

1.5

1.2

0.8

0.5

0.6

0.8

0.7

0.8

0.7

0.6

0.7

Developments ends

6.0

4.4

3.6

2.5

1.9

2.1

1.7

1.5

1.1

0.9

0.8

0.7

Shafts

5.8

3.3

5.5

3.0

3.6

2.5

0.3

3.2

1.8

1.5

1.4

1.1

1.2

0.8

Stopes

4.8

2.9

2.2

1.6

1.2

1.3

1.0

0.9

0.8

0.9

1.0

0.8

0.7

•a

in
M
2
1-3
M

i-ä

Ore passes and bins

5.5

3.9

3.4

2.3

1.9

2.0

1.6

1.7

1.6

1.2

1.1

Sundry

4.7

2.6

2.5

2.0

1.5

1.6

0.9

0.8

1.0

0.8

0.7

a
m

5.2

3.4

2.8

2.0

1.5

1.6

1.2

1.0

1.1

0.9

0.8

52
TI
H
53

General average
Upcast

3.4

2.1

1.6

1.2

0.7

0.8

1.1

0.5

0.6

0.7

0.6

Downcast

5.5

1.8

1.9

1.1

0.9

1.2

0.5

0.7

0.6

0.7

0.8

0.7

0.6

o
m
a
Pi

Total number of samples
analysed

5,261 14,362 27,460 27,508 25,821 23,739 16,259 24,709 25,268 24,616 25,796 26,212 26,228 15,195
1

Appointed under Mining Regulation No. 161/10.

Jan. to June inclusive.

TABULATION C. — SHOWING THE AMOUNT OF DUST IN MIÑE AIR, EXPRESSED IN PARTICLES PER CUBIC CENTIMETRE,
AS DETERMINED THROUGH THE MEDIUM OF KONIMETER SPOTS TAKEN BY THE DUST INSPECTORS OF THE TRANSVAAL
CHAMBER OF MINES IN VARIOUS PARTS OF EVERY MINE
1919

1920

1921

1922

1923

1924

1925

1926

1927

1928

1929 i

Light ground
D a r k ground
Subdued reflector light

Full
reflector
light

Illumination
1.4 Condenser

1.2 Condenser
Acid immersion

None
Acid vapour
Treatment
Ignition
Development ends
Shafts
Stopes
Ore passes and bins

490
468
270
240

324
303
165
129

211
303
128
155

268
167
111
154

385
261
182
185

623
361
319
289

498
420
384
356

351
242
267
240

306
378
251
246

138
120
121
146

78
78
63
105

166
109
135
247

General average
I n t a k e air

318

192

163

149

230

387

409

284

263

128
106

73
47

159
89

6,218

5,916

6,062

4,373

4,695

3,526

1,064

2,240

2,367

2,660

2,270

1,301

Total n u m b e r of spots

Jan. to Aug. Inclusive.

TABULATION D. — GIVING A FEW TYPICAL ANALYSES OF MINE WATERS EXAMINED IN THE CHAMBER OF MINES LABORATORY

Far East Rand

Locality

Central Rand

CO
03

West Rand
Tí

Appearance

Cloudy

Reaction

Alkaline

Muddy
(rust)
Acid

Clear

Muddy

Turbid

Cloudy

Muddy

Cloudy

Clear

Alkaline

Acid

Alkaline

Per cent. H2S04

—

.003

—

.012

.026

.023

.042

—

Percent. NaOH

.003

—

.002

—

.030

.004

Insoluble mineral
residue: grammes
per litre
Particles under
12 microns:
grammes per litre
Percentage of
particles under
12 microns
Remarks

>
m
v
03

M
m
M

a
M
Ö

.149

.054

.016

.298

.046

.026

.051

.050

.030

1-3

O
•3

a
m
.052

.018

.004

.070

.014

.009

.015

.028

.006

a
O

a
35
Unsuitable

33
Unsuitable.
Requires
clarification

25
Very
good

24
Unsuitable

30
Passable

35
Very
good

29
Unsuitable.
Requires
clarification

56
Passable

20
Very
good

TI
M

58
M

a
o
M

DUST IN MINE AIR

137

W A T E R USED FOR DUST PREVENTION AND ALLAYING

The Mining Regulations lay it down that the manager shall, for
dust prevention and allaying purposes " . . . . provide an
adequate and constant supply of water which is clear and odourless
. . . . ", and the Transvaal Chamber of Mines Standing
Committee on Dust laid it down in 1916 t h a t water containing
more than 0.05 grammes of insoluble mineral residue per litre
should not be used with water fed drills or atomisers, and when
water was so used it should be periodically analysed in the Chamber's
laboratory.
Tabulation D gives a few typical examples.
NATURE OF A D A Y ' S W O R K

UNDERGROUND

The work performed underground by a European will, of course,
vary in accordance with the class of occupation in which he is
employed. It may, however, be said that the European miners
on these fields are occupied mainly in directing and supervising
the work of natives, and it is proposed herein to follow the course
of a day's work of a man engaged in ordinary mining, pointing out
where the various operations produce dust, and making brief
reference to the methods employed for its suppression.
When a miner enters his working place his first duty is to
ascertain whether it is safe, and, if not, to cause it to be made safe.
His next, and really simultaneous duty, is thoroughly to wet the
roof and sides for a distance of 25 feet from where any work is to
be performed. Both these operations at first, especially where
water blasts are not used, raise a certain amount of dust, in the
same way as water applied to a road from a watering cart tends
to stir up dust.
In making safe some mines have used hollow punch bars attached
to a water hose, so that water under pressure emerges from near
the end of the bar. These bars, however, are not popular with
the miners since they are not so readily handled, and since there is a
tendency for the water to run back down the arm of the operator.
A place having been made safe in accordance with the various
provisions of the Mining Regulations, the ordinary work of drilling,
shovelling, and, if necessary, timbering, is commenced.
Most of the dust caused by drilling escapes during the small
interval of time occupied in starting a hole, say during the drilling

138

PAPERS PRESENTED TO THE CONFERENCE

of the first inch or two. This escape can be considerably reduced
by playing from a hose a stream of water on to the rock being
drilled, in addition to the ordinary supply which comes through
the drill steel.
The following figures, which represent the average of a considerable number of special tests, reflect this reduction:
Particles per
cubic centimetre
Dust found in collaring when extra hose is not used .
75
Dust found in collaring when using extra hose . . .
49

After the miner has marked out the holes to be drilled and
generally started his natives to work, he proceeds to perform
sundry other duties, namely, the collection of his supply of explosives
from the shaft station ; the preparation of his charges ; the marking
of his native labourers' work tickets, and so on, exercising in the
meantime a certain amount of supervision on the progress of the
work generally.
The following time studies of certain classes of underground men
were made during from May to August inclusive 1926 at the request
of the Mines Department, and will serve to give an idea of how
these classes of employees occupied an average shift:
At
stations
and
travelling
to and
from
working
place

Inspecting
banging
and
generally
supervising
at the
face

At
miners'
box

Charging
and
lighting
up

Total

Percentage of total time

Shaftsinkers
Developers
Machine stopers
Average

9.7
11.4
12.2

55.1
44.3
58.6

21.8
28.5
17.4

13.4
15.8
11.8

100
100
100

11.3

51.6

23.2

13.9

100

There has been no material alteration in methods of working
since the dates upon which these studies were made, and they can
be taken as representative of present day conditions.
After each hole has been drilled, and some time before the end
of.the shift, it is necessary that the holes shall be thoroughly cleaned
out before the charge of explosives is put into them. Some miners
cause each hole to be cleaned out immediately after it is drilled;
others wait until just before charging time.

DUST IN MINE AIR

139

Until recently this cleaning out was done by compressed air
applied through a pipe to the bottom of the hole for the purpose
of blowing out all the mud and water in it. The more recently
introduced method is first to wash out the holes with water under a
considerable pressure through a pipe and then to dry the holes by
causing the water to be sucked out by an ejector using a water jet
as its source of power. By this method no compressed air is used,
and less dust is projected into the mine air.
The following figures, which again represent the average of a
number of tests, show the different amounts of dust produced by
the two methods:
Milligrams
per cubic metre
Dust found in blowing out 5 holes with air blow pipe . .
45.9
Dust found when cleaning the same number of holes
with water method
1.7

In considering these sources of dust, however, it must be remembered that either method occupies but a relatively short space of
time, and that if, as is usually done, the sequence of blowing out
the various holes is arranged in a direction against the ventilating
current, the dust caused by the operation is quickly removed and
does no harm to anyone.
While drilling is in progress the other operations of mining, such
as shovelling the broken rock and loading it into trucks ; timbering;
track laying; pipe laying; track cleaning, and so on, are also
performed. The Regulation already referred to, which requires
everything within a distance of 25 feet from a point at which work
is being done to be wetted and kept wet, has the effect in practice
to cause in stoping the area between the whole length of the stope
face and a distance therefrom of 50 or more feet to be wetted and
kept wet, and in development work that practically the whole
length of the heading shall be so treated. This being the case,
the operations referred to, with the exception of the handling of
the broken rock, cause little or no. dust.
Various methods of handling the broken rock are in vogue to suit
different conditions, the dip of reef, etc., but ultimately in all cases
the ore is loaded into trucks and taken to ore passes and/or ore bins,
whence it is loaded into the shaft conveyances and hoisted to the
surface. Although the rock is kept wet during the process of
handling and loading it can readily be understood that these
processes cause a certain amount of abrasion of the rock and a
consequent escape of dust. Particularly is this the case in ore

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passes where the rock has to fall, roll or slide through considerable
distances, and where the rock is being tipped from or loaded into
trucks or other conveyances. In these cases a successful way of
combating the dust is to provide sprays and to ensure as far as
practicable that the ore passes, bins, etc., shall never be entirely
empty, but shall always contain enough ore to prevent a free
current of air which in passing through them might carry the dust
into the main ventilating currents of the mine; also to provide a
secondary ventilation system which by means of suitably sized
pipes will draw off the dust and by-pass it into the return airways,
or if this is not possible, into an air filter of some kind.
Various types of filters have been tried, and while some of them
have proved moderately efficient as dust traps, the expenditure of
power in relation to the quantity of air filtered is so great that they
are only used in places where the dust-laden air can be treated in
no other way. One such filter consists of several large sheets of
moist flannelette through which the dust laden air is forced at low
velocity by a fan. In some cases old workings are used as filters,
with excellent results, but such use is not always practicable.

METHODS FOR D E T E R M I N I N G T H E D U S T
IN MINE AIR, AS PRACTISED ON
THE WITWATERSRAND
BY

JAMES BOYD, A.R.T.C. (GLAS.), F.i.e., F.es., A.M.S.A.I.E.

To the best of our knowledge the fir3t determinations of dust
in mine air on the Witwatersrand were carried out for the Miners'
Phthisis Commission of 1902, with the following results:
Place
Face of drive
do.
do.
do.
do. behind spray
100 ft. from face after blast
End of drive 5% hours after blast
Stope
Stope
Raise

Dust in milligrams
per cubic metre
424
192
42
83
43
14
32
164

In 1910 the East Rand Proprietary Mines found as much as
1,500 milligrams in a drive.
In 1911 the systematic determination of dust was begun by
the Consolidated Gold Fields Group. The method adopted was
a gravimetric one, a known quantity of the mine air being drawn
through a column of pure sugar, the sugar being then dissolved
in distilled water, and the dust filtered off, ignited and weighed.
The dust-laden air was aspirated through the sugar (which was
contained in a tube) by various methods, the one generally adopted
being to use a double-acting suction pump.
The capacity of the standard pump is about 3 litres per double
stroke, the pump being calibrated against a standard wet meter.
The tube used to contain the sugar is made of thick walled glass
tubing, 5 inches in length by l 1 ^ inches in diameter, fitted at

142

PAPERS PRESENTED TO THE CONFERENCE

the top with a solid rubber cork, and at the bottom with a oneholed rubber cork, through which passes a piece of glass tubing
1
/ 2 inch in diameter. At the bottom of the sugar tube is placed
a small piece of cotton wool, this being used to prevent the sugar
being drawn out in sampling. The sugar used is of such a size
that it will pass a ten-mesh sieve and remain on a twenty-mesh
sieve, and 40 grammes of the sugar is used per tube.
In taking a sample the tube is connected by a length (usually
6 feet) of pressure tubing to the inlet of the suction pump, and
the required volume of air aspirated. This volume depends on
the dustiness of the air, but is usually 1 / 3 to 1/2 cubic metre.
The tube is held at about the height of a man's mouth, and
the sampling is done to windward of the pump, the tube being
moved about so as to obtain a representative sample. After
sampling, the tube is recorked, numbered, and a record made of
the place sampled and the work in progress. The tube is then
returned to the laboratory for analysis.
Up to 1913 all the dust found in a sample was regarded as
dangerous, and was returned as total dust. The research of
Dr. J. McCrae, however, proved that in the ash of a silicotic lung
it was only the very fine dust that was found, the particles ranging
in size from 12 microns downwards.
As the sugar tube determinations were of all the dust in the
air, it became necessary, therefore, to devise some method of
separating the coarse from the fine dust.
In 1915 Dr. J. Moir published details of a method for the
separation of large and fine quartz particles. The method consisted
of allowing dust in suspension to settle in water for a period of
time, calculated from the size of the particles and from the rate
of fall of quartz particles when suspended in water. The formula
is as follows:
V = = _Z5L

100000
where V = velocity of fall in cm. per second.
D = diameter in microns.

In practice, the procedure to settle out particles above
12 microns in size was to allow the well-mixed suspension of dust
to settle for four minutes for each centimetre of height of the
liquid in a straight-sided beaker, siphon off the supematent liquid
{containing the fine dust in suspension), make up the residual
liquid to the original bulk, allow to settle for two minutes for

WITWATERSRAND : DETERMINATION OF DUST

143

each centimetre of height, siphon off, mix the two siphoned-off
liquids, filter and weigh the dust.
In dealing with large numbers of samples, the time involved
in this process was very great, and recourse was made to a
mechanical method. It became possible to obtain very fine
screening of some 350 mesh. A small truncated cone was made,
the screening forming the base of the cone, and the sugar solution
containing the dust was filtered through the cone on to a fine
filter paper. The cone is then washed free of sugar solution,
removed, and the filter paper containing the dust is then
incinerated in a crucible, cooled, weighed, and the weight of
dust determined.
As all sugar contains a certain amount of inorganic dust, it
is necessary to make an allowance for this as well as for the
weight of the filter ash. This is done by running a number of
blank sugar tubes, which are treated in the same way as the tubes
containing dust and the weight of dust found is taken as the
weight of dust in the sugar plus the weight of the filter paper
ash, the amount usually being about 0.7 milligrams per sample.
The amount of dust found in mine air is returned as milligrams
per cubic metre.
The method described above gives the weight of dust in a given
quantity of air. It is, however, necessary to have a knowledge
of the number of particles of dust in the air. This can be determined in a gravimetric sample by counting the dust in an aliquot
part of the solution by means of a Haemocytometer or similar
instrument; but this is a tedious method.
In 1916 Sir Robert Kotze, Chairman of the Miners' Phthisis
Prevention Committee, devised an instrument to enable the
particles of dust in mine air to be counted. This instrument,
known as the Konimeter, consists of a valveless cylindrical suction
pump of a cylinder capacity of 5 to 10 cubic centimetres. In
this instrument a piston is depressed and held by a catch, and
when it is released a volume of 5 cubic centimetres of air is sucked
in through a nozzle, which is tapered and smoothly bored, with
an orifice diameter of 0.6 millimetre. The air sucked in impinges
on a glass slide which is placed 0.5 millimetre from the nozzle.
The slide is made by cutting an ordinary microscope slide in half,
and is held in position over the nozzle by means of a spring, the
jet itself being surrounded by a rubber ring about 16 millimetres
in diameter. This forms, with the slide in position, a small airtight chamber. The slide may be moved over the chamber so

144

PAPERS PRESENTED TO THE

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that samples of dust may be taken. The slide may be coated
with a very thin coating of vaseline or glycerine jelly, or, if the
sample is being taken in moist air, may be uncoated with any
adhesive. The velocity of the air when it leaves the nozzle should
be not less than 30 metres per second. To count the particles
of dust in the spot, the slide is examined under a microscope,
using a 16-millimetre objective, and an eye-piece of high power.
An eye-piece micrometer ruled in sectors is used, the most usual
sectors being either 9° or 18°. The spot is counted vertically and
then the eye-piece is rotated through 90° and the spot counted
again, the sum of the two counts giving the number of dust
particles when 5 centimetres of air has been impinged.
A modified form of Konimeter is also used. In this instrument
the glass plate on which the dust is caught is made circular and
fitted into a toothed wheel which engages a pinion. By means
of this device the plate is made to revolve under the jet and as
many as sixty spots can be taken on the one slide. When the
plate is removed from the Konimeter it is fitted into a special
holder on the stage of the microscope, and by means of a toothed
pinion is revolved under the objective so that each spot in turn
comes into focus and can be counted.
When the Konimeter was invented, counting was done by
means of ordinary reflected light, but it was soon found that, as
the particles of dust are extraordinarily minute, they could not
all be counted by this means. After much experimenting a
method was evolved which is a modification of dark ground illumination. The method has for its object the securing of contrasts,
and therefore a spot is used which allows the maximum illumination. In practice this is obtained by placing a dark ground
spot of 10 millimetres diameter immediately below the condenser.
This cuts out the central portion of the light pencil and allows
the particles of dust to stand out clear, bright and easily countable.
Illumination is obtained by using a 100 candle power ^ - W a t t
ground glass bulb, which is placed about 9 inches from the mirror.
Just as the gravimetric sugar tube collects all the dust in the
air, irrespective of size, so does the Konimeter collect the dust
irrespective of kind, and irrespective of its nature.
It has been pointed out by Dr. Mavrogordato that all instruments
delivering air at a high velocity through a narrow jet bring in the
condensation principle, and that the resultant spots are not only
precipitation spots but also condensation spots, so that if the
moisture in the air contains salts in solution, these will materialise

WITWATERSRAND : DETERMINATION OF DUST

145

as visible particles when the spot on the Konimeter is examined
under the microscope. This does happen in the sampling of mine
air by the Konimeter, and has been a source of error and of great
trouble in Konimeter work on these fields.
Water used for dust allaying almost invariably contains soluble
salts, and, as the air underground is more or less saturated with
moisture, a Konimeter spot contains salts of sodium, calcium and
iron. The Konimeter appears to exert a selective action in its
collection of dust particles, and these are always of very small size.
The soluble salts in the moisture in the air crystallise out in very
minute crystals, and are nearly always indistinguishable from the
quartz particles. Here then we have a source of very considerable
error.
In addition, the illumination of the underground workings is by
means of acetylene lamps and candles. Acetylene, as is well known,
burns with a smoky flame, and large amounts of carbon in a very
fine state of division are liberated, so much so that the gravimetric
or sugar tube sample is often stained black by the carbon. The
carbon particles by semi-dark ground illumination appear bright
and shiny like the silica particles, and it is impossible to differentiate
the one from the other. As far as our knowledge goes, carbon
particles are not dangerous when breathed into the lung, and as in
some places they are present in very large quantities in mine air,
if counted in the Konimeter sample with the silica dust, an entirely
wrong idea of the dangerousness of that particular sample of mine
air would be obtained. Here there is another source of error in
counting dust particles.
Experiments were conducted for some time in an endeavour to
eliminate the soluble particles from the Konimeter samples,
and a method devised by Mavrogordato, Moir and Ray proved
satisfactory. These investigators found that most of the soluble
particles could be removed by the action of hydrochloric acid
vapour, which did not touch the silica.
The method adopted was to insert a watch glass over the spot,
the watch glass having in its centre a small segment of filter paper
saturated with a 15 per cent, solution of hydrochloric acid. In
the case of spots on circular slides a rubber ring is placed round the
periphery of the slide and a spare glass slide with the saturated
filter paper in the centre placed on top of the ring, thus forming a
small chamber with an atmosphere of hydrochloric acid gas. By
this means most of the soluble salts were dissolved, but, unfortunately, not the carbon particles.
10

146

PAPERS PRESENTED TO THE CONFERENCE

In 1927 McEwen and Thompson tried immersing the whole slide
in a dilute solution of hydrochloric acid, washing in distilled water
and drying. Instead of this somewhat drastic treatment removing
the whole spot, they found that on examination under the microscope the particles on the spot shone up clear and bright with no
trace of contamination by either carbon or soluble salts; the silica
in fact looked clean and polished.
Many experiments were made to see if there were any loss of
silica particles, but the results in many cases showed an increased
count after treatment, as if some of the silica particles had been
masked by carbon in the original count.
In 1925, on my suggestion, an attempt was made to eliminatecarbon from the spots by ignition, using heat-resisting glass in
the slide, but unfortunately it was not then possible to obtain a
sufficiently transparent glass.
Recently it has been found possible to obtain a glass with heatresisting properties which is also transparent under the microscope and free from flaws. McEwen and Thompson have made a
large number of experiments with encouraging results. Theslides are made of Chance's heat-resisting glass. On to the centre
of the slide is poured a few cubic centimetres of the acid, and
this is allowed to spread all over the slide covering the spots.
The slide is then immersed in a basin containing distilled water,,
the washing being repeated twice, and finally the slide is immersed
in. hot distilled water and allowed to dry. The slide is then placed
on a smooth fireclay tile in a cold gas muffle, and the gas lit. The
muffile is kept at a dull red heat for thirty to twenty-five minutes,.
then the gas is turned off and the slide allowed to cool in the
muffle. The silica particles when examined under the microscope
after this treatment are clear and bright, and in many cases show a
much larger count than before treatment.
This new method represents a very great advance, and enable»
more reliance to be placed on the accuracy of Konimeter samples.
SYSTEMATIC DUST SAMPLING ON THE WITWATERSRAND

Previous to 1913 no attempt had been made to determinesystematically the amount of dust in the air of the mines of the
Witwatersrand. In December of that year the Miners' Phthisis
Prevention Committee, which had been appointed by the Government, caused the first dust survey of the mines to be carried out.

WITWATERSRAND:

DETERMINATION

OF DUST

147

The samples were all taken by the gravimetric method, and gave
the following results:
Milligrams
per cubic metre
5.4
6.1
9.1
5.0
5.5
4.2

General average
Drives
. . . .
Raises
. . . .
Winzes . . . .
Ore bins . . .
Stopes
. . . .

In May 1914 the Chamber of Mines established a department
to investigate the dust conditions of the mines, and to suggest
methods of preventing the formation of dust and its dissemination into the air of the minee. Visits were paid to each mine,
and samples taken in as many of the working places as possible.
Tests were made of various kinds of work likely to produce dust,
and suggestions made for bettering conditions.
Since 1914, fifty-eight systematic dust surveys were made,
showing the following results:
1915

General
average 4.9
Development
6.9
Stopes
3.4
Ore bins
4.4
Percentage
over 5 mg. 27.0

1916 1917 1 9 1 8 1 9 1 9 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929

3.9
5.8
2.8
4.0
23.0

3.8
5.4
2.9
4.2

2.9
4.4
2.1
3.7

2.4
3.5
1.9
2.9

2.6
2.9
1.6
2.7

1.6
2.3
1.2
2.1

1.6
2.4
1.2
2.2

1.3
1.9
0.9
1.8

1.1
1.2
0.7
2.0

0.9
1.0
0.7
1.6

20.0 13.0 10.0 8.0 4.0 4.0 3.4 2.5 1.7

1.2
1.1
1.0
1.8

1.2
1.2
0.9
1.9

0.8
0.8
0.6
1.3

1.0
0.8
0.7
2.0

1.1 1.2

1.2

1.9

It will be noticed from the above table that there is a steady
diminution in the quantity of dust found in the various sections
into which mine work is divided. Taking 5 milligrams per cubic
metre as the danger mark, it will be noticed that whilst in 1915
27 per cent, of the samples were above that limit, it had fallen in
1928 to 1.2 per cent, and in 1929, owing to some high samples at ore
bins, was 1.9 per cent.
In 1916 it was decided to appoint an official on each mine
to investigate and report on the dust conditions, as it was recognised
that the staff of inspectors appointed by the Chamber of Mines could
not be expected to pay sufficient attention to all the working places
on the mines. These inspectors were expected to pay surprise visits
to see that things generally were in good condition.
The mine officials took samples in the same way as the Chamber's

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officials, and all the samples were analysed in the Chamber's
laboratory. The following table shows the more important of the
results obtained:
1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928

General average
Development
Stopes
Ore bins

5.2
6.0
4.8
5.5

3.4
4.4
2.9
3.9

2.8
3.6
2.2
3.4

2.0
2.5
1.6
2.3

1.5 1.6 1.2
1.9 2.1 1.6
1.2 1.3 1.0
1.9 2.0 1.6

1.2
1.5
0.9
1.8

1.0
1.1
0.8
1.6

1.1
1.2
1.0
1.6

1.1
1.1
0.9
1.2

0.9
0.9
0.8
1.2

1929
(6
mthg.)

0.8
0.8
0.7
1.1

It will be noticed that the improvement in dust conditions
indicated by the samples taken by the Chamber inspectors is
corroborated by those taken by the mine inspectors.
KONIMETER

SAMPLES

Since 1919 Konimeter samples have been taken as a matter of
routine at the same time as the gravimetric samples.
Until June 1923, all the samples were counted by light ground
illumination, with the following results:

Development
Stopes
Ore bins
General average

1919

1920

1921

1922

1923

490
270
240
318

320
165
160
190-

211
130
150
160

270
110
150
150

390
180
190
230

As before stated, dark ground illumination was introduced in
July 1923, and the following results were obtained:

Development
Stopes
Ore bins
General average

1923

1924

1925

1926

620
360
280
380

480
390
350
410

350
260
250
280

310
250
250
270

In 1927 the McEwen-Thompson method of treating the slides for
the removal of soluble particles and particles of carbon was introduced, with the following results:

0.8
0.8
0.7
1.1

WITWATERSBAND : DETERMINATION OF DUST
1927
132
119
142
125

Development
Stopes
Ore bins
General average

149

1928
78
62
105
73

In 1929 the ignition method of treating the slide was introduced
and in addition the spots were counted by using the fullTreflectors
of the microscope instead of subdued light.
Results
Development
Stopes
Ore bins
General average

1929
Particles per c.c.
165
135
247
159

CONCLUSIONS

The figures given show that there has been a vast improvement
in the amount of dust present in mine air in 1929 as compared with
1914.
It may be asserted that neither of the two methods of sampling
dust in mine air used on the Witwatersrand are methods which can
claim any scientific accuracy. The errors which can be, and are,
introduced through no fault of the operator are such as to render
any claim to real accuracy untenable. The gravimetric method,
sampling as it does all sizes of dust in the air, can easily be made
to show very serious dust conditions by the presence of a few
large (in the microscopic sense) particles of dust, whilst innumerable
small dangerous particles of very light weight will not be reflected
in the results obtained. The difficulty of separating the gravimetric sample into large (in the microscopic sense) and fine dust is
so great that it is not practicable in ordinary routine work. On the
other hand, as an indication of the dust conditions, the gravimetric
method is useful and has done good work. The vast improvement
in underground conditions on the mines of these fields can be
traced to the results of gravimetric sampling as showing the
condition prevailing.
Despite its faults and errors, the fact that, by the same method
as was used in 1914, the average dust content of mine air has
fallen from over 5 milligrams per cubic metre to round about
1 milligram, is an indication of the good work performed as the
result of using the gravimetric method to call attention to bad
conditions.

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The Konimeter method has also its faults and errors, some of
which have been already mentioned, such as its showing up all dust,
whether dangerous or not, and its liability to contamination by
carbon particles.
The result of long and painstaking research work indicates
that it may be possible in the future to obtain a sample by the
Konimeter method which will be a true indication of the amount
of dangerous dust in the mine atmosphere.
In the meantime we can say that by using both methods we can
obtain results which, if interpretated in a relative manner, give
us a good indication of the dustiness, and consequently of the
dangerousness from a phthisis-producing point of view, of the air
of the mines. By using these methods and remembering that
neither give accurate results, but rather results which are only an
approximation to absolute accuracy, we can still hope for further
improvement in the dustiness and ventilation of the mines.

MEASURES FOR PREVENTING THE
F O R M A T I O N OF D U S T , A N D P R E C A U T I O N S
DESIGNED TO PREVENT PERSONS INHALING
SUCH D U S T A S MAY BE F O R M E D , A N D T H E
REGULATIONS RELATING THERETO1
BY

MALCOLM FERGUSSON, CHIEF INSPECTOR OF MINES, UNION OF SOUTH
AFRICA, AND WALTER SCOTT, ASSISTANT CONSULTING ENGINEER,
CENTRAL MINING-RAND MINES GROUP OF MINES

M I N E R S ' PHTHISIS COMMISSION'S

FINDING

Little, if anything, had been done in the way of taking precautions
to prevent persons from inhaling dust before the sitting of the
Miners' Phthisis Commission in 1902-1903.
The finding of the Commission was that miners' phthisis was
contracted as the result of miners inhaling dust-laden air, and the
disease was to be found chiefly among rock-drillers in development
ends, especially when employed on raising.
SOURCES OF D U S T PRODUCTION

The chief sources of the dust inhaled by developers were as
follows :
(a) The drilling of dry holes in raises and drive ends. In the
former all the holes were drilled dry, in the latter the two top holes
were drilled dry as well as the bottom cut holes. Holes inclined
downwards had water poured into them by hand sufficient t o
prevent the drill from sticking. Samples of air taken close to the
rock drill machine whilst boring a dry hole showed that there were
0.185 and 0.0839 grains per cubic foot of air respectively, and an
1

The following notes will serve to give the reader a working knowledge
of the steps which have been taken on the Witwatersrand on the subject
matter of these notes. They will be found in some respects to overlap
certain portions of the Historical Review of Mining Conditions on the
Witwatersrand, p. 107, but this is clearly unavoidable.

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PAPERS PRESENTED TO THE CONFERENCE

analysis of air taken in a raise in similar circumstances gave as
a result 0.072 grains per cubic foot.
(b) The method of blasting in development ends considered,
at t h a t time, to be necessary for obtaining good results.
It was the practice of the miner to charge up the cut holes
completely, and the remaining holes partially, then to blast the
cut and return to the end after a very short interval; he then
completed charging up the remaining holes, i.e. put in the primer
cartridges and tamped the charge, and blasted the round. Miners
were even known to return after blasting the round to see how it
had broken.
PRECAUTIONS

Among the first precautions taken to prevent the dust formed in
drilling and blasting from being inhaled by the miner, was the use of
inhalers and respirators.
Dr. Aymard's inhaler was a close-fitting mask placed over the nose
and mouth of the rock-drill operator. This mask was connected to the
air-cock operating the machine, whereby compressed air was supplied
to the miner by means of a light flexible metallic tube about 6 inches
long. It was not necessary for the mask to fit perfectly as the constant
pressure of air prevented the ingress of dust. The objection raised to
this form of inhaler was : first, the range of the wearer's movements was
limited to the length of the flexible tubing; second, air from the compressors, at that time, occasionally contained dangerous quantities of
CO and C0 2 due to having unsuitable lubricating oil in the compressors.
There were various makes of respirators used by the miners. The
essential points which a respirator has to fulfil to be considered satisfactory were as follows:
(a) It must fit closely to the face so that the whole of the inspired
air would pass through the filtering material and not shortcircuit between the face and the side of the mask.
(b) The filtering material must be capable of arresting all the minute
angular particles of dust in the air, but should not impede
respiration.
(c) The mask must be fitted with an outlet valve through which
the expired air can escape freely.
From the original trials made with respirators, they were considered
to have sufficient merit to permit the miner to return to the end of a
drive shortly after blasting the cut to complete blasting the round,
provided he wore a respirator. This was embodied in an addition to
Regulation No. 146 of the Mines and Works Regulations gazetted on
29 December 1905, viz.:
(6) After blasting in any end, raise or other place, no person shall
return to that place until after the lapse of at least half-an-hour
unless the air in such place has been cleared of the dust and smoke
arising from such blasting, by efficient ventilation or other special
means, or unless an efficient respirator or other apparatus is used
to prevent the inhaling of such dust or smoke.

DUST PREVENTION AND RELATIVE REGULATIONS

153

Also Government Notice No. 1278 of 1908, 146 (11), permitted a
miner to enter a development end containing dust and fumes provided
he wore a respirator. This practice was permissible until 30 October
1913.
The use of the respirator seemed a simple and effective solution of
the whole matter, but it proved impracticable. The miners as a whole
were averse to the use of respirators chiefly, perhaps, on account of the
discomfort attending their use, e.g. extra effort required to inhale
through the filtering material when working hard, and interference
with speech and smoking. The valve was usually made of mica and got
out of order very easily, so that the miner invariably replaced it by a
piece of sponge. This was objectionable as it did not permit of the free
escape of the CCyand moisture exhaled.
It was eventually ascertained that the filtering material did not
arrest the very fine dust particles in size 10 microns and under, which
were the most harmful, and the use of respirators was rapidly abandoned.
It is interesting to note here that in 1902 the Transvaal Chamber
of Mines advertised a competition in papers in the United Kingdom,
Europe, Australia, South Africa and America and offered prizes for
the three best suggestions and devices for the prevention of miners'
phthisis. There were 229 competitors' suggestions as under:
1.
2.
3.
4.
5.
6.
7.
8.
9.

Respirators
41
Dust extractors and hoods
35
Water drills
9
Jets delivering water inside the hole
4
Jets delivering water at the mouth of the hole . . 60
Sprays
22
Atomisers
6
Medical
15
Miscellaneous
37

The judges condemned as quite impracticable and useless Classes 1,
2, 8 and 9, but the others are all in general use in some form or other.
FUMES AND DUST FROM BLASTING

From the evidence given before the Miners' Phthisis Commission
in 1902-1903, it is evident that up to that time there had been few
restrictions of blasting operations, and that persons working
underground had been very frequently exposed to smoke and
fumes; this latter state of affairs was particularly marked at the
end of the one shift and the beginning of the other.
The Commission in its report did not lay stress on the necessity
of avoiding exposure of men to blasting smoke in the mine, except
in the case of miners returning to dead-ends immediately after
blasting. The danger from dust produced by blasting was not
then fully realised, and, although progress was made in allaying
dust produced by machines, etc., by the use of water, it took some
years before the effects of dust from blasting were finally controlled. The following extracts from reports of inspectors of

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mines clearly show that even as late as 1911 the conditions on some
of the mines were still very bad:
In 1908-1909 it was a common practice on a certain mine to send the
night-shift down against the day-shift coming up—naturally the nightshift had to inhale smoke from blasting.
Occurrence in 1911 and the years immediately preceding it:
While taking dust samples in a stope about 6 p.m. in an atmosphere
which was full of smoke, the night-shift arrived to begin work, and I
understand that this was a daily occurrence.
No real advance was made until the Medical Commission issued
its report in 1912, and definitely concluded that not only men
working rock drills, but all men working underground were liable
to contract miners' phthisis.
From this conclusion it was perfectly clear that the problem had
resolved itself into not only allaying the dust produced by drilling
machines and the removal of the broken rock, but reducing the
dust content of the whole mine atmosphere, which was permeated
with very fine dust particles, blasting operations being the most
prolific source of dust and the most difficult to contend with.
It was impossible to reduce the dust in the air created by blasting
to a safe limit, and the only method to overcome its deadly effect
was to remove the men before the smoke enveloped them and to
keep them out of the mine until the fumes and dust were dissipated.
DOUBLE SHIFTS

One factor which had a very marked effect on the health of
the miner was the double shift worked on all the mines of the
Witwatersrand, i.e. a complete cycle of mining operations, cleaning,
drilling and blasting, was performed on two shifts in the twentyfour hours. Owing to the duration of each shift being nine and
a half to ten hours, there was insufficient time between the shifts
to permit of the smoke and fumes from blasting operations to be
cleared out of the mine before the arrival of the following shift, and
almost invariably the on-coming shift was exposed to smoke and
fumes. On Saturdays the position was even worse, as the afternoon shift was lowered immediately after the blasting of the morning
shift; this had to be done in order to get a full shift in by midnight,
as it was, and still is, illegal to work on Sundays.
When it became known that these conditions were exceedingly

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155

injurious to health, the necessary change-over to single shift could
not be effected at short notice, but had to be done gradually.
Generally all the stope faces in the mine were being worked,
and to obtain the required tonnage for the mill these faces had to
be drilled and blasted twice in twenty-four hours; to maintain
the stope faces, development ends were being pushed ahead on
double shift.
Summing up the position, the mines had to continue double
shift until such time as sufficient faces were available to permit the
breaking of the necessary tonnage to keep the mill supplied on the
one shift only.
ALTERATIONS NECESSARY FOR SINGLE SHIFT WORKING

A further factor which delayed the change-over was that the
mines were only equipped for double-shift working. Considerable
alterations and additions had to be made in the plant and in the
mine itself, e.g. compressors had to be duplicated to meet the
greater demand for compressed air. Hoisting arrangements could
not cope with the full complement of men on the single shift;
the capacity of ore bins underground was too small; the number
of rock drills had to be increased, etc. Apart from the time
required to effect these alterations, a large amount of capital had
to be found before they could be carried out.
PROGRESS OF THE SINGLE SHIFT

In 1907 some of the mines resorted to what was virtually a
sixteen-hour shift, i.e. two eight-hour shifts, the one shift following
directly after the other, blasting operations being carried out at
the end of the second shift only. This was undoubtedly a step
in the right direction, as it gave an interval of eight hours for the
smoke and fumes to clear away before the following shift was sent
down.
The year 1910 registered a further advance, in that some of the
mines were on single shift, blasting at the end of the shift, i.e. the
major portion of the work in the mine was done on the day shift,
with a limited complement of boys and men on night shift to do
the cleaning out.
By 1913 the majority of the mines on the Witwatersrand had
changed over to single shift, the full night shift of practically equal
strength to the day shift having become a rarity.

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CONFERENCE

There is no doubt that the elimination of the double shift was one
of the most important steps taken to produce healthy underground
conditions, as well as doing away with an unduly expensive night
shift expressed in the following terms by a witness before the
Mining Regulations Commission, 1907:
Nearly all miners sleep underground on night shift, the average time
slept being about four hours.
DURATION OF SHIFT

The duration of the shift also had a very important bearing on the
health of the miner. It might almost be considered, other things
being equal, as a measure of the amount of dust inhaled by the
miner.
Prior to the Anglo-Boer War, miners were scarce, and the
tendency was for contractors to take on as much work as was
given to them; this entailed long hours underground, and it was not
an uncommon practice for a contractor to have two gangs of natives
working, one on day shift and the other on night shift. Although
the latter practice eliminated itself as the mines became deeper
and access became more difficult, nevertheless the tendency for
contractors to work long hours underground persisted and became
an established custom.
Up to 1909, the mines were still working shifts of ten hours'
duration; the hours were, day shift 7 a.m. to 5 p.m., night shift
7 p.m. to 5 a.m. On the day shift the men were allowed one hour
on the surface for lunch. In 1910 the hour for lunch was done
away with, thus reducing the over-all period to nine hours. This
was a very much better arrangement, as the men were hoisted an
hour earlier; this gave them more daylight for outside recreation.
It also increased the interval between shifts.
The nine-hour shift continued until Act 12 of 1911 was passed,
limiting the hours of employment of persons underground.
. Act 12, 1911
9. (1) No person employed to perform underground work in any
mine shall work, and no person shall cause or permit any person so
employed to work, underground for a longer period than eight hours
during any consecutive period of twenty-four hours, or forty-eight
hours during any consecutive seven days, exclusive of time occupied
in going to or from the working place.
There is no doubt t h a t the reduction of hours could only do good
from the point of view of the miners' health, and, as far as reducing

DUST PREVENTION AND RELATIVE REGULATIONS

157

the amount of work done was concerned, had little effect, as it was
balanced by closer supervision and improved organisation generally.
Difficulties were met with at first in arranging shifts and hours,
but were finally overcome. The eight hours was from face to face,
and this led to difficulties in regard to time spent underground by
the miners, the contractors being only too willing to remain at work
in order to get the best results, the increased overtime being
attributed to travelling delays, etc.
Regulations
In order effectively to control and give effect to the eight-hour shift,
the following Regulations were promulgated:
158. In addition to his other duties and responsibilities under
these regulations, the manager shall:
(24) Provide on mines other than coal and base metal mines
under section 9 (2) (c) of the Act:
(a) That a notice shall be kept posted up at each shaft head,
showing the time within which shifts will be let down and
hoisted up at the shaft head.
(£>) That the average time in getting miners, as defined in Act
19 of 1912, from the shaft head to their working place
at the commencement of their shift, and back again at the
conclusion of such shift, shall together not exceed thirty (30)
minutes per miner for any one shift. In special cases, after
application made through the Inspector of Mines, the Minister
may grant such extension of the period of thirty minutes
as he may consider to be necessary. Notice of such application
shall be posted up at the mine for fourteen days before the
application is sent to the Inspector of Mines.
(c) That the mine overseer, shift boss or other official appointed
by the manager for the purpose shall satisfy himself that
no white person not exempt under section 9 (2) of the Act
remains underground after the ordinary hoisting of persons
employed on that shift is concluded, and shall record in a
book to be provided by the manager, the name of any such
white person so remaining underground, and the time when
such white person reaches the surface.
The effect of these Regulations was to give the white man an average
period of eight and a half hours underground, including travelling from
the surface to his working place and back again.
Original Arrangement arrived at between the Transvaal Chamber
of Mines and the South African Mine Workers' Union
That from 1 January 1918 the underground working week shall be
forty-eight and a half hours bank to bank, the length of each shift to be
counted from the first skip down to the first skip up, and the Saturday
shift to be at least one hour less than the weekday shifts. (In practice
the hours are eight and a quarter bank to bank on weekdays and seven
and a quarter on Saturdays, with some minor exceptions, e.g. certain
shaft sinkers and developers.)

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These are the hours prevailing on all the Witwatersrand mines at
the present time.
CONDITIONS PREVAILING IN THE M I N E S

Generally the adverse conditions which had to be overcome may
be summed up as follows :
(1) All men on the outgoing shift were not hoisted before blasting
took place, and were in the mine for some time after blasting
operations had taken place, and in many cases were exposed
to smoke.
(2) Some of the persons had to be hoisted in the upcast shafts,
where the conditions were bad.
(3) The persons actually blasting were often unable to avoid the
smoke from blasting.
(4) Promiscuous blasting was practised more or less throughout
the shift.
(5) The oncoming shift was lowered before the air was sufficiently
clear.
To overcome Nos. (1) and (2) the mines had to resort to hoisting
as many men as possible in the downcast shafts.
Special cages and conveyances were made to hoist the workmen
as quickly as possible before the smoke overtook them in the upcast
shaft. Doors and regulators were put in to keep back the smoke
or to deflect it. Mechanical ventilators were temporarily stopped t o
delay the arrival of smoke at the shaft; suitable waiting places were
provided for the up-going shift and kept supplied with fresh air
from the compressors.
No. (3) was overcome to a great extent by arranging the blasting
of individual places in a suitable sequence commencing from the
upcast side and travelling against the air currents.
No. (4): blasting, except where absolutely unavoidable and in
isolated instances only, was confined to the end of the shift.
No. (5): blasting at the end of the day shift, and increasing
the interval between t h a t shift and the following oncoming shift,
was finally overcome by doing away with the double shift and
blasting at the end of the shift only.
The concentrated attention given to the problem of successfully
combating miners' phthisis led to the carrying out of necessary
experiments by individual mines. As the problem became better
understood, the tendency was for successful innovations to be
automatically adopted into general practice.
The progress of these changes is reflected in the history of the
changes periodically embodied in the Mining Regulations.

DUST PREVENTION AND RELATIVE REGULATIONS

159

Regulations
On the recommendation of the Miners' Phthisis Prevention Committee,
the following Regulations were eventually framed, and were embodied
in the amendments published on 30 October 1913:
61. No person shall work, or remain, or be permitted or ordered
to work, or remain in any place in a mine, if the air contains dust
smoke or fumes perceptible by sight, smell, or other sense.
101. (33) A ganger or miner . . . shall only blast at the end
of the shift, except where necessary, and then only with the permission
of the mine overseer or the shift boss.
158. The manager shall:
(4) Cause blasting operations and shifts to be so arranged that
workmen shall be exposed as little as practicable to fumes
and dust from blasting.
178.
(2) All Regulations referring to the prevention of miners'
phthisis shall, so far as they concern coloured workmen,
be translated into the more important native languages and
kept posted up in the compounds.
The First Miners' Phthisis Prevention Committee investigated the
extent to which men were exposed to the dust and fumes from blasting
at the end of the shift, and dust samples were taken on all the mines
for the purpose of determining the amount of dust present in the air
breathed by the oncoming shift. They found that the air after blasting
contained extremely large quantities of dust, and that the presence of
smoke is a sufficient indication of the existence in such air of an amount
of dust which is very dangerous to health. Five minutes in such an
atmosphere has probably a worse effect than a full shift spent in drilling
holes in a drive with water well applied. This indicated that very
stringent measures had to be taken to prevent persons from being
exposed to fumes from blasting.
Largely on the recommendation of the Miners' Phthisis Prevention
Committee, further amendments were added to the Regulations and
promulgated in 1917; their object was to improve the conditions in
mines in respect of dust and ventilation. The following are those applied
to prevent persons being subjected to fumes and dust underground:
60. In any mine included in the list of mines framed under section 2
of Act 19 of 1912 (mines in which miners' phthisis may be contracted):
(1) Blasting shall only take place once in every twenty-four hours,
except as permitted under Regulation 106 (33), or for sinking
vertical shafts, or after written permission has been obtained
from the Inspector of Mines;
(3) No person shall blast or be permitted or caused to blast the
cut and round separately on the same shift in the same
development end.
106. (34) Shall . . . only blast at the end of the shift except
for removing obstructions in ore passes or box holes, or for the purpose
of making the hanging safe, or for blasting misfired holes in development faces, and then only with the permission, in each case, of the
manager, mine overseer or shift boss.

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158. The manager shall:
(4) Cause the times of the working shifts and of blasting operations
in every section of the mine to be so arranged that workmen
shall not be exposed to fumes and dust from blasting, unless
this is unavoidable;
(5) Cause every person not engaged in blasting operations, or not
required for the transport of the persons so engaged, to be
hoisted to the surface or removed to the intake side of all
places in which blasting is to be done, or to remain in a waiting
place free from fumes and dust before blasting commences;
(6) Cause every person engaged in blasting operations or required
for the transport of persons so engaged to travel to the surface
in the downcast shaft, unless they can be removed from the
mine before the fumes overtake them or can remain in a
waiting place free from dust and fumes, until these have
dissipated ;
(7) Cause any person who is to work in the mine after blasting has
taken place to enter the mine only after the places in which
he has to travel or work are clear of fumes and dust, and
after the expiry of an interval to be fixed for each mine by
the Inspector of Mines;
(8) Supply to the persons who have to carry on blasting operations,
lighting torches, which in burning evolve not more nitrous
fumes, expressed in terms of N0 2 , than one-half of 1 per cent.
of the weight of substance burned.
161. (9) A shift boss or other official of at least equal rank shall
be present underground at each working shaft at blasting
time and shall not travel to the surface before the persons
engaged in blasting operations.
(10) The manager shall, when the total number of persons employed
underground, on any one shift, exceeds 1,000 persons, appoint
one or more competent persons whose principal duty it shall
be to examine and report to the manager on:
(a) All matters relating to the mine's water supply, its quality,
distribution and use,
(b) The condition of the necessary appliances for using water
at each working place, etc.;
(c) The dust sampling of the mine;
(d) The condition of the mine relating to ventilation and
health, etc.
The manager shall, by letter, notify the Inspector of Mines of the
person or persons so appointed from time to time, and the reports
made by them shall be open to the inspection of the Inspector.
143. (2) (c) Any person who has knowledge of dust or fumes in
the workings during working hours, etc., shall record the matter
without delay in the record book.
(d) Verbal report of the above defective condition to be made to
the shift boss or other official.
The following amendment was made as from 30 October 1913:
106. A ganger or miner who is the holder of a blasting certificate :

DUST PREVENTION AND RELATIVE REGULATIONS

161

(33) Shall not enter or allow any person to enter an end, raise, winze
or other close place after blasting within thirty minutes after
putting the water blast in action, and then only if the air is
free from dust smoke, and fumes perceptible by sight, smell
or other senses.
The practice of returning only when the drive, raise or winze was
free of smoke, although an advance on the previous practice, was still
unsatisfactory, as it frequently happened that the water blast was
out of order when the miner blasted, or the water blast was put out of
commission by the blast; the miners were very unwilling to lose the
round, and there was nothing to prevent the men re-entering before
thirty minutes had elapsed or before the smoke had been cleared out
of the drive.
The practice of blasting the cut and round separately on the same
shift was prohibited by Regulation 101 (3) from and after 1 January
1915, except with special permission from the Inspector of Mines.
By this time a considerable number of the mines had discontinued
this practice and were blasting cut and round together, or had made
provision for the cut being blasted on the one shift and the round on
the following day by increasing the miners' working ends.
One or two mines continued to blast the cut and round separately
on the same shift, availing themselves of the special permission granted
under certain restrictions.
Finally the practice was totally prohibited in 1917.
With the improvements in drilling machines and methods applied
at the present day, very little footage is lost by blasting cut and
round together.
The 1925 Annual Report of the Transvaal Chamber of Mines
Standing Committee on Dust Sampling records a steady and progressive decrease in the average amount of dust found in mine
air since 1915.
Referring to Regulation 158 (8), the Miners' Phthisis Prevention
Committee considered t h a t exposure to nitrous fumes produced by
blasting operations was a greater danger than that of possible
chronic poisoning by carbon monoxide. The fumes of N 0 2 are
intensely irritating to the air passages and lungs, and the repeated
inhalation of very small quantities would produce and maintain a
chronic catarrhal condition, which would aggravate and accelerate
the harmful effect of dust. As lighting torches were made up of
blasting gelatine (a highly undesirable practice), it was advisable
to limit the amount of N 0 2 given off by torches.
The problem of extracting dust from mine air was also investigated by the Committee appointed to report on the ventilation
of dead ends in 1924, but, although a certain amount of success
was obtained, the experiments were not brought to a final conclusion.
This brings us up to date, and it seems as if only greater attention
H

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to detail, and possibly various minor changes, can effect any
appreciable improvement in conditions without radically altering
our present system.
If preliminary investigations made along the lines recently
suggested by Dr. Haldane with regard to dust dilution tend to
support his hypothesis, it may be found possible to carry out
practical tests on a working scale which if successful would lead
to the complete elimination of miners' phthisis.
SUMMARY OF TESTS FOR

DUST

(BEFORE

AND

AFTER BLASTING)

PRESENT IN THE AIR OF WAITING PLACES OF THE
CERTAIN

MINES

THE

WITWATERSRAND

TAKEN

SHAFTS OF
1914-1915

(MINERS' PHTHISIS PREVENTION COMMITTEE)
[Dust: mg. per c m . = milligrams of dust (mineral) per cubic metre of air. Before
blasting = Prior to shots being beard. After blasting = From time first shots beard
up to the hoisting away of last cage load of employees.]
Number of persons hoisted during
Mine

All

Average
period
occupied
by
sampling

1 hr.
35 mins.

Upcast shaft

Downcast shaft

Dust samples (mg. per cm.)
Upcast shafts

Downcast shafts
¡

Whites

Natives

Whites

Natives

Before
blasting

After
blasting

Before
blasting

After
blasting

1,301

14,941

1,654

22,206

2.8

10.4

3.5

4.9

This table clearly shows the large number of persons who were
hoisted in upcast shafts during blasting at this time, and the
big increase in dust concentration to which they were exposed.
In 1917 this was prohibited [see Regulation 158 (5)].
THE USE OF WATER FOR ALLAYING DUST

The use of water was recognised as the most efficacious method
of allaying dust produced by the various mining operations. The
best methods of applying it effectively were only arrived at after
years of experience and innumerable experiments.
Among the devices first used for dust allaying were sprays and
atomisers. In 1903 experiments with the various types were
carried out to test their relative efficiencies as dust allayers, and

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163

from the results of these tests Britten's atomiser was adjudged
the best and awarded the Chamber of Mines first prize in the
competition referred to previously.
At the outset water was not laid on to the working places;
to operate the sprays and atomisers, drums were installed in the
working place, and water carried in to them. These drums were
connected to the compressed-air pipe, from which the necessary
pressure was obtained to force the water out of the drum through
a hose pipe to operate the atomiser or spray, which in turn was
directed on to the collar of the hole being drilled whilst the drill
was operating, thus damping the dust as it came out of the hole.
Sprays and atomisers were believed to be effective in allaying
most of the dust produced during drilling and shovelling operations, and by 1906 many of the mines were equipped with them.
Regulations were eventually promulgated to enforce their use.
These devices were never popular with the miner; the atomiser
charged the atmosphere with water, and everything within its
range became saturated with water, including the miner's clothes;
moreover in many cases the water was not clean, and the atomisers
became choked and ceased to function. At their best, although
allaying a considerable proportion of the dust formed, they did
not prevent the very fine and most dangerous dust getting into
the atmosphere. Gradually they were replaced by water jets,
and ultimately (when water under pressure was available in
abundance) by the hose pipe, sprays being retained only in such
places as vertical shafts, and over ore boxes and ore passes.
ALLAYING DUST IN DEVELOPMENT ENDS

The first attempt to allay dust produced by blasting in the
development ends was to place an atomiser about 70 feet from
the face and put it into operation when the charge was lit up ;
the smoke and fumes from the blast passing through the atomised
water were to a certain extent deprived of their dust content;
this, however, had no effect on the broken rock and did not clear
the end of the drive of smoke. To overcome this defect the water
blast was devised and introduced on an experimental scale in
1907, and gradually became common practice throughout the
Witwatersrand, its use being made compulsory by Regulation
in 1911. The water blast is a simple device consisting of a single
nozzle connected to both a water and compressed air supply by
means of which a mixture of air and water is projected along

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the drive to the face, wetting down the broken rock and displacing
the gases produced by blasting operations.
INSTALLING P I P E L I N E S FOR W A T E R SUPPLY

By 1906 many of the mines were using dust-allaying appliances
for certain classes of work, and, as previously explained, the
water supply to operate the various appliances had to be carried
by hand into the working place: a very unsatisfactory practice
and not conducive to obtaining the best results, specially in
places difficult of access such as raises. The mines realised the
necessity of a better water supply and commenced to lay water
pipes into the working places, obtaining water chiefly from underground sources, and by 1908 a large number of the mines were
so equipped, and Regulations were promulgated for the enforcement
of this practice. The Mining Regulations Commission's report
was issued in 1910, and at that time efforts were directed principally to allaying the dust produced by drilling and shovelling
operations, it being assumed that these were the two chief sources
of phthisis-producing dust.
The Medical Commission report of 1912 dispelled this illusion,
and from then the attack on dust became more general, i.e. water
had to be used freely to water down each working place after
blasting operations before work commenced. The water service
had to be further improved to supply the greater demand, and
in most cases clean water was taken down the shafts supplying
underground reservoirs made for the purpose, and distributed at
suitable pressure to the working places, travelling ways and all
other places when its use was considered necessary.
The introduction of an adequate water supply was the key to
the solution of dust elimination. By the abundant use of water
the dust is not only allayed, but washed down into the drains
and sumps, from where it is either bailed or pumped out of the
mine.
W A T E R F E E D ROCK D R I L L S

The " Water Leyner " rock drill was first introduced into the
mines as far back as 1902. The principle of this machine as a
dust allayer was accepted as correct at the time and its maker
was awarded the Chamber of Mines second prize. The conservativeness of the miner, the poor class of material of which hollow
drill steel was then made, and the lack of a satisfactory water

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165

supply delayed its successful introduction. In 1913 the " Water
Leyner " drill and the Atlas drill, both passing water down the
drill steel, were introduced on a number of the mines, and were
very welcome from a health point of view. As time went on,
reciprocating machines, both in stoping and development, were
gradually eliminated by the water-fed machines, which apparently
cut down dust production considerably.
At the end of 1916 a drilling machine known as the " dry "
jackhammer was used; it worked with a hollow jumper, but
exhaust air and not water passed down it. If a plentiful supply
of water was turned into the hole by means of a jet, the dust
results were at first considered satisfactory, but it was afterwards
found that the air passing down the steel ejected considerable
quantities of dust on escaping into the atmosphere. This led to
experiments being carried out in 1919 with " wet " jackhammers,
i.e. " axial water feed machines ", and some of the mines changed
over to these " wet jacks " in 1920, and gradually they replaced
the " dry " type. The advent of the " Kotze " konimeter revealed
the fact that internal water-feed machines produced extremely
fine dust of the most injurious nature which had hitherto passed
unnoticed. This defect was to a certain extent overcome in 1922
by re-designing the rock drill machines, fitting them with dustless
pistons and later by the introduction of release ports into the
front head of the machines. The former reduced the amount of
air escaping from the cylinder to the chuck cavity, and the latter
allowed most of the escaped air to pass out of the chuck cavity
instead of passing through the axial hole in the drill steel. To
reduce the amount of air passing down the steel, Regulations
were promulgated prohibiting the use of short pistons in certain
classes of work, enforcing the adoption of release ports, and
requiring all machines to be tested by the Mines Department
and approved before being passed for use underground. At
present endeavours are being made to develop a satisfactory
external water-feed machine, which will practically prevent any
air passing through the steel, the sludging being done by water only.
OTHER SOURCES OF DUST

(a) Dirty water supply. — The machines atomise a certain
amount of water, leaving the solid matter suspended in the air.
The only check on this is to take samples of the water periodically
and analyse them for solid matter (silica).

166

PAPERS PRESENTED TO THE

CONFERENCE

(b) Blowing out drill holes. — If this is done dry, it releases
enormous quantities of dust, which should be washed out by water
jets, avoiding the use of air if possible.
(c) Blowing out sockets. — Air should be avoided and water
only used to wash them out.
REGULATIONS

Government Notice 1278 of 1908: Amendment to
Regulation 146
Recommendations of the Mining Regulations Commission:
(5) Every place where development work is carried on, and where
the natural strata are not wet, and every dry and dusty stope
shall be adequately supplied at all times with suitable clean
water. Such supply shall be continuous and shall be sufficient
for effectively damping the broken ground and for allaying the
dust caused by drilling operations.
146. (ii) The ganger or miner in charge of workmen shall be responsible that the following provisions be observed:
(1) No person shall in the drilling of holes use any percussion machine
drill, unless a water jet or spray or other means equally efficient
is provided and used so as to prevent the escape into the air of
dust caused by the drilling.
(2) No person shall in any part of a mine remove any broken rock
or ground, if such rock or ground is in a dusty condition, until
it has been effectively damped so as to prevent the escape of
dust into the air during removal.
Act 12 of 1911
60. In development faces and in winzes a water blast or similar
apparatus for laying dust after blasting must be used.
101. (1) No person shall in the drilling of holes use or cause or permit
to be used any percussion machine drill unless a water jet or spray or
other means equally efficient is provided and used, so as to prevent the
formation of dust by drilling, and unless the floor, roof and sides of the
working place, to a distance of at least 25 feet from the face, be kept
constantly wet.
When hand drills are used for drilling dry holes, a swab shall be
provided and used around the drill at the collar of the hole.
(2) No person shall in any part of the mine move any broken rock
or ground if such rock or ground is in a dusty condition, unless and until
it and the floor, roof and sides of the working place, to a distance of at
least 25 feet, have been effectively wetted and kept wet, so as to prevent
the escape of dust into the air.
Amendment Published on 31 October 1913
106. A ganger or miner who is the holder of a blasting certificate:
(32) Shall, at any mine included in the list of mines framed under
section 2 of Act 19 of 1912, not enter nor allow any person
to enter any end, raise, winze or other close place after blasting

DUST PREVENTION AND RELATIVE REGULATIONS

167

within less than thirty minutes after putting the water blast
in action, and then only if the air is free from dust, smoke and
fumes perceptible by sight, smell or other senses.
(34) Shall in all development faces (except in the case of a winze
being worked on single shift) immediately after lighting up,
put into action the water blast, which he shall previously have
tested. If as a result of such test, the water blast shall be found
to be not in order, no blasting shall take place.
109. The following plans shall be kept in the office at every mine:
(2) (6) A plan showing all the water pipes with their dimensions
as well as all tanks, reservoirs, fixed and continuous sprays,
and other devices for allaying the dust.
158. (6) (a) Provide or cause to be provided an adequate and constant
supply of water which is clean and odourless at every working place
which is not naturally wet. Such supply shall be sufficient for effectively
wetting the broken ground and for preventing the formation of dust
caused by drilling operations. Such water shall be supplied in metal
pipes not less than one inch in diameter, at a pressure of not less than
30 Ibs./sq.in. at each working place, when all sprays and jets supplied
from the same pipe are working. Such pipes shall reach to within 50 feet
from the face and from there a sufficient length of hose shall be provided
and used to bring the water up to the face.
(¿>) Cause the surface in all working places, travelling ways and
shafts, which are not naturally wet, to be kept wet as far as practicable.
{d) Provide in shafts, which are not wet, ring sprays at suitable
points to prevent dust being carried with the air current.
(e) Provide a water blast as near as practicable to all development
faces (except winzes worked on single shift).
161. (9) Each shift boss shall at the end of the shift pay special
attention to the requirements of Regulation 106 (32).
Amendment Published on 30 May 1917
Regulation 60 to be amended to read:
(2) Every drive, cross-cut, raise, incline shaft, and winze, and every
working place in which there is no through ventilation current,
shall be furnished, at a distance not exceeding 50 feet from the
face, with a water blast, approved by the Inspector of Mines,
which shall be continuously applied for at least thirty minutes
after blasting, for the removal of dust and fumes, where the
distance of such working place from the point at which there is
connection with the general air current of the ventilating district
exceeds 300 feet; an additional water blast shall be placed and
used not more than 200 feet and not less than 100 feet from the
water blast at the face.
Regulation 62:
(3) No person shall stope or be caused or permitted to stope above
any drive or level where there is no through connection from the
stope to the drive or level above, except by permission of the
Inspector of Mines, and then only on the condition that the
ventilation of such stope is adequate, that the number of persons
working therein is limited, and that when machine drills are
used, such machine drills are provided with axial water feed.

168

PAPERS PRESENTED TO THE

CONFERENCE

Regulation 101: section (1) to be amended to read:
(a) No person shall in the drilling of holes use or cause or permit
to be used any percussion machine drill other than an axial water feed
drill, unless a separate water hose, furnished in the case of dry holes,
with a narrow pipe at least 24 inches long, for inserting in the hole when
drilling, is provided for each machine and used, so as to prevent the
formation of dust.
{b) In collaring by means of a percussion machine drill, other than
an axial water feed drill, the narrow pipe shall be removed from the
hose, and the water from the hose shall be turned directly on to the
collar.
(c) No person shall use or cause or permit to be used any hand
drill unless water is applied or a wet swab is used around the drill at
the collar of the hole, so as to allay the dust.
(d) No person shall use or cause or permit to be used, for the
purpose of rising or of boxholing, any machine drill other than one
with axial water feed.
(e) No person shall commence or continue to drill any hole, or cause
or permit such commencement or continuation of drilling, unless the
floor, roof, sides and broken rock of the working place' to a distance
of at least 25 feet from such hole have been thoroughly wetted and kept
wet.
(/) No person shall blow out or be caused or permitted to blow out
any hole with compressed air unless he has applied sufficient water in
case there is not already a sufficiency to prevent the formation of dust
during the process of blowing out.
Section (3): No person shall in any part of a mine perform or be
caused or permitted to perform work of any kind liable to create
dust, unless and until the floor, roof and sides of the working place
to a distance of at least 25 feet have been effectively wetted and
kept wet, unless such working place is naturally sufficiently wet to
render the formation of dust impossible.
Regulation 106 (34) to be amended to read as follows:
(34) Shall at every mine included in the list of mines framed under
section 2 of Act 19 of 1912 only blast at the end of the shift, except
for removing obstructions in ore passes or box holes or for the purpose
of making the hanging safe, or for blasting misfired holes in development
faces, and then only with the permission in each case of the manager,
mine overseer or shift boss. Before blasting such obstructions in ore
passes or boxholes or for making the hanging safe, the ganger shall wet
the ground thoroughly within at least 25 feet of the obstruction. When
blasting misfires he shall observe the precautions prescribed in Regulation 106 (33).
Regulation 143:
(b) Any defect in the mine water service or dust-allaying devices, or
in any appliances provided for the health or safety of persons working
underground, shall be recorded in the record book by the employee
having knowledge of such defect immediately on coming off shift.

DUST PREVENTION AND RELATIVE REGULATIONS

169

Regulation 158:
(6) (a) to be amended by the deletion of the words " which is not
naturally wet " and the substitution therefore of the words,
" which is not sufficiently wet to make the formation of dust
impossible ";
(6) to be amended by the deletion of the words " as far as practicable"
and the addition of the words " or regularly washed down ".
To be amended by the addition of the following new subsection:
(/) Provide or cause to be provided at every ore bin, ore pass, or
grizzley, unless exempted by the Inspector of Mines, a constant
supply of clean water, which shall be applied during working
hours at the openings of such ore bins, ore passes, and grizzleys,
by means of efficient atomisers, which shall at all times be kept
in good working order.
Regulation 158 to be amended by addition of the following section:
(23). Cause any surface dump as the Inspector of Mines may direct
to be sprayed with a sludge of black soil, or otherwise dealt with in a
manner satisfactory to the Inspector, so as to prevent the dissemination
of dust or sand from it.
Regulation 161 to be amended by the insertion of the following
section:
(10) (a) All matters relating to the mines water supply, its quality,
distribution and use.
(6) The condition of- the necessary appliances for using water at
each working place and elsewhere.
Government Notice 1571 of 26 November 1918
Regulation 158: section (10) to be amended by the addition of the
following subsection:
(g) Provide and cause to be used in every crusher station and ore
sampling room, appliances, such as suction fans, atomisers and
sprays, which may be necessary for the effective prevention of
dust arising from the operations conducted in such station or
room.
Government Notice 1730 of 26 October 1921
Amendments to Mines and Works Regulations
101. (5) (a) No new type or make of machine drill may be used
on the scheduled mines without the prior approval of the Government
Mining Engineer, or may be continued in use unless that approval is
ratified by him within one year, and after at least twenty (20) of the
machine drills so previously approved have been in regular use on the
scheduled mines to his knowledge for a period of six months.
(¿>) The Government Mining Engineer may prohibit the use of any
type or make of machine drill in use on any scheduled mine. Such
prohibition (etc.).

170

PAPERS PRESENTED TO THE

CONFERENCE

Government Notice 1863 of 16 November 1921
Regulation 102 is hereby amended as follows:
102. (3) At any mine the ganger or miner making the examination
prescribed in sections (1) and (2) shall also thoroughly wet the roof,
sides and floor, as well as the broken rock, before admitting to the
working place the members of the gang, other than those required to
assist him in making safe.
Government Notice 511 of 21 March 1923
Regulations 60 (2), 101 (1) (a), 101 (1) (b) and 161 (10) to be deleted
and the following substituted therefor:
60. (2) Every tunnel and development end, such as a drive, cross-cut,
raise, incline shaft or winze, shall be furnished with a water blast approved
by the Inspector of Mines. Such water blast shall discharge within a
distance of not more than 50 feet of the face being advanced, and
shall be applied so as to effectively wet the face and broken rock for
at least fifteen minutes immediately after blasting, and again for a
further period of fifteen minutes immediately prior to entry by any person,
provided that the Inspector of Mines may give written permission to
the manager to vary these conditions on any mine or part therefor.
101. (1) (a) No person shall, in drilling a hole, use or cause or permit
to be used any percussion machine drill using solid steel, unless a water
hose is provided for each machine, and used so as to prevent the formation
of dust. When drilling a dry hole the water hose shall be furnished with
a narrow pipe at least 24 inches long, which shall be inserted in the hole.
In collaring, except in the case of jackhammers in stopes, the full bore
of the hose must be used for supplying water to collar.
101. (4) (b) No person shall, in drilling a hole, use or cause or permit
to be used any axial water-feed drill, unless an adequate supply of
water flows through the drill steel. In every tunnel and development
end, such as a drive, crosscut, raise, incline shaft or winze, and in every
stope included under Regulation 62 (3) no person shall, in drilling a
hole, use or cause or permit to be used any axial water-feed drill, unless
an additional water-hose is provided and the water from it turned
directly on to the collar while collaring. No drill steel shall be used in
any axial water-feed drill, unless the diameter of the axial hole is at least
one-quarter of an inch throughout its whole length, when the diameter
of the drill steel is one and one-eighth inch or over, and at least threesixteenths of an inch, when the diameter is less than one and one-eighth
inch.
161. (10) In any mine included in the list of mines framed under
section 2 of Act 19 of 1912, the manager shall, when the total
number of persons employed underground on any one shift exceeds
one thousand persons, appoint one or more competent persons whose
principal duty it shall be to examine and report to the manager on:
(a) All matters relating to the mine's water supply, its quality,
distribution and use.
(b) The condition of the necessary appliances for using water at
each working place and elsewhere.

DUST PREVENTION AND RELATIVE REGULATIONS

171

On 4 July 1923 the following machines were prohibited:
(a)
shafts
(b)
work,

The short-piston Leyner drill, in all development work, except
and winzes, after 10 March 1924.
The Model 21 Waugh Turbro drill (Standard) in all classes of
after 10 January 1924.
Government Notice 2046 of 8 December 1923

Prohibiting the use of any machine drill used with either shell or
cradle which passes or is designed to pass air through the drill steel
with or without water in all development work except shafts and winzes,
after 10 March 1924.

THE GENERAL Q U E S T I O N OF
MINE V E N T I L A T I O N A N D AIR RENEWAL,
INCLUDING REFERENCES TO T H E H E A T A N D
HUMIDITY PROBLEMS
BY

G. A. WATERMEYER,

B.A. (C.G.H.), A.R.S.M., PROFESSOR OF MINING,

UNIVERSITY OF THE WITWATERSRAND; AND J . P . R E E S , A.R.S.M., B . S C ,
D.I.C., A.M.I.M.E., A.I.M.M., DUST AND VENTILATION OFFICER, TRANSVAAL
CHAMBER OF MINES

The ventilation of the mines of the Witwatersrand is now
almost universally produced by means of fans. The fans may be
placed at any suitable point either on the surface or underground.
But, wherever placed, the purpose is to cause the air to enter
the mine through a down-cast shaft or shafts, to pass through
the working places, and to return to the surface through the
returns and upcast shafts. The primary purpose is to ventilate
the working places. These are naturally divided into two types,
the development ends and the stopes. To facilitate the operations
of mining, the reef containing the gold is cut up into blocks by
driving tunnels, both on the level (" levels ") and at the inclination of the reef (" winzes "). The operations involved in cutting
out the blocks of reef (or " development work "), therefore,
precedes the actual mining of the reef (or " stoping "). And as
a general rule the fresh air is first directed to the development
work and is afterward directed through the stopes.
The downcast shafts are generally used for lowering and raising
men, material and rock, and for carrying compressed air and
water pipes, as well as electrical cables. The timber framework
of the shafts is kept wet by means of water sprays and in addition
water often appears in the shafts from other sources. Hence the
shafts are wet, and the air picks up a large amount of moisture
during its passage into the mines and is kept correspondingly cool.
The air may pass in series through two or three shafts if the
workings are at great depth, and then, towards the bottom of
the mine, the air splits and travels out to the working places.

MINE VENTILATION AND AIR RENEWAL

173

The velocity of the air in the splits is much less than in the shafts,
and it is exposed to a much greater area of rock. Hence its
temperature tends to rise rapidly towards the natural temperature
of the rock. The rate of increase in temperature, however, is
reduced to some extent by the evaporation.of water and by the
fact that the smaller the difference in temperature between the
air and the rock, the slower is the rate of heat flow from the rock.
Although most of the deep mines are very dry naturally, the
floor of the levels leading to the stopes is wetted by water dripping
out of the cars in which the broken reef is carried from the stopes
to the shafts. The evaporation of this moisture tends to cool
the air and so increase the heat flow from the surrounding rock.
The result is that the wet bulb temperature rises as the air
approaches the stopes.
In the development ends the workers are crowded together in
a confined space (the " end "), whilst in the stopes the} are more
dispersed. Hence the need for large volumes of air is more vital
in the development ends than in the stopes, and special attention
is paid to the ventilation of the former. In 1923 a Committee
was appointed jointly by the Government Mining Engineer and
the Transvaal Chamber of Mines to consider methods of ventilating
dead ends, particularly with the object of reducing the dust during
drilling time to a minimum. This Committee recommended that
development ends should be ventilated generally with at least
800 cubic feet of air per minute blown on to the working face
by fans, or blowers delivering through large diameter pipes carried
sufficiently near the face to produce a perceptible current of air
there. As in some cases the mine air was not found to be sufficiently clean for this purpose, it was further recommended that
in such cases a separate compressed-air jet delivering a minimum
of 100 cubic feet of free air per minute be used. The air travels
into the end through galvanised piping from 12 to 30 inches in
diameter hung from the side of the drive; after ventilating the
end the air travels out along the drive. In some cases, however,
the air travels into the end along the drive and is sucked out
through ventilation piping. But, by whichever system may be
used, fresh air is supplied to the workers; the heat given off from
the freshly exposed rock, from the workers and from their lamps
is removed; and any dust that has escaped the water used to
allay it is diluted and swept away. The length of tunnel that
must be ventilated in this way is usually about 500 feet, and
seven workers are engaged in the end with two machine drills.

174

PAPERS PRESENTED TO THE

CONFERENCE

Tbe workers engaged in shovelling the broken rock and in other
duties may raise the total number of persons in the level to about
two dozen. In the larger tunnels the length may run into several
thousands of feet and the number of persons in the drive be
doubled. The quantity of air circulated varies according to the
circumstances, from 800 cubic feet per minute to 4,000 or 5,000
cubic feet per minute.
The development ends are generally situated in the lowest part
of the mine and the stopes are then at a higher elevation. The
ventilation is almost invariably arranged to pass up from the
lower workings to those at a higher level, so as to take advantage
of the natural tendency of heated air to rise from a lower level
to a higher. The air, therefore, passes from the development
ends to the stopes, though often the stopes are ventilated by air
brought directly from the shafts. The air in its passage through
the workings approaches saturation point. As it travels up the
stopes, it continues for a time to be heated by contact with the
warmer rock and to pick up more moisture from the artificially
wetted surfaces. But, after a time, the air begins to cool by
expansion and contact with cooler rock, so that in the higher
stopes and in the return airways moisture begins to condense out.
This is apt to produce a fog or mist. Mist may also be produced
where warm air meets and mixes with cooler air, or in the neighbourhood of working compressed air machines. The air finally
travels out through old workings and shafts to the surface.
Where necessary, special ventilation shafts have been sunk at
considerable cost to facilitate the return of the air to the surface.
In the stopes the air performs the same duties as in the
development ends. Behind the working face in a stope there
may, however, exist a very large open area, through which the
air passes at a very low velocity. Small boosters of the Venturi
type may then be employed to increase the rate of movement
of the air along the face, or bratticing may be used to direct the
air on to the workers.
The Village Deep mine has now reached a depth of 7,640 feet
below surface, and is the deepest mine in the world. Some of the
neighbouring mines are only a little less deep than this. At these
great depths, the problem of supplying air sufficiently cool for
work to be carried on efficiently has called for special attention.
Air in passing down a shaft is compressed by the weight of the air
above it. The work done produces heat which would under
adiabatic conditions raise the temperature of the air 5%° F. for

MINE VENTILATION AND AIR RENEWAL

175

every 1,000 feet of depth. This heating effect is independent of
the volume and cannot be reduced by the circulation of larger
volumes of air. It so happens that on the Witwatersrand the rate
at which the temperature of the rock rises from the surface downwards is almost the same, being about 5° F. per 1,000 feet in depth.
This temperature gradient is extraordinarily slight and has been
the decisive factor in permitting mining operations to be carried on
to such great depths with copious use of water to allay the dust.
For the evaporation of water reduces the temperature of the air
far below that of the rock at the bottom of the intake shafts. This
difference in temperature between the rock and the air sets up a
flow of heat from the rock to the air which raises the temperature
of the wet bulb to such a degree that it becomes difficult for the
workers to get rid of their body heat produced during work.
Although the evaporation of the water cools the air, the worker
could not in any case receive any direct benefit, since the evaporation does not reduce the wet bulb temperature on which the ability
of the body to get rid of its heat by sweating primarily depends.
From the point of view of providing cool conditions, the use of
water underground is therefore almost entirely objectionable.
The flow of heat from the rock to the air can be stopped by
the circulation of a sufficiently large volume of air which cools
the rock for such a distance round the airway that the heat flow
is negligible. For technical reasons it is difficult to produce a
sufficient volume to effect this purpose even in shafts, and after
the air has split it is quite impossible. Nevertheless experience has
shown that by the circulation of large volumes of air the flow of
heat from the rock can be diminished, and the conditions in the
working places improved, not only because the wet bulb temperature
is lower, but also because the cooling power of the air is increased
by the increased rate of movement of the air.
Although normally the intake shafts of the Witwatersrand are
wet, some of the shafts recently sunk are lined with concrete
and cement, and equipped with steel and are in consequence
comparatively dry. The graph on page 176 illustrates the wet
bulb conditions in two development ends in different mines. In
the case of Mine " A " the shafts through which the air passes
are comparatively dry and in the case of Mine " B " are very wet.
In both cases the shafts are vertical and the volumes passing are
not widely different. The end at Mine " A " is 800 feet deeper
than the end in Mine " B ". In spite of this greater depth the wet
bulb temperature in the Mine " A " end is much lower than that

176

PAPERS PRESENTED TO THE CONFERENCE
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in Mine " B ", mainly owing to the smaller rise of wet bulb temperature in the downcast shafts. A big rise in the wet bulb temperature
takes place in the Mine " A " end owing to the water used there
and the comparative dryness of the downcast air. This graph
shows clearly the adverse effect of the evaporation of water underground on the wet bulb temperature. The actual wet bulb
temperatures in the ends were:
Mine " A '
Mine " B '

79° F.
88° F.

The cooling power of the air as registered by the wet katathermometer was, with two Leyner type machine drills 1 working:

Mine " A "
Mine " B "
1

Millicalories per sq. cm.
per second
14
7

These machines each exhaust about 120 cubic feet of free air per minute.

MINE VENTILATION AND AIR RENEWAL

177

In all the deep mines, in addition to providing as large a volume
of air as is technically and economically possible to produce cool
conditions, special attention is paid to the health of the workers,
but this subject is dealt with elsewhere.
From this account it will be clear that the ventilation provides
fresh air to the workers, ensures as far as possible cool working
conditions, and with the help of water, keeps down the dust
content of the air. After blasting (which only takes place once
in the twenty-four hours) special conditions arise which are met by
the prohibition of anyone entering the working places until sufficient
time has elapsed for the smoke, fumes and dust to be swept away.
In order to ventilate the mines, very large fans have been
installed. For instance, at the Government Gold Mining Areas
the fan which ventilates the mine is capable of handling 900,000
cubic feet per minute at a water gauge of 7 inches. The fan is
30 feet in diameter and driven by a tandem compound engine
developing 1,500 horse power. At the present time this is the largest
mine fan in the world. On other mines are fans nearly as large.
Mention might also be made of the propeller fan, which has proved
particularly suitable for certain purposes. This is a recent innovation and is made up of one or more aeroplane propellers on a
common shaft.
By means of these fans sufficient air is circulated to ensure that
the quantity per person never falls below 30 cubic feet per minute.
Indeed, although a very large personnel is employed underground,
there is usually about 60 cubic feet per person per minute in circulation.

A REVIEW OF THE HISTORY OF SILICOSIS
ON THE WITWATERSRAND GOLDFIELDS 1
BY L . G . I R V I N E , M.A., M.D., C M . , B.SC. (PUB. H.) ( E D I N . ) , CHAIRMAN, MINERS'
PHTHISIS MEDICAL BUREAU; A . M A V R O G O R D A T O , M.A. (OXON), M.R.C.S.
(ENG.), L.R.C.P. (LOND.), FELLOW IN INDUSTRIAL HYGIENE, SOUTH AFRICAN
INSTITUTE FOR MEDICAL RESEARCH; AND H A N S P I R O W , D . S C , D.I.C.
(LOND.), M.I.M.M., GOVERNMENT MINING ENGINEER.

T H E GOLD-BEARING AREA OF THE WITWATERSRAND

Wherever mining operations are carried, on on a large scale in silicious
rock of " phthisis-producing " type, the menace of silicosis begins to
appear so soon as the mining population has become a settled population,
and especially is this the case where machine drills have been
in extensive use.
That is the common experience, and that has been our experience
in South Africa.
The prominence which the problem of miners' phthisis has assumed
in this country has been due to the magnitude of the gold-mining
industry, to the large number of miners whom it employs, and to its
unique concentration upon a single large and continuous gold-bearing
area. The problem has thus been at once larger and more sharply
concentrated than in other countries, and the deaths and suffering
caused by the disease have been more clearly apparent.
The gold-bearing area of the Witwatersrand extends for some thirty
miles on either side of Johannesburg, the outcrop running roughly east
and west, with the reef dipping to the south. The reef is a
quartz conglomerate in a country rock of quartzite. Analyses published
in 1916 in the General Report of the Miners' Phthisis Prevention Committee give the composition of the original ore, and of dust found in mine
air. They show that the components of both are silica, silicates and
pyrites. Dr. J. McCrae informs us that the probable order of the amount
of free silica in the original ore is 75 to 80 per cent., but that in the dust,
according to the published sample, it might be as low as 35 per cent.
So far as the silicosis problem is concerned, it is only the very finest dust
which counts, since only the minutest particles can be taken up by
1
The writers are greatly indebted to Mr. F. G. A. Roberts, Technical
Adviser to the Chamber of Mines, and to Mr. A. B. Payne, General Manager,
Van Ryn Deep, Ltd., for valuable suggestions which have been incorporated
in this paper.

WITWATERSRAND: HISTORY OF SILICOSIS

179

" phagocytosis " into the lungs. Dr. McCrae, in his brief but classical
paper on " The Ash of Silicotic Lungs " published some sixteen years
ago, found that the mineral particles present in the lungs of miners
who had died of silicosis were practically all under 5 microns, and
70 per cent, were under 1 micron in size.
SUBDIVISIONS OF THIS REVIEW

The history of silicosis on the Witwatersrand falls naturally into
four periods :
(1) The initial period of gold mining on the Rand, from 1886 to 1899,
that is, from the date of the first discovery of the reef until the
outbreak of the South African War. One may fairly call this
period, so far as local conditions are concerned, a period of
ignorance of the dangers of silicosis.
(2) The period of first realisation of the menace of silicosis and of
tentative preventive measures, from 1901 to 1910.
(3) The period of the introduction of a legal system of compensation
for the disease, and of the trial of more systematic preventive measures,
from 1911 to 1916.
(4) And, finally, what one may call: The period of the " present-day "
system of fully systematised measures of prevention, detection, and
compensation, from 1916 to the present time.
Our object in the following pages is to trace briefly the parallel and
inter-related development of occupational conditions, of local knowledge
of the disease, its types and its incidence, of the general legal attitude
towards the problem, and of the general preventive measures which
have been adopted.

I. — The Initial Period of Mining on the Rand from 1886 to 1889
This period was one of a large number of small " outcrop " mines.
When gold was first discovered on the Witwatersrand in 1886,
the deposit was regarded as consisting of auriferous gravels which
had become solidified in parts.
Even when it was found t h a t the gold was contained in an
inter-bedded conglomerate, most engineers were sceptical about
the real value of the discovery, as past experience had shown
t h a t the mineral contents of such conglomerates were so erratic
and patchy as to preclude large scale workings. The true
significance of the discovery was only realised many years later.
The eventual growth of the industry was never foreseen, with
the result t h a t the original lay-out of the mines proved unsuitable
for subsequent deep level working. Some ten years after the first
discovery, deep boreholes intersected the reef at depths of 3,000 feet,

180

PAPERS PRESENTED TO THE CONFERENCE

and led to the sinking of the first " deep level " shafts in 1898.
During the first five years, mining on the Rand was largely confined
to work in the oxidised zone which extended to a depth of from
60 to 300 feet. A considerable portion of the workings was
open-cast, and, even when underground methods were resorted to,
the ore was found to be comparatively soft and friable. It can,
therefore, safely be said that the miners were exposed to little,
if any, injurious dust during those days. Drilling was done by
hand until about 1892, when large and heavy reciprocating machines,
mounted on bars and driven by compressed air, were introduced
in development ends.
From the beginning the mines have been worked by gangs of
native labourers under the close personal direction of miners of
European stock.
The European miners at that time were almost exclusively
overseas men attracted to the Rand by high wages and bringing
with them experience gained in other mining fields. To a large
extent they came from Cornwall, where the population had been
inured for centuries to mining conditions. The mining methods
employed were crude, the development ends, which had been
started by " hammer boys ", were small and tortuous, following
the reef exposure. No provision for mechanical ventilation was
made, even when the workings reached depths of several hundred
feet and when machine drills had been introduced in them.
When, however, the oxidised zone had been passed through,
mining operations caused an excessive amount of highly silicious
dust to be disseminated throughout the workings. In development
ends, " cut " and " round " were blasted on the same shift, resulting
in the miner with his assistants returning to the face through
clouds of smoke and dust. Not realising the danger of exposure
to this dust, neither the authorities nor the employees made
any efforts to avoid exposure to it. Blasting took place at all
hours, the miners, who were on contract and earned good wages,
remaining underground until they had taken out their round
or completed the blasting in their stopes. The sanitary conditions
were equally unsatisfactory. No latrines were provided, and
pollution of the working places was common practice. The living
conditions on the surface were no better. Even when the tents
and shacks, which served as shelter during the first few years,
had been replaced by wood and iron and brick houses, living
conditions were those of a typical mining camp. The water
supply, which for many years was precarious, at times threatened

WITWATERSRAND : HISTORY OF SILICOSIS

181

to fail altogether; fuel was expensive; and for a number of years
ox-wagon transport had to be relied upon for bringing the bare
necessities of life from Kimberley, over three hundred miles of
bare veld. It is, therefore, not at all surprising that the foundations of the industiy, laid under such trying conditions, should
have been found unsuitable for the subsequent deep level exploitation.
One may fairly say that locally this period was one of practical
ignorance of the menace of silicosis, although towards the end
of the period, when some years had elapsed after the introduction
of rockdrills, it became known that a proportion of the miners
were becoming affected with disease of the lungs.
At the close of the period in 1899, there were 100 mines working,
hoisting about 8 million tons per year. White employees numbered
about 12,000, coloured employees nearly 100,000. The number
of underground employees at this time is not recorded. About
2,000 rockdrills were in commission, all of the " dry " reciprocating
type. The average stoping depth was about 800 feet. The
maximum depth reached at this time was 3,400 feet.

II. — Period of First Realisation of the Menace of Silicosis and of
Tentative Preventive Measures, 1901 to 1910
The awakening came when work was generally resumed on the
Witwatersrand after the cessation of the South African War.
It was then found that a large number of rockdrill miners who
had previously been working on the Rand had died during the
wai' period, or within a short time after resuming work in the
mines.
In the Report of the Government Mining Engineer (Transvaal)
for the six months ending December 1901, it was stated that of
1,377 machinemen employed before the war, 225 were known to
have died between October 1899 and January 1902. These
numbers would give an average annual death rate of 73 per 1,000.
Facts such as these arrested the attention of the Government,
the mining community and the general public, and in December
1902 the first (Transvaal) " Miners' Phthisis Commission " was
appointed by Lord Milner " to enquire into and report on the
disease commonly known as minéis' phthisis ". This body, usually
referred to as the "Milner Commission", issued its Report in 1903.

182

PAPERS PRESENTED TO THE CONFERENCE
THE MILNER COMMISSION,

1902-1903

This Report forms the first landmark in our local knowledge of
the disease. An attempt was made by the Commissioners to
procure a medical examination of all working miners, but the
returns were incomplete, partly because many of the miners were
reluctant to submit themselves to examination.
However,
1,201 miners were examined; of these 15.4 per cent, were found to
be affected by miners' phthisis and another 7.3 per cent, were
suspected cases. Including the latter, the prevalence of the disease
would thus appear to have been about 23 per cent., b.ut this figure
is probably too low. A very significant feature brought out in the
Report is that, in spite of the number of newcomers required to
replace the losses amongst rockdrill miners, the vast majority of the
miners employed at this time still consisted of miners who had had
their first and often a lengthy experience of mining overseas.
Miners born overseas made up well over 90 per cent, of the total.
The limited evidence adduced indicated that mining work in the
Transvaal, especially rockdrill work, was more dangerous than
similar work elsewhere, but the Commissioners were justified in the
conclusion that previous mining work in other countries had
contributed to some extent to the prevalence of the disease. In 1904
the Report on the Health of Cornish Miners, by Dr. J. S. Haldane
and Messrs. Martin and Thomas, put the position from the Cornish
standpoint. This Report contains the statement that the great
increase which had occurred in recent years in the death rate
amongst miners living in Cornwall had been due to the deaths of
men who had worked rockdrills, and that " the great majority of
these deaths are attributable to the effects of rockdrill work in the
Transvaal or elsewhere abroad ", although " a considerable number
are attributable to work in Cornwall ". One may believe that
there was truth on both sides and the exceptional danger of rockdrill
work in the Transvaal remained common ground.
The Transvaal Commission found that, although cases of miners'
phthisis were chiefly noticeable amongst rockdrill miners, they were
also found amongst miners who had never worked with rockdrills.
The men affected were mostly younger men, their average age being
thirty-five and a half years. The limited evidence available showed
that the rockdrill miners affected by the disease, who had worked
only in the Transvaal, had had an average underground service of
under six years. The Report on the Health of Cornish Miners gives
an average duration of service of 4.7 years for affected men who
had worked only in the Transvaal.

WITWATERSRAND : HISTORY OF SILICOSIS

183

The very dusty conditions then prevalent underground are
shown by several gravimetric measurements published in the
Commission's Report, which, although few in number, may be
taken as fairly reflecting the position then existing. One may
quote the following—the figures are milligrams per cubic metre
of air: stopes, 14 and 32; raise, 164; face of drive, 192 and 424.
The mines were very dusty, and they were also largely dry.
The sanitary conditions underground, especially in disused
workings, were found to be frankly bad; no attempt at organised
sanitation was made.
TYPE OF SILICOSIS PREVALENT AT THIS PERIOD

The type of silicosis produced by these conditions is described
in a statement by the Transvaal Medical Society which the
Commission published in full, and is illustrated also by the somewhat
crude but nevertheless effective coloured plates attached to the
Report. It was the " classical " type of silicosis, with heavy
bulky lungs characterised by an excessive development of
pathological fibrosis, which tended to obscure evidence of coincident
infection, except as a rule in the terminal stage. Death occurred
in either of two ways, by cardiac failure with dropsy and without
emaciation or obvious signs of tuberculosis, or, on the other hand,
by a rapid terminal tuberculosis. Local medical opinion at the time
was that the majority of cases were " non-tubercular ", although a
" mixed fibroid and tubercular type " was recognised. Probably
this conclusion was partly due to the migratory character of the
early mining population; many of the deaths which occurred did
so after the return of the men to their homes overseas. But
Dr. J. S. Haldane and his colleagues, speaking from experience in
Cornwall, were emphatic that, in the majority of cases, including
returned Transvaal miners, death was due to tubercle. Obvious
tuberculosis was however typically a late phenomenon. One
should probably relate the " classical " type of silicosis seen in these
years, in which the changes due to dust immensely predominated
over obvious changes due to infection, mainly to the kind of
occupational conditions existing, but to some extent also to the kind
of miner who was exposed to these conditions. The miners of that
time were drawn almost exclusively from older mining centres which
had long been industrialised and they had presumably therefore
a relatively high inherited or acquired immunity to tuberculosis.
They were for the most part men of initially robust physique.

184

PAPERS PRESENTED TO THE CONFERENCE
PREVENTIVE MEASURES ADOPTED

Certain general recommendations regarding dust prevention,
particularly in development work, and regarding ventilation and
underground sanitation, and the provision of " change houses " for
miners, were made by the Commission. A phrase in the Report
of the Transvaal Medical Society—" dry mining must as far as
practicable become wet mining "—reflected contemporary opinion
and indicated the main direction in which measures of dust
prevention on the Rand have proceeded ever since.
As a result of the Commission's work certain Regulations were
issued in 1904 and 1905, under Act No. 54 of 1903.
These Regulations required that sprays or jets were to be used
with machine drills, that broken ground was to be damped in
development places, and that blasting operations should be arranged
so as to avoid exposure to dust, and they prohibited return to
working places after blasting until the air was clear. Efficient
ventilation was to be provided.
But, unfortunately, no effective means were prescribed to ensure
that these measures should be actually carried out, and the inborn
conservatism of the miners, who disliked innovations in traditional
ways of working, did not help matters. A considerable improvement was unquestionably effected in the directions indicated,
but it was not sufficiently thorough to produce very substantial
results. The idea remained that the main cause of the trouble was
rockdrilling and that rockdrill miners were almost the only sufferers.
The very dangerous conditions produced by the widespread dissemination of blasting dust received quite inadequate attention.
OCCUPATIONAL CONDITIONS IN THIS PERIOD

The period 1901 to 1910 brought many " deep level " mines
to the producing stage and the main changes in occupational
conditions and mining methods during this period may be summarised as due to the greater depth and wider extension of the
mine workings. The restricted area of many of the old " outcrop "
mines combined with the fact that the dip of the reef was found
to be considerably less in the deeper workings gave rise to a
number of amalgamations of the smaller properties. Thus, whilst
the tonnage hoisted and the gold produced rose steadily year by
year, the actual number of mines on the Witwatersrand decreased.
The average grade of the ore mined fell, and it became obvious
that only those properties which could work on a large scale and

WITWATERSRAND : HISTORY OF SILICOSIS

185

held a large area for exploitation could survive for any length of
time. These amalgamations obviously had a marked effect on
mining methods and also caused a great change in the mine
ventilation. Boundaries between the small properties were stoped
out, and even where this did not occur holings became increasingly
frequent. As a result, the course of the natural ventilation
currents underwent many changes. Although the result in
individual cases was distinctly beneficial, yet the lasting effect
of the many holings was definitely detrimental to a lay-out
providing for efficient ventilation of all the working places. This
heritage in the course of years became more serious, and at a
later stage, when mechanical ventilation had to be resorted to,
it was found that radical changes, though desirable, could not be
effected except at a prohibitive cost.
The evidence of various dust samples taken during this period
shows that dust conditions remained in general of much the same
order as regards dangerous dust as they had been in 1903.
Much credit is due to the Chemical Metallurgical and Mining
Society of South Africa for the active attention devoted by its
members to the subject of miners' phthisis during these years,
which served a very valuable educative purpose. The discussions
which centred round papers contributed particularly by
Drs. Macaulay and Irvine, Dr. James Moir and Mr. W. Cullen did
much to extend the knowledge of the mining community regarding
the nature and danger of miners' phthisis, to elucidate the nature
of accidents from " gassing " underground, and to direct attention
to the question of mine ventilation.
THE MINING REGULATIONS COMMISSION,

1907-1910

In 1907 a second Commission was appointed by the Government
of the Transvaal—the " Mining Regulations Commission ". Its
primary reference was to revise and suggest amendments to the
Mining Regulations; and in this connection its members devoted
much attention to miners' phthisis, to the question of " gassing "
accidents in the mines, and to mine ventilation and sanitation.
Medical evidence was led by Drs. Macaulay and Irvine on the
" Conditions affecting the Health of Underground Workers ", and
by Dr. G. A. Turner on the " Health of Mine Natives ". From
the evidence submitted by the former it was found that the local
mortality from phthisis during the years 1905 to 1907 had been
approximately six times higher amongst underground workers

186

PAPERS PRESENTED TO THE

CONFERENCE

than amongst other adult males on the Rand, but that the age
period of maximum mortality fell somewhat later amongst the
former, a feature which is recognised to. be characteristic of
" dust-phthisis ".
The final Report of the Mining Regulations Commission was not
issued until 1910. A revised code of Mining Regulations, based
upon its recommendations was promulgated in 1911, and instituted
many improvements, which began to take effect from the latter
date and which represent the inauguration of the next period.
The chief of these improvements were the introduction of
qualitative tests of ventilation, to supplement the quantitative
requirements of older Regulations, and power was given to require
the introduction of mechanical appliances where the natural
ventilation current was insufficient. As before, the use of a water
jet or spray was required in machine drilling; and the responsibility
of the manager to maintain an adequate and constant supply
of clean water for use for these appliances and for damping down
working faces and broken rock in ends and stopes, was tightened up.
An important innovation was the requirement that a " water
blast or other suitable appliance " should be used in development
ends to control dust from blasting, and further provision was made
for the protection of all persons in the mine from fumes and dust,
and for the prompt hauling of coloured labourers to the surface
at the end of the shift. The ventilation of winzes was specially
provided for. Responsibility was placed on the sectional officials
to secure the proper observance of preventive regulations. Finally,
back-to-back living rooms on the surface were prohibited, and
underground sanitary organisation received detailed attention.
The result was that the use of water for dust-laying underground
became from this time much more general. The following figures
show very strikingly the effect of these measures, and the conditions
existing at this time of transition.
DUST IN MILLIGRAMS PER CUBIC METRE
(Samples

taken at the Bottom of an Upcast Shaft in a Deep-level

9 to 10 a.m.
11.30 a.m. to 12.30 p.m.
2 to 3 p.m.
4.15 to 5.15 p.m.

Mine)

Sept. 1911:
No sprays

April 1912:
Sprays

Sept. 1912:
Sprays

280
130
80
100

32
21
39
14

3.3
0.2
2.1
17.1

WITWATERSRAND: HISTORY OF SILICOSIS

187

An important event which is to be referred to this period was
the opening in November 1911 of the Miners' Phthisis Sanatorium
at Springkell, the capital expenditure being provided by the
Transvaal Chamber of Mines. This institution has ever since
filled a most valuable purpose in providing free special medical
treatment of cases of miners' phthisis.
At the close of this period in 1910, the number of mines working
was eighty-four. These mines were hoisting nearly 27,000,000 tons
of rock per year. The white underground employees numbered
over 10,000; coloured underground employees over 120,000. The
average stoping depth was 1,100 feet; the maximum depth reached
at this time was 4,500 feet. Some 5,500 rockdrills were in
commission: all or nearly all were of the " dry " reciprocating type.
III. — Period of Introduction of a Legal System of Compensation
for Silicosis and of Trial of More Systematic Preventive
Measures, 1911 to 1916

The new Code of Mining Regulations published in 1911, which
introduced this period, has already been noted. The important
matter of hours of work underground was also dealt with at this
time under Act No. 12 of 1911, which limited work at the face to
eight hours per day and forty-eight hours per week. This had the
effect in practice of an eight-and-a-half-hour day from bank to
bank 1 . The same year, 1911, witnessed also the first institution
of a legal system of compensation for the disease. In the first
session of the Union Parliament the Minister of Mines introduced
a preliminary measure—the " Miners' Phthisis Allowances Act
of 1911 "—to provide temporary relief for men affected, pending
more extensive legislation.
A " Miners' Phthisis Board " was appointed to administer the
Act, and this body, with various subsequent changes in composition,
still performs this very important office.
At the same time (June 1911) a further Miners' Phthisis Commission was appointed, composed entirely of medical men and hence
known as the " Miners' Phthisis (Medical) Commission ", " to
enquire into the prevalence of miners' phthisis and tuberculosis
on mines within the Union ", and to advise from the medical
point of view on provisions for legal measures for compensation.
1
The practice since 1918 has been to work eight and a quarter hours bank
to bank on weekdays and seven and a quarter hours on Saturdays.

188

PAPERS PRESENTED TO THE CONFERENCE
THE MINERS' PHTHISIS (MEDICAL) COMMISSION,

1911-1912

The Report of the " Medical " Commission, issued in February
1912, forms the second landmark in the medical history of silicosis
in South Africa.
The actual examinations made were more complete than in 1903,
but they did not cover the whole of the underground employees.
A general clinical examination was made of 3,136 working miners,
supplemented by a special examination of 326 men, in which
radiography was for the first time applied to the examination of
cases on a fairly extensive scale by Dr. A. H. Watt, at the Simmer
and Jack Hospital.
By these means the prevalence of definite cases of the disease
amongst the working miners examined was found to be about
26 per cent., with an additional 5.5 per cent, of doubtful cases.
This figure is somewhat higher than that found in 1903. It gives
no reason, however, to conclude that the situation had retrogressed,
since the earlier date; it probably merely reflects the result of a
more extensive investigation.
Machine drillers were still the occupational group most affected,
and the Commissioners concluded that, regarding this group, the
statement made in the Report of the Transvaal Medical Society
in 1903, that " the working efficiency of a rockdrill miner working
under present conditions would be impaired or even exhausted
after seven to nine years' work ", still held good. Although other
occupational groups showed much lower attack rates, no class of
underground workers, including the supervisory staff, was free
from serious risk of attack. The importance of the factor of
tuberculosis in the course of the disease was fully recognised in
the Report, in which it is stated that " in at least the great
majority of cases tuberculous infection becomes towards the end
superimposed upon the pre-existing silicosis ". The Report adds
that " there has been undoubtedly since 1902-1903 a distinctive
alteration in the predominant clinical type of the disease ".
The average duration of underground service in the whole class
showing the first definite physical signs of the disease was 8.2 years,
and the average age of those so affected 35.5 years : for machine-men,
with South African experience only, the average duration of service
was 6.1 years.
It was suggested that, for purposes of compensation, cases should
be divided into three stages : early, intermediate and advanced, and
that for the two latter a pension or annuity should be payable.

WITWATERSRAND: HISTORY OF SILICOSIS

189

Pure tuberculosis was found to be comparatively rare amongst
miners at work, and while the Commissioners were agreed t h a t
" miners' phthisis " was definitely an " occupational " or " industrial " disease, they were also agreed t h a t pure tuberculosis could
not be so regarded.
THE

MINERS' PHTHISIS ACT OF

1912

The Report of the Medical Commission was the basis of the
" Miners' Phthisis Act of 1912 ", which introduced for the first
time a system of legalised compensation for the disease.
This Act has proved to be only the first of a long series of
subsequent amending and consolidating measures, each of which
has been marked in general by an increase in the amount of the
awards payable to fresh cases, and by additional provision for
surviving beneficiaries under former Acts, or for the dependants
of deceased miners. It is unnecessary to trace the development
of this complicated mass of legislation in detail, but some reference
may be made to certain of its general aspects.
The system adopted in the Act of 1912 is of interest principally
because it marked a definite policy, which has since been superseded.
Two " stages " of the disease were recognised—a " first "
applying to " a miner who shows definite physical signs of miners'
phthisis and whose capacity for underground work is thereby not
seriously or permanentlym ipaired ", and a " second " applying to
" a miner who has contracted silicosis in a marked degree and
whose physical capacity for underground work is thereby seriously
and permanently impaired ".
Sums (whose total amount was limited) were paid for each stage
in instalments. The miners contributed 2 % per cent, of their
wages towards the liabilities.for these payments in respect of new
cases, and this system was continued until 1919. No award
was payable to cases of pure tuberculosis.
A panel of medical examiners was appointed to carry out the
medical examinations of European claimants and to certify as to
their eligibility for an award. Natives suspected to be suffering
from miners' phthisis were examined and certified by the Mines'
Medical Inspector. The former system led to a considerable lack
of uniformity in the standards of certification adopted. Increasing
use was made by some examiners of radiography to supplement
clinical examination, but this was far from general. Only those
miners who made voluntary application for benefits were examined.

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PAPERS PRESENTED TO THE

CONFERENCE

and no periodical examination of all working miners was provided
for. Although a medical examination of new recruits was
authorised, this also suffered from a very considerable lack of
uniformity.
INCIDENCE OF SILICOSIS IN THIS PERIOD

The number of awards of benefit granted in these years to
working and retired miners was very considerable and is shown
in the accompanying table:
ORIGINAL AWARDS TO MINERS FOR SILICOSIS MADE BY THE MINERS'
PHTHISIS BOARD FROM 1 9 1 2 TO 1 9 1 6
Year

First stage

Second stage

Total

1912-1913
1913-1914
1914-1915
1915-1916

698
1,087
912
540

1,632
993
367
243

2,330
2,080
1,279
783

1912-1916

3,237

3,235

6,472

At the outset of the period there existed a large number of
" accumulated " cases amongst working and retired miners.
If we make an allowance of 3,000 as the approximate number of
these, the figures would suggest that some 800 to 900 new cases
were arising in each year during this period. That this approximate
estimate is probably fairly near the truth is further suggested by the
fact that, after nearly 6,500 working or retired miners had thus been
compensated during these four years and debarred from further
underground work, the Bureau detected over 900 cases of
" primary " and " secondary " stage silicosis amongst miners who
were actually at work during 1916-1917. These facts indicate
that the incidence of the disease at this period was decidedly worse
than it has since become. It must be remembered that even the
new cases arising during these years would on the average represent
the cumulative effect of occupational conditions the beginning of
which dated back to some eight or ten years previously.
The lack of uniformity in the medical standards of certification
employed by different members of the " panel " of examiners,
and of systematic means for the detection of fresh cases as they
arose, resulted in a general feeling that the system adopted in 1912

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191

was unsatisfactory. In 1916, accordingly, a Parliamentary Select
Committee was appointed to reconsider the position. The Report
of this body recommended the adoption of an altogether different
policy.
One may note here that contributions to the local literature of the
subject were made during this period by Dr. J. McGrae (1913),
by Dr. W. Watkins Pitchford (1914 and 1915), and by Drs. Watt,
Irvine, Pratt Johnson and Steuart (1916).
PROGRESS OF PREVENTIVE WORK FROM 1912

1916

Following on the Report of the " Medical " Commission the
Minister in February 1912 had appointed a " Miners' Phthisis
Prevention Committee " under the chairmanship of Sir Robert
Kotze. This body was an authoritative and representative one,
composed of Government mine inspectors, mining engineers and
mine managers representing the industry, working miners, medical
men and other technical advisers. It was appointed " to enquire
into and report upon methods for the prevention of miners' phthisis,
and to advise on the introduction of a systematic and uniform
policy ".
The composition of the Committee afforded an
opportunity for continued close co-operation in preventive work
between the Department of Mines and the industry. It may fairly
be said that " the formation of this Committee marks the initiation
of the first really energetic steps to stamp out the disease ". Two
interim Reports were issued by the Committee in 1912 and 1913, in
which urgently needed steps were indicated. In 1913 a large
number of Regulations were promulgated incorporating these
recommendations. In addition to amplifying and more accurately
defining existing Regulations, additional provisions were introduced.
In 1913 it was required that an adequate supply of water should be
provided throughout each mine by means of a system of pipes. This
cardinal requirement led to much greater efficiency and uniformity
in the provision of water for use with sprays and jets and waterblasts, and for wetting working-places and broken ground, and hence
to a more extended and adequate application of these methods.
In 1914 a further Regulation prohibited the blasting of " cut " and
" round " separately on one shift, except by special permission of the
Inspector of Mines. The practice so restricted had long been
recognised as a peculiarly harmful and dangerous one.
Regular determinations of the dust in mine air had been begun
by the Consolidated Goldfields Group in 1911. The first systematic

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dust survey of all the mines was conducted by the Prevention
Committee in 1913-1914.
The general average result was
5.4 milligrams per cubic metre of air, the highest results being found
in raises, drives and at orebins. These figures are much below the
values of earlier observations, but still very considerably higher
than recent results. In 1914 the Chamber of Mines established
a special Dust Sampling Committee under the charge of Mr. James
Boyd, and systematic surveys of workings in all mines have been
carried out since that date by that Committee. In addition, since
1916 each mine has conducted its own dust surveys. The body
of evidence so collected is now enormous, and provides useful
guidance regarding dust conditions.
The method of dust sampling first employed was the gravimetric
sugar-tube method, used with screening in order to exclude very
large particles. In 1916 Sir Robert Kotze introduced a dustsampling instrument which he named the " Konimeter ". In that
device a measured quantity of the air to be examined is made to
impinge on an adhesive-coated microscopic slide, and the number
of particles in the " spot " so produced is subsequently counted
under the microscope.
For long there was controversy as to the relative merits of
the sugar tube and the konimeter. It may be agreed that no
one method of sampling the air for dust is satisfactory in all
respects. The phthisis-producing properties of dust particles
depend upon their size and upon their quality. Sugar tube or
gravimetric methods do not discriminate size, and konimetric or
optical methods do not discriminate quality.
The konimeter has two great advantages for routine work: a
low konimeter count means safe conditions, while this does not
necessarily apply to a low sugar-tube return. Further, the
konimeter is handy, and can be used in observing rapidly changing
dust conditions. The methods of konimeter work are at present
being investigated with a view to standardisation by a Joint
Committee of the Department of Mines and the Chamber of Mines.
There can be no doubt of the value of this instrument, when
properly used, for giving approximately accurate relative results
which will serve as a sufficient guide for most practical purposes.
OCCUPATIONAL CONDITIONS DURING THIS

PERIOD

During the years 1911 to 1916 mining methods on the Witwatersrand underwent a number of changes notably as regards

WITWATERSRAND: HISTORY OF SILICOSIS

193

the lay-out of the mines, the ventilation systems and the type of
machine-drill employed.
The greater depth to which the workings had penetrated, as
well as the larger area over which they had extended necessitated
larger shafts and development ends. It was also realised t h a t
in order to handle the increased tonnages and to improve ventilation,
the drives and cross-cuts had to be laid out on as straight lines as
possible, although the great bulk of the underground tramming
was still being done by hand.
A more radical change took place in the ventilation systems
of mines. In 1908-1909 the first large mechanical fans were
installed on some mines and during the next decade all the deeper
mines found it necessary to follow suit in order to clear the workings
of fumes from blasting. The importance of ventilating currents
in reducing the residual fine dust in the mine air had not yet
been fully realised, when mechanical ventilation was installed.
An important change in the type of machine-drill came about
when the reciprocating drill was superseded by the hammer type
of drill. The latter was smaller and lighter, and thus more easily
handled and its drilling speed was also considerably greater. The
holes drilled by these machines, were smaller in diameter but
not only did the new machine drill more holes per shift than the
old one, but in striking a larger number of blows per inch drilled,
it also pounded the rock very much finer than did the reciprocating
machine, and thus produced a greater proportion of fine dust.
In addition, some types of hammer drill exhausted air only through
the drill steel, with the result that excessive quantities of microscopic
particles of dust were disseminated in the mine air, in spite of the
fact that water was applied externally to remove the sludge from
the drill hole. This new position had to be met by investigation
into the use of air, or air and water, or water only with rock-drilling
machines.
T H E GENERAL POSITION IN

1916

One may note here an important development which had been
going on during this period and the later years of the previous one.
In 1903 over 90 per cent, of the miners employed on the Rand
were men of overseas origin and the great majority of these had
had previous mining experience elsewhere. But a steady increase
had been proceeding since that time, particularly since 1907, in
the number and proportion of miners of South African birth and
training. It was noted by the Miners' Phthisis Medical Commission
13'

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PAPERS PRESENTED TO THE CONFERENCE

in 1911 that in that year, 35 per cent, of the miners examined
were South African born, and that, although 65 per cent, were
of overseas birth, only 19 per cent, of the whole number examined
had had previous mining service elsewhere. To-day 73 per cent.
of the working miners are of South African birth, and 91 per cent.
of the whole body have had their experience of mining solely in
South Africa. The position has therefore been completely reversed
since 1903. The industry has become throughout a genuinely
South African industry. The recruits of South African birth have
been drawn mainly from the rural community. It may be suggested
that the presumably lower acquired immunity to tuberculosis in
a population of this origin, may have contributed, along with the
progressive reduction of dust in mine air, to the greater and
earlier relative prominence of the element of tuberculous infection
in our local cases, which had already begun to be noticeable before
1916.
The number of mining companies at work in 1916 was fifty-five.
They employed underground over 11,000 Europeans and over
155,000 coloured employees. The rock hoisted per year was
32,000,000 tons. During the period the number of rock-drills in
commission had increased from. 5,500 in 1910 to 9,500 in 1916,
and 40 per cent, of the rock mined was broken by rock-drills. The
average stoping depth was 1,600 feet; the maximum depth reached
was 5,250 feet.
IV. — Period of the " Present Day " System of Fully
Systematised Detection and Prevention
The year 1916 was a cardinal year in the history of silicosis
on the Rand. It was marked by two new departures—the
institution of the Miners' Phthisis Medical Bureau, and the publication of the General Report of the Miners' Phthisis Prevention
Committee. From 1916, therefore, we may suitably date the
period of the " present day " system of detection and prevention
of silicosis on the Rand.
THE MINERS' PHTHISIS ACT OF 1916 AND THE INSTITUTION
OF THE MEDICAL BUREAU

The Miners' Phthisis Act of 1916 was the outcome of the Report
of a Parliamentary Select Committee which sat in that year.
This Act continued the previously existing system of limited

WITWATERSRAND : HISTORY OF SILICOSIS

195

awards for two " stages " of silicosis, but the amounts granted
were increased in this year, and still further in the succeeding
year. The two " stages " were now termed " primary " and
" secondary ". The interpretation given to the definition of the
" primary " stage by the legal advisers of the Crown was that it
should be held to include only such cases as showed some amount
of disability; an interpretation in conformity with the general
usage regarding cases of industrial " injury ". The basis of
compensation may have been temporarily somewhat affected by
this decision.
A further step was taken by the inclusion under the Act of cases
of pure tuberculosis when detected amongst miners actually at
work. It was not conceded that pure tuberculosis is an occupational
disease: the object was to remove from underground work cases
of tuberculosis which were actual or potential sources of the
communication of infection to others, and the award was granted
to the affected miner simply in view of compulsory retirement
from his occupation. The grant was originally made only to
cases detected amongst miners at work during a period of one
year from the date the system came into force. Later amending
legislation, however, ultimately established the privilege of a
miner to claim compensation for simple tuberculosis, provided
that the condition is detected by the Bureau in a miner who is
actually at work underground in a scheduled mine, or who has
been so employed within not more that twelve months prior to
the date on which the disease was detected.
Perhaps the most important innovation introduced by the Act
of 1916 was the institution of the " Miners' Phthisis Medical
Bureau "—as a central body of whole-time Government medical
officials to conduct or control all medical examinations under
the Act.
In the case of European miners the main functions of the Bureau
have been:
(1) To conduct an " initial examination " of all new recruits for the
industry;
(2) To conduct a " periodical examination " of each working European miner once every six months in order to secure the early
detection of all cases of silicosis or tuberculosis which arise
amongst the working miners ;
(3) To conduct a " benefits examination " of all miners or ex-miners
who claim compensation in respect of the presence or suspected
presence of silicosis or tuberculosis, and
(4) To decide from the medical standpoint upon the claims of dependants of deceased beneficiaries.

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PAPERS PRESENTED TO THE CONFERENCE

In the case of native mine labourers, the " initial " and
" periodical " examinations are conducted under Regulation by
the mine medical officers acting as examiners under the Act.
The Bureau, however, exercises general powers of supervision
over these examinations and is directly reponsible for the
examination and final disposal of all natives suspected by the
mine medical officers to be suffering from silicosis or tuberculosis.
The first Chairman of the Medical Bureau was Dr. W. Watkins
Pitchford, on whom the heavy work of the initial organisation
of that institution fell. Dr. Watkins Pitchford continued to direct
the activities of the Bureau for a period of ten years up to
September 1926, when he was succeeded by the present Chairman
(Dr. L. G. Irvine).

SUBSEQUENT CHANGES IN THE PRINCIPLES OF LEGISLATION
ON MINERS'

PHTHISIS

Acts affecting minor changes in the system of compensation
were passed in 1917 and 1918. Accumulating experience of the
progressive character of most cases of silicosis gave support to
the feeling that cases of silicosis should become eligible for
compensation ,at the earliest detectable stage of that condition,
irrespective of whether disability was present or not. It was
hoped that, if this were done, the disease might be detected, and
the men be given the opportunity of leaving underground work,
while the condition was still non-progressive. This principle was
therefore adopted in the Miners' Phthisis Act of 1919, which
was the outcome of a further reconsideration of the problem by
a third " Miners' Phthisis Commission " (1918) and by a
Parliamentary Select Committee. Since the earliest stage of
silicosis compensated under the previous Acts had been termed
the " primary " stage, the somewhat anomalous expression " anteprimary " stage was introduced to designate the earlier condition
which it was now intended to render compensatable. In this
Act also simple tuberculosis was finally recognised, under the
restrictions already mentioned, as a compensatable condition in
miners. Judged from the preventive aspect, the wisdom of that
decision is, we think, unquestionable. A further change of
importance was the provision of a maintenance life pension for
miners who had reached the " secondary " stage of grave
incapacitation, with an allowance for their wives and children.

WITWATERSRAND : HISTORY OF SILICOSIS

197

The " ante-primary " and " primary " stages were made compensatable by limited lump sum payments. Holders of a periodical
certificate were entitled to remain eligible for a periodical examination provided that they presented themselves for examination
at intervals not exceeding two years.
Minor amendments were effected in 1918 and 1924; a further
. Commission—the " De Villiers Commission "—re-examined the
situation in 1921 ; and finally, in 1925, a new consolidating Act was
passed—the " Miners' Phthisis Acts Consolidation Act of 1925 ",
This measure aimed mainly at " levelling up " the awards granted
to beneficiaries under the previous Acts to the scales of award
instituted for new cases in 1919. The Act also required that medical
officers appointed by mining companies to attend mine natives
should be whole-time officers, power being reserved to the Minister
to allow exemption in the case of small mines. This measure has
tended to a more uniform and effective system of medical
examination of natives for the purposes of the Act. Finally a
" Medical Board of Appeal " was appointed with power to revise
decisions of the Medical Bureau in respect of any examination at
which the question of possible compensation was involved. This
provision was made to meet the case of persons dissatisfied with the
decisions of the Medical Bureau, and has added elasticity to the
whole system. It cannot be said that complete satisfaction with
the present system has been attained, and at present another
Miners' Commission is once more reviewing the situation.
One may note here that further contributions to the literature
of the subject have been made since 1916, particularly by
Dr. A. Mavrogordato (1922 and 1926) and by Dr. W. Watkins
Pitchford (1927).

THE

" GENERAL "

AND

" FINAL "

REPORTS

PHTHISIS PREVENTION COMMITTEE, 1916

OF THE
TO

MINERS'

1919

The publication of the General Report of the Miners' Phthisis
Prevention Committee in 1916 forms the second feature which
makes that year a landmark in the local history of silicosis. This
Report and the Committee's Final Report of 1919 contained a large
number of further detailed recommendations aimed at the
prevention of miners' phthisis. The work of that Committee was
not, however, confined to the issue of general recommendations.
Perhaps its most important work lay in the detailed survey of all

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PAPERS PRESENTED TO THE CONFERENCE

mining operations which it accomplished and the formulation of a
detailed policy of dust control for each of these, the careful
investigation of actual appliances suggested or in use for dust
prevention which it carried out, and the illustrations published of
those appliances which appeared best to meet their purpose. The
Chairman of the Committee, Sir Robert Kotze, was, throughout the
period of its sittings, in close touch in these respects with the officers
of his department and with the technical advisers of the industry.
An amended code of Mining Regulations, issued in 1917, embodied
the cumulative result of the Committee's work.
Perhaps the most important additional measure introduced
in 1917 was the provision that blasting should take place only once
in twenty-four hours, at the end of the day shift. Blasting the " cut "
and "round " separately on the same shift was now totally
prohibited. Other related provisions were that work and shifts
should be so arranged as to avoid exposing persons to fumes and
dust from blasting, and that the night shift should only enter the
mine after the lapse of an interval fixed by the Inspector of Mines.
For control of the dust generated in blasting only an approved
water blast was permitted.
The Regulations relating to ventilation were amplified. It was
required that a prescribed minimum quantity of air must be
provided for every person employed underground, and that the air
must be suitably " split ". Special requirements were made
restricting back-stoping, and for the special ventilation of
development ends. For machine drilling only a jet or a drill with
axial water-feed was permitted.
Finally, it was provided that a special dust and ventilation officer
should be appointed for each mine, and that regular dust
determinations should be made.
In 1918 there followed Regulations enforcing dust prevention
in crusher stations and assay rooms.
Subsequent to 1919 further investigations with effect in practice
have been made by two Joint Committees appointed by the
Department of Mines and the Chamber of Mines for special purposes
•—one on " Water Blasts and Ventilation " was appointed in
1921, and the second, on the " Ventilation of Development Ends "
in 1923.
In 1921 a Regulation was promulgated giving the Government
Mining Engineer control over the types and makes of machine drills
which may be used on " phthisis " mines. Since then no new
machine drill may be introduced without the prior approval of the

WITWATERSRAND: HISTORY OF SILICOSIS

199

Government Mining Engineer, and a system of testing drills with
regard to dust production has been established. The principal
outcome of this provision has been that the use of machine drills
not provided with an axial water-feed has been prohibited since 1926.
In 1916 the majority of rockdrills in commission were still of
t h e " dry " reciprocating type. In 1918, 10,500 rockdrills were
in use of which nearly half were of the hammer type, and 40 per cent.
of these were " dry " drills. In 1928 the reciprocating type had
practically disappeared, and 8,500 hammer drills, all of the " wet "
type, were in commission.
To ensure observance of the Regulations inspections of the
mines are being constantly made by the Government mining
inspectors, who in many of their inspections aid their ordinary
observation by taking dust samples with the konimeter. Control
is also exercised by the industry itself through the Dust Sampling
Committee of the Chamber of Mines, whose inspectors make
routine sampling visits to the mines, as well as visits to obtain
samples in connection with particular observations. The samples
are taken either with the sugar tube or konimeter. They are
examined at a laboratory maintained by the Chamber for t h a t
purpose, to which also the samples taken by the dust samplers
on the individual mines are sent for examination and report.
Finally, the Minister in 1926 appointed a second Miners' Phthisis
Prevention Committee, similar in constitution to the first, to carry
on similar work.

OCCUPATIONAL CONDITIONS SINCE 1916 AND THE P R E S E N T POSITION

The development of that portion of the Witwatersrand goldfields
situated between Benoni and the village of Nigel and popularly
known as the " Far East Rand ", did much to change the ventilation
systems on the Witwatersrand. The areas of individual mines
on this portion of the Rand are considerably larger than were those
of the older mines. The reasons for this fact may be briefly
indicated as follows:
These areas were known to contain extensive unpayable blocks
of ground, the reef lay at depth without outcrops to the surface
except in the extreme North West and South East, the dip of the
reef was small, and a large amount of virgin ground was rendered
available under the mining leases system.
As a result very little, if any, natural ventilation could be

200

PAPERS PRESENTED TO THE CONFERENCE

hoped for, and the lay-out of the mines had therefore to be adapted
to the requirements of mechanical ventilation. Again, efficient
handling of the broken rock underground could only be obtained
by means of mechanical haulages requiring large haulage-ways
with the minimum of bends or constrictions, and thus also facilitating
improved ventilation.
As a mining field the Witwatersrand to-day stands unequalled
as regards the scale on which operations are carried on, the depth
the workings have attained, the organisation involved, and the
extent of the precautions taken to prevent miners' phthisis. Visible
dust underground is as rare as it once was common, exposure to
fumes from blasting if occurring at all is accidental, and sustained
efforts are being made to provide improved ventilation.
The main difficulties encountered lie in the fact that the lay-out
of many of the older mines is unsuitable and the necessary alterations
could not be effected except at prohibitive cost. Although a
great amount of attention is now paid to ventilation requirements
in the original lay-out, the enormous expense of shaft sinking
resulting from the great depth of the shafts and the hardness
of the rock limit the area of the shafts very considerably. The
danger of rock-bursts, the large unpayable areas which have to be
driven through on certain mines, the close packing required for
support, the narrow width at which stoping must be carried out
in some mines in order to be payable, and the fact that the large
ore reserves must be blocked out in advance are further factors
which tend to limit the cross-sectional areas of these underground
excavations, along which the main downcast current has to travel
before reaching the actual working faces.
Again, these very working places are so scattered that extensive
splitting of the air current is necessitated on most mines. A further
complication arises from the fact that relatively few mines can be
regarded as separate units as regards their ventilation systems.
Holings into neighbouring mines are continually increasing,
boundary pillars are being removed and the ventilation system of
two or more mines must frequently be treated as one composite
problem. On most mines the workings are interconnected to
such an extent as to make the circulation of a main air current
extremely difficult and costly. If the dust content of widely
scattered stopes and development ends, in the latter of which
most dust is created, is to be efficiently diluted, a good deal more
ventilation will be required in such places, and on some mines
the cost would be prohibitive.

WITWATERSRAND : HISTORY OF SILICOSIS

201

At the present time the number of mines working on the Witwatersrand is forty-five but of these nine are small tribute companies
working portions of mines which had previously been shut down.
The number of European miners employed is over 10,000 and
of underground coloured employees over 147,000. The tonnage
hoisted is over 36,000,000 tons per annum, practically all of which
is broken by rock drills. The average stoping depth is 2,700 feet.
The maximum depth attained is 7,638 feet (October 1929).

T H E C H I E F FACTORS IN PREVENTIVE POLICY SINCE
AND THEIR

1916

RESULTS

Following the summary review outlined in the last Report of
the Medical Bureau one may say that since 1916 four kinds of
preventive methods have combined to influence the situation.
Two of these make up what one may call the "engineering
methods " aimed directly against the production or dissemination
of dust in mine air. One may perhaps conveniently distinguish
these as:
(1) " Dry " methods of prevention, by which one means measures
which do not directly depend upon the use of water. These are the
measures, already described, to secure an adequate standard of ventilation both general and local, to regulate the methods and times of blasting,
to secure the arrangement of shifts and the times and manner of hoisting
so that there should be no unnecessary exposure of any person to dust
and fumes, and measures of a similar character. The general tendency
to think of the use of water as the all-important measure in dust prevention has perhaps tended to an under-estimation of the cardinal importance
of the provisions just mentioned.
(2) " Wet " methods of prevention, by which one means measures
which depend directly on the use of water to allay dust at its source,
or to remove it from the air when formed. Every mining operation is
now covered by meticulous regulations having this object, of which we
have already mentioned the chief. When in 1916 the Miners' Phthisis
Prevention Committee found that the adequate use of water suitably
applied would reduce the amount of dust generated in drilling and
blasting by 97 or 98 per cent, by weight, it appeared that the problem
had been solved. It had only been solved so jar. The further statement
made by the Committee that water would lay the dangerous dust in
equal proportion to the coarser harmless dust has since required, and in
our opinion still requires, re-investigation. •
There is no doubt that the combined operation of these two
groups of preventive measures has effected an immense reduction
in the quantity by weight of dust in mine air. One may in illustra-

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PAPERS PRESENTED TO THE

CONFERENCE

tion quote the following results of the gravimetric observations
made by the Dust Sampling Committee of the Chamber of Mines:
Year
General average
Development
Stopes
Orebins
Total samples
Percentage of samples
above 5 milligrams

1915

1917

1919

1921

1923

1925

1927

4.9
6.9
3.4
4.4
1758

3.8
5.4
2.9
4.2
6188

2.4
3.5
1.9
2.9
7491

1.6
2.3
1.2
2.1
6695

1.3
1.9
0.9
1.8
4872

0.9
1.0
0.7
1.6
2399

1.2
1.2
0.9
1.9
2869

27.0

20.0

10.0

4.0

3.4

1.7

1.4

Figures represent milligrams per cubic metre of air.

The other classes of preventive measures one may call the
" medical measures ".
Of these, two are of chief importance:
(3) The " initial examination " of recruits conducted or in respect
of native labourers controlled by the Bureau. The object of this examination is to prevent the entry into the industry of persons suffering from
respiratory diseases (including tuberculosis) or of persons who appear
to be unduly liable to contract such diseases.
A very important result of the initial examination in the case of
European miners has been the gradual introduction since 1916 into
the general body of working miners of a group of men of specially
selected physique, whom we call the " new Rand miners ", and who
now number over 8,300, or 54 per cent., of the whole body.
In the case of the mine natives there are three medical
examinations of recruits, a preliminary sifting in the recruiting area,
a principal examination at the Witwatersrand Native Labour
Association's depot in Johannesburg, and a supplementary
examination by the mine medical officers.
(4) The " periodical examination ", similarly conducted or controlled
by the Bureau, which aims at the detection of all cases of simple silicosis,
tuberculosis with silicosis, or of simple tuberculosis, amongst the working
miners and the mine natives. European miners actually in employment
are examined by the Bureau every six months.
From the purely preventive aspect the most important
consequence of the periodical examination is the permanent removal
from underground work of persons found to be suffering from
tuberculosis or tuberculosis with silicosis, who are thereby prevented
from remaining as potential sources of dissemination of infection.

WITWATERSRAND: HISTORY OF SILICOSIS

203

The number of cases of these conditions detected amongst European
miners has fallen steadily during the past ten years and does not
now constitute a serious menace.
The preventive aspect of the periodical examination is of more
importance as it affects the native mine workers.
The periodical examination of native labourers is carried out,
under the Act, by the mine medical officers, who are almost
exclusively whole-time men and are an active, organised and
progressive body. The system of examinations of natives on the
mines is rather complicated.
Every native employee is weighed once in six weeks, and all who
show more than a prescribed loss of weight are set aside for special
medical examination; all natives with more than five years' service
on any mine undergo a further special medical examination every
three months, and all natives on leaving employment have to
undergo a " final " medical examination. These are the prescribed
examinations. In addition the medical officers examine the chests
of all natives admitted to hospital for any cause. And finally the
Chamber of Mines three years ago instituted an annual X-ray
examination of long service natives. The whole system draws
round the mine natives a serviceably close net of opportunities for
detection of cases of silicosis and tuberculosis.
Suspected cases are sent to the Bureau for final examination and
disposal.
The result of the examinations of mine natives discloses that
simple tuberculosis and tuberculosis with silicosis taken together
are decidedly more prevalent amongst them than amongst the
European working miners. The reverse is true of simple silicosis.
Even so, when judged by European and American experience
the attack rate for tuberculosis amongst mine natives is not
alarming. But the actual number of cases detected annually is
considerable, and, so far as underground conditions are concerned,
it is from the mine native that the menace of tuberculous infection
arises both in the production of cases of frank tuberculosis and in
that of early infective silicosis amongst European and native
employees alike. Hence the necessity of continuing the campaign
to reduce all possible sources of tuberculous infection in the mining
population to the fullest practicable extent.
One may add that three years ago a " Tuberculosis Research
Committee ", representative of the Government and of the Chamber
of Mines, was appointed to make a fresh investigation of the
tuberculosis problem.

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PAPERS PRESENTED TO THE CONFERENCE

THE INCIDENCE OF SILICOSIS SINCE

1916-1917

What now has been the practical result of all these intensive
efforts ?
It is only duiing the past twelve years—from 1917-1918 onward—
that we have been able to obtain from the published Reports of
the Medical Bureau accurate figures regarding the new cases of
silicosis which have actually arisen year by year.
During the whole of that period of twelve years there have been
detected by the Bureau at the periodical examination of working
miners 4,362 cases of simple silicosis, 382 cases of tuberculosis with
silicosis, and 409 cases of pure tuberculosis.
Reduced to average figures these numbers represent, in the case
of simple silicosis alone, an average annual production of 363 cases,
amongst a population of 13,600 working miners, or 2.66 per cent.
The actual incidence has, however, varied considerably from
year to year. Let us attempt to follow its general course, and for
convenience let us divide the whole period into four shorter periods,
each of three years' duration.
For the years 1917 to 1920 the incidence averaged 3.5 per cent.,
but the returns for these years were inflated by the inclusion of a
considerable number of " accumulated " cases of early silicosis,
which became compensatable as " ante-primary stage " cases in
1919-1920.
Partly owing simply to the removal of these accumulated cases,
there followed in the years 1920 to 1923 a drop in production
to an average of 1.9 per cent.
The next three years, 1923 to 1926, witnessed on the other hand
a well-marked rise to an average figure of 3.3 per cent., culminating
in a maximum peak of 3.8 per cent. (490 cases) in 1925-1926, a
figure precisely double the average rate for 1920 to 1923.
This marked increase naturally attracted much attention and
aroused misgiving.
But, as was first publicly pointed out by Dr. A. Mavrogordato,
it had quite an innocent explanation. It was not attributable
to a worsening of hygienic or occupational conditions underground.
The greater part of it was due to the simple fact that the mining
population had become more settled and was growing older—older,
that is, in length of underground service. During that period,
accordingly, there had been a steady increase in the number of
miners with long periods of service behind them and with a
correspondingly greater liability to contract silicosis. Everyone

WITWATERSRAND: HISTORY OF SILICOSIS

205

knows that, other things being equal, the longer a miner has
worked underground the more liable he is to contract silicosis,
and therefore the greater the number of miners with long service
that are working the greater must be the number of cases of silicosis.
That was one thing that was happening in these years. The
remaining and lesser portion of the increase was attributable to a
different cause. It was due to a temporary augmentation of the
cases detected, occasioned by a further liberalisation in the standard
of diagnosis of the earliest recognisable stage of silicosis, attained
during these years by the Bureau, as the result mainly of improvements in X-ray technique, and of the consequent possibility of
a more exact correlation between the radiographic, pathological
and clinical signs presented in a large series of cases. A liberalisation
of the standard of selection of this nature, however, only effects
a material increase in the number of cases detected when it is
being applied for the first time, and when, accordingly, two grades
of the disease are being taken out at once. Once it has been
applied all round to the whole body of working miners, the temporary
increase disappears.
As the result of this investigation it was, therefore, possible to
predict that this temporary increase, at least, would shortly
disappear, and that the rise which it had occasioned would be
succeeded by a fall. And the fall occurred in due course. In
1926-1927 the incidence of silicosis dropped back to 2.7 per cent.
But the further drop which has since occurred to a figure of
1.76 per cent, in 1928-1929 is even more satisfactory. It represents
a genuine improvement because it has been effected in the face of
a continued increase in the number of older miners at work.
When one makes allowance for the influence of that increase,
one is able to state with entire confidence that the true production
of silicosis, when measured (as it can only be truly measured) by
the respective attack-rates for the disease amongst the miners at work
in each corresponding respective year of underground service, shows
a decided improvement upon the condition which obtained six years
ago, before the intervening rise occurred.
The most striking evidence of improvement is seen in the returns
for the specially selected body of men who have entered the industry
since 1916, and whom we have termed the " new Rand miners ".
These men now number over 8,300 and are increasing year by year.
Now whereas in the period from 1920 to 1923 the attack rate for
silicosis amongst all miners who were working in their tenth
year of service was 5 per cent., amongst the "new Rand miners"

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working in their tenth year of service in 1928-1929 it was only
1.3 per cent. Part of this effect is certainly due to the better
stamp of man of which the " new Rand miners " are composed.
But if we allow an equal share to that factor this result is still
remarkable. One cannot indeed anticipate that rates of this
low order will continue when the " new Rand miners " enter the
later periods of service, but there is no reason to suppose that they
will even then reach the relatively high figures which the older
miners have hitherto shown.
The duration of underground service amongst those miners
who became silicotic during the past year was over twelve years.
Of the 270 cases detected during that year, 90 per cent, had begun
work prior to August 1916—prior, that is, to the beginning of the
" present-day " period. One must remember, as we have said,
that the cases of silicosis which arise in any one year are the
cumulative result of the conditions obtaining during the previous
ten or twelve years.
All of this is reassuring. But one must add a definite word of
caution. Although we have turned a big corner in the matter of
silicosis, one does not anticipate that the actual number of cases
detected will show any significant further decrease in the immediate
future. For, although the " new Rand miners " with their
relatively lower attack rates are becoming more numerous and the
alder miners fewer, nevertheless, the older miners who remain,
and there are still well over 5,000 of them, are every year getting
still older in years of service, and therefore more liable to contract
silicosis. The one factor will probably for some time balance the
other, and, as a consequence one does not anticipate much, if any,
actual decrease in the number of cases which will arise for a good
many years to come.

SOME OUTSTANDING PROBLEMS

Reference may be made here to the recent strong move on the
Witwatersrand towards reconsideration of the methods of
combating miners' phthisis underground. The principal line which
those concerned in that movement have taken has been to urge that
" wet " methods of dust allaying should be replaced where possible
by " dry " methods, and that, where " wet " methods are still
found necessary, the amount of water used should be as small as
possible. Two main factors have encouraged the movement. On

WITWATERSRAND: HISTORY OF SILICOSIS

207

the one hand, there has been growing realisation of the discomfort,
inefficiency, and even danger to life from heat stroke, arising from
high temperatures combined with high humidities in deep and
insufficiently ventilated mines. On the other, a strong medical
opinion, in which the two medical joint authors of this paper share,
has established itself to the effect that the rapidity with which many
of our cases of " simple " silicosis pass to the " infective " type is in
part connected with the increased facility of infection induced by
the dampness and high humidity underground- There are,
however, many problems to be solved before practical effect can
be given to such a policy. While the comparative ineffectiveness
of water in sprays or on wetted surfaces in removing from the air
those very fine particles of dust, under 5 microns in diameter, with
which we are concerned, is now well known, and was demonstrated
in the case of the water blast, formerly looked upon as very effective,
by the Witwatersrand Joint Committee on the Ventilation of
Development Ends in 1923, it remains to be shown that ventilation
can be increased or other means found to enable the sprays or wet
surfaces to be wholly or partially given up without detriment. It
has also to be shown that methods can be found which will in
practice allow reduction in the very effective results of the use of
water in checking the rise of fine dust from holes being drilled or
from broken rock or ore being shovelled.
Another point which has to be considered is whether or not,
when all that is possible has been done in cutting out the use of
water for dust allaying, the amount of water naturally percolating
into the mine shafts and working places or inevitably used for dust
allaying will not still be sufficient to give high relative humidity in
the mine air. It has to be remembered that less than 20 gallons
of water will give a relative humidity of over 90 per cent, to 100,000
cubic feet of air at 87° Fahr.
Another type of preventive measure calls for consideration. It
has been noticed for many years that in certain industries wherein
silicosis production might be expected the disease has either been
absent or of very low prevalence and has occurred very late in the
working life of the employees. It has been suggested that this
happy state of affairs may be related to the presence in the air,
together with silica, of some particles that serve as an antidote.
This hypothesis is particularly associated with the name of Dr. John
Scott Haldane, and he called the attention of the Witwatersrand
to its possibilities in 1918 and again in 1929. It is desirable to
locate these industries and to secure data as to the actual amount of

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dust of silica to which their employees are exposed and to confirm
the reputed absence of silicosis by examinations of employees and
some method of " follow-up " similar to t h a t obtaining on these
fields.
The whole matter is bristling with fascinating problems for both
the scientific investigator and the practical engineer.
CONCLUSION

In conclusion a word may be said about the possibilities of future
developments on these fields.
It would appear that although the life of a number of the existing
mines is limited there are others whose production is likely to continue
for twenty and more years, and in addition there are further areas of
virgin ground which presumably will give rise to the opening up of
new mines. It is, therefore, evident that the fight against miners'
phthisis is likely to continue for many years to come unless a satisfactory
solution to our present problems can be found. Judging by our experience of the past, it is practically certain that our mining methods
will also undergo considerable changes in the future. The tendency
exists throughout the Witwatersrand mines to adopt mechanical means
for handling and transport of the broken rock and it is conceivable that
this fact may have become an important factor in the prevention of
miners' phthisis if, with the advance of engineering methods, a large
proportion of the manual labour can be eliminated and thereby human
exposure to phthisis-producing dust can be lessened.

AETIOLOGY OF SILICOSIS (DUST-PHTHISIS)
BY

A. MAVROGORDATO,
FELLOW

INDUSTRIAL

M.A. (OXON), M.R.C.S. ( E N G . ) , L.R.C.P. (LOND.),
HYGIENE,

SOUTH

AFRICAN

INSTITUTE

MEDICAL RESEARCH

While thanking the Conference for the honour done me, I
remember t h a t I am before an audience many of whom have
travelled some six thousand miles to' be present and are intimately
acquainted with the subject. This is not the occasion to approach
the matter in the spirit of a post-graduate lecturer.
The lungs are used to inhaling dust and used to getting rid of it,
and one may perhaps recognise exposure to four main types of
dust :
(1) Dust that is harmless.
(2) Dust that is usually harmless but may contribute to the mischief
when inhaled in association with a harmful dust.
(3) Dust that is usually harmless and may have actual prophylactic
value when inhaled in association with a harmful dust.
(4) Dust that is harmful.
When dealing with silicosis one is not concerned with dusts that
are harmful by virtue of being irritant; such dusts make their
mischief after a different fashion. Our concern is with what is
now pretty generally known as "phthisis-producing dust". For a
dust to be phthisis-producing it must possess certain qualities
some of which may be enumerated as follows: it must be capable
of overcoming the lung's physiological ability to rid itself of dust
and of getting itself arrested, and of getting itself so arrested for a
considerable time. As dust particles do not multiply of themselves,
it must be relatively indestructible by tissues and tissue-juices.
Since the initial means of arrest is by phagocytosis, it must be
of a size to lend itself to this process; t h a t is to say, it must be
about the size of the common pathogenic micro-organisms.
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It must be too inert to bring about the ready destruction of the
cells that take it up, and too inert to provoke a free production of
the cells that take it up or to provoke the production of any
considerable exudation. Dusts that when inhaled provoke a moist
condition of the lungs associated with expectoration are not readily
retained for long by normal lungs.
Dusts that lend themselves to arrest and the production of a
dust-phthisis do not readily destroy the cells that take them up,
and the laden cells tend to aggregate into what Koch called pseudotubercles. Here, then, is one means of arrest. A suspension of
such dust injected intra-venously will be retained among other
situations in the lungs, and will there set up a similar reaction to
that which it sets up when inhaled. It is the exception for injected
suspensions of particulate matter to behave in this fashion, and
the procedure affords one means of testing the phthisis-producing
qualities of a dust. Pseudo-tubercle production is another feature.
For some years I have been interested in the fact that in tolerably
pigmented lungs one may find areas clear to the naked eye, but
surrounding an intensely black spot several millimetres across:
much larger than the ordinary pseudo-tubercle. I have examined
many of these spots in microscopic preparations, and usually they
are aggregates of dust-laden cells surrounding a minute lymphoid
nodule. I saw two such cases recently with Dr. Sutherland
Strachan, and he tells me that he attaches considerable importance
to the part played by such nodules in the arrest and distribution
of dust. As to why these nodules should hold up some dusts
rather than others is a further point. I am disposed to relate it
to the prolonged preservation of the dust-laden cells, and attribute
this preservation to the dust being slightly soluble. The pseudotubercle formation also suggests a chemical factor entailing a
measure of solubility. There is a vires acquirit eundo quality
about a dust-phthisis, and one suspects certain dusts of possessing
the property of provoking an allergic response in the tissues which
implies the need for their being to some degree soluble.
The dust that possesses these qualities and dominates the dustphthisis of industry is dust of free silica, Si0 2 .
Clinical dust-phthisis is a protean disease and, as with other
diseases, in considering its aetiology one must consider together the
agent, the subject, and the conditions of exposure.
Let us start with the agent. You cannot have tuberculosis
without the tubercle bacillus, and you cannot have a dust-phthisis
without a phthisis-producing dust. So far so good; but the dust

AETIOLOGY OF SILICOSIS

211

or agent may be " pure " or " adulterated ". In practice the agent
is always more or less adulterated and, nowadays, the adulterant
interests us perhaps more than the primary agent. The adulterant
may be inanimate, that is to say other dust, or animate, that is to
say micro-organisms. When I first came in real contact with the
subject of dust-phthisis it was as assistant to Dr. J. S. Haldane, and
I found my chief's, attention particularly focussed on this question
of the inanimate adulterant. This was getting on for twenty
years ago, but in a fox-hunt Dr. Haldane would be found in front
of the fox. The question was this: why, given the presence of a
phthisis-producing dust, did those exposed seem on occasions to
escape the disease, and why did the disease vary so widely both in
incidence and severity ? Obvious considerations such as intensity
and duration of exposure did not cover all the facts. Colliers, for
instance, might be exposed to phthisis-producing dust when drifting
and shaft-sinking, yet they were held to be particularly fortunate
in avoiding respiratory diseases in general and dust-phthisis in
particular. In certain American mining districts the miners ought
to have been suffering from the disease, but, as far as the evidence
went, they were not doing so. It was possible that Si0 2 might vary
in its nature or that certain other dusts when inhaled with Si0 2
might serve as an antidote. As Sir William Garforth used to say,
where you find nettles there you find docks. It was on such an
hypothesis that experiments were performed comparing the
influence on animals of exposure to dust of free silica alone and to an
equal dose of dust of free silica but with coal dust added 1 . Different
series of these experiments were performed over many years, some
in Dr. Haldane's private laboratory at Oxford, some at St. Thomas's
Hospital in London, and some at the South African Institute
for Medical Research, Johannesburg.
The results may be
summarised by stating that coal inhaled simultaneously with
silica did help silica out of the lung, but that previous invasion
by coal did not appreciably hinder the settlement of silica, nor did
a subsequent invasion of coal bring out settled silica. Coal dust
is not the only dust that has this property; Professor E. L. Collis
has pointed out that, in the manufacture of fire-bricks, the
presence or absence of certain " clays " seems to decide the
prevalence or absence of silicosis among the workers, although
the exposure to silica dust is practically the same in amount and
1
Journal of Hygiene, Vol. X V I I , 1918, p. 439. Publications of South African
Institute for Medical Research, No. XV, 1922, p. 15, and No. X I X , 1926, p . 19.

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under similar conditions in each case. Of late years instances of
this kind have accumulated; I shall confine myself to mentioning
one of them.
By the courtesy of Dr. L. P. Stokes, in response to an enquiry,
Dr. Orenstein was informed that on the Kolar Gold Field they had
met with only one case of silicosis in a European who had not
worked in a phthisis-producing industry elsewhere: this man had
worked underground for thirty-eight years. Dr. Stokes adds:
" We have not found primary fibrosis in any Indian cases. "
Pulmonary tuberculosis is increasing throughout India, and a latent
tubercle infection is frequently made active by underground work.
Systematical medical examination of European employees,
including an X-ray examination, is the rule on the Kolar Gold Field,
so one may assume that silicosis is not arising. The mines are
quartz mines, but until one knows the total silica and free silica in
their rock one must beware of attaching too much importance to
freedom from silicosis on this field.
Just as the presence of certain dusts seems to interfere with the
ability of silica dust to settle in the lungs, so too the effective
occupation of the lungs by silica dust seems to interfere with the
ability of the lungs to rid themselves of dusts that do not settle
in normal lungs. Does a phthisis-producing dust set up an
allergic state ? The analyses of the dust-content of the lungs of
those who have died with a dust-phthisis always show the presence
of dusts other than the incriminated dust, while in the case of
our own sufferers the lungs are often as black as a collier's, even
though the subject gave up mining years before his death. I have
shown that, in our subjects, the " black " or pigment is mostly
carbon from the soot provided by the acetylene lamps used underground1. In experimental animals that have received heavy doses
of silica dust by inhalation and then been left to live out their
lives where they were exposed to smoke, then carbon is to be found
in the silica-stricken areas of their lungs, though not elsewhere.
I do not believe for a moment that this carbon did any harm, but
I do suggest that, in the presence of a dust known to be phthisisproducing, all dust should be regarded as potentially harmful
unless known to be helpful. In this context one may refer to the
collections of coal dust to be found in the lungs of old colliers who
have worked for many years at " hard-headings ".
The question of the inanimate adulterant can be left here with
1

Publications of South African Institute for Medical Research, No. XV, p. 54.

AETIOLOGY OF SILICOSIS

213

the comment that it suggests two lines of research ; one of them very
important. In the case of industries not associated with a serious
incidence of dust-phthisis, although exposure to phthisis-producing
dust appears adequate for its production, then the specific antidote
must be sought in case it is present, perhaps in small quantities,
as an inanimate adulterant. In the case of phthisis-producing
industries associated with an incidence of simple dust-phthisis
beyond that which experience would lead one to expect, one
must beware an inanimate adulterant in addition to other
possibilities.
Let us turn to animate adulterants or micro-organisms. The
distinction between " simple " and " infective " silicosis or dustphthisis in a phthisis-producing industry is as important as the
distinction " clean " and " dirty " cases in surgery. In this
disease disability and death are always associated with a greater
or lesser degree of the infective element, but in some industries
and in districts with a high prevalence of dust-phthisis the disease
persists for a long time in the clinically simple stage and progresses
but slowly, while in other districts and industries the infective
factor comes into evidence early, and often with the result that many
cases show rapid progression even after the subject has given up a
phthisis-producing occupation. Unfortunately, on the Witwatersrand we are confronted by the type of the disease in which the
infective factor is of great importance. (See accompanying graphs
by the Miners' Phthisis Medical Bureau, Johannesburg, 1920
and 1922, pages 214 and 215.)
Ante-primary silicosis is regarded by us as the earliest stage at
which we can recognise a dust-phthisis as a specific clinical entity.
Our miners' phthisis compensation is not based directly on the
principles of accident compensation, consequently we do not
require a subject to be disabled before being compensated. The
data on which the graphs are based are taken from the Annual
Reports of the Miners' Phthisis Medical Bureau. After six years
only 156 survived as ante-primary silicosis, while 107 were dead—in
the great majority of cases, of tubérculo-silicosis. The remaining
survivors have progressed beyond the ante-primary stage, although
nearly all of them gave up underground work on these mines when
they were notified as suffering from the disease. With us, as
elsewhere, the tubercle bacillus is the dominant infective factor in
disability and death related to dust-phthisis. Dust-phthisis has
always been with us on these fields, but a change in clinical type has
been observed as the years go by.

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895
of S.

1922

TO T H E

782

719

647

599

Of S.

of S.

537
of S.

CONFERENCE

466

409

348

289

Of S.

Of S

After
After
After
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After
12 mths. 2'tmlhs. 36 mths. 48 mths 60 mths. 72 mths. 84 mths. 96 mths. 108 mths.

IOO

473 of
A-P S

373 Of
A-P S

324 of
A-P S

193 of
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156 Of
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112 Of
A-P S

215

AETIOLOGY OF SILICOSIS

o/.
'
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1st
year

2nd
year

3rd
year

4th
year

^>v.

5th
year

6th
year

7th
year

8th
year

9th
year

20
IO

No. 3. — Taken from Nos. 1 and 2. The progression curves of " Primary
Silicosis (A) and " Ante-Primary Silicosis (B) compared. There is no gain in
ability to arrest the disease.

%
4.0

1st
year

2nd
year

3rd
year

4th
year

5th
year

6th
year

7th
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30
20

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No. 4. — Death curves of " Primary Silicosis " (A) compared with " AntePrimary Silicosis " (B). There is a gain in expectation of life for ante-primary
cases.

216

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In the earlier days the dust was the dominant factor and the
outstanding features were dyspnoea with cardiac-failure, dropsy,
and oedema of gravity distribution. The disease, while much more
prevalent, was running a different course. For many years past
the disabled cases have been much more like an ordinary chronic
tuberculosis, and the infective factor has been dominant. Some
years ago the Medical Bureau introduced the term " silico-tuberculosis " to distinguish cases in which the infective factor was
dominant from the cases of tuberculo-silicosis in which the dust
factor was dominant. My colleagues, Drs. A. Sutherland Strachan
and F. W. Simson, both of whom have had a wide post-mortem
room experience of dust-phthisis, urge me to insist on the fact that
the distinction between tuberculo-silicosis and silico-tuberculosis is
clinical and not pathological. They point out that the lesion of
tuberculo-silicosis is a specific pathological lesion and is neither
the lesion of tuberculosis nor the lesion of silicosis. It is the same
now as in hundred-year-old museum specimens. They add that
there is no such thing as the specific lesion of silico-tuberculosis.
With these contentions I of course agree; but one does not drop
a term or classification that is useful clinically solely on the grounds
that it does not fit in with pathological categories, nor have clinical
terms always been introduced with an aftercoming pathologist
in mind : one may perhaps add that a dust-phthisis does not start
in the post-mortem room.
It might also be argued that what Dr. W. Watkins Pitchford has
called the " gross characters of the silicotic lung " may differ in the
two types of case. The " old " lungs were typically bulky; emphysema was present, but was far from being solely responsible for the
bulk. The lungs, apart from the characteristic lesions of tuberculosilicosis, rather suggested a pigmented fibroid phthisis, but they
were twice the size they ought to be. The present lungs are not
typically bulky, while emphysema plays a larger part in their bulk
than it did in the old lungs, which did not collapse when removed
from the body but stood up like plaster casts. I have discussed
this question with Dr. Louis Irvine, the present Chairman of the
Medical Bureau, and we both agree that, since the term " tuberculosilicosis " fits both the clinical and pathological categories, it is
misleading to bring into literature a term such as silico-tuberculosis
that fits the clinical categories only. It is for this reason that
Dr. Irvine himself has never liked this term.
The association between tuberculosis and dust-phthisis is proverbial, but the variation in the part played by tuberculosis is

AETIOLOGY OF SILICOSIS

217

almost equally proverbial. It is misleading to deduce the " silicosis
rate " of an industry from its tuberculosis rate, even if one counts
tubérculo-silicosis as tuberculosis. In many phthisis-producing
industries tuberculosis does not become an important factor till
well into the sixth decade of the worker's life and after getting on
for thirty years of employment, yet a systematic examination of
employees will disclose plenty of simple silicosis. An instance of
such a state of affairs has been splendidly reported by Drs. E. R.
Hayhurst, D.T. Kindel, B. E. Nyswander, and C. D. Barrett in the
Journal of Industrial Hygiene, Vol. XI, 1929, p. 228. These
observers point out that they were dealing with an open quarry,
but, after all, silicosis was first systematically studied and its
association with tuberculosis first satisfactorily defined in the case
of workers in open quarries 1.
It is not difficult to recognise factors in a dust-phthisis which
predispose to infection of lungs, but it is very difficult to see why
identifiable factors should operate so differently.
1 have been impressed by the following observations made
chiefly on native miners. While dust of Si0 2 possesses the ability
to settle permanently in the hostile territory of the lungs, this
ability is only relative. In the case of a native who has worked
many underground contracts on these fields and has died immediately on his return from his kraal, it is surprising how little pigment
there may be in the lungs. If a native who has worked many underground contracts dies of pneumonia immediately on his return
from his kraal the pulmonary alveoli will be found to be swarming
with pigment-laden and silica-laden cells. These cells will have
been loaded up months before and yet have remained sufficiently
handy, sufficiently free and sufficiently well preserved to be poured
into the alveoli. I incline to think that these cells have remained
in the fluid but stagnant lymph of obstructed lymphatics, and that
lymph persists for a long time fluid but stagnant in a distended
obstructed lymphatic. The history is the same as that of a
thrombosis: ultimately organisation occurs in each case. If
invading pathogenic organisms be met by stale humoral and
cellular elements, their survival would be facilitated. To borrow
a term Professor Lyle Cummins has used in connection with
tuberculosis, the effective occupation of an area of lung by a
phthisis-producing dust sets up a " dead area " in the sense that
this area is out of the free circulation.
1

Trans.

Med.

Chirurg.

Soc. of Edinburgh,

Vol. I, 1824, p. 373.

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One more feature may be adduced to illustrate the interference
in normal lymph circulation that follows on effective occupation
of the lungs by a phthisis-producing dust. Dr. Harvey Pirie
and I have been much impressed by the promptness and ease
with which inhaled dust gets past the lungs to be held up elsewhere.
We have described what we call the silicotic or tuberculo-silicotic
zone, and this zone includes glands in the portal fissure and glands
round the stomach and pancreas as well as glands above the
diaphragm other than the trachaeo-bronchial groups. The
phenomena described—retention in the lung, mobility in the lung,
and interference with the normal flow of lymph—are all such as
should favour infection, but why do not they function more
uniformly ?
Before leaving the subject of phthisis-producing dust and its
adulterants, I would emphasise my belief that intermittent
employment is the most effective single measure against a
phthisis-producing dust making a dust-phthisis. The simple
silicosis rate is comparatively low in our native miners, most of
whom are employed intermittently, and I relate this low rate
to the fact that even a phthisis-producing dust before being finally
fixed remains for some time under conditions that enable some
of it to get out of the lung in favourable circumstances. Such
favourable circumstances are intervals between periods of underground work of sufficient length to enable elimination to retard
accumulation.
In this context the following feature may be recalled. Greenfield,
later on Ziegler, and in recent times Collis and others, have called
attention to the fact that although a dust-phthisis is a " dry "
disease and a disease of the terminal portion of the bronchial
tree, the small bronchioles are involved in the trouble and shed
their epithelium. Intervals from exposure to a phthisis-producing
dust affords this section of the lung's eliminating apparatus an
opportunity for regaining lost efficiency.
To turn from the agent to the subject. To begin with, the
initial examination of recruits to the mining industry that has been
our practice since 1916 has amply justified the selection of men
with good general physique and unimpaired respiratory apparatus.
With exposure to a phthisis-producing dust, as in other circumstances, it is a case of one is taken and the other left. Workers
differ greatly both in the ability to get rid of dust and in their
ability to resist tuberculous and other super-imposed infections.
While writing this paper I have seen the lungs of two miners,

AETIOLOGY OF SILICOSIS

219

•one native and one European. Each had worked sixteen years
underground and on machines; neither had a clinical silicosis.
In both cases there was comparatively little pigmentation of lungs,
and the native did not present the slightest suggestion of macroscopic
silicotic lesions while in the European such macroscopic lesions
as were recognisable were confined to the roots of the lungs.
The part played by the tuberculous factor varies from one
phthisis-producing district to another. With us the tuberculous
factor is perhaps the most serious aspect of the problem: so many
of our men, although they give up mining, pass rather rapidly
from silicosis without disability to silicosis with disability, and so
on to tubérculo-silicosis. Some observers relate this phenomenon
in part to difference in physical type and compare the short stocky
Cornishman and his long-drawn-out simple silicosis with the tall
lanky South African and his rapid development of the infective
clinical type of the disease. I would also associate this difference
in behaviour with the fact that the industrialisation of pastoral
and agricultural districts is always associated with an initial rise
in their tuberculosis rate. This initial rise is followed by a fall.
The Western areas of the United States of America and Japan
are modern instances. At present over 70 per cent, of our European
underground complement are South African born, but this class
only took up mining in considerable numbers since 1907. Before
1907 our European underground complement was drawn almost
entirely from overseas. Other things being equal, the members
of an underground complement with traditional spontaneous
discipline will look after themselves better than those of a complement with no mining tradition.
The third factor for consideration in dealing with the causation and
progression of silicosis or dust-phthisis is the conditions of work. The
important part played by intensity and duration of exposure, and,
in my opinion, by continuity of exposure, may be taken for granted.
I am going to refer to conditions related to methods adopted for
reducing intensity of exposure to dust and infection. At about
the same time British and South African authorities were attempting
to deal with risks due to dust underground. With the British
it was coal dust and colliery explosions; with us it was silica dust
and silicosis. Each party was confronted with the original choice
between wet and dry methods. The British adopted dry methods
and rendered coal dust non-explosive by mixing it with inert dust
in preference to by wetting it. They were, of course, alive to the
risk of introducing a phthisis-producing dust. Fifteen years'

220

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experience has shown t h a t the method adopted has put a stop to
colliery explosions without raising the respiratory diseases rate of
employees. It is quite possible that systematic examination
of colliers will disclose silicosis or dust-phthisis without disability,
but the method has justified itself.
South Africa chose wet methods. Circumstances alter cases
and, on the Rand, we have neither colliery lay-out nor colliery
ventilation as the given manoeuvre ground. Up to a point the
method adopted has been a success; the amount of air-borne dust
has been greatly diminished and the incidence of silicosis has fallen.
The reduction of dust by watering cannot, however, have all the
credit for the fall in silicosis incidence; one must remember the
important part played by improvement in ventilation and by
selection of employees (" initial examination ").
When one considers conditions of exposure as a factor in the
causation of dust-phthisis, one remembers that this disease may arise
in open quarries, workshops or mines. The peculiarity of conditions
on the Witwatersrand lies in the following combination of factors:
Men are working at a high temperature with a high relative humidity.
Nearly all underground employees, both European and native, are
drawn from a population occupied until recently with agricultural and
pastoral pursuits.
The working population is, comparatively speaking, highly tuberculised.
At any one time there will be rather over 9,000 Europeans and rather
over 150,000 natives at work underground. The annual tuberculosis
incidence on native miners is about 700 per 100,000 per annum.
Opportunity for contact with tuberculosis is greater than usual.
Is this peculiarity in conditions associated with any peculiarity
in the disease ? One may say t h a t the incidence rate of simple
silicosis is not unduly high, but two points call for mention.
In the case of those affected, the mean duration of exposure
before the disease is detected is about twelve years.
A large proportion of the cases pass on to the infective progressive
type of the disease not long after the condition has been recognised
in its simple form.
Granting that one takes on an occupation with an occupation
hazard, there is a vast difference between risking disablement
early in the fifth decade and risking disablement late in the sixth
decade. When one remembers that but few South-African-born
Europeans start underground work before they are twenty-five
years of age, the fact that a serious proportion of those who contract
silicosis are disabled in the first half of their fifth decade is the
salient feature of silicosis on the Witwatersrand. The mean

AETIOLOGY OF SILICOSIS

221

duration of exposure before the disease is detected is on the short
side, and the comparatively brief accumulation period cannot be
accounted for by intensity of exposure. It must be born in mind
that the majority of the cases that progress have given up .underground work. One is driven to the conclusions that in considering
conditions of exposure as a factor in the aetiology of silicosis one
must consider them under two heads:
(a) As a factor in simple silicosis.
(b) As a factor in infective silicosis.
1 will dismiss simple silicosis without further reference and turn
to the infective type of the disease. Granted that tuberculosis is,
and always has been, the dominant infective factor in silicosis or
dust-phthisis, one must accept the fact that the underground
workers on the Witwatersrand present a favourable soil for the
implantation of this disease. I am not satisfied that this is the
whole story. When workers are not exposed to high temperatures
associated with a high relative humidity, the disease does not
behave as it behaves on the Witwatersrand. Reference has been
made to the Kolar Mine Field. There one has a population susceptible to tuberculosis working at a high temperature but at very low
humidity: there is no evidence of a high silicosis rate, still less of a
high infective silicosis rate. Certainly the fine ventilation of the
Kolar mine must be considered in assaying their favourable
position in respect to silicosis; but I cannot help thinking that the
adoption of wet methods of dust control means the giving of too
much consideration to simple silicosis and too little to the more
formidable infective type of the disease.
In 1918, and again in 1929, Dr. J. S. Haldane called the attention
of the Witwatersrand to the price that had to be paid for keeping
down dust in a mine by water. As far as the recognised methods
of estimation of dust can tell us, our workers are not exposed to
higher concentrations than are workers elsewhere. Water has not
failed in this respect. The fact remains that the disease with us is
made rather more quickly and in a more vicious form than is the
rule elsewhere. I cannot think that our experience on the
Witwatersrand will encourage others to add a high relative
humidity to other conditions of exposure to a phthisis-producing
dust if they can possibly avoid doing so. As has been pointed out
in another communication to this Conference 1 , our selection of wet
1
" Historical Review of Mining Conditions on the Witwatersrand ".
p. 107.

222

PAPERS PRESENTED TO THE CONFERENCE

methods of dust control was largely dictated by our circumstances.
Our damnosa haereditas did and does prevent us from realising
colliery or Kolar ventilation conditions. What is left ? Dr.
Haldane urges us to seek the " inanimate antidote ".
Remembering my audience, I have discussed the aetiology
of silicosis or dust-phthisis in terms of mining in quartz; the^
condition of which I have first-hand experience. Members from.
overseas are far better qualified to discuss other aspects than I
am myself. There is good reason to believe t h a t colloidal silica isas dangerous as, if not more dangerous than, crystalline silicaExperience in the manufacture of certain abrasive powders suggeststhat certain colloids favour the production of silicosis when present
in the air with Si0 2 . The investigators at the Amherst Quarries,
Ohio, suggest that certain colloids hinder the production of silicosisand particularly of tubérculo-silicosis when present in the air with
Si0 2 . Since the war, attention has been directed to asbestos as a
cause of dust-phthisis. If South Africa is to become a centre of
diamond cutting and polishing it may have another dust-malady in
which to be concerned.
To summarise: when dealing with the aetiology of silicosis or
dust-phthisis :
(A) One considers intensity, duration and continuity of exposure to>
phthisis-producing dust.
(B) One remembers that the association of adulterants animate and
inanimate may influence both the production of the disease and its type.
(C) One fears that a high humidity favours infection by prolonging
the life of pathologic organisms outside the body and facilitating their
entrance into the body.
(D) One asserts that infection in a phthisis-producing industry
should be thought of as it is thought of in a surgical ward or operating:
theatre.
(E) One feels that if a pastoral or industrial population is to turn
to industry, they should think twice before turning to a phthisis-producing;
industry.

A PRELIMINARY STUDY
OF THE PATHOLOGY OF SILICOSIS AS SEEN
ON THE WITWATERSRAND
BY

A. SUTHERLAND STRACHAN,
F. W. SIMSON, M.B., CH. B.

M.A., B . S C , M.D. (GLASGOW),

(EDIN.), PATHOLOGISTS AT THE

AND

SOUTH

AFRICAN INSTITUTE FOR MEDICAL RESEARCH, JOHANNESBURG

In this study, an anatomical basis of silicosis is outlined.
The development of silicotic lesions, both uncomplicated and complicated by infection is described.
The macroscopic features are detailed and the complications indicated.
A small series of experiments on the relationship between tuberculous
infection and silicosis is incorporated and a tentative conclusion
arrived at.
ANATOMY

In the routine examination of a large series of lungs for silicosi»
and tuberculosis our attention was early drawn to the occurrence
of pigmentation in the pleura, in the interstitial tissue and
apparently in the lung parenchyma, and an explanation was sought
for this phenomenon. The explanation was found to lie in the
distribution of the lymphatics and of lymphoid tissue in the lung.
For this reason it appears to us that a review of the anatomy of the
lung with particular emphasis on the lymphatic apparatus is an
essential preliminary to the study of the pathology of silicosis.
For our purpose it is sufficient if we consider the bronchi, lungs
and pleurae.
The intra-pulmonary bronchi divide and subdivide throughout
the lung and terminate in the lobular bronchioles. The bronchi and
bronchioles are lined by ciliated epithelium. The bronchiole is
succeeded by a slightly dilated portion known as the vestibule,,
in which the epithelium alters to a flattened type. The vestibule
divides into several passages from three to six in number—the
atria; these open out into two or more somewhat elongated passages
—the infundibula, from which arise the alveoli or air-cells.

224

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The lung parenchyma consists of lobules, which, though quite
distinct from one another, are intimately bound together by
connective tissue, the interlobular septa.
A terminal bronchiole with its subsequent divisions and air-cells
and with the associated blood-vessels, lymphatics and nerves,
forms the lobule.
Both lungs are covered by a thin transparent serous membrane
which encloses the organ except at the root.
Beneath this membrane is a delicate connective tissue in which
are to be found elastic fibres, blood-vessels, nerves and lymphatics;
the subserous connective tissue is continuous with the trabeculae
of the lung parenchyma.
In our experience early pigmentation occurs in certain definite
sites in the lungs and pleurae ; these sites are in the lymph-glands,
in the sub-pleural tissue, in the interlobular septa and in the
parenchyma in relationship to the terminal bronchioles, to the
vestibules and to the atria.
The lymph-glands into which drain the lymphatics of the lung
may be divided into four groups :
(a)
(b)
(c)
(d)

Broncho-pulmonary.
Superior tracheo-bronchial.
Inferior tracheo-bronchial.
Paratracheal.

The broncho-pulmonary glands lie in sites between a lobe of
the lung and its bronchus.
The superior tracheo-bronchial group lies in the upper angle
between the trachea and the main bronchus.
The inferior tracheo-bronchial group lies in the lower angle
formed by the main bronchi at the bifurcation of the trachea.
The paratrachial group lies along the trachea in relation to the
inferior laryngeal nerve.
The lymphatics of the lung are divided into two groups, superficial and deep.
The superficial forms a wide-meshed net-work in the subpleural
connective tissue over the whole surface of the lung. From this
net-work channels pass to the broncho-pulmonary glands at the
root of the lung. Oppel 1 states t h a t in addition to these channels,
many small lymphatics pass from the superficial vessels by way
of the interlobular septa to join the deep vessels arising around
bronchi and blood vessels.
1

OPPEL:

Lehrbuch

der vergi. Mikr.

Anat. der Wirbeltiere,

1905, p . 746.

WITWATERSRAND : PATHOLOGY OF SILICOSIS

225

Scott and Beattie x remark t h a t : " t h e superficial plexus is
almost independent of the deep except at two points " b u t they
do not mention where the points of communication are.
Miller 2 states:
In the human lung there are connective tissue septa much more
largely developed than those about the primary lobules, which separate
the secondary lobules from each other. In these septa blood and lymph
vessels are associated with each other and where they join the pleural
vessels 3 there is always found a mass of lymphoid tissue.
Our observations have led us to the conclusion that communications between deep and superficial lymphatics must exist in order
t o account for the distribution of pigment in the interlobular septa
and in the pleura. This distribution, in our opinion, is mainly in
relationship to the perivenous lymphatics. The transport of
pigment for any distance in the lung parenchyma is intra-cellular
•and b y way of lymphatics and for this reason the early pigmentation
of pleura implies communication between deep and superficial
lymphatics.
The deep lymphatic vessels take origin in relationship to the
¿ranches of the bronchi and of the blood-vessels and terminate in
the tracheo-bronchial glands.
According to W. S. Miller, lymphatics cannot be demonstrated
in the branches of the bronchi beyond the terminal bronchiole
•except they be in relationship to the artery or vein.
In the larger bronchi the lymphatics form two plexuses—an
inner sub-mucosal, and an outer peribronchial beyond the cartilages;
as the branches of the bronchi become smaller the peribronchial
plexus gradually disappears and only the sub-mucosal persists.
The pulmonary artery follows the bronchus in all of its subdivisions, dividing as it subdivides; each has its own system of
lymph vessels and these are in communication at the places where
the bronchus divides and at the distal end of the vestibule.
The pulmonary veins have also a system of lymph vessels which,
like the arterial, are in communication with the bronchial system
where the bronchus divides and also at the distal end of the vestibule
where the bronchial system begins.
In the primary lobule of the lung, the bronchiole and the artery
lie in the centre while the veins occur mainly in the periphery, only
t h e venous radicles from the vestibule form veins within the lobule.
1
2

SCOTT and BEATTIE: Jour. Path, and Bac, Jan. 1928, Vol. XXXI, p. 54.
MILLER: Anat. .Ree, 1911, Vol. V, p. 99.

The italics are ours.
15

226

PAPERS PRESENTED TO THE

CONFERENCE

As yet no lymphatics have been demonstrated in the walls of
the alveoli. It is our opinion that lymphatics do not exist in this
situation.
The examination of sections of carcinoma of the lung showing
extensive lymphatic permeation revealed no involvement of the
alveolar walls (vide fig. I 1 ). Further, the absence of pigment in the
alveolar walls in early cases of pigmentation without alveolar
fibrosis is, in our opinion, in favour of the view that lymphatics
do not exist in this situation.
In association with and intimately related to the lymphatics
of the lung, there occur aggregations of lymphoid tissue, which may
be in the form of simple aggregations, follicles or nodes.
This tissue is found in sites sub-pleural, peribronchial, periarterial
and perivenous.
In the sub-pleural region the lymphoid tissue occurs as simple
aggregations irregularly distributed, but showing very often at the
points of junction of interlobular septa with sub-pleural connective
tissue.
Lymph nodes and follicles are found on the larger bronchi
where branching takes place; in the smaller bronchioles lymphoid
aggregations, not follicles, are seen outside the muscular coat,
lying between the bronchiole and the artery.
Lymphoid aggregations occur along the artery and then usually
lie between the artery and the atria, not between the bronchus
and the artery as in bronchial lymphoid tissue.
The perivenous lymphoid tissue is found commonly where a
small vein joins one of the main trunks of the pulmonary vein;
consequently these aggregations are frequently best seen in the
interlobular connective tissue septa.
In this outline of lymphoid tissue of the lung we have followed
W. S. Miller's 2 description, which corresponds in the major details
with the description given by Oppel 2 and which is accepted and
confirmed by Scott and Beattie 2 in their recent work on tuberculosis
in primates.
We are able also to confirm the observation made by Miller a
that in miliary tuberculosis the tubercles appear where he has
described the normal occurrence of lymphoid aggregations.
Further, it is in these situations that the arrest of pigment
akes place in the earliest stages of the development of silicosis.
1
2

The illustrations (figs. 1-14) are given after p . 248.
Op. cit.

WITWATERSRAND:

PATHOLOGY

SILICOSIS

227

As regards the epithelium lining the air vesicles the literature
has been discussed in full by Cappell1, and we agree that the
lining consists mainly of nucleated squames and the lipoid-containing
" septal cells ".
Cappell2 states that the alveolar phagocytes are derived from
these two types of cell, and that some time after separation from
the alveolar wall they become indistinguishable from one another.
A feature of importance in these cells is the presence of lipoid
granules in the protoplasm.

THE DEVELOPMENT OF SIMPLE SILICOSIS

We have emphasised the importance of the lymphatic apparatus
in the development of silicotic lesions, but before proceeding
with the discussion of the development, it may be worth while
recapitulating the main features of the defensive mechanism,
which acts in the prevention and limitation of the invasion of the
lung by dust.
In the nose and nasopharynx the anatomical structure provides
a very efficient dust filter for the inspired air ; the dust that escapes
arrest may settle on the mucous menbrane of the trachea and
bronchi, whence by the action of the ciliated epithelium it is
driven upwards and is removed in the sputum. Thus the air
which reaches the alveoli, for all practical purposes, may be
considered dust free.
Several factors may play a part in breaking down the defensive
mechanism; of these, infection-producing disquamationof the epithelium of the upper air passages is an important one, while a great increase in the dust content of the inspired air may be another. In an
atmosphere loaded with particulate matter, the filtering mechanism
of the nose and nasopharynx is overcome, the lining epithelium
of the upper air tubes becomes clogged and the air entering the
alveoli contains relatively large amounts of dust. In our cases
of silicosis both factors mentioned play a part, but the dominant
one appears to be the great increase in the inspired air of respirable
particulate matter. The greater part of the dust which finally
reaches the alveoli, according to most authorities, is of a size
comparable with that of pathogenic bacteria.
1
1

CAPPELL: Jour. Path, and Bac, July 1929, Vol. XXXII, p. 697.
Op. cit..

228

PAPERS PRESENTED TO THE CONFERENCE

In the reaction to the invasion of the alveoli by dust, phagocytosis is the essential feature and this is associated with proliferation of the lining epithelial cells, which become detached
from the walls to form the alveolar phagocytes.
In the conditions under which miners work on the Rand, there
is in the air, in addition to siliceous particles, a considerable
quantity of finely particulate carbon; both are found associated
in the development of silicotic lesions. The alveolar phagocytes
or " dust cells " become pigmented by the carbon particles (pigmentation may occasionally be seen in cells still in situ on the
alveolar walls) and the silicotic lesions also show a similar pigmentation. This pigmentation is of considerable help in tracing the
development of the lesions as the siliceous particles are frequently
so small that even investigation by polarised light is unsatisfactory.
At this stage it is worth while recalling the fact that not all dust
which reaches the alveoli is retained within the lung parenchyma.
Some of the cells which contain it reach the lumen of the bronchi
and are removed in the sputum. The alveolar " dust cells " tend
to accumulate in the small air passages—atria, vestibules and
smaller bronchioles, and from there they pass into the tissues of the
walls to the lymphatics. In our investigations we have not been
able to demonstrate dust cells in the alveolar walls except in cases
where there is a generalised fibrosis, probably of infective origin.
We have, however, constantly noticed their accumulation in the
small air passages, apparently just prior to their entrance into the
lymphatic system. The first sign of the arrest of " dust cells "
occurs at very definite sites in the lymphatic system—-where
lymphoid tissue has been described as occurring in the normal
lung. In the earliest stage of the process the first places of arrest
appear to be in lymphoid tissue about atria, vestibules and terminal
bronchioles as the lumen of one or more of these structures can
usually be seen in close relationship to the aggregations of "dust
cells " (vide fig. 2). In our experience the true silicotic formation
does not occur as a rule in relation to the larger bronchi. That the
perivenous lymphatics are also involved in the process is obvious
from the fact that the periphery of the lobule becomes delimited
by deposits of pigmented cells and that interlobular septa and
pleura also show the cell aggregates. With the exception of
the subpleural connective tissue, however, true silicotic nodule
formation is rarely seen in these situations.
An interesting and important feature noted in the bronchiole
related to the pigmented cell aggregates in the peribronchial

WITWATERSRAND : PATHOLOGY OF SILICOSIS

229

lymphatics, is the occurrence of desquamation of the ciliated
epithelium {vide fig. 3). This " dry " bronchiolitis is a constant
feature and may be an important determining factor in the lung
invasion. It is also worthy of consideration from another point of
view ; the radiological examination of miners has revealed a condition which is, in the majority of cases, definitely presilicotic, and
which is associated with a characteristic picture known as " fine
ramifying fibrosis ". This shows an appreciable increase in the
extent of the shadows originating at the hilus of the lung and
spreading fanwise into the lung substance. In the normal lung
these shadows show the same distribution as the larger bronchi and
possibly blood-vessels, but in radiographs showing increase the
definition of the main trunks is better, and in addition shadows are
seen extending almost to the periphery. The picture has previously
been explained by postulating a diffuse fibrosis occurring in
peribronchial and perivascular tissues associated with a mantling
of bronchi and vessels with dust cells. In our experience the
mantling of these structures with dust cells is not a constant
feature even in moderately advanced cases of silicosis. It seems
to us that some other explanation is required and for this reason the
problem is being investigated. For the present, however, we would
lay emphasis on the occurrence of the dry bronchiolitis which
manifests itself before actual microscopic silicotic foci can be
demonstrated.
The effect of arrest of the pigment-laden phagocytes has been
described to be associated with a reaction which increases the
lymphoid tissue. This increase has been noted by many observers,
and by some, follicle formation with adenoid reticulum has been
described. Lymphoid follicles in relationship to the smaller air
passages were described as normal by Klein x, though W. S. Miller 2
maintains that follicle formation in these sites does not occur apart
from pathological changes. This increase may occur in the sites
at which the pigmented cells of silicotic lesions are arrested. In
the majority of cases we have not been able to demonstrate the
increase in lymphoid tissue as it is almost certain to be obscured
by the preponderance of pigmented cells. The further reactive
phenomena seen in the early silicotic lesion becomes comparable
with those which take place in a lymph gland, which is the seat of
invasion by dust cells.
1
3

K L E I N : Quoted by Miller: Anal. Ree,
Op. cit.

1911.

230

PAPERS PRESENTED TO THE CONFERENCE

In the early pigmented mass, in suitable preparations, an
occasional cell is seen t o contain fatty material in addition t o
pigment. The fatty material may be an original element in t h e
cell, as phagocytes derived from septal cells usually contain fatty
material, or it may be a manifestation of degenerative changes
taking place prior to disintegration of the cell. This appearance
of fat in the earliest cell aggregations is, in our opinion, of considerable importance, for fat is present in all stages of the development
of the true silicotic nodule. In the fully developed silicotic focus
the fat is mainly extracellular, and this we take as presumptive
evidence that the dust cells die and disintegrate. In addition to
this, we have noted calcification of symmetrical character in some
of these foci (vide fig. 4).
The silicotic nodule develops in the pigmented cell aggregate and
appears as a small ball of well-formed fibrous tissue ; only when this
change takes place is the term silicotic nodule used.
On disintegration the phagocytes set free the irritant dust,
which provides the stimulus for the reactive fibroblastic phenomena
of silicosis. The cells taking part in the reaction are probably
derived from the adventitial tissues of bronchiole and blood-vessel.
If follicle formation occurs, as has been described, part of the
fibroblastic reaction may be derived from the reticulum. Herring
and MacNaughton 1 in their investigations of the lymphatic system
in relation to the removal of particulate matter from the lymph
stream summarise their conclusions as follows:
The phagocytic cells are arrested in the first lymph gland in the
lymph stream. The cells carrying solid particles pass from the lymph
sinuses of the gland into the lymphoid tissue of the cortex and medulla
and eventually discharge their burden among the lymphocytes there.
The lymph gland is an extremely efficient filter and only allows
solid particles to pass through it when these arrive in too great numbers
at a time, or when the gland has become disorganised.
The lymphocytes of the lymphoid tissue act as a mechanical barrier
against the particles and eventually the barrier is made more complete by
the appearance in it of fibroblasts and the formation of fibrous tissue.
The foreign material is firmly enclosed, while the lymph sinuses are
left open for the free passage of lymph.
The efficient filtering action of t h e lymph gland demonstrated
by Herring and MacNaughton 2 probably also applies to t h e
lymphoid tissue in the lung. The phagocytes are arrested and
the pigment incarcerated while t h e lymph channels remain clear.
1

HERRING and MACNAUGHTON: The Lancet, 3 June 1922, p. 1081.

Op. cit.

WITWATERSRAND: PATHOLOGY OF SILICOSIS

231

As the first lymph gland in the stream is first involved and then
the next in the series, so in the lymphoid tissue in the lung, viz.
the aggregations in relation to atria, vestibules and bronchioles
are first to show the reaction.
The lymphoid hyperplasia, which, as Herring and MacNaughton x
conclude, acts as a mechanical barrier to the onward passage of
the dust-laden phagocytes is followed by a fibroblastic reaction
and a fibrosis.
The Development of the Silicotic Nodule in Lung Substance
In the aggregation of pigmented cells a small focus of fibroblasts
appears (vide fig. 5). It may be oval or circular in shape and may
occur in the centre of the aggregation or quite eccentrically; the
site of its appearance is quite fortuitous but once initiated the
succeeding changes proceed from this centre of origin (vide fig. 6).
In some cases, the reaction appears almost of a granulation tissue
type (vide fig. 7), but in the majority of cases there is little new
formation of blood vessels. The earliest microscopic nodule is a
very minute cellular fibroblastic accumulation of cells, arranged
irregularly, some cells radially, some at the periphery arranged
tangentially, and surrounded by pigmented dust cells and lymphocytes. The fibroblasts show little if any pigmentation. It would
appear that the greater part of the carbon pigment is removed
from the site in which the fibrosis is developing while siliceous
particles are retained. This is a feature which can be demonstrated
from the minute cellular focus to the well formed nodule.
The cellular character persists for a period during which the
focus is enlarging, but soon collagen fibres are laid down and a ball
of well formed fibrous tissue appears, which is surrounded by
zones of fibroblasts, dust laden pigmented cells and lymphocytes.
The fibrous tissue is arranged in a whorl-like manner in the central
portion while at the periphery the appearance is that of concentric
lamination. The increase in size of the nodule is always at the
periphery by concentric lamination (vide fig. 8).
There are two striking features in the well-formed silicotic
nodule—the absence, in the majority of cases, of appreciable
quantities of carbon pigment and the presence of fat. With regard
to the absence of pigment the nodule from the lungs of the Rand
miner differs from specimens of British material which we have
examined.
1

Op. cit.

232

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As to the fat, this makes itself manifest as soon as fibrosis takes
place and increases in amount with the advance of the fibrosis.
We have noticed that frozen sections show appearances suggestive
of changes preliminary to calcification; the haematoxylin stain
shows an alteration in the colour reaction of the material varying
from the normal, through varying tints of violet right up to the
intense bluish black of calcification. The tissue apparently contains.
a substance, which is readily soluble in the reagents used for the
preparation of ordinary paraffin sections, for these show alterations
of the staining reaction only when calcification is complete.
Presumably some soap soluble in the reagents is a stage in the
calcifying process, and this soap when brought into contact with
the haematoxylin stain in frozen sections gives the modifications
which we have noted.
Our opinion is, therefore, that in a considerable number of
instances, changes just preliminary to calcification may be present
in silicotic foci though not demonstrable by the ordinary paraffin
section methods. In the advanced silicotic islet, calcification may
occur and usually is in the centre and appears to be a condition quite
apart from infection (vide fig. 4). A further noteworthy point in
regard to the silicotic nodule is that, in some sections, the aggregation of dust cells appears to be surrounding pulmonary blood
vessels and air tubes, and this suggests the possibility of subsequent
fibrosis bringing about obliteration of the lumen. In our investigations the appearance of the fibrosis and its development do not
suggest that obliteration occurs to any great extent in simple
silicosis; the fully formed fibrous tissue islet appears to displace
structures rather than to surround them.
The islets of fibrosis increase in size by a laminated type of
growth at the periphery until ultimately they are readily detectable
by the naked eye and are easily palpable. Though microscopically
the fibrous tissue may show little or no pigmentation, the zone of
arrested phagocytes at the periphery imparts a definite black
colour to the naked eye appearance. The contrast between macroscopic and microscopic appearances is thus very striking.
As the condition of simple silicosis progresses, the nodules not
only increase in size but also in number, so that there may be
nodules in various stages of development in one lung, but they
are all of the type described above.
We have mentioned that in the earliest stages the aggregates
of dust cells occur in relationships to bronchioles, vestibules and
atria. A silicotic focus may arise in one or more of these sites. If

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they arise simultaneously, in their growth they may become
contiguous and then confluent, producing a " composite nodule ".
This is seen macroscopically and palpated as a single nodule
(vide fig. 9).
It has been stated that the nodular fibrosis produces an appearance which has been likened to a " string with beads on it ". In
our opinion the simile is not quite accurate. The arrangement is
rather that of a staphyloid type; each element consisting of a
silicotic nodule, single or composite, situated at the entrance to
a lobule.
In some macroscopic specimens of simple silicosis there are seen
massive areas of fibrosis, which superficially resemble similar areas
to be described in infective silicosis. Close examination may
reveal a nodular basis for the massive areas. Microscopic sections
show numerous contiguous single and composite silicotic nodules
between which there still survive some of the lung structures,
e.g. bronchi, blood vessels and alveoli. In this type of lesion
collapse of lung tissue occurs which may be the result of narrowing
of the lumen of bronchus or bronchiole or more probably the result
of displacement of tissue by the great number of nodules (videfig.10).
Changes in the Pleura
While the changes, which have been described, are taking place
in the lung substance, similar changes occur in the subpleural tissue.
These in the order in which they occur are — arrest of dust cells in
aggregations, fibroblastic reaction and finally fibrosis with the formation of an islet surrounded by pigmented cells and lymphocytes.
The process is modified, however, as soon as the islet reaches the
surface. In the subpleural tissue it is entirely surrounded by
pigmented cells, but when the fibrous tissue in its growth reaches
the serous membrane, the pigmented cells become displaced,
leaving that portion which projects on the surface free from these
pigmented cells (vide fig. 11). In some of the older subpleural
nodules the endothelial cells of the pleura have disappeared, and
at that point the fibrosis is of a denser character and greater in
amount. This suggests that the change is partly induced by
friction of the opposing pleural surfaces. The macroscopic appearance of the silicotic islet from the pleural aspect is that of a small
pearly white, slightly raised area and is then known as the " subpleural plaque ". In the morbid anatomy of silicosis the subpleural
plaque is a feature of some importance, and we emphasise here

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that it is simply a nodule of silicotic fibrosis originating in subpleural tissue. It only involves the pleural membrane secondarily,
in the course of its increase in size. Its site is probably determined,
as in the lung, by the presence of lymphoid tissue; its development
by the invasion of this tissue by dust cells.
Changes in Lymph Glands
Dust cells from lung and pleura are transported to the tracheobronchial and "broncho-pulmonary glands respectively, and are
arrested there. When the lung is invaded by dust, some of the
phagocytes escape arrest in the lung foci and are carried by way of
the lymphatics to the root of the lung. Probably only a few cells
escape at a time from the region of each pigmented focus, but the
sum of these cells from all foci is large. There is thus a relatively
massive concentration of dust cells in the lymph glands. This
concentration explains why gross pigmentation occurs in the root
glands while lung and pleura still show relatively small amounts.
The pigmented cells pass from the afferent lymphatics into the
sinuses and from there to the cords and nodes in the cortex and
medulla of the gland. The dust cells die and disintegrate, set free
the irritant particles which give rise, first, to lymphoid hyperplasia,
then a fibroblastic reaction and finally a localised fibrosis. The
nodule at this stage is similar in type to those seen in the lung or
pleura. In some cases a dense hyaline change is seen presenting
features which superficially resemble amyloid tissue, but sections
of this material suitably stained give a negative result. The nodules
occur in multiple sites in gland tissue, and there arise numbers of
single islets which may coalesce to form composite islets, or in a
further stage areas of massive fibrosis. This brings about destruction of the normal gland elements. Even when replaced by massive
fibrosis, dilated lymph channels may be seen at the periphery.
In a proportion of cases calcification occurs without obvious signs
of tuberculous infection. The changes we have observed in dustoccupied gland tissue are in agreement with the conclusions of
Herring and MacNaughton 1 on the arrest of particulate matter
in lymph glands.
The similarity between the changes seen in lymph glands to
those which occur in lung substance and pleura is a further point
in support of the view that the silicotic foci begin in lymphoid
tissue in the lung substance.
1

Op. cit.

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Gye and Kettle 1 show that local inoculation of silica into subcutaneous tissues produces a definite and characteristic reaction,
but this reaction differs from that seen in lymph glands and in the
lung tissue.
We can find no evidence that silica produces the lesion of silicosis
in tissues other than lung and lymph glands.
INFECTIVE SILICOSIS

The lesions we have just described are, in our opinion, due almost
entirely to the effect of inhaled dust. We have now to consider
what modifications arise when infection is associated with silicosis.
Some of these modifications present definite features to which the
term " infective silicosis " has been applied. Amongst infections
the one that really matters is tuberculosis, though we have to
admit that others may play a part both in the spread of the fibrotic
process and in modifying its characteristic features. To what
extent infection, apart from tuberculosis, is responsible for the
changes in infective silicosis has not yet been determined, but the
question is being investigated.
There are two main aspects of the relationship between infection
and dust. In the former dust modifies infective processes; in the
latter superimposed infection modifies the reactive processes
produced by the presence of irritant dust.
In the lungs of miners who have worked underground in a dusty
atmosphere, silica particles may be present in considerable numbers
without producing macroscopic or microscopic silicotic nodules.
The local tissue resistance of such a lung is so lowered that relatively
small doses of a pathogenic organism may produce infection.
Further, Mavrogordato 2 has shown, in experimentally dusted
animals, that an unresolved pneumonia occurs in a proportion of
cases when the animals are subsequently exposed to infection by
organisms other than the tubercle bacillus. This may explain the
relatively frequent occurrence of unresolved pneumonia in native
miners, whose lungs show little or no evidence of silicosis. These
manifestations are not included in the group " infective silicosis ",
though they may be due to the modifications of the infective
process by dust.
1

G Y E and K E T T L E : Brit. Jour. Exp. Path., 1922, Vol. I l l , p . 245.
MAVROGORDATO: Publications of the South African Institute for Medical
Research, 1926, Vol. I l l , No. 19, p . 32.
2

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Superimposed infection modifying the reactive processes produced
by irritant dust is best seen in tubérculo-silicosis. Other organisms
may play an important part in these changes, but up to the present
it has not been determined to what degree.
The term " infective silicosis " should be confined to conditions
in which infection produces changes in the reactions to dust.
As the tubercle bacillus is by far the most important organism
which modifies silicosis, we shall confine our discussion to its effects.
Tuberculosis is essentially a disease of the lymphatic system,
and when tubercle bacilli settle in the lungs they do so in lymphatic
tissue. Miliary tubercles we have noted in sites in which lymphoid
tissue has been described as normal; the same sites in which
aggregate the pigment laden phagocytes which initiate the changes
of silicosis. It is possible then, that the two reactive processes may
occur simultaneously in relationship to one site. In such circumstances an islet of fibrosis of some size is produced relatively rapidly,
but the fibrosis differs somewhat from the ball of well-formed,
dense fibrous tissue of " simple silicosis ". In the centre of the islet
the definition of the elements is lost, and appearances suggestive
of central necrosis are seen, while at the periphery granulation tissue
is more abundant. The typical tuberculous reaction, however, is
absent. There is no follicle formation; no obvious aggregation of
endotheloid cells and no giant cell formation (vide fig. 12). An
islet may thus be the result of the combined process, and may be
termed a tuberculo-silicotic islet; in this the tuberculous process
is masked to a great extent.
In other cases the naked-eye appearances of an islet of similar
size may suggest tuberculosis round the periphery, and this is
confirmed microscopically. In this case infection had evidently
occurred after the silicotic process had been well established.
It is difficult to estimate the relative incidence of the two types
of tubérculo-silicosis.
The records of the Miners' Phthisis Medical Bureau show that a
considerable proportion of miners, diagnosed as simple silicosis
progress to the condition of tubérculo-silicosis. If they live long
enough they die of tuberculosis, even if they have been removed
from the working conditions in which the silicosis was set up. Of
the cases diagnosed as simple silicosis on radiological and clinical
grounds, some correspond with those, which are seen post-mortem
to show the macroscopic features of simple silicosis and yet have
the microscopic stigmata of tuberculosis with silicosis. These are
cases of tubérculo-silicosis even though diapnosed in the first

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instance as simple silicosis. The progress of the condition is slow,
and although silicosis predisposes to tuberculous infection, it also
has a limiting or inhibitory effect on the infection, as though the
bacilli were incarcerated in the reactive fibrosis, or that the virulence
of the organism was altered by the presence of silica. In other
cases of simple silicosis, there is no tuberculous infection in the
beginning, but this becomes superimposed later and tubérculosilicosis is again produced. The terminal result is similar and it
is this similarity which renders difficult the determination of the
relative incidence of the two types.
The progress of the fibrosis in infective silicosis differs somewhat
from that of simple silicosis. In simple silicosis we have shown
that composite islets arise in relationship to the bronchioles, and
that relatively large areas of fibrosis arise as a result of apparent
confluence of contiguous islets in an area heavily affected by the
silicotic process. What interstitial change does occur is almost
certainly related to infection. A clean silicotic lung—admittedly
a rarity—shows little change in the lung parenchyma beyond the
silicotic foci and the changes in the air tubes.
In tubérculo-silicosis, however, we have a condition where increase
of fibrosis occurs by direct extension. Lymphatics, interstitial
tissue and alveoli may all be involved in this manner; although the
lesion may be initiated as discrete islets, in time a diffuse fibrosis is
set up. A considerable number of nodules may have been embedded
in this tissue, but with the advent of necrosis and increasing generalised fibrosis their distinguishing characters are lost.
An area of diffuse fibrosis, generally designated " massive ",
shows considerable pigmentation with carbon, irregular foci of
necrosis and frequently some caseation. Giant cell systems and
tubercle follicles are exceedingly rare. In frozen sections, fat
may be demonstrated in considerable quantity.
Massive areas of fibrosis apparently arise in several ways.
In simple silicosis where numerous single and composite islets
become contiguous the appearance simulates massive fibrosis.
Although called massive, close inspection shows that it is composed
of definite islets of fibrosis still retaining their distinctive nodular
character (vide fig. 10).
A second mode of development arises in infective silicosis. In
this too a nodular character may still be seen as the distinctive
feature of the massive area, but unlike the simple type there is
evidence of coalescence and minute foci of caseation may occur
(vide fig. 13).

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These two types may resemble one another macro scopically,
in that each presents a greyish black coloration and has a nodular
character. The points whereby they may be distinguished are
evidence of coalescence of the nodules, distinct foci of caseation,
and the colour is more grey in the infective type.
A third type of massive fibrosis is seen in which there is no evidence
of nodular character. In this there is an ill-defined, diffuse necrosis.
The colour is again grey from the combination of pigment, fat
and necrosis (vide fig. 14). There may also be present areas of
unpigmented necrosis. This is a manifestation of infection probably
always tuberculous in origin. It is produced by the coalescence
of numerous tubérculo-silicotic foci with subsequent breaking
down of the tissue to form one mass. Often at the margin of such
an area it is possible to distinguish the outline of some nodular foci.
Though tuberculosis may produce the modification which is
known as tubérculo-silicosis, some cases in which silicosis is present
show obvious local tuberculous foci. Sometimes they are unmodified
and sometimes associated with an area of pigmented fibrosis.
The condition may remain localised or there may be an acute
terminal spread; silicotic lesions and tuberculous lesions occurring
without one modifying the other.
Endarteritis obliterans has been described by some authorities
as an essential factor of silicosis, but we have been unable to
convince ourselves that this is so. In tubérculo-silicosis vessels
may be obliterated in the progressive, massive interstitial fibrosis.
MACROSCOPIC APPEARANCE OF THE SILICOTIC LUNG

When a miner dies and an autopsy is performed, the lungs are
removed and sent to the Miners' Phthisis Medical Bureau for
examination. This examination is essentially a macroscopic one;
only in certain cases where confirmation is required is a microscopical
investigation made. It is thus seen that from the practical
administrative aspect, the macroscopic features of silicotic lesions
are of considerable importance.
A minute silicotic focus in the lung in the earliest stages is not
palpable, though the small pigmented islet may be visible; only
on microscopic examination can fibrosis be detected. As the focus
enlarges a stage is reached when it becomes palpable. On section
of the lungs it projects slightly above the cut surface. The small
palpable islet is the first macroscopic manifestation of silicosis
in the lung substance.

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It is obvious that, from the administrative point of view, the
occurrence of an occasional small palpable islet cannot be held
to constitute the disease silicosis. Certain degrees of the condition
have therefore been determined which have been found to correspond
with arbitrary stages in its progress, and with definite estimated
degrees of disability. These degrees of silicosis are known under
the terms, " slight ", " moderated ", " well-marked ", and " verywell-marked ". They indicate to the Bureau the relative number
and size of the macroscopic lesions present in the lung substance.
Thus in slight silicosis the lesions may be small and moderately
numerous, or medium-sized to large and sparse; in the moderate
degree the lesions may be numerous and small, or moderately
numerous and large; in the well-marked degree, the lesions are
numerous and large; while in the very well-marked degree they are
very numerous and large.
In appreciating the degree present the whole lung substance has
to be considered, for it is found that in a proportion of cases the
lesions may be very limited in site, so that though they may be
numerous and large where they occur, the greater part of the lung
substance may be free from silicotic manifestations.
The terms small, medium-sized and large are used for islets of
diameters up to 2 millimetres for the small, varying from 2 to
4 millimetres for the medium and from 5 millimetres to a centimetre
for the large.
It is difficult to give a precise meaning to the words sparse,,
moderately numerous and numerous, as such a meaning could apply
only in cases where the lesions were diffuse and more or less symmetrical throughout the whole lung substance. On the cut surface
of the lungs in early cases of silicosis, the diffuse symmetrical
distribution occurs in a minority of cases. More frequently the
lesions are localised to restricted areas, where they may be
moderately numerous or even numerous, but if the same number
were spread over the whole lung symmetrically, they would be
considered sparse. Less often a similar distribution may be met
with in moderate and well-marked degrees.
Standards have been elaborated for the assessment of degrees of
silicosis, where the islets are more or less symmetrical in distribution.
According to them, the word " sparse " is used when the distribution of the palpable islets on the cut surface of the lung is of the
order of one silicotic islet in each square whose side is 5 centimetres
in length; moderately numerous when the square has a side of
3 centimetres in length; numerous when the square has a side of

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2 centimetres in length and very numerous when the square has
a side of less than 2 centimetres in length.
From our definitions it is seen that the varying degrees of silicosis
are not sharply defined, but merge gradually into one another.
Similar criteria are adopted for tuberculo-silicotic lesions.
Silicotic lesions, on the Rand, are pigmented and show up black,
but not all pigmentation is silicotic. The presence of silicosis is
determined not by pigmentation, but by the appreciation of a
definite amount of palpable fibrosis in the lung substance.
In presilicotic conditions, there is accumulation and concentration
of pigment in the root glands, but in them occur the first signs of
fibrosis. At first the glands are slightly enlarged, slightly firm to
the touch and pigmented by carbon. The pleura shows a definite
increase in pigment, which tends to outline the periphery of the
subjacent lobules, and the lung substance shows pigmentation in the
form of discrete non-palpable islets.
As silicosis develops the glands are definitely enlarged, pigmented
and firm to the touch. The subpleural pigmentation increases in
amount and there is incipient plaque formation. The subpleural
nodules have probably just reached the serous membrane and are
seen as fine pin-point pearly white foci, surrounded by a ring of
pigment. They are palpable but scarcely project above the
surface. The serous membrane is still smooth and glistening.
Sometimes there are patchy areas of pleural opacity, which are
probably associated with infection. In the lung substance, sparse
small islets of pigmentation become palpable. On section the lungs
show moderately numerous discrete islets only a few of which are
palpable. All islets are black in colour whether palpable or not.
With further advance of the disease, there is progressive fibrosis
in the lymph glands, small subpleural plaques are formed, and the
palpable islets in the lung parenchyma increase in size and in number
so that a stage is reached when the lung section shows moderately
numerous discrete islets of pigmentation, the majority of which are
palpable and project above the cut surface of the lung. A slight
amount of marginal emphysema may be noted and chronic
bronchitis is present.
In the well-marked and very well-marked degrees of silicosis,
the lungs may not be much increased in size, but show an increase
in weight. Emphysema, particularly in the marginal regions and at
the apex, is present as a more or less constant feature. There is
also a chronic bronchitis with thickening of the walls of the larger
bronchi. The root glands are enlarged, sometimes excessively so.

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The pleura shows plaque formation to a marked degree, particularly
at the apices and along the posterior borders of the lungs. The
interlobar pleura is rarely affected. Opacities, patchy thickening
and adhesions are usually present, though they are not purely
silicotic in origin, but are the result of infection. The lungs on
section show moderately numerous or numerous large palpable islets,
black in colour but often with a greyish tinge in the centre. Massive
areas of fibrosis may be present, in which, even on macroscopic
examination, the individual islets may be recognised. The massive
fibrosis is generally a little less dense in colour; the colour being
rather a greyish black than pure black. In some cases, plaque
formation has been noted on the diaphragmatic pleura, while in a
relatively large number there is fibrosis of silicotic character in the
gland groups in the posterior mediastinum, at the cardiac end of
the stomach and in the upper part of the abdomen. In the case
of the latter, they are found particularly around the pancreas and
in the portal glands at the hilus of the liver. This extension is more
commonly seen in tubérculo-silicosis, and we explain it as mainly
retrograde spread along lymphatic channels, which communicate
between the lung root glands, posterior mediastinal glands and the
diaphragm; or more directly by way of the mediastinal pleura.
The macroscopic detection of tubérculo-silicosis in the early
stages is attended with great difficulty. The islet is usually large,
grey in colour and shows evidence of rapid growth or enlargement,
though none of these factors is essentially characteristic of superimposed tuberculous infection. The large amount of fat contained
in the islet is sufficient to explain the change in colour. The
occurrence of numerous islets restricted to the sites of election for
tuberculous infection may suggest that the lesions are tuberculosilicotic. Probably such lesions are of infective type, but the
paucity of suitable material for biological tests leaves the question
still open.
In a well-marked case of tubérculo-silicosis, the root glands are
grossly enlarged, of steel grey colour, sometimes with foci of caseation, sometimes of calcification. There are dense adhesions on the
pleura with much scarring and patchy thickening associated with
local emphysema. Plaque formation may be a prominent feature.
Section of the lung shows numerous large grey islets, some with
points of caseation. In localised parts numerous islets become
confluent forming massive areas of fibrosis, a frequent site for which
is just under the pleura, and towards the upper parts of the lobes
of the lungs. These areas may show foci of caseation, evidence of
16

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breaking down and even actual cavity formation. Chronic
bronchitis with great thickening of the bronchi is present. In a
number of these cases there is no evidence of overt tuberculosis, but
a proportion do show active tuberculosis with cavity formation
and broncho-pneumonia.
DISTRIBUTION OF LESIONS

The first lesion associated with silicosis appears in the root
glands; next pleural involvement is seen, and cases may show
plaque formation with enlarged glands with little evidence of the
disease in,the lung substance. In early cases the site of the lesions
of the lung shows great variation. They may appear more or less
symmetrically throughout both lungs or they may be more numerous
towards the apices and in the posterior parts of the lungs. Occasionally they are localised in small areas; the localisation being most
frequently seen at the apices.
In more advanced cases the nodules tend to be more symmetrically distributed. In some well-marked cases with numerous islets,
the islets near the pleura are small, while those near the root are
large and in the intermediate zone they are of medium size. This is
not a constant feature, but is seen sufficiently frequently to be
worthy of note.
COMPLICATIONS

The most important complication of silicosis is tuberculosis«
If a silicotic patient does not die of some other disease or by accident,
he will ultimately die of tuberculosis. Tuberculosis may appear
early and give rise to tubérculo-silicosis, or may occur relatively
late and produce obvious lesions of overt tuberculosis associated
with excavation and tuberculous broncho-pneumonia. Sometimes
the manifestation is a terminal miliary tuberculosis originating in a
focus in some other organ. With tuberculosis there may be a
chronic tuberculous pleurisy, showing a greatly thickened and adherent pleura. The lungs may be firmly anchored, particularly at the
apices and this may play a part in the development of yet another
complication—bronchiectasis.
There is bronchitis of a chronic type in all cases of well marked
silicosis. The walls of the bronchi are much thickened and in some
cases there is a diffuse dilatation giving rise to a fusiform type of

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bronchiectasis; occasionally a saccular bronchiectasis is seen,
usually associated with chronic pleurisy. The evidence of bronchiectasis is sufficient to be noteworthy, but it is much less than might
be expected in view of the constant bronchitis and chronic pleurisy.
Associated with the chronic bronchitis in silicosis or tubérculosilicosis, there is gross emphysema. Large bullae are frequently
seen along the margins and in the apical regions. We have met
with one case of pneumothorax, due to rupture of a large bulla in
a tuberculo-silicotic lung.
In certain cases when pneumonia affects a silicotic lung there may
be non-resolution and organisation. This is seen in both lobar
and broncho-pneumonia. In other cases, particularly in natives,
gangrene is not an uncommon event.
Odema and congestion are frequently seen, but these are usually
explained as terminal phenomena.
One other complication in the lung substance remains to be
discussed — the incidence of primary carcinoma and its association
with silicosis. We have met with seven cases of carcinoma in a
series of European miners, all being carcinomata of bronchi. In a
series of autopsies on Europeans carried out by us at the General
Hospital, Johannesburg, only two cases of carcinoma of the lung
have been observed. The number of cases is too small to permit
of any accurate assessment of the place of silicosis as an etiological
factor in carcinoma of the lung, but the possibility must be kept
in view.
Changes associated with silicosis and tubérculo-silicosis may
occur in organs apart from the lungs; particularly is this so with
tubérculo-silicosis. In the glandular advance of tubérculo-silicosis
we have seen the " cavai " gland of the heart to be the seat of
tubérculo-silicosis and the pericardium the seat of tuberculosis.
As described by Shore a , the cavai gland is intrapericardial and
drains into the lower tracheo-bronchial group. If the cavai gland
is involved in tubérculo-silicosis or tuberculosis it must be so by
retrograde spread. The site of this gland and its relation to the
tracheo-bronchial group may explain one mode of spread of tuberculosis from the lung to the pericardium.
As regards the heart itself, it is often stated that silicosis produces
changes in the heart associated with hypertrophy. We have not
been able to demonstrate this. Even in cases of gross fibrosis
and emphysema, there has been little alteration in the weight of
1

SHORE:

Jour. Anal., April 1929, No. 63, p. 291.

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the heart and little evidence of hypertrophy. When the cause of
death is cardiac failure, emphysema and interstitial fibrosis are
sufficient, as a rule, to account for the cardiac disability. Disease
of the coronary vessels may also aggravate the condition.
Disease of the blood vessels is common on the Rand. It usually
takes the form of atheroma and is not infrequently associated with
calcification. This change may appear early in life. We have
noted atheroma with calcification in cases as young as twenty-one
years, and in females as well as males. Vascular disease is common
amongst miners on the Rand, but does not appear to be more so
than in members of the general population.
We have noted chronic nephritis in a proportion of cases, but
in how far this is caused by vascular disease or by the silicotic
process it is difficult to determine. Our impression, which is yet
to be confirmed, is that the incidence of chronic nephritis is no
greater in miners than in members of the general population.
With regard to the liver, we have not noted any preponderance
of cirrhotic changes in silicotics. A few have shown haemochromatosis, but haemochromatosis is relatively common in both Europeans
and natives in Johannesburg.
Apart from complicating tuberculosis of the lungs and mediastinum
tuberculosis may be seen in other parts of the body. Normally it
would appear that silicosis tends to localise the tuberculosis, but we
have seen numbers of cases, in which there is evidence of metastatic
foci occurring in other organs. At autopsy, such a case may show
grossly enlarged tuberculo-silicotic root glands, extensive genitourinary tuberculosis and a terminal miliary tuberculosis. This
type of case is more commonly seen in natives but it also occurs
in a small proportion of white miners. Similarly in cases where
there is no evidence of overt tuberculosis in the lungs or root
glands there may be tuberculomata in the brain and tuberculous
meningitis.
EXPERIMENTAL INVESTIGATION OF TUBERCULOUS INFECTION
IN SILICOSIS WITHOUT OVERT TUBERCULOSIS

As some authorities have suggested and maintained that silicosis
is infected by tuberculosis in its earliest stages, it seemed advisable
that the problem should be investigated from this point of view.
Not every lung sent for examination is suitable for this type
of investigation. The specimens are rendered useless as a result

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of delay in transit and consequent putrefaction, or having been
placed in fixative. Even in autopsies performed by ourselves
many of the lungs showed post-mortem changes which rendered
them useless for biological tests. Further, in a considerable
number of cases the lungs were the seat of necrotic and caseous
lesions, in which the tubercle bacillus was readily identified by
ordinary bacteriological methods. These factors explain why so
small a number of cases have been submitted to biological tests
over a comparatively long period.
The material originally selected was from early cases of silicosis
in which there was no suspicion of tuberculosis. The material
for inoculation was selected from root glands, subpleural nodules
and nodules from the substance of the lungs. Subsequently tissue
was obtained from more advanced cases where tubérculo-silicosis
was suspected. In one case only (J.R.B.) was there any sign
of overt tuberculosis, but even in this case tissue was carefully
selected from portions of the lung showing no active tuberculosis.
The silicotic lung, as is well known, is a " dirty " lung, but the
tissues used for the tests were taken as aseptically as was possible
in the circumstances. In the experiments the tissue was ground
up both with and without the aid of sterile sand, in a minimal
quantity of sterile saline. When thoroughly ground an emulsion
was made in about 4 cc. of sterile saline and the whole inoculated
into the left groin of a guinea-pig.
A few of the guinea-pigs died of septicaemia, but the majority
lived sufficiently long for evidence of tuberculosis to develop.
An abstract made from the protocols of the various experiments
is given in table I.
The experiments up to the present are few in number but are
being continued when suitable material is made available.
From the few results recorded it is impossible to express any
dogmatic opinion, but it is permissible to suggest certain conclusions.
The terms in the table, silicotic nodule, lung, small or large
and black, indicate respectively: the material used, the site from
which taken, size and colour and presumed absence of infection.
The site also applies to root glands and tuberculo-silicotic area
—and grey indicates presumed presence of infection but does not
necessarily imply it.
With the black silicotic nodule, the results have been uniformly
negative.
In the cases labelled tuberculo-silicotic as a result of nakedeye examination, a large percentage of positive results have been

to
TABLE

Case

Degree of
silicosis

Guineapig.

Date
inoculated

Material inoculated

Date of
deatn

Cause of
death

Result

>
J.M.McD

Very occasional islet

l.A
l.B

2 0 . 5.27
20. 5.27

Silicotic nodules, lung. Small, black
Silicotic nodules, lung. Small, black

30. 5.27
25.11.27

Enteritis
Killed

Negative
Negative

A.J.R,

Very occasional islet

3.«
3.*

15. 6.27
15. 6.27

Silicotic nodules, lung. Small, black
Silicotic nodules, lung. Small, black

11. 9.28
11. 9.28

Killed
Killed

Negative
Negative

H.P.B.

Very occasional islet
k.b

17. 6.27
17. 6.27

Subpleural plaque large, grey
Silicotic nodules, £Iung.',Small, black

29, 7.27
11. 9.28

Tuberculosis Positive
Negative
Killed

Á.S.

Slight silicosis

2.a
2.b

27. 5.27
27. 5.27

Subpleural irregular scars
Silicotic nodules, lung. Small, black

25.11.27
25.11.27

S.F.D.

Slight silicosis

l.a
l.b

19. 9.27
19. 9.27

Subpleural plaques grey
Silicotic nodules, lung. Small, black

11. 9.28
Killed
5.10.27 Septicaemia

ll.a

10. 9.28

Silicotic nodules, lung. Small, black

1. 2.29

11.è

10. 9.28

Silicotic nodules, lung. Small, black

9. 1.29

12.a

15. 9.28

2.10.28

12. b

15. 9.28

Subpleural and deep large irregular
foci
R o o t glands tuberculo-silicotic

6.a
6.¿>

8. 7.27
8. 7.27

Silicotic nodules, lung. Small, black
Silicotic nodules, lung. Small, black

11. 9.28
1 1 . 9.28

Killed
Killed

Negative
Negative

V
W
M
t»
M

M
ö
O
>-}

Negative
Negative

M
Ci

G.L.Q.

W.A.S.

w.w.

Slight silicosis

Moderate silicosis

Lobar
pneumonia
Splenic
abscess

Negative
Negative

Pyaemia

Negative

6. 3.29 Tuberculosis
Killed
Killed

Positive
Negative
Negative

M.R.C.

Moderate silicosis

8.a
8.6

27.10.27
27.10.27

Silicotic nodules, lung. Small, black
Root glands soft, black

Negative
KUled
11. 9.28
31.10.27 Septicaemia Negative

L.W.P.

Moderate silicosis

9.a

27. 1.28

30. 1.28

Septicaemia Negative

9.6

27. 1.28

Silicotic nodules, lung. Moderate size,
black
Large silicotic nodules. Tuberculosilicotic

30. 1.28

Septicaemia Negative

Large area tubérculo-silicosis
Large area tubérculo-silicosis

20.11.29
20.11.29

T.de B.

Moderate silicosis

16.a
16.6

31.12.28
31.12.28

TC.C.

Moderate silicosis

17.a
17.6

4. 1.29
4. 1.29

J.R.

Moderate silicosis

10.a
10.6

12. 4.28
12. 4.28

Silicotic nodules, lung. Large, black
Silicotic nodules, lung. Large, black

12. 7.29
12. 7.29

Root glands tuberculo-silicotic
Root glands tuberculo-silicotic

9. 1.29
9. 1.29

Negative
Negative

Negative
Killed
Septicaemia Negative

en
V

Killed
Killed

Negative
Negative

C.J.S.

Moderate to marked silicosis

13.a
13.6

17.10.28
17.10.28

Tuberculo-silicotic nodules, lung
Tuberculo-silicotic nodules, lung

12. 7.29 Tuberculosis Positive
Negative
15.12.28
Enteritis

P.J.A.

Moderate to marked silicosis

14.a
14.6

30.11.28
30.11.28

Root glands tuberculo-silicotic
Nodules from lung tuberculo-silicotic

5. 7.29 Tuberculosis Positive
14. 6.29 Tuberculosis Positive

V.J.D.

Moderate to marked silicosis

19.a
19.6

23. 4.29
23. 4.29

Small root glands tuberculo-silicotic
Small root glands tuberculo-silicotic

20.11.29
20.11.29

C.M.J.

Well-marked silicosis

5.a
5.6

17. 6.27
17. 6.27

Subpleural plaques black
Nodules from lung tuberculo-silicotic

18. 6.27 Septicaemia Negative
5. 8.27 Tuberculosis Positive

J.R.B.

Very well-marked silicosis

18.a
18.6

9. 4.29
9. 4.29

Massive area tuberculo-silicotic
Root glands tuberculo-silicotic

12. 7.29
12. 7.29

Killed
Killed

Negative
Negative

1-3

>
2
ö
•tí

>
•3

a
o
e
o
o
"<
o
•9

r
o
O
ce

Positive
Positive
to

248

PAPERS PRESENTED TO THE CONFERENCE

obtained. These cases were, with two exceptions, in a state of
marked tubérculo-silicosis. In one exception (H.P.B.) the tissue
was taken from the subpleural region but was grey in colour, in
the other (W.A.S.), though showing no tubérculo-silicosis of the
lung itself, was from a gross tuberculo-silicotic gland.
If any conclusion can be drawn from the results of these experiments it would seem, t h a t they indicate that silicosis does exist
and progress as a separate entity apart from tuberculosis. Further,
as a result of our examination of the weights, the progress of the
animals and the type and number of the tuberculosis lesions found,
it would appear that an attenuated type of organism is associated
with tuberculo-silicotic lesions.

SUMMARY

The site of the silicotic lesions in the lungs appears to have an anatomical basis. This is related to the positions in which lymphoid tissue
has been described.
The first evidence of change in the lung as a result of the inhalation
of irritant dust is a " dry " bronchiolitis.
The manifestations oí the silicotic process appear first in relationship
to terminal bronchioles, vestibules and atria.
The silicotic process is a fibroblastic reaction followed by a dense
fibrosis of nodular type, in which fat accumulation occurs in all stages
and increases pari passu with the size of the nodule.
Massive fibrosis may result from the progress of uncomplicated
fibrosis.
Infection modifies the silicotic process in the direction of excessive
fibrosis.
The important infective factor is tuberculosis.
The macroscopic changes are usually seen, first in lymph glands then
in pleura and lung substance.
The main complications are related to tuberculosis; others present
are chronic bronchitis and emphysema.
Silicosis may exist and progress without superimposed tuberculous
infection.

Fio. i . •—• From a case of primary carcinoma of the lung with widespread
lymphatic permeation. Section shows a bronchus in cross section, portions
of septa, and surrounding air vesicles. The carcinoma-filled lymphatics are
shown in the wall of the bronchus and in the septa, while the alveolar walls
remain free from the growth.

FIG. 2. — From a case of slight silicosis. This section shows the entrance
to a lobule with several aggregations of pigmented cells. It is in these
aggregations that the future silicotic nodule develops.
Witwatersrand : Pathology 0/ Silicosis.
[To face page 24S.]

9 bis

Fie. 3. — Dry bronchiolitis from a case of slight silicosis. Section of
lung showing terminal bronchiole, vestibule, etc. Pigmented cells are present
in the walls and almost complete denudation of the lining epithelium is
shown. There is no evidence of exudate.

FIG. 4. — Very advanced silicosis. A' small, well-defined, circular area
of calcification is shown in the centre of one of the nodules. This type of
change is also seen in nodules of less advanced cases.

I''ic. 5. — From a case of early silicosis. Section shows an aggregation
of pigmented cells in the wall of a bronchiole. In the centre of the pigmented
mass the earlv, cellular, fibroblastic reaction is seen.

FIG. .6. — Early simple silicosis. Higher power section of pigment cell
aggregation, with slightly more advanced central fibroblastic reaction.

FIG. 7. — Slight silicosis. Infective type. A pigment cell aggregation
is shown with central fibroblastic change. This is the cellular type resembling
granulation tissue. Blood vessels are absent. In the later stages, when
fibrosis has taken place, breaking, down of the central mass occurs early.

F;G. 8. — Early simple silicosis. Section shows a fibrotic nodule situated
in the region of a terminal bronchiole. It consists of a mass of irregularly
arranged, well formed fibrous tissue in the centre, surrounded in turn by
concentric laminae of fibrous tissue, fibroblasts and pigmented cells. . Dust
cells and almost the whole of the carbon pigment have disappeared from
the fibrous tissue zone. There is no evidence of breaking down.

V7-:-

ÉM,

FIG. 9. — Early simple silicosis. A composite nodule is shown. It consists
of at least three centres of origin. Each centre represents the original site
of a mass of pigmented cells in relationship to a bronchiole, vestibule or atrium.

••^
'.¡Ss.

> <«.si Îî ^, A
V ¥SSP~ < ¿ f
. i f i ä i » ^ ,,--v

ïf-Si-.'jSiSs- >».••

«át^

Fio. 10. — Well-marked silicosis. Massive area of single and large composite islets. The islets are contiguous, causing compression and collapse of
the intervening lung tissue. The bronchioles are probably occluded in this
type of change. The larger blood vessels appear to be unaffected. All these
nodules are composed of dense fibrous tissue and show no breaking down
or other sign of infection.

FIG. 11. — Well-marked silicosis. Two large. well-developed subpleural
nodules are shown in this section. Where the nodules approach the surface
no pigmented cells are seen. As a rule the subpleural islet is more flattened,
it projects above the surface and a thicker layer of laminated fibrosis is
seen just under the pleura.

FIG. 12. — Early silicosis. -Infective type. This nodule consists of a central
mass of fibrous tissue, which shows a tendency to break down. This is surrounded by a very cellular fibroblastic layer and an outer pigment, cell zone.
In a later stage the central portion will become quite necrotic without any
of the usual signs of tuberculosis.

Fin. IS. — Advanced tubérculo-silicosis. This section shows a second
type of massive fibrosis. It consists of numerous nodules, many of which
have coalesced. In the larger masses there is evidence of central caseation.
The usual signs of tuberculosis (follicle formation and giant cells) are absent.
Material such as is shown here usually gives a positive biological test for
tuberculosis.

FIG. 14. — Advanced tubérculo-silicosis. This section shows a massive
area of tubérculo-silicosis. The nodules have coalesced and the whole structure has become converted into a pigmented, necrotic mass. Tubercle follicles
and giant cell formations are absent. This type of lesion also gives a positive
biological test for tuberculosis.

THE CLINICAL PATHOLOGY, RADIOLOGY
AND SYMPTOMATOLOGY OF SILICOSIS
TWO PAPERS

INTRODUCTORY

The object of these two papers is to present a concrete account of
silicosis as met with in South Africa, from the several aspects of its clinical
pathology, radiology and symptomatology, and particularly from the
aspect of the correlation which has been found to exist between the
results of these different methods of investigation of the disease, as an
aid to formulation of precise criteria for its practical diagnosis.
Such precise criteria are of much practical importance, since silicosis
has become in many countries the subject of a legal system of compensation as an " occupational disease ", but their formulation is a matter of
some difficulty, inasmuch as the silicotic process develops from minute
beginnings extending over a considerable period of time, during which
health and functional activity are in no way disturbed. It is therefore
of practical importance to determine at what point that process produces
results which can be regarded as a condition of definite " disease ".
The diagnosis in such circumstances must be " pragmatic " rather than
simply academic.
It is impossible, in our experience, to deduce a practical standard of
diagnosis from accounts of the disease furnished separately by the
pathologist, the radiologist, and the clinician. Clinical examination is
obviously an essential factor in the decision in any individual case, since
it provides us with important information, which we cannot otherwise
obtain, regarding the general and local condition of the patient, the
degree of incapacitation, if any, which exists, and the presence or absence
of complication by active infection, or by disease of other organs. But
in the case of such a disease as silicosis, in which, in respect of the
diagnosis of the earliest stages of the condition, clinical evidence is in
many cases inconclusive and may be misleading, such evidence taken by
itself is an insufficient guide. The standard of diagnosis which we seek,
while in no way ignoring the clinical factor, should rest as far as possible
upon an objectively demonstrable basis. Only so can we reach an
approximately uniform standard and one which can be described in
terms which are generally intelligible to other people.
Physical measurements of respiratory function, such as vital capacity,
respiratory force, etc., give results which are objective so far as they go,
but they show such considerable individual variations, and are so readily
modifiable by subjective factors, including the psychical attitude
towards the test of the person examined, that they do not in themselves
supply a sufficiently precise guide.

250

PAPERS PRESENTED TO THE CONFERENCE

There remain in the living subject radioscopy and radiography, and
in the last resort the pathological condition found after death. Radiography, again, has its limitations, since on the one hand not all forms of
pulmonary fibrosis which it reveals, even in miners, are of silicotic origin,
and on the other hand certain types of radiograph which do not show
unequivocally " specific " signs of silicosis, may yet in certain
circumstances be legitimately regarded as affording evidence of the
presence of a silicotic factor in the case. One can only obtain full value
from the radiograph when one is able to interpret it in the light of
experience derived from extensive pathological observation. Only
when one has been able to correlate the results of pathological observation
in a large number of cases with radiographs taken from the chests of the
same individuals shortly before death, and with the results of clinical
examination made during life, is one in a position to obtain the accurate
knowledge which is required to formulate a reliable general standard
of diagnosis. The very extensive material at the command of the
Miners' Phthisis Medical Bureau in each of the three directions mentioned
has enabled it to effect this triple correlation in a large series of cases.
The systematic " periodical " examination of working miners which
forms one of its main functions has provided it also with the opportunity
of observing, in many hundreds of cases, the first appearance of the
earliest clinical and radiographic signs of silicosis, and to follow their
subsequent development.
An accurate standard of diagnosis in silicosis should rest on the triple
correlation described. But, when this has been effected, it will be found
that, when interpreted in the light of this correlation, a radiograph
which is of high technical quality, and 'which is taken instantaneously,
forms the most reliable single diagnostic criterion which we possess. It
provides us with a general basis of diagnosis which is at once objective
and trustworthy, in so far that it narrows down the issue by the exclusion
of cases which do not show certain determined characteristics. But it is
never the only factor in a decision. The final adjudication in any
individual case must always incorporate the additional evidence supplied
by expert clinical examination, which indeed is frequently the deciding
factor, particularly in borderland cases. It is assumed also, as a matter
of course, that the previous industrial and medical history of the
individual has been thoroughly investigated. In the light of what has
been said it will, we think, be found convenient to deal with the subject
of our discussion under two main headings. It is proposed, therefore,
first to discuss briefly some aspects of the clinical pathology of silicosis,
considered particularly in relation to pathological diagnosis. This will
provide us with a summary view of the general character and course of
the disease. Thereafter the clinical and radiographic diagnosis of
silicosis will be dealt with.
The two papers submitted are the result of team work. Drs. A. Sutherland Strachan and F. W. Simson, of the pathological staff of the South
African Institute for Medical Research, who conduct the routine
pathological work for the Bureau, have taken a large part in the preparation of the first paper, which embodies several important new observations
made by them upon the pathology of the disease. Dr. Simson is also
responsible for the illustrations representing the pathology of simple and
infective silicosis (see figs. 1 to 10). Dr. W. Steuart, Radiologist to the
Bureau, has collaborated in the preparation of the sections relating to
radiography in the second paper. Members of the Bureau have also
rendered valuable co-operation, particularly Drs. E. H. Phillips and
S. W. Verster in recording and classifying the series of over 350 " correla-

PATHOLOGY, RADIOLOGY AND SYMPTOMATOLOGY

251

tion " cases, Dr. D. A. Ogilvie in investigating the causes of death in cases
of silicosis, and Dr. J. G. McMenamin in recording the distribution of
the different varieties and degrees of fibrosis, as indicated by the
radiograph, amongst initial examinees and working miners. Mr. J. H.
Dowds, of the University of the Witwatersrand, conducted the series
of physical tests on non-silicotic and silicotic miners, the general results
of which appear in the second paper. The series of prints illustrating
radiographic appearances in silicosis (films 1 to 22) have been reproduced
by Kodak, Ltd., Johannesburg, from negatives taken at the Bureau.
The Chairman of the Bureau (Dr. L. G. Irvine) is responsible for the
actual form of both papers, which with several modifications follow
closely and in parts verbally the lines of a communication on the subject
contributed by him to the meeting of the Permanent International
Committee for the Study of Occupational Diseases held at Lyons in 1929 '.
One may add that the conclusions set out are based almost wholly
upon the practical experience gained by the writers from the material
made available from the work of the Medical Bureau. They will be
found, however, to be in substantial agreement with the presentation
of the subject in the paper on " Silicosis on the Witwatersrand ", by
Watt, Irvine, Steuart and Pratt Johnson, published as an appendix to
the General Report of the Miners' Prevention Committee in 1916 -'.
Since in these papers we are dealing solely with South African silicosis,
the references made to the work of other writers have been practically
confined to the local literature of the subject.
The figures and films mentioned in the two papers are given after
page 294.

I. — THE CLINICAL PATHOLOGY OF SILICOSIS
BY L. G. IRVINE, M.A., M.D., CM., B.SC. (PUB. H.) (EDIN.), CHAIRMAN,
MINERS' PHTHISIS MEDICAL BUREAU; F. W. SIMSON, M.B.,
CH.B. (EDIN.), PATHOLOGIST, SOUTH AFRICAN INSTITUTE FOR
MEDICAL RESEARCH; AND A. SUTHERLAND
STRACHAN,
M.A., B.SC, M.D. (GLASGOW), PATHOLOGIST, SOUTH AFRICAN
INSTITUTE FOR MEDICAL RESEARCH
There are two factors which are predominant in the course
of cases of silicosis as we meet them in South Africa — silica dust
and tuberculous infection. Other factors, such as intercurrent
non-tuberculous infections, may modify the course of the disease,
and may indeed not infrequently be the immediate cause of death
' L. G. IRVINE: " The Diagnosis of Silicosis as an Occupational Disease. "
Rapports; Réunion de la Commission Internationale Permanente pour l'étude
des Maladies professionnelles, p. 43. Lyons, 1929.
2

H. WATT, L. G.

IRVINE, J. PRATT JOHNSON and

STEUART:

" Silicosis (' Miners' Phthisis ') on the Witwatersrand. " General Report of
the Miners' Phthisis Prevention Committee, p. 81. Pretoria, 1916.

252

PAPERS PRESENTED TO THE

CONFERENCE

in silicotic miners as in other people. But apart from this circumstance, the predominant factors are those just named. The typical
history of an average case is that it begins as a dust fibrosis and
ends as a dust phthisis. Without dust there would obviously
be no silicosis, but, without the predisposition to tuberculous
infection which the presence of silica dust in the lung induces,
silicosis would not be the gravely disabling and fatal disease which,
in its later stages, it becomes.
One uses the term " simple silicosis " to describe a condition of
fibrosis of the lungs which is produced by the long continued
inhalation of siliceous dust, and its subsequent entry into and
arrest within the lung, and which is unaccompanied by overt signs
of active tuberculous infection. This is the condition of the
immense majority of cases in the earliest detectable stage of the
disease, at which it first becomes notifiable, and at which also by
far the greater number of the men affected cease work underground.
The significance of such a case, however, is not what it is at
the moment, but what it may become. At the moment the affected
man is, generally speaking, quite in good health and has at the
most only a comparatively slight impairment of working capacity.
But in the majority of cases the disease tends sooner or later to
advance. There are wide individual variations. Some may
remain stationary practically indefinitely. Others may remain
stationary for long periods, and may then begin to show signs
of advance. In others again the progress of the disease is rapid
from the first. But, although these individual variations occur,
the general tendency to advance is on the whole fairly uniform.
And, although an uncomplicated silicosis may, and does, in itself
progress, and will do so up to a point even if the man affected
ceases to work underground, the most important factor which
accounts for the progressive tendency manifest in most cases of
the disease is infection, and particularly tuberculous infection.
The " simple silicosis " tends in most cases to become an " infective
silicosis ". The terminal stage of the disease, if it be reached, is
one of obvious active tuberculosis in the silicotic lung. But not
all cases reach that stage.
In the present paper an attempt is made to present a brief review
of the respective roles played by the factor of dust and the factor
of infection in the course of the disease, considered particularly
in their bearing on the practical question of diagnosis, and of the
differentiation of the several " stages " of the disease of which a
system of legal compensation must take account.

PATHOLOGY, RADIOLOGY AND SYMPTOMATOLOGY

253

T H E DUST FACTOR IN SILICOSIS — T H E ORIGIN OF THE SILICOSIS
PROCESS

The genesis of the silicotic process has been repeatedly described 1 ,
and, although variations may exist in the precise interpretation
of the phenomena observed, there is substantial agreement as
to the general facti. By " the silicotic process " one means the
fibrotic changes produced in the lungs by the repeated inhalation
over long periods of a " phthisis-producing " dust which contains
free silica, in quantities greater than can be successfully dealt
with by the physiological protective mechanisms of the respiratory
organs.
Dr. J. McCrae 2 and later Drs. Watkins-Pitchford and J. Moir 3
showed many years ago that it is only the minutest particles
which gain entry into the lungs, and this observation is in conformity with the fact that their mode of entry is by phagocytosis.
Even if the expulsive functions of the epithelium and musculature
of the air-passages remain intact, dust particles may reach the
alveoli and some may be taken up into the lungs. The extent to
which this will happen will depend upon the intensity of the
exposure to dust and upon the physiological efficiency of the
defensive structures and function of the respiratory passages
and alveoli.
But one effect of the repeated inhalation of abnormal quantities
of silica dust is to produce in time a dry bronchitis and bronchiolitis,
with eventually a greater or less amount of denudation of the
epithelium particularly of the bronchioles. This condition may
be found in lungs which have undergone long-standing and repeated
exposure to dust, even in cases which do not yet show definite
signs of silicosis. It must eventually produce a situation which
1

A. H. W A T T , L. G. I R V I N E , J. P R A T T J O H N S O N and W . S T E U A R T , op.

cit.

W. WATKINS-PITCHFORD:
" T h e Industrial Diseases of South Africa."
S. A. Medical Record, 1914, Vol. X I I , No. 3, p . 33.
" T h e Gross Characters of t h e Silicotic L u n g . " Med. Jour, of S. Africa,
1915, Vol. X , No. 10, p . 167.
A. MAVROGORDATO: Studies in Experimental
Silicosis and other Pneumonoconioses. S.A. Inst. Med. R e s . P u b l n . XV. 1922.
Contributions to the Study of Miners' Phthisis. S.A. Inst. Med. R e s .
P u b l n . X I X , 1926.
2
J. M C C R A E : The Ash of Silicotic Lungs. S.A. Inst. Med. R e s . P u b l n . I l l ,
1913.
3

WATKINS-PITCHFORD

and

Refracting Particles seen in Microscopic
I n s t . Med. R e s . P u b l n . V I I I , 1916.

MOIR:

The

Sections

Nature

of Silicotic

the

Lungs.

Doubly

S.A.

254

PAPERS PRESENTED TO THE CONFERENCE

directly and increasingly facilitates the entry of dust into the lungs.
It appears to be an important factor in the original development of
definite silicotic changes in the lung substance, and to be an important
factor also in the further development of the latter.
When silica dust enters the alveoli it does so in company with
fine pigmented carbonaceous particles, derived chiefly from the
smoke of lamps and candles. The latter are taken up into the
lungs by the same agency and follow the same distribution as the
silica dust, and thus give to the lesions produced by the latter their
characteristic pigmented appearance. But mere excess of pigmentation in a lung does not necessarily spell silicosis, and, on the other
hand, in mines in which there is little smoke there may be silicosis
without any marked excess of pigmentation. In the cases we see
on the Witwatersrand the silicotic lesions are always pigmented.
But the relation is accidental, not essential, and the amount of
pigmentation which is present does not in itself afford a measure
of the degree of silicosis which may exist.
In the alveoli the dust and pigment particles are taken up by the
" alveolar phagocytes " or " dust cells ". Some of these are
expelled by way of the air passages and are expectorated; some,
and in time many, enter the lymphatic channels of the lung. The
" dust-cells " tend thereafter to follow the course of the lymph
channels by way of the peribronchial, perivascular and septal
lymphatics within the lung, and of the rich sub-pleural lymph
plexus, to the lymph glands at the root of the organ. In all of these
situations many " dust cells " with their loads of dust and pigment
undergo arrest, and the most important seats of arrest are the
sites in which small aggregations of lymphoid tissue have been
shown to exist in the normal lung x in relation particularly to the
peribronchiolar and perivascular lymphatics. The site of election
for arrest in the lung substance appears to be at the entrance to
the lobule; in the sub pleural region it as at the points of junction
of the lymph systems, of the lungs and pleurae. At these sites
the dust cells become aggregated in small discrete " clumps ",
and these points of clumping become the eventual seats of origin
of the fibroid " nodules " which form so characteristic a feature
of the developed disease. Given continued exposure to dust,
the process is a cumulative process.
Observation of many lungs in the earliest stages of the silicotic
1
Cf. especially W. S. MILLER: " Distribution of Lymphoid Tissue in the
Lung. " Anatomical Record, 1911, Vol. V.

PATHOLOGY, RADIOLOGY AND SYMPTOMATOLOGY

255

process has shown that fibrosis with associated pigmentation
begins first in the lymph glands at the root of the lung. There
appears next, most commonly, sòme increase in pigmentation in
the visceral pleurae, with, in parts, some irregular areas of slight
opacity, or of more definite thickening, indicative of concurrent
infection, past or present. The pigmentary changes in the pleurae
are usually at this stage of the process definitely in advance of the
similar changes which in turn become apparent in the lung substance.
The latter show on the cut surface of the organ as small discrete
pigmented islands, unassociated as yet with visible or palpable
fibrosis. Microscopic examination shows that the pigment is
almost wholly aggregated in the sites of clumping already described
as being associated with small aggregations of lymphoid tissue,
and in some of these small rounded foci of fibro-blastic reaction
may be observed. The alveoli are not affected; the septa show
no appreciable thickening; the lungs retain their normal resilience
on handling. But there is some amount of associated bronchiolitis
and bronchitis. These changes precede the appearance of definite
palpable " nodulation " ; at the most a very occasional small
palpable islet may be detected here and there, under the pleurae,
or in the lung substance.
Although the pathological development in the silicotic process
is continuous and cumulative from the earliest minute beginnings
of fibrosis, the changes produced up to this point, when considered
from the standpoint of their effect upon respiratory function, do
not constitute a definite degree of " silicosis ". They tend,
however, to produce a characteristic modification of the radiographic appearances, described in the Bureau's terminology as a
" commencing generalised fibrosis " (cf. film 6). It is suggested
that this is in some and probably in large measure associated
with the accompanying bronchitis and bronchiolitis, but it may
be in part also due to a fine fibrosis originating around the peribronchial and perivascular lymphatics.
The microphotograph shown in fig. 5 illustrates the condition
present.
THE

DUST

FACTOR IN

SILICOSIS —

" SIMPLE SILICOSIS "

If one employs the term " simple silicosis " to designate a
condition of silicosis which is unaccompanied by a clinically detectable or " overt " tuberculosis, one may say that, viewed from the
practical standpoint of effect upon respiratory function, the develop-

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ment of an appreciable degree of " simple " silicosis coincides with
the appearance of some amount of palpable miliary " nodulation "
under the pleurae and in the lung substance. We shall expand this
statement in a moment.
This condition of " nodulation " supplies a general and readily
recognisable standard, of diagnosis, and is the distinctive feature
of the disease, particularly in its earlier stages. The individual
silicotic " nodules " develop as a reactive fibrosis in the sites of
the minute " clumps " of " dust cells ", of which we have spoken
(cf. fig. 6). They form irregular " headings " along the course
of lymphatic channels, particularly, as has been said, at the entry
to the lobule, and in the subpleural area.
As the process of fibrosis increases, the individual nodules coincidently increase in size and number, so that they eventually become
distributed more or less widely throughout the lung substance,
although they show a predilection first and throughout for its
upper and posterior portions, and are always less obvious in the
more freely movable lower and marginal regions of the lung.
Under the pleural surface they have a similar general distribution.
The subpleural nodule is typically a firm, somewhat flattened
" plaque ". In the lung substance the individual nodule shows
as a dense, black, rounded structure, which projects slightly from
the cut surface, and is definitely palpable as firmer than the surrounding lung tissue, from which it is sharply marked off. The
microscopic structure of the developed nodule is characteristic.
In the centre is a core of typically acellular fibrosis, in which the
fibres are disposed irregularly, with dust and pigment particles,
derived from disintegrated dust cells, lying apparently free between
the meshes. Around the central area are concentric layers of
fibres, in the outermost of which the cellular elements are for the
most part apparent. The peripheral zone is still unorganised, and
is crowded with " dust cells " laden with dust and pigment.
The growth of the nodule is snowball fashion, by concentric
additions at the periphery. At first of " ornali " size (up to 2 mm.
in diameter), the individual nodule may, as the disease advances,
reach a size of 5 mm. or thereabouts; one would call the latter
type of nodule " large ".
The silicotic " nodule " forms so conspicuous a feature of silicosis
that for the purpose of rapid diagnosis one may describe the stage
or " degree " of an uncomplicated or " simple " silicosis in terms
of the number, size and density of the nodular elements seen upon
the cut surface of the lungs, when these organs are laid open by

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257

the knife. The Medical Bureau, for the practical medico-legal
purposes of its work, which demands the classification of the
disease into definite " stages ", is accustomed to distinguish four
" degrees " of simple silicosis — " slight ", " moderate ", " wellmarked " and " very well-marked ". And, speaking in general
terms, it may be said that, in the two former the nodules are
" small " and respectively " sparse " or " moderately numerous " ;
and that in the two latter they are " medium " to " large " in size,
and " numerous " or " very numerous ".
The distinctive characteristic of the silicotic process is that it
begins as a fibrosis which affects independently, simultaneously or
in succession, many different points in the lungs, so that the developed
disease is typically a generalised disease. And this character of
generalised change is equally apparent in the radiograph and in
the complex of physical signs and symptoms which distinguish
the condition. There are exceptions, however, to this statement,
to which we shall presently refer.
THE

MACROSCOPIC APPEARANCES IN

" SIMPLE

SILICOSIS "

It will be sufficient, from the aspect of pathological diagnosis,
to describe, in illustration of these general observations, the
macroscopic appearances of a typical case of " simple " or uncomplicated silicosis of a " moderate " degree, it being understood
that by " uncomplicated " one means a case of silicosis in which
there are no obvious signs of active tuberculosis or other infection.
In examining the lungs one should look for evidence of fibrosis in
the three sites mentioned — in the root glands, in the pleurae,
and in the lung substance.
In such a case the root glands will be found to be somewhat
enlarged, deeply pigmented, and firmer to the touch than is normal.
The surfaces of the visceral pleurae are for the most part smooth
and glistening. They show, however, a moderate or even considerable excess of pigmentation, in part merely in the form of a marbled
outlining of the underlying lobules of the lung, in part as a more
diffuse pigmentation, with areas of slight thickening, affecting
particularly the upper half of the organ. Where areas of welldefined thickening are present an infective origin of these may
be assumed. The inner, interlobar and diaphragmatic surfaces
are less affected. In association with these changes there will
be found scattered over the areas which show more marked pigmentary change a moderate number of small, sub-pleural nodules
17

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or " plaques ", which give the appearance and " feel " of a fine
mammilation.
The cut surfaces of the lung itself will also show excess of
pigmentation in the form of moderately numerous " small ",
discrete pigmented islands, and a considerable proportion of these
insular areas will be found to be the sites of well-defined, " small ",
firm, rounded and definitely palpable nodules of silicotic type.
Except for this, the normal resilience of the lungs on handling
is retained. The general appearance is thus one of a more or
less generalised " small " miliary nodulation of moderate amount.
The general character of the condition present is indicated in
figs. 1 and 7. It is also very well brought out in the radiograph
of such a case (cf. film 9). In the radiograph both lung fields
will be seen to have, throughout, a characteristic " mottled "
appearance, produced for the most part by the shadows thrown
by individual " small " nodules. This characteristic discrete
" mottling " is the one " specific " radiographic sign of silicosis.
At this stage of silicosis, microscopic examination shows that,
except perhaps in the immediate neighbourhood of the nodules,
there is no evidence of alveolar fibrosis. Nor is there evidence of
any definite thickening of the interlobular septa or the trabeculae
of the lung. A slight degree of emphysema may be present. Apart
from the effects of the coincident bronchitis and bronchiolitis,
any interference with respiratory function which may exist would
appear to be due to some slight limitation of the expansibility of
the lungs; but, judged by measurements of vital capacity, this
is not on the average at all marked.
This is the general picture. There is, however, a type of
case in which the presence from the outset of an infective element
in the process of silicotic fibrosis is strongly suggested.
It is not uncommon, for example, to find that in some cases
the pigmented fibrotic lesions take the form of more massive and
uniform, although still moderate, areas of fibrosis, or of a cluster
of unusually large irregular nodules, confined or practically confined
to the apical regions of the lungs, and associated with a well-marked
thickening of the overlying pleura. The remaining portions of
the lung show no obvious silicotic lesions.
Or again, we may find nodules of this larger atypical form,
scattered or clustered here and there, in lungs whose general
condition is that of the more uniformly distributed miliary nodulation of a typical silicosis.
These atypical nodules do not conform to the description

PATHOLOGY, RADIOLOGY AND SYMPTOMATOLOGY

259

previously given. They are larger and more irregular in shape
than the typical silicotic nodule, generally a greyish black in
colour, and stippled perhaps with points of necrosis and sometimes
of caseous or calcareous change. Their minute structure differs
also from that of the typical silicotic nodule. Although portions
of these larger nodular formations may show the typical concentric
arrangement of fibres, in other portions the fibres may be found
to be distributed in irregular zones enclosing focal areas of necrosis.
One or two of the root glands corresponding to the areas in which
these irregular nodules are present may be found to show a similar
appearance.
One has for long held the view that in most cases lesions of this
atypical character are indicative of past or present infection and
that many at least are the product of a localised low-grade tuberculous infection, occurring during the development of the silicotic
lesions, and this is the more probable inasmuch as dust and the
tubercle bacillus are both phagocyted by the same type of cell.
Where caseation or focal necrosis is present the association of an
infective element is clear. Further, a series of animal inoculation
experiments recently carried out by two of us (F. W. Simson and
A. S. Strachan) with material derived from lesions of this type,
which showed no obvious evidence of tuberculous infection, has
demonstrated its presence in a considerable number of instances.
One concludes therefore that in many cases of clinically " simple
silicosis ", even at its earliest detectable stage, an element of low
grade and latent tuberculous infection may already be present in
association with certain of the " silicotic " lesions. And the
circumstances suggest that in such cases the infection is at least
frequently an infection by inhalation 1.
Just as one finds in a precedent or coincident bronchitis and
bronchiolitis a determining factor in the original development of a
definite condition of silicosis in the lung substance, so here one
appears to find at least one determining factor in the advance
from a clinically " simple " to a clinically " infective " silicosis,
which characterises the further history of a majority of cases
of the disease.
The same qualifications regarding the possible presence of
limited foci of low-grade infection applies equally and usually
in greater measure to the later stages of clinically " simple silicosis ".
1

op.

A. MAVROGORDATO: "Contributions t o t h e S t u d y of Miners' Phthisis ",
cit.

260

PAPERS PRESENTED TO THE CONFERENCE

The more marked degrees of " simple silicosis " show more marked
changes of the same general type as those described above. The
nodules in the lung substance are for the most part larger and
usually more abundant, and microscopical examination shows
that many are of composite structure, resulting from the fusion
of several originally more or less distinct small nodular formations.
The pleurae also show more marked nodulation and more definite
thickening. In the more advanced stages bronchitis is well marked
and the bronchi are obviously thickened. So, too, may be the
septa and trabeculae, but this condition is never gross. Growth
of the nodules, particularly where they are closely aggregated,
produces some obliteration of alveoli, but apart from this, alveolar
fibrosis is not an obvious feature except in areas where infection
is present. There is always in the later stages some amount of
emphysema. Figs. 2 and 8 show the condition in " well-marked ",
and " very well-marked " cases, and this is also well portrayed
by the radiograph (films 11 and 13).
THE INFECTIVE FACTOR IN SILICOSIS •— " INFECTIVE SILICOSIS "

Silicotic lungs, like other lungs, may become at any time the
seat of a complicating infection. This is the more likely because,
as Dr. Mavrogordato is fond of saying, " the silicotic lung is
generally a dirty lung ". The accompanying bronchitis in itself
makes it so. Evidence of infection may be obvious — lobar
pneumonia may be found, or influenzal pneumonia, or an acute
caseating tuberculosis, or a terminal miliary tuberculosis, each
presenting its usual distinctive pathological features.
More chronic or less massive acute infections tend, however,
to produce somewhat atypical results in a silicotic lung; they tend
to stimulate the development of fibrosis in the area affected by them.
This is particularly the case with low-grade tuberculous infections,
although the tendency is not confined to such infections alone.
It is common knowledge' that a lung affected by silicosis is
peculiarly prone to become infected with tuberculosis. Several
circumstances may contribute to this predisposition. First, there
is the point emphasised by Mavrogordato x that the humid, dustladen atmosphere of a mine forms a vehicle which directly facilitates
the entry of the tubercle bacillus into the lung. We have already
stated that pathological observation has led one to the belief that,
1

Ibid.

PATHOLOGY, RADIOLOGY AND SYMPTOMATOLOGY

261

in many cases of clinically apparently uncomplicated silicosis
there is evidence of an early association of an element of low-grade
tuberculous infection with certain of the developing silicotic lesions,
and the distribution of these " infective " lesions is frequently
very suggestive of an inhalation infection. Active tuberculosis
may develop later on from such original foci, or may be due to
further infection from other sources within or outside the lung.
A second circumstance is that the sites of silicotic lesions provide
possible points of arrest of bacteria in the lymphatic system of
the lung.
And finally there is to be considered the view which has
recently been advanced on experimental evidence by Gye and
Kettle, namely, that finely divided silica acts as a soluble protoplasmic poison, particularly to endothelial cells, and has in consequence a specific effect in determining the selection by a tuberculous
infection of sites where silica is aggregated 1 . One may regard
all of these factors as contributory to the predisposition in question.
As we have said, typical acute tuberculous lesions are frequently
met with in silicotic lungs, practically unmodified. But it is
very characteristic of silicosis that, when a chronic tuberculous
infection affects a silicotic lung, it tends to pursue a modified
and atypical course — it runs to excessive fibrosis. Small infections
may go no further than to produce a scattering of large nodules
of the " infective " type already described; or these maybe clustered
or become coalesced to form limited areas of consolidation. In more
extensive infections the process takes the form of a more diffuse
infective fibrosis, with the production of large masses of uniform
consolidation, in which, however, the original " nodular " basis may
still be discernible. In the earlier stages of their development both
the isolated nodules and the larger masses are typically of a pale
grey colour and of only moderately dense consistence, and indications of caseation may sometimes be apparent in them. In oldstanding cases the colour is dark grey or black, and the consistence
is often extremely dense, so that the larger areas may form, at this
stage, more or less extensive and sometimes very extensive areas
of a massive pigmented " fibroid consolidation ", such as appears
in no other disease (see figs. 3, 4, 9 and 10). In some cases these
areas may show no macroscopic signs of tuberculosis; in others,
1

W. E. GYE and E. H. KETTLE: " Silicosis and Miners' Phthisis ", Brit.
Jour. Expe.r. Path., 1922, Vol. I l l , p. 241; and E. H. KETTLE: " Influence
of Silica in determining B. Tuberculosis Infections ", Brit. Jour. Exper. Path.,
1924, Vol. V, p. 158.

262

PAPERS PRESENTED TO THE CONFERENCE

however, areas of caseation or of a terminal necrosis with softening
or cavitation may be present, and tubercle bacilli may be recovered
from the necrotic material. It is to this characteristic product of
the conjunction of a tuberculous infection with silicosis that the
term " tubérculo-silicosis " was originally applied 1 . " Tubérculosilicosis " is the modification produced in silicotic lesions by a chronic
tuberculous infection. Similar changes are found in the corresponding root glands.
We have pointed out that the " infective " nodule is typically
of larger size than the nodular formations of an uncomplicated
silicosis, and one may say in general that in any case of silicosis
an unduly large size or a marked irregularity in size in the islands
of fibrosis, or a marked tendency to their coalescence is suggestive
of the presence of an infective element. These variations are well
brought out in the radiograph (compare, for example, films 11,
13 and 15 with films 12, 14 and 16). Indeed, in cases of advanced
silicosis many of the nodules may be of the " infective " type,
whether by activation of an original minute included focus of
infection, or by further infection at the periphery of the nodule.
The account which has just been given of the manner in which
the presence of a chronic tuberculous infection in a silicotic lung
results in the production of infective lesions marked by an excessive
fibrosis, suggests that other infections may in the same circumstances
produce similar results. One may agree with Mavrogordato 2 and
others 3 that this may occur and that areas of massive fibrosis may
in some instances be the end result of the organisation of local
areas of unresolved " pneumonia " of non-tuberculous origin.
Again, in a good many instances of " fibroid consolidation " the
appearances, both macroscopic and microscopic, suggest a simple
growth and close aggregation of originally discrete silicotic nodules,
in which there are no indications of tuberculous or other infection.
Such a condition might result from obliteration of individual
lobules and local collapse. With the exception of the type of lesion
fust described, massive fibroid consolidation in the silicotic lung spells
infection, past or present ; and in the majority of instances the infection
is tuberculous, and the lesions are " tuberculo-silicotic ".
The gross infective lesions which we have described are not often
1

L. G. IRVINE, op.

cit.

A. MAVROGORDATO: "Studies in Experimental Silicosis and other
Pneumonoconioses ", op. cit.
3
W. WATKINS-PITCHFORD : " The Industrial Diseases of South Africa ",
op. cit.

PATHOLOGY, RADIOLOGY AND SYMPTOMATOLOGY

263

seen in a lung which is otherwise in a stage of quite early silicosis;
they are typically a late complication. Nevertheless, in some
instances, as has already been noted especially in cases which are
clinically of a " phthinoid " type, well-marked circumscribed lesions
of this character may be found from the first, particularly in the
apical regions, although in the remainder of the lung little or no
evidence of silicotic change may be present. In such cases the
distribution of the lesions is that of a simple apical fibroid tuberculosis.
When a tuberculous infection develops acutely in a silicotic
lung, the downward progress of the case is usually rapid. But the
modification of a chronic infection by its conjunction with silicosis,
which we have described, appears to tend to two results. The
excessive fibrosis which is produced tends, on the whole, to retard
the spread of the infective process to other portions of the lung
and to other organs of the body, but at the same time renders it
less susceptible of " c u r e " . The retardation and limitation of
the infection which may thus be occasioned is illustrated in the film
which is shown as film 18 taken from a mine official who was
awarded compensation some years ago as the subject of tuberculosis
with silicosis, with evidence of sub-apical infection of both lungs.
The condition of this man's lungs has remained practically unchanged for five years.
Another feature of interest is frequently seen in old-standing
cases of silicosis, namely the presence of extensive calcareous
deposits in the nodules, indicated by the particularly bright
appearance in the negative of the shadows thrown by them. In
some cases the great majority of the nodules may show calcareous
change. Film 17 is a good example. That this is the condition
which such radiographs represent has been proved post-mortem.
In view of the fact that calcareous deposit may occur in any lesion
associated with excessive fatty deposit, one is not justified in
accepting the hypothesis that this condition is indicative of a
previous widespread tuberculous infection of the silicotic lung.
It is nevertheless a striking phenomenon.
One may add here a few further observations. As we have seen,
some amount of bronchitis is a constant concomitant of silicosis.
Emphysema, however, is not an important feature in the early
stages, although it is commonly present and may be well marked
in the more advanced conditions. Cardiac dilatation and hypertrophy is uncommon in the cases we meet with nowadays, and its
amount when present appears to be dependent on the degree

264

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CONFERENCE

of emphysema which exists. The presence even of extensive areas
of fibroid consolidation does not in general appear to lead either t o
dilatation or hypertrophy of the heart. Bronchiectasis is definitely
a rare complication. The results of the examination of a large
series of urines in silicotic and non-silicotic miners l do not suggest
that impairment of renal function is more common in the former
than in the latter, and pathological observation supports this
conclusion. Nor, so far as our local experience goes, does silicosis
appear to predispose to hepatic cirrhosis.

T Y P E S AND GENERAL COURSE OF CASES OF SILICOSIS

From what has been said it will be apparent that the actual
pathological condition found in individual cases of silicosis will
present many variations. The accompanying illustrations (figs. 1
to 4) may serve to give some indication of the appearances which
may be met with in different types of case in miners of European
stock. Figs. 4 A and 4 B represent the more grossly infective type
of tubérculo-silicosis which is more characteristically met with in
certain cases of the disease in native mine labourers.
There is a very significant difference of type in cases of silicosis,
according as the dust factor or the infective factor is predominant
in its causation or in its development. The first condition, in which
the dust factor predominates because exposure to dust is heavy,
produces the type of case with which we were familiar in the first
twelve or fourteen years which succeeded the turn of the century;
the mines then were very dusty and they were dry. It was marked
by the presence of extensive fibroid consolidation, with large,
bulky, heavy lungs, in which the excessive development of fibrosis
overwhelmed and frequently almost wholly obscured the evidence
of coincident infection, except as a rule in the terminal stage.
This is the " classical " type of silicosis. But those who are
familiar with the history of silicosis on the Rand are aware t h a t ,
during the past fourteen years or so, coincidently with the improvement of dust conditions underground, there has occurred a progressive modification in the cases which have arisen, so that the prevalent
type of infective silicosis with which we are familiar to-day is one in
which the infective factor is predominant, or at least more evident,
and the dust factor is relatively less prominent than formerly.
1
Report of Miners'
Pretoria, 1929.

Phthisis

Medical

Bureau

for year ending

31 July

1928.

PATHOLOGY, RADIOLOGY AND SYMPTOMATOLOGY

265

Sufferers from silicosis of the " classical " type frequently
retained a robust general appearance to within a few months of
death. And although, of those who died from the disease, the
majority died of a rapid terminal breakdown, with cavitation
and emaciation, in many other cases death resulted definitely
from heart failure, with cardiac dilatation, cyanosis, ascites and
oedema of the lower limbs, without clinical evidence of active
infection and without emaciation. One has not seen the latter
mode of death for a good many years. Those who nowadays die
directly from the disease do so with obvious signs of active tuberculosis, from progressive asthenia, or from haemorrhage.
The cases which have originated within the past nine or ten
years have exhibited up to a point a more progressive tendency.
One reason for this may be that the diminution of dust in mine air
has tended to a diminution of the limiting and retarding influence
of excessive fibrosis upon the spread of infective lesions in and
beyond the lung. On the other hand, in the later type of case the
final stage of serious incapacitation appears to be more prolonged.
The terminal break-down in the older " classical " type of case
was apt to be much more rapid.
For although this change in the type of silicosis has been in part
directly due to a change in occupational conditions, it has also
been due in part to a change in the type of miner. The Witwatersrand miners in the early days, before and just after the South
African War, were almost wholly men of overseas birth and training,
derived from older long-settled and industrialised mining communities, men for the most part of originally robust physique,
with a relatively high immunity to tuberculosis. But, especially
in the last twenty-two years, there has been a steady increase in
the number and proportion of miners of South African birth, drawn
mainly from an agricultural instead of an industrialised community,
and with, it may be presumed, a lower inherited or acquired
immunity to tuberculosis. To-day miners of South African birth
form over 70 per cent, of the " working miners ", and during the
past five years these men have contributed a majority of the new
cases of silicosis which have arisen. One finds too to-day that
men of the robust, broad-shouldered, deep-chested type (figs. 11
and 12) still run rather to the " classical " type of silicosis, and when
they have acquired the disease they tolerate it much better. The
originally "phthinoid " type of man, on the other hand (figs. 13 and
14), runs rather to the infective type of the disease and, having less
respiratory and constitutional reserve, does not stand it so well.

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We have in these remarks laid so much stress upon the importance
of the infective factor in silicosis, as it occurs on the Witwatersrand,
that it is perhaps desirable once more to emphasise the fact that
it is uncommon to find a condition of clinically obvious tuberculosis
present at the stage at which a silicosis first becomes detectable.
The very great majority of cases of silicosis found amongst working
miners, when first detected, are from the clinical standpoint cases
of uncomplicated or " simple " silicosis, without evidence of obvious
or " overt " tuberculosis. Nevertheless, in our belief, it remains
true to say that we should not think of " simple " silicosis merely
as a dust fibrosis, but as being, at least in many cases, a dust
fibrosis, which from its beginning as a clinically detectable condition,
is linked up with an element of latent tuberculous infection. The
after-history of these cases is in this respect significant. In the
majority of instances, as we said at the outset, silicosis is a progressive disease. The outlook of the individual case is mainly dependent
upon whether the infective element remains " bottled up " and
inactive, or whether, on the other hand, it becomes active, or a
further infection occurs from outside the lung. There are wide
individual differences, dependent no doubt in part upon constitutional, nutritional and environmental factors, but the tendency of the
majority of cases to advance is, on the average, singularly uniform.
It may be well, in order to give concreteness to this picture, to
quote a few definite figures 1. During the three years 1920 to 1923,
728 cases of " simple silicosis ", in what is legally termed the
" ante-primary " stage of the disease, were detected amongst
working miners. These were cases of a " slight " or of a " moderate " degree of silicosis. At the end of the sixth year subsequent
to the year of their detection, 557 of these men, or 76.5 per cent.,
were alive. Only some 26 per cent., however, were approximately
in their original condition; 27 per cent, were in the intermediate,
and some 23 per cent, were in the advanced stage of the disease.
Twenty-three and a half per cent, had died, and in 18 per cent.
death had been due to silicosis or to a cause (such, for example,
as an acute respiratory infection) to which silicosis was regarded
as having been contributory. The remainder had died from causes
unconnected with silicosis.
One may put these facts in another way. Mr. Spence Fraser,
Actuarial Adviser to the Union Government, informs us that the
i Report of Miners' Phthisis Medical Bureau for year ending 31 July 1929
(in press).

PATHOLOGY, RADIOLOGY AND SYMPTOMATOLOGY

267

average expectation of life of a case of silicosis when first detected
is 13.66 years. Some, of course, will die much sooner than that;
others will live longer. But on the average an early or " anteprimary " case will advance to the intermediate or " primary "
stage in about four and a half years, and the "primary" stage case
will reach the " secondary " stage of grave incapacitation in about
another four years. The average time that such a miner remains
in the secondary stage until he dies is seven years.
These figures indicate very clearly the inherently progressive
tendency manifest in most cases of silicosis. That tendency depends
almost wholly upon the factor of infection, and for practical purposes, apart from acute intercurrent respiratory disease, the
infection which matters in these cases is tuberculosis. It is possible
that the infective factor plays a more prominent role in silicosis
on the Witwatersrand than it does elsewhere, since, with us, the
European miners, generally speaking, work as overseers practically
side by side with a very large number of native mine labourers.
The African native is more susceptible to tuberculosis than the
European, and, although judged by the standard oí European
communities the incidence of tuberculosis amongst the mine
natives is not excessive, it is, by reason of their number, sufficient
to constitute a definite menace. We may add that amongst the
mine natives the incidence of silicosis is relatively much smaller
than amongst European miners, not because the former are less
susceptible to the effects of dust when subjected to similar conditions x but because, in general, the natives work on comparatively
short individual contracts, and their total service is, on the average,
not only much shorter but also less continuous. The latter fact
has a very important bearing upon the hygiene of silicosis. As
Dr. Mavrogordato has said, " Intermittent as opposed to continuous employment is perhaps the most effective single measure
against silicosis " 2. For these reasons, in contrast to the position
amongst the European miners, the overwhelming majority of cases
of compensatable disease which arise amongst mine natives are
cases of active, uncomplicated tuberculosis, or, in those of longer
service, of active tuberculosis preceded or accompanied by an element
of silicosis 3. It is from the side of the mine native, so far as
1
W . W A T K I N S - P I T C H F O R D : Report of Miners' Phthisis Medical
Bureau
¡or year ending 31 July 1924, p. 33.
2
A. MAVROGORDATO: " T h e Aetiology of Silicosis", Rapports,
Réun.
Commiss. Perman. pour l'étude des Malad. Profess., p. 15. Lyons, 1929.
3
Report of Miners' Phthisis Medical Bureau for year ending 31 July 192S.
Pretoria, 1929.

268

PAPERS PRESENTED TO THE CONFERENCE

underground conditions are concerned, t h a t the danger of tuberculous infection arises, both in the production of cases of frank
tuberculosis and of early infective silicosis amongst European
and native employees alike.
THE

IMMEDIATE CAUSES OF DEATH IN CASES OF SILICOSIS

We may suitably conclude this account of the clinical pathology
of silicosis with the subjoined tabular statement of the actual
causes of 543 deaths which have occurred amongst 1,623 cases
IMMEDIATE

CAUSES OF 543

ORIGINALLY

CERTIFIED

Immediate cause of death
Silicosis with tuberculosis
Silicosis in secondary stage
without obvious tuberculosis or other specified intercurrent disease
Influenza
Bronchitis
Pneumonia
Other diseases of respiratory
system
Malaria
Dysentery
Enteric fever
General paralysis of insane
Syphilis
Aneurysm, aortitis and angina
Valvular disease of heart
Other diseases of heart
Cancer of lungs (primary)
Cancer all other sites
Chronic rheumatism
Alcoholism
Cerebral haemorrhage, etc.
Other diseases of nervous
system
Nephritis
Other genito-urinary diseases
Diseases of prostate
Cirrhosis of liver and hepatitis
Appendicitis
Intestinal obstruction
Hernia
Other diseases of digestive
system
Deaths by accident or injury
Other causes
Undetermined
Total
1

DEATHS OCCURRING IN 1,623
AS HAVING

CASES

" SIMPLE SILICOSIS "

Originally primary
stage cases:
372 deaths
(a)

257 (69%) i i
1
[(76.5%)

Originally ante-primary
stage cases:
171 deaths
<f»

116 (68%)!'
• (72%)

28 (7.5%) ,
7
3
• (6-1%)
13 (3.5%)

7(4%) .
2
—
• (5.8%)
8 (4.6%) J

1
3
2
—
2
—
3
4
3
.—
1
1
1
3

—
1

—
3
1
—
5
—
1
1

1 (acute mania)
4
—
2
1
1
.—
1

2
14
2
5
372

•

—

1
•—
1
2
2
1
1
6
—
—
1

(3.7%)

1
10
1
—
171

The percentages shown are percentages of the total deaths.

(5.8%)

PATHOLOGY, RADIOLOGY AND SYMPTOMATOLOGY

269

originally certified when first detected as being the subjects of
" simple silicosis ". These cases fall into two groups:
1. The 895 cases of " simple silicosis " in the " primary " stage
detected amongst working miners during the three years 1917 to 1920.
Of these men, 372 had died up to 31 July 1929, and the immediate
causes of death are tabulated in column (a).
2. The 728 cases of " simple silicosis " in the " ante-primary " stage
detected amongst working miners during the three years 1920 to 1923.
Of these men, 171 had died up to 31 July 1929, and the immediate causes
of death are tabulated in column (b).
It will be seen that in both groups oí these cases approximately
three-quarters of the total deaths were caused directly by the
disease, and t h a t the evidence showed that recognised tuberculosis
was present in 68 or 69 per cent. The close similarity in the
proportion of deaths from tuberculosis with silicosis in the two
groups is remarkable, since the cases in the latter group were
detected when in a " slight " or " moderate " degree of silicosis
only, whereas in the first group all were cases in which the disease
had begun to produce some degree of disability. The inherent
predisposition to tuberculosis in cases of silicosis is nevertheless
seen to be practically the same in both groups, and the figures
give an approximate measure of t h a t predisposition. The only
other feature of this return to which we may call attention is that
acute respiratory infections, namely bronchitis and pneumonia,
even when taken together with influenza, account for only some
6 per cent, of the total deaths in each group.

II. — THE RADIOLOGY AND SYMPTOMATOLOGY
OF SILICOSIS
BY L . G . I R V I N E , M.A., M.D., C.M., B.SC. (PUB. H.) ( E D I N . ) , CHAIRMAN,
MINERS'

PHTHISIS

MEDICAL

BUREAU,

AND

STEUART,

M.R.C.S. (ENG.), L.R.C.P. ( L O N D . )

GENERAL

The variations in the pathological and clinical types of the
disease-complex we term silicosis, which depend partly upon the
relative and actual prominence of the dust factor or of the infective
factor in the cases concerned, and partly upon the type of man who
is exposed to the influence of these factors, render a succinct
account of the radiology and symptomatology of silicosis a matter
of some difficulty.

270

PAPERS PRESENTED TO THE CONFERENCE

From the medico-legal and clinical standpoint the Miners'
Phthisis Medical Bureau divides the cases it deals with into the
two classes of " simple silicosis " and " tuberculosis with silicosis ",
according as the silicotic condition present is unaccompanied or is
accompanied by obvious, active, or " overt " tuberculosis.

" SIMPLE SILICOSIS "

All cases of silicosis which do not exhibit signs of active tuberculosis fall, therefore, under this classification, into the broad class
of " simple silicosis ".
Quite a number of cases which are so classified may nevertheless
present radiographic or clinical indications of a past or present
infective element, which is not definitely active. Hence the
Bureau distinguishes in cases of " simple silicosis " between a
" predominantly silicotic " type and a '* partly or predominantly
infective " type of case, the latter term being applied to cases
presenting clinical or radiographic indications of an old or inactive
infection. The pathologist would no doubt regard cases of the
latter type as instances of " infective silicosis ". But they are
not cases of " tuberculosis with silicosis " in the medico-legal and
clinical sense above defined.
Clinically one finds that the " robust " type of man runs, as
has been seen, more to the purely silicotic or non-infective type,
and evidence of infection is in such cases typically a late phenomenon. The " phthinoid " type of man, on the other hand,
tends rather to the infective type from the outset. Between these
extremes, however, there is a large number of intermediate cases
which incline some to the one side, some to the other, in physical
or in radiographic type.
If, however, one makes allowance for these variations in the
disease, it is possible to divide the cases of " simple silicosis "
which one meets with into three broad groups — the " slight "
and " moderate " cases, the " well-marked " cases, and the " very
well-marked " or " advanced " cases. As is to be expected in a
disease which is in most instances progressive, these " stages "
merge successively into one another. Nevertheless, the bulk of
the cases in each group exhibit, on the average, a general correspondence in pathological condition and radiographic appearances
and in the complex of signs and symptoms and degree of disability
which they present.

PATHOLOGY, RADIOLOGY AND SYMPTOMATOLOGY

271

We have seen in the preceding paper that, from the practical
standpoint of effect upon respiratory function, the appearance of
an appreciable or " slight " degree of silicosis may be taken to
coincide in general with the development of some amount of
visible and palpable fibrosis in the shape of a sparse " small "
miliary nodulation under the pleurae and in the lung substance.
This is the standard of pathological diagnosis which experience
has led the Medical Bureau to adopt, and it is in this sense that
the term " slight degree of silicosis " is used in the present paper.
We have seen also that, as a consequence of its mode of origin,
a developed silicosis is typically a more or less " generalised "
condition. This is an important diagnostic point, inasmuch as this
feature of " generalisation " characterises alike the pathological
changes, the radiographic appearances and the clinical signs of
silicosis in each of its stages. Although there are exceptions in
some cases of predominantly infective type, in which the lesions
may be more localised and the physical signs may be correspondingly
altered, the statement just made is generally applicable.
The recognition of a developed case of silicosis usually presents
no difficulty. One has already called attention to the symmetrical
" mottling " of the lung fields, with small and typically discrete
shadows, which characterises the radiograph of an established case
of what we may term a " moderate degree " of silicosis. One calls
this appearance " specific ", and this kind of " mottling ", dependent upon the presence of miliary nodulation, is the only specific
radiographic sign of silicosis.
In the film shown (film 9) this appearance is quite obvious,
and it becomes more obvious still in later " stages " of the disease.
Difficulty in the matter of diagnosis can hardly arise in such
established cases. The sole difficulty is naturally with cases which
have not yet reached this stage of development. The question
we have to answer is : " At what point can we say that the ' earliest
detectable ' clinical and radiographic signs of a ' slight ' but
appreciable degree of silicosis, in the sense above defined, are
present ? "
We have said that a radiograph of high technical quality, properly
interpreted, provides the most reliable single diagnostic criterion
of silicosis. It may be convenient, therefore, to begin this part
of our discussion by describing the indications of the presence
of pulmonary " fibrosis ", as shown by the radiograph, up to the
point at which these indications afford definite evidence of the
existence of an appreciable degree of silicosis.

272

PAPERS PRESENTED TO THE CONFERENCE

T H E ROUTINE RADIOLOGICAL PRACTICE AT THE MEDICAL BUREAU

The number of persons who have to undergo radiological
examination at the Medical Bureau during the forenoon of each
day averages about 120. For this reason alone the examination
made is practically entirely solely a radiographic one — radioscopy
is not employed as a routine method, although one fully recognises
its supplementary value in detailed individual examination.
The X-ray plant used is a " Polydor ", with four-valve tube
rectification of the high-tension current. Its capacity is from
35 K.V. effective to 115 K.V. effective; the output is 250 M.A.
The tubes used are line focus tubes, the " Philips' Metallix "
fine focus, and the Siemens' " Phoenix Radion " medium focus,
both with water-cooled anode.
The tube setting is 40 K.V. effective, with 3.8 A. heating current,
giving an output of 50 M.A. Focal distance, 29 inches. Exposure,
1
/io"3/s second for patient with average depth of chest. Films "Kodak
contrast ". Intensifying screens are used at present on both sides
of the film.
The Bureau's radiologist (Dr. W. Steuart) is at present investigating in Europe whether the installations using high capacity
tubes, with long focal distance, recently introduced there, would
prove suitable for the work of the Bureau.
TERMINOLOGY ADOPTED BY THE BUREAU TO DESCRIBE THE VARIOUS
T Y P E S OF RADIOGRAPH

In order to secure consistency in the description of the large
number of radiographs with which it has to deal daily, the Medical
Bureau has found it necessary to create a private conventional
terminology, descriptive of the various general grades of radiographic appearances indicative of pulmonary " fibrosis ". The
Bureau's radiologist, in reporting upon negatives, first classifies
them into one of the following eight groups:
1.
2.
3.
4.
5.
6.
7.
8.

" Normal Thorax " (N.T.).
" Rather more Fibrosis than usual " (R.M.F.U.).
" More Fibrosis than usual " (M.F.U.).
" Commencing generalised Fibrosis " (C.G.F.).
" Moderate generalised Fibrosis " (M.G.F.).
" Well-marked Fibrosis " (W.M.F.).
" Very well-marked Fibrosis " (V.W.M.F.).
" Gross Fibrosis " (G.F.).

PATHOLOGY, RADIOLOGY AND SYMPTOMATOLOGY

273

The term " fibrosis " is here used to indicate merely the amount
of fibrous tissue in the lung, as indicated by the radiograph, whether
t h a t amount be within the normal limits, as in the first two or three
classes, or be abnormal, as in the others. Each general group,
except the first, contains two or more subdivisions; e.g. a " Wellmarked Fibrosis " may be " mainly silicotic " or " partly (or mainly)
infective in type ", and the particular variety present is also specified
in the radiologist's report.
Further, each grade may be
accompanied b y appearances indicative of special conditions,
such as " suggestive of tuberculosis ", " apparently definite
tuberculosis ", " pleural effusion ", " empyema ", " pneumonia ",
" enlarged heart ", " aortic aneurism ", " pericarditis ", etc.
These also are noted, if present.
The report on any individual case is made very simple by the
radiologist merely initialling the relevant description upon a
stereotyped form. A specimen form is attached as Appendix " A " 1
and the radiographic appearances therein reported upon are seen
to be a " moderate degree of fibrosis, silicotic in type, with
apparently definite tuberculosis left lung ". In this manner a
hundred radiographs can easily be reported upon in much less than
as many minutes.
The terms used to describe varieties of " fibrosis " are quite
arbitrary and conventional, but an attempt has been made to
relate them to the radiographic appearances actually shown, and
to the pathological conditions indicated by these. The terminology
is employed merely as a means of rapidly placing any particular
negative in its appropriate approximate " bin ". Presumably all
radiologists use an analogous private code, and the Bureau does not
claim any particular value for the terminology which it employs,
other than t h a t of the practical convenience of securing a working
uniformity of description. The precise meaning of the terms used
is explained below, but for convenience of reference we append
here a schematic statement which may render their general
significance and relations more apparent.
The above scheme shows in tabular form the general classification
of radiographic appearances adopted by the Bureau. To any
one of these may be added, if the relevant indications are present,
such particular additions as:
" Pleural thickening " or " pleural effusion ".
" Hilus thickening " or " peribronchial thickening ".
1

P a g e 294.
18

274

PAPERS PRESENTED TO THE CONFERENCE

TABLE I. —

NOMENCLATURE OF TYPES OF RADIOGRAPH

EMPLOYED

BY MINERS' PHTHISIS MEDICAL BUREAU

Subdivisions
General group

(a)

(f>)

(c)

Simple

Partly or mainly
Silicotic in type
(p. or m. Sil.)

Partly or mainly
Infective in type
(p. or m. Inf.)

1. N.T.
Normal
Thorax

Normal shadows

2. R.M.F.U.

Simple
(slight increase
of fibrosis in
normal
situations)

Rather
more
Fibrosis
than usual

p. or m. Inf.
(as in (a), with
indications of old
or inactive infective element)

3. M.F.U.
More Fibrosis
than usual

(Further increase
of fibrosis in
normal
situations ; " large
branch fibrosis")

4. C.G.F.
Commencing
generalised
Fibrosis

Simple
partly Silicotic
p. or m. Inf.
(generalised fine
in type
(as in (a), with
(as in (a), with indications of inarborisation
throughout both partial " small " fective element
specific mottling) not
definitely
lung fields;
active)
" small branch
fibrosis " ; " the
leafless tree ")

5. M.G.F.
Moderate
generalised
Fibrosis

Simple
(as above, but
more marked)

Silicotic in type
p. Inf.
(as in (a) or (b),
(symmetrical
"small" mottling with indications
throughout both of infective element not
lung fields)
definitely active)

6. W.M.F.
Well-marked
Fibrosis

(Symmetrical
" medium "
mottling)

7. V.W.M.F.
Very
well-marked
Fibrosis

(Symmetrical
"large "
mottling)

8. G.F.
Gross Fibrosis

(Gross mottling)

(as in (è), with
indications of infective element
not
definitely
active)

If the radiograph
shows
indications of
active Tuberculous infection,
substitute for
Group 1, or add
to any of the
other groups,
" Suggestive of
Tuberculosis ",
or
" Apparently
definite
Tuberculosis "

PATHOLOGY, RADIOLOGY AND SYMPTOMATOLOGY

"
"
"
"

275

Consolidation " not regarded as tuberculous, e.g. from pneumonia.
Heart enlarged " or " heart asthenic in type ".
Aorta enlarged " or " aortic aneurysm ".
Other changes, e.g. " ? neoplasm ", " ? hydatid ", etc.

The term " fibrosis " is here used merely to indicate the amount
of fibrous tissue in the lungs, as shown by the radiograph. The
increase in " fibrosis " indicated in Groups 2(a) and 3(a) is within
limits which are not in general of pathological significance. The
increase indicated in Group 4(a) is of pathological significance, but
is not necessarily of silicotic origin ; the same is true of Group 4(c).
Group 4(¿>) is specifically indicative of a " slight " degree of
clinically simple silicosis; Group b(b) of a " m o d e r a t e " degree.
Groups 6(b), 1(b) and 8(¿>) indicate, respectively, a " well-marked "
and finally a " gross " degree of clinically simple silicosis.
RADIOGRAPHIC APPEARANCES IN MINOR DEGREES OF " FIBROSIS "

This being premised, one may proceed to indicate the precise
meaning of the terms used and their application to diagnosis. The
type described as " Normal Thorax " (N.T., film 1) ought perhaps
to be described as the " ideal " normal thorax. It is present in
only a minority of adult males of working age.
The type described as " Rather More Fibrosis than Usual "
(R.M.F.U., film 2) shows, as compared with the former type, a
slight increase of fibrosis in normal situations. The difference is
not in general of pathological significance; indeed this type of plate
is probably the most common amongst healthy adult males of
working age. It shows the heart shadow of the normal shape; the
hilus shadows are of normal density and extent; and radiating from
these are the branching shadows thrown by the larger bronchi and
blood vessels, which'extend some distance into the lung fields.
Between and beyond these shadows the lung fields are clear. Even
in " normal " radiographs taken from perfectly healthy persons
there may be found a few sharply defined bright spots in the lung
fields and a similar appearance in one or two of the root glands,
indicative of an old healed " primary " tuberculous infection in
early life, which has left no other trace.
The next type of film is that termed by the Bureau's radiologist
"More Fibrosis that U s u a l " (M.F.U., film 4).
It shows an
advance on the previous type in the form of an increase in the
number and extent of the branching shadows spreading from the
hilar areas. These are now more numerous, and may generally

276

PAPERS PRESENTED TO THE CONFERENCE

be traced almost to the periphery of the lung. They remain,
however, dendritic or linear in form. The hilus shadows are rather
more obvious; the heart shadow remains normal in shape. The
condition represents a further increase in fibrous tissue in normal
situations. It may be described as a " large branch fibrosis ", the
shadows shown in the lung fields being for the most part thrown by
the larger branches of the bronchial or vascular trees. This type
of film is not necessarily, or even as a rule, of pathological significance. It is seen in about 25 per cent, of all initial examinees, and
in well over 50 per cent, of those of forty-five years or over, since
there is, as life advances, a normal increase in the fibrous tissue
of the lung framework. This type of radiograph is frequently seen
in cases of chronic bronchitis and bronchial asthma and chronic
valvular disease of the heart, and is common, together with other
signs, in cases of " old healed tuberculosis ". As is to be expected,
it is more common in miners, age for age, than in those who have
not been underground; but pathological evidence shows that it is
not in itself indicative of silicosis.
MINOR DEGREES OF " FIBROSIS " OF INFECTIVE TYPE

Running parallel to the two simple types of radiograph just
described, there are two other types (films 3 and 5) which, although
similar in most respects, nevertheless show certain definite
differences. They show respectively practically the same amount
of fibrosis as in the " rather more fibrosis than usual ", or " more
fibrosis than usual " types which we have discussed. But in each
case the evidence of fibrosis is now accompanied by features which
distinguish these films rather sharply from the former ones, inasmuch as in each the fibrosis is associated with signs indicative or
suggestive of a limited amount of former tuberculous infection of hilar
or peribronchial type. It is associated with a change in the shape
of the heart to the narrowed, elongated, " asthenic " or " vertical "
form, and with a definite or marked increase in the hilus and
bronchial shadows, indicative of glandular enlargement and
peribronchial fibrosis of infective origin. Denser shadows cast by
markedly fibrosed or calcareous lesions may be apparent at or near
the hilus region, or here and there in the lung fields. Clinically,
individuals who show this type of radiograph may be quite healthy
and fit for ordinary work, but they are not in general of robust
physique. They are almost always under weight, sometimes
markedly so, with a flat or flattish chest, a defective posture,

PATHOLOGY, RADIOLOGY AND SYMPTOMATOLOGY

277

sometimes with " winged " scapulae, and they usually are somewhat
languid-eyed or " deep-eyed ". They have, in short, as a rule the
characteristic physical stigmata of the " phthinoid " type of
individual, associated with radiographic indications of an old
" healed " pulmonary infection. The Medical Bureau therefore
labels this type of radiograph " Rather More Fibrosis than Usual,
partly Infective in type " (R.M.F.U. p. Inf., film 3), or " More
Fibrosis than Usual, partly Infective in type " (M.F.U., p. Inf.,
film 4).
Those who are familiar with the radiographs shown by cases of
simple tuberculosis will at once recognise these varieties.
It is remarkable how close the correlation between the radiograph
and the clinical condition generally is in this group of cases. Cases
of this class are never passed for underground work by the Bureau.
But there is no difficulty in obtaining representative films of each
of these varieties in persons who have never worked underground;
indeed; some 4 per cent, of the average " healthy " males of working
age, who present themselves as possible recruits for mining, have
radiographs actually or approximately of one or other of the types
shown in films 3 and 5. Films of this character are not in general
indicative of silicosis; they are generally speaking indicative of an
old tuberculous infection.
" COMMENCING GENERALISED FIBROSIS "

Silicosis, as we have said, is a generalised condition, and the
earliest type of radiograph which gives indication of a commencing
generalised increase of fibrous tissue in the lung is that indicated by
the next group of films, which are termed " Commencing Generalised Fibrosis " (C.G.F., films 6, 7 and 8). In the Bureau's
terminology there are three varieties of this group: 1. "Simple
Commencing Generalised Fibrosis" (film 6); 2. "Commencing
Generalised Fibrosis, partly Silicotic in t y p e " (film 7); and 3.
" Commencing Generalised Fibrosis, partly Infective in type "
(film 8). The terms may seem cumbrous, but they represent
definite distinctions.
The feature common to them all is the appearance of a well-marked
generalised fine " arborisation " in the lung fields. The radiograph
shows an advance on the previous type (M.F.U., film 4) in the
appearance of additional finer dendritic or reticular shadows cast
by the smaller air tubes or blood vessels and apparent more or less
generally throughout the lung fields.

278

PAPERS PRESENTED TO THE CONFERENCE

In the variety termed " Simple Commencing Generalised Fibrosis"
(S.G.G.F., film 6) the description just given is all that is apparent.
The heart shadow is normal ; the hilar shadows are increased ;
the lung fields show the generalised arborisation which we have
described. The appearances suggest the branching of a leafless tree
in which the smallest branches have now become apparent. There is
no evidence, however, of any definite amount of specific silicotic
" mottling ". The appearance described cannot be regarded as
being unequivocally " specific " of silicosis. Similar indications
may be given by other conditions, by peribronchial tuberculosis
(to which we shall refer in a moment), by chronic bronchitis not
associated with special exposure to dust, possibly by pulmonary
syphilis, and may be found in some cases of chronic cardiac or
cardio-vascular disease. It is sometimes seen in coal miners who
arrive from overseas to apply for work in the gold mines, and does
not appear in them to lead to anything more serious or to be
accompanied by any incapacity. It begins to be evident in a small
percentage of our miners who have worked about ten years or so
underground, and is found in them to correspond in general to the
condition of fine thickening of the branches of the bronchial and
vascular trees, unassociated with palpable fibrosis, which was
described in the previous paper, as preceding the development of
a definite condition of silicosis. It was there suggested that this
characteristic appearance was probably in large measure dependent
upon changes in the bronchial tree induced by bronchitis and
bronchiolitis. Pathological investigation shows that, in a majority
of instances, the lungs of individuals who have shown this appearance in radiographs taken during life do now exhibit definite evidence
of silicosis post-mortem. This particular type of film therefore
cannot be taken as affording a general standard diagnostic of the
presence of silicosis. On the other hand, in a minority of cases, a
" slight " degree of silicosis has been found post-mortem in individuals whose chests during life had shown a simple fibrosis of
this type.
THE

EARLIEST

" SPECIFIC " RADIOGRAPHIC INDICATIONS
OF SILICOSIS

The second variety of the group of radiographs we are discussing
is termed " Commencing Generalised Fibrosis, partly Silicotic in
type " (C.G.F., p. Sii., film 7). The general background of
" arborisation " is the same as in the radiograph last described.

PATHOLOGY. RADIOLOGY AND SYMPTOMATOLOGY

279

But in some areas here and there, commonly first towards the
upper poles of one or both lungs, local evidence of specific " mottling "
is beginning to appear. The leafless tree is beginning to put on
leaves. Pathological evidence shows that in practically all instances
this appearance in the radiograph represents the sparse beginnings
of palpable miliary nodulation, which marks the development of
a " slight " degree of silicosis. The clinical signs will be found also
to correspond, and the conjunction clinches the diagnosis.
In all cases in which the appearance described is found to develop
in a miner, or is present in a claimant whose industrial history
includes a period of several years' work underground, a diagnosis
of silicosis may safely be made. The Medical Bureau, accordingly,
accepts a radiograph of this type as the general radiographic standard
of diagnosis of the " earliest detectable " stage of simple silicosis.
It is the earliest type of film which gives unequivocal specific evidence
of the disease.
In practice, however, the Bureau is accustomed to allow a
certain degree of latitude in the application of this general standard,
inasmuch as pathological evidence shows, as we have said, that a
slight degree of silicosis may sometimes be found after death in
individuals whose chests during life had shown the appearance
merely of a simple " commencing generalised fibrosis ". If these
appearances develop under observation in a miner during the course
of underground work and are accompanied by a coincident development of definite clinical evidence of pulmonary fibrosis, and of some
respiratory disability not attributable to other causes, a diagnosis
of a " slight " degree of silicosis may be made. The possible
presence of bronchitis and bronchiolitis is of importance in this
respect. But in such cases the confirmatory clinical evidance must
be unmistakable, and the occupational history convincing.
The same qualification applies to the evidence afforded by the
third type of film of this group, named " Commencing Generalised
Fibrosis, partly Infective in type " (film 8, with which we may
associate film 10). These films are similar in general character
to those already referred to (films 3 and 5) as illustrating minor
degrees of " fibrosis " of infective type, but they show a more
extensive condition of " fibrosis ". Like these they are indicative
in general of an old tuberculous infection. They resemble the
type of film shown in cases of a limited degree of simple apical
fibroid tuberculosis. Indeed, beyond one or two enlarged and
fibrosed root glands and a possible old pleural scar and a few
cretaceous or fibroid nodules at the apices or elsewhere, there is

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CONFERENCE

usually very little macroscopic change detectable post-mortem
in lungs which have shown appearances of this sort during life.
Radiographs of this type may be met with amongst individuals
who have never been underground at all. But they are certainly
commoner amongst miners who have spent a good many years
underground than amongst non-miners. Such appearances may
be accompanied by no deterioration of general health or respiratory
function in the individuals concerned. Nevertheless, a certain
proportion of cases of the type, represented by films 8 and 10,
occurring in miners, have been found, post-mortem, to show evidence
of a slight degree of slowly progressive tubérculo-silicosis. This
takes the form usually of one or two circumscribed areas of tuberculo-silicotic consolidation at or towards one or both apices, with a
scattering of smaller nodules in the neighbourhood, with thickening
and perhaps adhesion of the overlying pleura, and with similar
tuberculo-silicotic changes in the corresponding root glands. If
these lesions are enough to " matter " they will, with practical
certainty, be indicated in a good radiograph. But there is no
generalised silicosis. One is here dealing with a slight localised
degree of tubérculo-silicosis. Persons showing this condition are
usually spare and not robust, and incline to the " phthinoid "
type of chest.
It is accordingly the practice of the Medical Bureau that, when
a radiograph of this infective type of " Commencing Generalised
Fibrosis " (film No. 9), with indications of localised apical change,
is found to have developed during the course of his employment
in a miner who, although showing no signs of active infection,
presents evidence of some progressive deterioration in general
condition and respiratory function, together with physical signs
of pulmonary fibrosis, to certify the presence of a slight degree of
tubérculo-silicosis. Such a condition is the characteristic expression
of a limited tuberculous infection in a person exposed to the
inhalation of dust in moderate amounts.
One hopes that what has so far been said regarding the diagnosis
of the " earliest detectable stages " of silicosis has not left a sense
of indefiniteness. The position amounts to this. The general
diagnostic standard is the film, which shows the first indications
of specific " mottling " (film No. 7), and a considerable majority
of the cases notified fall into this group. But pathological evidence
indicates that we are justified in extending our basis of selection to
include a certain number of cases whose radiographs are of the
" simple " or " infective " varieties of " simple generalised fibrosis ",

PATHOLOGY, RADIOLOGY AND SYMPTOMATOLOGY

281

provided that we have ample support from the clinical side and from
the industrial history in so doing. That is the position which
corresponds to the facts of the case. But this situation suggests
all the more the desirability of placing all decisions which may
lead to awards under a system of compensation in the hands of a
specially selected body of whole-time examiners, whose expert
experience of all aspects of the question will enable them to give
an impartial decision.
T H E CLINICAL SIGNS IN A " SLIGHT " OR " MODERATE "
OF

" SIMPLE SILICOSIS "

DEGREE

One may now consider the nature of the clinical signs which are
usually present at the " earliest detectable " stage of silicosis.
It will readily be understood that, in a condition whose pathological beginnings are fine and generalised, and whose development
is extremely gradual, the symptoms will be correspondingly insidious
in their onset and more elusive in character than is the case with
most other lung diseases. This is certainly so, and constitutes
the unquestionable and unavoidable difficulty in diagnosing the
disease by ordinary clinical methods in its earliest stage.
The usual symptoms of silicosis in its " earliest detectable stage "
are slight shortness of breath on exertion, with some amount of
irritative cough, typically a dry cough with little or no expectoration, often worst in the morning and sometimes inducing vomiting.
There may also be some complaint of occasional slight pains in the
chest. Even these symptoms may be absent, and, in not a few
cases, miners, when notified that they have contracted a " slight "
degree of silicosis, may be unaware that there is anything the
matter with them. Further, these symptoms in themselves are
not peculiar to silicosis, and in no case is the Medical Bureau
influenced in its decision solely by such subjective evidence. In
general one may state that at this stage respiratory disability
is, at the most, slight, and it may be altogether absent.
To come now to physical signs. In the earliest stage of a " simple
silicosis " there is no departure from the normal standard of nutrition, except in individuals of an originally poor physique. Loss
1
The succeeding portions of the present paper are based, with however
a considerable amount of expansion and modification, upon an account of
" The Diagnosis of Silicosis and Tuberculosis in the practice of the Medical

Bureau ", prepared by one of us (L. G. IRVINE) in conjunction with
Dr. J. M. SMITH, and published in The Proceedings of the Transvaal Mine

Medical Officers' Association, Vol. I, No. 6, Sept. 1921.

282

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of weight, which occurs coincidently with the development of signs
of silicosis, and which cannot be attributed to other causes, definitely
suggests an infective element in the case.
The conformation of the chest usually shows little or no alteration,
although the upper chest may show some flattening. The percussion note is typically of average normal quality. The practically
constant clinical signs are:
1. A certain lack of elasticity of the chest wall during the movements
of respiration, together with
2. A somewhat reduced air entry, and
3. A characteristic alteration of the inspiratory murmur from the
normal " vesicular " character to a higher-pitched or " harshened ",
" thinned " and commonly somewhat shortened type, the expiratory
murmur, although somewhat prolonged, remaining fainter than the
inspiratory.
This type of breath-sound is very characteristic, with some
modifications, of silicosis in all its stages, and this clinical sign
has also the significant character of more or less complete generalisation. It is first noticeable at the anterior, lateral and basal regions.
In a minority of cases, however, the breath-sounds may be
simply diminished, but breath-sounds which are simply diminished
or which, on the other hand, are merely somewhat louder or more
" pronounced " than normal, are not specially characteristic of
silicosis.
Usually there are no accompaniments, but a stray rhonchus
may be heard here and there.
This complex of physical signs is almost constantly present in
cases of a slight degree of " simple " silicosis. The cough may be
put down to the coincident bronchitis and bronchiolitis, the recurrent pains to slight intercurrent local pleurisies.
The clinical condition is not much more marked in each of its
components in cases of a " moderate " degree. The radiographic
appearance of the latter condition is, however, now quite distinctive.
It is that described by the Bureau as a " Moderate Generalised
Fibrosis, Silicotic in type " (M.G.F. Sii., film No. 9), to which
we have already referred. The partial indications of the specific
" mottling " shown in film No. 7 are replaced by a symmetrical
and practically uniform distribution of this appearance over the
whole of both lung fields. The latter are seen to be occupied
practically throughout by numerous small discrete shadows cast
by individual nodules or (in part) b y slightly thickened air tubes
or blood vessels caught " end on ". We are here obviously dealing

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283

with an established condition of silicosis, and its radiographic
appearance is now unmistakable. It is simulated by no other
condition, except by some cases of acute miliary pulmonary
tuberculosis. In the latter, however, although the distribution
of the small discrete shadows is practically identical, the individual
shadows are less well defined, and clinically the differential diagnosis
should present no difficulty.
Individuals who show the " infective " type of " slight " or
" moderate " silicosis are most often of " phthinoid " conformation
and aspect, and, apart from these characters, the physical and
radiographic signs may be more marked at the apical regions of
the lungs.
CLINICAL

AND

RADIOGRAPHIC

SIGNS

" WELL-MARKED "

DEGREE OF " SIMPLE SILICOSIS "

The description of the later stages of silicosis need not occupy
us long. In cases which have passed from the earlier stage of a
" moderate " to that of a definitely established " well-marked "
degree of simple silicosis the radiographic and clinical signs are
very distinctive.
The radiographic appearances are those shown in the type of
film termed " Well-marked Fibrosis of Silicotic type " (W.M.F. Sil.,
film No. 11). This exhibits the characteristic " mottling " in
a more marked degree. The individual shadows are larger, although
they may not be more numerous. They are of a fairly well defined,
rounded or sometimes annular form, generally discrete, but sometimes, in places, merging somewhat into one another. The heart
remains of good shape. This is the characteristic picture.
If, on the other hand, the " mottled " shadows are irregular
in shape, size and distribution, and are accompanied by a change
in the heart shadow towards the vertical type, the presence of an
infective element, which is commonly tuberculous, may usually
be assumed, although there may be no clinical indications of active
pulmonary infection. Compare in this respect film 11 with
film 12.
In a fair proportion of cases another and very striking change
may be manifest, namely, that many or most of the individual
shadows may be seen (in the negative) to be abnormally bright
and sharp, owing to an increased density of the individual nodules
(film 17). Pathological evidence has confirmed the view which
had previously been taken by the Bureau that this remarkable

284

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and suggestive feature is due to calcareous deposit occurring in
the nodules, and this change may extend to the great majority.
No microtome will touch them.
Finally, one may add t h a t a coarsely " mottled " appearance
may be seen also in some cases of simple broncho-pneumonic
tuberculosis. But in these the appearance is rarely generalised
throughout both lungs, the shadows of " mottling " are less sharply
defined and may commonly be seen to merge into a more diffuse
opacity at the apex or round the hilus.
The clinical signs in the intermediate or " well-marked
stage of simple silicosis show a corresponding advance upon those
of the earlier stages. They now present a characteristic complex.
In a case of average or of robust type the man is usually quite
well nourished, and indeed is not at all infrequently well above
the normal weight. The upper chest is typically somewhat —
but " smoothly " — flattened or " sloping " but is not markedly
retracted, as in chronic tuberculosis (cf. fig. 12). The character
of the chest movement is modified, as much, however, by an
alteration in the quality of the movement, which is sluggish and
lacking in elasticity, as by a mere reduction of the range of movement, although some amount of reduction is the rule.
The percussion note, without being definitely " dull ", is usually
somewhat flattened, particularly posteriorly.
The air entry is somewhat shortened and thinned. The breath
sounds are also typically somewhat shortened and present almost
constantly and more definitely the characteristic thinning and
harshening of inspiration, together with a prolonged but fainter
expiration, already described, although in a small minority of
cases, at this stage also, the breath sounds are simply " diminished
vesicular " in character.
The silicotic chest, in the absence of complication due to infection,
is typically a " dry " chest, although sometimes fine crepitations,
due to congestion, may be heard towards the lateral and basal
margins, or a few rhonchi may be heard here and there. Cough too,
if complained of, is usually " dry " and irritative, often of the
morning " emetic " type.
In the cases which we see nowadays cardiac dilatation, except
when dependent on intrinsic disease of the heart, is quite exceptional
a t this stage of silicosis.
Cases of silicosis in the intermediate stage are usually fit for
" moderate " physical work; indeed, a number of cases who show
the radiographic signs of a well-marked silicosis may lead a full,

PATHOLOGY, RADIOLOGY AND SYMPTOMATOLOGY

285

active life, without obvious interference with respiratory function.
But in an average case there is an amount of dyspnoea on exertion
which definitely impairs the working capacity.
Simple silicosis of the " classical " type is not typically a wasting
disease. As we have said, even in well-marked cases the general
condition and appearance may be quite good, and there is actually
in a number of cases a tendency to gain weight coincidently with
the onset of detectable evidence of the disease. In others, however,
there is loss of weight, and this is more common in those whose
radiographs are of the " infective " type which I have described,
circumstances that suggest the presence in such cases of an element
of latent infection.
THE ADVANCED STAGE OF " SIMPLE SILICOSIS "

Twenty years ago it was common enough to meet with advanced
cases of " simple " silicosis which were not obviously of an infective
type. To-day one meets with cases which can fairly be described
as such, generally speaking only in men of originally robust physique.
A characteristic example is shown in fig. 11, already referred to.
The radiographic signs in such cases are those of a medium or
large, close mottling, and the shadows may be seen here and there
to have coalesced, giving the appearance of limited areas of more
diffuse opacity (films 13 and 15). If the shadows show much
lack of definition and are unduly large or irregular in size, with
a definite tendency to local coalescence, it is probable that an
infective element is present in the case (films 14 and 16). Indeed,
the first radiographic indication of the supervention of an active
tuberculosis is frequently the occurrence of a blurring of the outline
of the " mottled " shadows which, in previous radiographs taken
in the same case, may have been well defined.
Few cases of advanced silicosis are without some infective element,
although this may be latent and not apparent clinically.
In advanced cases of the " classical " type (films 13 and 15)
the clinical signs are very pronounced. The general nutrition may
be quite good ; many cases indeed are somewhat obese. There are,
with few exceptions, some cyanosis and some obvious dyspnoea;
in some the expression may be rather " anxious ". The chest
is smoothly flattened, without however showing marked retraction.
The intercostal and supraclavicular spaces may show no obvious
hollowing. The configuration resembles that of a moderate
emphysema, and a greater or less amount of emphysema is a

286

PAPERS PRESENTED TO THE CONFERENCE

constant feature of the condition (cf. fig. 11). Expansion is
decidedly impaired, both qualitatively and quantitatively, and the
range of movement is decidedly limited. The percussion note is
flat, without being absolutely dull, although there may be local
areas of dullness due to thickened pleura. To the percussing finger
the normal resilience of the chest wall is impaired. The vocal
resonance may be generally increased, but frequently it lacks
" ring ", and so too may the voice. The air entry is decidedly
reduced and short. The. respiratory murmur is short and highpitched, sometimes thin, sometimes rather blowing, although it
may (but much less usually) be merely much reduced and faint.
The condition of the pleurae may to a large extent account for
these differences. There may be signs of localised consolidation,
but these, if extensive, point to an infective complication.
As we have said, it was formerly not uncommon for cases of
advanced silicosis to die from a progressive heart failure, with
cardiac dilatation, cyanosis and dropsy. But death by progressive
heart failure occurs very rarely nowadays, since few cases now
exhibit the excessive degree of fibrosis which determined that mode
of death. A definite cardiac dilatation secondary to silicosis is
relatively uncommon in the cases we meet with at present, although
some amount of fine crepitation, due to congestion, is very frequently present towards the lateral and basal margins of the lungs.
Nor is there any evidence in our cases of a higher proportion of
instances of disordered renal function amongst silicotic than amongst
non-silicotic miners.
To-day cases such as we have just described are uncommon.
The greater number of advanced cases of " miners' phthisis "
are nowadays cases of " tuberculosis with silicosis " ; and the
majority of the remainder, who have so far escaped an active
breakdown, and for that reason are still classed as " simple silicosis ", nevertheless show clinical and radiographic indications of
the presence of a latent infective element. (Gf. films 14 and 16.)
Gases of advanced silicosis are in general fit for light work only,
or for no physical work whatever, although even at this stage
some may be able to lead a moderately active life.
FUNCTIONAL TESTS IN GASES OF

" SIMPLE SILICOSIS "

A preliminary series of functional tests was carried out at the
Bureau both upon miners and non-miners by Mr.. J. H. Dowds,
of the Witwatersrand University, in 1924; and a further and more

PATHOLOGY, RADIOLOGY AND SYMPTOMATOLOGY

287

extended series of similar observations was conducted by him at
the beginning of the present year, in order to obtain an approximate
measure of several of the clinical features found in silicosis, and in
order to determine the possible value of such tests in diagnosis.
Observations were made upon 500 cases, which were divided
into five groups, each represented by 100 individuals. The groups
chosen for observation were:
1. " First Periodicals " i.e. men who had been underground for not
more than six months and all of whom had passed the " initial " examination of the Bureau as new recruits.
2. " Short-service Miners ", i.e. men working in their fifth, sixth or
seventh years of underground service; all of these men also had passed
the initial examination of the Bureau.
These two groups are therefore comparable with each other,
since all had undergone special selection in respect of their physique
prior to entering on underground work. The observations made
in these 200 cases may be of particular value in the future when
the further history of these men is followed.
3. " Long-service Miners ", i.e. men working in their ele\enth,
twelfth and thirteenth years of underground service. Very few of these
men had passed the initial examination of the Bureau, and they were in
general a group the members of which had not undergone any special
selection. They are therefore not, as a class, comparable with the first
two groups, but they are comparable with the two succeeding groups,
which are also in general composed of men who had not passed the
initial examination of the Bureau.
4. Cases of " Ante-primary " stage silicosis, examined either at the
time of their certification or at their first re-examination thereafter.
5. Cases of " Primary " stage silicosis.
With only one or two exceptions, all of these men had worked
underground solely on the Witwatersrand. Men under twenty or
over fifty years of age were not examined, the latter precaution
was taken in order to exclude persons suffering from simple senile
changes. Very obese men were excluded, also cases of chronic
heart disease, subjects of present or recent illness or recent operation,
and persons suffering from hookworm infection, or those in whom
there was evidence of tuberculosis, or men who obviously were not
trying to execute any of the tests properly. With these exceptions,
the men were taken as they came.
The sequence of the tests, used was: resting respiratory rate,
resting pulse rate, stool-stepping test, chest expansion, vital
capacity, total lung ventilation per minute, blood pressure (silicotics
only) and haemoglobin percentage.

TABLE

II.

—-

AVERAGE

RESULTS

PHYSICAL

MEASUREMENTS

IN CERTAIN GROUPS OF NON-SILICOTIC AND SILICOTIC MINERS
Group I :

100
anteprimary
stage
silicotics

Group V:

Group VI :

100
shortservice
miners

100
longservice
miners

34
170
70.5

38
169
66.5

40
171
70

42
469
66.5

66.5

68.0

68.5

69.5

0. 4m.

6. 7m.

12. 4m.

9. 11m.

93.5

86.7

6.5

5.5

4710

4440

4090

4020

3610

3190

+ 10.7

+ 4.4

—3.2

—6.3

—14.6

—24.9

10790

10680

11340

11440

11720

12690

154

151

170

163

176

189

—0.5
663
2.31

—0.4
603
2.43

+ 0.7
589
2.81

—0.4
583
2.91

539
3.31

+ 1.5
506
4.41

41.3

46.6

59.8

64.1

80.5

121.2

—
—

—
—
*

131
93
38

130
91
39

131
91
40

100
first
periodicals
Age (years)
Height (cm.)
W e i g h t (kg.)
Mean s t a n d a r d weight
(kg.)
Service underground
(years)
R e s p i r a t o r y r a t e (per
minute) :
A t rest, s t a n d i n g
Increase immediately
after exercise
Increase remaining
after pulse r e t u r n ed to normal
Pulse r a t e (per minute) :
A t rest, s t a n d i n g
Maximum
increase
after exercise
Time (seconds) for
r e t u r n to normal
Chest circumference a t
end of normal expiration :
2 ins. above nipple
(cm.)
2 ins. below nipple
(cm.)
Average range of expansion between full
inspiration and full
expiration (cm.)
Actual vital capacity
(cc.)
P e r c e n t a g e deviation
of
vital
capacity
from calculated standard value
Ventilation per m i n u t e
(cc.)
Ditto, per kg. b o d y
weight
Alteration respiratory
r a t e on breathing
through spirometer
Tidal air (cc.)
Ventilation per min.
-r Vital capacity
Resp. r a t e (spirometer)
X Ventilation
per
minute
-r Vital capacity
Percentage haemoglobin
Blood pressure:
Systolic
Diastolic
Pulse pressure

Group I I : Group III : Group IV:

25
170
70

100

primary
stage
silicotics

secondary
stage
silicotics
44
170
67
70.5

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289

Flack's test (respiratory force) was not employed, as its results
in the preliminary series of observations were erratic. An efforttest of stool-stepping (10 times in 30 seconds; height of stool,
20 inches) was employed instead, and the alterations of pulse and
respiration were observed.
The average results are shown in table II.
In the last vertical column a series of observations on ten secondary stage cases has been added; the number is small, but the
results so far as they go are consistent.
These observations show a progressive diminution in chest
expansion in silicotic cases. The vital capacity is also progressively
reduced, but only slightly so in ante-primary stage cases; in primary
stage cases the average reduction is of the order of 15 per cent.;
the resting respiratory rate is increased and the breathing becomes
proportionately shallower.
These results are of interest, but the great variations shown by
individual cases in each group and the element of uncertainty
which might readily be introduced by the subjective factor in such
tests render them of little value in diagnosis. The observations
on the average blood pressure in cases of silicosis are of interest
from their negative result.

" TUBERCULOSIS WITH SILICOSIS "

By the term " Tuberculosis with Silicosis " one means silicosis
complicated by clinically obvious, active or " overt " tuberculosis.
Mere indications from the radiograph or from physical signs .of
limited areas of consolidation do not lead one to place a case in
this class unless there are local or constitutional signs of active
tuberculous infection. Active tuberculosis may be present from
the first appearance of detectable signs of silicosis, but this is
uncommon. It may supervene at any stage in the progress of
what has previously been from the clinical standpoint a condition
of simple silicosis. But it is most common as a terminal complication in well-marked or in advanced cases of the disease.
The diagnostic indications of silicosis complicated by tuberculosis
are that the signs, particularly the radiographic signs, of both
conditions are present.
In the radiograph, in addition to the generalised signs of silicosis
in one or other of its stages, indications of more or less extensive
" blurring " or of more marked local opacities indicative of areas
19

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of definite consolidation appear (see films 19, 20, 21 and 22).
The heart shadow also may show a change to the asthenic or
" vertical " type.
The radiograph is particularly helpful in such mixed conditions,
especially when these are seen for the first time, and it is usually
decisive. It is a common and easy course, when a case of active
tuberculosis is met with in a miner, to assume the presence of a
silicotic element. But such a diagnosis, when made on clinical
grounds alone, is in very many cases merely presumptive. The
only objective proof of such a conjunction during life is the radiograph, which will almost invariably give precise and accurate
indications of the actual condition present. In some instances,
however, the appearances produced in the radiograph by an
extensive bilateral tuberculosis may altogether obscure the distinctive indications of an underlying silicosis. In such cases one is
compelled to fall back on the probabilities of the case, taking into
consideration the previous condition of the individual and the
duration and character of his underground service. The same
observation applies to some old-standing cases of chronic " tubérculo-silicosis ", in which the distribution of the lesions resembles
that of a fibroid tuberculosis, and in which no indications of a
generalised silicosis may be present.
On the clinical side the supervention of active tuberculosis is
shown first usually by a definite and progressive loss of weight,
by the appearance of evidence of localised areas of infection in the
lungs or pleurae, with their characteristic physical signs, by
increased cough and expectoration, sometimes with haemoptysis,
and commonly by a rapid break-down in the patient's condition.
Examination of the sputum for the tubercle bacillus should,
of course, always be made; its presence is a more ominous sign in
tuberculosis complicated by silicosis than in cases of simple tuberculosis. It is a characteristic feature that, when an overt tuberculosis
becomes manifest in a case of well-marked silicosis, the amount
of dyspnoea appears to be quite out of proportion to the actual
extent of the infection. This is one side of the picture. The other
side is that, as we have already said, not a few cases of " tubérculosilicosis ", in which the infective element is less acute, may run
a very chronic course, with a well-marked tendency to retardation
and limitation of the infection (cf. film 18).
In conclusion, an interesting observation may be mentioned,
namely that the onset of a tuberculous infection in a lung in which
no radiographic or clinical signs of silicosis were previously detectable

PATHOLOGY, RADIOLOGY AND SYMPTOMATOLOGY

291

may sometimes bring to light a condition of what Watkins-Pitchford
has termed " latent silicosis " 1 . The infection appears to select
the sites in the lung where minute aggregations of silica are already
present, and thus to assume the characteristic " miliary " distribution of a silicosis. This feature, when it occurs, commonly does
so within a comparatively short time of the appearance of evidence
of infection.

LEGAL

DEFINITIONS

THE

" STAGES "

SILICOSIS

We should have liked to add a few remarks regarding the
differential diagnosis of silicosis, but what has been said is possibly
sufficient to indicate the general features which distinguish t h a t
disease from other pulmonary conditions, and one does not wish to
extend this discussion unduly.
It may, however, be of interest from a practical point of view
to quote in conclusion the definitions of the three legal " stages "
into which, for purposes of compensation, cases of silicosis are
classified under the Miners' Phthisis Act of 1925, of the Union of
South Africa. This will enable one to form an idea as to how t h e
varying types of case which we meet with may be fitted into a
legal system of compensation.
The definitions of silicosis in the Act mentioned (section 76 (2))
are as follows:
2. For the purposes of this Act . . . the expression " silicosis "
shall mean silicosis of the lungs. A person shall, for the purposes of
this Act, be deemed to have or to have had silicosis
(a) in the ante-primary stage, when it is found by the Bureau that the
earliest detectable specific physical signs of silicosis are or have
been present; whether or not capacity for work is or has been
impaired by such silicosis ;
(b) in the primary stage, when it is found by the Bureau that definite
and specific physical signs of silicosis are or have been present,
and that capacity for work is or has been impaired by that disease,
though not seriously and permanently;
(c) in the secondary stage, when it is found by the Bureau that definite
and specific physical signs of silicosis are or have been present,
and that capacity for work is or has been seriously and
permanently impaired by that disease, or when it is found by the
Bureau that tuberculosis with silicosis is or has been present.
i W . W A T K I N S - P I T C H F O R D : " The Silicosis of t h e South African
Mines. " Joum. Indust. Hygiene, Vol. I X , No. 4, p. 113.

Gold

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CONFERENCE

The definition of tuberculosis (section 76 (3) ) reads as follows:
3. For the purposes of this Act . . . " tuberculosis " shall
mean tuberculosis of the lungs or of the respiratory organs. A person
shall, for the purposes of this Act, be deemed to be suffering from
tuberculosis whenever it is found by the Bureau either
(a) that such person is expectorating the tubercle bacillus; or
(b) that such person has closed tuberculosis to such a degree as
seriously to impair his working capacity and render prohibition
of his working underground advisable in the interests of his
health.
It may be noted t h a t the terms " is ", " are ", " has " or " have " •
in the above definitions apply to the cases of living miners ; " has
been " ; " have been " or " have had " to those of deceased miners.
We may add one or two explanatory observations upon these
definitions :
1. It will be noted that cases of tuberculosis do not come within the
provisions of the Miners' Phthisis Act unless they are either " open "
cases or cases which are productive of serious impairment of working
capacity. Minor degrees of " old " healed tubercle or " latent " tubercle
which do not cause serious incapacity are not cases of " tuberculosis "
as defined.
It is recognised that it is very undesirable for any person who is the
subject of active simple tuberculosis to continue to work underground,
alike in his own interest and that of his fellow workmen. All working
miners who are found to have simple tuberculosis are therefore debarred
from further work and are given a " lump sum " award. But this award
is regarded not as compensation for " injury " done, since simple
tuberculosis is not an occupational disease, but as a payment for compulsory loss of employment. A miner can only obtain an award for simple
tuberculosis if the condition is detected while he is at work or within a
year after he has ceased underground work. No such limitation of time
is applied to cases of silicosis or tuberculosis with silicosis.
2. In the system of awards of compensation in respect of silicosis
the gradation in legal " stages " is applied solely to cases of " simple "
silicosis, under which designation are included cases of the " tuberculosilicotic " type which do not present evidence of active infection. The
criteria adopted depend partly upon clinical considerations and partly
upon the degree of incapacitation for work of the affected man. In
the " ante-primary " stage there need be no incapacitation ; the sole
criterion here is the presence of the " earliest detectable specific physical
signs of silicosis ". In the two later stages the physical signs must be
" definite ", but the important consideration is the degree of incapacitation. This bears a general although not an exact relation to the degree
of silicosis present.
In general it may be said that the " ante-primary " stage includes
cases of a " slight " or of a " moderate " degree, as these terms are used
in this paper; the " primary " stage includes " well-marked " cases fit

PATHOLOGY, RADIOLOGY AND SYMPTOMATOLOGY

293

for moderate physical work ; the " secondary " stage includes " advanced "
cases fit for light or no work. The three legal stages thus correspond
closely with the stages of " simple " silicosis as described in this paper.
3. Since the onset of active tuberculosis in a silicotic subject is
generally in itself sufficient to produce a " serious and permanent "
incapacitation, the law prescribes that all cases of tuberculosis with
silicosis shall be classed as being in the " secondary " stage, no matter
what the actual degree of silicosis may be.

294

PAPERS PRESENTED TO THE CONFERENCE

APPENDIX " A '

MINERS' PHTHISIS MEDICAL BUREAU
INITIAL
SPECIAL
PERIODICAL
BENEFITS.

Bureau No

"X "-RAY REPORT

Board

No. .

Name
CHAIRMAN'S NOTES.

Date.

Total Underground
Service
No.

The Skiagraph shows:—
Normal

Thorax.

R a t h e r more Fibrosis t h a n
More Fibrosis t h a n

usual.

Commencing generalised
Moderate generalised

Fibrosis.

Machine drillsCrushers, etc. Mining elsewhere Weight-index
Chest-movement Before exam.Pulse
After
„
Capacity for workRemarks

Fibrosis.

Well-marked Fibrosis.
Very well-marked Fibrosis.
Gross Fibrosis.
Fibrosis, partly /mainly SILICOTIC in type.*
10

Fibrosis partly/mainly INFECTIVE in type.*

Appearances suggestive of TUBERCULOSIS

B GH T
L'E F T

TlTrT'IT

Apparently definite TUBERCULOSIS

Peribronchial thickening.*

Pleural thickening S ^

Pleural effusion ^ E

*JttiM. lung.

Hilus thickening.*

side.

LEFT

Consolidation

BI0HT

side.

LEFT

Heart

asthenic,* vertical* in type.

Heart enlarged.
19

Aorta enlarged.*

O t h e r changes,

Aortic aneurysm.*

viz.
* Delete terms not applicable.

lung.

Claimed —
Confirmed-

Macroscopic Appearances in Silicosis
SIMPLE

SILICOSIS1

Fiu. I. — Moderate
degree of simple silicosis.
The lung shows considerable excess of pigmentation, with moderately
numerous " small " to
"medium" sized palpable
silicotic nodules. (Cf. fig. 7
and film 9.)

>V h

Fie. 2. — Very well-marked
degree of simple silicosis, with
" large " miliary nodulation.
(Cf. Mg. 8 and film 13.)

Figs. 1 to 'i are taken from the lungs of European miners.

Pathology, liadiology and
Syrnpiomalology.
[To face p. 294.]

INFECTIVE SILICOSIS

FIG. 3. — Very well-marked
degree of silicosis, with many
large irregular nodules and some
areas of fibroid consolidation.
No overt tuberculosis.

FIG. 4. — Very extensive
tuberculo-silicotic consolidation,
without
overt
tuberculosis.
There is marked emphysema,
and emphysematous bullae are
visible at the marginal portions
of the diaphragmatic surface of
the lung.

lit

TUBÉRCULO-SILICOSIS IN LUNOS OP NATIVE MINE LABOURERS
These photographs illustrate the more grossly infective type of tubérculosilicosis which is more characteristically seen in certain cases of the disease
occurring amongst native mine labourers.

FIG 4 A. — Very extensive tubérculo-silicosis in lower lobe, with
active tuberculosis. Complete destruction of upper lobe. Lung of a
native mine labourer.

FIG. 4 H. — Very extensive
dense fibroid consolidation of tubereulo-silicotic character, with
tuberculous cavitation in upper
lobe. Lung of a native mine
labourer.

Mierophotographs on Uniform Scale (1 x 9)
(To illustrate the Scale of Lesions in Silicosis)

FIG. 5. — Condition corresponding to most radiographs of " Commencing
Generalised Fibrosis ". There is some excess of pigmentation, with one or
two minute foci of fibro-blastic reaction. Bronchiolitis is present. The lung
is congested.

F'G. 6. —• Slight degree of simple silicosis, with f" small " miliary nödulation. The nodules shown are just palpable; there is no necrosis.

FIG. 7. — " Moderate " degree of simple silicosis. " Small " and
"medium " sized nodules; the composite character of most of the latter is
well seen; none show necrosis. There is some amount of emphysema, and
the lung is congested. (Cf. fig. 1 and film 9.)

FIG. 8. — " Very well-marked " or " advanced." degree of simple silicosis.
The section shows a cluster of " large " nodules of silicotic type. Most are
of composite structure: none show necrosis. (Cf. fig. 2 and film 13.)

FIG. 9. — Tubérculo-silicosis.
nodule, with massive necrosis.

,,^

" Very large " isolated tuberculo-silicotic

•cÄV'i '

i •' ' -•>• •••-•

J -w.v>'ti I-vMr

.. > t ' ' ; ; ^ ? H ^ : ^ ' ' : . ? . i í r ^ i | " ; i .„

//'

¿•S

sc
¿ft;

M)Ä

*• :m few,--

'...-)*

'-V"f

" « ^

•',--•; ;

-•'

FIG. 9 A. — Infective nodules associated with slight degree of silicosis.
The silicotic islets are small and are embedded in limited areas of tuberculous
infection.

Fie. 10. •— Tubérculo-silicosis. Section from an area of massive tuberculosilicotic consolidation. Foci of active tuberculosis are present.

Vili

Physical Types in Silicosis
• THE

ROBUST

TYPE
FIG.

FIG.

II Ji.

FIG. 11 A. — Photograph of case of advanced silicosis in elderly man of
originally robust type. Note the characteristic " semi-emphysematous "
conformation of the chest and the tendency to obesity which is common in
this type of case.
FIG. 11 B. — From a radiograph of his chest. This man is still actively
engaged as a surface mine official. He was first found to have silicosis over
twelve years ago.
FIG.

FIG.

12>.

12 A.

FIG. 12 A. — Photograph of well-marked case of simple silicosis in individual of originally robust type. His radiograph, FIG. 12 B. shows a well
marked silicosis of the " classical " type. This man is still actively engaged
as a senior underground official, and states that he is as well as ever; he plays
golf and goes shooting when on holiday. He was first certified to have
silicosis eight years ago.

THE

PHTHINOID

TYPE
FIG.

13 «.

Fie. 13 A. — Photograph of well-marked case of tubérculo-silicosis in
originally phthinoid type of man.
FIG. 13 B. — A print of his radiograph. It shows bilateral sub-apical
consolidation, the appearances being those of a fibroid phthisis. 'Phe lesions
have remained stationary for at least five years. He is in fair but not good
health, but is still engaged in fruit farming. He was first found to have
silicosis eleven years ago; he was then a highly placed mine official. (Film 18
is also taken from this case.)
F i o . 14 it.

F i o . 14

FIG. 14 A. — Photograph of case of moderate silicosis in an initially
phthinoid type of man.
FIG. 14 B. — A print of his radiograph, which is of infective type. This
man is quite healthy, but short of wind; he is employed as an assistant
storekeeper. He left underground work twenty-one years ago.

Series of Radiographs to Illustrate the Radiology of Silicosis

FILM NO. 1. — Normal Thorax.

FILM No. 2. — Rather More Fibrosis than Usual.

FILM NO. 3. — Rather More Fibrosis than Usual,
partly Infective in type.

FILM NO. 4. — More Fibrosis than Usual.

FILM No. 5. — More Fibrosis than Usual,
partly Infective in type.

FILM NO. 6. — Simple Commencing Generalised Fibrosis.

FILM NO. 7. — Commencing Generalised Fibrosis,
partly Silicotic in type. Characteristic film- of slight degree
of Silicosis.

FILM NO. 8. — Commencing Generalised Fibrosis,
partly Infective in type.

FILM No. 9. — Moderate Generalised Fibrosis, Silicotic in type.
Moderate degree of Silicosis. (Cf. figs. 1 and 7.)

FILM NO. 10. — Moderate Generalised Fibrosis,
partly Infective in type.

FILM NO. 11. — Well-marked Fibrosis, Silicotic in type.
Well-marked degree of Silicosis

FILM NO. 12. — Well-marked Fibrosis,
partly Infective in type.

FILM No. 13. — Very well-marked degree of Fibrosis,
Silicotic in type. Very well-marked Silicosis. (Cf. figs. 2 and 8.)

FILM NO. 14. — Very well-marked degree of Fibrosis,
partly Infective in type.

FILM NO.

15.

— Gross Fibrosis, Silicotic in type.
Advanced Silicosis.

FILM NO. 16. — Gross Fibrosis, partly Infective in type.

FILM NO. 17. — Well-marked Silicosis,
with general Calcareous Deposit in nodules.

FILM No. 18. — Case of very chronic Tuberculo-silicosis.
The lesions shown have remaiaed. stationary for five years.

FILM. NO.

19. — Moderate degree ofSilicosis
with Tuberculosis.

FILM No.

20.

— Well-marked degree of Silicosis
with Tuberculosis.

FILM No. 21. — Very well-marked degree of Silicosis
with Tuberculosis or Tubérculo-silicosis. (Cf. fig. 3.)

FILM NO. 22. — Advanced Silicosis with Tuberculosis,
or Tubérculo-silicosis.

SILICOSIS IN
BY

AUSTRALIA

KEITH R. MOORE, M.B., B.S., D.P.H.,

INDUSTRIAL

HYGIENE,

DIRECTOR, DIVISION

COMMONWEALTH

DEPARTMENT

HEALTH, AUSTRALIA

The rapid increase in the population of Australia which marked
the latter half of last century was due in great part to the discovery
in several parts of the Continent of rich alluvial gold fields. A large
proportion of the migrants of this period came from mining districts
in England and other countries.
The resultant stimulus to prospecting brought about the discovery
of other metalliferous deposits, and to-day many of the Australian
mining fields bear names such as Bendigo, Broken Hill, Kalgoorlie,
which are almost household words.
The conditions under which deep mining was carried out in the
earlier days exacted a heavy toll of lives from those who were
connected with the industry. The advent of modern procedure
involving the use of water in drilling and more meticulous attention
to ventilation, dust prevention and the regulation of blasting has
doubtless resulted in saving many lives. Silicosis has been
demonstrated in many of the mining fields and a high death-rate
from pulmonary diseases, including tuberculosis, has been evidenced
in association with the industry. The following table shows the
increase in mortality from phthisis during the development of the
mining industry in the Bendigo district:
ANNUAL MORTALITY FROM PHTHISIS PER

10,000

OF POPULATION

AMONGST MALES AGED 2 1 AND UPWARDS
Period

Bendigo and district

Victoria

1870-1872
1880-1882
1890-1892
1900-1902
1903-1905

35.33
60.44
77.90
77.36
62.29

22.15
26.89
26.37
23.18
20.81

296

PAPERS PRESENTED TO THE CONFERENCE

The following table shows the mortality in the occupational
group, mining and quarrying, as compared with the average
general mortality during the years 1908-1914. These figures are
taken from a table published by the New South Wales Board-of
Trade in 1919:
Average
number
of mining
employees

State

New South Wales
Victoria
Queensland
South Australia
N o r t h e r n Territory
W e s t e r n Australia
Tasmania
Commonwealth

Average
number
of deaths
per year

Death-rate
per group

Annual
death-rate
per 1,000
population

593
508
282

15.7
31.0
20.7

13.9
27.5
18.5

6,614

12.7

11.2

16,118
5,662
96,058

218
58
1,743

13.5
10.2
18.2

12.0
9.1
16.1

37,715
16,363
13,586
1
J

New South Wales
INVESTIGATIONS

AND

ENQUIRIES

During the reticulation of Sydney with a system of sewers
attention was focussed on the conditions under which the men were
working, and a Sewer Works Ventilation Board was appointed
in 1902 to enquire into the working conditions and to recommend,
where possible, any means of improvement whereby the work
might be rendered less hazardous.
The principal country rock on which Sydney stands is sandstone
containing over 90 per cent, of silica.
The Board found that " for many years past miners employed
on this class of work (tunnelling) suffered acutely from a disease
which was for a long time known by the rather misleading term
' sewer disease ', but as the complaint became more widely
known it was strongly suspected that dust was the chief cause of
the mischief ".
The Board blamed the fumes of explosives and the expired
air from the lungs of the miners in tunnels, imperfectly ventilated,
as causes contributory to the high mortality, but stated that the
dust from hammering, drilling and the use of the pickaxe was
probably the sole cause of the disease once known as " sewer
disease ".
The first recommendation of the Board was the prevention of

SILICOSIS IN AUSTRALIA

297

dust. Next, efficient ventilation was recommended and suitable
change-house accommodation. The work of a sewer miner in
tunnelling sandstone was regarded by the Board as a dangerous
occupation and a day of six hours was recommended for these men.
In 1907 another Committee was appointed in Sydney to enquire
and report on methods of excavation in trenches and tunnels
through sandstone where blasting operations are limited or not
permissible, and as to whether the methods in use might be improved
and made less dangerous to the workers by the use of rock-cutting
or boring machinery. The terms of reference of this Committee
also included an enquiry into rates of pay and hours of work.
The Committee reported that the best method of preventing
diseases from dust would be the introduction of machinery. Six
hours were recommended as a day's work, and it was also recommended that £500 should be made available for experiments with
rock-cutting machinery. Exhaust ventilation was advised in place
of forcing air to the working face.
In 1912 a reported epidemic of pneumonia at Broken Hill was
investigated by Armstrong, who reported that the death-rate
from pneumonia among underground miners in that locality during
1910-1912 was 6.5 per thousand or nearly four times as great as
that for all males in New South Wales. The death rate from
pneumonia for females in Broken Hill was only slightly higher than
that for females in the rest of the State.
In 1914 a Royal Commission was appointed to enquire into the
mining industry at Broken Hill. With regard to industrial diseases,
this Commission stated that pneumonoconiosis and plumbism
were among the risks of a miner's calling, while other diseases—
for example, pneumonia—were added risks of the calling, but not
strictly industrial because they affected others than miners. From
unanimous medical testimony the Commission concluded that
pneumonia was more prevalent, severe and fatal, among miners in
Broken Hill than in any other class in the State. While attributing
sudden changes in temperature as the prime cause, the Commission
advanced the opinion that dust inhalation in any form would
predispose to the disease.
This Commission expressed the opinion that pneumonoconiosis
was practically unknown at Broken Hill and blamed mining in other
States for such cases as had been noted. Tuberculosis was a
disease to which the Broken Hill miners, as elsewhere, were
peculiarly subject, and the presence of tuberculous patients in a
mine was considered particularly dangerous.

298

PAPERS PRESENTED TO THE CONFERENCE

This Commission recommended exclusion from mines of men
suffering from tuberculosis or pneumonoconiosis, medical examination prior to employment, compensation of sufferers from
pneumonoconiosis or tuberculosis, and that the dependants of
the latter should be a charge on the State.
In 1916 a forty-four-hour week was granted by the Commonwealth Court of Conciliation and Arbitration for underground
men at Broken Hill, largely on account of the association between
working conditions and the incidence of pneumonia and tuberculosis.
In 1919 the New South Wales Board of Trade, in response to a
request by the Government, after reviewing the available
information concerning pneumonoconiosis, concluded that, while
there was an undue mortality from pulmonary disease in the case
of stone masons and sandstone quarrymen working on stone
containing free crystalline quartz, there was not sufficient evidence
to form an opinion as to the prevalence of these diseases among
miners, and recommended that a Technical Commission of Enquiry
be constituted to ascertain the actual facts, " using clinical and
radiological means ". As a result of this recommendation, in
December 1919 a Technical Commission was constituted to examine
the miners at Broken Hill. This Commission, for the first time
in Australia, used X-rays as a means of diagnosis of silicosis as an
occupational disease.
In its preliminary report the Commission records the results of
examination of 4,337 mine employees. In 370 of these, the
examinations were incomplete.
Of the total, 193 cases of
pneumonoconiosis were diagnosed, 90 in the first stage, 44 in the
second and, in 59 cases, complicated with tuberculosis. In addition, 39 cases were definitely diagnosed as suffering from pulmonary
tuberculosis only, and in a further 26 it was thought " highly
probable that these persons were suffering from uncomplicated
pulmonary tuberculosis ".
The Commission defined the stages of pneumonoconiosis on
which the diagnoses were founded as follows:
A person in the first stage of the disease shows no impairment of
his working capacity and of his general health. The photographs taken
with the X-rays show the presence of an early fibrosis in the lungs.
A person in the second stage exhibits a more advanced fibrosis in
the X-ray photographs and in some individuals clinical evidence of the
presence of the disease.
In the third form, radiographic and clinical evidence of infection
with tuberculosis is present.
Tubercular infection may supervene in either the first or second stage
of pneumonoconiosis.

SILICOSIS IN AUSTRALIA

299

The Commission found that pneumonoconiosis arises in Broken
Hill as a result of inhalation of dust among those persons who have
been engaged in drilling and blasting underground and concluded
that " pneumonoconiosis arising as a result of work in Broken Hill
only progresses so slowly that no impairment of working capacity
occurs previous to infection with tuberculosis ".
The Commission recommended exclusion from the mines and
compensation of all persons suffering from tuberculosis ; also that
no person suffering from pneumonoconiosis should be allowed to
continue working on the mines. The reasons given for the lastmentioned recommendation were: increased liability of such
persons to tuberculosis and pneumonia, and other pulmonary
diseases will be more severe and more fatal; such persons should
follow an open-air occupation, agricultural or pastoral, and will
thus be brought less frequently into contact with other persons
and less often exposed to tuberculous infection; they should be kept
under observation and a scheme for employment prepared.
In a further report in 1922 on 6,538 miners, the Commission
stated that the form of pneumonoconiosis found at Broken Hill is
characterised by changes along the air passages and beneath the
pleural covering of the lungs and by scanty affection of those parts
directly concerned with respiratory exchanges. This form of
pneumonoconiosis was stated to differ from those found among
miners at Bendigo, Cobar and Kalgoorlie, and among rock-choppers
in the Sydney sandstone.
Of 2,618 underground men examined, 266 showed pneumonoconiosis, 113 in the first stage, 51 in the second stage, and 102
complicated by tuberculosis; 107 additional men were diagnosed
as suffering from tuberculosis onry.
As a result, two Special Rules applying to the Broken Hill district
were incorporated in the Mines Inspection Act of New South Wales
regulating firing as far as possible to the end of shift, and requiring
the moistening of ore being filled or moved in any working place,
to prevent the escape of dust.
A Bureau of Medical Inspection was established to follow, up the
work of the Commission by examination of applicants for employment under the Workmen's Compensation (Broken Hill) Act, 1920.
Dr. S. A. Smith, of the Technical Commission, later analysed
certain important features of the relationship between pneumonoconiosis and tuberculosis.
He found that of 8,966 men examined, 322 showed changes
due to dust; of these, 148 or 46 per cent, suffered from tuberculosis.

300

PAPERS PRESENTED TO THE

CONFERENCE

Of the remaining 8,644 who showed no changes due to dust, 161 or
only 2 per cent, suffered from tuberculosis.
Of the 177 men showing simple fibrosis the subsequent history
was followed for two and a half years and resulted as follows :

Place

Total number

Number who developed
tuberculosis

Broken Hill
Adelaide
Melbourne
Sydney
Ballarat and Bendigo
Newcastle
Griffith
River and Country

101
19
6
2
3
1
34
11

27
7

Cities
Country

132
45

36 (27 per cent.)
1 (2 per cent.)

1
1
1

Dr. Smith concludes that " changes in the lungs due to inhalation
of mine dust produce a definite susceptibility to the development
of pulmonary tuberculosis ; that the development is most frequently
not an activation of an old lesion but a new infection, and that the
frequency of infection is proportional to the number of persons with
whom the affected worker is daily brought in contact ".
As a matter of interest, it may be mentioned here that the Broken
Hill silver-lead lode was discovered in 1883 and still represents the
main source of Australia's lead production, supporting a town of
17,000 inhabitants as well as the township of Port Pirie comprising
a further 13,000 inhabitants. At this port the Broken Hill ore is
smelted and the pure lead and other metals obtained. Mining
operations are at present carried out to a great extent in sulphide
ore which is sparsely intermixed with a gangue of rhodonite, a
manganese compound with a low free silica content. Analyses
of the country rock at Broken Hill have shown the silica content,
free and combined, to vary between 60 and 70 per cent., of which
less than half is free silica.
Broken Hill now represents the only considerable metalliferous
mining field in active working in New South Wales, although
many miners are still employed in tunnelling and quarrying
operations in Sydney, working in siliceous rocks, chiefly sandstone.
In 1922, the New South Wales Board of Trade, in conjunction
with the Commonwealth Department of Health investigated

SILICOSIS IN AUSTRALIA

301

clinically and radiologically the prevalence of pulmonary diseases
amongst workers in sandstone and other siliceous rocks in the
metropolitan district of Sydney. Of 716 men examined, 123 were
found to be suffering from silicosis. Using the standards set down
by the Broken Hill Commission, 47 of these were diagnosed as
being in the first stage, 38 in the second and 38 were stated to be
suffering from pneumonoconiosis complicated by tuberculosis.
In 16 men, pulmonary tuberculosis only was diagnosed.
In 1927 Dr. Charles Badham drew attention to a series of cases
in which the X-ray films showed a very fine type of fibrosis (Report
of Director-General of Health, New South Wales, 31 December 1927,
p. 102). These cases came from tunnels around Sydney where the
country rock contains a high proportion of combined silica.
Dr. Badham considers that the fibrosis probably differs from true
silicosis and suggests the term " Silicatosis " for such cases.

STANDARDS OF MINE VENTILATION

The Broken Hill Technical Commission in its report of 1922
regarded ventilation as the most important factor in the removal
of dust from the mines, and stated as its opinion that an air current
exceeding 20 feet per minute was sufficient to keep the suspended
dust below the quantum necessary to give rise to pneumonoconiosis.
While this amount of air movement was not obtainable in large
stopes, it was recommended that the working of mines be laid out
to ensure as far as possible an air velocity of 20 feet per minute.
Dependent on the dilution of the concentration of dust by a large
volume of air, the Commission found that the passage of 5,000 cubic
feet a minute past any working place would be sufficient to prevent
the accumulation of dust in the air during the conduct of mining
operations, except in the immediate neighbourhood of drilling
operations without adequate water supply or where heaps of dry
ore were being shovelled. The Commission stated that water
must be used to assist ventilation in keeping down dust in these
operations.
In 1924, Dr. Badham considered that 60 linear feet of air-movement per minute were necessary to keep the dust content low. He
prescribed a standard of 200 dust particles per cubic centimetre for
sandstone tunnelling and said that this " could in all well-ventilated
works be halved ". Dr. Badham used the Owens' dust sampler
in his work, checking his results by gravimetric methods.

302

PAPERS PRESENTED TO THE

CONFERENCE

LEGISLATION

In 1920 a Workmen's Compensation (Silicosis) Act, 1920 (No. 13
of 1920), was passed in New South Wales to amend the Workmen's
Compensation Act of 1916. The purpose of this Act was to enable
the provision of a scheme of compensation to be paid by the
employers to workmen certified to have suffered death or total
disablement from fibroid phthisis or silicosis of the lungs, or from
that disease complicated by tuberculosis or from any other
pulmonary disease caused by exposure to silica or other dust, also
to those men who though not totally disabled are found on medical
examination to be suffering from any of the above diseases to such
an extent as to make it dangerous to continue work in the industry.
This Act applied to any man engaged in work involving exposure
to silica dust, who had been continuously resident in New South
Wales during five years immediately preceding the date of death or
incapacity and who had been employed as specified for not less than
three hundred days during that period, or to men who had been
resident for five years out of seven and had been employed for at
least five hundred days in that period.
Under this Act was produced in 1927 the Workmen's Compensation (Silicosis) Scheme No. 1, applying to stonemasons, quarrymen,
rock-choppers and sewer miners in the Sydney area who are eligible
under the residential and employment qualifications mentioned
above, and who have been certified in accordance with the
conditions prescribed in the Act.
Under this scheme the question of the award, amount and
apportionment of compensation rests with the judgment of a Joint
Committee appointed by the Minister under the scheme. Provision
is made for the immediate payment of compensation by the
employer in accordance with the general rate for the State in the
case of death or total disablement and, where men are suspended
from work owing to silicosis, but not totally disabled, for the
payment after two weeks of a sum which will supplement, if
necessary, his earnings making them equal to his previous earnings.
This sum is paid from a general fund maintained by subscriptions
from the employees, and which may be subsidised from time to time
by Parliamentary vote. The subscriptions are fixed and levied as
necessary by the Minister and the fund is administered by the Joint
Committee. Provision is made under this scheme for the payment
of lump-sum compensation, and the appointment of medical
authorities for periodical examination and certification. The

SILICOSIS IN AUSTRALIA

303

onus for arranging preliminary medical examination is thrown on
the employer, and the workman is obliged to submit himself for
periodic and other examinations, to give the necessary true
information in respect of his employment and not to re-engage
in any industry affected by the scheme after suspension.
Employees in the mining industry at Broken Hill come under a
special Act known as the Workmen's Compensation (Broken Hill)
Act, 1920 (No. 36 of 1920), which is also construed with the
Workmen's Compensation Act, 1916. This Act includes a scheme
known as the Broken Hill Mines (Pneumonoconiosis-Tuberculosis)
Compensation Scheme.
The present medical authority under this scheme is appointed
in Broken Hill by the Minister and includes the medical officer
in charge of the Bureau, which has been in operation since 1922.
Prior to the introduction of the scheme which is similar in details
of operation to the Silicosis Scheme No. 1 described above, the
Technical Commission of Enquiry represented the authority.

Victoria
GENERAL

The history of metal mining in Victoria is concerned mainly with
gold, which was discovered on four large alluvial fields between
July and December 1851. Of these fields the only one in which
there has been any activity of recent years is Bendigo. Deep
mining was commenced in this place shortly after 1870. The
country rock consists of quartz, slates and sandstones with a high
silica content. The field at present is in a very low state, less than
a hundred men working underground where formerly there were
thousands. At one time there were fifty-three shafts in operation,
over 2,000 feet deep and several over 4,000 feet, the deepest
reaching 4,614 feet.
The Ballarat field in which lode mining was formerly practised,
although at no great depth, has been closed down for many years..
INVESTIGATIONS AND ENQUIRIES

In 1907 Summons submitted a report on miners' phthisis to
the Committee of the Bendigo Hospital, stating that there was
undue mortality among Bendigo miners and that this was due

304

PAPERS PRESENTED TO THE CONFERENCE

to respiratory diseases, notably tuberculosis. He classified the
cases examined according to two clinical types :
1. A pure fibrosis of the lungs, non-tuberculous in origin, which is
silicosis.
2. The mixed type with a tuberculous infection in a fibroid lung.
Of those affected with either type, 47 per cent, had specific
bacilli in the sputum. Summons stated that " although only
47 per cent, of cases are infected, all miners dying of lung complaint
die of tuberculosis ".
No further work of this nature was undertaken in Victoria until
1920, when D. G. Robertson investigated clinically the conditions
amongst miners in Bendigo. He found the incidence of tuberculosis
higher in Bendigo than in the rest of the State, and attributed this
to the presence of old miners affected with pulmonary disease.
A compensation scheme was recommended.
In 1928 the Commonwealth Department of Health conducted
an investigation into the health and working conditions of employees
in the metal-mining industry in Victoria and Tasmania at the
request of the Commonwealth Court of Conciliation and Arbitration. In Bendigo sixty-one men were examined radiologically
and clinically, representing 37 per cent, of the total metalliferous
mine employees in the district. Among underground workers
9.4 per cent, were diagnosed as suffering from silicosis uncomplicated
and a further 7.5 per cent, from silicosis and tuberculosis. Of all
workers, 3.3 per cent, were found to be suffering from tuberculosis
only.
MINE VENTILATION

In 1906 Summons stated that it is " unnecessary to demand that
a fixed volume of air be supplied to the working faces for the
quantity is only a means to produce the quality and to maintain
less than 0.15 per cent, of carbon dioxide in the air ".
The investigation by the Commonwealth Department of Health
in 1928, referred to above, included an examination of the working
conditions. In respect of three mines visited at Bendigo it is noted
that the temperatures ranged from 61° F. to 76° F. and the relative
humidity averaged 88 per cent. The dry katathermometer cooling
power averaged 4.9, a figure stressing the need for improvement
in ventilation. The recommendations included in the report of the
mining engineer who conducted these inspections stated that in all
drives and cross-cuts over 100 feet, and rises and winzes over

SILICOSIS IN AUSTRALIA

305

30 feet in length or depth, artificial means of ventilation should be
adopted unless bratticing is effectively carried out. Further
recommendations include the supply of an extra hose for wetting
heaps of broken ore when shovelling, special precautions for
supplying water when " collaring " and against fogging from
machines, and the restriction of firing to times at which the mine
will be empty of workers.
LEGISLATION

Industrial pulmonary diseases including tuberculosis are not
included in the schedule of diseases for which compensation is paid
in Victoria and no other legislation exists dealing with this subject.
The Mines Act, 1914, of Victoria contains the following clause
relating to drilling : " No hole shall be bored or drilled by machinery
underground unless a jet or spray of water shall be directed into and
around such a hole. "
Queensland
GENERAL

Gold was first discovered in Queensland at Gympie in 1867.
The country rock in this field consists largely of limestone, shales
and slates. In 1872 the Charters Towers field was discovered, and
in 1882 the Mount Morgan gold and copper deposit was found and
has been worked practically up till the present day. The country
rock at Mount Morgan consists of limestones, banded claystones
and tuffs with quartz-porphyry dykes and sills and contains a fairly
low silica content. Copper has been discovered at Cloncurry and
mixed metallic deposits at Herberton and Chillagoe. All these
fields are at present inactive, and the most active field at this time
in Queensland is the Mount Isa silver-lead lode situated west of
Cloncurry, far inland. The work at present in this area is wholly
developmental.
COMMISSIONS AND ENQUIRIES

In 1911 a Royal Commission was appointed in Queensland
to enquire into the working conditions in Queensland mines in
relation to the health of the miners.
This Commission concluded that pulmonary fibrosis was not as
common in Queensland as in Victoria and Western Australia, but
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that pulmonary tuberculosis appeared to be a„ relatively frequent
cause of death among metalliferous miners in Queensland.
Recommendations were made dealing with dust-prevention,
ventilation and sanitation.
The Commission considered that miners suffering from pulmonary
or laryngeal tuberculosis should be excluded from underground
work, provided that means be taken to deal with the predisposing
causes of infection among miners and among the general population,
also providing that the difficulties in connection with the medical
examination and the collection and distribution of funds be overcome in a reasonably economical manner.
LEGISLATION

In 1915 the Queensland Government granted to mine employees
suffering from pulmonary diseases a weekly allowance.
The Workers' Compensation Act, 1916 to 1926, of Queensland
awards compensation for death or incapacitation from earning full
wages at the work at which he was employed, as a result of certain
industrial diseases. The list includes " silicosis of the lungs,
miners' phthisis, pneumonoconiosis, pulmonary tuberculosis".
South Australia

Although in the past copper was mined extensively at Wallaroo
and Moonta, the mining industry of this State is now very small and
confined to a few scattered enterprises. No investigations or
enquiries have been made dealing with the health of miners.
Industrial pulmonary diseases are not subject to compensation.

Tasmania
GENERAL

Although small in area this State is very rich in mineral resources.
Gold has been mined in the Northern part of the island and tinsluicing and mining is still carried on in the North-eastern part,
but it is the West coast on which the larger mining operations are
now practised. The two most important fields are at Mount Lyell
and Rosebery. At the latter place an extensive zinc field is being

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307

developed around the site of two older mines, but relatively few
men are employed here at present. At Mount Lyell a rich deposit
of copper ore was first discovered in 1897. About 500 men are still
employed underground here. The country rock is partly a
conglomerate with quartzite pebbles embedded in a cementing
matrix, and partly a schist. The silica content of the schist
averages 60 per cent, and that of the conglomerate about 90 per cent.
The ore contains about 63 per cent, silica, probably 50 to 60 per cent.
in the free state.
INVESTIGATION

The only investigation into the health and working conditions
of metalliferous mine employees in Tasmania was made in 1928
by the Commonwealth Department of Health. Reference has
already been made to the Victorian portion of this enquiry.
In Tasmania the various mining centres were visited in turn
and men examined clinically and radiologically practically at thé
mine-head. For radiological purposes a portable plant was used
and was installed in the mine offices or in some suitable place close
to the mine. At several mines the management permitted the
men to undergo examination while on duty, and these men were
brought to the surface during the working shift, examined and then
returned to work.
In all, 650 mine employees volunteered for examination, comprising 65 per cent, of those available.
Of 314 underground employees, 5.9 per cent, were shown to
be suffering from uncomplicated silicosis and 2.1 per cent, from
silicosis with tuberculosis. Of all workers examined, 1.1 per cent.
were found to be suffering from tuberculosis only, 1.2 per cent, in
underground and 1.0 per cent, in surface workers.
Inspection of the industrial histories of examinees showed that
there was a definite incidence of silicosis among those who had
worked underground in Tasmania only, and also in Mount Lyell
only, although in neither case was the incidence as high as that
observed in Victorian mine employees.
The incidence of
tuberculosis, either alone or complicating silicosis, was found to be
much lower in Tasmanian miners than in those examined at
Bendigo.
MINE VENTILATION

The working conditions in Tasmanian mines were inspected and
form the subject of a portion of the report in the above investigation.

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The temperatures recorded ranged from 47.5° F. to 69° F. and the
average relative humidity was 92 per cent. The dry katathermometer cooling power averaged 7.1, indicating satisfactory ventilation.
Dust counts made with the Owens' instrument and checked by a
gravimetric method were on the average satisfactory, but
unnecessarily high in some places.
The recommendations regarding mine hygiene quoted in the
section dealing with Victoria apply also to Tasmanian mines.
LEGISLATION

No industrial diseases are subject to compensation under
Tasmanian law, although an Act was passed during 1929 * in an
endeavour to provide miners disabled through industrial disease
with a pension.
Western Australia

Gold was discovered at Northampton in Western Australia in
1842 and at Kimberley in 1882, but it was not till the discovery
of the Coolgardie field in 1893 and the later discovery of the
adjacent Kalgoorlie field that the mining industry of the State
began to flourish. To-day many fields are in operation in various
parts of this large State, employing over 4,000 men, about 3,000
of whom work in the famous " Golden Mile " between Kalgoorlie
and Boulder City. The mines here are worked in some instances to
a depth of over 3,000 feet in a country rock consisting of quartz
diabases, calc-schists and acid amphibolites. An analysis of the
dust collected in a dry-crushing mill and measuring less than
10 microns in diameter shows 43.58 per cent, silica. The approximate proportion of free quartz in this dust is 19 per cent.
INVESTIGATIONS AND ENQUIRIES

The Western Australian gold-mining industry has been the subject
of more Royal Commissions than that of any other State.
The first of these was a Royal Commission appointed in 1905 to
enquire into the ventilation and sanitation of the mines in Western
Australia. This Commission expressed itself as unable to form an
opinion as to the degree to which miners suffered from pulmonary
disorders. Although only two cases of silicosis of local origin had
been reported to the Commission, the local hospital returns showed
that diseases of the respiratory system fell heavily upon miners.
1

INTERNATIONAL L A B O U R O F F I C E : Legislative

Series, 1929, A u s t r . 2.

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309

Assuming that the necessity for proper ventilation and sanitation
was proven the Commission concerned itself with prescribing
standards and procedures designed to secure efficiency in these.
The exclusion of persons suffering from tuberculosis of the
respiratory organs from underground working was recommended,
but not adopted, by the Government at that time.
In 1910 a Royal Commission was appointed to report upon
pulmonary diseases among miners. The report of this Commission
concluded :
The miner is more liable to lung disease generally than the average
male over fifteen years of age. The miner is less long-lived than the
average male over fifteen, partly on account of greater liability to lung
diseases.
Tuberculosis of the lungs is on the increase among miners and is
twice as prevalent as among all males over fifteen.
Pneumonia among the acute, and bronchitis, asthma, emphysema
and fibrosis of the lungs among the chronic, lung diseases are more
prevalent among miners than among males over fifteen.
Mine employees were physically examined and the conclusion
was drawn that fibrosis of the lungs could be detected amongst
various groups of men in increasing percentages according to
exposure to silica dust at work; also t h a t exposure over
comparatively long periods was necessary before the onset of
recognisable symptoms. Machine mining and dry-treatment work
were noted as prominent causes of fibrosis, especially machine
work. Non-machine miners and truckers were found to be affected
although to a less extent, and after much longer periods.
Tuberculosis was not commonly found.
The principle was laid
down that " any man suffers from fibrosis to the extent to which
he is exposed to the continued inhalation of mineral dust. If
there be no dust, there will be no fibrosis, and conversely, the
continued inhalation of dust certainly produces some fibrosis ".
The findings of the Commission prompted the appointment of
another Royal Commission in 1911. This Commission found that
" pneumonoconiosis without the super-imposition of other diseases
of the respiratory organs had not yet attained very alarming
proportions in Western Australia, and if the precautions suggested
be carried out gold mining will become very little more injurious
to health than other industries ".
Standards of procedure in respect of ventilation and dust
prevention were prescribed and, for the first time in Australia,
the recommendation was made that men suffering from tuberculosis
or pneumonoconiosis be excluded from mine work, and in order to

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secure that this be effectively done, that every man should be
medically examined before employment and all miners be medically
examined at intervals of six months. The tuberculous person and
his dependants were recommended as charges of the State and the
pneumonoconiosis patients to be compensated under an insurance
scheme.
In 1925 as a result of the recommendation of the above Commission, an arrangement was made by the Western Australian
Government whereby the Commonwealth Department of Health
made a complete physical and radiological examination of all
metalliferous mine employees in Western Australia. This was
carried out in Kalgoorlie at the Commonwealth Health Laboratory
and in the surrounding country districts by a travelling unit
equipped with a portable X-ray apparatus.
The following standards of diagnosis were adopted :
" Normal." — No evidence of pulmonary lesions due to dust, tubercle
bacilli or any other cause.
" More fibrosis than normal." — Lung abnormality but not silicosis
or tuberculosis.
Three types are recognised: (a) healed or inactive lesions not due to
dust; (6) reticular markings accentuated as from arteriosclerosis, old
age, auto-intoxication, high blood pressure or renal disease; (c) the
same accentuated linear markings from dust. Dust other than siliceous
may cause this but is not progressive. The appearance radiographically
is of a fine network but without mottling. It should be noted, however,
that where tuberculosis also is present these come under " silicosis plus
tuberculosis ".
Subjects in this class were not reported under the Miners' Phthisis
Act because: (i) the X-ray technique could not then secure uniformly
reliable pictures; (ii) the same appearance was obtained in certain
non-silicotic subjects; (iii) absence of symptoms; (iv) a clear definition
was necessary of the group of cases coming within the meaning of the
Act.
" Silicosis, early." — Fine mottling throughout; often breathlessness,
cough and sputum; no physical signs.
" Silicosis, advanced." — Coarse mottling of the small " snowstorm "
variety; often symptoms; phagocytic cells in the sputum containing
dust ; chest movements restricted in all movements ; absence on inspection
of the inspiratory bulging movement of the upper anterior part of the
chest in the triangular areas between the lines joining the acromioclavicular and sterno-clavicular joints and nipple on each side; dull
to percussion; restricted air-entry and harsh broncho-vesicular murmur;
rales often heard at bases.
" Silicosis plus tuberculosis " and " Tuberculosis only ". — Diagnosed
on established clinical standards.
During 1925 and 1926 a total of 4,067 miners were examined.
The results of this examination may be tabulated as follows:

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SILICOSIS IN AUSTRALIA

Number
Per
with
cent.
silicosis of total

Surface workers
Underground
workers
Total

Silicosis Per
Tuberplus
culosis
tuber- ofcent.
only
total
culosis

Per
Number
cent.
exof total amined

117

6.6

1.5

0.3

1,759

538

23.3

116

5.0

0.3

2,308

655

16.1

143

3.5

0.3

4,067

Silicosis was not found in any case under forty years of age or
with less than five years' underground work.
Since 1926 examinations have been made of the mine employees
in Western Australia annually by the Commonwealth Department
of Health. Of 2,290 men previously classed as normal in 1927,
30 or 1.3 per cent, were found on re-examination to be suffering
from silicosis uncomplicated, and 13 or 0.5 per cent, from silicosis
with tuberculosis. A further 3 or 0.2 per cent, had tuberculosis
only. Of 491 diagnosed as silicotics, 86 or 17.5 per cent, showed
silicosis with tuberculosis. In 1928, of 2,822 men classed as normal
in the previous year, 48 or 1.7 per cent, had progressed to silicosis
only, 11 or 0.4 per cent, to silico-tuberculosis, and 3 or 0.1 per cent.
were found to be suffering from simple pulmonary tuberculosis.
Of 425 silicotics, 25 or 5.9 per cent, showed signs of tuberculous
complication on re-examination. In 1929, of 2,293 normals
re-examined, 100 were diagnosed as silicotics. A further inspection
of these cases, however, made it evident that the majority of these
diagnoses were due to the introduction of improved plant and
radiographic technique. It was considered that in only 26 or
1.1 per cent, of cases a definite advance had occurred in the disease.

MINE

VENTILATION

In 1905 the Royal Commission on the Ventilation and Sanitation
of Mines laid down the first standards of air-composition for mines
in Western Australia. This prescribed a maximum of 0.15 per
cent, of carbon dioxide and a maximum temperature of 85° F.
in any part of the mine.
When this subject was brought under consideration by the Royal
Commission of 1911 no standards were recommended, the Commission considering that further enquiry on the subject was necessary.

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LEGISLATION

The first practical results of the recommendations of the Royal
Commission of 1911 was the Miners' Phthisis Act of 1922 which
was passed with the object of removing persons suffering from
pulmonary tuberculosis from the industry, and the payment of
compensation until suitable employment could be found for them.
This Act was proclaimed on 7 September 1925, and provided
that:
(a) Every person engaged in mining operations be required to
submit himself when required to an appointed medical officer
for examination;
(b) If on examination he is found to be not suffering from tuberculosis,
he shall receive a- certificate to that effect ;
(c) If on examination he is found to be suffering from tuberculosis,
the Minister may prohibit his employment in any mine;
(d) If on examination he is found to have developed definite symptoms
of miners' phthisis uncomplicated by tuberculosis as to indicate
that further employment in, on or about a mine may be detrimental to his future health, the Minister shall notify him accordingly.
Compensation for tuberculosis amounts to the ruling rate of pay
in the districts in which the sufferer was employed at the time of
prohibition of employment, until other suitable employment is
found and offered by the Mines Department.
Under the Miners' Phthisis Amendment Act of 1925, if any
prohibited person is or has become unable to work at any suitable
employment, compensation as above shall cease to be payable,
but such person shall be entitled to receive compensation not less
than as prescribed by the scale of relief in force at the
commencement of this Act, under the rules of the Mine Workers'
Relief Fund, and similar compensation is accorded the dependants
on the death of any such person.

SILICOSIS IN BELGIUM
BY

DR. D. GLIBERT, BRUSSELS

The study of silicosis may even at the present time be said to have
made very little progress in Belgium. Only the stage of establishing
contact with this important problem has been reached, and the
efforts of a few experts are at present concentrated in first of all
bringing to the notice of medical circles knowledge of the results
obtained in countries where for years back the question has been
thoroughly investigated. It may be asserted that the question
of the diagnosis of silicosis has so far hardly received the attention
of the great majority of medical practitioners in our country.
As regards public opinion, almost complete ignorance reigns in
regard to this matter. The workers' organisations themselves,
representing as they do the most interested parties, would appear
to show little or no concern in regard to the problem. At most
a few articles have appeared in the daily political press, but this
isolated effort has met with no echo.
In official administrative spheres action has consisted in the
appointment of a non-official committee, but up to the present no
really practical measure has been taken to obtain a comprehensive
view of the subject.
This delay would appear to be due to several causes, the principal
of which are as follows :
The Government, and more particularly the medical factory
inspectorate, has at its disposal neither radiographic installations nor the experienced staff required for this delicate
research work.
The extremely restricted credits granted are besides
earmarked for definite purposes which exclude the possibility
of the use of funds for effecting costly studies of this kind.
It would be necessary, in order to form a well-grounded opinion
on the subject, to examine a great number of patients, to have
at one's disposal numerous radiographs, and in consequence to

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involve relatively high expense. Nevertheless, thanks to
special subsidies voted with a view to Government participation
in the Liege Exhibition, the medical factory inspectorate has
been able to make a certain number of radiographs which will
be submitted to public view on the stands of the group designated " Social Insurance and Social Welfare ". This will
ensure effective propaganda amongst those best adapted to
profit by a knowledge of the question.
The obstacles referred to above, however, are far from being
those most radically opposed to a practical and extensive study
of silicosis in Belgium.
The economic state of the country together with its industrial
requirements are at present such that the greatest care must be
taken to prevent manual labour from quitting certain industries
in which, up till quite recent times, labour has been rather scarce.
In principle employers are in favour of research effected in relation
to the health of their workers. Many of them even encourage such
research, yet all of them are insistent on the necessity of progressing
with discretion and preferably limiting action to profiting by
circumstances when workers spontaneously present themselves for
medical examination, complaining of symptoms connected with the
respiratory system. It is evident that in such conditions there is a
risk that lack of positive data in sufficient number may yet delay the
solution of the problem in Belgium for a long time.
It is good to be able to add, with a view to qualifying the lack
of encouragement in the preceding paragraphs, that a new fact
has just occurred which is capable of modifying considerably the
situation. The Government has just granted a considerable subsidy
(100,000,000 francs) for the anti-tuberculosis campaign.
Silicosis being often complicated with this disease to such a point
that the two are associated under the names silico-tuberculosis and
tubérculo-silicosis, it will probably be possible to organise a fairly
extensive enquiry relative to silicosis properly so called. So far
unofficial contact has been established with the medical authorities
on whom shall rest the responsibility of organising this great
campaign, which is in course of preparation. The above facts,
however, only constitute matter for hope. In the meantime, a
few facts are given below which show that here and there isolated
research workers are engaged in praiseworthy efforts with a view to
contributing by their personal research to a solution of the problem.
Dr. Courtois, attached to the Marcinelle Sanatorium, an institu-

SILICOSIS IN BELGIUM

315

tion founded fairly recently, presented to the last sitting of the
Society of Scientific Studies on Tuberculosis an excellent work on
the relation between tuberculosis and anthracosis occurring amongst
sanatorium patients drawn from the mining population.
The
discussion of the question thus instituted will eventually be carried
further.
Dr. Denet-Kravitz, Director of the Medical Social Dispensary
of the Henricot Factories at Court-St. Etienne (Metallurgy), has
interested himself particularly in the question.

In a note which he has sent me he states:
The first victims of silicosis which I had a chance of observing before
the war or immediately after the armistice were authentic tubercular
subjects dying more of tuberculosis than of pneumonoconiosis properly
so called.
I have since then (in 1920) systematically examined all the workers
who, amongst those submitted to me for examination, seemed to me
likely to develop silicosis, the examinations in question being therefore
preventive examinations of " non-sick workers ".
My first observations, published in January 1924, in the Belgian
Tuberculosis Review, led to the following conclusions:
(1) Radiography is the only means of following the disease in
its initial stages, clinical examination and radioscopy being
insufficient.
(2) At the outset of the disease there is seen to develop a bundle
of sliadows, the accentuation of normal vascular and bronchial
shadows starting from the hilum and spreading fanwise, then
subsequently, contemporaneously with the lengthening of these
shadows, a reticulated area which becomes closer and closer.
(3) Most frequently the apices are clear.
(4) The affection is not necessarily bi-lateral.
(5) Aggravation of the process is not in proportion to the length
of exposure to the dust, the individual factor here playing a role
of great importance (lymphatism).
I should like to draw attention to the fact that the results of my
examinations are in accordance with the already old histological results
obtained by Arnold, which showed the anatomopathological modification
of the lymphatics.
In consequence of other observations published in the Belgian Tuberculosis Review. March-April-May 1926, I was led to conclude a
scleroginous fibrofying action of the silica.
In the March-April 1928 number of the same Review, I described a case
of nodular pulmonary sclerosis, interesting by reason of the fact that
I had had the man in question under observation since 1921, at which
time he still presented a negative radiological image and that having
radiographed him periodically I had seen develop little by little an image
comparable, one might say, to that of the corymbiform granular form
of pneumonoconiosis starting from the hilar regions, and that though
the patient had been for a long time withdrawn from the action of the
vulnerating agent the process had continued (see Böhme). The B.C.G.

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reaction (Calmette-Guerin test) had always been negative as well as the
test for the bacillus in the sputum.
In No. 6, March 1928, of the Review of Industrial Accidents, I resumed
my former observations, drawing a striking comparison between them
and the works of Drs. Leon Bernard, Potter and Thomas on pulmonary
sclerosis with arrested development, containing radiology identical with
that which I had found for the sclerotic subjects at the outset—identical
to such an extent that I was forced to ask myself if different causes might
not be capable of setting up phenomena of the same character in specially
predisposed subjects.
In the early cases which I have been able to observe there could have
been no question of tuberculosis. In the pseudo-granular case (le cas de
pseudogranulie] perhaps there is association, even though there ought
to be taken into account the fact that this case has been developing
for nine years back.
Finally, Dr. Stassen, Director of the Provincial Institution
at Liege for the Study of Occupational Diseases, sends me the
following communication :
Pneumonoconioses other than pulmonary anthracosis have also been
made the subject of certain researches in the Province of Liege. On the
initiative of the Permanent Deputation an enquiry was made in 1924
in the district of the Ourthe and Amblève quarries with a view to discovering whether diseases of the respiratory passages were particularly
frequent amongst the quarrymen.
All the quarrymen suffering from pulmonary affections who believed
in any direct or slight connection between such affection and defective
working conditions were invited by posters to present themselves at
certain hours fixed in advance for examination by the medical investigators. The latter in the course of their visit at the same time
established contact with the medical practitioners in the neighbourhood
of the quarries.
The enquiry lasted for six weeks, one sitting being held each week:
20 workers suffering from affections of the respiratory passages offered
themselves for examination; 5 cases were retained as possibly being
due to silicosis.
Two cases were radiographed, but the radiographic plates as well
as the radioscopie images did not permit in any case of the detection
of the characteristic signs of silicosis. The plates assembled did not differ
remarkably from the radiographic plates of lungs infected by tuberculosis.
Amongst the tunnellers and perforating-machine men employed in
excavating roads through stone strata in the coal mines we have found
about 10 cases which might be suspected of being silicosis. As in the
case of the quarrymen, however, the radiographic plates were not
characteristic and might be confused with plates of other affections
having no relation to the working conditions of the men in question.

SILICOSIS I N CANADA
BY

J. G. CUNNINGHAM,

M.B., DIRECTOR, DIVISION OF

INDUSTRIAL HYGIENE, DEPARTMENT OF HEALTH, ONTARIO

From east to west in Canada, there is a widely diversified mineral
production. Some of these operations are on a large scale. Gold
is mined in nearly every Province. Nickel is limited to Ontario
and asbestos to Quebec. Copper is important in British Columbia,
Ontario and Quebec.
In manufactured products, Canada is second among the countries
in the British Empire, and in terms of their gross value 80 per cent.
of this industrial activity is centred in Ontario and Quebec. It is
natural that industrial hygiene activities should have developed
first in these two Provinces. Ontario established a Division of
Industrial Hygiene in the Department of Health in 1920, and in
Quebec such a Division was established in the Public Health
Department of McGill University in 1928.
" Miners' phthisis " was included in the list of compensatable
diseases enumerated in the Workmen's Compensation Act of
Ontario in 1917. Its legal interpretation requires the presence
of silicosis with active tuberculosis in a miner. The first case
was compensated in 1924 on medical evidence submitted by
Dr. C. D. Parfitt.
In the Alberta Workmen's Compensation Act, the disease in
1928 was designated: " Pneumonoconiosis which shall be deemed
silicosis, siderosis, lithosis in quarrying, cutting, crushing, grinding
or polishing of stone, or grinding or polishing of metal. Mining. "
No cases have been compensated.
The Nova Scotia and British Columbia Workmen's Compensation
Acts, while they do not specify silicosis as a compensatable disease,
enable the workman to claim compensation for disease due to
occupation as though it were a compensatable injury.

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In Saskatchewan, the Workmen's Compensation Act, not yet
in operation, provides for compensation of industrial workers
suffering from silicosis, and for making regulations for the prevention
of this and similar industrial diseases when necessary.
In Manitoba, in 1929, a Bill was introduced to the Legislature
providing for the compensation and prevention of silicosis. This
was set aside pending the recommendations of a General Committee
now considering the existing Workmen's Compensation Act. In
the meantime, the Mines Department has drafted rules, not yet
in effect, intended to control the hazards from dust and tuberculosis
in mines. Recently, the Provincial Department of Health has
established a clinic for the examination of gold miners to determine
whether silicosis is present.
In Ontario, silicosis has been the subject of clinical enquiry,
particularly in the mining industry, in quarrying and among granite
cutters. The pathology of the disease has been studied. The
results follow.
Attention was first directed to the subject in 1924 in an article,
" Silicosis in Ontario Gold Mines ", by Dr. J. H. Elliott, who
reported physical examination findings in eleven men who had
been engaged in underground work in the Porcupine mines in
Ontario for more than seven years with no other exposure to silica
dust. Three of these men presented evidence of silicosis, indicating
that the disease was being produced in this mining area. The
recommendation was made and carried out that these men be
placed at work on the surface away from exposure to dust. Up to
the present time, two of them have progressed to the primary
stage of silicosis and the other one has died with ante-primary
silicosis complicated with tuberculosis.
SURVEY OF GROUPS OF MINERS

In 1925 and 1926, a further survey was made by the Industrial
Hygiene Division of the Ontario Department of Health, covering
the four principal mining areas, all situated in the Northern part
of the Province, viz. Porcupine, Kirkland Lake, Cobalt and Sudbury.
Miners with more than five years' experience underground in the
individual mining area and with no exposure to silica dust elsewhere
were to present themselves for physical examination. Some were
included who had worked underground elsewhere.
The examination findings based on consideration of both physical
condition and X-ray manifestations are reported in terms of the

319

SILICOSIS IN CANADA

classification of stages of silicosis, developed by the South African
Miners' Phthisis Medical Bureau. The interpretation of these
standards was made possible through the guidance of Dr. J. M.
Smith, of the South African Miners' Phthisis Medical Appeal Board,
at the time of his visit to Ontario in 1927.
It is unnecessary to outline the details of the clinical classification
or the pathological findings upon which it is based. These have
been described in detail by W. Watkins-Pitchford in the Journal of
Industrial Hygiene for April 1927, and by L. G. Irvine and A.
Mavrogordato in the 1929 Report of the Convention of the International Commission for the Study of Occupational Diseases.
The years of exposure are based on statements made by. the
man at the time of examination. The occupational history was
detailed from the time the man left school. Where, in view of age,
it was apparent that this was incomplete, the history was carefully
reviewed.
TABLE I. ••— SURVEY EXAMINATION FINDINGS, 1 9 2 5 AND 1 9 2 6
Average years of exposure
Mining
area

Number
of
examinations

Porcupine

236

Ante-primary
Primary
Secondary

29
9
8

Kirkland
Lake

280

Ante-primary
Primary

11
2

Stage of
silicosis

Number
of
cases

Secondary

Same
area

Elsewhere in
Ontario

Outside
Ontario

9
9
10

1
0
3

1
0
4

3
5
5
(Both o utside K irkland
Lake )
(Both o utside 0 ntario)

Cobalt

398

Ante-primary
Secondary

6
1

11
12

2
0

6
0

Sudbury

306

Ante-primary

With one exception, the secondary cases were cases of silicosis
with tuberculosis. This survey was the first chest examination
conducted in these areas to include large numbers of miners. The
findings, therefore, represent an accumulation of cases.
Extensive chemical and petrographical examination of mine
rock samples to determine their free silica content, or dust counts
to determine the number or proportion of silica particles under ten
microns in mine air, have not been made.

320

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The type of rock encountered varies considerably from area
to area, from mine to mine in the same area and even from level to
level in the same mine, so that the degree of exposure even for one
occupation can be only approximate.
From the examination of such analyses as have been made,
enquiry at the Ontario Department of Mines and the Dominion
Geological Survey suggests that estimates may be made of the
average free silica content likely to be encountered as appear
in table II.
TABLE II.

CASES OF SILICOSIS WITH EXPOSURE IN ONE MINING
AREA ONLY

Mining
Area

Years
Average
Average
of oper- Probable Number Average
expo- Number expo- Number
expoation
cases
cases
persure
sure
cases
sure
of area centage antesecondin
in
primary
in
up to
ary
primary years
SiOa
years
years
1926

Porcupine
Kirkland
Lake

14
8

25-35
25-35

17
0

Cobalt
Sudbury

22
31

5-10
5-10

1
1

9.5

9
0

9
8

0
0

9.5

3
1
1
0

10.6
5
(crushers)
12

A few dust counts recorded in the article referred to above,
" Silicosis in Ontario Gold Mines ", made with the Palmer Spray
apparatus 1 and not distinguishing free silica from other dust
present, showed the highest count under wet conditions as
17,400,000 particles under 12 microns in size per cubic foot of air.
This cannot give more than a mere suggestion as to the exposure
involved.
The average number of years of exposure of cases of silicosis
among the men whose employment in mines was limited to the
area in which they were examined during this survey follows.
Reference to tables I and II shows that, of the cases in the
Porcupine area, over one-half had developed in that area. The
average duration of exposure of these cases was low at 9.5 to
10.6 years.
1
Comparative efficiencies of the Palmer Spray Machine, Sugar Tube
and Greenburg and Smith Impinger are given as 1 to 2.1 to 5. (Comparative
Tests of Instruments for Determining Atmospheric Dusts; Public Health
Bulletin No. 144, United States Public Health Service.)

SILICOSIS IN CANADA

321

The rock conditions are such that exposure is high in free silica
at times and very low at other times. Wet conditions have partly
obtained since the early days of this mining area.
The Kirkland Lake area has not been in operation for a sufficient
length of time to give any indication as to how much silicosis
the area may produce.
It is interesting to note that in Sudbury and Cobalt, with a
very low exposure to silica dust, among 300 and 400 men examined
respectively, many of whom had worked underground in one or
the other of these areas for twenty years and more, there appeared
only three cases of silicosis advanced as far as the ante-primary
stage. These men had worked underground for eight, nine and
twelve years.
However, apparently in a few individuals even the low concentration of free silica encountered in this area can produce the
disease.
A later case of secondary silicosis from the Cobalt area was a
case of advanced silicosis with tuberculosis, with exposure in this
area underground for twelve years and in the mill for five years.
The lungs presented pigmented, visible, palpable nodules, widely
distributed, a few of them, particularly under the pleura, at the
right apex, large enough to conform to the outline of lobules.
There was comparatively little pleural thickening, but extensive
cavitation at the left apex and consolidation of the remainder of
the left lung.
It should be recorded that in the Cobalt area, where the ore
itself contains from 30 to 35 per cent, arsenic, in 398 examinations
with stereoscopic X-rays of underground miners, most of them
with over twenty years' exposure, there was no case of lung
cancer.
In 1926, there was added to the list of compensatable diseases
in the Workmen's Compensation Act, " Silicosis occurring in mines ".
Three stages of silicosis, ante-primary, primary and secondary
are defined as in the South African Miners' Phthisis Act. To receive
compensation for silicosis, the miner who has developed the disease
must have been exposed to silica dust in his employment in Ontario
for periods amounting in all to five years preceding disablement.
The Act did not apply to those who had left their employment
previous to April 1926, but these cases might be compensated as
" miners' phthisis " cases if silicosis and tuberculosis with positive
21

322

PAPERS PRESENTED TO THE CONFERENCE

sputum was present. In such cases, the requirement for exposure
is shorter.
In April 1928, an amendment to the Mining Act provides for
physical examination on employment and yearly thereafter of each
workman employed underground in all mines except those exempt
by the Chief Inspector of Mines. At the same time, a " Certificate
of Freedom from Pulmonary Tuberculosis ", in force for twelve
months from the date of issue, is to be given to the workman,
certifying that he is free from tuberculosis of the respiratory organs.
This certificate is to be retained by the manager or superintendent
at his request, during the period of employment, and returned
to the workman on its termination or at the time of periodic
examination. In the same year, an amendment to the Workmen's
Compensation Act provided for the appointment of medical officers
to carry out the physical examinations required under the Mining
Act and defined tuberculosis of the respiratory organs as present,
when on examination it is found that, (a) " such person expectorates
the tubercle bacillus ", or (b) " such person has closed tuberculosis
to such a degree as to seriously impair his working capacity and
to render prohibition of work underground advisable in the interests
of his health ".
By this time, the mine operators, of their own initiative, in the
Porcupine and Sudbury areas, had already provided for physical
examination with X-rays, of underground miners employed, and of
applicants for employment. This procedure has been extended
to all four mining areas. Examinations are conducted under the
supervision of the Workmen's Compensation Board by physicians
employed by it and paid out of assessments levied on mine operators
for silicosis compensation purposes. Miners appear for examination
in accordance with a pre-arranged schedule. Those meeting the
requirements at initial or periodic physical examination are given
a certificate in accordance with the Act. For identification, a
photograph of the man with his X-ray number is taken at the same
time and attached to the certificate. Cases of silicosis or silicosis
with tuberculosis discovered in the course of these examinations
are submitted by the examiners to the Workmen's Compensation
Board. The claims include history of employment, medical history,
record of physical examination findings with stereoscopic X-ray
films of the chest.
When the history of exposure to silica dust in employment
in Ontario mines for at least five years has been verified, the claims

SILICOSIS IN CANADA

323

are passed for review to a Silicosis Referee Board composed of three
members of the Ontario Department of Health. As a rule, the
claimant is given physical examination by any two members of
the Referee Board, which makes periodic visits to the camps for
this purpose. The cases are then considered by all three members
and a unanimous decision regarding the diagnosis is transmitted
to the Workmen's Compensation Board.
As in the case of claims for accidents and other occupational '
diseases under the Workmen's Compensation Act, there is no
appeal from the decision of the Workmen's Compensation Board
except through the Board itself. Any claim may be re-opened for
the Board's further consideration by the workman or employer,
at any time, if new evidence is available.
Miners with a compensatable stage of silicosis are notified by the
Workmen's Compensation Board that their claims have been
allowed. At the same time, they are informed that if they continue
in work exposing them to silica dust, and should the disease progress,
they will be entitled to no further benefits. Should the miner cease
work in which he is exposed to silica dust, and should the disease
progress, be is then entitled to further compensation depending
on the stage to which he ultimately progresses. When tuberculosis
is present, the miner does not receive a certificate and cannot
be employed.
The Silicosis Referee Board indicates when, in its opinion,
the compensated cases should be re-examined for any purpose.
FINDINGS IN FIRST EXAMINATIONS OF ALL EMPLOYED MINERS

Hague and McBain reported, in an article entitled, " Silicosis
as an Industrial Hazard in Ontario Gold Mining ", in approximately 3,000 examinations of miners employed underground in the
Porcupine area, 39 ante-primary, 28 primary and 27 secondary
cases of silicosis.
In Kirkland Lake in 1929, in 1,793 first examinations, there were
6 ante-primary, 6 primary and 4 secondary cases of silicosis. Their
exposure averaged seven years in Ontario and four years elsewhere.
In Cobalt in 1929, in 662 first examinations, there were 7 anteprimary, 2 primary cases and one secondary case, with an exposure
averaging thirteen years in Ontario and three years elsewhere.
In Sudbury in 1927 and 1928, among 1,434 first examinations,
there were 6 ante-primary cases with an average exposure of
twelve years in Ontario and none elsewhere.

324

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COMPENSATED CASES OF SILICOSIS AMONG MINERS

Compensated cases are reported as from the ' mining area in
which the claimant was last employed. Movement from one area
to another is not infrequent. All cases in which the diagnosis has
been established, have not necessarily been compensated, because
of failure to satisfy other requirements of the Act. From April 1926
to 1 January 1930, there have been compensated 91 ante-primary,
58 primary and 33 secondary cases of silicosis. The proportion
of secondary to total cases is high.
Up to 1 January 1930, of the compensated cases, one anteprimary case compensated in 1927 has progressed to primary and
one ante-primary case compensated in 1928 has progressed to
secondary. Three primary cases compensated in 1926, two primary
cases compensated in 1927 and one primary case compensated
in 1928 have progressed to secondary.
In the Porcupine area, of 27 secondary cases compensated
to 1 January 1930, 15 have died. Of 17 secondary cases compensated in 1926, 9 died in 1926. Since then 10 more secondary cases
have been compensated and 6 have died. In the 15 death cases,
the period which elapsed between the time they were compensated,
which in most cases was shortly after disability arose, and the date
of death, averaged sixteen months. The compensated secondary
cases still living at 1 January 1930 have averaged twenty-seven
months since compensation was awarded.
Some interest attaches to the group of cases among the claims
for compensation submitted from the Porcupine area, which have
been examined by the Silicosis Referee Board.
TABLE H I . <— CASES FROM PORCUPINE AREA EXAMINED BY SILICOSIS
REFEREE BOARD, 1927-1930
Distribution of all cases
Stage of
silicosis

Ante-primary
Primary
Secondary

Number
of cases

20
9
35

Distribution of 35 secondary cases
Stage of silicosis
Uncomplicated secondary
Ante-primary and tuberculosis
Primary and tuberculosis
Secondary and tuberculosis
Silicosis and tuberculosis

Number
of cases
4
7
6
9
9

In this group, just under one-half of the cases are complicated
with tuberculosis. Nine cases reached the secondary stage before

SILICOSIS IN CANADA

325

the development of tuberculosis, but in most of them signs of
active tuberculosis followed rapidly.
Among the secondary cases are two which developed tuberculosis
some years after leaving the mines for work in the forest. One
had worked underground in the Porcupine area for six years up to
1920 and one had worked in the Porcupine area for seven years
up to 1919, that is, the development of tuberculosis was nine years
and ten years after removal from exposure. These cases did not
meet the requirements of the Act and were not compensated.
The " silicosis and tuberculosis " cases were mainly cases which came
to attention early in the work when tuberculosis already masked the
late evidences of advancing silicosis that may have been present. In
a few cases, the silicosis was of the massive bilateral type with signs
and symptoms indicative of superimposed tuberculous activity.
The tubercle bacillus has not been demonstrated in the sputum
of silicotics with tuberculosis as early, or as readily as might be
expected. This holds for both examination of smears, using
concentration methods and also for animal inoculation. Animal
inoculation has frequently produced a typical lesion, months
before the detection of the organism by repeated examinations of
smears. In seven secondary compensated cases positive sputum
was detected on an average nine months before death.
It is impossible to indicate what yearly incidence of silicosis
among miners in these areas may be expected. The arrangements
for examinations have not been completed for a sufficient length
of time to warrant conclusions.
APPLICANTS FOR EMPLOYMENT

The number of rejections on physical examination with X-rays,
varies from area to area, from 5 to 10 per cent, of those sent from
the mine employment office. This percentage is very low compared
with South African experience, but may be influenced by the form
of certificate, which certifies only " to freedom from tuberculosis "
without reference to fitness for underground work, although in
the examinations this may be taken into account.
In one area, where the numbers employed have largely increased
recently, among 4,700 examinations of applicants in two and a half
years, there were 22 cases of ante-primary silicosis and one case
of secondary silicosis, all from outside Ontario. In this respect,
examinations have acted as a protection against claims on mines
operating in Ontario, for which they are not responsible.

326

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CONFERENCE

SIMPLE TURERCULOSIS

The Survey of 1925 and 1926 involved single physical
examinations with stereoscopic X-ray films, so that there was no
opportunity to determine definitely the presence of tuberculosis in
suspected cases. Most of the men examined had been employed
in mines in Ontario for over five years.
TABLE IV.

INCIDENCE OF " SIMPLE TUBERCULOSIS " ON SURVEY
OF GROUPS OF MINERS IN 1 9 2 5 AND

Mining area
Porcupine
Kirkland Lake
Cobalt
Sudbury

1926

Number of examinations

Cases of tuberculosis

236
280
398
306

10
8
10
5

Reference to the report by Hague and McBain on the findings
in the first year's examinations at Porcupine shows under tuberculosis that the first two groups designated those " showing
positive sputum " and those " showing a definite risk " taken
together, and the last two groups, those " with slight risk " and
those with " apparently non-significant peribronchial tuberculosis "
taken together present a relative incidence among employees and
among applicants expressed as 2 : 1. The group of employees
" showing positive sputum " and " showing definite risk ", were
2.6 per cent, of those already employed.
In this area, in 1929, after two periodic examinations among
2,330 employees, there were 6 cases of simple tuberculosis, similar
to the yearly incidence among European miners in South African
gold mines. Three of them were Finlanders.
In Kirkland Lake, in 1929, among 1,800 first examinations of
employees, there were 12 cases of simple tuberculosis.
In Cobalt, in 1929, among 662 first examinations of employees,
there were 5 cases of simple tuberculosis.
In Sudbury among 1,434 first examinations of employees in 1927
and 1928, there were 23 cases of simple tuberculosis. In 1929,
among 1,958 examinations of employees there were 4 cases of
tuberculosis. In this area among 4,700 applicants, there were
149 cases of tuberculosis, and suspected tuberculosis.
Tuberculosis is not compensatable. There can be little doubt that

327

SILICOSIS IN CAÑABA

as the importance of dust and tuberculosis in the mines has been
more generally recognised, a number of men with tuberculosis or
suspected tuberculosis have discontinued underground mining
before the initial examinations were completed.
In an investigation by the Commonwealth Department of
Health, among 4,067 gold miners in Western Australia (Kalgoorlie),
there were 0.3 per cent, with simple tuberculosis.
The Report of the Technical Commission of Enquiry to investigate
" the prevalence of miners' phthisis and pneumonoconiosis in the
metalliferous mines at Broken Hill " showed 1 per cent, of underground miners with simple tuberculosis.
In New South Wales, of 716 men examined, not all miners but
with some exposure to silica dust, there were 16 cases of simple
tuberculosis (2.2 per cent.).
In Bulletin No. 162, the United States Public Health Service
reports the tuberculosis rate for all ages among 10,000 male
industrial workers as 2.5 per cent, and among foundry workers
as 1.9 per cent.
TABLE V.

COMPARISON OF MORTALITY STATISTICS OF " UNDER-

GROUND

MINERS

AND

ALL

MALES

OVER

YEARS " ,

1925 TO 1929, BY AREA

Mining
area

Porcupine
Kirkland
Lake
Cobalt
Sudbury

Estimated
AU males, proportion
Miners'
deaths,
deaths,
pulmonary
pulmonary tominers
adult
tubertubermale
culosis
culosis
population

Miners'
deaths,
all
causes

Miners'
deaths,
pneumonia

All males,
deaths,
pneur
moniá

22
6

Percent.
60
45

13
5

94 + 3 3 1
33

24
2

54
3

5
18

25
55

4
3

5
7

12
54

54
46

One accident.

The figures are small. Sanatorium deaths from tuberculosis are
allotted to the area from which admission to the Sanatorium was
made. The proportion of the population in the lower age group
is probably higher in these areas than in most communities. No
important increased proportionate mortality is shown to exist
for tuberculosis. • It is high for pneumonia in Porcupine.
The available information suggests that there are no important

328

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CONFERENCE

variations in the number of cases of simple tuberculosis from one
area to another and t h a t there is no marked increase in these miners
over those employed in mines elsewhere or in other heavy trades.
TUBERCULOSIS

IN CHILDREN

MINERS

In the course of one of the clinics conducted by Dr. G. C. Brink,
of the Tuberculosis Section of the Preventable Diseases Division
of the Department of Health, there were examined 73 children in
the centre of the Porcupine area. Forty-six of these were t h e
children of miners. There was among them one child with positive
tuberculosis and 19 showing a positive tuberculin reaction. These
children were between the ages of one and fourteen.
Among
27 children whose fathers were not miners, there were 8 showing
a positive tuberculin reaction.

COST OF SILICOSIS IN MINERS

An ante-primary case is awarded $500, a primary case $1,000,
and a secondary case, total disability. For total disability, the
workman receives 66 2 / 3 per cent, of his previous wages, medical
and hospital care. In the event of death, a pension is paid in
accordance with the number of dependants.
Ninety-one ante-primary, 58 primary and 33 secondary cases of
silicosis, of which 18 have died, have cost $268,356. Of this amount
$111,196 was for the death claims. In addition, there has been set
aside $282,500 for continuing claims and $69,000 for claims reported
but not adjusted.
CONTROL OF DUST

The Mining Act of the Province of Ontario requires the control
of dust underground.
Every dusty place where work is carried on in a mine must be
adequately supplied with clean water under pressure. In a few
mines, wet conditions prevail naturally, but in all mines, stopes,
raises and drifts are kept wet. The use of wet drills since 1924
has been compulsory and water is used in collaring holes.
Attempts are made to limit dust generated in handling ore
by the suitable location and design of ore passes. On account of
climatic conditions, hoisting shafts are necessarily upcast shafts,
thus the dust created at ore passes is carried up and out of the mine,

SILICOSIS IN CANADA

329

instead of being distributed through it. Canvas screens continuously
supplied with water have been used in front of ore pass openings.
The Mining Act provides that the times for blasting shall be
so fixed that the workman shall be exposed as little as possible to
dust and fumes. As a rule, blasting is done at the end of the
second shift so that the mine is idle until the first shift of the next
day comes on duty. After blasting, a small amount of water is turned
into the air lines which are operated to blow out the fumes, thus
a mist is created which assists in carrying down dust. This is
looked upon as one of the most important measures that have been
adopted from the standpoint of both fumes and dust.
In some cases, blasters are using masks of the filter type.
Dust counts made of samples of air from within these masks have
shown an important reduction in the count.
The rock temperature with the depth reached has not risen
above 67° F., so that heat is not a problem in these mines. Relative
humidity is about 95 per cent. In winter, the difference in temperature at the surface and underground favours natural ventilation.
In some of the mines, huge fans have been installed in shafts,
delivering from 150,000 to 250,000 cubic feet of air per minute
giving a linear velocity up to 8 miles an hour in drifts. These fans,
on account of climatic conditions cannot be operated during the
winter except where the air is led into the mine through old workings
not in use. Auxiliary fans delivering fresh air through canvas or
metal tubing to development faces are widely used. In one instance,
a special shaft has been built for forced ventilation and in another,
a special compartment in a shaft has been set aside to assist natural
ventilation in the removal of fumes and dust.
GRANITE

CUTTERS

In Ontario in 1924, there were examined 110 men quarrying and
crushing rock for use in the manufacture of ferro-silicon. The free
silica content is high. The exposure in most cases was limited to a
few years for the summer months only.
There were 5 ante-primary and 3 secondary cases of silicosis,
all but one having had exposure elsewhere. The single case referred
to had exposure at the crusher for four years of six months each,
and none elsewhere. At the time of examination, three months
before his death, there was dyspnoea, marked on exertion, poor
expansion with indrawing of the intercostal spaces and evidence

330

PAPERS PRESENTED TO THE CONFERENCE

of consolidation in the upper portion of both lungs. The
X-ray presented massive consolidation to the fourth rib anteriorly
on each side with less dense shadows and mottling in the fourth and
fifth interspaces. Pathological examination revealed a massive
fibrosis of silicotic type in the upper two-thirds of both lungs.
The case has been fully reported by Dr. A. R. Riddell in an article
entitled " A Case of Silicosis with Autopsy ". Further examination
of this case, showed the presence of small tubercles in the spleen,
and the cell reaction suggests that the lung was involved.
At this time, 1924, silicosis was compensatale only as " miners'
phthisis in mines ". Locally, such a situation left operating
companies open to civil suit for silicosis contracted in other
industries.
In 1925, in Ontario, provision was made for the compensation
of cases of stone workers' or grinders' phthisis in quarrying, cutting,
crushing, grinding and polishing of stone or grinding or polishing of
metal. In 1926, pneumonoconiosis was added to the list of compensatable diseases to apply to the same industries as stone workers'
or grinders' phthisis. The difference lies in interpretation of the
Act. The presence of silicosis with active tuberculosis and positive
sputum is required under grinders' phthisis.
Exposure of granite cutters in this Province is mainly from the
dust from Barre light granite, Quebec Stanstead granite, Georgia
granite and Balmoral red granite. The first three contain about
35 per cent, free silica. Many of these granite cutters have cut
sandstone or been exposed to dust from the sandblast.
A few dust counts, made with the Palmer Spray apparatus,
have shown big variations at the breathing level of workers using
different kinds of tools. With the use of the heavy picker for
surfacing, counts ran from 106,000,000 to 220,000,000 particles of
dust (not Si0 2 alone) under 10 microns in size, per cubic foot of air.
The shop air away from these tools was usually under 5,000,000
particles per cubic foot. No detailed study of dust content of air
was made.
In 1928 and 1929, the Industrial Hygiene Division conducted
examinations of 133 granite cutters with over fifteen years'
experience in the trade, with the results shown in table VI.
There are roughly 500 granite cutters in the trade in the Province,
so that the accumulation of cases is not high. Attention is rather
arrested by the number of granite cutters who have worked
twenty years or more at the trade without presenting more than
an increase in fibrosis of the lungs, producing no symptoms. The

331

SILICOSIS IN CANADA

proportion of complicated cases to total cases is high compared
with that found in the survey of miners.
TABLE VI

Average years of exposure
Stage of silicosis

Ante-primary
Primary
Secondary

Number of cases

19
5
10

In Ontario

Elsewhere

20.6
27.6
19.3

11.1
4.5
13.1

It is interesting to note that these cases present findings on
physical examination with X-rays, which make it possible to divide
them in accordance with the classification of ante-primary, primary
and secondary. The secondary cases reported, with one exception,
were cases of silicosis and tuberculosis. Only a few of them
presented massive consolidation similar to that described as
occurring among Barre, Vermont, granite cutters. While some of
the secondary cases have died, none have come to autopsy.
The shops are, as a rule, small, frequently with only one or
two cutters, so that most of them do all types of work. Many of
these shops have indifferent exhaust equipment for the removal
of dust, especially from surfacing machines. The work is done
under dry conditions and the floors are covered with rock dust.
In March 1929, the Silicosis Act for the " better prevention of
silicosis among stone workers " was passed in Ontario. This Act
requires examination on employment and periodic examination
of granite cutters. The details for these examinations have not
yet been arranged. The Factory Inspection Branch of the
Department of Labour will supervise appliances used for the
control of dust when this Act comes into force.
A positive pressure mask, devised by Dr. F. M. R. Bulmer, of the
Division of Industrial Hygiene, is in fairly widespread use among
granite cutters. It is easily adjusted, comfortable and inexpensive.
Suitable cloth is held over the face by rubber bands which tie
behind the head. It is ballooned with filtered air, from a compressor, which escapes from the sides and front of the mask to keep
it cool and to prevent inspiration of dust or fumes. It is not
intended as a substitute for the mechanical control of dust.

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TABLE VII.

A FEW ADDITIONAL CASES REFERRED TO THE DIVISION
FOR EXAMINATION

Occupation

Stage of silicosis

Sandblaster
Moulders

Grinders

Number
of cases

Secondary
Primary
Primary
Secondary
Ante-primary

1
1
1
1

Primary

Primary
Secondary

1
1

Average years' exposure

15
40
23
12
j 2 % (sandstone)
Í sy2 (artificial)
I 8 (sandstone)
f 5 (artificial
grindstone)
40 (sandstone)
12 (sandstone)

These were all cases with nodular fibrosis, and considered with
other cases reported, having various types of exposure to silica,
suggest that the inhalation of dust, for a period, containing free
silica alone, may determine the widespread distribution of fibrosis.
In the course of investigation of hazards to health in other
industries, the following physical examinations with X-rays, of
interest in reference to silicosis, have been conducted.
TABLE VIII. —• EXAMINATION

OF WORKMEN EXPOSED

TO DUSTS

OTHER THAN SILICA

Industry

Cement workers
Brick a n d tile workers
Grain elevator workers
Artificial abrasive, manufacture a n d use (silicon carbide and aluminium oxide)

Number
of men
examined

Average
years'
exposed

26
34
68

19
19.3
16.7

7.9

Approximate
SiOa

Physical
flndings

Percent.
1
1-10
3

No silicosis
No silicosis
No silicosis

0.3

No silicosis

i Twenty-seven of these 68 men had an average exposure of thirteen years.
PHYSICAL EXAMINATION

FINDINGS

In Ontario miners the symptoms present in the ante-primary
stage of silicosis have been an irritating cough, frequently in the
morning, with shortness of breath on moderate exertion, rather
more than is expected. On examination there have been no

SILICOSIS IN

CANADA

333

characteristic signs. Frequently, there is diminished expansion,
sometimes very marked, with slightly diminished resonance in the
upper two-thirds of the chest and breath sounds diminished and
sometimes slightly higher-pitched, no appreciable change in voice
transmission. As the condition progresses, these symptoms and
signs are emphasised, that is, diminished resonance, high-pitched
breath sounds with apparent shortening of the inspiratory phase
compared with expiration. Rales are seldom heard unless tuberculosis complicates the condition. The X-ray presents increased
hili shadows and linear markings with diffuse mottling, frequently
more marked in the inner and middle zones on the right side.
The advent of tuberculosis has manifested itself by an aggravation of existing symptoms and others common to tuberculosis,
and in the X-ray by a less discrete outline to the nodular shadows
with local conglomeration, usually in the upper third of one or
both lungs.
Among the granite cutters, after a much longer exposure to dust
containing free silica, the manifestations of the disease were much
the same as in miners, contrary to the experience of Jarvis 1 and
later, Russell2 with Barre, Vermont, granite cutters. Rather than
a massive local fibrosis suggesting itself by the physical signs,
decreased expansion, diminished resonance, high-pitched breath
sounds and diminished voice transmission limited to one area
bilaterally, with corresponding conglomerate shadows in the X-ray
and the remainder of the lung fields fairly clear, the distribution of
fibrosis in the Ontario cases, as a rule, has been the same as that
presented by the miners, although the linear markings often cast
deeper shadows and discrete nodules are more common in the hili
shadows, probably associated with longer continued exposure to
dust. However, in a few cases, more frequently in granite cutters
than in miners, localised conglomerate shadows extending from
the hilum outward and upward appeared as the important X-ray
manifestations of the disease. The other physical findings in such
cases were localised.
When tuberculosis supervened even in these cases, it was usually
apical and not basal, as in the Barre, Vermont, granite cutters.
1
D. C. JARVIS: "A Conception of the Chest Röntgen-Ray Densities Based
on a Study of Granite Dust Inhalation." American Journal of Roentgenology,
April 1922, Vol. IX, No. 4, p. 266.
2
A. E. RUSSELL: The Health of Workers in Dusty Trades. [2. Exposure to
Siliceous Dust (Granite Industry).] United States Public Health Bulletin
No. 187.

334

PAPERS PRESENTED TO THE CONFERENCE

PATHOLOGY

The pathological findings in some of these cases have been
discussed by Riddell and Rothwell in " Some Clinical and Pathologic
Observations on Silicosis in Ontario ".
Here observations were made corresponding to those described
by South African workers as the basis for their classification of
cases. Attention is drawn to atypical cases in which there was
widespread invasion of lung tissue by fibrous tissue without palpable
nodules but with " fibrous whorls " in microscopic section.
In these cases, there was moderate exposure to free silica and
the ash of the lungs showed a comparatively high silica content.
The marked difference between the silica content of the ash
of lungs in adults not especially exposed to silica dust and t h a t
among miners is indicated, with a description of the gravimetric
method used for the chemical determinations. Since that time,
E. J. King, reporting difficulty with the use of Isaacs' method for
the estimation of silica in tissue, described a micro method for this
purpose which depends on the production of yellow silicomolybdic
acid, which gave accurate results.
Studying these with other lung specimens, T. H. Belt, at work
in the Pathological Department of the University of Toronto,
reported in " Silicosis, Its Pathology and Relation to Tuberculosis "
the result of a comparison between the silica content of the ash
of the lungs of silicotics and the number of particles of silica to be
seen in adjoining portions of the same lung with the polarising
microscope.
The invisible portion designated " occult silica " was greatest
where fibrosis was most extensive, i.e. few particles to be seen, a
high silica content on chemical examination, and extensive fibrosis,
are related. This appears to support the theory of Gye and
Kettle t h a t crystalline silica produces its ill-effects on account of
a slow chemical change, probably to colloidal form.
No silica particles were noted in the fibrotic nodules, but they
appeared in the zones surrounding these nodules, which were
occupied by young fibroblast and endothelial cells. With few
or no silica fragments, the presence of a healed lesion suggested
the absence of any irritant and the assumption that the silica by
this time has changed to silica gel. With this conception of the
sequence of events, fibrosis will continue for some time after
exposure has ceased, until the silica already in the lung has been

SILICOSIS IN CANADA

335

rendered innocuous. This is noted in explanation of the clinical
progress which takes place in uncomplicated silicotic cases after
removal from exposure to silica.
In the cases with tuberculosis, the fibrous nodules largely escaped
caseous necrosis, but the zone surrounding them in which the
silica particles lie was necrotic and without any evidence of cell
reaction except at its edge. Extensive cell reaction occurred
in the normal lung and away from the fibrotic areas. So t h a t
it is inferred that tuberculosis gains a foothold in the areas
surrounding the fibrous nodules called " silica nests ", and that so
long as these areas have not become fibrosed the increased
liability to the spread of tuberculosis infection exists.
G. C. Cameron, associated with the Banting and Best Chair of
Medical Research, has .been good enough to abstract for this
summary an unpublished paper describing " An Experimental
Study of Elimination of Silica from the Lung ", 1 January 1930:
The work was based upon the observation personally conveyed by
Professor Oskar Klotz that the lung alveoli of anthracotic subjects
dead of pneumonia often contained many phagocytes which were
heavily laden with carbon. We sought therefore an agent which upon
introduction to the air spaces of the lungs would promote emigration
of phagocytes and at the same time be innocuous to the subject. It
was presumed that the emigrating phagocytes would carry with them
their previously ingested content of silica.
It was found that rabbits might be enclosed in a chamber the
atmosphere of which was heavily charged with paraffin oil in droplet
form, as discharged from an atomiser. Prolonged exposure of several
hours daily did not seemingly impair the health of the animals.
Histologic study of the lungs of such animals showed that exposure
for an hour sufficed to disperse oil widely throughout the lungs, and
that oil could be demonstrated in the lungs as long as fifteen weeks
after the cessation of exposure. The oil promoted very active emigration of phagocytes to the alveoli, from where it was presumed they
were expectorated with a full capacity of oil. Oil was observed in the
parenchyma of the lungs in only one of the twenty-seven rabbits
exposed. In this instance, the oil was evidently being conveyed along
the lymph channels and was demonstrable in small amounts in lymph
nodes. In none of the animals did the oil occasion fibrosis that might
occlude air spaces.
Rabbits exposed to an atmosphere highly charged with finely particulate quartz dust both before and during the exposure to oil spray
were killed, and the lungs examined histologically and chemically.
The production of histologically demonstrable silicosis was not achieved
during the period of observation and chemical estimation of silica in
the lung by the colorimetrie method of King1 did not indicate that elimination of silica from the lung, in the sense of complete expectoration,
1
E. J. KING: " Estimation of Silica in Tissues. "
Chemistry, 1928, Nov. 1928, p. 25.

Journal of Biological

336

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was accomplished. As the chemical procedure would not differentiate
between silica in the tissue and silica in the air spaces, however, it
was felt that this result did not indicate complete failure of the method.
The process of elimination of particulate foreign matter from lung
parenchyma by administration of oil spray was demonstrated by
experimentation with carbon. Rabbits were made anthracotic by
intravenous administration of India ink and then subjected to oil
spray. The air spaces of the lungs of these animals contained many
cells which had ingested both carbon and oil, apparently to the limit
of their capacity. Lungs of control animals untreated by oil showed
absence of phagocytes in the air spaces but very many cells heavily
laden with carbon in the parenchyma. The lungs of animals intensively
treated with oil showed microscopically some months after cessation
of treatment approximately as much carbon as the untreated controls,
so that the practicability of oil spray as a therapeutic measure was
not proven. Experiments are proceeding.

SUMMARY

(1) The cases reported indicate that silicosis, as defined by the
standards of the Miners' Phthisis Medical Bureau of South Africa,
is contracted in gold mining in Ontario. The number of cases
in proportion to the number employed underground is not high,
but the time required for the development of these cases is relatively
short. The proportion of silicosis cases complicated with tuberculosis is high.
(2) The number of cases and deaths from simple tuberculosis
is little, if any, higher than that found in mines elsewhere.
(3) Granite cutters in Ontario develop silicosis with manifestations similar to those presented by Ontario miners. The proportion
of cases found during the survey of those employed at the trade for
more than fifteen years, is low, having in mind the skilled nature of
the employment and the consequent high percentage with long
service. The period of exposure to silica dust in all cases is long.
The proportion of silicosis cases complicated with tuberculosis
is high.
*
*
*
The writer wishes to acknowledge valuable assistance in the
preparation of this summary from :
Mr. V. A. SINCLAIR, K.C., Chairman, and Mr. T. N. DEAN, M. A.,

F. S. S., Statistician, Workmen's Compensation Board, Ontario.
Dr. N. H. RUSSELL, Dr. E. A. MORGAN and Dr. R. W. MCBAIN,

Examining Physicians in the mining aseas.

SILICOSIS IN CANADA

33 7

Professor 0 . E. KLOTZ and Dr. T. H. BELT, who has examined

and reported in detail for the Department on the pathological
specimens submitted to the Department of Pathology, University
of Toronto.
Dr. G. C. CAMERON, Banting and Best Chair of Medical Research,
University of Toronto.
Dr. A. R. RIDDELL and Dr. G. C. BRINK, of the Silicosis Referee

Board, Province of Ontario, and Mr. S. J. MANCHESTER, Director,
Division of Vital Statistics, Department of Health of Ontario.

BIBLIOGRAPHY

ELLIOTT, J. H. " Silicosis in Ontario Gold Mines ". Canadian
Medical Association Journal, Oct. 1924.
HAGUE, 0 . G. and MCBAIN, R. W. " Silicosis as an Industrial
Hazard in Ontario Gold Mining ". American Journal of Roentgenology
and Radium Therapy, Vol. XVIII, No. 4, Oct. 1927, p. 315.
. RIDDELL, A. R. " A Case of Silicosis with Autopsy ". Canadian
Medical Association Journal, 1925, Vol. XV, p. 839-841.
and ROTHWELL, H. E. " Some Clinical and Pathologic Observations on Silicosis in Ontario ". Journal of Industrial Hygiene,
Vol. X, No. 5, May 1928, p. 147.
BELT, T. H. " The Pathology of Silicosis of the Lung ". Canadian
Public Health Journal, Vol. XX, No. 10, Oct. 1929, p. 494.
KING, E. J. '" The Estimation of Silica in Tissues ". Journal of
Biological Chemistry, Vol. LXXX, No. 1, Nov. 1928. p. 25.

This Bibliography is limited to Canadian references.
22

338

PAPERS PRESENTED TO THE CONFERENCE

APPENDIX

The Workmen's Compensation Board

THE MINING ACT

ONTARIO

CERTIFICATE OF

This certifies that I have examined

FREEDOM FROM PULMONARY
whose photograph is attached hereto
and have found him free from tuberculosis of the respiratory organs.
If required by the Manager or
Superintendent, this certificate shall
be delivered to him, and shall remain
in his custody until the holder is
discharged.

TUBERCULOSIS
Serial Number

Date

Name
Address

DATE OP INITIAL EXAMINATION

Nationality
Married

Single

Age.

1. Date due for re-examination

Signature of Workman
Examined— • Doctor's Signature
2. Date due for re-examination
Personal Photograph
Full Face View
Photograph to be also signed

Examined—

Doctor's Signature

3. Date due for re-examination
Examined—

Doctor's Signature

N. B. — The holder of this certificate must be re-examined not later than twelve months from
date of initial examination, and annually thereafter.

SILICOSIS IN GERMANY

I. — PRESENT STATE OF THE SILICOSIS PROBLEM
IN GERMANY
BY

PROFESSOR A. BÖHME, BOCHUM

INTRODUCTION

The exposition of the present state of knowledge relative to
the silicosis problem in Germany should be preceded by a short
discussion of the principal features of its development in our
country. Only a few names need be mentioned. The first German
author to deal with injury to the lungs of miners caused by inhalation of dust, and to designate such injury as an occupational
disease, was Paracelsus, who, about 1534, published his work
entitled Miners' Phthisis and Other Miners' Diseases. In the second
half of the nineteenth century, German pathologists and clinicians
made considerable progress in regard to research connected with
diseases caused by dust.
Zenker 1 provided the anatomical, and Kussmaul 2 the chemical,
proof of the deposit of inhaled dust, especially silicic dust in the
lungs. The name pneumonoconiosis was invented by Zenker, who
described in detail the anatomical picture of the dusty lung.
Merkel 3 studied the tubercular changes in siderotic lungs. The
fundamental experimental and anatomical research engaged in by
Arnold 4 constituted considerable progress.
He succeeded in
producing experimental dust fibrosis of the lung, and in distin1
2

ZENKER, in Deutsches Archiv für klin. Med., 1866, Vol. II.
KUSSMAUL, ibid., Vol. II.

MERKEL, ibid., 1887, Vol. XLII.
* ARNOLD: Untersuchungen über Staubinhalation
Leipzig, F. C. W. Vogel, 1885.

und

Staubmetastase.

340

PAPERS PRESENTED TO THE CONFERENCE

guishing clearly between that and tuberculosis.
Eulenberg x
definitely affirmed that silicic acid causes serious fibrotic disease
of the lungs.
A close connection between the inhalation of dust with a quartz
content and tuberculosis has been revealed repeatedly by statistical
data : Oldendorff 2, Sommerfeld 3, Moritz and Ròpke 4 and others
draw attention to the high mortality rate from tuberculosis amongst
metal grinders; Lewin (1863), Hirt 5 , Wilbrandt 6 , Eulenberg,
Sommerfeld7 and others to similar conditions amongst pottery
workers.
For extensive hygienic research relative to the dust content of
the atmosphere, to the deposit of dust, to the self-protecting
mechanism of the system against injury due to the dust, we are
indebted to Lehmann and his collaborators 8.
CLINICAL PICTURE OF SILICOSIS

The clinical picture of the silicotic lung could only be studied
in the case of very advanced disease forms prior to the introduction
of Röntgen ray examination. Bäumler 9 describes the symptoms,
and lays stress on the cirrhotic character of the accompanying
tuberculosis.
The accurate diagnosis of silicosis during life, as well as in its
early stages, and investigations relative to its incidence in the
several occupations involving exposure to this risk, as well as a
study of its development, were only rendered possible by the
introduction of the Röntgen diagnosis. On the basis of earlier
discoveries, Staub-Ötiker 10, the next writer to describe in
detail the radiographic picture of the silicotic lung as found in
metal-grinders, also distinguished the various stages of the disease.
Numerous further radiographic and clinical studies have since been
effected. Comprehensive expositions of the subject are provided
1

E U L E N B E R G : Handb. d. Gewerbehyg. Berlin, 1876.
O L D E N D O R F F , in Zentralbl. f. aligera. Gesundheitspfl., 1882.
SOMMERFELD, in Beil. z. Hyg. Rundschau, V I I . J a h r g . , N o . 1, 1897.
* MORITZ and R Ò P K E , in Zeitschr. f. Hyg. u. Infektionskrankh.,
Vol. X X X I .
6
H I R T , in Krankheiten der Arbeiter, Vol. I. Breslau, 1871.
« W I L B R A N D T , in Vierteljahrsschr. f. gerichtliche Mediz., Vol. X X I V .
7
SOMMERFELD, in Deutsche Vierteljahrsschr. f. öffentliche Gesundheit, 1893,
Vol. X X V , N o . 2 ; Handb. d. Gewerbekrankheiten, Berlin, 1898.
8
L E H M A N N , in Archiv f. Hygiene, Vol. L X X V ; also in Arbeits- u. Gewerbe2

hygiene,

Leipzig, 1919; L E H M A N N , SAITO a n d G E F R Ö R E R , in Archiv

Hyg.,

Vol. L X X V .
9
BÄUMLER, in Münch. med. Wochenschr., 1909, N o . 10.
10
S T A U B - Ö T I K E R , in Deutsches Archiv f. klin. Med., 1916, Vol. C X I X .

SILICOSIS IN GERMANY

341

by Stähelin 1 , Ickert 2 , Jötten and Arnoldi 3 , Lehmann-EngelWenzel 4 . The lines followed by the above researches are somewhat
as follows:
In very many dusty trades, as, for instance, among bakers and
millers, who suffer from bronchitis, often amongst coal miners
(hewers), and likewise in the initial stages of silicosis, there is found
an enlargement and mottling of the hilar shadow, thickening of
the trunk shadows proceeding from the hilus, intensifying of the
outline of the lungs which reaches to the border of the chest and
shows arborification, giving a picture resembling a network, with
prominence of the bronchial tubes in the form of longish cavities
with a double-edged border. From the anatomical point of view
such a picture corresponds to a type of bronchitis.—a filling-up
of the peribronchial and perivascular lymph cavities with coal
dust, without fibrosis; also eventually to an initial dust fibrosis
of the lung.
Such a picture is found, for instance, frequently amongst
rockdrillers in coal mines, where, associated with initial fibrosis,
there is found considerable deposit of coal dust in the lung.
Among cement workers, polishers in the knife-grinding industry,
and coal miners (hewers), this picture is very frequent. Symptoms
are not as a rule associated with these slight modifications unless
there is bronchitis. The pictures above described do not indicate
silicosis.
Where definite fibrosis develops, the knots of the reticulated
area are seen to thicken, the single outline of the lung resolves
itself into small round spots which are partly ranged one behind
another like beads in a necklace, or there may be seen, quite apart
from the outline of the lung, various small spots within the lungs,
at first more especially in the centre, but which gradually invade
and cover the outline of the lung. This picture is characteristic
of dust fibrosis, as met with more especially after inhalation of
quartzitic dust, but possibly also after deposit of coal dust or
graphite.
With the development of the disease, the fine mottling spreads
over the lungs in an almost symmetrical manner, though the right
side is somewhat earlier and more intensely involved than the left.
1
STÄHELIN, in Handb. d. norm. u. pathol. Physiologie, Vol. I I , p. 515.
Berlin, 1925.
2
I C K E R T : Staublunge u. Staublungentuberkulose.
Berlin, 1928.
3
J Ö T T E N and A R N O L D I : Gewerbestaub- u. Lungentuberkulose.
Berlin, 1927.
* L E H M A N N - E N G E L - W E N Z E L : " D e r S t a u b in der I n d u s t r i e " , Beiheft z.
Zentralblatt f. Gewerbehyg. u. Unfallversicherung,
Vol. I X .

342

PAPERS PRESENTED TO THE CONFERENCE

The apical zones are usually less affected than the other parts of
the lung, but in the end they also generally become involved.
According to the nature of the dust, the Rontgen slides reveal at
this stage certain differences. According to Kaestle, the mottling
shows deeper shadows and sharper edges the higher the quartz
content of the dust. He has thus observed a specially intensive
mottling in workers engaged in sandstone quarries; such pictures
are also met with in the case of steel-grinders, who work with wet
sandstone. The mottling becomes gradually more intensive and
larger, but the spots seldom exceed a few millimetres in diameter.
They may in places be so thick as to appear to overlap.
Regarded from the anatomical point of view, the small spots
cluster round fibrotic foci, with a rich dust content which in their
central zone are mostly transformed into hyaline. Signs of infection, especially of a tubercular nature, are not in general to be
found in these small nodules. With the developing thickness of
the fine mottling, the elasticity and vital capacity of the lung
becomes reduced, and there arises a certain amount of dyspnoea
on effort (Arbeitsdyspnoe). A dry cough is often met with; sounding
reveals, however, bronchitic respiration only in a fraction of the
cases*—at least where stonecutters are concerned. The percussion
note (Klopfschall) is as a rule hardly worth considering. Where
the radiographic picture reveals special thickening of the fine
nodules, the sound may in this region be somewhat shortened, as
for instance, where the side, in the axillary region or the interscapulary region is heavily involved. In some forms of silicosis
bronchitis appears to play a rather important part.
In the further development of the disease, there are recognised
on the Röntgen plate, large, dense, circumscribed masses of shadow,
often enclosed by sharp edges, which frequently develop symmetrically, but also at times asymmetrically. Favoured situations
for these massed shadows are the sides of the infraclavicular regions
on each side, and also those parts which project in a lateral direction
from the hilus. These masses of shadows with large mottling may
become greatly extended in the course of a few years and finally
cover the greater part of the lung.
It is especially the middle and upper parts of the lung which
generally become filled with these masses of hard cicatricial tissue
showing a strong tendency to shrinkage, whilst in the lower parts
of the lung there develops a marked secondary emphysema to
which the indurated changes formerly present there gradually give
place. Descending trunk shadows reaching from the large shadow

SILICOSIS IN GERMANY

343

masses down to the diaphragm, and intense displacement of the
diaphragm complete the picture. Ultimately it not infrequently
happens that an enlargement of the heart is established radiographically. With the increase in indurated phenomena there sets
in also marked diminution in the percussion note (Klopfschall),
modifications of the respiratory murmur, which may at times
be softer and at times harsher. Rales are then usually rare. The
capacity for chest expansion and for displacement of the border
of thelungs, as well as the vital capacity, become gradually reduced
until finally dyspnoea occurs on the slightest movement or even
while the patient is at rest. Expectoration is often entirely absent
even in these serious stages of the disease. The temperature is
normal. Finally, there may occur marked symptoms of cardiac
insufficiency with stasis of the pulmonary and general circulation.
This state is responsible for the death of the patients. Clinically
the picture presented up till the end in such cases is that of the
purely silicotic lung.
Anatomically there may be found a fibrotic, in part hyaline,
tissue which reveals no signs of tuberculosis infection, and likewise
in animal experiments shows no connection with tuberculosis. In
yet other cases, even when during life no symptoms of
tuberculosis, were present, post-mortem examination reveals at
the same time histological tubercular changes, and it may ultimately
occur that the histological examination reveals no tuberculosis,
whilst animal experiment and cultures show positive results. The
possibility must therefore be admitted that, at least in some of the
fibrotic cases showing large nodules but developing clinically,
without symptoms of tuberculosis, latent tuberculosis infection
nevertheless plays a part.

Very frequently there occur grave cases of silicosis in which,
after long observation, definite tuberculosis is seen during life tobe
associated with silicosis.
There are often seen on the Röntgen plate, showing finely mottled
silicosis, on one side in the upper part large spots with a tendency
to spreading and cavitation. Such areas almost always develop
later into overt tuberculosis. In the case of forms of silicosis with
large mottling it is often very difficult to tell from the Röntgen
picture whether overt tuberculosis is in course of development. A
preference for the apical zones, asymmetry of the thickening
processes, cavernous destruction and a small and vertical form

344

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of the heart, are indications of this state, but fairly often the
Rontgen picture provides no differential criteria.
Clinically, loss of weight, night sweats, reduced strength, fever,
occurrence of increased dullness, bronchial murmur, resonant rales
in the apical zones, acceleration in the sedimentation test, are
signs of active tuberculosis. Proof of the presence of the tubercular
bacillus is often provided by animal experiment earlier than
microscopically. A positive local and general reaction to tuberculin
may on occasion be of value for the diagnosis of an active form
of tuberculosis, but in general the tuberculin reaction and likewise
the complement fixation test is of no great diagnostic significance
in regard to the foregoing questions.
Koelsch x and Kaestle 2 designate the stage of fine mottling as
the first stage of silicosis, associated with slight dyspnoea after effort.
The second stage is connected with the formation of larger and
thicker foci and is characterised by increasing breathlessness,
pressure and stitch in the chest, dry morning cough and a tendency
to obstinate catarrh arising from cold.
To the third stage there belong forms with extensive and massive
shadows, clinically marked dyspnoea, strong intense fits of coughing
frequently accompanied by expectoration which is often slight,
pains in the chest and disturbance of the circulation. The above
distinctions have also been accepted by other research workers
(Von Döhren 3, Reichmann 4 and Schürmann 5). Still further
investigators have likewise distinguished three stages, which do
not, however, correspond to the above.
Thus where an exchange of views is desirable it is advisable—at
least so long as no uniform designation has been established—to
avoid the classification into first, second and third stages, and
preferable to designate the dominant characteristics of each stage.
COURSE CF THE DISEASE

Extensive observations in the various dusty trades are still
lacking in this connection. Böhme reports on the course of the
disease during a certain number of years (two to eight) as affecting
1

KOELSCH: "Schwere Staublungenerkrankungen",in Arbeit und Gesundheit,
No. 12, Ausdehnung der Unfallversicherung auf Berufskrankheiten, Berlin. 1929.
2
KAESTLE, in Fortschr. auf dem Gebiete der Röntgenstr., 1928, Vol. XXXVII.
3
VON DÖHREN: "Zur Klinik der Staublunge" in Die gewerbl. Staublungenerkrankung, Berlin, 1929.
4
REICHMANN: "Ueber die Begutachtung der Gesteinstauberkrankung", ibid.
6
SCHÜRMANN: "Gewerbestaub, seine Bekämpfung, usw.", ibid.

SILICOSIS IN GERMANY

345

150 stonecutters in the Ruhr coalfields. He confirms the gradually
deteriorating condition of many silicosis cases after quitting work
in dusty trades, observed by the South African investigators and
the frequent development of these into serious forms of open
tuberculosis. Of those showing incipient induration after two and
a half years, about 26 per cent, had grown worse, and in a third
of these active tuberculosis was confirmed. In cases of the typical
fine mottled stage of the disease, after about two and a half years
there was observed in 40 per cent, of the cases an increase in
induration, and about a third of these showed active tuberculosis.
Amongst those cases showing large hard masses of cicatricial
tissue there was altogether an increase of induration amounting
to 72 per cent., whilst overt tuberculosis was confirmed in half
of these cases. The presence of tuberculosis was often established
by means of experiments on guinea-pigs earlier than microscopically.
Where, in the case of serious modifications due to dust, overt
tuberculosis supervened, death usually occurred within a few years.
Also in the case of slight changes due to dust, overt tuberculosis
mostly followed a progressive course, though extensive improvements were also encountered. As a result of observation continued
for several years, it was not infrequently remarked how, together
with a state of general well-being, indurated centres gradually
suffered extension and suddenly revealed cavernous formation
with expectoration of the tubercular bacillus. Such observations
point to the fact that already at an early stage the tubercular
infection is latent in these indurated foci. Dust tuberculosis would
appear to develop often for a period of years in the form of slow
progressive indurated latent tuberculosis. The state of the patients
is characterised by general well-being and freedom from toxic
symptoms. Probably the blocking of the lymphatic channels
prevents rapid dissemination of the infection and resorption of
toxic substances. There finally occurs, nevertheless, in these
advanced cases, collapse of the tissue and overt tuberculosis. Only
in the minority of the cases does the process come to a complete
standstill. Also in the finely mottled forms of silicosis lengthy
observation often results in establishing definitely associated
tubercular infection. Radiographically, such cases are characterised
by forms showing larger apical or sub-apical foci, which mostly
reveal a decided tendency to progress.
Our continued clinical observations have resulted in confirmation
of the South African views as to the great significance of tuberculosis
in regard to the production and progress of serious forms of silicosis.

346

PAPERS PRESENTED TO THE CONFERENCE

On the other hand, clinical and anatomical investigations (see
below) lead to the view that even serious and extended processes
of induration may occur subsequent to the inhalation of quartz
dust alone, and that such processes may, even after the patient
has quitted the dusty trade in question, show continuous development up to a point at which, as a result of increasing pulmonary
fibrosis, cardiac insufficiency of the right heart occurs, which leads
to death by symptoms of stasis.
The association of silicosis and tuberculosis would often appear
to follow a more favourable development than in the case of the
stonecutters whom we had under observation. Kreuser reports
on pottery workers who for decades showed overt tuberculosis.
Holtzmann and Harms 1 and Roessle 2 speak of the benign nodular
development of dust tuberculosis amongst pottery workers.
Ickert 3 makes similar observations in regard to miners in the
Mansfeld ore district. .
ANATOMICAL RESEARCH

Since the research engaged in by Arnold, fibrosis due to dust
has in general been recognised as a disease sui generis and distinguished from tuberculosis. It has, however, been admitted on all
sides that very often tuberculosis is associated with dust fibrosis.
Nevertheless, the majority of Germans are of opinion that in this
case these two processes are to be sharply distinguished one from
another, and that dust inhalation, as such, may lead to extensive
pulmonary fibrosis without associated tubercular infection.
Schmorl 4 , Staub-Ötiker 5, Arai 6 , Koopmann 7, Böhme and
Schridde describe such cases of pure silicosis of serious development
in which careful macroscopic and microscopic examination yielded
no signs of tuberculosis.
Schridde 8 emphasises the histological similarity which exists
between dust fibrosis (stone) with cicatricial keloid, and modifications of the ulcus callosum ventriculi, and assembles these processes
1
HOLTZMANN a n d H A R M S : Zur Frage der Staubeinwirkung
au] die Lungen
der Porzellanarbeiter.
Tuberkulose-Bibliothek, 1923, N o . 10.
2
R O E S S L E , in Beitr. z. Klinik d. Tuberkulose, Vol. X L V I I , No. 2.
8
I C K E R T : Staublunge und Tuberkulose bei den Bergleuten des Mansjelder
Kupferschieferbergbaues.
Tuberkulose-Bibliothek, 1924, No. 15.
4

R O S T O S K I , S A U P E , S C H M O R L : Zeitschr. f. Krebsforschung,

1926, Vol. X X I I I .

S T A U B - Ö T I K E R , in Archiv f. klin. Med., 1916, Vol. C X I X .
6
A R A I , in Virchows Archiv, 1920, Vol. C C X X V I I I .
' KOOPMANN, in Virchows Archiv, 1924, Vol. C C L I I I , p . 423.
8
S C H R I D D E , in Klin. Wochenschr., 1928, p . 582.

SILICOSIS IN GERMANY

347

under the name of " keloidosis ".. He sees in keloidosis a particular
reaction of the connective tissue to simultaneous physical and
mechanical irritation in subjects with a special inborn susceptibility.
Böhme finds in about two-thirds of the sections 01 lungs affected
by dust an accompanying active tuberculosis, and in about onethird pure modifications due to dust without tuberculosis. In
several cases, designated anatomically as pure dust fibrosis of
serious development, the guinea-pig experiment gave negative
results. In one or two cases in which clinically and anatomically
no signs of tuberculosis were discerned, animal experiments and
culture of tuberculosis bacillus gave opposite results.
In opposition to these views, Ribbert 1 had at an earlier date
advanced an opinion that all indurated anthracotic nodules of
the lungs in the hilar lymph glands owed their production, not
to dust alone, but to simultaneous chronic infection, chiefly with
tubercular bacillus. Merkel 2 also has concluded from his anatomical
findings that simultaneous inhalation of dust and tubercular
bacillus occurs and that these exert a double action in the production
of the majority of dust fibrosis.
Hübschmann 3, similarly on the basis of histological research,
holds the opinion that at least all extensive processes of hard
cicatricial tissue in dust fibrosis are due, not to dust alone, but to
the simultaneous influence of the tubercular bacillus, and even in
cases in which small nodules are present, he found many to be of a
typically tubercular character, and alongside this, transition to
pure hyaline nodules, so that he also assumes tubercular aetiology
for small nudolar forms of the disease.
Ickert 4, like Mavrogordato, distinguishes two varieties of small
nodules: the majority are small fibrotic nodules, in the midst of
which a blood-vessel is situated. These he calls block nodules, and
attributes them to the influence of dust. Besides these nodules,
there are found nodules similar in formation to the so-called
" Puhl focii ", in connection with the production of which an
infectious agent plays its part. Thus, though opinions differ in
relation to the significance of tuberculosis in regard to the development of serious forms of dust fibrosis, it is nevertheless generally
recognised that fine nodular modifications may arise purely from
1

a
8

RIBBERT, in Deutsche med. Wochenschr., 1906, p. 1615.

MERKEL, in Deutsches Archiv f. Hin. Med., 1888, Vol. XLII.
HÜBSCHMANN, in ICKERT: Staublunge und Tuberkulose bei den Bergleuten

des Mansfelder Kupferschieferbergbaues. Leipzig, 1924.
* ICKERT: Staublunge und Staublungentuberkulose. Berlin, 1928.

348

PAPERS PRESENTED TO THE CONFERENCE

the effect of dust. It is likewise admitted that also in many cases
of serious silicosis, success has not attended any method of establishing proof as to the presence of tubercular infection, including also
animal experiment.
As a consequence of serious pulmonary fibrosis, there is often
met with in pure cases of lungs affected by dust a considerable
dilatation and hypertrophy of the right ventricle, and also symptoms of stasis in the general and pulmonary circulation. The
nutritional condition and the strength of the patient in such cases
often remains very good up till death.
Our workers in dusty trades are exposed to very considerable
injuries from dust, and there is therefore frequently found on dissection forms such as were frequently met with formerly in South
Africa, though at the present time as a consequence of the successful
campaign against dust, such forms have become much rarer in the
above-mentioned country.

It has always struck the workers in dust fibrosis research that
in cases of dust fibrosis complicated with tuberculosis very slight
specific tubercular changes are to be found in the areas containing
hard cicatricial tissue, and that the extensive fresh tubercular focii
are met with rather in those parts of the lung which are free from
fibrosis. Likewise in the bronchial glands there are often no large
tubercular modifications to be found.
Fränkel 1 has already
regarded as the cause of this phenomenon the block of the lymph
passages by dust induration, which prevents transport of the
tubercular bacillus and causes the tubercular process to be limited
for a long time to one spot, and to develop chronic induration.
Jotten and Arnoldi have confirmed by their animal experiments
this blockade of the tubercle bacillus. Roessle 2 attributes only
slight importance to the lymph block. He is rather inclined to the
view that a specific influence on the connective tissue peculiar
to silicic acid, is the cause of the fibrotic character of dust tubercles,
and is even in favour of the therapeutic application of silicic acid
as a remedy against pulmonary tuberculosis.
While the block of the lymph vessels on the one hand obstructs
the spread of the tubercular processes, on the other it hinders the
cleansing mechanism of the lung from acting in rejecting tubercle
1
F R Ä N K E L : Spezielle Pathol, u. Therapie der Lungenkrankheiten.
Berlin,
1904.
2
R O E S S L E , in B R A U E R : Beitr. z. Klin. d. Tuberk., Vol. X L V I I , 1921.

SILICOSIS IN GERMANY

349

bacilli and other infectious agents which have penetrated it, and
so provides, perhaps, the explanation of the increased tendency
of cases of dust fibrosis to develop tubercular infection (Fränkel).
SCHNEEBERG

LUNG

DISEASE

A disease of special character, connected with the inhalation of
stone dust, is the Schneeberg lung disease, a combination of dust
fibrosis and cancer of the lungs which has been frequently observed
amongst the miners in the Schneeberg Mines on the borders of
Saxony and Bohemia. As the researches of Rostoski x, Saupe and
Schmorl in confirmation of former observations prove, about
one-half of the older miners die of this disease. The condition in
question is pulmonary carcinoma, of slow and partly horny growth
inside the pneumoconiotic lung with metastases in the hilar gland
and partly also in other organs. Amongst the population of the
district not occupied' in the mines, such frequency of pulmonary
carcinoma is not met with, and it must therefore be induced by
the occupation in question. One condition necessary to its production is dust induration, but this is not the only condition. Frequency
of pulmonary carcinoma has, indeed, in the last decades, been by
many authorities (Von Hampeln, Schmorl2) stated to be related
to increase of dust due to industrialisation and traffic. It should,
however, be noted that in other industrial regions, as, for example
in the Ruhr district, in spite of the frequency of diseases due to
dust, complication with pulmonary carcinoma has hardly been
noticed. As a further condition for the production of pulmonary
carcinoma in the case of Schneeberg disease, there have therefore
to be taken into account certain properties of the ore extracted
there. The ore in question is chiefly cobalt and bismuth, with an
arsenic and radium content. It is just this mixture of arsenic and
radium which is perhaps of significance. It is recommended in
every case where ore with a radium content is extracted, that
attention should be paid to the possible presence of pulmonary
carcinoma. The practical importance of the Schneeberg lung
disease is at present not great, as the number of workers engaged
in the local mines is diminishing considerably, and hardly exceeds
fifty. Its theoretical interest, however, is all the more important.
1

Vol.
2

ROSTOSKI, SAUPE and SCHMORL, in Zeitschr. f. Krebsforschung, 1926,
XXIII.
VON HAMPELN, in Grenzgeb. d. Med. u. Chir., 1922, Vol. XXXVI.

350

PAPERS PRESENTED TO THE CONFERENCE

EXPERIMENTAL

SILICOSIS

Lehmann 1 and his pupils Saito, Gfrörer, and Katayama 2 proved
by animal experiment that about 50 per cent, of inhaled dust is
retained by the nasal mucous membrane. A further amount is
retained by the walls of the bronchial tubes, and withdrawn thence
by the action of the ciliated epithelium into the pharynx, whence
it passes into the digestive canal. Only 4 to 24 per cent, of inhaled
dust arrives in the lungs.
The older investigations in regard to experimental production
of pneumoconiosis, including those of Arnold, were mostly undertaken with very considerable quantities of dust, which greatly
exceeded those which have to be taken into consideration in
connection with human pathology. Acute injuries resulting from
dust were caused by these large amounts of dust, especially bronchopneumonia, which, at first of a secondary order, ultimately led
to fibrosis, which cannot be directly compared with human fibrosis
without further investigation. Pure inhalation experiments with
small measured quantities of dust gave—in the absence of infections
—hardly any, or very slight, reactive fibrotic processes.
Gross 3, using a mixture of soot and quartz dust for inhalation
in the case of rabbits, failed entirely to produce fibrosis. Lehmann
made cats and guinea-pigs inhale for a considerable time porcelain
dust in concentration similar to that inhaled in the porcelain
industry. In this case likewise no fibrotic changes took place.
Cesa-Bianchi 4 instituted experiments in regard to the signification
of simultaneous tubercular infection. The dust concentrations
used by him, though very considerable, were not, in themselves,
sufficient to produce notable histological modifications, apart from
a few cases of pneumonia. The animals previously subjected to
dust were thereafter infected with small amounts of weakened
cultures of the tubercular bacillus. These animals almost all died
of tuberculosis of the lungs of a grave form, whilst the infected
control animals which had not been previously subjected to dust,
showed no tubercular modifications, or very slight tubercular
affections. In these cases, tuberculosis was therefore obviously
favoured by dust inhalations. Chalk and gypsum dust had less
effect than grindstone dust and anthracite dust.
1

L E H M A N N , S A I T O a n d G F R Ö R E R , in Archie

f. Hyg.,

Vol. L X X V .

KATAYAMA, i n ibid., 1916, Vol. L X X X V .
a
GROSS, in Beitr. z. Pathol. Anat. u. z. allgem. Pathol., 1927, Vol. L X X V I .
* C E S A - B I A N C H I , in Zeitsehr. f. Hyg. u. Infektionskrankh.,
1913, Vol. L X X I I I .

SILICOSIS IN GERMANY

351

Henius and Richert x did not succeed in proving the influence
of the inhalation of coal dust on rabbits infected with tuberculosis.
Wedekind 2 has, on the other hand, observed arrest of tuberculosis of the lungs in the case of rabbits infected intravenously,
through previous or subsequent intravenous injection, of the
suspension of coal dust.
Remarkable progress was effected by the large-scale experiments
of Jötten 3 and his collaborators, whose methods are distinguished
from those of earlier research workers especially by exact dosage
of the dust used, and by the method of infecting with tubercular
bacillus. After intensive dusting during two to five months with
fired vitrified porcelain dust, the laboratory animals showed a
highly developed proliferating reaction of the endothelium of the
capillaries of the lungs, which induced serious disease and eventually
death. The dust was found on the mucous membrane of the
respiratory passages, in the alveoli, in part filling these out completely, in the inter-alveolar and inter-lobular tissues, in the
peribronchial, perivascular and sub-pleural tissues, and in the
tracheo-bronchial lymph nodules. The greater part of the dust
formed an inter-cellular deposit. Fine unfired porcelain dust of
almost similar Si0 2 content, but richer in kaolin and coal dust,
caused qualitatively similar, but much slighter modifications. Two
months after the inhalation had stopped, the coal dust had for the
most part disappeared from the lungs, whilst the porcelain dust
was firmly fixed therein.
With a lesser concentration there appeared, even after use of
fired porcelain dust, no particular symptoms of disease. The septa
were somewhat thickened in parts through cell proliferation, and
there was also a slight fibrosis of the septa. The dust deposit was
similar to that in the previous case, but smaller.
After inhalation of lime dust, lime particles were found in the
lungs only in very sparse amount. Lime was immediately and
completely dissolved.
By application of massive concentration of dust, the changes in
the lungs brought about by dust alone were therefore very slight.
In order to study the effect of dust inhalation on simultaneous
tubercular infection, the rabbits were subjected to an intertracheal
infection with droplets by means of spraying with a tuberculous
bacillus emulsion. In one part of the experiment, a striking similarity
1
2
8

H E N I U S and R I C H E R T , in Zeitschr. f. Tuberk., 1926, Vol. X L V I , No. 2.
W E D E K I N D , in Klin. Wochenschr., 1928, No. 19.
J Ö T T E N and A R N O L D I : Gewerbestaub u. Lungentuberkulose.
Berlin, 1927.

352

PAPERS PRESENTED TO THE CONFERENCE

to the conditions in the case of human beings was encountered in
the following manner: the animals were first subjected to a weakened
infection by the use of drops, and later, after or during prolonged
dust inhalation, were reinfected with a stronger intravenous dose
of tuberculous bacillus. It was found that with the exception of
lime dust, all the kinds of dust applied favoured the settling and
dissemination of the tuberculosis infection. The danger of various
kinds of dust is given in descending order in the following series:
steel grinding dust, coarse pottery dust, fine pottery dust, coal
dust and soot. The last two were indeed probably less harmful
than grindstone and pottery dust, but showed, however, in contrast
to the controls, an undoubted favouring of tuberculosis, an observation which is of importance in the face of many statements to the
contrary, which are mostly based on insufficient material. The
most dangerous kinds of dust are those rich in quartz. They are
distinguished by the fact that they are retained in a considerably
firmer manner by the lung tissues than coal and soot. Lime
(Ca02H2) inhalation does not favour tuberculosis infection—it may
even perhaps be said to give rise to a certain arrest of the process.
In the case of animals reinfected with porcelain dust, there occurs
a marked tendency to the development of connective tissue round
the tubercular focii, as is characteristic in the case of human beings
where there is a combination of injury due to dust and tuberculosis.
Jötten and Arnoldi consider, as also did Fränkel at an earlier
date, the obstruction of the lymph channels by dust as of importance
in the causation of the unfavourable effect of dust on the progress
of tubercular infection. The lymphatic system in the presence of
dust-fibrosis is consequently no longer in a position like the dust-free
lung—to effect its task, namely, to reject disease stimulants which
have penetrated into it.
The results of research are in accord on many points with those
established by Mavrogordato, but indicate further an effect, though
a slight one, of coal dust and soot in favouring tuberculosis.
Later, similarly conducted experiments by Jötten and Kortmann 1
have shown that stone dust, with a 57 per cent, silicic content
(Si02) applied to prevent coal dust explosions in mines, produces
a similar effect to the fired porcelain dust, whilst cement dust
(20 per cent. Si02) and limestone dust only slightly favoured
tubercular infection, and basic slag dust not at all.
1
J Ö T T E N and K O R T M A N N : Gewerbestaub
Berlin; Springer, 1929.

und Lungentuberkulose.

I I . Teil.

SILICOSIS IN GERMANY

353

CHEMICAL EXPERIMENTS

Chemical experiments show that where pneumoconiosis is present
to a considerable extent, silica has been deposited in large quantities
in the lungs. Böhme, in examining rockdrillers' lungs, has
found a close relation to exist between the amount of deposited
silicic acid and the gravity of the fibrosis. Where the quartz
content (and silicates) of the fresh lung substance amounted to
over 0.7 per cent, (reckoned as dry substance over 3 per cent.),
there was found an extended cicatricial fibrosis, with quantities
ranging between 0.3 and 0.6 per cent, a moderate or average extent
of fibrosis, and with smaller quantities of quartz very little or no
fibrosis. Even in the same lung, the more seriously indurated
centres proved to be richer in quartz than the less indurated parts.
The highest quartz content found in a rockdriller's lung was 2.25
(calculated as fresh substance) or 8.77 per cent, (calculated as dry
substance). The value is almost as high as that formerly found
by Langguth in the case of a haematite cutter, namely, 11.9 per
cent, (calculated as dry substance), the highest amount known to
me in medical literature. The silicon is contained in the acid
insoluble fraction of the silicotic lungs not only in the form of
Si0 2 , but in smaller portions also as aluminium or alkali silicate.
We find in the hydrochloric acid insoluble fraction, 74 to 83 per
cent. Si0 3 , 13 to 22 per cent. A1 2 0 3 , 3.7 per cent, alkali oxide
together with small amounts of MgO or Fe 2 0 3 . The coal content
of the silicotic miner's lung may be extraordinarily high, up to
5.44 per cent, of coal reckoned as damp substance (21 per cent, as
dry substance), In the case of serious pneumoconiosis affecting
graphite millers, Koopmann * found 12.93 per cent, of graphite
(reckoned as dry substance). On the other hand, amounts of 1.4
per cent, of coal (reckoned as wet substance) were supported
without reaction by the lung tissues.
INFECTIOUSNESS OF D U S T TUBERCULOSIS

All doctors in districts where dangerous dusty trades have been
carried on have for centuries back (Agricola) noticed that a high
mortality rate from lung diseases amongst the men was accompanied
by a considerably lower mortality rate for the women and children.
It has been concluded therefrom that dust-tuberculosis is but
slightly infectious. This fact is indeed explained by the widely
1

KOOPMANN,

in Virchom Archiv, 1924, Vol. CCLIII, p. 423.
23

354

PAPERS PRESENTED TO THE CONFERENCE

recognised poverty in bacilli of the sputum, yet recent accurate
observations have nevertheless shown that the frequency of
tuberculosis amongst women and children in the families of workers
in dusty trades is higher than the average; Ickert x and Redeker 2
have found by radiological examination of the children of Mansfeld
miners a frequency of cases of calcified tubercular focii in the lung
amounting to twice that for children in the other industrial areas,
and further, that active tubercular forms occurred five times as
frequently amongst the schoolchildren in the Mansfeld mine
districts as in the surrounding country districts. According to
K reuser 3 , the tuberculosis mortality amongst members of the
families of pottery workers is distinctly higher than that for
women and children belonging to the families of other workers in
the same area (3.1 as opposed to 1.7).
INCIDENCE OF SILICOSIS

There are not so far available research results which embrace
the total number of workers engaged in any given industry, yet
an extensive series of observations has already been furnished
in regard to many industries.
Rockdrillers in Mines
Silicosis is met with more rarely amongst the coal miners in the
Ruhr coal district, but on the other hand, more frequently amongst
the rockdrillers engaged in drilling the layers of stone situated
between the beds of coal, blasting the stone, and removing the
debris. Amongst hese rockdrillers silicosis has considerably
increased subsequently to the introduction of mechanical drills,
as a consequence of the larger amount of dust produced. At the
instigation of the Ruhr Miners' Society (Ruhr Knappschaft), there
was undertaken in the winter of 1928-1929 clinical and radiological
(plate of the lungs) examination of 3,318 rockdrillers working
in the mines, in order to determine the presence of alterations
due to dust. According to Schürmann 4, of the above workers:
1,261 had worked as rockdrillers for 5 years
1,095 „
„
„
„
„ 10
441
15
*>"5 ,,
,,
,,
,,
,, ¿U
,,
216 ,,
it
,,
><
)> 25
„
1

I C K E R T : Staublunge

REDEKER,

und Staublungenluberkulose..

quoted by

Berlin, 1928.

ICKERT.

K R E U S E R , in Beitr. z. Klinik der Tuberkulose, 1926, Vol. L X I I I .
S C H Ü R M A N N : " G e w e r b e s t a u b " , in Die gewerbliche
Staublungenerkrankung.
Berlin, Springer, 1929.
4

SILICOSIS IN GERMANY

355

Of these 3,318 individuals, 80.56 per cent, showed no modifications due to dust, 19.44 per cent, showed modifications due to dust
distributed as follows:
Slight alterations
Alterations of slight to average severity . . . .
Alterations of average severity
Alterations of average severity to grave alterations
Grave alterations

Per cent.
14.74
2.26
1.84
0.42
0.18

Examinations made by Böhme amongst working rockdrillers
provided similar figures. Greater accumulation of indurated
symptoms due to dust is found only after about ten years' occupational experience, but even after five years and, exceptionally,
after two years changes of average severity are to be met with.
Investigations amongst working rockdrillers do not comprise all
severe disease forms, since the victims of these have mostly been
already obliged to give up work. Such cases are much more
frequently encountered in the course of investigations covering
miners suffering from diseases of any kind in hospitals. Likewise
the frequency of pneumoconiosis is naturally considerably greater
amongst these, since workers with pronounced dust diseases are
to be found assembled in the hospitals, and whilst, as a result
of the high average age of hospital patients, many workers formerly
suffering from latent silicotic disease have at those ages passed
into the stage of overt silicosis. Böhme found, during an
examination of 301 rockdrillers in a hospital in the last three years,
the following figures:
TABLE I
Length of
employment on
rockdrllling
Years
10
10-20
20-30
Over 30

Number of
workers
examined

Incipient
to slight
silicosis

Silicosis
of average
severity

Severe
silicosis

Total

124
133
34
10

41
54
11
1

10
15
7
2

5
7
4
3

56
76
22
6

301

107

160

From this survey there is easily recognised the increase in more
serious forms accompanying duration of employment at rockdrilling.

356

PAPERS PRESENTED TO THE CONFERENCE

The occurrence of dust fibrosis at all stages amongst rockdrillers
is also reported from other German coal districts (Upper Silesia
and the Saar district), though statistical data in regard thereto
are not so far available ; likewise, the presence of silicosis is known
amongst ore miners in the Saar and in the Mansfeld mines.
Ickert 1 observed exceptionally, even after two to five
years, typical changes; but extensive fibrotic forms only after at
least ten years.
In the Mansfeld copper district the mortality rate from tuberculosis is, according to Redeker (quoted by Ickert) three times
as high for the men as for the women. The tuberculosis mortality
rate reckoned over 10,000 living units, amounts in the local mining
communities to 36.5 as opposed to 10.7 in the other Prussian
country districts. The peak of the mortality rate for the local
miners, and indeed for general affections as well as for tuberculosis,
lies between fifty and sixty years of age, that is to say, as high
as that for all dangerous dusty trades.
Böhme met with an overt form of tuberculosis amongst rockdrillers having completed over ten years of employment, at the
rate of 3.5 times as frequent as that for coal miners with a similar
period of employment.
Quarry Workers
According to Domann 2 there were in 1907 70,000 workers
engaged in stone quarries and in establishments for the manipulation
of stone.
Thiele and Saupe 3 have found amongst quarry workers in the
Elbe sandstone district changes due to dust amounting to a very
high percentage. This depends on the one hand on the very high
quartz content of the stone, and on the other on the fact that
victims of dust still continue to work in the dusty trades, whilst
in the coal districts they are removed from work on rockdrilling
as soon as possible after they are found to be suffering from the
disease in question. Tuberculosis is often found in combination
with dust fibrosis amongst the sandstone workers in Saxony.
Table II again provides statistical data.
1
2

ICKERT: Staublunge und Staublungentuberkulose. Berlin, 1928.
DOMANN: Die Steinhauerlunge. Veröffentl. aus dem Gebiete der Medizinalverwaltung. Berlin, 1925.
8

THIELE and SAUPE: Die Staublungenerkrankung

Berlin, 1927.

der

Sandsteinarbeiter.

SILICOSIS IN GERMANY

357

TABLE II
Length of
employment
Years

Number
of workers
examined

Up to 5

9
9
8
19
19
24
10
11
2
1

1
1
6
13
10
9
4
1

112

„
,
- ,
,
,
,
,
,
,

„
.„
„
„
„
„
„
„

10
15
20
25
30
35
40
45
50

Injuries due to dust
Average

Slight
••

—

2
1
4
6
11
4
10

Severe

_
1
4
2

Kaestle x found, among 40 variegated sandstone workers, 25
suffering from silicosis, and amongst 133 white sandstone workers
38 suffering from silicosis. Amongst the variegated sandstone
workers silicosis was not only more frequent but occurred oftener
in the severer forms, whilst amongst the white sandstone workers
the slight forms predominated. The sandstone worked contained
about 80 per cent, of crystallised Si0 2 . Kaestle draws attention
to the fact that the isolated focii induced by this particularly
quartzitic dust were distinguished radiographically by the depths
of the shadows and the sharpness of the border lines. Nürburg
siliceous chalk contains 89 to 97 per cent, of quartz, mostly in an
amorphous form. Among 39 workers, who, moreover, had been
employed at the most for fifteen years, 8 were found to be suffering
from dust fibrosis2.
Amongst 93 granite workers (30 per cent. Si02) only 7 suffered
from coniosis. Tuberculosis was suspected only in 2 cases.
Kaestle found, among other symptoms, amongst shell limestone
workers (Si0 2 practically nil) inflamed hilar glands and sparse
pulmonary focii with small mottling, but none of the changes
corresponding to true silicosis and no tubercular lesions.
Cement Workers
The cement industry in Germany gives employment to 25,000
workers (Beintker) 3.
1
2

KAESTLE, in Fortschr. d. Roentgenstrahlen, 1928, Vol. XXXVIII, No. 6.
KAESTLE, loc.

cit.

»BEINTKER: "Zementfabriken und Kalkbrennereien", in Handbuch der

sozialen Hygiene, 1926, Vol. II. Berlin.

358

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Cement contains about 19-22 per cent. Si0 2 , 62-65 per cent.
CaO, 7-9 per cent A1203. The silicic acid is for the most part
contained in a fixed form, only 3 per cent, being free SiO? ( Jòtten) 1 .
According to Schott 2, cement workers seldom develop indurated
dust focii of the lungs, and then only after ten years' employment.
Out of 100 cases, mostly older workers, he found changes due to
dust in 21 cases, which for the most part were of a slight variety.
Kaestle, on examination of 93 cement workers, found only one
typical case of pulmonary silicosis ; in five further cases there were
slight changes of the hilus and surrounding areas, which he likewise
attributed to the effect of dust. The tendency to tubercular
changes could not be proved. The tuberculosis mortality rate
amounted in 1908 to 10.6 per 10,000, and was therefore very small.
Perhaps the lime content of the cement exercises a favourable
influence as regards tuberculosis. Sleeswijk 3 emphasises the fact
that in the Dutch sandstone works the risk to the workers
diminishes, the greater the lime content of the stone. The low
tuberculosis mortality rate of marble-workers, plaster-burners and
other workers handling materials with a lime content is known
(Jòtten and Arnoldi). The quantity of dust in the cement
industry is in parts considerable, despite many measures of protection. Jötten found in the packing-room 20 mg. of dust per
cubic metre, near the cement mills 160 mg., and near the ball
mills 300 mg.
Quartz Millers
Injury due to dust is set up to a considerable extent in the case
of quartz millers 4.
Pottery and Stoneware Industries

According to Koelsch (1914), there were 67,295 workers and
employees engaged in the German china industry. Only about
half of these were employed in connection with the production
of china and exposed to china dust in large quantities. The other
half consisted of decorators and helpers (painters, packers, machine
workers, etc.); 25 to 40 per cent, of the employees were women.
' J Ö T T E N : " S t a u b l u n g e u n d S t a u b l u n g e n t u b e r k u l o s e " , in Die gewerbliche
Staublungenerkrankung.
Berlin, 1929.
2
SCHOTT, in Beitr. z. Klinik der Tuberkulose, Vol. L X I X , No. 1.
3
S L E E S W I J K , in IV. Internat.
Kongress für Unfallheilkunde
und Berufskrankheiten, A m s t e r d a m , 1925.
4

D O M A N N , loc.

cit.

L E H M A N N : Ueber die Gesundheitsverhältnisse
keramischen,
insbesond. der Porzellanindustrie

der Arbeiter in der deutschen
usw. Berlin, 1929.

SILICOSIS IN GERMANY

359

The clay used contained about 25 per cent, quartz, 25 per cent.
feldspar, and 50 per cent, kaolin (aluminium silicate). Froboese 1
found quantities of dust amounting to 3.5-161 mg. per cubic
metre. The higher quantities were almost always found in the
grinding rooms; in the other departments the quantities of
dust for the most part only amounted to 5-20 mg., or on an average
to 12.3 mg. Koelsch had at an earlier date found greater quantities.
The installation of the factories was in general designated as
hygienic. At points where there was more abundant dust production many kinds of exhaust apparatus had been successfully
applied, as in the cases of polishing half-dry china objects, cleaning
subsequent to first firing, kiln drawing, glazing, etc.
Holtzmann and Harms 2 found on radiological examination of 41,
chiefly older, pottery workers, 19 cases of coniosis of average to
severe type, and in three cases the symptoms of pronounced
pneumoconiosis.
Examination of 85 workers belonging to china factories in Berlin
revealed about 30 per cent, of the workers as suffering from changes
due to dust. May and Petri 3 examined radiologically 50 elderly
pottery workers particularly exposed to the inhalation of dust, and
suspected of clinical symptoms, and found slight thickening in the
hilar area in 30 per cent., with incipient mottling in 26 per cent, and
distinct mottling in 12 per cent. According to the extensive and
protracted researches undertaken by Koelsch and Kaestle 4 at Selb,
the chief centre of the Bavarian pottery industry, 145 out of 455
porcelain workers, or about one-third, revealed radiologically
symptoms of dust fibrosis, mostly of a slight degree, and a smaller
number in the second and third degree. The male workers suffered
more frequently (38 per cent.) from changes due to dust than the
women (25 per cent.). The reason for this difference is chiefly
to be found in the shorter length of employment in the case of
women.
In 1.5 per cent, of the total number cirrhotic tuberculosis was
confirmed, and the possibility of a combination of dust fibrosis and
tuberculosis was admitted in a further 3.7 per cent. A frequent
tuberculosis rate could therefore not be proved.
1

F R O B O E S E , in Archiv f. Hygiene, 1925, Vol. XCV, p. 175.
HOLTZMANN and H A R M S : Zur Frage der Staubeinwirkung
auf die Lunge
der Porzellanarbeiter.
Tuberkulose-Bibliothek, No. 10. Berlin, 1923.
3
MAY and P E T R I : Bear. z. Klinik d. Tuberkulose, 1924, Vol. L V I I I , No. 2.
4
KOELSCH and K A E S T L E : Klinische und röntgenologische
Untersuchungen
über den Lungenbefund
bei 500 Porzellanarbeitern.
(Not y e t published, quoted
2

LEHMANN.)

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Amongst the helpers in the pottery industry no forms of indurated
tissue due to dust were met with.
Earlier statistical returns prepared by Sommerfeld x, Holitscher2,
Bogner 3, Leymann 4, Koelsch 5, all concurred in showing a high
tuberculosis mortality amongst porcelain workers. At least, any
variations were slight. On the basis of clinical researches Koelsch
had earlier, in 1908-1912, found a higher morbidity rate for tuberculosis, and likewise Thiele 6 in 1920 in regard to the Saxon porcelain
workers. Kreuser 7 also, in his capacity of insurance medical
officer for the district of Merzig finds frequent causes of death from
overt tuberculosis amongst pottery workers. The annual tuberculosis mortality rate per thousand amounted amongst the pottery
workers to 4.4 per cent., and amongst other workers to 1.77 per cent.
The peak of the tuberculosis mortality rate among porcelain
workers was reached, according to Kreuser, between the ages of
fifty-one and sixty, whilst for the remainder of the local population
the peak rate occurred between twenty-one and thirty. Thiele,
Koelsch, Holtzmann and Harms find a similar age for the peak rate.
That the occupational risk is not the only decisive factor in
regard to the tuberculosis mortality rate among porcelain workers
has been shown by Vollrath 8 in a statistical work. In the various
porcelain districts of Thuringia the tuberculosis mortality rate
amongst these workers is lowest where the economic and hygienic
conditions are most favourable, and vice versa. Koelsch 9 also
proved, in regard to the Bavarian industry, that tuberculosis is
of most frequent incidence in those districts where the pottery
industry has been longest established, the calling descending from
father to son, and where conditions approach those of town industries, whilst in other regions, where the industry was of later
establishment, the plant more modern, and the workers living in
country surroundings, the tuberculosis was less disseminated.
Pathological and anatomical researches have been engaged in by
1
SOMMERFELD, in Deutsche
Vierteljahrschr.
für öffentliche
Gesundheitspflege, 1893, Vol. X X V .
2
HOLITSCHER : " K r a n k h e i t e n der P o r z e l l a n a r b e i t e r " , in Weyls Handb. d.
Arbeiterkrankheiten,
1908.
3
B O G N E R , in Deutsche Vierteljahrschr. f. öffentliche Gesundheitspflege, 1909,
Vol. X L I .
4
L E Y M A N N , in Zentralblatt f. Gewerbehygiene, 1913 a n d 1915.
5

K O E L S C H : " S t a u b u n d B e r u f " , in G R O T J A H N a n d K A U P , Handbuch

der

sozialen Hygiene, 1912.
6
T H I E L E , in Zeitschr. f. Tuberkulose, 1921, Vol. X X X I V .
7
K R E U S E R , in Beitr. z. Klinik d. Tuberkulose, 1926, Vol. L X I I I .
8
V O L L R A T H , in Beiträge zur Klinik der Tuberkulose, 1921, Vol. X L V I I .
9
K O E L S C H : " K e r a m i s c h e I n d u s t r i e " , in Handbuch der sozialen
Hygiene,
Vol. I I . Berlin, 1926.

361

SILICOSIS IN GERMANY

Roessle of Jena. Out of 45 pottery workers, 20 (44 per cent.) were
seen on post-mortem examination to have suffered from dust
fibrosis, and 25 (50-55 per cent.) from tuberculosis.
From the fibrotic character of the tuberculosis of the lungs and
the lack of caseous forms of pneumonia, Roesslex concludes that
a favourable effect is exercised by porcelain dust.
The results of more recent researches undertaken amongst
workers in the German pottery industries, are in agreement in
proving that pneumoconiosis of the lungs occurs in a considerable
number of cases. Controversy exists in regard to the question of
whether tuberculosis is also frequent amongst these workers. Under
favourable hygienic conditions, up to the present, incidence of
overt tuberculosis has hardly been found to be above the average
amongst workers engaged in the china factories. Kreuser's figures
relative to the frequency of deaths from tuberculosis and those of
Roessle relative to the incidence of tuberculosis as a factor in
mortality amongst porcelain workers, point, on the other hand, to
the fact that towards the end of life, tuberculosis occurred frequently
amongst these workers. The contradiction between these points
of view is only apparent. Probably many cases of fibrotic tuberculosis, which only became open late in life, have been disguised
as dust fibrosis.
Metal- Grinders
The frequency of lung diseases amongst grinders has been
recognised for a long time. Protracted hygienic, clinical and radiological researches have been recently instituted by Teleky, Lochtkemper, Rosenthal-Deussen and Derdack 2 in the highlands
(Solingen-Remscheid district). Recognition of the connection
between dust inhalation and lung disease had given rise to the
introduction of regulations as to means of protection as early as
1875. Under the influence of these, and in connection with the
general fall in the tuberculosis mortality rate, the health conditions
amongst grinders has very considerably improved in Solingen,
though less so in other places in the district.
In so far as the death registers permit of judgment of the circumstances, it was found that tuberculosis still occurred very frequently
amongst grinders and that the rate was extremely heavy in certain
1
2

ROESSLE, in Beiträge z. Klinik d. Tuberkulose, 1921, Vol. XLVII, No. 2.
TELEKY, LOCHTKEMPER, ROSENTHAL-DEUSSEN and

fährdung und Staubschädigungen der Metallschleifer.

DERDACK: Staubge-

Berlin, 1928.

362

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places. The tuberculosis mortality (inclusive of dust fibrosis)
relative to 10,000 living, amounted in Solingen to 14.7 for the
total male population, and 29.9 for the grinders. In Remscheid
the differences were much greater. The tuberculosis mortality
return for the male population amounted to 17.0, whilst on
the other hand the corresponding rate for grinders reached 97.6.
In Solingen as well as in Remscheid, a very remarkably high peak
for tuberculosis mortality was revealed for workers of 50 years
of age, as Collis and Teleky have frequently shown to be the case
in regard to occupational tuberculosis. Very remarkable is the
difference between the tuberculosis mortality for grinders in the
two adjacent towns of Solingen and Remscheid. Teleky ascribes
this to the difference between the hygienic conditions of the
industry in the two places.
With the help of Owen's apparatus Rosenthal-Deussen and
Teleky estimated the amounts of dust in various workplaces;
they then established the fact that in winter the amount of
dust was about three times as great as in summer, in consequence
of the lack of ventilation and the production of soot from the
heating apparatus. The result of comparative analysis at working
posts can be seen from table III:
TABLE III.

ESTIMATIONS OF DUST IN GRINDING ROOMS

Occupation

Wet sandstone
Dry sandstone, with dust removal

Dust figures at the
working-post
Summer

Winter

1,047
785

2,546

Artificial grindstone, dry, without dust removal
,,
„
„ with dust removal
,,
,,
,, with mechanical removal
,,
,,
wet, automatic
„
,,
,, hand work
,,
„
with oiling

647
246
428
203
295
605

Dry emery polishing, without dust removal
,,
,,
,,
with dust removal

419
244

Fine emery polishing, without dust removal
,,
,,
„
with dust removal

358
238

Dry buffing, without dust removal
,,
,,
without dust removal, with oiling
,,
,,
with dust removal, with oiling

526
674
263

Rosenthal-Deussen and Teleky.

1,424

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SILICOSIS IN GERMANY

It follows from this that by far the greatest amounts of dust
are developed during the wet grinding of sandstone—an established
fact which is in accord with the findings of the English and American
research workers. The dust figure is lower in the case of grindstones
provided with ventilation apparatus, and likewise in the case of
artificial grindstones and emery polishing.
The artificial grindstone consists of artificial corundum (A1203)
or silicon carbide (SiC). Also emery (30-40 per cent, corundum,
a little Fe 2 0 3 , 2-8% Ver cent. SiOs) is used. Emery polishing is
effected by leather bands coated with emery (or colcothar, chalk,
diatomaceous earths). The dust figure becomes considerably
diminished by the application of exhaust devices during the use
of artificial grindstones, and likewise during emery polishing.
Oiling does not reduce the dust figure. During wet grinding on
sandstone the dust produced is especially rich in quartz particles.
Large amounts of dust arise during rounding and splitting of
sandstone.
Lochtkemper examined clinically and radiologically 100 grinders,
with a view to determining the presence of injuries due to dust.
The results of this examination are given in table IV.
TABLE IV

Number
examined

Polishers
Pine emery polishers (pliester)
Dry emery polishers (pliester)
Artificial grindstone
Dry sandstone
Wet sandstone

Free
form
dust
fibrosis

11
9
15
14
15
36

100

Suffering from dust fibrosis
I

III

4
2
4

7
9
8
10
1
19

2
2
8
6

2
11

1 »

Had worked for twenty-three years in the same room on wet grinding.

The classification of the three stages of the disease differs from
the usual practice, in so far as that all cases evolving with thick,
fine mottling are included in Group III; these have been recorded
by other research workers as changes of slight—or, as the case
may be, average severity.
The cases in the first group only show very slight changes. It is
true that changes due to dust are found amongst all the groups
of workers, but the very severe changes are found almost exclusively

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in the case of sandstone grinders, and here again, these predominate
in the case of wet grinding.
Polishers, emery polishers, and artificial grinders show only
increase of the linear marking of the lung with single mottling,
and increased trunk shadows at the basis of the lung. When at all
exposed to the influence of quartz dust, these groups of workers
only come in contact with very small quantities.
Lochtkemper and Teleky recommend, amongst others, the
following hygienic measures of improvement: substitution of
artificial grindstones for sandstone as far as possible; separation
of emery polishing rooms from the ordinary grinding rooms, and
effective dust exhaust devices.
Various Occupations
The occurrence of a typical form of silicosis is known in Germany
amongst workers producing and handling fireproof (with a quartz
content) stone-ware (schamotte-silica-stone), amongst moulders in
iron foundries who make the moulds for castings, amongst workers
engaged in sand-blasting; and amongst glass-grinders. Statistical
returns as to the frequency of silicosis amongst these workers are,
however, still lacking.
Coal Miners (Hewers)
Among hewers in coal mines, also, radiological examination
reveals, amongst other symptoms, slight indurated areas due to
dust. The frequency of this affection may be seen from the following
table, prepared by Böhme:
Length of
employment
Years

0-10
10-20
20-30
30-40

Appearance
of the
formation
Severe
of hard thickening
cicatricial
tissue

Number
of cases
of
indurated
forms

Number
examined

Initial
changes

24
94
74
31

0
16
17
12

1
9
9
9

0
0
0
1

0
0
0
0

1
25
27
22

223

Fine
mottling

The frequency and intensity of the changes thus increases, as
in other dusty trades, with the length of employment, but the
disease hardly ever proceeds beyond the stage of fine mottling.
Anatomical examinations have established that the condition in

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SILICOSIS IN GERMANY

question consists of a true small nodular dust fibrosis. Often the
cause may be sought in a mixture of quartz with the dust. The
coal hewer may also, on occasions, inhale quartz dust which is
produced in his neighbourhood, or which he himself raises in
removing stones in his proximity. Large quantities of coal dust
can, however, in themselves produce a certain form of fibrosis.
The quartz content chemically proved to be present in such lungs
with coal dust nodules is, however, extraordinarily low. Collis
also has observed pneumoconiosis amongst coal miners, especially
coal trimmers. In the least severe cases the Rontgen ray revealed
changes consisting only in an increase in the linear marking of the
lungs. Anatomically this stage often corresponds merely to the
filling-up of the perivascular and peribronchial lymph areas with
coal dust, without fibrosis worthy of mention.
Severe dust changes are at times observed amongst graphite
workers. Quite pure and soft Swedish coal may indeed become
deposited in considerable amount in the lungs, and give rise to a
mottled X-ray picture, but according to Edling 1 it is not productive
of fibrosis. Hollmann 2 found, amongst 33 workers in a carbon
pencil factory exposed to pure coal and graphite dust without
admixture of stone, three certain cases of dust fibrosis, and besides
these, sixteen cases in a pre-fibrotic condition.
The mortality from tuberculosis among the miners in the Ruhr
district was before the war, at the figure 71 per 10,000, less than
that for most other occupations. During the War and after the
War it rose considerably, and then gradually fell. It would be
considerably less were not stonecutters, with their high tuberculosis mortality, included in the returns.
LEGISLATIVE PROVISIONS IN REGARD TO COMPENSATION

By an Order of the Ministry of Labour, dated 12 May 1925, a
number of occupational diseases have been assimilated to occupational accidents for the purpose of compulsory compensation.
Silicosis was not at that time included under those occupational
diseases subject to compulsory compensation, though the Schneeberg
lung disease, that peculiar disease occurring amongst the miners
of the Schneeberg ore district, which evolves with the formation
of carcinoma in a silicotic lung was included.
1
3
3

E D L I N G , in Acta radiologica, Vol. V I .
HOLLMANN, in Zeitschr. f. Tuberkulose, 1928, Vol. L I I , p . 394.
Cf.

BAUER, ENGEL,

KOELSCH,

KROHN:

"Die

Ausdehnung

der

Unfall-

versicherung auf B e r u f s k r a n k h e i t e n " , in Arbeit und Gesundheit, 1929, No. 12.

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In accordance with the Order of 11 February 1929, by which
the list of occupational diseases subject to compulsory compensation
was considerably extended, " severe pneumoconiosis " (silicosis)
was also included, in so far as it occurred as the result of occupational
activity in the following industries:
(a) Establishments engaged in sandstone extraction, manipulation and manufacture.
(b) Metal grinding establishments.
(c) Pottery factories.
(d) Mining undertakings.
In the case of severe dust fibrosis combined with tuberculosis
of the lungs, tuberculosis is regarded as pneumoconiosis (silicosis)
for the purposes of compensation.
Right to compensation is therefore confined to severe pneumoconiosis. As " severe " are considered, according to the German
legal interpretation, in general injuries and diseases which involve
a reduction of the earning capacity of the patient by at least 50
per cent. The right to compensation has a fairly extensive retrospective effect. Injuries are taken into consideration when the
disease has obviously been caused as the result of occupational
activity subsequent to the date 31 December 1919 in one of the
industries mentioned.
The insurance is effected as in the case of the German accident
insurance, through employers' co-operative societies (Berufsgenossenschaflen), that is, special bodies founded with a view to execution
of the provisions in regard to accident insurance, and protection
against accident, which collect the funds necessary for their purpose
from the employers in the branch of industry concerned. These
societies grant, in accordance with the legal prescriptions, on
the occurrence of " severe pneumoconiosis ", benefit, the amount
of which is dependent upon the degree of earning capacity; they
further accord benefit to the next of kin when the occupational
disease has been the real cause of death.
The societies are further in a position to grant " transitional
allowances " independent of the extent of the occupational loss of
earning capacity when continuation of the former occupational
activity is to be feared as an agent in aggravating the disease. This
" transitional allowance " is intended to enable the patient to
enter another occupation which does not expose him to risk.
Tuberculosis of the lungs combined with severe pneumoconiosis
is regarded from the point of view of compensation as pneumoconiosis itself.

SILICOSIS IN GERMANY

367

The occupational disease is subject to compulsory compensation.
and also subject to compulsory notification. Notification is obligatory for the employer as well as for the doctor in charge of the case.
Notification has to be made at the insurance office, which proceeds
to thorough examination by a doctor appointed for the purpose
—" geeigneter Arzt ". The society decides as to the proposed
payment of benefit. Appeal to the Reich Insurance Office against
their decision is possible.
In future, the institution of protective measures against silicosis
in the industries affected will also come within the competence
of the societies.
PROPHYLAXIS IN REGARD TO DISEASES FROM DUST

According to Thiele and Saupe, in the Elbe sandstone district
it is the practice to wet the stone frequently, in order to reduce
the amount of dust produced. Many attempts have been unsuccessfully made in regard to the wearing of respiratory masks. The
workers always felt themselves unduly hindered in their work
by these.
In the grinding industries, the use of ventilators in the workrooms,
and of dust exhaust apparatus at the working posts has been
compulsory for several decades. Processes which cause considerable
dust production, such as the splitting of grindstones, have to be
deferred to the close of the working shift. Teleky demands, further,
that as far as possible sandstone should be replaced by artificial
grindstone, and that effective dust exhaust devices should be
installed, together with the separation of polishing and grinding
operations.
In the china industry, also, the provision of exhaust dust
apparatus, and means of maintaining the workrooms in a state of
cleanliness are required. The hygienic conditions have been greatly
improved during the last decades, and further improvement may
be expected by the erection of partition walls to shut off very
dusty processes from other departments, and by the covering-in
of edge mills and similar devices in dust-tight compartments.
Koelsch, further, demands thick, smooth flooring, cleaned daily
by wet process, daily cleaning of the working post and tools, special
working clothes, and adequate washing facilities.
In mining, many efforts have been made to prevent the production
of dust and to further its removal. Many rockdrillers tie wet
sponges in front of their noses, others wear respiratory masks of

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various patterns; most workers, however, are opposed to such
measures, since they are apt to hinder work. The " duster " who
sprinkles stone dusts as a protective measure against coal dust
explosions, regularly wears a protective mask. Continuous sprinkling with water of drill holes is very much practised, but the
contact with material which becomes wet during this process,
as well as wetting of the workers' clothes, has been found extremely
trying. Dry exhaust removal of dust from drill holes, on the
principle of the vacuum cleaner, has likewise been applied in many
places.
A prize essay recently issued on the subject of measures of protection against dust contains many new proposals, the efficacy of
which time alone can prove.
In many dusty trades, the wearing of helmets with a provision
of fresh air has become an established custom, as, for instance,
in sand-blasting.
Where convenient, as, for instance, in the case of ball grinders,
an effective protection from dust is provided by enclosing the
apparatus in a dust-tight cover.
There must be emphatically demanded thorough medical
examination before entry into the occupation of rockdrilling,
combined with the rejection of unfit applicants, and likewise
periodical radiological examination.
Of great importance for the protection against many severe
forms of pneumoconiosis, is the campaign waged against tuberculosis. All individuals manifestly tubercular must be kept away
from work in trades involving exposure to quartz dust. The wellorganised campaign against tuberculosis engaged in for several
decades past, has succeeded in bringing about a reduction in the
tuberculosis mortality and morbidity rates, but during the war
and post-war periods these figures again increased very considerably.
In recent years there has occurred a fresh reduction as compared
with the pre-war figures, and it is hoped that a further fall in the
tuberculosis rate may exert a favourable influence on the campaign
against the severer forms of pneumoconiosis.
The brilliant success encountered in connection with the application of well-organised measures for dust reduction in South
Africa leads to the hope that in Germany also the campaign against
pneumoconiosis will be crowned with success.

SILICOSIS IN GERMANY

369

II. — TYPES OF DUST AND SILICOTIC LUNGS:
COMPARATIVE STATISTICAL AND
CLINICAL-RÖNTGENOLOGICAL RESEARCHES IN BAVARIA
PROFESSOR KOELSCH, MUNICH, IN COLLABORATION WITH
DR. KAESTLE, MEDICAL OFFICER OF RONTGENOLOGY IN MUNICH

According to the theory of pneumonoconiosis founded by Zenker,
Professor of Pathology in the Bavarian University of Erlangen,
in the year 1865, all changes of the pulmonary tissue caused by
different kinds of dust were up to the beginning of the present
century considered as fairly similar, though chalicosis (lung changes
due to stone dust) took a specially predominant place in regard to
its pathological and clinical effects.
The notions of the action of the various types of dust were at that
time standardised in an essentially morphological manner, it being
assumed that it was particularly the pointed and sharp-edged dust
particles which caused mechanical wounds of the pulmonary
tissue and thereby in combination with dust deposits set up
injuries. Only with the observations of the last decades, and in
particular the thorough investigations effected in the last fifteen
years have the former theories been fundamentally altered. To-day
it is recognised that the varied types of dust must be judged in
a fundamentally different manner, that in this connection the
decisive factor in regard to effect is not so much the morphologicalphysical activity of the various types of dust, but rather the content
of free crystallised silicic acid (quartz). Where it is a question of
mineral dust, where dust with a mineral, metallic, vegetable or
similar content is raised, the deciding factor in settling the question
from the point of view of industrial medicine is the relative presence
of free silicic acid; it need hardly be added that the amount of
dust, the duration of exposure to it and other external factors
also play their part.
Wherein does the specific effect of silicic acid consist ? In
addition to morphological properties such as hardness, sharp
glass-like fracture, there come also into consideration certain
chemical-necroctic fibro-plastic effects, interference with the cleans24

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ing mechanism of the lung in regard to dust removal, disturbance
of the bactericidal power of the blood and other factors; these
problems still await solution at the present time.
It is, besides, now known that the various forms of pneumonoconiosis manifest fundamental differences from the pathologicalanatomical and clinical points of view—that in reality it is only
injuries caused by dust with a silicic acid content, the so-called
" silicosis ", which are of practical importance. Finally, it is
necessary to distinguish between " dusty lungs " and pneumonoconiosis, for not every " dusty lung " as regards silicosis implies
disease in the clinical sense, involving a right to compensation;
only in the case of average and severe forms is it possible to speak
of pneumonoconiosis. The same is true of uncomplicated silicosis ;
yet in the latter case certain complications may be brought about
especially through accompanying tuberculosis (silico-tuberculosis,
tubérculo-silicosis) or through secondary disturbances of the circulation; such complications may under certain circumstances, even
in cases where roentgenological examination reveals but slight
symptoms, lead to the belief that severe illness is in question.
The present-day view in regard to the problem is somewhat as
described above.
The author had already commenced some years ago to prove
these views statistically and clinically by large-scale investigations.
In the last few years over 1,200 workers in carious branches of
industry involving exposure to mineral dust were clinically and
röntgenologically examined with the collaboration of the rontgenologist Dr. Kaestle: for the majority of this group of workers
available history in regard to morbidity and mortality from diseases
of the respiratory passages was also taken into statistical consideration. The data provided by these investigations, will be given
in a comprehensive manner in the following part of this Paper,
and dealt with, with the exception of granite, in order of the specific
danger attaching to the dust as regards pneumonoconiosis,
beginning with the occupations known to be the most dangerous.
(1) The foremost place is occupied by sandstone workers.
Our investigations covered workers from the variegated sandstone district on the lower Main (Miltenberg, Marktheidenfeld)
and from the white sandstone district on the middle Main (Eltmann,
Zeil). The material worked consisted of quartz granules of varying
size baked into a conglomerate with argillaceous cement. The total
silica content amounts to 80-85 per cent.; it consists almost

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entirely (90-100 per cent.) of free silicic acid. The microscopic
picture of the fine dust reveals considerable quantities of quartz
crystals. Statistical analysis of the data furnished by the General
Local Sickness Fund at Marktheidenfeld revealed the fact that
sandstone workers there (calculated on the full working complement) showed on a four-year average, in respect of pulmonary
tuberculosis, a morbidity rate about five times that for the remaining insured male population of the same age. The rate for other
diseases of the respiratory system was likewise higher (10.50 as
against 7.71), while the rates for all other disease forms including
accidents occurring amongst sandstone workers were lower (the
total being 59.18 as against 61.88). In the case of the General
Local Sickness Fund of Miltenberg, the three-yearly average
showed a considerable excess for sandstone workers for all forms of
disease of the respiratory system including tuberculosis (15.8 as
against 5.2). In the case of the Trade Sickness Fund of the firm
Ph. Holzmann, the rate for diseases of the respiratory tract,
including tuberculosis, amounted for the three-yearly average
affecting sandstone workers, to 1.25 per cent., while for the remainder of the insured workers it was 0.90 per cent.
The death register showed the following results (three-yearly
average) :
General mortality

Tuberculosis, lung diseases

District

Marktheidenfeld
Miltenberg

Stoneworkers

Other
males

Stoneworkers

Other
males

Per cent.

5.60
3.83

1.64
1.64

5.32
3.11

0.2
0.2

About 173 workers in all were covered by the clinical ròntgenological examination. Whilst deposits of stone dust were only
found to a small extent, 1 per cent, in the case of workers with
a five years' record of work, the amounts found in the case of workers
old in the trade grows to such an extent that workers with a
twenty to forty years' record showed up to 76 per cent, affected by
severe injuries due to dust. Taken all in all there was found
in the case of 36 per cent, of the workers indisputably positive
lung changes as indicating silicosis, of which five were probably
combined with tuberculosis.

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The Rontgen ray picture showed here quite typical changes;
in pronounced cases both lungs were found to be fairly evenly
infiltrated with numerous isolated foci, characterised by strikingly
profound shadows and sharp borders of the isolated foci; the foci
with fine mottling gave the appearance of small shot (bird shot).
The site favoured was the middle and lower region of the lungs.
There were also found pictures showing broadened flakelike foci
distributed fairly symmetrically over both lungs; these massive
broadened foci were likewise characterised by the depth of their
shadows. To these were added massive hilus nodules with
sharply outlined arborification, and further, not uncommonly
pleuritic changes, adhesions, etc. The general impression is one
of a severe mass of dust infiltration of the pulmonary tissues.
(2) In the neighbourhood of Neuburg on the Danube, the
so-called siliceous chalk is extracted, which contains about 86-97
per cent, of silicic acid mostly in a free state. Thirty-nine of the
workers engaged there were examined clinically and radiologically;
the majority had, it is true, been working in the trade for under
ten years (frequent change of occupation !). Most of these were
found to be relatively healthy; on the other hand, eight showed
clear signs of silicosis, mostly in the form of mixed large nodular
and fine mottled foci; the shadows were somewhat less profound;
between numerous soft shadow areas with relatively sharp outlines
lay solitary thick foci with profound shadows resembling those
typical of pure sandstone pneumonoconiosis.
(3) Less on account of its place in the order of danger, but rather
on account of the type of Rontgen picture connected with it, an
account of the granite stone industry may be added here. Granite
dust contains between 61 and 82 per cent, of silicates ; the content
in free crystalline silicic acid is said to amount to about 25-30
per cent. The physical combination of the quartz crystals is
probably a very firm one in this case. Statistical analysis of the
data of the General Local Sickness Fund for the Passau district,
counting upwards of 1,600 granite workers (full working complement) amongst its members, showed more favourable figures
relative to respiratory diseases including tuberculosis of the lungs
in comparison with similar age-groups amongst the remaining
male members insured. Likewise the mortality rate for granite
workers as against that for the general male population in the same
district was in nowise excessive. It was even, on the other hand,
more favourable: mortality rate from all diseases (three-yearly

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373

average) 0.56: 2.11. The mortality rate for tuberculosis was 0.14:
0.16 per cent. The anamnestic and clinical investigation next
covered 200 granite workers of the lower Bavarian forest. It
revealed in general more favourable conditions than had been
expected. A thorough clinical and röntgenological examination of a
further 93 granite workers from the Fichtelgebirge was effected
later, almost 82 per cent, of the workers in question having been
engaged in the occupation for upwards of ten years (up to fifty
years) ; 64 of these showed no symptoms of any kind. Clinical
findings in respect of subjective complaints were present in the
case of 20 workers, yet the röntgenological examination showed
in all these cases fairly normal conditions.
Clear pneumonoconiotic changes were only established in the
case of 5 workers in all (out of 93)—that is, hardly 5 per cent, of the
workers in question having a record of work as granite cutters of
between twenty-five and thirty years. The pneumonoconiosis
of the granite workers examined by us is characterised by moi e or
less numerous, fairly thick, small foci of the size of those produced
by sandstone pneumonoconiosis, by arborification starting from
more or less distinct enlarged and thickened hilar markings, especially in the right towards the basal and also the other regions
of the lung. The speckled shadows are localised as in other types
of silicosis, that is to say in the middle and infraclavicular lateral
regions of the lungs. In the cases examined by us the small foci
did not in general attain the thickness of the finely mottled forms
found amongst victims of sandstone pneumonoconiosis; solitary
nodules approached this thickness. The smaller content of crystalline silicic acid in firm combination with other harmless accompanying minerals may indeed be considered to be the chief reason
for the diminished biological effect of this mineral dust in general
on the lungs.
(4) Special interest has been taken in porcelain workers, the
dust risk to which they are exposed having for long been disputed.
The possibility of contamination of the atmosphere by dust in
the porcelain industry is freely admitted. I have determined the
presence at various working posts of concentrations of between 22
and 205 and over milligrams of dust per cubic metre of air. The
porcelain contains 42-66 per cent, of clay (aluminium silicate),
17-37 per cent, feldspar (potassium aluminium silicate), 12-30
per cent, quartz (free silicic acid). In the glaze there is about
30 per cent, of quartz, 30 per cent, feldspar, 26 per cent, calcspar,

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10 per cent, porcelain fragments and smaller quantities of other
mineral by-products. The dust is very fine and very volatile,
though it is necessary also to take into consideration the fact that
owing to the hardening process (vitrifying) a part of the free silicic
acid in the quartz enters into combination with the potassium
and aluminium.
I had long ago undertaken comprehensive statistical research
in regard to the liability of porcelain workers to diseases of the
respiratory passages or tuberculosis, the results of which, similar
to those achieved by earlier authors, confirmed the high morbidity
and mortality rates of these workers from diseases of the respiratory
passages, including tuberculosis. As an example I established
the fact that in certain typical porcelain districts of Bavaria
perceptibly higher mortality rates occurred amongst porcelain
workers for tuberculosis and other chronic lung diseases in comparison with members of the general population belonging to similar
age-groups—in Selb and Rehau a fourfold, in Tirschenreuth,
Kronach, Teuschnitz a two or two-and-a-half times increased
mortality rate. Similarly the actual porcelain makers showed
an increased morbidity rate for respiratory diseases—for instance,
in Selb 11.22 per cent, as against 8.44 per cent, for the other workers
in the same factories. Clinical examination (without rontgenological plates) revealed, in the case of about one-half of the 1,000
porcelain workers examined, changes in the lungs which must be
ascribed to injury due to dust. It was possible to prove correspondence between duration of employment and changes in the lungs.
There was effected a further clinical and ròntgenological examination of 500 workers. In this case it was found that about
55 per cent, of the male workers and 35 per cent, of the women
workers, giving an average of about 45 per cent., showed changes
of the lungs of varying degree due to dust.
Critical consideration of the data provided by these examinations
lead to the following conclusions.
In the case of workers who had been engaged in the porcelain
factory for a few years there was entirely lacking specific dust
changes of the lower respiratory passages or where present at all
these showed but slight development. In the case of older workers
with a relatively short duration of work the changes were more
plainly seen and more obstinate than in the case of younger workers
with the same duration _ of employment. Here an important
part is played by the vitality of the entire constitution and of the
respiratory system as a defence against injury, and in regard to the

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self-cleansing mechanism for removal of the dust which has penetrated into the respiratory passages. With advancing working
experience the symptoms of dust infiltration of the respiratory
organs increase from the subjective, clinical and röntgenological
point of view.
The first signs of dust in the lungs of porcelain workers are revealed röntgenologically by numerous shadow patches of almost
similar size distributed over the two central parts of the lung
being about a pin's head in size or a little over. The shadow
patches are relatively soft and the borders are of average sharpness.
In places there is to be seen in addition signs of chronic bronchitis
and peribronchitis, especially in the infraclavicular and lower, but
also in the upper and lateral parts of the lungs in the form of bands
with a double contour and showing nodular swellings in their
course.
Besides these changes there occur, especially after long occupational activity and with advancing age more or less widespread,
broad, thickened areas in the lungs, mostly in the middle regions,
reaching from about the clavicle to the upper end of the lowest
third of the lung.
Dry pleuritic changes (hairlike lines in the lungs, displacement
of the diaphragm, thickened reticulated areas) are often met with
even in the case of incipient forms of porcelain workers' pneumonoconiosis; on the other hand, exuding pleurisies are seldom met
with in cases of pure pneumonoconiosis. Secondary changes of
the heart (dilatation, hypertrophy) are by no means rare in
such cases of severe pneumonoconiosis affecting porcelain workers.
Obstructed blood vessels and obstruction in the parenchyma and
interstitial spaces complicate the Röntgen picture turning it in its
entirety or in part into an inextricable chaos.
Inflammation of the lungs, bacterial infection especially accompanied by tuberculosis to which porcelain workers are beyond
doubt more liable as compared with the general population, may at
any time lead to premature death in the case of these porcelain
workers, whose lungs and circulatory organs are already impaired.
In some cases, tuberculosis was found, also cavernous phthisis
of tubercular origin affecting porcelain workers who had been
employed up to a late age; in such cases it is indeed possible to
speak of the retarded effect of indurated lung changes. No
accurate knowledge is available to enable us to ascertain how many
porcelain workers—men and women even in their early years in the
incipient stages of porcelain pneumonoconiosis, that is at the

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irritation stage, are eliminated on account of pulmonary tuberculosis infection and take up other employment or meet with premature death.
(5) Chamotte industry. — By " chamotte " is meant fired
clay with a high melting point which is ground down, mixed
with ordinary clay and fired to make bricks. This mass contains
about 70-75 per cent, of aluminium, about 2.5-3 per cent, of
spar, about 20-26 per cent, of quartz, and the total silica content
amounts to 25-30 per cent. ; the free silicic acid becomes combined
with the potassium and aluminium to a considerable extent in
the firing process (vitrifying), so that in this way the free silica
content is eventually considerably reduced: "probably free
silica is hardly present any longer in the finished article ". The
dust is relatively large grained, heavy and less volatile.
Examination was made of 234 chamotte workers. The data
provided by the investigation was so arranged that two groups
were formed according to the rontgen findings: group I with
negative or harmless roentgenological results, and group II with
positive results. Group I comprised 184 individuals (78.63 per
cent, of all examined), of whom nearly 65 per cent, had been in
the industry upwards of ten years.
Group II comprised 50 people ( = 21.37 per cent.), most of whom
were of advanced age; 92 per cent, had been in employment for
upwards of ten years. Subjective complaints predominated in
regard to this group though 20 workers made no complaints.
Clinical examination of the respiratory organs revealed for half
this group changes from the normal condition; 15 men belonging
to the group, however, showed no clinical symptoms. Rontgenologically, there was established fairly plain results of dust in
the lungs, which may be summarised thus in passing. Once
again there was revealed lack of correspondence between complaints,
and clinical and ròntgenological findings to such an extent that
workers with fairly severe objective symptoms were free from
complaints, or again that workers with subjective complaints
showed relatively slight objective signs, and so on. The Rontgen
picture showed chiefly, sparse, multiple, fine mottled isolated foci,
distributed in various ways over the lungs with masses of thickened
reticulated areas and hilum markings; the shadows were soft
and in this respect occupied a place somewhat between those of
porcelain and cement coniosis; they were relatively small with
sharp outlines. The lungs often showed a particularly wavy

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377

appearance as if sown with small grains of grit. The broad shadow
patches were distributed either uniformly over the whole lung,
the basic parts being slightly less involved, or (more rarely) over
the lateral parts of the lungs.
In general, it was possible in this case also to establish the fact
that those with a long duration of employment showed greater
injury from dust than those with a shorter record of work, that
however in spite of this fact, even in the case of a record of ten to
twenty years' work, the changes due to the presence of dust in
the lungs only attained a moderate degree. It was not possible
to observe here cases of the three stages of the disease. Almost
three-quarters of the total number of workers examined having
upwards of ten years of employment in the chamotte industry
showed no or only very harmless pulmonary symptoms on röntgenological examination. In any case the results of our investigations here were by no means without value in regard to the
distribution of injuries of the respiratory passages due to dust,
since they served to indicate that the dust raised in the manufacture
of chamotte contains little free silicic acid, but on the other hand
has a rich clay content.
(6) Shell limestone. — Shell limestone consists for the most
part as its name implies of mussel shells which are bedded in clay,
also principally of carbonate of lime and clay with, as the case may
be, an admixture of iron. Free silicic acid is not present, or at
least only in traces.
Statistical analysis of the data provided by the General Local
Sickness Fund for the Würzburg district, to which all of the more
important establishments of the Bavarian shell limestone industry
belong, showed, in the three-yearly average, that the shell limestone
workers as opposed to the remaining male members insured, were
more favourably placed both as regards general morbidity rates
and morbidity rates for respiratory diseases, including pulmonary
tuberculosis.
Likewise the mortality rates would appear to be by no means
less favourable than those for the general male population. The
first (merely anamnestic-clinical) examination covered 200 workers,
of which 72 per cent, had been upwards of ten years in employment.
Two-thirds of them were designated as quite healthy; in the case
of one-third only slight symptoms of the respiratory passages
were confirmed. Better results were afforded by the later clinical
röntgenological examination of a further 124 workers most of

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whom had been more than ten years in employment ; of these 81
had previously worked exclusively in the shell limestone industry
(Group I); 14 of these showed dust deposits in the pulmonary
tissue with no complaints or very slight complaints. Rontgenologically there was found in 8 of those examined large hilum
glands, at times with a brighter nucleus and a thicker capsule.
Four examinations revealed sparse fine mottled foci distributed
over the lungs irregularly, and atypical as regards site; in 2 cases
there were fine mottled foci with nodes in the hilum. The fine
mottled foci were soft in shadows, not very thick and at the same
time fairly plainly outlined in contrast to their surroundings.
That fine mottled foci are seldom found in the lungs of limestone
workers, in spite of the dust evolved during the work, is partly explained by a certain solubility of lime dust in the respiratory
passages, by its rapid elimination, and partly by the tendency
of lime particles to coalesce and so to become too big to penetrate
into the deeper respiratory passages. They irritate the mucous
of the larger bronchial tubes and are in part reabsorbed and in
part eliminated. It is seen from these investigations, that also
limestone under certain circumstances may cause alteration of
the lungs as indicating pneumonoconiosis if only it is allowed to
exercise its effect for a sufficiently long time. Still these pictures
are clearly distinguished from Rontgen pictures for instance of
sandstone or porcelain workers. Group II (43 workers) had also
manipulated sandstone for some time as well as shell limestone,
29 of them having handled more shell limestone and less sandstone
(M workers)—14 the opposite (S workers). In the case of the
M workers, 13 showed a normal condition of the lungs, 6 border
symptoms and only 10 (34 per cent.) lungs with a dust deposit. Of
the S workers, on the other hand, 10 (71 per cent.) showed clear
changes in the lungs due to dust.
If Groups I and II be compared it is found that in manipulating
pure shell limestone (Group I) the percentage figure for negative
pulmonary cases is by far the predominant one and the figure
for clear cases of pneumonoconiosis is considerably less, whilst
under the influence of sandstone dust (Group II) these relations
are reversed. It may be deduced therefrom that work amongst
sandstone even when—and this is almost constantly the case
amongst our people—work has only been carried on for a few
years (mostly three to five or to eight) and when years and decades
have already elapsed since the employment in question, always
leaves traces in the pulmonary tissues, which it is true very often

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remain latent from a subjective or clinical point of view, but can
nevertheless be " brought to light " by the Rontgen rays. Whether
and to what extent the later work among shell limestone may have
influenced favourably the residual effects of work among sandstone
we do not dare to decide with certainty.
As far as the Rontgen picture in particular for Group II (combination of earlier work among sandstone with later employment
in an atmosphere of shell limestone dust) is concerned, the following comprehensive account may be given: in this group there are
found clear pictures of sandstone coniosis resembling those above
described; there may be recognised in this case in the typical
pictures of lungs resembling grains of small shot the one-time
influence of a mineral dust with a high quartz content on the lung.
There are found in part also on lung pictures with typical sandstoneconiosis foci resembling those found in shell limestone-coniosis:
less profound shadows than in the case of the fine shot shadows,
with fairly sharper outlines ; also enlargement of the hilum glands
and thickened areas are found. It is true that under the influence
of subsequent work in an atmosphere of shell limestone the traces
and effects of earlier work on sandstone had not been—or at least
had not been constantly—eliminated but have rather persisted.
(7) Cement. — In cement dust (lime-aluminium-silicate)
there is found 19-26 per cent, of silicic acid, though in general
combined with calcium oxide and alumina in a non-soluble form.
If the following morbidity rates are made to refer to 100 workers
per annum they provide percentages as follows: diseases of the
upper respiratory passages, 6.6; diseases of the lungs (inflammation,
tuberculosis, pleurisy), 4.2; 2.4 per cent, were treated annually
for pulmonary tuberculosis (2.6 per cent, of the cases of sickness) ;
in none of the cases referred to was an abnormal duration of illness
established; most of the cases of sickness recovered after from
three to four weeks. Of the cases of bronchial catarrh none
lasted longer than thirty days; cases of inflammation of the lungs
with a duration of from three to six weeks correspond to the
clinical type; cases of delayed resolution (over fifty days) were
not observed to any extent. The mortality rate for cement factory
workers showed no difference from that for the local population
at the same ages, but rather remained considerably under the average for the district; the tuberculosis mortality rate in particular
was within ten years under the average for the whole Bavarian
population.

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The anamnestic-clinical examination of 600 cement factory
workers showed no unfavourable results; in about 10 per cent.
bronchitis, etc., was present; in about 15 per cent, of the cases
changes in the respiratory murmur as indicating a dust deposit
were observed.
Recently a further 93 workers were thoroughly examined clinically and rontgenologically, 85 per cent, of whom had been in
employment for upwards of ten years ; 79 of these showed negative
röntgenological results, though a few suffered from slight complaints ;
4 further cases showed relatively benign tubercular processes
without a considerable rôle being played by the presence of dust;
4 further cases showed border signs, 6 clear signs of pneumonoconiosis (5 of these with over ten years of occupational activity).
There was only one picture of the pulmonary form of pneumonoconiosis. The 5 remaining cases belonged to the hilar form, that
is to say, there was found enlarged and thickened hilum markings
—mostly with small thickened deposits—and thickened arborification of the hilum in parts of the lungs only, or all over. Only
2 of the cases observed by us showed these phenomena in a
pronounced form, the remainder in a slight form. Pure cementconiosis as revealed by our investigations was slight in extent and
benign; it was clearly distinguished from sandstone workers'
silicosis; the foci shadows were softer, less profound, the characteristics of the " fine shot lung " are lacking in cement workers'
coniosis. Thickened foci are also found here in isolated areas.
Now how is this relatively favourable effect of cement dust to
be explained ? The high limestone content has been alleged to be
66-67 per cent., of which the favourable influence on tubercular
processes is well known. Likewise the solubility of the cement in
water containing carbonic acid is of importance as regards the
self-cleansing mechanism of the body. Perhaps its capacity for
swelling also plays a part, and thereby facilitates the resorptive
influence of the carbonic acid (Schott and others). Most important
of all however would appear to be the fact that cement dust—in
contrast to dust with a high percentage of pure silicic acid—does
not remain free in the tissues but is greedily absorbed by the dust
cells and removed. There is lacking here—just as in the case of
lime and gypsum dust—the capacity for forming typical fibroses.
(8) Finally mention should also be made of workers engaged
in handling basalt and melaphyr chiefly in macadam factories.
The total silicic acid content is here said to amount to about 50

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381

per cent.; free (crystalline) silicic acid is however not present.
The statistical clinical examination covered 200 workers, 70 per
cent, of whom had a ten years' record of occupational activity.
Since the anamnesis as well as the clinical examination provided
no striking results, and further the analysis of the sickness returns
revealed no increased disease liability for this category of workers
as compared with similar groups in the same district, ròntgenological
examination was dispensed with.
The outcome of the examination of groups of workers exposed
to mineral dust of varying composition may be summarised as
follows :
The statistical morbidity and mortality returns, as well as in
particular the clinical-ròntgenological examinations, show clearly
that the fundamental principle is as follows : the greater the quantity of free silicic acid in the dust the more dangerous it is for the
lungs—thus it is also found in reality that in the case of occupational
groups brought into contact with substances rich in free silicic
acid (sandstone, so-called siliceous chalk, to some extent also
porcelain) there exist increased morbidity and mortality rates
from chronic lung diseases (silicosis, silico-tuberculosis) ; on the
other hand statistical returns are the more reassuring the less
free silicic acid is present in the dust in question (workers handling
cement, clay, chalk, etc.). Similar results and, in truth, still
more sharply emphasised, are provided by the Rontgen picture.
Here we find in accordance with the composition fairly characteristic
pictures relative to the dissemination, form, thickness, outline
of the shadow foci: on the one hand with the presence in abundance of free silicic acid either massed broad foci with profound
shadows or more frequently, multiple, fine mottled or nodular
foci with sharp outlines and striking depth of shadow of the isolated
foci (lungs resembling fine shot). On the other hand the lower the
percentage of free silicic acid in the dust the more the argillaceous
and calcareous elements predominate the softer, the less sharp
edged will be the outlines and the less profound the shadows—
whether it is a question of isolated foci or conglomerated shadows.
A trained research worker will in this way be able to deduct from
a good Rontgen plate the relative content of the dust in question
in free silicic acid, or the amount of clay or lime elements present,
with a fair degree of certainty.
It is not going too far to say that the róntgenologically demonstrable property of the biological reaction of the respiratory organs towards inhaled dust is a good test of the content of the dust in free

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silicic acid. Where doubt exists as to the content of inhaled dust
in free silicic acid on the basis of analyses, the Rontgen picture can
furnish in typical cases an important indication as to the chemical
activity of the type of dust in question, and its content in fine
Si0 2 , whether the latter has been contained from the outset in
the dusty product manipulated, or has been liberated during the
mechanical processes of manufacture.
We are of course quite aware that in addition to the silicate
content many other factors must be taken into consideration in
regard to the development and type of symptoms of the pneumonoconiosis: for instance, duration of work, working posture,
and especially the constitutional factor, on which later depend to
a high degree the rapidity of development of the silicosis, the selfcleansing mechanism of the lungs, the distribution of the dust
deposit and of fibrosis in the pulmonary tissue and so on. Nevertheless we desire to insist with all possible emphasis on the decisive
part played by free silica in the development of silicosis. This
knowledge appears to us to be of special import, particularly
in regard to measures of prophylaxis to be adopted by the practising
factory surgeon in isolated establishments, and also for procedure
in regard to the handling of the pneumonoconiosis problem from
the legal aspect in regard to compensation.

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Supplement (52 pages, 15 X-ray plates).
KAESTLE, K. " Ueber die Pneumonokoniose der Sandstein-, Kieselkreide-,
Porzellan-, Granit-, Zement-u. Muschelkalkarbeiter." Lecture printed in:
Die gewerblichen Staublungenerkrankungen, Supplement 15 of the Zirbi, f.
Gewerbehyg. Berlin, J. Springer, 1929.
" Ueber Porzellanlunge: Vortrag b. d. Tagung der Süd und Westdeutschen Röntgengesellschaft in München. " Fortschritte auf dem Gebiete
der Röntgenstrahlen, Vol. XXXVII, No. 3.
" Ueber die Pneumonokoniose der Sandstein-, Kieselkreide-, GranitMuschelkalk- und Zementarbeiter. " Forschritte auf dem Gebiete der Röntgenstrahlen, Vol. XXXVIII, No. 6

SILICOSIS IN GREAT B R I T A I N
BY

E. L. MIDDLETON, M.D., D.P.H.,

H.M. MEDICAL

INSPECTOR

FACTORIES

INTRODUCTION

The aim of this paper is to bring within review the industries and
processes in which the workers are exposed to the inhalation of silica
dust. Throughout, the use of the word " silica " has been confined
to the dioxide of silicon, SiOa, as it occurs free in nature in the form
of quartz, flint, chert, etc. Although materials are dealt with which
contain free silica mixed with other substances either naturally, as in
granite, or artificially, as in earthenware, no substance is regarded as
coming within the scope of this paper in which the silica is wholly
united with other elements in chemical combination. It is necessary
to make this limited application of the word " silica " quite clearly
understood, because the compounds known as silicates will, sooner or
later, have to be studied systematically as the causes of pulmonary
disease in industry. There is abundant evidence already that the
silicates cannot be regarded as a single group showing a uniform effect
on the pulmonary tissues and producing the same results of disablement
and death of those affected. There is also sufficient evidence to show
that the action of the silicates is different from that recognised as
typical of the action of free silica.
One of the problems raised by bringing together facts such as are
grouped in this paper is that relating to the action on the lungs of
mixed dusts. While it appears to be true that free silica tends to
produce its characteristic effects whether inhaled alone or in admixture
with other dusts, it seems equally true that its action is influenced
to a greater or less extent by such dusts. When the accompanying
dusts happen to be silicates which are capable themselves of producing
effects, the resulting changes in the lung tissues, the influence on
function and the reaction to infections become extremely complicated.
The need for close investigation of all the possible circumstances
in which these dusts produce destruction of function is emphasised by
observation of the cases of disablement and death which are brought
to light at the present time, more or less by hazard.
The principal facts regarding the action of silica are generally
accepted, but we are still far from being able to explain the apparently

SILICOSIS IN

GREAT

BRITAIN

385

unequal results of exposure to the inhalation of even unmixed silica
dust. To gain a better understanding of this problem it is necessary
to place side by side as much of the evidence as can be brought
together, from all sources where the problem exists.
The scope of this paper is confined almost entirely to matters which
have come to the notice of the writer as Medical Inspector of Factories
in the Factory Department of the Home Office. In the sections
on mining, material has been supplied and guidance given by
Dr. S. W. Fisher, H.M. Medical Inspector of Mines, whose help is
gratefully acknowledged.
A number of dust-counts have been included in this paper. These
have been made during various investigations within the last eight
years. The instrument used for collecting the samples was Owens'
jet dust-counter, and for counting, a microscope giving a magnification
of from 900 to 1,000 diameters was used. In all cases, unless otherwise
stated, all particles over about half a micron in size are included in
the total count. In most cases an estimate is given of the proportion
of the total number of the particles which appeared to consist of the
dust under investigation, as distinguished from soot particles which
constitute the greatest difficulty in accurate counting in most of these
cases. The technique employed is similar to that described
in the
Annual Report of the Chief Inspector of Factories, 1922 l.
Each industry or process has been dealt with as far as possible
under the following heads: definition; distribution geographically;
employed persons; operations and processes at which silica dust is
liable to be inhaled; special character of the silica dust and reference
to other dusts and other modifying conditions as to the form and
concentration of dust in the atmosphere; evidence of silicosis being
produced; methods of prevention and special legislation; compensation.
The industries and processes include (1) refractory materials;
(2) grinding of metals; (3) sandstone; (4) granite; (5) slate; (6) coal
mining; (7) tin mining; (8) pottery; (9) sand blasting; (10) silica
milling; (11) scouring powders; (12) flint crushing; (13) flint knapping;
(14) millstone dressing.
References to the literature and official papers are given at the end
of each section.
General Bibliography
(1) " Industrial Pneumonoconioses with Special Reference to Dust
Phthisis." By Dr. E. L. COLLIS. Public Health, 1916; and reprinted by
His Majesty's Stationery Office, 1919. Price 2s.
(2) " The Aetiology of Silicosis." By Dr. E. L. MIDDLETON. Tubercle,
March 1920.
(3) " A Study of Pulmonary Silicosis. " By Dr. E. L. MIDDLETON.
Journal of Industrial Hygiene, March 1921.
(4) " Tuberculosis Infection and Tuberculosis as modified by Experimental
Pneumonoconiosis. " By Dr. L. V. GARDNER. Tubercle, April and June,
1925.
(5) " Silicosis and Tuberculosis." By Dr. J. LOGAN STEWART. British
Journal of Tuberculosis, Jan. 1929.
(6) Report of the Departmental Committee as to the Medical Arrangements
which could be made for the Diagnosis of Silicosis. Home Office Report. His
Majesty's Stationery Office, 1929. Price 6d.
1

Cf. General Bibliography, No. (7).
25

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PAPERS PRESENTED TO THE

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(7) " Investigation into the Dust Content of the Atmosphere of Workplaces
in the Grinding of Metals and Cleaning of Castings. " By E. L. MIDDLETON,
M.D., D.P.H. Annual Report of the Chief Inspector of Factories for 1922. His
Majesty's Stationery Office, 1923.
REFRACTORIES

INDUSTRY

For the purposes of legislation it has been necessary to define
this industry, so far as the use of silica is concerned, in its limited
sense. For this purpose the term " refractory materials " refers
to materials used in the construction of furnaces, flues, crucibles, etc.,
on account of their resistance to heat, when they are subjected
to the cutting action of flue gases, the influence of slags, and of
sudden changes in temperature x ; and in the making of moulds in
which metals are cast. They contain over 80 per cent, of silica.
The refractory materials in the raw state consist of silica rock
of high silica content, usually from 92 to 98 per cent. They include
ganister, quartzite, siliceous sandstone, quartz-schist or conglomeratic quartzite 2. Natural sand, flint and chert also may be used.
Distribution
These materials are widely distributed throughout this country.
The chief sources of supply are Yorkshire, Derbyshire, Cheshire, North
and South Wales, Durham and the south of Scotland, that is to say,
in the coal measure districts. In the majority of cases the materials
are manufactured near the spot where they occur in the quarries
and mines.
Employed Persons
About 3,000 persons are employed at present in the industry,
of which about 5 per cent, are women.
Processes
Various processes, from the quarrying or mining of the raw
material to the handling of the finished product, may give rise
to dust.
The raw material may be in the form of natural sand, as from
the pocket clays of Derbyshire and deposits in the south of England.
In getting out this material from the quarries or. sandpits, the
exposure to silica dust, though by no means absent, is relatively
slight, for two reasons : (a) the grains of sand are of too large a size
1
2

Cf. Bibliography, No. (1).
Cf. Bibliography, No. (2).

SILICOSIS IN GREAT BRILAIN

387

to be inhaled; (¿>) there is always moisture present, from about
5 to 15 per cent., which fixes the finest particles. In addition to
the action of the moisture, aggregation is assisted by the presence
of a pellicle of kaolinitic material—of considerable importance
from the health point of view since even when the material has
been dried, crushed and made up into bricks, there remains a
tendency for the minute particles to adhere so as to form aggregates
too large to be inhaled. This protection, however, is only partial,
and counts of atmospheric dust taken with Owens' dust-counter,
for example, at making silica bricks and setting bricks in the kiln,
show 1,000 to 3,000 particles per c.c. of air.
Quarrying and mining of solid rock involves definite exposure
to silica dust, even when the surface of the rock is wet. Drilling,
blasting and breaking with hammers, are always attended by the
liberation of much fine dust. In these processes the action of the
wind in removing the dust from the breathing point of the worker
is one of the most important safeguards. The processes of crushing,
grinding and sieving, which are usually carried on in more or less
open sheds ; mixing the materials into a plastic form for the manufacture of bricks and the subsequent manipulation by hand in
moving the bricks to and from the drying floors, are attended by
evolution of dust. Setting the dried bricks in the kilns is one of the
most dangerous processes in the industry, and it is extremely
difficult to solve the problem of dust suppression, since the use of
moisture or exhaust draught is practically impossible. The use
of a respirator for this process, if a suitable one could be devised,
standardised to protect even to 50 per cent, efficiency, would be a
useful measure, possibly with alternation of occupation, though
this is a specially skilled job with ordinary kilns. The solution of
the problem probably lies in the use of kilns which do not have to
be entered and in which no skill is required.
Evidence of Silicosis being Produced
From 26 February 1911 to 18 December 1916, 36 deaths of
ganister workers in the Stocksbridge district of Yorkshire showed
24 deaths due to phthisis and " ganister " disease ; other respiratory
diseases accounted for 5 deaths.
The Reports of the Medical Board of the Refractories Industries
(Silicosis) Scheme show cases of silicosis or silicosis with tuberculosis
certified from the time of appointment of the Medical Board in
May 1925 to the end of 1928, as follows:

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PAPERS PRESENTED TO THE CONFERENCE

TABLE I
Without
impairment of
capacity

With impairment

Total disablement

Death

Suspended
for
tuberculosis
only

1 May 1925 to
31 December 1926

1 J a n u a r y 1927 to
31 December 1927

1 J a n u a r y 1928 t o
31 December 1928

Period

Records of 18 post-mortem examinations of the fatal cases
in 1928 show that 9 were certified due to silicosis and 9 to silicosis '
with tuberculosis.
Of the former group the average age was 59 years and the
average period of employment in the refractories industries was
22.6 years. In the latter group the average age was 49% years
and the average period of employment 17.6 years.
A complete description of the pathology of a ganister miner's
lung, affected by silicosis with tuberculosis, is given in the Annual
Report of the Chief Inspector of Factories, 1900, pages 487 to 494,
with illustrations and chemical analysis of the ash. The amount
of inorganic ash found in two samples formed 3.20 and 3.01 per cent.
of the weight of dried lung. Silica, present as Si0 2 , was 24 and
36 per cent, respectively of the inorganic ash, the remainder being
chiefly iron, aluminium and calcium.
Prevention
Reference has already been made to the subject of prevention
in this industry. For mining and quarrying with pneumatic drills,
water supplied through the hollow drilled steel is a partial remedy.
Suction with collection in a specially constructed bag filter is
applicable. At crushing, grinding and other processes with the use
of machinery, efficient exhaust draught combined with the use
of water or steam spray, is nearly always possible. Moving materials
on drying floors and to and from kilns is very difficult to control
and calls for constant vigilance and cleanliness.
Refractory Materials Regulations have been in force since
April 1919. They provide for suppression of dust on the lines
indicated.

SILICOSIS IN GREAT BRITAIN

389

Compensation
The first scheme of compensation for silicosis was made for the
refractory industry in 1919, under the Workmen's Compensation
(Silicosis) Act, 1918, and came into operation on 1 February 1919.
From that date until the end of 1928 awards of compensation have
been made in 423 cases, including 121 cases of death. The present
scheme, made under the Workmen's Compensation (Silicosis)
Acts, 1918 and 1924, came into force on 1 May 1925. It provides
for a Medical Board for the purposes of certification and periodic
medical examinations.
Bibliography
(1) Refractory Materials. By A. B. SEARLE. 1917.
(2) Memoirs of Geological Survey. Special Reports on the Mineral
Resources of Great Britain. Volume VI : " Refractory Materials, etc. :
Resources and Geology ". His Majesty's Stationery Office, 1918.
(3)
Vol. XVI : " Refractory Materials : Petrography and Chemistry. "
His Majesty's Stationery Office, 1920.
(4) British Resources of Refractory Sands for Furnace and Foundry Purposes
Part I. By P. G. H. BOSWELL, O.B.E., D.Sc, London. Taylor and Francis.
1918.
(5) Annual Report of Chief Inspector of Factories for 1900. His Majesty's
Stationery Office, 1901.
(6) Manufacture of Silica Bricks and Other Refractory Materials used in
Furnaces, with special reference to the effects of Dust Inhalation upon the Workers.
By W. SYDNEY SMITH and E. L. COLLIS, M.B.

His Majesty's

Stationery

Office, 1917.
(7) Report of Departmental Committee on Compensation for Industrial
Diseases. Command 3495. His Majesty's Stationery Office, 1907.
(8) Second Report of Royal Commission on Metalliferous Mines and Quarries.
Command 7476. Part XIV. His Majesty's Stationery Office, 1914.
(9) Workmen's Compensation Act, 1925. 15 and 16 George V, Chapter 84.
His Majesty's Stationery Office.
(10) Refractories Industries (Silicosis) Scheme, 1925. Statutory Rules and
Orders, 1925, No. 79. His Majesty's Stationery Office.
(11) First Report of the Departmental Committee on Compensation for
Silicosis dealing with the Refractories Industries (Silicosis) Scheme, 1919.
His Majesty's Stationery Office, 1924.
(12) Regulations for the Crushing, Grinding and Sieving of Refractory
Materials and other Processes involving the Manipulation of such Materials.
Statutory Rules and Orders, 1919, No. 514. His Majesty's Stationery Office.
(13) Workmen's Compensation : Statistics of Compensation and Proceedings
for 1928. Command 3481. His Majesty's Stationery Office, 1930.
GRINDING OF METALS

In relation to silicosis the processes concerned in the grinding of
metals are confined to those in which grindstones composed of
natural or artificial sandstone are used.
The grinding of metals may properly be said to include, in
addition to the actual grinding, those processes incidental to it

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which are carried on at the factory where the grinding takes place ;
these are: (1) racing, (2) hacking, and (3) rodding or scaring of the
grindstones.
Distribution
The principal divisions of the industry and the chief centres at
which they are carried on are as follows : (a) steel knives and forks,
scissors, razors, surgical instruments—Sheffield; (b) saws, knives
for plantation work, metal cutting and woodworking, reaper
sections, chisels, augers, screwdrivers and similar tools—Sheffield,
Birmingham and Glasgow; (c) scythes, sickles and shears—
Sheffield and Worcestershire; (d) edge tools—Birmingham district
and Sheffield ; (e) files—principally Sheffield, also other engineering
centres;
(/) textile machinery and components—throughout
Lancashire and Yorkshire, also in Cheshire, Scotland and Belfast;
(g) stoves, grates, ranges—principally Falkirk, also various other
districts; (h) locomotive parts—principal railway centres.
Grindstones are obtained chiefly from the millstone grit
sandstones from Derbyshire and the Sheffield and Newcastle
districts.
Employed Persons
Reports compiled for January 1926 showed the persons employed
on grindstones to be 3,710. In addition, some 3,600 persons were
employed in other processes within a radius of 20 feet from the
grindstones.
The figures for the different trades are as follows :
TABLE II

Trade
Cutlery: Sheffield
Other districts
Edge tools : Sheffield
Midlands
Other districts
File grinding: Sheffield
hand
machine
Textile machinery
Locomotive and general
engineering
Stoves, grates, etc.
Foundries
Miscellaneous

Number
ot stones

Numbers employed
Others in
Grinders
proximity

880
107
623
303
166

882
93
660
282
145

510
100
400
131
200

200
130
550

120
110
471

583

378
163
147
292

369
148
153
277

824
162
286
389

3,939

3,710

3,585

391

SILICOSIS IN GREAT BRITAIN

Since the time these figures were prepared, there has been a
considerable increase in the number of manufactured abrasive
wheels brought into use to replace sandstone wheels. This of
course has the effect of removing the workers on these grindstones
from processes under review and therefore from the risk of silicosis,
properly so called, although the latent liability to the disease
from exposure in the period of employment remains.
The Inspector of Factories in Sheffield reports that a rough
census of the number of grindstones in use in Sheffield in 1926
and in 1929 records a notable change towards the artificial wheels
during the three years. The numbers are:
Cutlery and edge tool trades . . . .
Miscellaneous grinding (by hand) . .

1926

1929

1,540
70

654
8

An estimate of the number of grindstones and artificial abrasive
wheels in use at the end of 1929 is as follows :
Grindstones
Hand grinding cutlery and edge tools
Machine grinding circular saws. . .
Machine grinding files
Machine grinding long saws . . . .

468
31
104
51

Artificial
wheels
966
13
5
8

654

992

Operations and Processes
Males only are employed on grinding on sandstone. In the
Sheffield trades the hand-grinders serve a term of apprenticeship
commencing just after school age. Machine-grinding is done by
men who have worked for a time at hand-grinding or some other
trade. Occasionally racing of grindstones is done by labourers,
but usually it is done by the grinders themselves.
For the purpose of this paper reference is made only to grinding
when mechanical power is used in moving the grindstone. In a
few factories, in the Sheffield district especially, water power is
used; in the great majority of cases steam or internal combustion
engines are used.
Grinding may be done wet or dry, and the metal being ground
may be moved by hand or by mechanical power on a machine.
In wet grinding, the grindstone is mounted on a horizontal shaft,
and water is laid on from a tap or spray above the stone, or the
lower part of the stone dips to a small extent into a trough beneath

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it containing water. It is sometimes contended by grinders that the
grit which collects in the water of the trough from attrition of the
stone is necessary for the process, but in some cases the trough is
drained, the water being laid on at the top of the stone. The wet
grit mixed with particles of metal produced in grinding is known
as " swarf ".
In wet hand-grinding the grinder sits on a heavy saddle-shaped
stool called the " horsing ", or straddles on a suspended board.
He exerts considerable pressure on the metal which he holds in
his hands, or when a suspended board is used a metal piece on the
front of this is used to increase the pressure. Except in a few special
kinds of grinding, the grindstone revolves in a direction away
from the grinder. In wet hand-grinding localised exhaust draught
is only rarely provided.
In dry hand-grinding the metal parts being ground are usually
of small size, and localised draught is always provided. The
grindstones revolve either towards or away from the grinder,
depending on the class of work.
Wet grinding is also done by machines, especially in the manufacture of files, saws, large machine-knives and reaper-knives.
In this form of grinding the metal being ground is fixed in a part
of the machine which moves under or across the revolving grindstone.
The processes of dressing the grindstones are very important
from the health point of view, on account of the amount of dust
produced. They are " racing ", that is, trueing the surfaces of the
grindstone before it is brought into use for the first time; and
" hacking " and " rodding " or " scaring ", which are processes
of dressing the grinding face of the stone and are carried out
frequently in the course of a day's work.
Characters of the Silica Dust
Attrition of the grindstone occurs in all processes in the
grinding of metal, and varies in amount with the consistence of
the stone, the hardness of the metal, the shape of the article being
ground, and the amount of force exerted, and thus depending on the
extent to which the stone is cut in the process. Dust is produced
as a result of this attrition; its composition corresponds with
that of the grindstone, with some added particles from the metal
articles being ground. It is doubtful if the metal particles are
inhaled in any substantial amount, as they are present only to a
very small extent in atmospheric samples of dust.

SILICOSIS IN GREAT BRITAIN

393

The amount of dust produced varies within very wide limits
in different classes of grinding, and under varying conditions.
Gravimetric estimations show that in steel table-blades wet handgrinding, for example, from 88 to 220 milligrams of dust per
10 cubic metres of air were present in the atmosphere at breathing
level. Numerical estimation with Owens' dust-counter shows as
an example of a high count at hand-grinding of scythes, 3,205 particles in 1 c.c. of air (in a district where other dusts were at a
minimum). Even higher counts are obtained at the processes of
racing and " scaring ". These counts include dust which occurs as
free particles in the atmosphere. In addition, dust contained in
droplets of moisture, that is, " swarf ", are also potential sources
of danger when they become dry. An example of the amount of
dust contained in a droplet was obtained by counting the particles
deposited on a microscope cover-slip in wet hand-grinding
table-knives. The dry deposit from the droplet measured 2 millimetres in diameter and the particles composing it numbered, by
counting and calculation, 4,383. They appeared to consist entirely
of particles from the grindstone and measured from 24 ¡u down
to the limit of visibility under a magnification of 900 diameters.
The size of the particles produced in the grinding of metals on
sandstone wheels and found in the atmosphere at the breathing
level of the worker, is found by the microscopic examination of
samples taken with Owens' dust-counter. As a rule the samples
show that from 90 to 97 per cent, of the sandstone particles are
under 2 ^ in greatest diameter, i.e. are capable of being inhaled
into the alveoli of the lungs.
The grinding of metals on sandstone wheels has been recognised
for generations as a cause of silicosis and increased mortality from
tuberculosis. Especially in Sheffield " grinders' rot " has been
notorious and past records of that city show the effects of this on
the mortality rates *.
Statistics are not available for silicosis as a separate disease, but
reference is continually made to high mortality rates from tuberculosis. In the city of Sheffield such statistics are kept very carefully with reference to the occupation, so that figures from that
city may be quoted.
For the five years 1923 to 1927, the numbers of deaths of grinders
from pulmonary tuberculosis were 34, 35, 31, 28 and 38. On the
basis of the Census of 1921 this gives mortality rates per 1,000 grin1

Cf. Bibliography, No. (1).

394

PAPERS PRESENTED TO THE CONFERENCE

ders living of 6.9, 7.2,6.3, 5.7 and 7.8,contrasted with rates amongst
all persons over fifteen years of age of 1.2, 1.1, 1.1, 1.0 and 1.0
respectively.
These figures agree closely with those of an investigation carried
out at the Sheffield Municipal Tuberculosis Dispensary into the
particulars relating to all persons over the age of fifteen who died
during 1919 and 1920 of pulmonary tuberculosis and who had
been examined by the tuberculosis staff and the diagnosis confirmed
by them. The mortality rate for grinders in this series was 7.02 per
1,000 living while the rate in the general population of Sheffield
was approximately 1.0 per 1,000 living.
Dr. Rennie, Chief Tuberculosis Officer for the city of Sheffield,
has provided data which show that in 1928, 25 grinders died of
silicosis with or without tuberculosis, and in 1929 (1 January to
22 November) 29 died from these causes. The average age in 1928
was 49.4 years and in 1929, 54.8 years.
The following table includes particulars of 11 fatal cases, which
have come to the notice of the Factory Department and in which
the diagnosis has been verified by post-mortem examination:

TABLE III

No.

Age

(i)

(2)

(3)

(4)

Textile
machinery

Grindstone
dresser

I n d u s t r y Occupation

Edge
tools
Files

Files
Iron
foundry
Cutlery

Duration
of
symptoms

Period
of
disablement

Cause
of
death

Remarks

(5)

(6)

(7)

(8)

(9)

Years
10

20 m o n t h s

Silicosis and
tuberculosis

Left lung weighed

Silicosis and
tuberculosis
Silicosis and
tuberculosis
Silicosis and
tuberculosis
Silicosis and
tuberculosis
Silicosis and
tuberculosis

Died of
haemoptysis

8 months

Grinder

20 years

Handgrinder
Handgrinder
Grinder of
castings

1 year

6 months

6 years

8 months

2 years

16 months

5 months

|lì

Period
of
employment

Edge
tools

Grinder

11 m o n t h s

Files

2 years

Files

Handgrinder
Handgrinder

Grinder

11.

Edge
tools
Textile
machinery

Grinder

3 weeks

1 month
4 days
6 months
13 months

2 years
4 years

2 months
11 weeks

Acute pneumonia and
silicosis
Silicosis and
tuberculosis
Silicosis and
tuberculosis
Silicosis and
tuberculosis
Silicosis and
bronchitis

3 6 07.S.

R i g h t lung
weighed 28 ozs.
Died of
haemoptysis

Tuberculosis of
knee at time of
death
X-ray showed
silicosis 13 months
before death
Tuberculous meningitis at time
of death
Did much
" racing " of
grindstones

SILICOSIS IN GREAT BRITAIN

395

Characters of the Disease
" Grinders' rot ", the name formerly given to the silicosis occurring in metal grinders on sandstone, is a type frequently associated
with tuberculosis. The period of exposure required appears to
vary much with the concentration of the dust in the atmosphere.
A grindstone dresser who was employed in a large textile machinery factory, dressing about seventy stones a week, died of silicosis
with tuberculosis after six years of the work, that is, over a period
of ten years, four of which were spent in the army.
In the case of grinders, who do their own racing and dressing
of the stone, the duration is usually from twenty to forty years,
commonly about thirty-five years.
There appear to be two types of the disease : one in which tuberculosis supervenes, the commoner form, and a non-tuberculous
type in which pneumonia, oedema of the lungs and heart
failure occur. The first form usually shows only a short period of
symptoms before the onset of tuberculosis, which usually runs
a rapid course, and is frequently marked by severe haemoptysis.
In the second form, symptoms appear later in life with increasing
dyspnoea, while the clinical examination discloses greatly diminished
air entry in the lungs, especially the bases.
The morbid anatomy of the two types is rather distinctive.
In the common tuberculous form, there are large irregular areas
of consolidation showing more or less caseation and breaking down.
Usually there remains some lung tissue relatively free from tubercle
and in this the nodules of fibrous tissue can be made out. The
pleurae are densely and extensively adherent. In the nontuberculous form the lungs are usually bulky, studded throughout
with fibrous nodules, often discrete and with the intervening tissue
showing emphysema and pneumonic change. The pleural surfaces
are covered with discrete whitish nodules.
Methods of PreventionThere are two codes of Regulations made under section 79 of
the Factory and Workshop Act, 1901. One of these codes, the
Grinding of Metals (Miscellaneous Industries) Regulations, 1925,
came into force on 1 November 1926, except that in certain of these
Regulations involving structural alterations application was
deferred for a period of two years. The other code, the Grinding

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of Cutlery and Edge Tools Regulations, 1925, came into force on
1 January, 1926, except t h a t the application of Regulations
requiring certain structural alterations was deferred until three years
later. So far as they are concerned with suppression of dust in the
grinding of metals and dressing of grindstones, the provisions
of the two codes are similar, that for the cutlery and edge tools
being generally somewhat more stringent. These two codes replace
a single code of Regulations which came into force on 1 December 1909. The requirements of the Regulations are as follows:
(1) A hood and duct with localised exhaust draught must be
provided for all racing, dry grinding or glazing.
(2) Racing must be done in a separate room in cutlery and edge
tools shops, excepting shops in use before January 1926. In these
shops it is allowed to be done when no other work is going on in the
shop, provided the shop is cleaned before work is resumed.
(3) General exhaust and inlet ventilation must be provided,
adequate to secure a continuous movement of air from the grinder
and to renew the air of the room, twelve—in the case of cutlery and
edge tool shops, fifteen—times per hour.
(4) Wet grinding must be carried on in a separate room from
glazing or other processes.
(5) An adequate supply of water is required for " hacking " and
" rodding ", or alternatively adequate provision for intercepting the
dust.
(6) The rooms must be of a certain minimum height, windows
must be adequate, properly glazed and kept clean.
(7) Floors and walls must be so constructed as to be capable of
being cleaned, and all belts, shafts, etc., efficiently covered.
(8) There must be adequate drainage for water.
(9) All floors, walls, ceilings and fixtures must be cleaned periodically.
(10) Spitting is prohibited.
(11) Cloakroom accommodation must be provided.
(12) Grindstones must not be less than the prescribed distance
apart.
Since these Regulations came into force considerable success
has followed efforts to attain improvement in the methods of dust
suppression in both the racing of grindstones and in grinding of
metals. Two inventions have been introduced for removing dust
at racing of grindstones, which provide powerful suction downwards
through the trough over which the grindstone is hung. In one case
the process is done dry and the dust is removed by a short wide duct
to a portable bag filter. The efficiency of the localised exhaust
apparatus appeared to be of a high order when tested by atmospheric air samples, as it effected a reduction in the number of
stone particles from about 5,000 to 800 in a cubic centimetre.
The other arrangement consists of a copious supply of water laid

SILICOSIS IN GREAT BRITAIN

397

on at the point of contact of the racing tool and the provision of
an exhaust duct connected up with a main exhaust trunk. The
application of the exhaust downwards in both cases leaves the view
of the operator and his access to the grindstone unrestricted.
An apparatus has been brought into use recently for providing
exhaust draught in wet hand-grinding on grindstones. Tests
of atmospheric dust showed a considerable reduction in the number
of particles. The increasing use of machine-grinding and extensive
replacement of grindstones by artificial abrasive wheels, which
are more readily adaptable to methods of dust suppression, may be
regarded as important factors for the future reduction of cases
of silicosis in the grinding of metals.
Compensation
A scheme of compensation was made for metal grinders under
section 47 of the Workmen's Compensation Act, 1925. This scheme
is on different lines from those for the refractories and sandstone
industries in that it applies substantially the procedure under the
Workmen's Compensation Act in regard to scheduled diseases. It
provides for payment of benefits only in cases of total disablement
and death.
Bibliography
(1) Vital Statistics of Sheffield.
By G. CALVERT H O L L A N D . 1843. (Pages
198-199.)
(2) Industrial
Pneumonoconioses.
Milroy Lectures. By E . L. COLLIS,
M.B.
His Majesty's Stationery Office, 1919.
(3) Report on the Grinding of Metals and Cleaning of Castings, with special
reference to the effects of Dust Inhalation upon the Workers.
B y E . L. MACKLIN
a n d E . L. M I D D L E T O N , M.D. His Majesty's Stationery Office, 1923.
(4) " Hygiene of the Steel T r a d e . " By Dr. J . M. B E A T T I E . Journal of
the Royal Sanitary Institute, 1912.
(5) Report of the Departmental Committee on Industrial Diseases.
Command
3495. His Majesty's Stationery Office, 1907.
(6) Workmen's Compensation Act, 1925. 15 and 16 George V, Chapter 84.
(7) The Metal Grinding Industries
(Silicosis)
Scheme, 1927.
Statutory
Rules and Orders, 1927, No. 380. His Majesty's Stationery Office.
(8) Report on the Draft Regulations proposed to be made for Factories in
which the Grinding of Metals and Racing of Grindstones is carried on. By
A. H . L U S H . Command 4913. His Majesty's S t a t i o n e r y Office, 1909.
(9) Regulations for the Grinding or Glazing of Metals or Processes incidental
to the Grinding of Metals or the Cleaning of Castings.
S t a t u t o r y Rules a n d
Orders, 1925, No. 904. His Majesty's Stationery Office.
(10) Regulations for Grinding or Glazing or Processes incidental to Grinding
in, or incidental to, the Manufacture of Cutlery, Edge Tools, Swords,
Bayonets,
Files, Saws, Ploughs or other Cutlery or Piercing Implements of Iron or Steel.
S t a t u t o r y Rules and Orders, 1925, No. 1089. His Majesty's Stationery Office.

398

PAPERS PRESENTED TO THE CONFERENCE

SANDSTONE

INDUSTRY

The sandstone quarrying and dressing industry represents
perhaps the most widespread of all silicosis-producing industries.
The sandstones include the sedimentary silica rocks and t h e
industry covers all processes in getting the material from the
quarry or mine and the manipulation of the material with a view
to manufacture, sale, or use.
Distribution
To a great extent processes in cutting, shaping, dressing, and
crushing of the stone are carried out near the places where it is got
from the quarry or mine. Thus, the industry finds its most important
centres in the sandstone producing districts, the northern, central
and south-western countries of England, and the south and east
of Scotland.
Employed

Persons

About 12,000 men are at present employed in the industry in
getting the stone and in processes carried on in the same premises
or in the same ownership as the quarries or mines. In addition to
this there are masons and others employed in masons' and builders'
yards throughout the country.
Operations and Processes
The workers include rock-getters, who work at the stone face
in quarry or mine ; quarrymen or stonecutters who rough hew the
blocks; masons who shape and carve the stone to dimensions or
patterns; planers, sawyers and turners who operate stone-cutting
machines ; drillers with hand (pneumatic) or steam-drills; crushermen; labourers and cranemen; and builders, " fixers " or " wallers "
who frequently do some dressing of the stone.
Characters of the Dust
The proportion of silica in sandstones varies from over 99 per cent.
in certain quartzites. In many sandstones used for building and the
manufacture of grindstones and pulpstones the silica forms from
75 to 95 per cent, of the rock. The rock consists more or less of

SILICOSIS IN GREAT BRITAIN

399

quartz grains, mixed with a variety of other minerals and held
together by a cement of varying composition and proportion.
The composition, amount and hardness of the cement are important
factors in determining the dangerous character of the dust produced.
In a series of 140 atmospheric dust determinations taken with
Owens' dust-counter in the various processes in quarrying and
dressing sandstone and granite, certain general conclusions were
reached regarding the production of dust liable to be inhaled by
the workers. The action of wind has the most important beneficial
influence for workers employed in the open. Unfortunately the
worker is not always able to stand to windward of the point of
origin of the dust produced by neighbouring workers. For example,
a sample taken at breathing level of a man dry drilling a quarried
block of Derbyshire sandstone with an Ingersoll jack-hammer,
l5/8-inch drill, gave 469 particles in 1 c.c, while another sample
taken 8 yards to leeward gave 1,867 particles in 1 c.c. The stonemason working in closed or partly closed sheds is liable to be exposed
to dust produced by his neighbours as well as on his own work.
Danger is increased by the practice of brushing the dry dust and
debris from the surface of the stone and by blowing with the mouth
while carving.
Wetting the surface of the stone by rain has some influence in
diminishing dust, more especially in " getting " the stone from
the quarry, but it has little effect in reducing the fine dust given
off by the action of a cutting tool.
Stone-crushing plants are frequently found in quarry sites for
using up rubble for making road material. At the crushers, elevators
and screens, dense clouds of dust are frequently given off and travel
for considerable distances, so that though few workers may be
employed on the crusher-house plant, many may be subjected to the
dust produced by it.
Particulars of atmospheric dust samples, taken with Owens'
jet dust-counter, are given in table IV.
Evidence of Silicosis being Produced
An investigation into the occurrence of silicosis among sandstone
workers was made for the Home Office by Drs. Sutherland and
Bryson and a report of the investigation was published in 1929.
During this enquiry 454 workers were examined clinically, and of
these 266 were selected for radiological examination. The results of
the examinations are collected in table V.

400

PAPERS PRESENTED TO THE

CONFERENCE

TABLE IV
Origin
of
sandstone

Process

Position

Weather

Number of
particles
in 1 c.c.

Percentage over
2 f.

Remarks

Newton,
Elgin

Cutting wedge
holes

Fine

216

do.

Dry drilling
vertical
blow-hole
do.

do.

457

Mineral particles
often very fine.
About 20 % soot
particles.
Many fine particles.
Soot negligible.
Very sparse record
— not counted.
At least 50 % soot.

do.
do.
do.
Craigleith,
Edinburgh
do.
do.

do.

Ravelstone,
Edinburgh
Corncockle,
Lockerbie,
Dumfries
do.

Locharbriggs,
Dumfries

—

Operating
In shed
planing
machine
Dressing
Open air
sandstone
with punch
Picking wedge
do.
holes
do.
do.
Shovelling
Open shed
wet
stone
into cracker
jaws
Wheeling
Open air
away barrow
from stone
breakers
Picking wedge Sheltered
from
holes
wind
At "roughing" In planing
machine
shed

do.
do.

198

do.

271

1.6

Wind,
damp

1,530

do.

1,470
1,217

1
1.3

Wet

1,759

0.5

Much s o o t , clumped
at parts.

—

6,687

3.5

—

173

Practically all particles stone.
Obvious dust.
Soot negligible.
Some splashes.

Using finishing tool

iO-ft.
to
leeward
of planing
machine

Blowing hole
clear

—

Open shed

Corsehill,
Annan,
Dumfries
do.

Bedding a
stone with
chisel
Roughing
stone
in
planing
machine
Brunton,
Turning
up
Gosforth,
very
dry
Northumbergrindstone
land
Turning
up
do.
grindstone
(wet)
Feeding grit
do.
to saw (wet)

Henwick,
Wedge holing
Alnwick,
in d r y stone
Northumberland
Scappling
do.
stone block
do.

Feeding wet
sand to saw

do.

Dressing walling
block
with scutching h a m m e r

Many mineral p a r t icles
very
fine.
About 50 % soot.
Majority of particles
are refractive.
Some soot from crane
engine.
do.
do.
Considerable amount
of soot.

5
2.5

Soot negligible.

723

Windy,
wet

698

Some aggregates.
Large n u m b e r of
very fine particles.
No soot.
Many fine particles
under 1 n. No soot.

J u s t outside shed

do.

A very sparse record.

Closed
shed

—

1,711

Some aggregates.
Very little soot.

1,470

About 10% soot.

Saw shop

—

Raining

686

do.

Saw shed

Soot particles with
few scattered mineral particles.
Sample not counted
About 50 % soot.
Some aggregates.
Obscured by much
soot. Mineral p a r t icles scanty. Sample not counted.
Soot
from
craneengine. Numerous
soot particles. Sample not counted.
Mineral particles
scanty.

SILICOSIS IN GREAT BRITAIN

TABLE iv
Origin
of
sandstone
Elsdon,
Northumberland
do.
do.
do.
do.

Process

Scappling
large block

do.
Bankend,
St. Bees,
Cumberland
do.

Lazonby,
Carlisle,
Cumberland
Remington,
Penrith,
Cumberland
Bowscar,
Penrith,
Cumberland
Hightleld,
Penrith,
Cumberland
Ousel Nest,
Bolton,
Lancashire
do.
do.
do.
Cox Green,
Bolton,
Lancashire
do.
do.
Hall Cown,
Bacup,
Lancashire

Open air

(continued)

Weather

Number of
particles
in 1 c.c.

Percentage over
2 n

614

Soot negligible. Very
few clumps.
Soot n o t included.
Nearly all particles
discrete.
Practically no soot.
No cloud of dust.

do.
do.

3,096
3,120

7
9

Drilling
on
rock face
Operating
stone planing machine
Wet drilling
sandstone

Sheltered
position

do.

Dry

265

1.3

do.

1,952

0.4

—

518

Dry

650

—

Putting
—
moulding on
dry
stone
with chisel
Operating
planing
machine
Dressing with Open shed
4 inch chisel

Remarks

Dry

do.
Cutting wedge
holes

Darney,
West
Woodburn,
Northumberland
Making wedge
do.
holes
Redgate,
Wolsingham,
Durham

Position

401

—

Cutting wedge Open air
holes

—

994

Mineral particles
scanty. Considerable
a m o u n t of soot.
Negligible mineral
particles.
About
90% soot.
About 80 % soot.
Other particles
mineral.
Small amount of soot.

Very
little
soot.
Other particles
mineral.
Refractive
particles
not numerous. Sample n o t counted.
Practically all p a r t icles are refractive.
Very few soot
particles.

Dressing a flag

do.

Wet

325

Bottoming
race on post

Open air

Wind,
raining

132

About 20 % soot.

Holing in
quarry
bottom
Dressing
dimension
block with
scutching
hammer
Dressing stone
with punch

do.

Somewlnd,
raining

319

do.

Windy
raining

Large n u m b e r of very
fine particles. Soot
negligible.
Very sparse record.

do.

Windy

156

Dry drilling
rock on post
Holing block
on post
Feeding
crusher
Dry drilling

do.

433

do.

1,132

do.

Windy,
dry

2,844

Feeding
crusher

do.

277

Dressing stone
do.
with chisel
Sawing
Saw
machine
shed

do.

Making kerb
with chisel

Masons'
shed

Britannia,
Bacup,
Lancashire

Dressing kerb
with chisel

Open shed

do.

Dry, windy

144

Raining

343

0.7

Raining
hard

1,060

951

H.O

do.

Smaller particles down
to very fine dimensions and sometimes
occur in splashes.
Many particles very
fine. No soot.
Some particles in
clumps. No soot.
No soot.
No soot.
Many fine particles,
some in splashes.
Very little soot.
No soot.
Not more t h a n 10 %
of count mineral.
Great majority of
particles soot,
mostly discrete.
No soot.
High number of large
particles.
Soot negligible.

402

PAPERS PRESENTED TO THE CONFERENCE

TABLE iv
Origin
of
sandstone
Endon,
Kerridge,
Cheshire
do.
do.
do.

Arn agili,
Masham,
Yorkshire
do.

Process

Cutting wedge Open air
holes

do.
Birchover,
Matlock,
Derbyshire

Kaimesgate,
Edinburgh

Northumberland and
Durham
do.

do.

Endon,
Kerridge,
Cheshire
do.

Windy

Number of
particles
In 1 c.c.

Percentage over
2 1*
3

About 40 % soot.

566

About 5 % soot.

222

Cutting wedge Open air
holes

Slight wind,
damp

578

1.5

Sheltered
position

N o t raining

5,181

—

Raining

469

2.2

—~

do.

Cutting race
on post

do.

Feeding
Crusher
do.
cracker
house
Controlling
—
—
machine for
dressing
grindstones
(water
applied)
P u t t i n g head Open shed W i n d y , wet
on soft freestone with
toothed
chisel
P u t t i n g head
do.
do. do.
on sandstone
with h a m m e r
and pointed
chisel
P u t t i n g a head
do.
Windy
on hard grey
sandstone
with
hammer
and
square chisel
P u t t i n g a head
do.
do.
on a closegrained stone
with hammer
and
square chisel
Planing
do.
do.

Punching
stone with
hammer
punch-tool
At planing
machine
P u t t i n g head
on stone

Remarks

524

Windy

Woodhouse,
Northumberland
Shawk white, Dressing w i t h
Cumberland
chisel
Shawk red,
do.
Cumberland
Remington,
Facing red
Penrith,
sandstone
Cumberland
with chisel
do.

Weather

Dressing d r y 2-men
stone with
shed
chisel
Cutting wedge Open air
holes
1-man
Making setts
shed

Stancliffe,
Dry drilling
Darley Dale,
Derbyshire
do.

Position

(continued)

Over 50 % soot.
Very sparse record
and a large n u m b e r
of particles are soot.
Not counted.
About 50 % soot.

1,867

3.6

482

2.5

Many very fine p a r t icles and some overlapping.
Probably
all t h e
particles are derived
from
t h e stone.
Very
little
soot
(from cranes).
All particles a r e stone.
Very few aggregates.
50 % soot particles.

1,144

4.3

All particles are stone.

1,879

0.6

Very large a m o u n t of
soot.

2,442

3.7

About 60 % mineral,
rest soot.
Many
refractive particles.

1,626

0.7

Considerable amount
of soot.

1,132

7.0

Much of stone dust
in aggregates.

916

1.8

do.

Damp

197

11.0

do.

Dry

687

14.0

do.

Raining

542

do.

Light wind
Raining

Stone particles less
than 50 % ; few
aggregates.
All particles refractive
No soot.
Many aggregates.
No soot.
Large proportion One
discrete
particles.
Soot negligible.
Some aggregates.
Soot negligible.

—

421

Over 50 % soot.

—

927

Soot negligible.

I n shed

SILICOSIS IN GREAT BRITAIN

TABLE

SUMMARY,

SHOWING

THE

403

NUMBER

WORKERS

EXAMINED IN THE VARIOUS OCCUPATIONS, AND THE NUMBER
OF CASES OF FIBROSIS AND OF SILICOSIS

Occupation

Clinical
examinations
Cases of
fibrosis

Total

171
65
115
39
14
4
15
8
5
5-4
2
2
5

122
32
72
21
1

116
33
67
23
3
2
4
7
3
3
1

454

268

Total
Masons
R o c k getters
Quarrymen
Planers
Sawyers
Turners
Q u a r r y labourers
Wallstone dressers
Drillers
Crushermen
Builders
Carvers
Labourers to masons
Cranemen
Total

Radiological
examinations

2
8'
2
2
2
2
1
1

Cases of
silicosis
57
13
33
5

1
3
266

112

These figures do not represent the proportion of affected workers
in the industry, because, for the purposes of the enquiry a large
proportion of workers were selected with longer periods of
employment, and of those selected for radiological examination a
fairly high proportion showed clinical evidence of some degree
of fibrosis.
Silicosis was found to arise in the occupations of mason, rockgetter, quarryman, planer and wallstone dresser. The presence
of the disease was verified by radiological examination in these
occupations. From the clinical evidence and from the similarity
of occupation to one or other of the above, it was concluded that
the carver, turner and driller are exposed to a risk of silicosis.
In the case of the remaining occupations no definite evidence
was obtained from radiological examination, but this does not
imply that they are all free from the risk. In the occupations
where silicosis was demonstrated by radiographic examination
the disease appeared to become more common after forty years
of age and after twenty years in the stone industry.
With regard to the varieties of stone met with during the
investigation, cases of silicosis had undoubtedly been caused in some
instances by one particular stone. In Derbyshire, stones of Darley

404

PAPERS PRESENTED TO THE CONFERENCE

Dale, Birchover, Whatstandwell and Tansley; in Northumberland
and Durham, Blaxter, Darney and Heworth; in Lancashire,
Woolton, and Lancaster, and Halifax local stones ; in the west
of England, Bristol and Forest of Dean stones. On the other hand,
no evidence could be gathered to show that there was any sandstone
t h a t could be said to be innocuous to the workman.
Although silicosis is not a reportable disease under the Factory
and Workshop Acts, the Factory Department has received from
time to time reports of fatal cases occurring in various industries,
and especially has this been the case during 1929 owing to the action
of His Majesty's Coroners in holding inquests and notifying inspectors of factories in regard, to such cases. The coming into force
in the beginning of that year of schemes of compensation for
silicosis in certain industries has probably been another reason
for bringing the matter to the notice of the Department.
Between March 1929 and January 1930, seventeen fatal cases
of silicosis have occurred in which the diagnosis has been established
by post-mortem examination, and particulars of which have been
brought to the notice of the Factory Department (cf. table VI).
Methods of Prevention
These depend on the application of: (1) copious supplies of water
or (2) exhaust draught, at the point of origin of the dust, that is,
the point of contact of the cutting tool with the sandstone. An
example of each of these methods is given.
(1) In dressing grindstones at a quarry in Derbyshire, a machine
is used on which the grindstone is laid on a table which revolves
slowly on a vertical axis. The tool is made to traverse slowly over
each of the surfaces of the grindstone, and, at the point of contact
a water pipe supplies water at a pressure produced by compressed
air in the water tank at 70 lbs. pressure per square inch. It is not
necessary for the attendant to be closely over the tool during the
process. This arrangement has all the appearance of efficiently suppressing dust at the point of origin, and it is disquieting to find that
an atmospheric dust sample taken at breathing level of the man
operating the machine gave 1,144 particles in 1 c.c, all of which were
stone particles and many of very fine dimensions, with only 4.3 per cent.
over 2 f*. It appears that the dust, produced in a deep cut with great
pressure as in this machine, on a hard quartzite rock, cannot be
completely arrested by water alone, especially the fine particles. It
is probable that exhaust draught will be necessary in addition to the
water.
Another example comparing wet and dry turning of grindstones is
given in table IV (Brunton, Gosforth).
At another quarry at which grindstones are made, an exhaust

SILICOSIS

GREAT

TABLE

Occupation

Mason

District
and
stone

South Wales
(Forest of
Dean and
B a t h stone)
Leeds
(Yorks)

Age

Years

Some years

Mason

Stoke-onTrent

Mason

Hudders field
(Yorks)

Mason
Hudders field
(On plan- (Yorks)
ing machine)

Stone
planer
(Quarry)

Huddersfleld
(Yorks)

Mason

Chester,
Cefn,
Darley
Dale,
Brunskill,
(Yorkshire)
Stratford
(Flagstones
and p a t e n t
Victoria
stone for
station
platforms)
Bristol

Mason

Lancaster
(Lancaster
and Darley
Dale stones)

Mason

Darwen
(Lancashire)

Huddersfleld
(Yorks)

Birmingham
Hollington
stone
(Staffordshire)
London
(? stone)

Mason

Leeds
(Yorkshire)

?10
(before
1906;
afterwards
on limestone)
35

Mason

Harrogate
(Yorkshire)
Leeds
(Yorkshire)

Mason
(pavior,
railway)

Mason

Quarryman
stone
dresser
Mason

Mason's
labourer

Stone
crusherman

Period
Period
of
of
employsymptoms
ment

Years
41

405

BRITAIN

Period
of
incapacity

8 months

Cause•
of
death

Remarks

Tuberculosis
with
silicosis

Silicosis
Worked in open
plus
sheds.
tuberculosis
Silicosis
2
„
8
„
plus
tuberculosis
Open shed or open
Silicosis
18
„
2
„
plus
air.
tuberculosis
13
„
5 years
Silicosis
Left industry 10
years before death
owing to signs of
mason's disease.
No evidence of
tuberculosis postmortem.
None
Silicosis
Work in machine
—
plus
sheds.
tuberculosis
(haemoptysis)
Silicosis
Work
in
open.
5 years
1 month
plus
50 % of
stone
tuberculosis sandstone ; 50 %
(bronchoPortland stone.
pneumonia)
Some years 10 months Silicosis
Work mostly in
(bronchothe open.
pneumonia)
6 years

„

7 years

2 years

10 months 10 months
15
(from
age 14
to 21
and 36
to 44)
44
A few years 3
A fewweeks

1 week

Silicosis
with
tuberculosis
Silicosis
Silica formed 14%
plus tuberof total mineral
culosis (hae- m a t t e r and iron
oxide 9 % in the
moptysis)
lung. (D. S. Ashcroft, M.B.)
H e a r t failure
due to
silicosis
Silicosis
In open air and In
(bronchoopen sheds.
pneumonia)
Silicosis
plus tuberculosis

12 months

8 months

10 years
before
death

2 years

Fibrosis of
lungs. Silicosis (nontubereulous)

10 years

1 year

Silicosis
plus tuberculosis
Silicosis

6 months

—

6 months
9

Silicosis
plus tuberculosis

Silicosis diagnosed
by X-ray in 1906.
Probable exposure
to
silica
dust
berore then. History not obtainable.

406

PAPERS PRESENTED TO THE CONFERENCE

apparatus is used in which the dressing tool is carried by the pivoted
duct which is connected with a settling box by a flexible extension.
(2) The application of exhaust is illustrated by the apparatus
designed by Captain Hay, of the Safety in Mines Research Board,
for use with rock drills in mines, and adapted by him, in conjunction
with His Majesty's Office of Works, to hand pneumatic tools for dressing
stone '. The appliance for use in mines is already on the market.
That for stone-dressing is demonstrated by a special exhibit at the
Home Office Industrial Museum, London.
The method adopted to trap the dust is to fit, as near as possible
to the cutting point of the tool, a hood through which exhaust draught
is provided by an ejector provided with a jet, designed to operate
off the compressed air supply. The air containing the dust from the
working point is carried to a special filter bag, which, in the case of
mines is suspended in the working, but in sto ne-dressing would be
installed outside the workplace in an enclosed ventilated cabinet.
Experiments have been carried out with the dust trapping apparatus
in use and the results controlled by samples taken with Owens' dustcounter. The results show that the device provides a high degree of
protection. Samples taken with the device in operation gave counts
up to 150 particles in 1 c.c. of air, while samples taken with the exhaust
cut off gave counts of over 2,000 particles in 1 c.c. of air. A sample
taken at the ventilation opening of the collecting bag cabinet indicated
that only a small proportion of the finest particles of stone dust passed
through the filter bag and escaped to the outside air.
These two examples do not cover all the processes in quarrying
and dressing of sandstone, but they might form a basis for methods
of dust suppression from which modifications for the other processes
can be adapted.
Legislation in Force for Prevention
In processes in quarries where the stone contains not less than
80 per cent, of silica, a code of Special Rules made under the Quarries
Act, 1894, is applied by the Mines Department 2 . This code corresponds with the Regulations for Refractory Materials under the
Factory and Workshop Act, but in the case of quarries the Special
Rules are applied whether the material is to be used as refractory
material or not.
The chief provisions of the Special Rules are as follows :
1. Rock drilling by mechanical power to be provided by efficient
water jet or other efficient means to prevent escape of dust.
2. Stone to be broken by manual labour in the open air only,
and a wet canvas cloth to be used to prevent escape of dust, or suitable
respirators to be provided and renewed unless the work is carried on
so as not to expose the workers to the inhalation of dust.
1
2

Cf. Bibliography, No. (7).
Cf. Bibliography, No. (1).

SILICOSIS IN GREAT BRITAIN

407

3. Machines for crushing and grinding of stone (a) to be provided
with exhaust draught and dust collecting appliances, or with efficient
water or steam spray or other arrangement to prevent escape of dust;
or (b) to be entirely enclosed.
4. In sawing, planing and turning the stone to be kept wet.
5. Workmen dressing stone not to work nearer than 6 feet from
each other.
6. The dressing of stone not to be carried on in any closed shed
unless exemption is granted on the ground of exhaust ventilation
being provided.
Compensation
A scheme of compensation known as the Sandstone Industry
(Silicosis) Scheme, 1929, came into force on 1 April 1929 and
applies to all workmen employed in the sandstone industry, as
defined in the scheme. For the purposes of the scheme the industry
means all processes in or incidental to the getting or manipulation
of sandstone with a view to manufacture, sale, or use, which are
carried on at or within the close or curtilage of any mine or quarry
or at any premises worked in conjunction with a mine or quarry,
wherever situate.
For the purposes of the scheme, " sandstone " includes ganister,
gritstone and quartzite rocks, but does not include rotten stone
or natural sand.
The scheme does not apply to : (a) premises to which the Refractories Industries (Silicosis) Scheme, 1925, applies; (b) any premises
not being part of a mine or quarry, for the manufacture of silica
flour; (c) where sandstone is only occasionally worked and without
explosives or mechanical power; (d) certain employments carried on
apart from the processes; (e) certain processes in the manufacture
of artificial stone ; (/) any mine or quarry in which the stone worked
is proved, by chemical analysis, to contain not more than 50 per cent.
silica (free and combined).
This scheme is on the lines of the Refractories Industries (Silicosis)
Scheme, and by it special medical provisions have been made
whereby a specialist medical board carries out periodic medical
examinations and examinations for certificates of compensation
of all the persons to whom the scheme applies. The medical board
consists of whole-time medical men with their administrative
centre in Sheffield, which is a convenient centre for this and the
refractories industries, which shares with this scheme the services
of the same Medical Board. Subsidiary centres of the Board are
established at Bristol and Newcastle-on-Tyne.
The scheme provides for compensation in cases of partial and

408

PAPERS PRESENTED TO THE CONFERENCE

total disablement or death due to silicosis and silicosis with
tuberculosis.
Those workmen in the sandstone industry who are not employed
in or in connection with a mine or quarry are not included under
the Sandstone Industry (Silicosis) Scheme. For these workmen
provision is made under the Various Industries (Silicosis)
Scheme, 1928, which is on the lines of the Metal Grinding Industries
(Silicosis) Scheme, 1927, which provides for compensation in cases
only of total disablement or death.
Bibliography
(1) Special Rules. Quarries Act, 1894; Mines and Quarries Form No. 84:
Silica Quarries.
(2) Report on the Prevalence of Lung Disease amongst Workers at Grinshill
Quarries. By Dr. J. WHEATLEY, County Medical Officer for Shropshire. 1911.
(3) Report on the Prevalence of Phthisis among Quarry Workers and Miners.
By Dr. S. BARWISE, County Medical Officer for Derbyshire. 1913.
(4) Report on the Occurrence of Silicosis among Sandstone Workers. By
Dr. C. L. SUTHERLAND and Dr. S. BRYSON.

His Majesty's Stationery Office,

1929. Price Is. 6d.
(5) The Sandstone Industry (Silicosis) Scheme, 1929. Statutory Rules
and Orders, 1929, No. 171. His Majesty's Stationery Office.
(6) The Various Industries (Silicosis) Scheme, 1928. Statutory Rules and
Orders, 1928, No. 975. His Majesty's Stationery Office.
(7) "Modified Design of Hay Dust T r a p . " By Captain P. S. H A Y ,
A.M.I.E.E., A.M.I.Mech.E. Journal of Industrial Hygiene, Vol. XII, No. 1,
Jan. 1930.
GRANITE INDUSTRY

The granite quarrying and dressing industry may be regarded
as including all processes in getting the material from the quarry
and manipulation of the material with a view to manufacture,
sale, or use.
Granites and allied rocks of igneous origin are characterised by
a crystalline structure, more or less apparent, and a certain hardness
or toughness which demands special methods for quarrying them
and adapting them for use. From the point of view of the production
of silicosis it is important to distinguish the true granites, or acid
igneous rocks, from the intermediate and basic igneous rocks,
having regard to the proportion of free quartz in their composition.
Distribution
True granites are found in Cornwall and Devon, the Lake district
of England, and in several districts in the west and north of
Scotland. Other igneous rocks, resembling granite, are distributed

SILICOSIS IN GREAT BRITAIN

409

in many parts of England, Wales, and Scotland. The processes are
carried on for the most part at or near the district in which the rocks
are quarried.
Operations and Processes
The occupations in the granite industry may be classified, for
the present purpose, as follows: labourers, getters, drillers, settmakers, kerb-dressers, crushermen, building masons, monumental
operatives, polishers.
(1) Labourers are unskilled workers employed in removing overburden, loading and filling granite, and they may assist in blocking,
or getting, or drilling.
(2) " Getters " are skilled quarrymen who get the granite from the
quarry face, roughly square it into blocks of suitable size. The group
includes blockers and rockmen.
(3) Drillers include workmen employed in all forms of drills—hand
drills, steam drills, wet and dry air drills.
(4) Settmakers shape the setts or stone blocks for road material by
means of hand hammers. They work in a shelter or open shed.
(5) Kerb-dressers, sometimes referred to as masons, particularly in
Leicestershire.
(6) Crushermen include all workmen employed in crushing mills
and in concrete works. The group includes breakermen, screenmen,
oilers, labourers about the mill, and loaders.
(7) Building masons are skilled workmen engaged in cutting and
dressing granite in builders' yards. Some of these work only with
hand tools and others use pneumatic tools. The use of the pneumatic
tool varies considerably in different districts. In Cornwall it is used
to a comparatively slight extent. In Aberdeen the pneumatic tool
was found to be more in evidence among building masons. These
pneumatic tools may be for cutting or surfacing. Building masons
work in open sheds.
(8) Monumental operatives or monumental masons. This group
includes squarers, duntermen, finishers, and turners working in monumental yards. The squarer uses a hand chisel and a pneumatic cutter.
The dunterman is employed in operating the pneumatic dunter or
surfacing machine. The finishers use the pneumatic tool almost exclusively for their work. Turners work with a power driven lathe. The
squarers can work in a shed by themselves or in the same shed as
finishers. The duntermen work in widely open sheds in the yard.
Turners are, as a rule, in the same shed as the polishers.
(9) Polishers are employed in monumental yards. Polishing is a
wet process; it may be done by hand, but, as a rule, machinery is
used.
Characters of the Dust
The composition of the dust given off in the processes depends
on the character of the stone being worked. In the so-called true
granites there is a varying proportion of free silica in the form

410

PAPERS PRESENTED TO THE CONFERENCE

of quartz. In the other igneous rocks the proportion of quartz
varies to a considerable extent, and in some of the igneous rocks,
including some foreign stones, free quartz may be absent.
True granite consists of orthoclase felspar, quartz, and mica.
The chemical composition is distinctly acid, there being from
65 to 75 per cent, of silica. In intermediate rocks, for example the
syenites and diorites, the silica percentage varies from 60 to 55;
while in the basic rocks—dolorite and gabbro—the silica content
is from 45 to 55 per cent. The proportion of free silica as quartz
varies considerably in different specimens; for example, in some
of the Aberdeenshire granites: Rubislaw, 23 to 29 per cent.,
Sclattie, 27 per cent. ; Kemnay, 20 per cent. ; Peterhead 10 per cent.
In the city of Aberdeen, the centre of the monumental granite
trade, a large proportion of foreign stones are worked, amounting
to over 80 per cent, of the output. Many of these foreign stones are
not true granites and have a low quartz content. For example,
Emerald Pearl (Norway), 13 per cent.; Bonaccord Black and
Green (Sweden), no free quartz ; Balmoral Red (Sweden) 11 percent.
In others the quartz content is high; for example, " Glencoe ",
from Finland, contains 35 per cent, quartz.
With regard to {he conditions of work, there is a definite opinion
amongst men who have worked in America that the risk there is
greatly increased with the use of closed sheds, rendered necessary
by severe cold weather. Work is not done in this country under
quite the same conditions; this is especially true of work done
near quarries, whilst in Aberdeen, though sheds are covered in,
free ventilation is maintained.
The atmospheric dust produced at most of the processes in
granite quarrying and dressing was sampled with Owens' jet
dust-counter, at the place of work. Table VII gives particulars
of the results of the examination of these samples. The conditions
which favour the production of dust or its suppression are similar
to those which affect similar processes in the sandstone industry.
Speaking generally, however, there appears to be less tendency
for the dust from granite to rise to the breathing level of the worker.
Evidence of Silicosis being Produced
A Medical Enquiry was made for the Home Office, in conjunction
with the Mines Department, in 1929 by Drs. C. L. Sutherland,
S. Bryson, and N. Keating, members of the Medical Board under the
Refractories Industries and Sandstone Industry (Silicosis) Schemes,

SILICOSIS IN GREAT BRITAIN

411 •

TABLE VII
Origin
of
granite

Rubislaw,
Aberdeen

Process

Making
" crossing
setts "
Making setts

Position

Open shed

Weather

Fine, wind

Number
of
particles
In 1 c.c.

Percentage
over
2n

Remarks

566

Practically all particles are mineral.

To leeward

Strong
wind

1.7

Punching sett
Attending
crusher and
screens
do.

Shelter of shed
Open air

Windy
do.

138
951

10
11

do.

1,313

do.

Clearing
crusher jaws

On platform

do.

2,422

do.

Screening dust
from crusher
Making cross- Open shed
ing setts

do.

2,783

7.5

do.

204

3,145

do.

253

do.

2,325

do.

343

1.5

Larger number of
large particles.
Practically all particles are mineral.
Practically all particles are mineral.
Practically all particles mineral. Soot
negligible.
Scattered particles of
mineral only seen.
Scanty record. Not
counted.
Mineral
particles
nearly
all
fine,
chiefly in diffuse
splashes. No soot.
Very little soot.
Particles almost colourless.
Soot negligible.
Similar to above: but
more fine particles.
Many discrete tine
particles.
Soot
negligible.
Similar to above, but
more fine particles.
Particles sometimes
occur
in
loose
splashes.
Discrete
particles.
Many angular fragments. Soot negligible.
Some aggregates. No
soot.
Some aggregates
around larger particles.
Some soot,
nearly all in clumps.
Soot
from
crane
engine. About 70 %
soot; rest mineral,
all fine.
Soot negligible.

do.
do.
do.
Sciatile,
Bucksburn,
Aberdeen
do.

Persley,
Bucksburn,
Aberdeen
do.
Kemnay,
Aberdeen
do.

do.

Drilling side
hole in block
Drilling
vertical hole
Air-drilling

do.

Making steps

Balmeddle,
Aberdeen
do.

Feeding
crusher jaws
Attending
below
elevators

do.

Wet drilling
at face

Blackhill,
Longhaven,
Aberdeen
Guite,
Longhaven,
Aberdeen

Between 2
men drilling
granite
Between 2
men hand
drilling
granite
Dry drilling

do.
do.

do.

469

Open air

do.

4,796

do.

Quarry
bottom

Hand-drilling

Kemnay,
Aberdeen

Bonawe,
Taynuilt,
Argyll
do.

In shelter

Axing a
nidged sett
Dry drilling
for pop holes
Wet drilling
same hole

Using sett
hammer
Feeding
crusher jaws

Dry

434

3,337

3.6

do.

Open shed

—

Windy

Top of quarry Some wind,
dry

—

do.

Similar to above.

—

Slight wind,
sunny

180

Soot negligible.

—
—

do.

674

Soot negligible.

do.

2,434

No soot.

do.

259

Considerably larger
number
coloured
particles than above
and fewer larger
particles.
No evidence of clumping.
Some splashes. Soot
not included.
Some aggregates.
Many particles from
5 |i to 8 v.. Soot not
Included.

~~*
Crusherhouse

do.

Slight wind,
bright

951

412

PAPERS PRESENTED TO THE CONFERENCE
TABLE vu

Origin
of
granite

Process

Bonawe,
Working
Taynuilt,
below screens
Argyll
Craignair,
By t h e screens
Dalbeattie,
Kirkcudbright
Feeding gyrado.
tory crusher
do.
Filling 3/8th
inch crushed
granite from
shoots
Cove B a y ,
Dry
drilling
Kincardine
vertical hole
Dry drilling
do.
breast hole
On platform
do.
looking over
plant
Eskdale,
H a n d drilling
Cumberland
for p o p hole
Waberthwaite, Rock drilling
with wet triCumberland
pod air drill

do.
Embleton,
Cumberland
do.
do.

Threlkeld,
Cumberland
do.
Snap Fell,
Westmorland

do.

Dressing sett

Position

Crusherhouse

(continued)

Weather

Slight wind,
dry

N u m b e r Percentof
age
particles
over
in l c.c.
2 i*
2,325

614

Small crusherhouse

—

Shed open one
side
Large crusherhouse

Windy

2,325

Damp,
windy

—

—
—

1,506

1,144

915

Dry

602

— •

265

205

2,265

Crusher-house

—
—

Open shed

Shovelling
Crusher-house
crushed stone
into elevator
1-man shed
Settmaking
open one side
Dry drilling

Dry
do.

675

do.

1,349

3.5

Filling
tubs
—
from hoppers
at granulator
and screens.
Feeding stone
—
crusher
Making setts
Open shed

do.

2,024

do.

976

do.

626

Dry

Mouth of open
shed

do.

7,447

6.8

drilling

do.

Quarry face

do.

6,675

6.0

do.

Crushing

Crusher feed

do.

3,157

Mount Sorrel,
Leicester
do.

Air drilling on
block
Screening
while machine starting
to r u n

do.

Stone passing
in screens

Open air
I n screening
house, provided with
exhaust
draught
do.

Windy

482

168

229

Remarks

Many particles over 5
!<• u p to 15 V-. No soot.

Many large aggregates. Soot negligible.
Record sparse and
ill-defined.
Not
counted.
Very few aggregates.
Soot negligible.
Similar to above.
Large
number of
particles, m a n y
rounded.
A few aggregates.
No soot.
Mineral particles
nearly all in small
aggregates, studded
over with soot particles.
Nearly all
discrete
particles
are soot, clumped
in p a r t s .
Some small aggregates.
Very little
soot.
Some close aggregates. No soot.
No soot.
Majority of particles
very line.
Very
little
aggregation.
Soot
practically
negligible.
Many
large
close
clumps a n d masses.
Soot almost absent.
Considerable n u m b e r
of clumps.
Many line particles
adherent to larger
particles; others in
splashes. Soot negligible.
Many fine discrete
particles and a few
clumps. Soot negligible.
Resembled above in
general characters.
Some clumps of mineral particles and
some splashes. Soot
clumped.
Particles mostly
discrete. No soot.
Larger mineral p a r t icles
in
clumps.
Some soot.
Considerable a m o u n t
of soot.

413

SILICOSIS IN GREAT BRITAIN

TABLE
Origin
of
granite

Process

vu (continued)

Position

Mount Sorrel,
Leicester

Screening

do.

Crushing

Under h a t c h
cover in housing
while
stone was
passing
Crusher-house

do.

Settmaking

I n shed

At tarring
plant
Operating
shoot hopper

Rail track in
t h e open
Tar mixing
plant

Groby,
Leicester
do.

At mixing
cylinder
Feeding
cracker jaws
Dalbeattie,
Feeding
Kirkcudbright gyratory
crusher
Eskdale,
Feeding
Cumberland
cracker jaw
Wabertbwaite, Crushing
Cumberland
plant
do.

do.

Weather

Number
of
particles
in 1 c.c.

Percentage
over
2 n

409

do.

3,120

do.

4,555

2,699

933

747

do.

5,157

do.

2,524

—
In covered
shed
Open shed
do.

On staging
where aerial
ropeway
delivers
buckets
No work being Artificial flag
do.
done
shed
Craignair,
At little
Open air
Dalbeattie,
dunter
except
for
Kirkcudbright
head cover
Turning a
Turning shed,
do.
pillar on
door open
machine
Craignair,
Rough dress- Open shed
Dalbeattie,
ing granite
with
Kirkcudbright stone
punch
Putting bed
,
Creetown,
on stone with
Kirkcudbright
chisel
Putting botdo.
tom bed on
headstone
with pneumatic chisel
Using pneu- Closed shed
do.
matic surfacing ool
Dressing top
do.
do.
head of stone
with punch
Lettering
Carving shop
do.
headstone
with chisel

Record too dense to
count.
Particles
overlapping.

2,362
Windy

—

•

Windy

Remarks

A considerable n u m ber of very fine
particles.
Some very fine p a r t icles in groups. Soot
negligible.
Many large masses
and aggregates
Many large masses
and aggregates of
stone particles.
Some soot in fine
particles.
Much
dust
in
masses.
Particles nearly all
discrete.
Many
very
fine
particles.
Some
aggregates. No soot.
10% of particles soot;
others mineral.
Many
very
fine
particles, some in
splashes. No soot.
Control for
above
sample.
No soot.

do.

Windy

120

do.

Windy

855

do.

1,337

6.3

do.

130

About 50% of particles stone dust.
Some aggregates.
Soot negligible.

2,470

Soot negligible

397

Soot negligible.

265

Soot negligible.

•*"~

A few aggregates of
fine particles. Some
soot clumped — not
counted.
Soot absent.

414

PAPERS PRESENTED TO THE

CONFERENCE

the report of which is in course of preparation. The investigation
was carried out on the lines of that for the sandstone industry and
included the clinical examination of 494 workers, of whom 211 were
examined radiologically. The results of the radiological examinations are given in the following table:
TABLE VIII
Occupation

Number
examined

Number
X-rayed

Labourers
Getters
Drillers
Settmakers
Kerb-dressers
Crushermen
Building masons
Monumental masons
Polishers

1
52
66
88
30
105
85
54
7

2
17
25
41
13
36
45
29
3

Totals

494

211

Silicosis
found on X-ray

1
1
1
8
16
9
36

In the cases of silicosis, the stage reached, as shown by X-ray
examination, together with the district in which the workers were
examined, are shown in table IX.
TABLE IX
Occupation

Area

Number
positive

Stage of silicosis

Getter or blocker
Settmaker
Crushermen

Leicestershire
Cumberland
Cumberland
Leicestershire
N o r t h Wales

1
1
2
3
3

Ib.
la,
la, Ib.
la, la, He.
l a , la, l i b .

Masons

Cornwall

la, la, la, la,
l a , la, l a , Ib.

Building masons

Aberdeen

l a , l a , l a , la,
la, la, IIa, IIa.

Monumental masons

Aberdeen

la, la, la, la,
l a , I b , le, H a ,
Ile.

Driller

Cornwall

IIb.

JVoíe. — The getter or blocker had worked most of his time as a settmaker. The driller
had worked much longer in tin mines than in granite. Therefore no cases among blockers
and drillers really.

415

SILICOSIS IN GREAT BRITAIN

TABLE X.

PARTICULARS OF CASES OF GRANITE WORKERS,

DIAGNOSED

AS SHOWING SIGNS OF SILICOSIS BY RADIOLOGICAL EXAMINATION,
WITH A NOTE ON THE CHARACTERS OF THE

District and stone

Age

1. Leicestershire
(Syenite.
Total silica
= 66.48 %)
2.
do.

Crusherman

Crusherman oiler

Crusherman
(Foreman for
24 years)
Settmaker
Getter and
Blocker

Crusherman
Coal mine
5 years, of which
2 were on cutting
hard ground
Crusherman
Screens

3. Leicestershire
(Total silica
= 67.16 %)
4.
do.

Occupation

Period
of
employment
Years
27

Symptoms

Stage
of
silicosis

Remarks

Slight cough
and s p u t u m

la.

Finely granular
disseminated fibrosis.

Ic.

Very finely granular
disseminated fibrosis.
Nodules present.

—
Dyspnoea

—

la.

Slight cough
and s p u t u m

IIb.

la.

5. North Wales
(Total silica
= 58.06 %)

do.

Crusherman

Dyspnoea,
cough and
sputum
Slight dyspnoea cough
and sputum

8. Cumberland
(Total silica
= 67.18 %)

Crusherman

—

Crusherman
Quarryman

20 1
19/

10. Cumberland
(Diorite, total
silica =
75.22 %)
11. Aberdeen
(local, home
and
foreign
granites)
12.
do.

Settmaker
Blocking

411
20/

Very slight
cough

191

Pain in the
chest and
dyspnoea

13.

do.

Monumental operative
Dunterman squaring and finishing
Monumental operative (4 years on
Blue Pennant,
South Wales;
3 months on
Derbyshire grit)
Monumental operative (6 years in
United States)

14.

do.

15.

do.

Granite mason
(Home gTanites)
(2 years in
United States)
Monumental
Building
(2 years in
United States)
(Mostly home
granites)

lie.

221

i o /\

la.

lb.
la.

He.

9j
32

SHADOWS

la.

Some
dyspnoea

Slight dyspnoea and
sputum

la.

3!}

Dyspnoea on
exertion

la.

Ha.

Very slight nodulation
in the upper and
middle zones.
At
bases
only
fine
striation.
R a t h e r dense
fine
shadows middle
zones. Apices r a t h e r
clear.
Fine diffuse shadows,
except left middle
zone, which is clear.
No definite localising
signs.
Increased
mottling
w i t h very slight,
rather fine nodulation.
Middle zone on t h e
right, slight faint
mottling. Less on
t h e left.
Slight increased
mottling, very slight
nodulation.
Marked deep irregular
shadows in all areas,
with clear spaces
between.
Marbling and m o t t ling. Not very definite nodules.

Increased root shadows.
Slight fine
mottling and nodulation left
middle
zone.
Diffuse fine nodulation and much fine
mottling.
R a t h e r dense thickening. Slight nodulation.

416

PAPERS PRESENTED TO THE CONFERENCE

TABLE x

District and stone

Age

16. Arberdeen
(local, home
and foreign
granites)

17.

do.

18.

do.

19. Aberdeen
(Local, home
and
foreign
granites)

20.

do.

21.

do.

Occupation

Stone cutter
Fixer
(including pneumatic tool; 20
years in closed
sheds). 20 years
on home granite
Monumental
operative
Monumental
operative
(24 years on
pneumatic tools,
10 years in
United States)
Monumental
operative
(Pneumatic tool
2 days a week
last . 15 years.
One
year
in
United States)
Monumental
operative
Building 5 years
Monumental
operative
Squarer
Finishing
Stone dresser,
(7 years in South
Africa on granite)

(continued)

Period
of
employment

Stage
of
silicosis

Remarks

Years
24 1
6/

IIa.

Definite
nodulation
over both lungs.

la.

34 '

Some
dyspnoea

Ic.

Increase fine striation and reticulation.
No definite nodules.
Considerable amount
of fine nodulation
in middle zone a n d
right base especially.

Some
dyspnoea
4 years

la.

F i n e mottling and
increased shadows.

Slight cough
occasionally

lb.

Mottling with fine
nodules.

35 1
6/

Tightness of
chest 2 to 3
years. Slight
cough
Dyspnoea on
exertion.
Slight cough

la.

F i n e mottling and
nodules, right upper.
Much increase of
striation.
Much fine mottling
with fine nodules,
diffuse over both
lungs.
Much fine mottling
and nodules over
outer zones.
Much mottling and
diffuse fine nodules.
especially in the
outer zones.
Definite nodulation in
both lungs.

22.

do.

23.

do.

Building mason

24.

do.

Building mason

25.

do.

26.

do.

27.

do.

Building mason
(South Africa
6 years,
United States
1 year)
Building mason
(United States
2 years,
South Africa
12 years,
of which 5 on
sandstone)
Pneumatic dunter
Stone cutter
Granite mason
Granite mason
(United States
2 years)
Mason
(2 years on Blue
( P e n n a n t sandstone)
Granite mason
(Last 25 years on
d u n t e r . United
States 22 years
on dunter)

28. Cornwall
(Total silica
= 72.05 %)
29.
do.

50
52

32.

do.

31.

do.

Symptoms

la.

la.
Dyspnoea,
increased
over t h e last
10 years
Dyspnoea
1 year.
Sputum in
the morning

la.

Ha.

Dyspnoea
on exertion
2 years

la.

Very little nodulation.
Increased striation.

30 1
18/
30

Dyspnoea
3 years
Slight
dyspnoea

Ic.
lb.

Dyspnoea
6 years

la.

Much fibrosis with
fine nodules.
R a t h e r dense woolly
shadows. Nodulation
at parts.
Increased fine striation and slight fine
nodulation.
Increased fine striae.
No definite nodules.

la.

R a t h e r dense diffuse
fine nodular shadows,
all areas.

417

SILICOSIS IN GREAT BRITAIN

TABLE

District and stone

Age

x (continued)

Occupation

Period
of
employment

Symptoms

Stage
of
silicosis

Remarks

la.

Nodulation on finely
woolly base in upper
zones only.

Years
30. Cornwall
(Total silica
i : = 72.05 %)

33.

do.

34.

do.

35.

do.

Air driller 5 years.
Worked in granite
Tin miner on top
Tin miner underground
(including 5 years
with jack h a m mer)
Mason
(3 years in United
States. 8 years
on Blue P e n n a n t
sandstone)
Mason
(5 years in South
Africa, all on
granite)
Mason

36.

do.

Granite mason

9
3y¡i

18 f

Dyspnoea
8 years

la.

Increased
striation
with fine mottling
and very fine nodules

Dyspnoea
on exertion

la.

Increased
striation
with fine nodules.

Tightness of
the chest on
exertion

la.

Dyspnoea on
exertion for
6
months.
Slight cough

la.

Increased
striation,
very fine nodules,
especially the middle
zone.
Increased hilus s h a d ows, mottling and
fine nodules on the
outer middle zone
and right base.

Examination of the radiograms in the positive cases classed as
silicosis shows that the prevalent type of the shadows indicating
fibrotic changes is somewhat different from that found in workers
exposed to silica dust in other industries. In the radiograms of
granite workers there are usually the increased hilus, linear and
reticular shadows, but' instead of the discrete, dense nodules found
to a greater or less extent over the whole of both lungs, there is a
diffuse, cloudy or woolly effect with more or less definite fine or very
fine nodules occurring in areas irregularly placed over the lungs.
In the whole series the radiogram showing the most discrete
nodules of the silicotic type is in the case of a man who worked for
nine years as a driller on granite, but had been employed for
eighteen years as a tin miner underground. Amongst the other
cases, who had been almost exclusively employed on granite,
there appears to be some relationship between the composition
of the rock and the character of the fibrosis, as shown on the radiogram. The difficulty of obtaining accurate histories of workers
employed exclusively on any particular rock in this country makes
it impossible to draw substantial inferences on this point, but it
might be kept in mind for future investigation into the effects
of dusts such as silicates.
27

418

PAPERS PRESENTED TO THE CONFERENCE

Table X gives some particulars of employment of the workers
in granite, diagnosed as cases of silicosis by the writers of the
Medical Report referred to, and notes by the present writer on the
radiograms examined independently.
Clinical evidence of fibrosis, as distinguished from radiological
evidence of silicosis, was found in 260 cases, or 52.6 per cent, of
the 494 workmen examined.
The distribution in districts and occupations is shown in table XI.
Comparing the results of the medical examinations in the
sandstone industry and the granite industry, the proportion of
cases of fibrosis amongst sandstone workers was 59 per cent, of
those examined, compared with 52.6 per cent, in the case of granite
workers. The cases of silicosis in sandstone workers was 42 per cent.
of those radiologically examined, and 17 per cent, in the case of
the granite workers.
If fibrosis of the lungs, diagnosed by clinical examination, be
regarded as representing a slighter or earlier involvement of the
same character as silicosis, then it would seem that granites and the
igneous rocks of granite type produce less injury to the lungs than
do the sandstone. Having regard to the appearances of the radiograms in the two series of workers, there is a probability of a
difference in character of the types of fibrosis produced by the two
kinds of dust, and this probability is increased by the proportion
of cases of fibrosis in the granite series showing an approximation
to that found in the sandstone series, while the proportion of
silicosis cases remains far behind.
Methods of Prevention
The processes in the granite industry are similar to those
in the sandstone industry, and the principles of dust suppression
in the one case can usually be applied in the other. In the granites
and allied rocks generally, the rock is harder or tougher than in
the sandstones, and in the processes of quarrying, more drilling
has to be done. In cutting and surfacing pneumatic tools are more
often used on granites. The dunter or surfacing machine gives rise
to much dust and it is difficult to apply exhaust draught owing
to the wide movements of the tool and the vibration produced.
Drilling could be dealt with by the application of water spray or
hollow drill feed, or by the Hay type of exhaust apparatus. Cutting
and turning will require specially adapted exhaust which could
be provided on the lines suggested under Sandstone.

419

SILICOSIS IN GREAT BRITAIN

There are no special regulations in force in factories or workshops
in connection with granite working, but the general provisions
of the Factory and Workshop Act, 1901, apply.
TABLE XI.

CASES DIAGNOSED CLINICALLY AS FIBROSIS

OF THE LUNGS, AND RADIOLOGICALLY AS SILICOSIS, WITH THE
DISTRICTS AND OCCUPATIONS
(The proportion of cases of fibrosis are stated as a percentage of the workers
examined.
The proportion of cases of silicosis are stated as a
percentage of the workers
radiographed.)

District

Leicestershire

Cumberland

Cornwall

N o r t h Wales

Aberdeenshire

Occupation

Labourers
Getters
Drillers
Settmakers
Kerbdressers
Crushermen

Number
examined
2
22
14
26
30
67
161

Fibrosis

10
3
15
13
22
63 (39.1%)

Number
radiographed

9
7
9
13
12
50

3
4 (8%)

4
11
9
13
14
51

4
4
8
8
24 (47%)

Labourers
Getters
Drillers
Masons

1
8
9
34
52

3
3
22
28 (53.8%)

Getters
Drillers
Settmakers
Crushermen

11
10
18
11
50

5
9
12
10
36 (72%)

24
31
13

9
21
6

6
16
9

29
3
85
211

Labourers
Getters
Drillers
Settmakers
Crushermen

Drillers
Settmakers
Crushermen
Building
masons
Monumental
masons
Polishers
Totals

54
7
180
494

41
4
109 (60.5%)
260 (52.6%)

1
4
5
10
6

Silicosis

1
2
3 (11.5%)

1
2
4
23
30

1
8
9 (30%)

2
3
6
9

3
3 (15%)

17 (20%)
36 (17%)

420

PAPERS PRESENTED TO THE

CONFERENCE

Compensation
The granite industries are not at present included in any scheme
of compensation for silicosis.
Bibliography
(1) The Problem of Dust Phthisis in the Granite Stone Industry. By F. L.
HOFFMAN, LL.D. United States Department of Labour, Bulletin No. 293.
Washington, Government Printing Office, May 1922.
(2) Report on the Occurrence of Silicosis among Granite Workers.
By
Drs. C. L. SUTHERLAND, S. BRYSON and N. KEATING.

SLATE

QUARRYING

AND

DRESSING

1930.

INDUSTRY

The industry is concerned with the quarrying of the rock and
making into slates for roofing, structural, blackboard, sanitary
and electrical uses.
Distribution geographically and the numbers of persons employed
are given in the following table of wage earners employed in slate
mines and quarries in 1928:
TABLE XII

Division
1.

County
Aberdeen
Argyll
Banff
Caithness
Dumbarton
Perth

Cumberland
Westmorland

Lancashire
Isle of Man
Carnarvon
Denbigh
Merioneth
Montgomery

Cardigan

Carmarthen
Pembroke

Cornwall
Devon
Somerset

Number employed
10
300
9
2
9
31

361

11} ««
332
24
6,161
223
2,972
39

9,751

3} «
473]
530
52
10,907

421

SILICOSIS IN GREAT BRITAIN

Operations and Processes
In the open quarries of North Wales the slate is got by means
of blasting and wedging. Suitable sizes of slate so obtained are
conveyed to the mills. Overburden consisting of inferior slate,
igneous rock and soil has to be removed as the quarry extends.
In the mills the large blocks are sawn to required sizes, by
power-driven circular saws cutting across the grain. The smaller
blocks are then split by means of a broad flexible chisel and a
mallet, and cut to rectangular form either by hand or by the
revolving blades of a machine.
In some small quarries there are no mills and the splitting is
carried out in the open. The occupations may be divided into
(a) rockmen who work at the mine or quarry; (b) labourers who
assist rockmen in the quarry and remove overburden; (c) drillers
who use pneumatic drills ; (d) millmen who are employed in sawing,
splitting and dressing; (e) saw sharpeners, mechanics, etc.
The distribution of persons in the different occupations can be
seen from the following figures taken from two large slate quarries
in North Wales :
TABLE XIII

Quarry A

Quarry B

Rockmen, that is, getters, all of whom can do
drilling

Quarrymen, that is, slate makers, including
sawers, splitters and dressers

234

271

Labourers, including trammers, rubbishmen,
etc.

129

Day men, including slate loaders, tradesmen
and ropeway men

510

561

Special Characters of the Dust
Slate is the typical cleaved rock. The most important constituents
quantitatively are silica, free as quartz and combined as silicates,
alumina, iron, alkalis and other bases. Silica as quartz exists
in Penrhyn (Welsh) slates to the extent of from 34.66 per cent.

422

PAPERS PRESENTED TO THE CONFERENCE

to 43.26 per cent., while total silica (free and combined) is from
57.75 per cent, to 63.01 per cent. x
A series of dust counts taken with Owens' jet dust-counter
at slate quarries in North Wales in 1926, gave the following results:
At the Quarry :
(1) At breathing level of a driller dry drilling with pneumatic drill,
674 particles in 1 c.c, 8 % over 2 jx.
Many very fine particles in the sample.
(2) At breathing level of a driller on quarry-top dry drilling a vertical
hole in slate with Ingersoll pneumatic drill, %". Wind blowing the
dust away. Slight rain.
566 particles in 1 c.c, 10 % over 2 ¡J..
(3) Dry drilling as in (2). Sample taken 3 yards to leeward of the drill hole,
361 particles in 1 c.c, 7 % over 2 ¡J..
(4) Dry drilling at breathing level of a breast (horizontal) hole, about 18"
above ground, in slate quarry-top,
650 particles in 1 c.c, 25 % over 2 u.
Many large aggregates account for the high proportion of larger particles.
In the Mills:
Quarry A.
(1) At breathing level of a man at the saw table in slate dressing shed,
1,036 particles in 1 c.c, 17 % over 2 p.
There are many aggregates, varying in size from 2 ¡J. to 10 ¡J., and
consisting of a very few to several score of particles, most of which
are between 1 u. and 2 p. in size. The great majority of the particles
are irregularly rounded. Some are plaque-like, and a very few are
angular. Most are almost colourless and there is a fairly regular
sprinkling of deep red or black or dark green particles ; the coloured
particles being nearly always in aggregates. An aggregate is counted
as one particle, so that the presence of these reduces the count.
(2) Near the middle of the same shed,
2,361 particles in 1 c.c, 11 % over 2 ¡i.
The general characters of the particles are like those of No. 1, but there
are larger aggregates and a higher proportion of fine particles.
(3) In a slate dressing cubicle off the large shed. At breathing level
between two men, one splitting and one dressing with a hand knife,
855 particles in 1 c.c, 15 % over 2 ¡J..
The general characters are similar to those of (1) and (2).
(4) In another cubicle off the same shed, four men working, two splitting
and two dressing with hand knives,
241 particles in 1 c.c, 23 % over 2 ¡J..
A higher proportion of large particles and aggregates than in (3).
Quarry B.
(1) Near the centre of the dressing shed (in this shed splitters and dressers
work in a large room and not in cubicles as at Quarry A).
1,494 particles in 1 c.c, 8 % over 2 ¡J..
(2) Near the same point as (1), at breathing level of splitter,
3,325 particles in 1 c.c, 6 % over 2 ¡J..
There is a very large proportion of extremely fine particles and aggregates
of large numbers of these fine particles.
(3) In the same dressing shed, at breathing level of a dresser working at a
revolving slate dressing machine,
927 particles in 1 c.c, 9 % over 2 f¿.
Fairly large aggregates of many fine particles, reducing the count.
1

Cf. Bibliography, No. (1).

SILICOSIS IN GREAT BRITAIN

423

The general appearance of the microscope samples obtained
at these processes conveys the impression that slate dust tends
to form aggregates readily.
Evidence of Silicosis being Produced
In 1926 Dr. T. W. Wade, of the Welsh Board of Health, made
an investigation into an alleged high mortality rate from tuberculosis amongst slate workers in a district of North Wales. Dr. Wade's
observations and conclusions are contained in pages 28 and 29
of his Report 1 . He says:
The mortality tables of the Gwyrfai Rural District exhibit over a
long series of years a very high death-rate from tuberculosis of the
respiratory system, which is considerably higher for males than for
females. The mortality figures from this disease, both for males and
females, show high death-rates during the young adult periods of life.
The maximum mortality rate for males is, however, reached during
the old-age period of life, and this high mortality at the later age
chiefly determines the difference between the male and female deathrates from tuberculosis. It is probably true that the high death-rates
from tuberculosis of the respiratory system among young adults of
both sexes are produced by the same influences. The great majority
of the women are engaged in domestic duties in their homes, wherein
the men spend a part of their daily life. It is reasonable to assume
that the differences between the male and female mortality rates at
the later stages of life are in large measure the result of influences
outside the home. . . .
The mortality tables in the Report show t h a t in the earlier
periods of working life " other males " are less favourably
placed than " workers in the slate industry ", but that from
thirty-five years of age onwards, and particularly in the later
ages of life those engaged in the slate industry are very unfavourably
placed.
The standardised mortality of males aged sixty to sixty-five,
in certain occupations, given by the Registrar-General in the
Decennial Supplement for 1921 2 shows that the comparative
mortality figures for slate miners and quarriers compared with
1,000 for all occupied and retired civilian males, were, for respiratory
tuberculosis 1,594; diseases of the respiratory system 703; bronchitis 520; pneumonia 451; the comparative mortality figure for
all causes being 944, as compared with 1,000 for all occupied and
1
a

Cf. Bibliography, No. (2).
Cf. Bibliography, No. (3).

424

PAPERS PRESENTED TO THE

CONFERENCE

retired civilian males. Contrasted with these low figures for respiratory disease other than tuberculosis is the high rate for valvular
disease of the heart, which is 1,647 amongst slate miners and
quarriers, compared with 1,000 for all occupied and retired males.
While the local mortality rates and the occupational mortality
rates point to a high mortality rate from pulmonary tuberculosis,
there is little evidence t h a t respiratory disease independent of
tuberculosis is excessive.
On the evidence I think there is little doubt that the workers in
slate sheds are subjected to an injurious dust . . . The late age
at which the mortality curve for tuberculosis of the respiratory system
reaches its maximum may be due to the fact that the amount of dust
in slate sheds is not very great and also that slate dust when moistened
makes up into a clayey material which makes expulsion from the
respiratory passages more assured than otherwise.
A Medical Enquiry was undertaken by the Mines Department
in 1928. I t was carried out by Drs. Sutherland and Bryson, who
issued a Report in the form of a Memorandum to the Health Advisory
Committee of the Mines Department. The investigation was made
in North Wales in the district which was the subject of Dr. Wade's
enquiry. Clinical examinations were made of 120 workers and from
amongst these 61 were selected for radiological examination.
The results of examination in the various occupational groups
were as follows :
Rockmen. — Fifteen rockmen were examined clinically and 6 radiologically. No case of silicosis was found. The average age of the group
was 52.5. The average number of years spent as rockmen was 18.6,
but the average time spent in the industry of this group was 30.8 years.
Drillers. — Six drillers were examined clinically and 3 were X-rayed An average of only 3 years had been spent in drilling. No silicosis
was revealed.
Millmen form the largest occupational group. The total number
examined clinically was 96 and radiologically 52. Of those X-rayed
14 were found to be suffering from silicosis. The average age for this
group was 46.37 years, and the ages ranged from 19 to 71 years. The
average period in the occupation as millmen corresponds very closely
to the average time spent in the industry. A number of the millmen
had worked in coal mines for a few years and of these 7 had been
employed in hard heading work. None of these was included among
those X-rayed.
Clinical examinations show that severe fibrosis exists amongst
the older millmen. Fibrosis is also present in the older rockmen,
but to a less extent. In the drillers there is evidence of fibrosis
of a slight degree, but in the remaining two occupations no
evidence was found.

SILICOSIS IN GREAT BRITAIN

425

The 14 cases of silicosis found among the millmen could be placed
as follow: 12 in the first stage, one in the second, and one in the third.
The earliest age at which silicosis was found was 40 years. Most of
the cases, however, occurred in the 50-59 years age-group. The earliest
period of occupation group to show fibrosis was 20-29 years, but the
majority of cases occurred in the 40-49 years group.
Tuberculosis, apart from silicosis, was diagnosed in three instances
—one rockman and two millmen. The radiograph in these cases
showed no definite indication that silicosis was present. The case of
silicosis in stage 3 was also probably accompanied by tuberculosis.
Three of these cases were in the age-group 60-69 and one in the
40-49 years group. The number of years employed in the slate industry
in the 4 cases was 26, 42, 47 and 53 years respectively.
In four of the cases no symptoms were complained of. In 6 cases
the sole complaint was shortness of breath; a further 2 had cough
and dyspnoea and the remaining 2 complained of cough, spit and
dyspnoea.
Dyspnoea was therefore the most common symptom.
Pain was not complained of in any of the cases.
In view of the ages reached by many of the workmen while still
remaining fit for work, it may be assumed that there is no general
disability occurring amongst these workmen from exposure to dust in
their occupations. The rockmen show lower age periods, but their
work is rendered arduous by reason not only of the heavy character
of the work itself, but also by the climbing from the deep quarries
which their work involves. This would not be possible with a severe
degree of respiratory disease. It is possible that a considerable degree
of vocational selection is present and this is borne out by the standard
of physique, which the Report shows to be much higher in rockmen
than in millmen. Amongst rockmen no men were examined over
30-39 years' employment, but it is in this period that most of the
cases of silicosis are found amongst millmen, namely, 9 cases out of 14;
so that, although there appears to be less exposure to dust in the
work of rockmen than in that of millmen, there is not sufficient
evidence to make it possible to say that cases of silicosis would not
occur amongst rockmen if later employment periods were reached.
The presence of tuberculosis, fibrosis, and silicosis has been established. Is it possible to establish also a relationship between them ?
The Report shows that fibrosis and silicosis occur in this industry
and since extraneous sources of dust have been, to a great extent,
excluded by the selection of cases for examination, it may be assumed
that this change in the lungs is due to the inhalation of slate dust.
The view is generally accepted that fibrotic changes due to the inhalation of silica dust react unfavourably towards tuberculosis, and the
same may be true of slate dust which contains free as well as combined
silica.
It seems extremely probable that the cases of pulmonary tuberculosis occurring for the most part at advanced ages, in subjects who
have been exposed to the inhalation of dust and developed fibrosis,
are of a very chronic character. The period of infectivity extends
over many years and since the presence of the disease is not suspected,
precautions against the spread of infection are not taken. The opportunities for the spreading of the disease are considerable in the case
of millmen in slate factories, and the control of the excessive incidence
of tuberculosis amongst these workers appears to depend upon the
removal of sources of infection.

426

PAPERS PRESENTED TO THE CONFERENCE
Bibliography

(1)

MELLARD

READE,

F.G.S.,

and

PHILIP

HOLLAND,

F . I . C . , in t h e

Proceedings of the Liverpool Geological Society, 1898, Vol. V I I I , p a r t 2, p . 293.
(2) Report on the Investigation
into the alleged High Mortality Rate from
Tuberculosis of the Respiratory
System among Slate Quarrymen and Slate
Workers in the Gwyrfai Rural District.
B y Dr. T. W . W A D E . R e p o r t s on
Public H e a l t h a n d Medical Subjects, N o . 38. Ministry of H e a l t h , Welsh
Board of Health. His Majesty's S t a t i o n e r y Office, 1927. Price I s .
(3) Registrar-General's
Decennial Supplement, 1921. P a r t I I : " O c c u p a tional M o r t a l i t y " . His Majesty's Stationery Office, 1927. Price 7s. 6d.

COAL MINING

The distribution of the coal-mining industry in Great Britain
is indicated in the following table of employed persons.
TABLE XIV.
EACH

NUMBER OF WAGE EARNERS ON COLLIERY BOOKS IN
OF THE MINING

INDUSTRY

GREAT

ON 8 FEBRUARY 1 9 3 0

BRITAIN

ACT DISTRICTS OF

Division

County

Fife and Clackmannan
The Lothians
Lanarkshire
Ayrshire
Durham
Northumberland
Cumberland
1
Westmorland J
Yorkshire, South
West
North Derby
Nottingham
Leicester
South Derby
Lancashire and Cheshire
North Staffordshire
North Wales
South Wales and Monmouth
Part above and Forest of
Dean
Cannock Chase
" Warwick
South Staffordshire and Worcester
Kent
Somerset
Shropshire
Bristol

3.
4.

5.
6.
7.
8.

Tota in Great Britain

Numbers employed
23,847 1

Ufa "'.MS
12,815
142,108
49,333
10,090

J
1
1 2/ 0U .1 ,aqd.l
f
'

118,082 1
53,279 J
52,239 ]

l;l

>dbl

11^072 [ 1 1 8 > 3 8 0
3^792 J
76,334 1
28,800 \ 120,101
14,967 J
180,856 ]
[ 186,362
5,506 J
23,342 1
17,061
4,932
4,694
3,895
2,786
1,011
957,274

57,721

SILICOSIS IN GREAT BRITAIN

427

The processes underground in a coal mine, which may involve
exposure to silica dust are:
(1) Ripping: taking down the roof or top of roadway, to make
height ;
(2) Brushing: ripping or blasting of the roof and the using of
debris for building stone packs;
(3) Driving a hard-heading: a drift, tunnel or roadway driven in
rock or through hard measures;
(4) Driving a cross measure drift: driving a roadway in such a
direction as is necessary to form a travelling road from stratum
to stratum.
The drills used are mostly of the percussive type, operated by
compressed air. Table XV indicates the number and distribution
of coal mines in which drills are used, and special measures
adopted for dealing with the dust. The table includes mines in
which measures are required to be taken under section 78 of the
Coal Mines Act, 1911, for the use of water sprays or jets or other
efficient means when drilling in ganister, hard sandstone or
highly siliceous rock " the dust from which is liable to give rise
to fibroid phthisis ".
In the " Midland and Southern " Division where such dust is not
liable to be produced, there is one colliery where dust traps are
used because the men prefer to do all drilling in this way, even
although there is a low percentage of silica in the rock.
Special Characters of the Silica Dust
The dusts met with in these processes are mainly those evolved
from (1) clift, bind or shale, which may contain as much as 40 per cent.
to 60 per cent, free silica; (2) rock, bastard rock or sandstone, in
which the free silica may range from 60 per cent, to 85 per cent.
The following particulars are from three mines where highly
siliceous rock is worked.
Free silica in the rock. . .
Combined silica
Dust counts during boring
(Owens' jet dust-counter,
particles in 1 c.c.) . . .

Mine A

Mine B

Mine C

57.0 %
6.5 %

73.3 %
9.9 %

73.2 %
4.3 %

2,290

2,180

2,220

Excluding the large particles and masses, the average size of the
particles was 1.5 p- and they were generally angular and of crystalline structure with here and there opaque mineral matter resembling
coal.

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PAPERS PRESENTED TO THE CONFERENCE

TABLE XV. —

DRILLING

IN ROCK

LIKELY TO

DANGEROUS

FROM

THE

POINT OF VIEW OF SILICOSIS AND MEASURES TAKEN TO DEAL WITH DUST

Division

Number
of
mines

Total
number
of
drills
in use

Measures taken
to
deal with dust

N u m b e r of
drills used
when no
measures
t a k e n to
deal with
dust

Remarks

(1)

(2)

(3)

(4)

(5)

(6)

Scotland

Northern

208

Yorkshire

192

North
Midland

North
Western

Not given

Cardiff and
F o r e s t of
Dean

N o t given

Swansea

Midland and
Southern

Nil

117

534
(where
given)

Totals

W i t h 4 drills respirators
are used.
W i t h 10
drills water p u t into
boreholes.
W i t h 74 drills water
sprays used.

134

W i t h 16 drills, respirators used. W i t h 45,
water or wet brattice
applied. W i t h 3 water
put into boreholes.
W i t h 2 water flows
through hollow drills
W i t h 2 drills, water
jets in use. W i t h 21,
respirators in use

126

At one mine respirators
used.
At one mine
dust trap used.
At
one mine dust collectors being installed
At 3 mines dust t r a p s
used.
At 9 mines
water spray used. At
2 mines respirators
used
W i t h 8 drills dust traps
used. W i t h 15 drills
water sprays used.
W i t h 2 drills respirators used
Nil

1 (mine)

219

Nil

50 drills are in use at
one mine where no
precautions are taken
b u t Inspector states
conditions are n a t u r ally d a m p .
One mine where respirators are used a H a y
Dust t r a p is to be
ordered.

Of t h e total n u m b e r
of drills not all are in
use regularly. A t o n e
colliery (20 drills)
trials are being made
of dust traps.

4 (mines)

A t 4 mines where
water
sprays
or
respirators used, dust
t r a p s are on order.

One mine where water
sprays in use, a dust
t r a p is on order.

Nil

At one colliery dust
t r a p used with h a m mer drills in every
t y p e of rock.

337

Evidence of Silicosis being Produced
During recent years evidence has been accumulating which
shows that certain workers employed below ground in coal mines
contract a disabling and even fatal fibrosis of the lungs. Some
particulars are given in the table below of fatal cases where the
diagnosis has been verified by post-mortem examination, and
which have come to the knowledge of the Mines Department.

SILICOSIS IN GREAT BRITAIN

429

These cases, although at first sight they seem so varied, when
reduced to main factors show that all the men worked for a certain
time in rock. Many of the men who drive cross measure drifts
do no other form of underground work, but there is also a large
number of workers who work on the coal face or as repairers
during most of their time and only do brushing or ripping from
time to time.
Where the post-mortem findings indicated silicosis there has
always been a definite history of stone drilling, though the period
of such employment may have been short or even very short.
TABLE XVI

No.

Age

Occupation

Coal miner

Period
of
employment

Duration
of
symptoms

Years
15

Months Months
18
7

Labourer and
coal miner's
assistant

—

Silicosis and
tuberculosis

H a r d ground
borer
coal miner

—'

Silicosis and
tuberculosis,
pleurisy and
nephritis
Silicosis, a n t h r a cosis and acute
bronchitis

3
17

Years
2

Coal miner

Coal mine
" repairer "

Mine sinker
and making
overcasts

Silicosis and
tuberculosis

—

Cause
of
death

6
(on
hard
ground)
H a r d heading
9
hammer
drill

H a r d ground
1914-1921
Coal miner

Period
of
disablement

4
14

3
3 yrs.

Silicosis and
tuberculosis
Silicosis

Silicosis and
tuberculosis
6 m t h s . Silicosis
Massive silicosis
cerebral
haemorrhage,
vascular
degeneration

Remarks

Worked in hard ground
nearly all of 15 years
(South Wales).
Hard ground = 56.1 %
total silica. Clift with
occasional beds of sandstone (South Wales).
8.631 grammes of dried
lung yielded 0.31 g r a m mes silica (South Wales).
Pennant, rock ; respirators
worn during last 5-6
years. No water used
with t h e drills (South
Wales).
Hard
ground,
mostly
clift (South Wales).
18 years ago worked on
hard
ground,
rock
contained 37.8 % free
silica (Somerset).
Ash of lung contained
18.4 % or silica. 20 years
ago used hand drills
(South Wales).
Always worked in h a r d
headings,
shale
and
P e n n a n t rock.
Stone =
51.3% Tree
silica.

It is impossible as yet to arrive at the true incidence of silicosis
in the coalfields, but now that the condition has been brought
within the application of the Various Industries (Silicosis) Scheme
a more uniform standard of diagnosis may be expected and systematic records are more likely to become available.

430

PAPERS PRESENTED TO THE

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Preventive Measures
These either take the form of the application of water as a spray
or through a hollow drill, or the extraction of dust by means of an
exhaust dust trap. Those mostly in use are: (i) the Hay original
model, (ii) the Hay modified model, of which there are 90 in use
(February 1930) (the whole of the equipment weighs only 27 lb.),
and (iii) the Sgonina.
Legislation
The Goal Mines Act, 1911, section 78, enforces the use of water
sprays or jets or other efficient means when drilling in ganister,
hard sandstone or highly siliceous rock " the dust from which
is liable to give rise to fibroid phthisis ".
General Regulations (Statutory Rules and Orders, 1920, No. 873)
dated 3 June 1920, apply to all mines under the Coal Mines Act, 1911,
in which ganister or other stone containing not less than 80 per cent.
of silica (Si02) is worked with a view to sale or manufacture.
Compensation
The Various Industries (Silicosis) Scheme, 1928, which came into
force on 1 February 1929, includes provisions for the payment of
compensation in cases of total disablement or death due to silicosis
or silicosis accompanied by tuberculosis in workmen employed
in " drilling and blasting in silica rock, in or incidental to the
mining or quarrying of other minerals ".
Bibliography
(1) The Influence of Incombustible Dusts in Preventing the Inflammation
of Coal Dust. Fifth Report of the Explosions in Mines Committee. Command
7132. His Majesty's Stationery Office, 1913. Price Is. l i d .
(2) The Effects of Inhaling Dusts Applicable for Stone-Dusting in Coal
Mines. By Dr. J. S. HALDANE. Seventh Report of the Explosions in Mines
Committee. Command 8122. His Majesty's Stationery Office, 1915.
Price 2d.
(3) " The Effects of Coal Dust upon the Silicotic Lung." By Dr. CUMMINS.
Journal of Pathology, 4 Oct. 1927.
(4) " The Effects of Dust upon Coal Trimmers ". By Dr. E. L. COLLIS
and Dr. J. C. GILCHRIST. Journal of Industrial Hygiene, April 1928.
(5) " The Occurrence and Clinical Manifestations of Silicosis among HardGround Workers in Coal Mines " By Dr. TATTERSALL. Journal of State
Medicine, April 1927.
(6) " Investigation into the Radiological Appearances of the Chests in
Coal Miners. " Annual Report of King Edward VII Welsh National
Memorial Association, 1929.

SILICOSIS IN GREAT BRITAIN

TIN

431

MINING

Distribution
The mining and quarrying of tin ore in this country is almost
entirely confined to Cornwall.
Employed

Persons

In 1901, 3,678 men were employed underground, and 2,690 males
and 357 females above ground. The Census for 1921 gives 2,098 workers below ground and 1,004 males and 37 females above ground
and in open workings.
In 1928 the number of wage earners was 2,800. There are
employed on rock drills some 700 men, and 240 rock drills are in use.
Of these, 220 are provided with water jets or sprays and 20 are
without.
Characters of the Dust
Dust arising from drilling, blasting and handling the material
is derived from the hard stone (containing 1 to 4 per cent, of
binoxide of tin) of which the lodes consist, and from the containing
rock, consisting of granite and " killas ".
Evidence of Silicosis
In the Registrar-General1 s Decennial Supplement for 1921, it is
stated t h a t the mortality of tin and copper miners in Cornwall is
excessive ; the comparative mortality figure from all causes is 3 V,,,
and for underground workers 4^3 times the average. It is pointed
out that at this time the industry was depressed and probably
most of the able-bodied men had secured mining work elsewhere.
Almost all causes contribute to this excess mortality, but chiefly
tuberculosis and respiratory diseases. The phthisis death rate
is 12 y2 times the normal and that for respiratory diseases 6.3 times.
" No other occupation in this country suffers to anything like
the same extent from silicosis, or illustrates like these men the
liability of this condition to lead to tuberculosis. " Deaths from
chronic interstitial pneumonia numbered 27 out of the 2,110 underground tin miners; compared with 60 deaths from this cause
amongst 912,126 coal miners.

432

PAPERS PRESENTED TO THE CONFERENCE

Besides the dust in tin mining itself, a factor in producing the
high incidence of silicosis and tuberculosis in the past was the
practice among tin miners of working for a time in the gold mines
of South Africa, where in former times the amount of silica dust in
the atmosphere was very great and the incidence of silicosis was
correspondingly high. There is no doubt, however, that tin mining in
Cornwall has produced silicosis in persons who have not worked
outside of this country. The following case illustrates this.
A tin miner who died in November 1928 had worked underground
in two tin mines in Cornwall for at least seventeen years, and
had never been in South Africa.
Post-mortem examination of the lungs was made and the
following condition was found. The surface of the right lung was
rough and the basal lobe was disintegrated owing to dense adhesions
of the pleura, which was torn. The inter-lobar fissures were obliterated by adhesions. The left lung appeared to be voluminous and
dark grey in colour. The pleural surface was free from adhesions,
except between the lobes, and showed sub-pleural nodules,
about 2 mm. in diameter, with white centre. The right lung, on
section, was of a dark grey colour, thickly studded with nodules
averaging 2 mm. to 3 mm. in diameter. The nodules were hard
to the touch and could be easily removed from the adjacent tissue.
At the right apex there was a dense mass of fibrous tissue, about
the size of a walnut, with whitish bands. The lower lobe showed
a red congestion with saneous exudation. The left lung on section
was seen to be studded throughout its whole extent with nodules
similar to those found in the right lung. There was, however, more
inter-nodular tissue and much of this was emphysematous, especially on the anterior aspect. There was no evidence of tuberculous
change at any part of the lung on macroscopic examination. The
glands about the bifurcation of the bronchi were enlarged, matted
together,. and almost black in colour. In consistence they were as
hard as cartilage. On section, they showed almost black surface
with white fibrous striai and fine mottling as of nodules.
Microscopic examination of the lungs shows the nodules to be
composed of a centre of structureless substance, with few distinguishable cellular elements and with groups of dust particles,
numerous at parts. This area is surrounded by bands of fibrous
tissue, the elongated nuclei lying at right angles to the radius of the
nodule. Outside of this is an area of less densely formed fibres, with
a considerable cellular infiltration and many blood vessels. In this
zone cells are seen with well-stained nuclei containing dust particles

SILICOSIS IN GREAT BRITAIN

433

in the protoplasm. Giant cells are seen in the inner zone of fibrous
tissue. In the alveoli and in the interalveolar septa, numerous cells
are seen loaded with dust particles ; many cells containing particles
are seen around the larger blood vessels: in these the majority of
the particles are under 1 « and many appear to be carbonaceous.
Larger particles with a crystalline appearance are to be found in
the interalveolar tissue.
Section of a bronchial gland shows great increase in fibrous
tissue arranged in nodules, and with thick deposits of dust in the
tissue between the nodules.
Methods of Prevention
A Report on the health of Cornish miners 1 states that " the dust
produced by rock drills can easily be prevented by a very small
water jet. The dust from blasting in close ends can be laid by a
powerful jet of water and air; and can in any case be avoided by
the man ".
Metalliferous mines are worked under Special Rules under the
Metalliferous Mines Acts.
Compensation
The Various Industries (Silicosis) Scheme, 1928, applies to all
workmen employed on or after 1 January 1929 in certain processes.
Amongst these is included, " drilling and blasting in silica rock, in
or incidental to the mining or quarrying of other minerals ".
The Scheme provides for the payment of compensation in cases
of total disablement and death.
Bibliography
(1) Report on the Health of Cornish Miners.
B y Dr. J . S. H A L D A N E ,
J . S. MARTIN and R. A. THOMAS. C o m m a n d 2091. His Majesty's Stationery
Office, 1904. Price I s . 2d.
(2) Report on the Incidence
of Miners'
Phthisis
in Cornwall.
By
Drs.

R. B U R N E T and

C. R O P E R .

1914.

(3) The Various Industries (Silicosis) Scheme, 1928. S t a t u t o r y Rules and
Orders, 1928, No. 975. His Majesty's Stationery Office.

POTTERY INDUSTRY

This industry includes several distinct branches, the subdivision
being determined by the nature of the article manufactured and the
materials entering into the composition of the ware. The principal
1

Cf. Bibliography, No (1).
28

434

PAPERS PRESENTED TO THE

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divisions are: (1) general earthenware; (2) china; (3) tiles; (4) sanitary earthenware; (5) electrical fittings; (6) jet and Rockingham;
(7) sanitary fireclay; (8) stone ware; (9) coarse ware.
The subject of silicosis is especially bound up with the first five of
these subdivisions, though the others have also some interest.
For the purposes of this paper the term " pottery industry " will
be restricted to subdivisions 1 to 5, and the others will be referred
to by name where necessary.
Distribution Geographically
A large portion of the pottery industry is concentrated in the
North Staffordshire Potteries, the city of Stoke-on-Trent. Other
groups of potteries are found in Derbyshire, Scotland, Dorsetshire,
Devonshire, Yorkshire, Shropshire, Worcester, Newcastle-on-Tyne,
Bristol and other places.
Employed Persons
In a Census of Employees of the British Pottery Manufacturers'
Federation, for 14 January 1926, the numbers employed in the
five subdivisions of the industry referred to above were: males
18,424 and females 23,402. In the several subdivisions the numbers
were :
General earthenware
China (combined with earthenware).
China
Tiles
Sanitary earthenware
Electrical fittings
Totals

Males
8,892
2,041
1,835
2,370
2,081
1,205

Females
13,783
2,810
2,806
1,729
285
1,989

18,424

23,402

Operations and Processes
From the point of view of the production of silicosis the industry
is divisible into two main parts: (1) earthenware, including general
earthenware; sanitary earthenware, earthenware tiles and
earthenware electrical fittings, and (2) china.
In the manufacture of earthenware the ingredients—ball clay,
china clay, china stone, felspar, and flint, in a ground state—are
mixed together in the form of liquid slip, from which the excess
water is removed by pressing; the resulting composite body is made
into the consistence convenient for the manufacture of the various
articles. In the plastic state it is used by throwers, pressers, jiggerers

SILICOSIS IN GREAT BRITAIN

435

and jolliers, handlers, modellers, etc., in the potters' shops. So long
as it remains moist it is harmless, but in the process of manufacture
fragments fall on benches and floors, or adhere to the clothing of the
workers, become dry and give rise to dust. After the article has
been made in the plastic form, partly dried, it is frequently subjected to the process of towing, that is, application of tow or other
similar substance to the surface of the article while it revolves
on a mechanically driven disc, thus giving rise to large quantities of
dust for which localised exhaust is required to be provided. In
other cases the formed article in the " green " state is fettled, that
is, irregularities of surface and edges are removed by hand by
rubbing or scraping. This gives rise to dust as in the case of
" towing ", and with large articles such as sanitary ware the
application of localised exhaust is difficult.
In the potters' shops, the body or slip may be used by the potter,
" caster ", in the liquid state instead of in the plastic state. When
this is done it is poured into moulds of plaster of Paris and allowed
to set. Afterwards the parts of the moulds are removed and the
article in a semi-dry state is subjected to the process of fettling and
finishing, as in the case of " thrown " or pressed articles.
When the articles shaped by the potter into their final form
have been dried in a drying chamber to a condition known as
" white hard ", they are placed in " saggers "—large flat-bottomed
basins made of fireclay—for firing in the oven. In the case of
earthenware the material is " placed " in the saggers by " placers ",
the articles being prevented from touching the sagger or each
other by interposing some siliceous sand or coarsely ground silica
rock. In the case of china, however, the articles require much more
support in the process of firing than do earthenware articles,
and to provide this, finely ground flint is used. Flat ware is
embedded in flint to a greater or less extent, by the processes of
" placing ", called " Hinting ", where enough flint is used to
separate the flat ware when arranged in a pile in the sagger;
" bedding " when the whole sagger full of ware is filled up with
ground flint, and " settering ", when a separate mould covered with
flint is used for each piece of ware. Hollow-ware is treated on similar
lines so far as its form will allow, cups and similar articles being
placed with the rims, to which an adhesive is applied, in apposition.
The process is known as " boxing " of cups.
In the processes of " placing " earthenware and china in saggers,
the placers are exposed to dust produced in the manipulation of the
placing material, a relatively coarse sand in earthenware, a finely

436

PAPERS PRESENTED TO THE CONFERENCE

ground flint in the case of china. The processes in china placing are
therefore relatively much more dangerous, involving handling
of the more finely ground and more highly siliceous flint. The
china " placers " rank amongst the most severely affected workers
who contract silicosis in the pottery industry.
After the firing in the ovens, the saggers are removed by " biscuit"
oddmen, who remove the ware now known as " biscuit " from the
saggers, empty out the placing sand or flint and sift it for future
use when mixed with a proportion of fresh or " green " placing
sand or flint. After removal from the saggers the ware is placed
in baskets and conveyed to the biscuit warehouse where it is
subjected to a variety of processes to remove the adherent placing
sand or flint, in preparation for glazing or underglaze decoration.
The biscuit warehouse processes include hand brushing, placing
in and removal from scouring machines, in the form of rumblers,
" flat knocking ", " batting " and fine brushing. All these processes
in the biscuit warehouse give rise to dust from the adherent placing
sand or flint. They are carried on almost entirely by women.
When the biscuit ware has been cleaned, no substantial risk of
silicosis arises in the subsequent processes of manufacture until
glazing and decoration has been completed. Then polishing and
grinding are employed to remove blemishes, etc. This is done by
means of a revolving wheel which may be composed of cork or
stone, to which ground flint is applied mixed with water, or an
abrasive wheel of carborundum or similar material may be used.
Where flint is used, it gives rise to dust and is liable to produce
silicosis.
Glazes contain some free silica, but the evidence that disabling
silicosis is produced from this source is not conclusive.
The industry can be divided into some sixty occupations. Half
of these are occupations in which the worker is exposed to the
inhalation of silica dust to a greater or less extent. The following
is a list of these occupations, with the approximate number of
persons employed:
Males

1. Millmen
2. Slipmakers and dust house attendants .
3. Modellers
4. Mould makers (dust of plaster of Paris) .
5. Throwers and lookers-to ware
6. Turners and lathe treaders
7. Handlers
8. Plate makers and towers
9. Dish makers
10. Hand basin makers
11. Saucer makers

208
811
64
555
202
471
258
583
138
92
186

Females

—
13
1
6
147
295
720
788
132
132
497

437

SILICOSIS IN GREAT BRITAIN

12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.

Cup and bowl makers
Jiggerers and jolliers
China flat jiggerers and jolliers . . . .
Casters, earthenware and china . . . .
Sanitary casters
Hollow-ware pressers, earthenware and
china
Sanitary pressers
Tile pressers
Electrical dust pressers
Fettlers (electrical fittings)
Sagger and marl grinders
Biscuit placers
Biscuit oddmen
Biscuit firemen
Biscuit warehouse
Cdost placers and oddmen
Polishers and grinders
Tile slabbers
Labourers

Males

Females

75
307
74
307
729

702
535
16
914
13

229
132
306
25
16
760

5
1
712
520
479

1,158

23
16
1

272
219
180
1,723

419
124
526

—

1,710

162
37
5
3

The exposure to risk of dust inhalation in these occupations
may be stated briefly as follows :
1. Millers and mill labourers. — Only men are employed. They
carry out the preparation of flint—calcining, breaking, crushing and
milling, and the exposure is to flint dust. They are also employed
in grinding broken biscuit ware (pitcher) in the preparation of glaze;
manipulation and milling china clay, ball clay, china stone, felspar;
calcining and grinding of bone; grinding of marl and fireclay.
1. Slipmakers include slipmakers' assistants, slip pressers and press
emptiers. It includes those employed in mixing and manipulation of
the mixed materials for the' body of earthenware, sanitary earthenware, china, fireclay, mixed fireclay and earthenware and marl. It
also includes those engaged in the preparation of a material known
as " d u s t " for the body of tiles and electrical ware. Further processes
in the preparation of this dust consist in the drying and pulverising,
remoistening and sifting, before the tiles or electrical fittings are
pressed into their final shape.
3. The potters' shop. — In the potters' shop are those employed
in the manufacture of the ware before it is fired. The group includes
those engaged in the following occupations: throwers, turners and
lathe treaders, hollow-ware and sanitary pressers, ornamenters and
figure makers, casters and spongers and fettlers for casters, handlers
and handle makers, electrical and tile dust pressers and fettlers,
machine workers (jiggerers and jolliers), plate makers, saucer makers,
flat pressers, hand basin makers, dish makers, general jiggerers and
jolliers, cup and bowl makers; also those workers attached to machine
workers, towers, spongers, fettlers, scallopers, etc. In the potters'
shop the workers are exposed to dust from the mixed body of the
ware, the character of the dust varying according to the composition
of this body.
4. Mould makers are employed in making moulds from plaster of
Paris, to which dust they are alone exposed unless by proximity they
are also exposed to dust from potters' shops.

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5. Modellers are occasionally employed as mould makers as well
as modellers of the ware.
6. Sagger makers are engaged in grinding marl, broken saggers, etc.,
and the sifting of such material in the manufacture of saggers by
hand and by machine. The exposure is to dust of marl and a varying
quantity of flint or ware body from old saggers, etc.
7. Biscuit placers and biscuit oddmen include those engaged in the
handling and sifting of flint or sand in preparation for its uses in
placing; in the placing or bedding of biscuit ware in the sagger house;
in the preparation of the ovens, and in emptying the ovens and the
removal of ware, sand and flint from saggers. In the manufacture
of china, the bedding material is flint, and the workers in these occupations are exposed to dust of flint. In earthenware, sanitary, and
other types of ware, the placing material is sand, and it is to the
dust of this sand that workers are exposed.
8. Biscuit firemen include those employed in firing biscuit ovens,
but not in connection with the bedding of biscuit ware.
9. The biscuit warehouse includes those engaged in handling the
ware after its removal from the biscuit sagger house; in charging and
emptying rumblers and other mechanical apparatus for cleaning the
ware; in brushing, stopping, stamping, selecting and looking over the
ware. The dust to which these workers are exposed is, in the case
of china, flint; in the case of earthenware, the placing sand.
10. Glost placers and glost oddmen include those employed in the
preparation of new saggers, by flinting and glazing the exterior and
flinting the interior of the saggers; in the placing of glost materials,
the filling and emptying of glost ovens, the emptying of glost saggers,
and in brushing saggers. There is a slight degree of exposure to flint
dust.
11. Polishers and grinders include those employed in the polishing
and grinding of ware by the use of mechanically driven wheels, on
some of which ground flint is placed, or by the use of a sandblast.
Exposure is to finely divided flint dust.
12. Tile slabbers are employed cutting and grinding tiles for fitting.
The dust is that of the fired tile body.
13. Labourers include all those engaged in sweeping the shops and
yards and in cleaning localised exhaust plants, rumblers, sandblast, etc.
14. Slip carriers and mould runners. — The exposure to dust varies
greatly according to the particular duties and the type of ware produced.
Special Characters of the Silica Dust and Reference to the Presence
of Other Dusts
The composition and character of the dust to which workers
in the pottery industry are exposed, vary according to the occupations and the branch of the industry in which the worker is
engaged.
In the manufacture of earthenware, at which the slip or body
is liable to become dry, i.e. at all parts of the process before the

439

SILICOSIS IN GREAT BRITAIN

first firing, the dust produced consists of the body, that is, a mixture
of clays, china stone, felspar and flint in a fine state of division.
China stone contains about 73 per cent, total silica, part of which
is free as quartz. Flint is almost pure silica, containing 98 per cent.
Si0 2 , in an extremely fine crystalline (crypto-crystalline) condition,
set in colloidal silica which makes up 1.5 per cent, to 2 per cent.
of the rock. Felspar contains about 64 per cent, of silica combined
as silicates.
In the manufacture of china no flint is added to the body of the
ware, which consists of calcined bone, china clay and china stone.
A small amount of free silica as quartz is derived from the china
stone.
The chemical composition of atmospheric dust in certain pottery
processes has been determined by H. Oliver, B.Sc, in a Report
on an investigation of atmospheric dust in pottery workshops 1
(the Report was for private circulation).
TABLE

No.

XVII. —

Process

SiOi

TABLE

TiOa Al90a

OF COMPLETE

FejOa CaO

ANALYSES

OF DUSTS

MgO

KjO

Na s O

Loss
on
ignition

COLLECTED

Ps>08 Total

Remarks

2. Towing
Earthenware

Less
53.80 t h a n
0.01

16.80

0.90

2.80

0.90

2.60

2.50

20.00

—

3. Brushing
Earthenware

62.08

0.48

16.36

0.80

2.44

0.12

1.10

3.00

14.08

4. Dry F e t t ling China 36.34

0.00

26.54

0.48

16.64

0.02

1.92

1.84

8.18

100.46 Sand very
dry. Centre
of room.
8.26 100.22

5. Placing,
etc. China
Biscuit
96.20

0.00

1.74

0.12

0.68

0.00

0.08

0.64

9. China
Biscuit
Brushing 82.88

1.04 Trace 100.50 Alumina a n d
Phosphate
indicate
dust from
green ware.

0.00

1.82

0.54

2.52

0.00

1.52

1.56

8.68 Trace

13.12 Trace

Placing
China
Biscuit.

74.80

0.00

3.16

0.64

2.84

0.04

3.70

1.50

12. Flint
Sieving

84.80

0.00

1.20

0.48

3.48

0.16

2.80

0.90

10.

6.08

100.30

—

99.52 Alumina a n d
Phosphate
indicate
abrasion of
ware.
99.80
99.90

The relatively high alkalis and lime in every case indicate that these are general constituents of
atmospheric dust, although a portion of the lime may be from the moulds and bats.

Cf. Bibliography, No. (1).

440

PAPERS PRESENTED TO THE

CONFERENCE

An investigation into the dust content of the atmosphere of
workplaces in the pottery industry was undertaken to provide
a connecting link between the state of health found by examination
of the workers and the hygienic conditions under which their work
is carried on, with a view to the elucidation of the physical aspect
of the causation of disease and to assist in the problems of the
improvement of those conditions. The notes on the incidence of
respiratory disease which follow the dust determinations in the
occupational groups of this section have been taken from the
Report of a Medical Enquiry carried out by Drs. Sutherland
and Bryson in 1925 1, under the direction of the Home Office.
This section covers most of the occupations in which there is
exposure to silica dust in the manufacture of earthenware and china,
and in addition, some investigation into the stoneware branch
of the industry. From the hygienic point of view the stoneware
industry is probably similar to the jet and Rockingham branch
of the industries, in which there is at present no conclusive evidence
of incapacitating silicosis.
Flint Milling
While the preparation of powdered flint is essential for the
manufacture of all classes of pottery except coarse ware, stoneware
and fireclay, although in these it may be used for the glazes or
surface body, it might be considered as separate from the processes
of pottery manufacture. Although some potteries have their own
flint-milling department either within the precincts of the pottery
or in a separate factory, the industry of flint milling is commonly
carried on by separate firms who may supply the flint for purposes
other than pottery manufacture, and they may combine the
milling of other materials with that of flint. Further, the workers
in this industry do not belong to the Societies of Pottery Workers.
The methods in general use are as follows. Home or foreign flints
are placed in a large kiln with fine coal and fired, continuously.
As required, the calcined flints are removed, together with the ashes
of the fuel, from a small orifice at the bottom of the kiln, and are
washed by spraying with water from a hose or are shovelled dry
into barrows and wheeled to the mill room or to a stone crushing
machine. The flints may be broken by hand hammer, the remainder
of the grinding being done wet in buhrstone mills, or a preliminary
crushing may be done before the material is placed in the mills.
1

Cf. Bibliography, No. (2).

441

SILICOSIS IN GREAT BRITAIN

The grinding is done with sufficient water to keep the mass fluid :
from the mills it is passed to sedimenting tanks where the water is
separated and the flint is dried by heat until it contains only
from 5 to 10 per cent, of its weight of water. The mass is broken
up and removed by shovelling as required. Dust is produced
in removing the calcined flints from the kiln, though most of this
dust is ash : any process of manipulating the flints in this condition
TABLE

Precess

(1)
(2)
(3)
(4)
(5)

(6)

(7)
(8)
(9)

(10)
(11)
(12)

Number
of particles
in 1 c.c.

XVIII
Percentage over
2 f*

Remarks

R a k i n g calcined flints
2,687
Most of the particles are
2.6
from t h e kiln
mineral.
2,289
The sample closely
Sieving flint chips
2.8
from the kiln
resembles (1).
Sieving calcined flints
N o t more t h a n 1 0 % of
1,793
0.7
with an enclosed methe particles are minechanical shaker
r a l ; others are soot.
Shovelling crushed
2,132
A b o u t 1 5 % of the p a r t 1.7
calcined flints into
icles are mineral;
crusher: to windward
others are soot.
Charging the flint
4,314
A dense s a m p l e ; the
9.1
crusher; sample taka m o u n t of soot is negen to leeward of maligible.
chine
Compare (5) with t he following sample tak Bn at a pottery in Glasgow,
at the crusher, under cover, wher e the material was kept wet with water
from a hose.
Shovelling calcined
458
A sparse record; p a r t 6.8
flints, wet, into the
icles evidently flint,
crusher
varying in size from
1 (x to 6 (X.
Sample taken at a flint-milling factory in G lasgow, in a neighbourhood
free from excessive d ust and smo ke, and in lamp weather.
Control taken in yard,
1,156
Most of the particles are
0.3
to windward of prosoot.
cess
Shovelling calcined
2.2
1,807
Particles a p p a r e n t l y inflints and ashes from
clude flint, ash, and
the kiln : to windward
coal.
Sieving ashes, con1,325
A b o u t half of the part0.6
taining flint chips,
icles are refractive,
from t h e kiln: open
and probably some of
air
this is flint.
Shovelling calcined
1,120
1.0
Fine ashes and some reflints in the open: to
fractive material, prowindward
bably flint.
1,446
Breaking calcined
0.6
Flint forms a b o u t 5 0 %
flints with a h a n d
of the total.
hammer
1,530
In the drying room,
0.8
Occasional large p a r t turning over masses
icles, a p p a r e n t l y flint.
of ground flint

442

PAPERS PRESENTED TO THE CONFERENCE

is liable to produce dust, shovelling, knapping by hand hammer,
sieving and, especially, grinding in a stone - crushing machine.
A small amount of dust arises in shovelling the dried flint into carts
or bags, and where bags are used much dust may be produced in
handling them.
Two series of dust samples were taken with Owens' jet
dust-counter, one in Stoke and the other in Glasgow, and since the
general atmospheric conditions are not comparable, the series are
stated separately.
Samples taken at a flint-milling department in a pottery in
Stoke-on-Trent are given in table XVIII.
The most dangerous process in the milling of flints for use in
pottery manufacture is that of crushing the calcined flints in a
machine crusher. Sometimes this is replaced by breaking with a
hand hammer, with much less risk, especially if the flints are freely
wetted during the process. A liberal use of water immediately after
drawing the flints from the kiln and at the crushing process would
minimise or remove the danger : while sieving could be done by
covered machines or could be modified by a process of washing.
Silicosis was diagnosed by radiological examination in
3 flint-millers out of 7 examined; the earliest definite evidence
occurred after employment for from ten to fifteen years. Fibrosis
of the lungs was diagnosed by medical examination in 8 out of
13 flint millers examined, the earliest manifestation being after
ten to fifteen years' employment.
Note. — Some of these classed as flint millers had been employed
for various periods at other occupations in potteries or otherwise.
China
The following series of dust determinations represent processes
which fall into three groups: (1) processes before biscuit placing,
in which the dust is derived from the unfired body; (2) processes
in biscuit placing, and (3) processes after the firing of the biscuit
ware, in which the dust is derived from the flint, adhering to the
articles as a result of the process of placing them in the saggers
for firing.
In column (5) an estimate is given of the proportion of the count
which consists of particles, apparently composed of flint. To arrive
at the actual pollution of the atmosphere by flint it is necessary
to estimate the number of particles of flint per cubic centimetre
of air by taking the percentage given in column (5) out of the
number in column (3).

443

SILICOSIS IN GREAT BRITAIN

(1)

Processes before Biscuit Placing (in the Potters' Shops)
TABLE

Process

Position

(1)

(2)

XIX

Number Percentof parage
ticles
over
in 1 c.c.
2 f*

Remarks

(3)

(4)

(5)

(1)

Jollying hollow-ware

Jolly shop

5,350

1.1

About 20% of the
particles are refractive ; clumps
and splashes.

(2)

Dry fettling

Hollow-ware
casting shop

6,916

2.5

At least 50% of
particles are refractive ;
splashes, aggregates and clumps.

(3)

Dry fettling

China casting
shop

5,567

2.1

About 20% of the
particles are refractive;
splashes and
loose aggregates.
Numerous smoke
particles, discrete
and clumped.

(4)

Fettling china hollowware

China potters'
shop.

4,470

0.9

Much soot. About
10% of the particles are refractive.

(5)

Dry fettling
on whirler

Jolly shop

6,169

2.3

About 30% of the
particles are refractive ; splashes
and clumps. Considerable amount
of soot.

(6)

Dry fettling
on whirler

Jolly shop

7,157

2.2

Over 80% of the
particles are refractive ; numerous splashes and
closely aggregated masses.

(7)

Dry fettling
on whirler

Jolly shop

4,555

1.8

About 30% of the
particles are refractive ; others
soot.

(8)

Looking over
and dusting

Greenhouse

3,615

2.0

About 40% of the
particles are refractive ; others
soot.

444

PAPERS PRESENTED TO THE CONFERENCE

This series of dust counts is sufficient to indicate that a source
of danger exists in workrooms in which the china body is in the
damp or even wet state. The dust is certainly derived from particles
of dry material floating in the air of the rooms. In the wet processes
the dust is produced from fragments falling on the benches, floors
and clothing of the workers, where it dries readily in the high
temperatures prevailing and is set free as adventitious dust. In the
fettling processes, the ware is sometimes sufficiently dry to cause
dust directly from the action of the fettling tool.
Silicosis was diagnosed by radiological examination in china
saucer-makers employed 15-20 years, in flat jiggerers and jolliers
employed 20-25 years, and in a sliphouse worker employed over
40 years. Fibrosis of the lungs was diagnosed, by medical examination of china workers, in sliphouse workers and in handlers,
employed 10-15 years; in saucer-makers and flatfettlers, employed
15-20 years; in lookers-to-ware and flat jiggerers and jolliers,
20-25 years; in throwers, employed 25-30 years; in lathe-treaders,
employed 30-35 years; and in turners and hollow-ware pressers,
employed over 40 years.
(2) Processes in Biscuit Placing
In the manufacture of chinaware, the principal dust hazard
is due to the use of flint as the placing material in which the green
ware is fired.
The process, as denoted in column (3), relates to the variety
of placing adopted with different forms and classes of ware. Control
samples were taken, three in the yards of the potteries and one inside
a placing room, in which no work had been done that day, for the
purpose of comparison.
Looking at the data provided by the tests the actual number
of particles of flint, that is, the percentage in column (5) of the
number in column (3), the following facts appear. The lowest counts
are controls; number (18) taken in Hanley with the wind blowing
over Hanley Park, which gave 65 particles of mineral; and
number (19) at Fenton, which gave 151 particles. The lowest
placing sample is number (15) with 338 particles'—flinting with
a current velocity of 800 feet at an exhaust opening 24 by 2 inches.
Four placing samples are recorded below 500 particles in a cubic
centimetre, out of 29 samples taken at all the varieties of placing
china biscuit ware. Eleven are over 500 and below 1,000 particles
in a cubic centimetre. Eight are over 1,000 and below 2,000 particles
and six are over 2,000 particles in a cubic centimetre.

445

SILICOSIS IN GREAT BRITAIN

Silicosis was diagnosed by radiological examination in 16 chinabiscuit placers out of 22 examined: the earliest definite evidence
was found after 10-15 years' employment. Fibrosis of the lungs
was diagnosed by medical examination in 19 china-biscuit placers
out of 25 examined, the earliest case occurring after 5-10 years'
employment.
TABLE

No.

Process

(1)

(2)

Number
Percentof particles age over
in 1 c.c.
2F

Remarks

(3)

(4)

(5)

4,554

0.1

Control: centre of
yard
Bedding saucers

6,175

0.5

Boxing cups

5,699

2.6

2,602

0.3

Control: centre of
yard
Bedding

647

4.6

Flinting

825

3.6

Boxing cups

6,832

0.8

Bedding

5,940

0.3

9.
10.

Flinting
Bedding

5,916
4,482

0.27
0.7

11.

Flinting

5,615

0.5

12.

Bedding

3,807

0.3

13.

Boxing cups

5,097

1.1

14.

Bedding

1,434

2.5

15.

Flinting

3,384

0.1

16.

Settering

2,554

0.6

17.

Bedding

2,530

1.3

18.

Control: outside

1,373

0.3

19.

Control: placing
room
Boxing cups

1,518

0.2

2,506

1.2

Over 90% of the particles are soot.
30-40% of the particles
are flint.
60% of the particles are
flint.
Over 90% of the particles soot.
About 80% of the particles flint: some aggregates.
General characters similar to (5).
About 20% of the particles flint.
About 40% of the particles flint.
Characters similar to (8).
30% of the particles are
flint.
30% of the particles
flint: similar to (10).
10-20% of the particles
flint.
40% of the particles are
flint.
About 50% of the particles flint.
About 10% of the particles are flint: difference between 14 and
15 due to the effect of
exhaust draught.
20-30% of the particles
flint.
About 30% of the particles flint.
A few isolated mineral
particles; others soot.
Off work all day: 10% of
particles are mineral.
40-50% are flint particles :
some aggregates.

20.

446

PAPERS PRESENTED TO THE CONFERENCE
TABLE

No.

Process

(1)

(2)

(continued)

Number
Percentof particles age over

Remarks

in l c.c.

2 f*

(3)

(4)

(5)

40-50% are flint particles
some fine clumping.
20% flint particles:
clumping of soot.
40% flint particles:
some clumps.
Similar to (23), but less
clumping.
A large proportion of fine
particles of flint.
About 15-20% are flint
parts: fine clumping.
20-30% are flint particles.
About 20% of the particles are flint.
About 20% of the particles are flint.
About 30% are flint
particles.
Only about 10% are
flint particles.
About 10% are flint
particles.
About 10% are flint
particles.

21.

Bedding

3,338

0.1

22.

Flinting

1,759

0.8

23.

4,808

0.5

24.

Bedding and flinting
Boxing cups

5,266

0.7

25.

Bedding

4,241

0.2

26.

Boxing cups

8,989

0.4

27.

Settering

2,807

0.4

28.

Boxing cups

3,060

0.3

29.

Settering

4,109

0.2

30.

Settering

2,723

0.9

31.

Bedding

3,747

0.1

32.

Flinting

4,964

0.2

33.

Settering

5,603

0.1

(3) Processes after Firing of the Biscuit Ware
The series of dust counts given in table XXI, representing
processes undertaken for the removal of adherent flint from fired
china-biscuit ware, serves to show that a high degree of danger
exists to the workers in these processes. An inspection of thi s work
demonstrates the necessity for concentrating attention on the
removal of as much of the flint as possible in the earlier processes
after the ware is taken from the saggers. It is just in these early
processes that the methods are inclined to be haphazard and the
labour less skilled, with the result that the workers in subsequent
processes are exposed to a high degree of risk.
Silicosis was diagnosed by radiological examination in biscuitoddmen, employed 5-10 years, and in biscuit warehouse-women
employed 15-20 years. Fibrosis of the lungs was diagnosed by
medical examination in biscuit-oddmen employed less than 5 years,
and in biscuit warehouse-women employed from 5-10 years.

447

SILICOSIS IN GREAT BRITAIN
TABLE

XXI
Number Percentol parage
ticles
over
in 1 c.c.
2 v-

Process

Position

(1)

(2)

(3)

(4)

(5)

A b o u t 5 0 % refractive particles ;
others soot.
A b o u t 6 0 % of the
particles are refractive. Aggregates and masses.
Quite 50 % of
particles are re. tractive ; others
soot.
Over 50 %
of
particles are refractive ; others
soot. Very few
clumps.
A t least 8 0 % of
the particles are
refractive.
A b o u t 4 0 % of the
particles are refractive ; others
soot. Groups and
masses.
A b o u t 3 0 % of t h e
particles are refractive, probably
flint; others soot.
Only a b o u t 1 0 %
of the particles
definitely refractive.
A large proportion, over 80 % ,
of particles are
refractive.
A b o u t 4 0 % of
particles are refractive ; others
are soot.
Over
50 % of
particles are refractive. Dense
sample.
A b o u t 7 0 % of t h e
particles are refractive ; others
are soot.
Majority of p a r t icles are soot ;
n o t more t h a n
2 0 % are refractive. Soot thickly
clumped at parts.

Emptying
saggers

Mouth of china
biscuit oven

11,724

0.5

Sifting flint

Hovel of No. 1
biscuit oven.

3,916

5.3

Filling and
drawing

11,544

0.6

Emptying
hollow-ware

Mouth of mechanical flat
knocking m a chine.
Scouring shop

10,411

0.8

Filling racks
for d r u m s

Scouring shop

9,194

0.6

Filling racks
of hollowware

Scouring shop

5,121

1.0

Placing cups
in racks

China biscuit
scouring shop

7,423

1.3

Removing
cradles of
ware

China biscuit
scouring shop

5,964

0.2

Emptying
scouring
drum

Scouring shop

9,616

0.6

10. E m p t y i n g
racks of
hollow-ware

Scouring shop

5,157

0.9

11. B a t t i n g before printing

Scouring shop

10,399

0.3

12. B a t t i n g with
j e t of compressed air

Scouring shop

8,242

0.3

13. Fine-brushing
saucers with
revolving
brush

Scouring shop

7,073

0.5

Remarks

448

PAPERS PRESENTED TO THE

CONFERENCE

Earthenware
In the manufacture of earthenware there are many processes
which give rise to dust: these may be divided into four groups;
(1) the handling of the raw materials up to the completion of the
" b o d y " ; (2) the fashioning and drying of articles of pottery;
(3) the placing of biscuit ware, emptying saggers, and preparation
for glazing; (4) the making and applying of glaze, glost placing and
polishing. Other incidental occupations are mould and sagger
making.
When the slip or body has been made, and passed to the potter
to be fashioned into an article of pottery, portions of the body
become detached and, falling on the benches or floor, become dry
and are crushed and give rise to dust. This dust exists in the
atmosphere of the workplace as free particles of the constituent
ingredients of the body, and also as minute masses of all the
ingredients together. Collected with the Owens' dust-counter and
examined under the microscope, the particles are seen to consist
of masses firmly bound together, aggregates of loosely attached
particles, and splashes of particles which appear to have been held
together until the mass struck the surface of the recording slide.
Under these conditions the clay particles appear with a faintly
differentiated outline, as contrasted with the angular or finely
facetted and highly refractive flint or quartz particle. Discrete
particles are also seen scattered throughout the field, both ot the
clay and the crystalline character.
The following samples were taken in the processes of manipulating
the plastic " body " :
TABLE

Position
(1)

1.
2.

Potters' throwers
shop. Same factory as (2) and (3)
Turners' shop — a
large room in which
throwers also were
at work
Hollow-ware
pressers' shop

XXII

Number
Percentof particles age over
in 1 c.c.
2 f*

Remarks

(2)

(3)

1,398

Many discrete refractive
particles.

783

4.6

About 50% of particles
are refractive.

1,265

2.2

Much of the sample is
soot; there are discrete refractive particles.

(4)

SILICOSIS IN GREAT BRITAIN

TABLE

Position
(1)

5.
6.

Hollow-ware pressers'
shop—a very large
room (same factory
as (5))
Hollow-ware casters'
shop—a large room
Small jolly shop. General air of room at
breathing level

449

xxii (continued)

Number
Percentof particles age over
in 1 c.c.
2H-

Remarks
(4)

(2)

(3)

1,458

3.6

50%-70% of particles
are mineral.

1,506

0.5

916

5.6

The splashes contain refractive particles.
Many close splashes.
Impossible to count
refractive particles in
splashes.

In the above six samples the notable feature is the presence
of splashes which account for most of the mineral content of the
atmosphere, while free particles are comparatively scanty.
The following samples were taken at processes in manipulating
the dried body, i.e. unfired or green ware:
TABLE XXIII

Position

9.
10.

11.

Remarks

(2)

(3)

(4)

In drying stove : a boy
moving to and fro
with ware and
moulds
Jolly shop. Dry fettling edges of earthenware saucers

1,000

6.3

Much of the mineral
matter is in clumps
and splashes.

2,036

2.7

Flat pressing shop.
Fettling plates in
the green state
Towing flat ware at
a temporary bench,
without exhaust:
room warm

337

4.2

About 50% of particles
are mineral, some discrete and some in
splashes.
A very sparse sample.

964

17.2

1,048

8.9

(1)

Number
Percentof particles age over
in 1 c.c.
2f*

Towing. Same as (10)
but with the instrument warmed to
t e m p e r a t u r e of
room or slightly
above it, to test
variation in formation of aggregates

Most of the mineral material is in clumps and
splashes.
In this
sample clumps are
counted as single particles over 2 ¡t.
Similar to (10) but
shows slightly less
clumping and is more
uniform.

450

PAPERS PRESENTED TO THE CONFERENCE

TABLE

xxiii (continued)

12.

Number
of particles
Position
in 1 c.c.
(t)
(2)
1,036
Towing. Same fact o r y as (10) and
(11). Provided with
localised e x h a u s t

13.

Towing. Under hoods,
with e x h a u s t

1,747

3.0

14.

Towing. W i t h localised e x h a u s t a n d
with a hood not in
position
Towing. Same as (14)
b u t with hood in
position

747

2.1

807

1.4

3,012

1.0

1,590

1.1

15.

16.

17.

Towing house in another factory.
Under localised exhaust
Towing plates. Towing shop. W i t h exhaust

Percentage over
2 f
(3)
8.9

Remarks
(4)
Character of sample resembles (10) and (11),
and counts are remarkably similar.
The
effect of localised exh a u s t d r a u g h t in this
case is probably nil,
or is counterbalanced
b y a c u r r e n t of d u s t y
air drawn p a s t the
worker from the same
or adjoining rooms.
Many splashes of mineral
m a t t e r , also m a n y
free particles.
A b o u t 5 0 % of particles
are mineral, chiefly
in splashes.
Similar to (14) b u t soot
particles are more frequently
single, increasing the count.
Many of the particles
are soot; less t h a n
2 0 % mineral.
Much soot. A b o u t 1 5 %
to 2 0 % mineral.

Samples in which the dust is from the placing sand :

18.
19.

20.

21.

TABLE
Number
Position
of particles
in i c.c.
(1)
(2)
Placing biscuit ware
1,723
in saggers.
In the kiln; one m a n
inside, 4 men outside and one j u s t
outside, e m p t y i n g
saggers. Placing
sand is a pounded
sand
Biscuit warehouse.
Brushing biscuit
earthenware, 3
girls helping
Ornamenting shop.
O r n a m e n t i n g dinner-ware.
Large
room with windows
open

xxiv
Percentage over
2 -«
(3)
7.4

Remarks
(4)
A b o u t 7 0 % of particles
are mineral, much in
splashes.
Great majority of particles are soot ( 8 0 % ) ;
some of the mineral in
splashes and clumps.
Large sand particles
scanty.

2,879

0.6

2,108

0.6

A b o u t 9 0 % soot. Mineral for the most p a r t
discrete.

1,108

0.7

Particles are chiefly soot,
with a few scattered
discrete and clumped
refractive particles.

SILICOSIS IN GREAT BRITAIN

451

Of workers employed in the manufacture of earthenware in
occupations in which the unfired composite body is handled,
that is, from the sliphouse to towers and lookers-to-ware, 46 males
and 15 femaleswere examined radiologically. Silicosis was diagnosed
in 26 males and 3 females. The male cases of silicosis were distributed amongst platemakers, handlers, dishmakers, throwers,
jiggerers and jolliers, hollow-ware pressers and casters (some of
whom had been employed previously as hollow-ware pressers).
The female cases of silicosis were found amongst towers,
fettlers-for-casters and cupmakers.
Fibrosis of the lungs was diagnosed by medical examination
in 49 males out of 88 examined and in 12 females out of 89 examined.
Bronchitis was found in 13 and some evidence of tuberculosis
in 3 male workers.
Radiological examinations were made of 7 earthenware-biscuit
placers and 1 case of silicosis was diagnosed. Two earthenware
biscuit warehouse-women were examined radiologically and
10 medically, with negative results. Fibrosis of the lungs was
diagnosed in 10 out of 18 male earthenware biscuit placers. The
dust hazard to which these workers are exposed is that from the
placing sand.

Tiles

Ornamental and plain tiles are made from a body resembling that
of earthenware; in the case of white body there is up to about
40 per cent, of flint. In preparing the body for the press, the slip
is freed from excess moisture by pressure, dried and ground. The
dust given off into the atmosphere in the process of grinding the
dried mass consists of the total constituents of the body, and as
regard; the tendency to aggregate formation and the physical
separation of the particles, the conditions are similar to those
obtaining in the manufacture of earthenware, in which the body
becomes disintegrated about the benches, floors, stoves, etc., in
potters' shops.
In one tile-making factory, 5 samples were taken at some of the
dusty processes (cf. table XXV).
Another kind of dust is met with in tile manufacture—the

TABLE

XXV

Process

Position

Number
of particles
in 1 c.c.

Percentage
over
2 f*

Remarks

(1)

(2)

(3)

(4)

(5)

Control

Grinding room.
Taken at 2 p.m.
work h a v i n g
been suspended for an h o u r

1,277

1.5

About 1 0 % - 1 5 %
of t h e particles
are mineral some
in aggregates.

Feeding hopp e r of grinding machine

Same grinding
r o o m a t 2.35
p.m., work having been res u m e d a t 2.15

3,868

Very dense sample
w i t h m a n y aggregates. T h e whole
c o u n t represents
mineral.

Shovelling
material into
hopper. Most
p a r t s of grinding machine
are enclosed,
b u t a slight
leakage with
visible
dust
escaping

Grinding room
of a n o t h e r factory

1,458

19.0

Most of material
is in t h e form
of clumps and
splashes.
Very
little soot.

Control

Tile
pressing
room, t a k e n a t
1.55 p.m., work
suspended since
1 o'clock

4,060

1.0

Great majority of
t h e particles are
s o o t ; other p a r t icles a p p a r e n t l y
mineral, up t o 4ft

Tile pressing

Same r o o m ;
sample taken
14-hour after
work was res u m e d after
dinner interval

3,530

1.8

Very m u c h less
soot t h a n in (3),
and great increase
in mineral p a r t icles.

TABLE

Process

Position

(1)

(2)

XXVI
Number Percentof parage
ticles
over
in 1 c.c.
2 f*

Remarks

(3)

(4)

(5)

Brushing biscuit tiles

Biscuit warehouse

2,265

1.9

A b o u t 20 % of the
particles are min e r a l ; there are
few aggregates.

Emptying
saggers a n d
looking over
biscuit tiles

Biscuit warehouse

2,181

0.9

A b o u t 20 % of t h e
particles are mineral.
General
characters similar to (6).

SILICOSIS IN GREAT BRITAIN

453

placing sand giving rise to dust in the biscuit warehouse when
the tiles are removed from the saggers and looked over and brushed.
This work is done by women and girls. Two samples were taken
in the biscuit warehouse (cf. table XXVI).
Two tile-sliphouse men were examined medically and radiologically; one of these showed evidence of silicosis after being
employed 25-30 years: in both workers a diagnosis of fibrosis of the
lungs was made. Three male tile-pressers were examined radiologically and all of these showed evidence of silicosis, the earliest
signs appearing after employment for 10-15 years. Six were
examined medically, and of these 3 showed evidence of bronchitis
and 2 of fibrosis of the lungs.
Nineteen female tile-pressers were examined medically and 5 also
radiologically. In one case, employed 25-30 years, silicosis was
diagnosed. Fibrosis of the lungs was found in 2 cases and bronchitis
in 1 case.
Of workers exposed to dust from the placing sand, 3 placers were
examined medically and radiologically.
One man employed
35-40 years showed evidence of fibrosis of the lungs, but there was
no evidence of silicosis in the group. One warehouse-woman was
examined medically, with negative result.
Of tile slabbers, who are exposed intermittently to the dust
of the finished tile, 3 were examined medically and radiologically;
all showed evidence of fibrosis of the lungs, but none of silicosis.
None of the men had been employed for more than 20 years.

Electrically ittings
These articles may be made from a body consisting simply of
ball clay, such as is used for stoneware articles, or from a composite
body which resembles that of earthenware but contains usually
only about 10 per cent, of flint. When the composite body is used
the articles are formed by pressure from the so-called dust which
contains about 15 per cent, of moisture (cf. table XXVII).

454

PAPERS PRESENTED TO THE CONFERENCE

Composite Body
TABLE XXVII

Process

Position

(1)

(2)

Number Percentoí parage
ticles
over
in 1 c.c.
2 (*
(3)
<4)

Remarks
(5)

2,422

4.8

About 50% of the
particles are mineral, most of
them in splashes,
refractive particles mixed with
clay.

Die-pressing
shop

1,976

3.2

Some aggregates
and splashes, accounting for most
of mineral particles: about 40%
mineral.

Between 2
dry fettlers

Fettling shop

1,855

1.7

Precision
grinding electrical fittings,
unglazed or
biscuit ware.
Without exhaust

Fettling shop

2,096

4.7

Most of the particles are in
splashes. About
40% mineral.
About 40% mineral ; most as
discrete particles.

Sieving damp
dust

Pressing

Stoneware Body
The articles are formed from plastic clay by pressure in moulds
which are previously dusted with fine flint in a cloth bag; no
obvious dust is produced in dusting the moulds (cf. table XXVIII).
TABLE

Process

Position

(1)

(2)

XXVIII
Number Percentof parage
ticles
over
in 1 c.c.
2 F

Remarks

(3)

(4)

(5)

Pressing small
articles in
moulds dusted with flint

Pressing shop

2,036

1.3

About 20% refractive particles ;
much of mineral
in splashes.

Wiping dry
dipped article
to remove
marks

Dipping house

2,097

4.2

About 50% of the
particles refractive.

SILICOSIS IN GREAT BRITAIN

455

Fifty-one workers exposed to dust of the composite body of
electrical fittings were examined medically and 21 radiologically.
One man employed as a turner for 35-40 years, and two women
employed as pressers for 20-25 years and 25-30 years respectively,
were found to show signs of silicosis.
Fibrosis of the lungs was diagnosed in 1 jiggerer, 2 turners,
3 sliphouse men and 4 female pressers. Two of these pressers and
1 sliphouse man showed evidence of bronchitis.
Of those exposed to the dust of placing sand, one placer was
examined and showed evidence of fibrosis of the lungs after
employment for 25-30 years.
Sanitary Ware
The body may be fireclay or a white body similar in composition
to that used for earthenware. The preliminary manipulation of
the ingredients for the white body involve exposure to the dust
of clay, Cornish stone and flint; while the processes of casting and
fettling involve exposure to dust of the mixed body, as in the case
of earthenware (cf. table XXIX).
It would not be possible to make a differential count of the highly
refractive and other particles with polarised light, because of the
illumination of the clay particles. This is one example, like that
found in the manufacture of firebricks, of the effect of clays in
fixing free silica particles in the atmosphere, and not within the
lungs, and probably explains the diminished power of free silica to
produce silicosis in the presence of clays, though the dust may be
capable of producing other forms of respiratory disease and even
fibrosis of the lungs x (cf. table XXX).
TABLE

Process

Position

(1)

(2)

XXIX

Number Percentof parage
over
ticles
2 fin 1 c.c.

Remarks

(3)

(4)

(5)

Shovelling

Cornish stone
drying beds

662

7.1

Splashes and some
large refractive
particles up to
16 (i.

Wheeling flint
on to weigh
machine

Slip making and
weighing house

976

3.7

About 50% refractive material.

Cf. Bibliography, No. (10).

456

PAPERS PRESENTED TO THE CONFERENCE

TABLE

xxix (continued)

Process

Position

(1)

(2)

Loading
charges of
ground flint.
Shovelling
d a m p flint

Sandpapering
and brushing
s a n i t a r y fitting.

Number Percentof parage
ticles
over
in i ce.
2 (*
(3)
(4)

Remarks
(5)

1,180

0.7

A b o u t 8 0 % of
particles are
clear (flint).

Sanitary ware
casting shop

1,771

8.8

A dense sample
owing to large
n u m b e r of
splashes.

Dry fettling

do.

1,000

3.2

Most of mineral
matter in splashes.
Discrete mineral
particles form
u n d e r 5 0 % of
other free particles.

Do.

do.

964

2.5

A b o u t 3 0 % of
particles refractive; others soot.
A few splashes.

Sweeping
floor

do.

1,674

11.7

Most of mineral
m a t t e r in form of
splashes. Highly
refractive particles standing out
from surrounding
debris ; these are
probably flint.

TABLE
Process
(D

Position
(2)

Sandpapering
and brushing
biscuit sanita r y ware

Stopping warehouse

Enamelling
fireclay

Enamelled fireclay brushing
department.
Workers stopped for dinner
5 minutes before sample was
taken

XXX
Number
of particles
in 1 c.c.
(3)

Percentage
over
2 (*
(4)

Remarks
(5)

554

A b o u t 8 0 % of
particles are discrete and r a t h e r
coarse. Particles
generally highly
refractive.

1,036

4.2

The larger particles and most of
small ones are
clear a n d refractive.

SILICOSIS IN GREAT BRITAIN

457

Thirteen sanitary casters were examined medically and 10 of
these also radiologically. All of these had been employed previously
as sanitary pressers and some also as earthenware hollow-ware
pressers. Silicosis was diagnosed in 4 cases; fibrosis of the lungs
in 7, and bronchitis in 3. Of sanitary pressers 7 were examined
medically and 5 also radiologically. Silicosis was diagnosed in
2 cases after employment in this occupation for 25-30 years and
previous employment as earthenware hollow-ware pressers. Five
were found to show evidence of fibrosis of the lungs and 2 of
bronchitis.
Of workers in sanitary ware exposed to dust from placing sand,
1 placer employed 25-30 years, was examined medically and
radiologically, and fibrosis of the lungs was diagnosed. Two biscuit
warehouse-women were examined medically, one of them also
radiologically, with negative results: they had been employed for
18 and 20 years respectively.

Stoneware
The manufacture of stoneware is not regarded as part of the
pottery industry in the ordinary sense. The trade is not carried
on in North Staffordshire but is scattered throughout the country,
especially in Scotland, and the workers are not members of the
Pottery Workers' Trade Unions. The articles made include jam
jars, stone bottles, teapots, spirit and chemical jars, electrical
fittings, etc. The body consists entirely of ball clay made plastic
by milling with water. Flint is present in the glaze and in the
sagger wash (cf. table XXXI).
Polishing
The processes of polishing are carried out for the purpose of
removing blemishes and thimble marks from the glazed ware.
In general, the processes consist of abrasion by a rapidly revolving
wheel or brush to which is applied finely powdered flint mixed with
water; or the wheel itself is constructed of an artificial abrasive
and flint is not used. The wheel or brush rotates in a direction
downwards towards the operator. Close application of the worker
is necessary. In some polishing shops localised exhaust draught is

458

PAPERS PRESENTED TO THE

CONFERENCE

TABLE XXXI

Process

Position

(1)

(2)

Number Percentof parage
ticles
over
in i ce.
2 f*
(3)

(4)

Remarks
(5)

1. Drying stoves
with revolving carriers

Jolly shop

723

10.0

About 50% of
particles are mineral ; others
soot.

Working at
lathes ; ware
carriers passing to and
from room

Turning shop

735

Character of
sample similar to
(1) but larger
masses present,
up to 16 u, and a
higher proportion.

Jollying

Jolly shop

1,385

2.9

Few discrete mineral particles ;
most of mineral
matter occurs in
splashes. Soot
also present.

Jollying jam
jars

Jolly shop —
another factory

1,964

1.0

Mineral matter in
splashes with refractive particles
embedded, and
as discrete particles which form
about 10% of
count.

Turning jam
jars

Turning shop

1,844

2.8

Splashes which
include refractive particles. Discrete refractive
particles form
about 10%.

Dipping artticles for glazing

Dipping house

Sample taken
showed no evidence of danger
from liberation
of flint particles
from glaze into
atmosphere.

Note. — Stoneware was not included in the branches of the industries in which medical
and radiological examinations were made.

459

SILICOSIS IN GREAT BRITAIN

provided for each polishing lathe; in others no localised exhaust
draught is provided. The dust from polishing consists of the abrasive thrown off by the wheel or brush; this is either flint or the
material of which the abrasive wheel is composed. Dust from the
ware will consist of fired glaze and is probably not important.
Four samples were taken in a large polishing shop in which
15 lathes were working. In this shop there is a system of localised
exhaust ventilation by which a current velocity, averaging
1,500 linear feet per minute at the openings of the ducts, is obtained,
and a total ventilation of 10 changes per hour of the air in the room.
The shop measures 70 X 37 X 11% feet with a cubic content of
approximately 30,000 cubic feet (cf. table XXXII).

TABLE

Process

Position

(1)

(2)

XXXII

Number Percentof parage
ticles
over
in 1 c.c. 2 ¡i

Remarks

(3)

(4)

(5)

1. Polishing with
flint on a revolving brush

Polishing shop

2,446

10.0

Refractive particles vary in size
from 6 ¡i down to
under 1¡¿, and
form about 50%
of count.

Polishing on
an alundum
wheel, without
flint

Polishing shop

1,337

3.3

Refractive particles form about
20%; otherssoot.

Polishing on
a mica wheel,
with flint

Polishing shop

1,687

2.6

Refractive particles not numerous, about 10%

Polishing on
a cork wheel,
with flint

Polishing shop

1,952

1.0

Refractive particles form about
10%.

At a china polishing shop in another factory 4 samples were
taken; in this polishing shop there is no localised exhaust
ventilation; the room is much smaller than in the above-mentioned
polishing shop, and only 4 lathes were in use (cf. table XXXIII).

460

PAPERS PRESENTED TO THE

TABLE

Process

Position

CONFERENCE

XXXIII

Number Percentage
of parover
ticles
2 (*
in 1 c.c.

Remarks

(2)

(3)

(4)

(5)

Polishing dish
on cork wheel
with flint

Polishing shop

2,265

8.8

A large proportion of particles
are refractive.

Bufling dinner
plate with
brush, flint
being applied

Polishing shop

1,988

13.3

Characters similar
to (5), b u t large
proportion of
clumps.

' Scaring ' an
alundum
wheel

Polishing shop

4,145

10.3

G r e a t majority of
particles refractive.

Control ; general air of
polishing shop

2,205

3.3

A b o u t half
of
particles refractive; others soot

yards from
nearest working lathe

Two samples were taken in an earthenware polishing shop in
which there is no localised exhaust draught (cf. table XXXIV).
TABLE xxxiv

Process

Position

(1)

(2)

Number Percentof parage
over
ticles
in 1 c e .
2 f*

Remarks

(3)

(4)

(5)

Polishing on
cork wheel,
with flint

Polishing shop

1,639

1.4

Between 3 0 % and
5 0 % of particles
are
refractive,
a p p a r e n t l y flint,
discrete,
with
few aggregates

10. Polishing a
large surface
with flint on
cork wheel

Polishing shop

2,157

3.3

Similar to (9) b u t
slightly
more
dense.

SILICOSIS IN GREAT BRITAIN

461

Fourteen polishers were examined medically and eight of these
also radiologically. Silicosis was diagnosed in a polisher of earthenware who had been employed for thirty-six years. Ten cases were
diagnosed of fibrosis of the lungs, and in one case there was some
evidence of tuberculosis.

Mould Making
A sample was taken at the breathing level of a mould maker
in a stoneware pottery, while mixing plaster of Paris with water ;
this process occupies about three minutes at intervals of fifteen
minutes throughout the working day. A flatware presser at
work in the same room.
The sample is very dense and cannot be counted owing to
crowding and overlapping of particles, and the presence of numerous
aggregates. The individual particles are of various shapes, but the
majority are of an elongated form with straight edges and right
angles : they vary in size from 14 p. down to the limit of visibility.
With polarised light the particles are diffusely luminous with here
and there a brilliant point.
A mould maker in Hanley, aged sixty-five, who had been
employed on plaster of Paris for fifty years, had no chest trouble and
did not know of any mould makers who had suffered from " potters'
asthma " ; he was subject to frequent colds from the open doors and
windows: he had had pneumonia three years ago and was laid
up for two months. There was no evidence of irritation of the upper
respiratory tract in the early period of employment or on resuming
after a holiday.
Thirteen mould makers were examined medically and three
of these also radiologically. Two cases of fibrosis of the lungs and
one of bronchitis were diagnosed, but silicosis was not found.

Evidence of Silicosis being Produced
In the Report by Drs. Sutherland and Bryson, already referred to,
the number of cases diagnosed as silicosis amongst the workers in
the pottery industry examined during the medical enquiry, was
given as 87 out of 250 examined radiologically.
The distribution in occupations is given in the following table:
i

462

PAPERS PRESENTED TO THE CONFERENCE

TABLE

XXXV

Males
Occupation

Females

Number Number Sili- Number Number SiliexamXcosis examXcosis
ined
rayed found
ined
rayed found

Millers
Slipmakers and dusthouse
attendants
Modellers
Mould makers
Throwers and lookers-to-ware
Turners and lathe treaders
Handlers
Plate makers and towers
Dish makers
Handbasin and chamber
makers
Saucer makers
Cup and bowl makers
Jiggerers and jolliers
Flat jiggerers and jolliers
(china)
Casters (earthenware and
china)
Sanitary casters
Hollow-ware pressers
Sanitary pressers
Tile pressers
Dust pressers (electrical)
Fettlers
Sagger makers and marl
grinders
Biscuit placers
Biscuit oddmen
Biscuit firemen
Biscuit warehouse
Glost placers and oddmen
Polishers and grinders
Tile slabbers
Labourers
Red marl workers

24
4
13
14
16
7
20
6

13
2
3
5
3
5
11
2

6
7
1
12

Totals

3
3

—
—

1
1
3
7
1

6
8
25
20
1

1
6

—

.—

—

4
9
19
4

13
13
17
7
6
2
2

6
9
11
5
3
2
1

4
4
6
2
3

22
48
12
5
4
9
14
3
9
8

9
33
7
1
2
3
9
3
4
4

344

182

—
—
—
—
3
5
4
1
1

—

—
—
—
•—
—
—
1

—
—'
.—.

2
1

—

—
—

—
—
—

—
—

19
17
11

8
7
3

1
2

3
17
2
1

—
—
—
—

•

—

—
—
—
—

.—.

1
1

—
—
—

—
—
—
—
—
11

—

—
—
—
—
—

224

—

SILICOSIS IN GREAT BRITAIN

465

Since the coming into force of the Various Industries (Silicosis)
Scheme, 1928, on 1 February 1929, fatal cases of silicosis, or at
least the majority of cases, occurring in the Potteries district of
Stoke-on-Trent, have been the subject of enquiry by His Majesty's
Coroner. The results of these enquiries, together with the results
of the post-mortem examinations, have come to the notice of the
Factory Department, and some particulars of these cases are given
in the following table.
TABLE XXXVI. — FATAL CASES OF SILICOSIS WHICH HAVE OCCURRED
SINCE FEBRUARY 1 9 2 9 , AND WHICH HAVE COME TO THE
NOTICE OF THE FACTORY DEPARTMENT
(The diagnosis has been verified by post-mortem
Branch
of
Industry

Process

Age

Period
of
employment

Period
of
symptoms

2 years

1. General
earthenware

Flint miller

Years
21

do.

Miller's
engineman
13 years
Miller 25 years

do.

Miller

A number
of years

do.

Period
of incapacity

Silicosis and
Tuberculosis

Bronchopneumonia
and silicosis

2 weeks

Bronchopneumonia
and silicosis

7 months

4 months

Silicosis and
tuberculosis

Silicosis

„

do.

Saucer m a k e r

do.

Plate maker

do.

Jiggerer

Jiggerer
Presser and
caster

63
58

53
48

3
4

2 months
2
„

P o t t e r s ' shop ]
30 years
1
Presser
|
10 years
J

6 years

do.

10.
do.
11. General
Earthenware
12.
do.

Cause
of
death

9 months

Sliphouse
labourer
33 years
Mill labourer
9 years
Boiler fireman a n d
potter's
oddman
29 years
Mill labourer
14 years
Dish maker

examination)

3 years

Few years

8-9

Several
years
7

„

10 days

„

1 Yt years
2 weeks

Lobar
pneumonia accelerated
by
silicosis
Broncho-pneumonia silicosis
and
chronic
bronchitis
Silicosis and
tuberculosis
Bronchopneumonia
and silicosis
Silicosis
Silicosis

Silicosis and
tuberculosis

Remarks

E x h a u s t applied
during 21 years
of employment.
Dust sample
showed 2,277
particles in l c . c ,
10% over 2 f*.
Silicosis diagnosed
when an X-ray
was taken for a
broken collar
bone.
Silicosis in second
stage.
Mill dusty and
exhaust was n o t
applied till a year
ago.

464

PAPERS PRESENTED TO THE CONFERENCE
TABLE

Branch
of
industry
13.

do.

14.

do.

15.

do.

16.
17.

do.
do.

18.

do.

19.

do.

20.
21.

Process

Presser and
caster
Flat presser
and
bowl
jollier
Hollow-ware
presser
do.
Hollow-ware
jollier

Period
of
Age employment
Years
47
33

xxxvi (continued)
Period
of
symptoms

Period
of incapacity

years 11 days

1 year

Silicosis and
tuberculosis

6 months

Silicosis

2 week
3 days

Silicosis
Bronchopneumonia
and silicosis

5 months

Silicosis and
tuberculosis

Silicosis and
tuberculosis
(haemoptysis)

51
53

41
40

A number
of years
1 year
2-3 years

Sweeper
of
floors In
potters'
shops
23 years
Biscuit placer
or in Potters'
shop

11 m o n t h s

do.

Glost placer

do.

G-lost placer

8 months

Polisher
Polisher
Polisher
Presser and
caster

56
44
57
53

46
27
40
38

6 years
2
„
5
„
9 months

'65

Some
years
Several
years
3 months

1 year

28. China

Presser'and
caster
Presser and
caster
Turner

„

29.

do.

Plate maker

4 years

„

30.

do.

Saucer maker

31.

do.

Sauce maker
39 i ears
Coal miner
5 years
Slag crusher
5 years
Sagger crusher
3 years
F l a t presser

1 year
2 months

2 years

„

22.
do.
23.
do.
24.
do.
25. Sanitary
earthenware
26.
do.
27.

do.

32.

do.

33.

do.

34. Tiles

34.

do.

35. Electrical
. flttings

Biscuit oddm a n (flint
siever)
Earthenware '
plate maker
5 years
Earthenware
biscuit
placer
4 years
Tile glost
warehouse
10 years
Dust tile
maker
15 years
Dust grinder '
7 years
Tile maker
24 years
Dust grinder

Cause
of
death

„

>»

1 Vi. years Silicosis and
tuberculosis
Silicosis and
tuberculosis
(haemoptysis)
3 weeks
Silicosis
1 week
Silicosis
1 Yi years Silicosis
9 months Silicosis and
tuberculosis

6 months

Silicosis and
tuberculosis
Silicosis and
tuberculosis
Silicosis and
tuberculosis
Bronchopneumonia
and silicosis
Silicosis and
tuberculosis

H a d not slept In
bed for 5 months
owing to dyspnoea.

W a s employed as
a s a n i t a r y eai t h enware placer
previously.
No signs of lead
poisoning.
No signs of lead
poisoning.

W o r k confined to
china body.

5 months

Silicosis and
tuberculosa

2
„

Silicosis and
tuberculosis
Bronchopneumonia
and silicosis

„

Silicosis and
tuberculosis

Employed in coal
mine 1 year.

9 days

Silicosis and
bronchitis

A coal miner In
South Wales up
to 20 years of age

Silicosis

7 months

Some years

„

Remarks

2 % year»

Silicosis

SILICOSIS IN GREAT BRITAIN

465

Methods of Prevention
The present Code of Regulations for the Manufacture of Pottery l
was made in January 1913, and applies to all factories and workshops in which the manufacture or decoration of pottery or any
process incidental thereto is carried on. For the purposes of the
Regulations certain processes and technical terms are defined and a
Schedule is appended, divided into two parts, Part I including
lead processes and Part II other processes. Evidence was taken
as to the working of the present Regulations by the Departmental
Committee on Compensation for Silicosis dealing with the Pottery
Industry 2 .
In making certain recommendations the Committee believed
that, except as regards the processes of fettling and china biscuit
emptying, their proposals did not go beyond what is already the
practice in some factories. So far as the Regulations are concerned
the processes dealt with may be grouped under three headings:
(1) those involving the use of powdered flint in the making of china
ware ; (2) certain processes carried on in potters' shops, and (3) other
processes such as flint milling, polishing, sorting, and grinding.
(1) Processes involving the use of powdered flint. — In these
processes the workers run the greatest danger of direct exposure
to silica dust. They include: the placing of china ware in saggers;
drawing of china biscuit oven and emptying of saggers; the process
of flat knocking and flint sifting; emptying the ware from baskets
and other receptacles, and scouring. The present Regulations
require the provision of exhaust draught for (2) the processes of
bedding and sifting (Regulation 7 (a) (vii)); (a) the removal of
bedded ware from the saggers after firing (Regulation 7 (/));
(c) flat knocking and fired flint sifting (Regulation 7 (g)), and (d)
scouring of biscuit ware which had been fired in powdered flint
(Regulation 7 (a) (ix)).
The Committee's recommendations were:
(a) China biscuit placing. — The requirement of exhaust draught
should be extended to include the " placing " of hollow-ware.
(b) Drawing of china biscuit ovens. — The requirement of exhaust
draught should be extended to the emptying of all saggers if powdered
flint has been used and not only to bedded flat ware.
(d) China scouring shops. — That exhaust draught should be
required for (i) emptying of biscuit ware which has been fired in
1
2

Cf. Bibliography, No. (3).
Cf. Bibliography, No. (4).
30

466

PAPERS PRESENTED TO THE

CONFERENCE

powdered flint from baskets or other receptacles, except where special
general ventilation is provided; (ii) filling and emptying of cradles
or other receptacles when ware has been fired in powdered flint.
Cleaning of floors in china biscuit placing and scouring shops. —
Regulation 12 (c) requires that the floors shall be impervious and
thoroughly sprinkled and swept at least once a day. The Committee
regarded the cleaning by vacuum as the most satisfactory method
and should be encouraged. Failing that, an efficient moist method
such as the use of damped sawdust.
(2) Certain processes carried out in potters'' shops. — The evidence
is that the dust in potters' shops arises mainly from two sources,
(a) dirty floors and benches, and (b) the process of fettling.
(a) Cleaning of floors and benches. — The Committee recommend
that an efficient moist method should be required as now recommended
for china biscuit "placing" and scouring shops, and that every encouragement be given to firms to provide impervious floors on the lines
suggested by the Research Committee of the National Council for the
Pottery Industry. They also recommend that provision of sufficient
accommodation be made for moulds and that arrangements should be
made that the moulds be returned to the store and not left lying about
the shop so as to impede the cleaning.
(b) Process of fettling. — Exhaust is at present required by Regulations for (1) fettling of flat ware by towing or sandpapering, with
certain exceptions; (2) any other process of fettling on a wheel driven
by mechanical power, except where (a) the fettler is fettling as an
occasional operation, (b) fettling is done wholly with a wet sponge,
or (c) fettling is done by the worker who has made the articles while
the latter are still in a moist state. The Committee recommended
that as the fettling of " white hard " ware is a very dusty process,
if done on any wheel, whether driven by mechanical power or not,
exhaust draught should be required for (i) all fettling of flat ware by
towing or sandpapering; (ii) any other process of fettling flat ware
except where (a) fettling is done with a wet sponge; (b) fettling is
done while the articles are still damp. They further recommended
that efficient exhaust draught should be required for all fettling of
hollow-ware and other ware not dealt with above, unless the articles
are so moist that no dust is given off.
Brushing of earthenware biscuit ware. — Efficient exhaust draught
is required for this process under Regulation 7 (a) (viii) unless it is
carried on in a room which has been certified by the Inspector of
Factories to be adequately provided with general mechanical or other
ventilation.
(3) Polishing, sorting, and grinding processes. — Exhaust
draught can be required for these processes under Regulation 7 (m),
but the Committee recommend t h a t a definite requirement for
exhaust draught be included in the Regulations.
The Committee recommended that in addition to those processes in
which protective clothing was already required under Regulation 4,
overalls and head coverings be required and worn by all workers

SILICOSIS IN GREAT BRITAIN

467

exposed to pure flint dust, and by young persons who carry scraps
from potters' shops, and that accommodation for depositing clothing
put off during working hours be required for all workers who are
required to wear overalls.
Recommendation was also made that Regulation 6 (a), which prohibits workers from taking meals or remaining during meal times in
certain rooms, should be extended to processes involving exposure to
flint dust, and that messroom accommodation be correspondingly
extended. Similarly, that Regulation 11, requiring washing accommodation, should be extended to include all persons whose occupations
exposed them to powdered flint.
Self

Inspection

The Home Office Committee of 1908 x pointed out that to ensure
satisfactory compliance with the Regulations, it is essential t h a t
every department of every factory should be under constant and
regular supervision, which should be organised from within the
factory. In accordance with their recommendations, Regulation 27
of the present Code requires the occupier of every factory to appoint
a person or persons whose duty it is to carry out systematic inspections of the working of the Regulations in the factory and generally
to enforce the observance of them. The evidence received by the
Committee showed that in some of the larger works the system has
resulted in considerable improvement.
In the smaller works,
however, equally satisfactory results do not appear to have been
achieved. It appeared that this was partly due to the appointment
of unsuitable persons and failure to allow sufficient time and
facilities for carrying out the work. The Committee considered that
the Regulations should be retained and should be more rigorously
enforced, and expressed the view t h a t conditions in potteries cannot
be adequately controlled without daily inspection, and provided
really suitable persons are appointed and given the whole-hearted
support of the employers and workers alike, the Regulations should
be invaluable.
Placing of China without Flint
The attention of the Committee was drawn to one or two practical
experiments carried out by firms with a view to the abolition of the
use of flint for china biscuit placing. In one case the setters for
settering china flat ware are coated with a patent wash. Another
firm have experimented satisfactorily with materials to take the
place of flint for all placing of china biscuit ware. It seemed t h a t it
1

Cf. Bibliography, No. (5).

468

PAPERS PRESENTED TO THE CONFERENCE

is within the range of possibility that at no distant date it may be
practicable to supersede the present method of firing china ware
in flint.
Compensation
Reference has already been made to the Report of the Departmental Committee on Compensation for Silicosis, dealing with the
Pottery Industry. The Committee felt that a scheme on the lines
of the Refractories Industries Scheme would have great advantages
in t h a t the interests of the employers and the workers could be
adequately safeguarded and t h a t in the long run it would prove
more economical to the industry as a whole. A scheme of compensation was suggested on the lines of the Refractories Industries
Compensation Scheme, but this was not given effect to. At present
compensation is provided for under the Various Industries (Silicosis)
Scheme, 1928 1, which came into force on 1 February 1929, and
applies to all workmen employed on or after 1 January 1929 in
the following processes in potteries:
(a) The milling of flint or crushing or grinding of silica rock or
dried quartzose sand.
(b) Any process in or incidental to the manufacture of china or
earthenware, including sanitary earthenware, electrical earthenware
and earthenware tiles, up to and including the preparation for glazing,
but excluding underglaze decorating, and modelling and mould making,
where these processes are carried on in separate rooms.
(c) The polishing, sorting or grinding on a power driven wheel in
connection with the grinding of glost ware, and tile slabbing.
The Scheme provides for compensation
disablement and death only.

in cases of

total

Bibliography
(1) Report on an Investigation of Atmospheric Dust in Pottery Workshops.
By H. OLIVER, B.SC.

(2) Report on the Incidence of Silicosis in the Pottery Industry. By Drs. C. L.
SUTHERLAND and S. BRYSON. His Majesty's Stationery Office. 1926. Price
Is. 6d.
(3) Regulations for the Manufacture and Decoration of Pottery. Statutory
Rules and Orders, 1913, No. 2. His Majesty's Stationery Office. Price 2d.
(4) Report of the Departmental Committee on Compensation for Silicosis
dealing with the Pottery Industry. His Majesty's Stationery Office, 1928.
Price Is. 3d.
(5) Report of the Departmental Committee on the Dangers attendant on the
Use of Lead and the danger of injury to health arising from Dust and other
1

Cf. Bibliography, No. (6).

SILICOSIS IN GREAT BRITAIN

469

Causes in the Manufacture of Earthenware and China. His Majesty's Stationery Office, 1910. Price Is. 5d.
(6) The Various Industries (Silicosis) Scheme, 1928. Statutory Rules and
Orders, 1928, No. 975. His Majesty's Stationery Office.
(7) Mineral (Non-Metallic) Dusts, the Manufacture of Pottery, etc. By
Dr. J. T. ARLIDGE. London, Royal Sanitary Institute, 1893.
(8)

" Phthisis in the Potteries. "

By Drs. J. MAGILL and J. B. MCDOUGALL.

Public Health, Aug. 1916.
(9) " Dust Counting in the Pottery Industry, with Special Reference to
Health Considerations. " By Dr. E. L. MIDDLETON. Transactions of the
Ceramic Society, Vol. XXIV, 1924-1925.
(10) " The Pulmonary Lesions produced by the Inhalation of Dust in
Guinea Pigs. " By H. M. CARLETON. Journal of Hygiene,Vol. XXII, No. 4,
p. 438. July 1924.

SANDBLASTING

Sandblasting is the process of projecting sand or other grit
by means of compressed air or steam against a surface. It is used :
(1) in metal works to remove adherent sand and irregularities from
castings and to produce a surface of desired quality ; (2) for etching
on glass.
The process is employed in many industrial centres throughout
the country.
Both sexes are employed on sandblasting small articles, but men
only on the heavier metal work. It is not possible to state the
numbers employed in the process, which is a small subsidiary of the
industries, but experience indicates that the process is receiving
increasingly wide application.
In metal working sandblasting is employed for cleaning castings
of all kinds and for producing a surface on the metal suitable for
subsequent treatment. In metal work instead of sand, chilled iron
shot, ground granite or flint may be used.
The article of metal may be placed in the open air and sprayed
with the abrasive from a nozzle. Usually with large articles the work
is done in an enclosed chamber, the worker being covered with
protective clothing and provided with a helmet with an independent
air supply. Small articles are done by adapting the process within
a smaller closed cabinet before which the worker stands, passing
his hands through guarded holes to direct the abrasive from the
nozzle, while watching the process through a glass panel in the
front of the cabinet.
In the etching of glass, the article is held against a stencil plate,
the abrasive reaching it through the stencil and being retained in
the machine by a suitable collar of rubber or other material. A

470

PAPERS PRESENTED TO THE CONFERENCE

cabinet such as that used for treatment of metal articles may be
used for glass.
The dust hazard in the cleaning of castings is from the moulding
sand and from the abrasive, where this is sand or siliceous grit
such as flint or granite. Where clean castings or other metal
articles are treated the danger is from the siliceous abrasive alone.
The sand, granite or flint, by repeated use in the machine, becomes
finely comminuted and fine dust escapes in spite of the precautions
required to be taken. Unwarrantable risks are incurred by workers
in faulty methods, such as opening the door of the hand cabinet
to look at or move the work, while the air within the cabinet is full
of fine dust, instead of allowing the exhaust draught time to act
before opening the door. In the large chambers the workers are
sometimes found to leave the door partly open, thus interfering
with the exhaust ; or they may remove the helmet while still working
in the dust laden air of the chamber.
Defects in the apparatus are bound to occur from time to time,
and the closest attention is necessary to detect and remedy leaks.
Even with the closest attention the process of sandblasting appears
to carry a serious danger of producing silicosis where siliceous
abrasive is used.
Five cases of silicosis, two of them fatal, have been brought to
the notice of the Factory Department since August 1928, and as
silicosis is not statutorily notifiable it may be presumed that other
cases may have occurred.
Particulars of the five cases are given below :

TABLE

Industry

Cycle
accessories

Sex

Male

Age

Years
40

Period of
employment
in
sandblasting

XXXVII

Process

20 years

Cabinet
type

„

? Chamber

do.

—

Cabinet

do.

Steel works

do.

Motor
accessories

Female

—

Male

12 m o n t h s

do.

7 '/2 years

do.

do.
Carburetters

Diagnosis

Silicosis

Silicosis and
tuberculosis
do.

Remarks

F a t a l . Radiogram shows
numerous dark nodules
over whole of both
lungs; no tuberculosis.
Diagnosis confirmed by
radiograph.
No
tuberculosis.
Occasional haemoptysis;
no other sign of tuberculosis.
F a t a l ; diagnosis confirmed by post-mortem.

SILICOSIS IN GREAT BRITAIN

471

Regulations for the Grinding of Metals (Miscellaneous Industries) 1
came into force on 1 November 1925, and they include Regulations
for sandblasting in the cleaning or smoothing of castings by a jet
of sand, metal shot or grit or other abrasive, propelled by a blast
of compressed air or steam.
The Regulations provide that: (1) sandblasting shall not be done
in any room except in an enclosed chamber or cabinet in which
no other work is ordinarily performed and at which efficient means
are provided to prevent escape of dust to the outside of the chamber
or cabinet. (2) No person may perform sandblasting in the open
air or work within 30 feet of such unless he is wearing a suitable
protective helmet and gauntlets ; during sandblasting in a chamber
overalls are also required. (3) The protective helmet must be
provided with a supply of pure air, means of escape for exhaust air,
and it must bear the mark of the person using it. (4) Before being
used by another person the helmet must be thoroughly disinfected.
The prevention of silicosis would best be attained by the use of a
non-siliceous abrasive such as metal grit, where possible. Some
manufacturers have adopted this line primarily with the health
of the worker in view.
Compensation
The Various Industries (Silicosis) Scheme, 1928, provides for
compensation in cases of total disablement and death of workmen
employed in foundries and metal works on " Sandblasting of metal
or articles of metal by means of compressed air and with the use
of quartzose sand or crushed silica rock or flint ".
Bibliography
(1) Regulations for the Grinding or Glazing of Metals, or processes incidental
to the Grinding of Metals or the Cleaning of Castings. Statutory Rules and
Orders, 1925, No. 904. His Majesty's Stationery Office. Price 2d.
(2) The Various Industries (Silicosis) Scheme, 1928. Statutory Rules and
Orders, 1928, No. 975. His Majesty's Stationery Office. Price 3d.
SILICA

MILLING

This industry is concerned with the grinding of silica rock,
crystal quartz or silica sand, all containing a very high.proportion,
usually about 98 per cent., of free silica. The silica-flour so produced
is used for many purposes, as the manufacture of scouring powders,
paint fillers, wood fillers, silica glass, and for foundry use.
1

Cf. Bibliography, No. (1).

472

PAPERS PRESENTED TO THE CONFERENCE

The rock, quartz or sand is quarried and dried (the rock is sometimes calcined) and crushed and ground by machinery to a fine
powder. In some works a system of exhaust draught is provided
over the crushing, grinding, sieving and conveying machinery and
the exhausted air is collected in filter bags, the finest powder being
collected in this way.
The industry is not extensive; it is distributed near the source
of the raw material, most being in the north-west of England.
A considerable amount of ground silica is imported from the
Continent and from America.
The amount of dust liberated in the processes is frequently
very great. At a silica grinding factory where the machinery
was enclosed and localised exhaust draught was provided, the
following atmospheric dust samples were taken with Owens'
dust-counter :
(1) Outside. Filling a truck with silica rock from a rail dump,
229 particles in 1 c.c, 2% over 2 p.
The wind disperses much of the dust here.
(2) Feeding the crusher with silica rock,
1,169 particles in 1 c.c, 11% over 2 ¡*.
(3) Same as (2).
1,385 particles in 1 c.c, 14% over 2 p.
(4) At a bagging shoot,
1,205 particles 1 c.c, 14% over 2 ¡i.
(5) Same as (4).
1,096 particles in 1 c.c, 14% over 2 ¡i.
At this factory, dust escaped from a number of slight defects
in the housings enclosing the machinery, as inevitably happens as
a result of vibration, and the escaping dust was seen to rise upward.
A dust sample taken on the staging above the tube mills, about
16 feet from the floor, gave:
4,061 particles in 1 c.c, 12% over 2 ¡t,
indicating a high concentration of dust.
At a working where vein quartz was obtained and crushed
to sizes from 1 / 8 to 1 inch, the following counts were made from
atmospheric dust samples taken at breathing level in some of the
processes.
(1) Hand drilling in the open; running water in the working,
15 particles in 1 c.c, 4% over 2(*.
(2) Feeding the crusher, wet,
168 particles in 1 c.c, 3% over 2¡i.
(3) Weighing " fines " (1/8 inch) in the open,
385 particles in 1 c.c, 10% over 2f».
(4) Bagging " fines ", in shelter of a shed,
2,301 particles in 1 c.c, 10% over 2 ¡t.

SILICOSIS IN GREAT BRITAIN

473

From the low counts, which include many fine particles, it appears
that work done in the open, on wet material, carries a low or
negligible risk. The weighing and bagging processes here did not
involve continous exposure. As the working was at a remote spot in
the hills, the counts may be regarded as free from extraneous dusts.
At a factory where pure quartz crystal is used, an atmospheric
dust sample at breathing level of a girl sieving quartz under exhaust
gave a count of
5,977 particles in 1 c.c, 10% over 2 f».

By rearranging the work this process was entirely enclosed and
the exposure of the worker to dust was obviated.
Evidence of Silicosis
One fatal case of silicosis with tuberculosis, the diagnosis
confirmed by post-mortem examination, occurred in a silica milling
factory. The man, aged fifty, had been employed for 3 % years up
to a period four months before his death.
Methods of prevention include the use of water where possible
and localised exhaust draught, especially when combined with
enclosure of the machinery.
Compensation
The Various Industries (Silicosis) Scheme, 1928, includes '
" breaking, crushing, grinding, sieving, mixing or packing of silica
rock, or of dried quartzose sand or any dry deposit or dry residue
of silica or any admixture containing such materials ; or any process
incidental thereto " ; and " handling or moving of silica rock, or
of dried quartzose sand or any dry deposit or dry residue of silica,
in or incidental to the processes mentioned in the foregoing
paragraphs ".
Bibliography
The Various Industries (Silicosis) Scheme, 1928. Statutory Rules and
Orders, 1928, No. 975. His Majesty's Stationery Onice.
PROCESSES IN WHICH GROUND SILICA IS USED

Silica enters into the composition of many industrial materials
in virtue of one or other of its properties, as abrasive, inert filler,
refractory material, insulator, or acid in vitreous bodies. In all the
processes where the silica, dry, and in a fine state of division, is

474

PAPERS PRESENTED TO THE CONFERENCE

liable to give off dust, the risk to health from its inhalation must
be assumed, since the conditions are comparable with those known
to produce silicosis in industries where its presence is found.
SCOURING POWDERS

Scouring powders are chiefly used as domestic abrasive cleansers.
The manufacture consists in mixing the abrasive, which may be
finely ground silica rock, or ground pumice, with other ingredients,
soda ash, powdered soap, etc:, and filling the mixture into cartons,
packets or bags. Sometimes the ground abrasive is packed without
admixture with any other substance.
Distribution
A considerable number of small undertakings were started,
frequently as a subsidiary branch of another business, in widely
scattered places over the country, in which the proprietors and
workers had little or no knowledge of the risk to health or the means
necessary for avoiding it.
Employed Persons
The number of employed persons fluctuates, but there are
probably less than 500 employed. Men are usually employed on
mixing machines, women and girls on packing.
The Processes
Except in a few of the largest works, the silica rock is obtained
already finely ground. It is usually a highly siliceous quartzite rock,
containing 96 to 98 per cent, free silica, and it may be calcined
before being ground. The silica flour, as it is called, is mixed with
powdered soda ash, soap, and sometimes other substances, either
by hand with a shovel, or in a mixing machine. Filling of the
cartons may also be done by hand, or the mixed powders may be
conveyed automatically to mechanical fillers; the lids are then
placed and fixed by a machine.
Characters of the Dust
The dust to which the workers are exposed is silica, before the
process of mixing and in packing where no other ingredient is added.
Frequently the silica is mixed with powdered soap, and with

475

SILICOSIS IN GREAT BRITAIN

carbonate of soda, and sometimes with gypsum, pumice, or other
substance. The mixed powders, necessarily kept dry, are liable
to give off dust in the mixing, conveying and filling machines. The
presence of free alkali with the silica dust may have an important
influence in producing injury to the lungs.
At one factory, that at which the fatal cases described later
were employed, atmospheric dust samples were taken at breathing
level of the workers, with Owens' dust-counter, with the following
results. The particles were nearly all colourless, of irregular shape,
and appeared to be derived from the process. No soot particles
are included in the counts.
TABLE XXXVIII

No.

Process

Number
of particles
in 1 c.c.

Emptying ground silica into the
mixing machine
Carton filling machine
Putting lids on cartons
Fixing lids by machine
Filling cartons by hand

1,048
1,193
891
735
590

2.
3.
4.
5.

Particles
over 2 f

11
20
16
6.5
18

Localised exhaust draught was provided at all the processes.
Evidence of Silicosis
In one factory in which about 22 persons were employed in the
manufacture of scouring powder, 4 deaths occurred within a
remarkably short space of time. There was some evidence that
4 other workers at the same factory who were said to have died of
pulmonary tuberculosis may have died from silicosis. These
workers were employed in the factory before localised exhaust
draught had been provided, when the employers were unaware
of the danger to which the workers were exposed.
Brief notes on the 4 cases on which post-mortem examinations
were made, are as follows :
Case I. — Died 16 June 1928, aged 19, female. Employed as a
carton filler from March 1924 until May 1928—4 7i» years. History
of pleurisy: December 1927, cough and pains in the chest, temperature 99.6° F. No tubercle bacilli in the sputum. X-ray examination
—appearance of miliary tuberculosis. Admitted to hospital 1 June
and died 16 June 1928.

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CONFERENCE

Post-mortem, showed poor general development, heart muscle soft
and flabby; air passages congested and contained muco-pus; adhesions
over the right pleura and fluid in the pleural cavity. The lungs were
of firm consistence and were covered with grey nodules whicù showed
a tendency to coalescence in the right lung. There were no cavities
and no necrotic areas as in pulmonary tuberculosis. The bronchial
and tracheal glands were enlarged, firm, grey, and not caseated.
Microscopic examination of the lungs showed dense nodules of
fibrous tissue, with areas of necrosis and chronic catarrhal inflammation, and a terminal inflammation at parts due to pneumococcus.
No tubercle bacilli were found in the lung, although prolonge-! search
was made. The glands were necrosed and what appeared to be a few
tubercle bacilli were found in them. Polarised light showed granules
in large numbers in the lung and chest glands.
Case II. — Died 4 June, 1928, aged 17 y2, female. Employed as
a carton filler from 9 October 1925 to 17 March 1928—2% years.
Since December 1927, she had complained of headache, nose Bleeding
and vomiting in the morning. She was treated for bronchial catarrh.
She went into hospital on 30 April 1928 with a diagnosis of pulmonary
tuberculosis. She suffered from dyspnoea. There was irregular
pyrexia. The sputum was repeatedly negative on examination for
tubercle bacilli.
Post-mortem examination: the findings closely resembled those
described in Case I. Microscopic examination of the lungs showed
numerous large fibrotic patches surrounded by a small cell infiltration,
and in the interstices were finely granular pigmented or black deposits.
The alveolar tissue was much reduced; the walls were thickened with
fibrous tissue and the alveoli were filled with albuminous exudate.
The general picture was that of chronic inflammation with fibrosis.
The glands appeared to be almost completely fibrosed. There was
no evidence of tuberculosis and tubercle bacilli were not seen.
Case III. — Female, aged 23. Employed from July 1919 to
November 1928. She was usually employed on wax polishes and occasionally worked overtime in the scouring powder department. She
would not work more than 6 hours in any week and for a few weeks
only in any year. This employment on scouring powder began about
1921. She was ill about six weeks with cough, loss of weight and loss
of appetite. Removed to hospital on 6 December and died on 3 January.
While in hospital the chief symptoms were cough and dyspnoea. The
sputum was scanty and was negative for tubercle bacilli at first, but
later was positive. This patient was X-rayed in June 1928, and the
film showed slight general diffuse fibrosis.
Post-mortem, the lungs showed the presence of silicosis and tuberculosis. In this case the silicosis was less advanced than in Case I.
Microscopic examination of the lungs and glands showed deposits of
silica revealed by polarised light.
Exposure to the dust of scouring powder over a period of 7 years
and was intermittent. This difference in the history of exposure from
Cases I and II appears to be of special interest in view of the differences
in the nature of the silicotic lesions in the lungs and also of the presence
of tuberculosis.
Case IV. — Male, aged 19, employed from February 1926 to April
1928. He was employed in the mixing room and on packing, about
equally. He first complained of cough in August 1927. Off work
five weeks. He was ill again in April 1928, and was treated in a

SILICOSIS IN GREAT BRITAIN

477

sanatorium. He went back to work for 9 weeks, but not on scouring
powder, the manufacture of which had been given up. He was admitted
to hospital on 28 January 1929 with open pulmonary tuberculosis,
pyrexia, and emaciation. He died on 27 December 1929.
Post-mortem examination: lungs showed tuberculous cavities in all
lobes. The remaining parts of the lungs were hard and contained a
large number of hard nodules the size of a pea. Glands at the roots
of the lungs were enlarged and very hard.
Microscopic examination of the lung showed chronic tuberculosis.
The gland showed much fibrosis with patchy distribution of yellowish
brown granular material, suggesting silicosis. In this case the silicotic
process appeared to be present in the lungs in an early stage.
Prevention
Suppression of dust in the processes of mixing and filling are
by no means easy. Even with exhaust draught, the powders, owing
to dryness and fineness, are liable to liberate dust. Success appears
to be best attained by making use of mechanical methods to the
utmost extent, enclosing the machinery and applying exhaust
draught to the housings so as to maintain an inward directional
air current, and to all points where feeding or discharging takes
place and dust is liable to be liberated.
Compensation
The Various Industries (Silicosis) Scheme, 1928, applies to
workmen employed in certain specified processes which include
sieving, mixing or packing of silica rock, or of dried quartzose sand
or any dry deposit or dry residue of silica or any admixture containing such materials; or any process ancillary thereto; and to the
handling or moving of these materials in or incidental to the
processes mentioned.
The Scheme provides for payment of compensation in cases
of total disablement or death from silicosis or silicosis accompanied
by tuberculosis.
Bibliography
The Various Industries (Silicosis) Scheme, 1928. Statutory Rules and
Orders, 1928, No. 975. His Majesty's Stationery Office.
FLINT

CRUSHING

Apart from the milling of flint for use in pottery manufacture,
flints are crushed for poultry grit and for grit for sandblasting,
and sandpapers. The industry is a small one, employing few persons,
and is carried on chiefly in the south of England.

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The flints are broken in a stone crusher, passed through rotary
sieves and sorted into required sizes. The processes are usually
carried on in open sheds and localised exhaust draught is provided
at the points where dust is produced.
The dust is of raw (uncalcined) flint and the amount produced
would undoubtedly involve risk of silicosis, but in most of the
processes there is no constant exposure or close application of the
workers, and the open character of most of the works buildings
allows of the free action of wind.
In this, as in all the silica industries, the actual danger cannot
be assessed, as silicosis is not a reportable disease under the Factory
and Workshop Acts. As many of the processes belong to ill-defined
industries, the labour turnover is considerable and the nature of a
man's employment may be lost sight of should he develop symptoms
and signs of silicosis some years after he has left it.
FLINT KNAPPING

The making of flints for flint-lock guns or pistols. This ancient
industry is confined to the village of Brandon in Suffolk. It was
investigated by Dr. E. L. Collis in 1911.
The numbers employed have steadily diminished in the last
fifty years. In 1911 about 12 men, and in 1929, 5 men only were
employed, and these not constantly owing to fluctuations in the
demand.
The interest of this industry lies in its antiquity and the fact that
it is a pointer to, if not a measure of, the danger of inhalation of
flint dust—almost pure silica—carried on in small workshops in
rural surroundings and therefore unaccompanied by the other
industrial hazards so frequently met with in silicosis producing
occupations.
The process consists of splitting flints with a hand hammer into
pieces about 1 by 3/4 inch in size, flat on one side and with bevelled
edges on the other side, the faces showing the typical conchoidal
fracture of flint. The flints are packed in small sacks of 200 and are
exported for bartering with natives of Africa. The hammer blows
fall on the flint with remarkable rapidity and with each blow a small,
scarcely perceptible, cloud of fine dust is liberated.
Two samples of atmospheric dust were taken at breathing
level of two men knapping flints. The counts gave 1,313 and
1,192 particles in 1 c.c, with 1.4 and 2 per cent, particles over
2 p. respectively. Most of the particles were under 1 p. in size. Some

SILICOSIS IN GREAT BRITAIN

479

dust is liberated when the work benches are cleared of debris,
but mixed with this dust is chalk from the outside of the flints.
The evidence of silicosis being produced is, at present, entirely
statistical. From data provided by the Registrar-General's Department, Collis reported 27 deaths during the twenty-five years
1886-1910. Of these, 21 were from phthisis, 2 from other respiratory
disease, and 4 from other causes. The average age at death of the
21 who died from phthisis was 42.3 years. The death rate was
41.0 per 1,000 living compared with 0.8 for the Brandon Rural
district and 1.58 for all males, England and Wales, for the same
period.
Methods of Prevention
As the workers maintain that the flint must be dry for proper
working, water cannot be employed. Localised exhaust draught
would be too costly for this decadent and precarious industry in
which no mechanical power is used. Respirators, standardised to
protect against this very fine dust, would be difficult to attain, but
at least partial protection might be afforded in this way, and,
together with the intermittency of the work and the possibility
of working in the open air, as is done in summer, sufficient relief
from exposure might be attained to carry the worker through his
life without a disabling degree of silicosis.
Compensation
The Various Industries (Silicosis) Scheme, 1928, covers the
breaking of flint. Probably there is no one employed in this
industry at present who comes within the definition of " workman "
in the Workmen's Compensation Act, 1925.
Bibliography
The Various Industries (Silicosis) Scheme, 1928. Statutory Rules and
Orders, 1928. No. 975. His Majesty's Stationery Office.
MILLSTONE

DRESSING

This is an occupation in which a comparatively small number
of persons are employed. It consists in dressing the millstones for
the grinding of corn in distilleries, corn and fodder mills, and for
grinding chocolate in chocolate factories.
The process is carried on in many districts throughout the country,
where the mills exist.

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The persons employed may be specially skilled men who have
learned the trade and are solely employed on the process, or the
work may be done as a part-time occupation.
The corn mills consist of two circular stones placed horizontally.
They may be composed of any hard stone but are usually a hard
quartzite grit, chert or buhrstone—a chalcedonic form of silica—
or artificial stones. Dressing of the stones is done with an adzeshaped steel tool, by chipping along the ridges which run radially
from the centre. During chipping a slight cloud of fine dust rises.
Two cases of death from silicosis and tuberculosis in millstone
dressers have come to the knowledge of the Factory Department
recently. The first case was of a man, aged fifty-four, employed as a
cornmillers' stone-dresser since boyhood, with the exception of a
few years in the Army in early manhood. Eight months before his
death he gave up work on account of dyspnoea and loss of weight.
X-ray examination showed silicosis and tuberculosis.
Post-mortem examination confirmed the diagnosis. There were
besides the tuberculous lesions, innumerable nodules of silicotic
fibrosis confirmed by microscopic examination.
The stones dressed by this man were 90 per cent. Derbyshire
silica rock, the remainder French buhrstone.
The second case was a man who died, aged thirty, from silicosis
and tuberculosis, but no post-mortem examination was made.
He was constantly employed from boyhood on dressing Derbyshire
millstones in a corn mill. He became totally disabled by the
disease, six months before his death.
Prevention of inhalation of dust in the process could be achieved
by the provision of localised exhaust draught, but this would have
to be by a flexible duct so that the hood could be moved during the
process of chipping the stone which remains in situ.
Compensation
The Various Industries (Silicosis) Scheme, 1928, applies to
workmen employed in " sawing, planing, dressing, shaping, cutting,
or carving of silica rock ". For the purposes of the Scheme silica
rock includes quartz, quartzite, ganister, sandstone, gritstone
and chert.
Bibliography
The Various Industries (Silicosis) Scheme, 1928.
Orders, 1928, No. 975. H.M. Stationery Office.

Statutory Rules and

PNEUMOCONIOSIS

ITALY

BY PROFESSOR GIOVANNI LORIGA,
CHIEF MEDICAL INSPECTOR

OF FACTORIES

FOR

ITALY

Italian research workers have furnished several interesting
contributions to the knowledge of respiratory diseases due to the
inhalation of dust. This is proved by the bibliography on the
subject, which during the last twenty-five years has enriched
knowledge of this question and which comprises numerous studies
and results of experimental research on the pathological action of
dusts, numerous clinical observations on diseases of the respiratory
system met with in workers engaged in dusty operations of various
kinds, as well as accurate investigations into the health conditions
of special groups of workers exposed to forms of pneumoconiosis.
In addition, however, other references to pulmonary diseases of
these workers are frequently to be found in other books and
monographs.
Nevertheless, it must be recognised that the study of these
disease forms has not been so extended or profound in Italy as in
certain other countries, especially the Anglo-Saxon countries and
Germany. The scarcity of contributions by Italian scientists is
evident, in particular, in regard to that form of pneumoconiosis
which accompanies mining or operations connected with stone or
clay, and which has been fully studied in other countries under the
designation of " miners' phthisis ".
In seeking the cause of this phenomenon, it is not, in our opinion,
possible to plead either the limited number of workers engaged
in dusty operations in our mines, quarries or other places in which
stone or clay is manipulated, or the temporary character of most
work of this kind (such as, for instance, in the case of workers
31

482

PAPERS PRESENTED TO THE CONFERENCE

engaged in the excavation of railway tunnels or in the paving of
streets), or hygienic conditions superior to those in other regions,
or again the instability of most of the workers in question who,
as is well known, quit work very readily in the dusty trades and
immediately find other occupations. Further, in Italy, analogous
conditions and inconveniences are found in similar occupations,
hardly differing at all from those attaching to the corresponding
work in other countries.
It is almost certain, on the other hand, that the reason why
Italian medical bibliography on the subject is not so rich as that
of the other countries above referred to should be sought in the
small number of workers affected by miner's phthisis who come
under medical observation, and especially in the fact that it is
a question of isolated cases, or rather that pneumoconiosis does
not assume the character of a mass infection or a focal disease,
and that therefore it is not strictly related to a given locality or
to a certain quality of material, as would appear to be the case
in other countries.
It is, however, very probable that the limited extension and the
less serious nature of the cases depend on the fact that in our
country the composition of the minerals extracted or worked
presents a relative poverty of siliceous material.
It is well known, in fact, amongst medical men that the most
dangerous mineral dusts are those of a siliceous nature, since the
presence of silicic acid gives to the dust particles greater hardness
and a remarkable irregularity of form by means of which their
surface becomes very rough, sharp and cutting and they are therefore rendered capable, not only of considerable injury to the tissues,
but also of remaining insoluble amongst these. Recent studies,
the conclusions of which have been confirmed by the Papers
presented by Mavrogordato and Irvine to the fourth meeting of the
Permanent International Committee for the Study of Occupational
Diseases (Lyons, April 1929), and have given support to the older
statements of Weigmann and of Lubenau, lead to the belief that
the most harmful dusts are those containing siliceous oxides
(Si0 2 = silicic anhydride or bioxide of silicon). To this category
belong quartz dusts and those of its various forms (rock crystal,
agate, amethyst, chalcedony, jasper, onyx, opal) as well as siliceous
sand, fossil dust, granite and sandstone.
There would, on the other hand, be considered in the second place,
that is, as of average harmfulness, the silicates, those of the heavy
metals: for instance, silicates of copper (malachite and azurite)

PNEUMOCONIOSIS IN ITALY

483

and of zinc (calamine) or others variously mixed with other clays
(asbestos, mica, slate, kaolin, cement).
Besides the poverty in silica of the mineral deposits, there must,
however, be kept in mind, in our opinion, other factors concurring
to augment or diminish the pathogenic capacity of all the dusts,
especially when the disease attacks large groups of workers, and
when the conditions in question vary greatly in different localities.
Such conditions are in the first instance those relative to the
hygienic conditions obtaining in the workers' homes and in the
workplaces, and secondly, the duration of exposure of the worker
to the action of the dust.
Nevertheless, it is not difficult to recognise that many of those
who insist on a special and extraordinary gravity of silicosis have
overlooked almost entirely this influence, whilst they have attributed great importance to the physical properties of the dusts
inhaled, when engaged in research for the causes thereof or in
research relative to the pathogenic interpretation of the pneumoconiosis described by them. We suspect, on the other hand,
that such information may play a role which will become preponderant when the study of the disease has been completed by
enquiry into the physical and social environmental conditions.
We do not desire thereby to deny that more serious pulmonary
diseases and also perhaps more rapidly developing forms are
caused by siliceous dust, but we only wish to insist on the fact
that in the first instance we cannot recognise any specific character
in their pathogenic action, such as certain authors desire to do,
some of whom have almost made of silicosis a separate disease
to be distinguished from the general pathological picture of
pneumoconiosis, presupposing even a hypothetical chemical or
chemicotactic influence exercised by the above-mentioned dusts
on the lymphatics and other cellular elements.
It seems to us that this aspect of the problem may be highly
interesting, but requires to be still further investigated and cleared
up by means of accurate experimental research, since the statement has so far not been supported by sufficiently convincing
proof.
Secondly, we must make certain reservations in regard to the
specific nature of the supposed cause which imparts to silicosis
the particular character of a focal disease or a mass disease, such
as it has assumed in some countries, and therefore also in regard
to the applicability of preventive and social measures edicted by
the legislation in Anglo-Saxon countries and in Germany, to

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other countries in which the disease above referred to does not
present the same characteristics relative to its incidence and
clinical gravity.
Obviously, in order to form a rational criterion in regard to
this special aspect of the question, it would be advisable to take
into consideration the other causative elements, mention of
which has been made, and which seem to us of primary pathogenic
importance, especially the following:
(a) The social and hygienic conditions under which the work
is carried out, whether relative to the working conditions
and to the means of prevention and protection against
dust inhalation or to the welfare conditions of the workers,
which are of such great importance in determining their
physical resistance to disease in general and to pulmonary
affections in particular.
(b) The intervention of the infectious tubercular factor. This
factor constitutes in fact such a frequent complication as
to leave the doctor almost constantly in doubt in regard
to the gravity of the pneumoconiosis considered as a
separate disease, since we do not yet possess sufficient
criteria to enable us to effect a differential clinical diagnosis
between dust phthisis and tubercular phthisis during the
life of the patient, when the presence of the Koch bacillus
in the sputum is lacking.
Another cause of doubt has recently been removed by the
anatomo-pathological observations made by Mavrogordato, from
which it would result that the large mononuclear endothelial
cells, after phagocyting the grain of silica, are not destroyed, but
thus conserve their vitality and acquire besides the capacity of
assembling and forming pseudo-tubercles.
This observation evidently creates another remarkable difficulty
in regard to the differential diagnosis between the two diseases,
also on the anatomo-pathological side, so much the more so as
the same author recognises that all the fatal cases of miners'
phthisis at present encountered in the Witwatersrand are manifestly cases of tuberculosis. How is it possible to determine, we
ask, the moment at which the siliceous granulation stops and the
tubercular process commences, and how is it possible to distinguish
the one from the other by clinical and radiological examination
and perhaps also by anatomo-pathological examination ?

PNEUMOCONIOSIS IN ITALY

485

No one can but see how far these two facts—that is to say,
the formation of granules due to silica, and, on the other hand,
the total mortality due to tuberculosis—diminish the great importance attributed by some research students to miners' phthisis as
a special clinical disease, considered capable not only of causing
death to certain workers but of creating a very serious mass
pathology.
In the Latin countries, as mentioned by the eminent research
workers, Professor Martin, of Lyons, and Dr. Glibert, of Brussels,
the various and complex symptomatology attributed to miners'
phthisis in Anglo-Saxon countries and in Germany is practically
unknown, and it would therefore be advisable to engage in a
detailed study of silicosis and the other forms of pneumoconiosis
in our countries also.
With the precise intention of collaborating as far as possible in
developing the knowledge of this most important problem of
occupational pathology, which affects the great mass of workers,
there have been undertaken in Italy, since the Lyons Congress,
certain researches into the pathology of workers in the slate,
asbestos and marble industries, the results of which will be communicated to the Johannesburg Conference.
In this preliminary paper, it is intended merely to set forth the
present-day state of the pneumoconiosis problem in general in
our country as derived from laboratory experiments, clinical,
anatomical and statistical data assembled from various research
workers who have dealt with the question, or from special investigations covering certain working establishments.
Without going back to the clinical and anatomical observations
made by Ramazzini, Morgagni and other authors in past centuries,
it is easy to affirm that the study of disease due to dust affecting
the respiratory organs has not been neglected in the revival of
interest in the subject of occupational disease to which our research
workers have testified about the year 1900. Many publications have
been devoted to the study of general questions relative to pneumoconiosis. Others deal in particular with the pathogenic action of
certain qualities of dust.
In the experimental field there should be recalled in the first
instance the researches of Biondi (1906), who, by making animals
inhale metallic dusts collected in the workings of the Sardinian
mines, succeeded in producing in them more or less diffused
bronchitis and small foci of bronchial pneumonia.
He carried out, moreover, experiments by means of the ingestion

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of inert dusts (non-metallic) and noted that these also produced
a form of pneumoconiosis, but that grains of dust were not found,
as in the case of pneumoconiosis, from inhalation in the bronchial
tube and in the alveolar cavities, but only in the inter-lobular and
inter-alveolar tissues and in the tissues between the inter-alveolar
groups. Soon thereafter in order of time (1907) there appeared
the study by Tommasi-Crudeli, chiefly anatomo-pathological in
character, entitled " Destiny of the Dust Introduced into the
Lung ". Feliziani (1906) and Romby (1908) directed their experimental researches to the study of the intestinal origin of pulmonary
anthracosis, the first denying, and the second affirming the possibility, in confirmation of the observations made by Biondi.
The question of pneumoconiosis was moreover discussed by
Ruata in 1908.
Guerra-Coppioli, in 1911, resumed the question of the intestinal
origin of anthracosis, arriving at a negative conclusion and asserting,
on the other hand, that the lymphatic ganglia of the mesentery
constitute an almost insurmountable obstacle to the small corpuscles
coming from the intestine with the lymphatic current.
The report of Devoto and Cesa-Bianchi to the third National
Congress for Occupational Diseases (Turin, 1911) must be considered
as a complete survey of the whole question relative to the pulmonary
pathology of dust inhalation. These authors have emphasised the
difficulty of provoking pathological phenomena in the respiratory
apparatus in the case of guinea-pigs kept for eight to ten weeks
and four to six hours per day in a very dusty atmosphere, and
the facility, on the other hand, with which these arise as soon as
the guinea-pigs are forced to exercise mouth breathing by closing
the two nostrils or even one nostril. They have besides found
alveolar lesions on microscopic examination of guinea-pigs which
had inhaled cement. They have moreover studied the relation
between pneumoconiosis and tuberculosis, asserting that the
animals subjected to the inhalation of very fine limestone dust are
less susceptible to tuberculosis than those which have inhaled
silica dust.
In the same year, Moscati had stated at the Congress of Physiology that the prolonged experimental inhalation of starch dust was
capable of producing evident connective peri-bronchial and subpleural sclerosis, though of a mild form. He saw, however, that
the grains of flour undergo in the lung notable modifications which
may presumably be interpreted as phenomena of hydrolysis or
ptyalin digestion and finally become absorbed.

PNEUMOCONIOSIS IN ITALY

487

Tedeschi and Abbo have produced experimentally serious
phlogistic processes of the respiratory organs of guinea-pigs by
making them inhale for some time dust collected in grain silos
(1914).
Recently Aiello has demonstrated that phrenicotomy favours the
production of pneumoconiosis in animals subjected to dust inhalation (1929). Recently again Mazzitelli (1929) has felt justified in
stating on the basis of some of his experiments that inhaled marble
dust is subject, though only in part, to evident processes of
transformation, absorption and elimination, whilst Bianchi has
affirmed that it causes evident processes of reaction and inflammation in the lung.
As an offset to this important series of research contributions,
numerous other studies of a clinical and anatomo-pathological
character exist which have furnished important information on
the œtiology and pathogenesis of the pulmonary diseases derived
from dust.
There should be recalled in this connection the interesting
studies of Devoto on the relations between pneumoconiosis and
catarrh of the pulmonary apical zones (1913), on the non-tubercular
lesions of the pulmonary apex (1914), on the relations between
pulmonary affections due to dust and tuberculosis of the lung
(1925) and on pneumoconiosis in its initial stages (1925).
Tedeschi also has described special non-tubercular lesions of the
pulmonary apex (1914).
Highly interesting are, moreover, the histological and chemical
researches of Boattini and Lo Faso on the essence of pulmonary
anthracosis (1928), from which the said authors have drawn the
conclusion that the particular colouring of the anthracotic lung
is certainly due in part to the presence of iron, but that this fact
does not afford justification for substituting siderosis for the
conception of anthracosis, and that the anatomical and pathogenic conception of pulmonary anthracosis should not be in any
way modified.
Ferrannini has measured the respiratory capacity of individuals
engaged for many years in bagging flour, and who were decidedly
free from tuberculosis (1911). In about half of these he found
the pulmonary capacity to be more or less markedly reduced,
that is to say, an indication of diminution of the respiratory surface
due to encumbrance of the pulmonary alveoli. He was able,
moreover, to demonstrate the presence of starch in the sputum
of a few individuals, not microscopically but chemically, and also

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found there albumen, which he supposes to be derived from the
gluten in the flour.
Another work of great importance has been completed by
Bonanno (1928), who has studied from the clinical and radiological
aspect eighteen cases of pulmonary silicosis in miners from the
South African gold mines.
Meda also has completed some observations on the radiological
picture of pneumoconiosis (1927). A few isolated cases of pneumoconiosis produced by different dusts are worthy of special
attention.
Devoto and Cesa-Bianchi have reported the case of a glove
maker, who during life had suffered from chronic bronchial catarrh
and who, having died as a result of inter-current nephritis, showed
during the pathological macro- and microscopical examination
pneumoconiosis due to talc powder.
Ferrannini has studied a case of pneumoconiosis from cement,
characterised by asthma and pulmonary emphysema in an individual
whose occupation was handling cement (1928). His pupil, Sorrentini, had described a case of pneumoconiosis from flour (1923).
Fiori has moreover published particulars of a rare case of pneumoconiosis due to barium (1926).
Quite as numerous, and perhaps more interesting from the point
of view of the discussions likely to take place in the international
field in regard to dust pathology, are studies effected relative to
the health conditions of groups of workers engaged in various
dusty trades.
It would seem advisable to summarise rather fully the results
of these investigations, since in them, rather than in clinical or
anatomical findings pertaining to single individuals and laboratory
experiments, we are likely to find elements useful in resolving
the problems connected with the study of silicosis.
In a great many publications of various natures, clear indications
are given not only of the incidence of the disease in question,
but also of the high mortality rate from pulmonary diseases amongst
workers engaged in the dusty trades of mining, quarrying or stonework. Mention shall, however, be confined here to recording a
few of the more characteristic results taken from enquiries made
on the spot.
Biondi (1906) had observed that amongst the miners in the
mines of Sardinia the greatest damage due to the mechanical
action of dusts occurs when the gangue of the mineral extracted
contains silicates. He had moreover noticed that coal miners

PNEUMOCONIOSIS IN ITALY

489

were almost all addicted to coughing and continued to expectorate
an entirely black sputum even some time after they had quitted
their occupation. In the workings of the mines of Bergamo, on
the other hand (1907), he found minor injuries due to dusts, perhaps
because the workers in these mines worked intermittently, the work
in the mines alternating with agricultural pursuits. In a few
miners, however, especially in the older men, Biondi met with
cases of pharyngitis and bronchial catarrh with dark sputum
due in great part to the black smoke of the candles used, and
he observed that acute affections of the respiratory apparatus
affected these workers more seriously and were of a more obstinate
nature.
Frongia (1908), in twenty-six post-mortem examinations of
miners from the Sardinia mines, effected with a view to studying
pneumoconiosis, noted that the cause of death was in most cases an
acute infection (pneumonia), but he found, nevertheless, very
frequently amongst these workers serious and diffused arteriosclerosis, emphysema and anthracotic foci, with more or less
diffused softening of the tissues and presence of gangrenous foci
containing a black broth-like matter, that is to say, the characteristic
finding of black phthisis. On the other hand, foci of bronchoectasia due to tubercular infection were only met with by him in
five cases. Eighty per cent, of the fatal cases amongst the miners
were not therefore cases of tuberculosis infection. Nevertheless,
Frongia asserts that black phthisis would not represent the
essential cause of death of the worker in any of the cases.
Pieraccini (1926) has noted amongst stonebreakers of fifty to
sixty years of age (working on the roads), remarkable
emphysematous conditions and ordinary forms of catarrh. Amongst
the road-menders, however, he found many who showed a
pronounced tolerance in the matter of resisting irritations due to
dust.
Also in the sputa of these workers little addicted to coughing
and who only suffered from time to time from catarrhal secretions
from the nose and mouth, there was found dust in such quantity
that it sufficed to take the secretion between the fingers in order to
feel the presence of sand.
Pieraccini recalls that the working atmosphere in road-mending
is one of the most dusty which exist (at least for many months of
the year) and that the road dust which he examined was highly
dangerous, since it contained amorphous silica to the extent of 22.47,
with a content of aluminium and oxide of iron amounting to 4.45.

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Evidently, however, the slight frequency of pulmonary affections
among road-menders is due to the fact that they inhale the dust
intermittently, and that for this reason it does not succeed in
injuring the bronchial mucous membrane.
Vernarecci has studied mortality from respiratory diseases among
workers in some dusty trades in Rome during the biennial period
1921-1922, and has established the following figures:
(0)

Macaroni makers and
millers
(b) Stone masons and
marble workers
(c) Carpenters and cabinet
makers
,j, M
w

masons

f
\
J
{
f
\
f
\

tuberculosis = 16.66 per cent, of all deaths
other pulmonary diseases = 33 per cent.
tuberculosis = 14.80 per cent, of all deaths
other pulmonary diseases = 14.15 per cent.
tuberculosis = 18.6 per cent, of all deaths
other pulmonary diseases = 16 per cent.
tuberculosis = 15.56 per cent, of all deaths
other pulmonary diseases = 21.11 percent.

The total mortality for all pulmonary diseases is therefore not
excessive, since it averages about 30-36 per cent, of all deaths.
In a contribution relating to the injuries to health suffered by
workers engaged in making vases (earthenware vases) in Sardinia,
Marcello (1908) refers to the frequency of affections of the
respiratory organs amongst workers engaged in turning.
Contradictory data exist relative to the incidence of pulmonary
diseases amongst workers engaged in the cotton industry. Whilst
Tassinari (1892) found amongst 100 weavers in the hospitals of Pisa
in the years 1885-1890 a death rate of 2.07 from tuberculosis and
amongst the other women in the hospital only 1.57, Pierotti during
medical examinations effected in a cotton factory at Pontedera
found :
(1) That amongst the male workers (comprising mechanics,
firemen, cotton printers and finishers) there were found
to be suffering from chest affections during the medical
examination 15.5 per cent., or 10 per cent, affected with
chronic febrile catarrh and 5.5 per cent, with tuberculosis
(2.2 per cent, of which showed certain tuberculosis and 3.3
per cent, of which were doubtful).
(2) That amongst the women, on the other hand (all engaged in
spinning, weaving and teasing), only 7.9 per cent, suffered
from chest affections, more precisely 4.3 per cent, from
chronic catarrh without fever, and 3.6 per cent, from
tuberculosis (of which 1.61 per cent, revealed a positive
diagnosis and 1.45 per cent, were doubtful).

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491

Amongst workers in the alabaster industry, where for the most
part work is carried out in narrow, badly ventilated workrooms
unprovided with exhaust ventilation, and requires faulty posture
on the part of the workman, who is obliged to inhale large quantities
of dust (sulphate of lime), Pieraccini has found a certain incidence
of catarrhal affections of the respiratory passages, but he has not
given the proportion which these constitute of the deaths in the
general population. De Hieronjmis and later De Guasta have
found amongst these workers a high percentage of tuberculosis.
Besides these generic observations on the pulmonary pathology
in a few dusty trades, we possess certain more extensive and
important studies relative to certain special materials from mines
and quarries generally regarded as involving greater risk for the
health of the workers engaged in their extraction and subsequent
manipulation.
Such materials are lime, cement and plaster, asbestos, slate,
sulphur, marble and silica. On account of their interest and of
the more accurate knowledge which we possess concerning them,
it would seem advisable to give here a more detailed account of
these.
CEMENT, LIME, AND PLASTER

Pesenti, at Alzano Maggiore, and Rota and Finzi, in Gasale
Monferreto and neighbouring districts, have contemporaneously
(1906) dealt with the health conditions of workers manipulating
lime, cement and plaster. Pesenti clearly affirms the high incidence
of pneumoconiosis amongst workers in cement and plaster, but
omits to provide proportional statistics. The conclusions which
he draws from post-mortem examinations effected by him are, on
the other hand, more explicit.
In one case he found that the process of pulmonary sclerosis had
penetrated into the pleura, which was remarkably thickened and
had lost all elasticity. In the lungs, disseminated amongst the
sparse centres of normal parenchyma, were to be seen real connective
islands thickened and hard, in the centre of which were found a
nucleus of cement which grated under the knife. These were true
pneumoliths. Similar alterations of connective neo-formations
affected the lymphatic channels and the peribronchial tubes.
A middle bronchial tube contained a broth-like mixture of cement ;
the mucous membrane of it was encrusted with pulverulent deposits ;
here and there were to be seen bronchial ectasia of varying dimensions.

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The parenchyma free from incrustation showed the characteristic
signs of vicarious emphysema.
In six other autopsies of workers in the cement industry, the
author found sclerosis localised at a few points of the lung,
circumscribed and nodular.
These forms of nodular, partial, broncho-pulmonary sclerosis
follow, the author affirms, a slow evolution, and provide few
subjective symptoms. He noted dyspnoea, loss of weight, night
sweats, pleximetric and stethoscopic phenomena, and sputa similar
to those of tuberculosis in the case of an individual in whom
tuberculosis was not discovered, neither macro- nor microscopically,
at the autopsy.
The case in question was only one of multiple nodular sclerosis
of the lungs.
The author believes that the cement dust inhaled neither produces
tuberculosis nor favours the evolution thereof, but he merely
formulates this opinion as a hypothesis. These observations
made by Pesenti are highly interesting, for they present very
clearly the picture of the various forms of pneumoconiosis without
tuberculosis, and also provide an idea of the varying nature of the
clinical picture according to the gravity of the disease.
The study- made by Rota and Finzi amongst workers in the
cement and lime industry is predominantly clinical and statistical
in character. They found that the morbidity and mortality rates
for these workers (excavators, kiln workers, transport workers,
crushing machine operators and baggers) are not higher than those
of other workers. The diseases to which they are subject most
frequently, however, are diseases of the respiratory apparatus,
and besides, they often die at an early age. In fact, out of 63 deaths
amongst the permanent workers engaged entirely in lime and cement
work, 28 died before the age of forty and 11 under fifty. The cause
of death was in 20 out of 63 cases due to pulmonary diseases, or,
more precisely, in 9 cases to acute pneumonia, in 2 cases to pleuromediastinitis and in the other 9 cases to tuberculosis. The authors
remark that there is no truth in the statement that lime-kiln
workers enjoy a certain immunity from tuberculosis as averred
by Halter. On the contrary, they found that the greatest toll
to this disease was paid by the kiln workers. For instance, in the
commune of Casale, 9 deaths of kiln workers out of 35 were due
to tuberculosis.
During physical examination of 218 factory workers, Rota and
Finzi found in 122 cases harsh respiration in the upper respiratory

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493

passages, due certainly, they assert, to an incipient pneumoniocosis
or infiltration of dust in the peribronchial lymphatic channels.
Harsh respiration was found more frequently in workers employed
for a long time, and especially in those who had already worked for
ten to twelve years. The proportions in which it was present were
the following: 52 out of 128 workers engaged at the kilns, 18 out
of 26 workers engaged in transporting stone, 43 out of 50 crushing
machine operators, baggers and porters of sacks.
Many workers were also found to be emphysematous.
ASBESTOS

From an interesting statistical study made by Scarpa, it would
appear that out of 30 workers (9 male workers and 21 women who
had been engaged in manipulating asbestos in the mines or factory
laboratories for weaving this mineral, and who were being treated
in the department of the Turin Polyclinic under the direction of
the author from 1894 to 1906), only one showed simple catarrhal
lesions of the respiratory apparatus. The other 29 suffered from
tuberculosis. All died in less than a year after the first medical
examination, since the disease in a short time brought about
destructive and ulcerative lesions of the lung. The author claims
therefore that the asbestos industry is one of the most dangerous
of those industries involving predisposition to pulmonary tuberculosis.
SLATE

Already, in a communication dealing with the enquiry into
conditions of factory workers completed in 1877 by the Ministry
of Agriculture, Industry and Commerce, the sulphur mines of
Sicily and the slate quarries of Liguria were designated as dangerous
and liable to provoke special forms of ill-health in consequence
of the nature of the work engaged in by the workers, as well as
on account of the extremely heavy and trying work involved.
In a communication presented to the third National Congress for
Occupational Diseases (Turin, 1911), Devoto and Cesa-Bianchi
have stated that " in the district of Chiavari there has been observed
a progressive loss of weight leading to premature death of workers
(in the slate industry) without there being encountered, so it is
affirmed, the tuberculosis bacillus ".
In La Medicina del Lavoro, 1929, No. 7, Devoto relates having
found in the library of the Economic Society of Chiavari two monographs by Professor G. A. Mongiardini, of the University of Genoa

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(1809 and 1812), and an Honours Thesis by Dr. G. B. Ravenna
(1812), which illustrate the life of workers engaged in slate extraction
in the quarries of Lavagna, and which contain many observations
in regard to the diseases of the respiratory apparatus in question
as well as many post-mortem findings. Also, a monograph by
Dr. N. Delia Torre, published in 1840 and entitled " Guide to the
Quarries of Lavagna", contains many clinical and sociological data
relative to these workers.
Devoto himself records, moreover, that during the Congress
of Italian Scientists, held in Genoa in 1846, there was discussed the
pathology and hygiene of work in the slate quarries and that a
priest, Giuseppe Ravenna, summarised all the medical and sociological studies on the subject in a publication dated 1879 and
entitled " Memoirs of Lavagna ". All the elements furnished by
this publication were co-ordinated in 1929 by Dr. Carlo Picchio,
a pupil of Devoto, who made it the subject of his Honours Thesis.
The following are the principal data which have been extracted
therefrom. Slate contains 25 per cent, of silica, 10 of aluminium,
35 of calcium and 30 of various other materials. About 1834 there
existed in Monte-s.-Giacomo (Cogorno) seventy slate quarries, now
abandoned, and the whole population of the region (about 4,000
persons) was engaged in working the slate, the men as excavators
and cutters and the women as transport workers.
It would appear that the mortality was not high for that period,
since Delia Torre relates that from 1828-1837 there occurred in
Cogorno only 422 deaths out of a population of 1,800 inhabitants
(23.44 per cent.). It would seem, however, that males died prematurely, since from 1800 to 1816 more than half of them died before
reaching fifty-five years of age, and in the period from 1780-1830
Delia Torre found that only one man for each 10 women reached the
age of seventy. Dr. Picchio, in scrutinising the death register
from 1800 to 1816, noted that tuberculosis constituted a very
frequent cause of death. Mongiardini also had drawn attention
to the fact of the frequent incidence of pulmonary tuberculosis,
and Ravenna had, moreover, written that the dust, being composed
of " small particles, without doubt rough, hard, sharp, and having
prominent points, calculated to wound and cut " when inhaled for
a long time, could produce in the lungs changes sufficient to favour
the outbreak of tuberculosis, which disease was commonest amongst
the workers in question. Ravenna himself carried out a postmortem examination of a quarryman and a stonecutter, and found
only evidence of pulmonary tuberculosis without dust deposit.

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The existence of true pneumoconiosis is demonstrated by the
findings of an autopsy effected by Mongiardini on the corpse of a
certain worker G. B. Binasco, aged fifty, an excavator at Gogorno.
He found " the lungs fully more voluminous than the normal, of
a dark red colour and variegated with blackish lines in the interior,
similar to the colour of slate. There were multiple adhesions,
especially of the left lung, which showed tophaceous concretions,
and amongst these, a cyst as large as an egg, filled with ashcoloured pus. The back part was far more than half scirrhous, and
almost stony and most difficult to cut into with a knife. The pleura
and the right lung were sewn with tubercles, many of which were as
big as a large hazel nut (noce avellana) and contained a blackish
humour, others a very fine black powder which blackened the fingers
and resembled wet and pulverised slate. The lung showed great
hardness under the scalpel, which in cutting became toothed like a
saw. Vésicules were found full of an earthy powder; many had
coalesced, filled with the said powder, and seemed to form cysts. "
The symptomatology presented by all the sick workers is described by Mongiardini, as well as Ravenna, in an almost identical
manner—the state of dénutrition more or less advanced to the point
of approaching cachexia, dyspnoea, emphysema, chronic bronchitis.
There is, however, some divergence between the views of the two
authors as to the interpretation of the origin of the disease, since
Mongiardini had at first denied and then (after the autopsy on
Binasco) admitted the existence of dust in the atmosphere of the
quarries, and Dr. G. B. Ravenna, on the other hand, admits that
one of the principal causes of the diseases of quarrymen is the
inhalation of slate dust, whilst he did not admit the existence of
special diseases amongst the workers manipulating slate in the openr
especially when protected against inhalation of the dusts.
Sulphur
In 1892, Dr. Giordano, of Lercara, described under the name
of theapneumoconiosis a process of chronic broncho-pneumonia
accompanied by abundant deposits of sulphur in the pulmonary
tissue and in the peribronchial glands of sulphur miners. Giordano
had had the opportunity of effecting a single autopsy on a miner,
aged fifty-one, who had worked in the mines from the age of six
and had died as a result of chronic broncho-pneumonia. In the
lungs and in the bronchial glands there was found a great quantity of
sulphur dust, but Giordano had also treated many miners suffering

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from chronic bronchial catarrh with rales, dyspnoea, cyanosis and
emphysema, in the bluish-grey sputa of whom there was found a
more or less extensive amount of sulphur dust accompanied or not
by pus corpuscles, elastic fibres and bacillus of Koch, according as to
whether tubercular infection had followed the pneumoconiosis or
whether it was merely a question of pneumoconiosis in a pure form.
He affirms, besides, having seen miners who had quitted their
occupation still expectorating, not intermittently but constantly,
pale bluish-grey matter two, seven and even twelve years later.
The observations of Giordano were confirmed by Lattuca at
Casteltermini and by Ricevuti at Caltanissetta, all of whom, as a
result of numerous autopsies on miners who had died by accident
or had been killed, found in the lungs an emphysematous state,
bronchial catarrh, greyish pigmentation, and besides, small nodules
very compact and resistant, disseminated in the tissues, which
grated under the knife and which varied in volume from the size
of a grain of millet to a pea or larger, and which presented on
section a surface of a blackish-grey colour.
Carapelle and Gabrielli, though not denying the existence of
theapneumoconiosis, have expressed doubt as to its frequency; the
first on a basis of theoretical considerations founded on the small
quantity of fine dust daily inhaled by the miners, and the second,
because, having had the opportunity of taking part in a number of
autopsies on miners and having read the accounts of a number of
other necroscopic examinations (in all eight cases), he felt unable to
confirm the presence of infiltration of the lung by sulphur dust,
whilst he found in all the cases a considerable extent of anthracosis.
Giardina, however, has confirmed having observed in a sulphur
worker who died of ankylostomiasis the complete findings
accompanying Zenker's pneumonoconiosis, and he provides the
following picture of the anatomical finding in the case of sulphur
workers :
The pulmonary tissue is rugged to the touch and grates under the
knife ; on the surface revealed in section there are bluish-grey stains and
greyish nodules which extend to the size of a pea and are at times isolated
or at other times grouped together round a caseified centre, or again
surrounded by a more or less manifestly inflamed area. In the most
serious cases, moreover, there are observed cavities in consequence of
gangrene occasioned by compression exercised on the capillaries by the
interstitial sclerosis. The bronchial tubes, here and there ectasie, are
filled with muco-pus, and charged with a pigment recalling the fine dust
of the mines. The alveoli have thickened walls and are moreover charged
with purulent matter. The marginal areas of the lungs are emphysematous and the bronchial ganglia swollen and greyish in colour.

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Numerous statistical data have moreover confirmed the frequent
incidence of pulmonary diseases amongst sulphur workers.
Di Giovanni reported to the Congress for Occupational Diseases
at Palermo (1907) that 47.4 per cent, of the sulphur workers
examined presented chronic affections of the respiratory passages
which ranged from chronic catarrh with emphysema* to pneumoconiosis.
The Health Officer of Caltanissetta has reported in the years
1896 and 1897 the deaths of 250 sulphur workers, of which 199
(79.20 per cent.) were due to bronchial and pulmonary diseases.
The Health Officer of Serradifalco has attributed to diseases of
the respiratory passages 8 out of 19 deaths (42.10 per cent.) which
occurred in 1898 amongst the sulphur workers of the commune.
Dr. Ricevuti has, moreover, reported that of 739 deaths which
occurred amongst the population of Caltanissetta as a result of
pulmonary diseases in the triennial period 1896-1898, 308 (41.67
per cent.) were sulphur workers.
It is not, on the contrary, known precisely to what extent
tuberculosis exists amongst this category of workers. Zampa has
asserted that it is very rare amongst the sulphur workers of
Romagna. Giordano, Burruano and others have said the same
of the Sicilian sulphur workers.
Yet, as Giardina has justly observed, it is difficult to admit
that sulphur dust is the almost exclusive cause of the extraordinary
frequency of diseases of the respiratory apparatus occurring
amongst sulphur workers, and that perhaps but little tuberculosis
is diagnosed on account of the fact that the bacteriological proof
is often neglected.
MARBLE

The pathology of marble workers is at present the subject of
an interesting controversy. Fraschetti, subsequent to an enquiry
on marble workers in Rome, had drawn attention to the fact that
work of this nature predisposes the workers to contract pulmonary
diseases, and Calderai had previously noted the very frequent
incidence of these disease forms in the workers of Serravezza.
During the years 1928 and 1929 there were published two works
of greater importance which arrived at opposite conclusions from
one another.
Dr. G. Bianchi, of Massa, as a result of clinical, radiological,
anatomical, and statistical observations and animal experiments,
has concluded that:
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(1) The inhalations of fine marble dust cause alteration of the
upper respiratory passages and disease symptoms (rhinitis,
pharyngitis, bronchitis) such as to render null the protective
function of these passages, which are no longer able to
offer resistance to the penetration of the fine dust itself
into the pulmonary alveoli.
(2) The fine dust, having arrived in the alveoli, gives rise to
pathological processes such that the various defensive means
possessed by the alveoli are weakened, if not abolished.
(3) The bacillus of Koch finds in the pulmonary tissue a ground
favourable to its development and its pathogenic action.
The facts on which Dr. Bianchi bases his conclusions are as
follows :
A group of rabbits kept for ten months in the marble laboratories
presented bronchial and broncho-pulmonary symptoms, consisting in
oedema, hyperemia, tumefaction, desquamation of the bronchial mucous
membrane, casts composed of peelings of the epithelium and catarrhal
secretions of the smaller bronchial tubes and the alveoli, intense vascularisation and production of new connective tissue in the interstitial
tissues, obstruction of the ganglia of the hilum. Some of these rabbits,
inoculated with the bacillus of Koch in various ways, developed tuberculosis of a much more serious and rapid evolution than others, which
had not previously been subjected to dust inhalation.
Many workers showed the entire symptomology of forms of chronic
bronchial catarrh and pulmonary sclerosis, and died of an insufficiency
of the right ventricle or of acute complications which supervened,
amongst the most frequent of which were tubercular infection.
Radiography of the respiratory apparatus has shown in the most
simple forms of " marbloconiosis ", disseminated shadows, more dense
towards the hilum, with an area varying from the size of a grain of rice
to a small nut, and with peribronchial striae. In the cases complicated
with tuberculosis, the specific tubercular foci develop preferably where
the more intense shadows of pneumoconiosis are situated and evolve
during a long time on the traces of already existent peribronchitis.
Further the cavitary lesions from the bacillus of Koch in pneumoconiotic subjects never assumed a considerable extension and rarely
gave rise to large cavities. An anatomical, and pathological examination
has revealed emphysema, sclerosis of the pulmonary tissue, the presence
of hard nodules (pneumoliths) and other features of less importance.
Finally, statistical returns have demonstrated that the percentage
of deaths from tuberculosis amongst marble workers is very high.
Dr. M. Mazzitelli, of Carrara, on the other hand, in studying
the statistics--of the causes of death of the population of Carrara,
has observed that the tuberculosis mortality figures are very
low amongst the marble workers since " out of 13,000 workers in

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499

two years there occurred 38 deaths, that is to say, 26 amongst
workers in the open, in an atmosphere slightly or not at all dusty,
and 12 amongst those daily subjected to dusty work in the
laboratories ". He therefore concludes t h a t marble dust is not
an element which can cause tuberculosis, not to speak of causing
predisposition to it. Besides he injected five times in succession,
at periods separated by one month's time, 2 grammes of white
marble dust (almost pure carbonate of lime) directly into the lower
lobe of the right lung of a guinea-pig, and this animal not only
remained free from any troubles but continued to gain weight
and to multiply. Twenty-four hours after the fifth injection the
lung of the guinea-pig subjected to radioscopie examination showed
no opacity at the point of injection and the autopsy showed t h a t
the lungs were normal in form, volume and colour, and t h a t their
surface was smooth and glossy. The peribronchial glands were,
however, well developed and firm. Microscopic examination
revealed absolute absence of marble crystals, slight signs of an
inflammatory process, with small infarcts, desquamation of the
alveolar epithelium and infiltration of the septa. The other
guinea-pigs inoculated, on the other hand, with dust from coloured
marble, from granite, or dusts of mixed marble and granite,
presented on post-mortem examination various lesions, such as
adhesive pleurisy, degenerative processes, necrosis, etc.
A chemical analysis having been made of the lime in the lungs
of the animals inoculated the smallest calcium content was found
in the case of the guinea-pig injected with white marble dust
and the largest in the case of that injected with dust from a
mixture of coloured marbles.
From the results of this and other enquiries of less importance
the author arrives at the following conclusions:
(1) Dust of Carrara marble is subject in the animal system
to processes of absorption and elimination.
(2) A true dust pneumoconiosis from marble does not occur,
at least as a usual phenomenon in consequence of work.
(3) Dust from Carrara marble. cannot therefore be considered
as phthisogenic.
It is difficult to pass judgment on these conclusions, which are
in open contrast to those formed by Bianchi.

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SILICA

In regard to the importance of silica dusts as the cause of
pneumoconiosis, we possess a single clinical study by Giglioli,
carried out by a good method and, therefore, of much weight.
Amongst the mercury mines of Monte Amiata there are some
which have an argillaceous and damp gangue and one which has
a siliceous gangue. Pieraccini had already remarked that amongst
the workers who were engaged in the latter mine (Cornacchino)
there occurred a high incidence of broncho-pulmonary affections
and pulmonary tuberculosis, and an enquiry effected later by
Drs. Puccinelli and Ginanneschi has confirmed the existence of
this fact.
Giglioli found that in many of the miners at Cornacchino and
in almost all those who worked at the top of the road, where the air
is richer in silica dust, there occurred after two to three years of
work broncho-pulmonary affections with coughing, breathlessness,
emphysema, dusty but not hemorrhagic expectorations, almost
always without fever and without marked decline. In general,
however, after a more or less lengthy period which may last even
five years fever sets in, the expectoration becomes haemorrhagic,
there occurs at times haemoptysis and organic decline becomes
evident. There appear, in short, all the signs of pulmonary
tuberculosis. There is, consequently, almost always a well-marked
pre-tubercular period, which may evolve slowly without tubercular
complications and which corresponds to the so-called miners'
phthisis as it has been precisely described in the Transvaal Rand
Mines by the English Royal Commission of 1906.
More recently than Giglioli, Mazzi (1913), on the basis of animal
experiments and clinical observations, has come to the conclusion
that silicon (in the special form of silicates) causes chronic intoxication of the system and acts especially on the blood in exercising
a general ansemia-producing action.
*

From this summary account of the studies effected in Italy
in the last twenty-five years on the problem of pneumoconiosis
confirmation is afforded of the fact that this question is well known
amongst our research workers, who have examined it from the

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501

experimental point of view as well as the clinical and anatomopathological point of view and have availed themselves on various
occasions of the means of proof furnished by semiology, radiology,
histology and histo-chemistry in order to diagnose the disease
or recognise its pathogenesis, in the same way as they have had
recourse to statistics and to a study of the objective conditions in
order to arrive at an idea of its social importance.
It is not our intention here to provide a reasoned and critical
survey of the results at which they have arrived or of the conclusions which they have drawn, and still less to discuss the methods
of enquiry which have been adopted in certain investigations.
We only wish to draw attention to a few points which seem
to us to be the most interesting for those desiring to study pneumoconiosis and bring into relationship its pathogenesis in the individual
with the social risk which it represents for certain categories of
workers.
It seems evident, in our opinion, from the studies quoted that
there exists the possibility of the manifestation of chronic bronchopulmonary affections, more or less serious in character, amongst
all the workers engaged in dusty industries, manifestations possessing clinical and anatomo-pathological characteristics analogous to
the disease described by Zenker under the designation of "pneumonoconiosis". Almost all the research workers are in agreement
in recognising that there exists a varying degTee of harm in the
various dusts which can be determined in accordance with their
physical characteristics (hardness, insolubility, sharpness of the
surface of the particles). Silica dust has always been recognised
as the most harmful, but less hard and more easily absorbed dusts,
such as, for example, flour dust, are also capable when inhaled
for a long period in large quantity of overcoming the means of
defence of the system and producing irritative phenomena or
inflammatory symptoms, of penetrating into the structure of
the tissues and there producing considerable lesions. But whether
on the basis of studies completed in Italy or of those carried out in
other countries referred to at the beginning of this paper, it seems
to us that there still await solution certain problems of pathology
which are amongst the most interesting from the point of view
of hygiene. These points are : (a) the possibility of pneumoconiosis
assuming the character of a disease with progressive evolution,
that is to say, whether its evolution continues even after removal of
the patient from the dusty atmosphere, and (b) the possibility
of its assuming a severity sufficient to endanger life of itself,

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without infective complications and especially apart from
tuberculosis.
Only after having thoroughly verified our data in regard to these
fundamental questions shall we be able eventually to engage in a
study of the reasons explaining why in a particular locality the
individual disease assumes the character of a mass infection and
becomes a menace to the whole community.
The key to the solution of these questions resides, in our opinion,
in the capacity to diagnose pneumoconiosis during life and in
being able to discriminate between it and other pulmonary diseases,
especially between it and tuberculosis.

BIBLIOGRAPHY

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Frenicotomia

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Clinica

BOATTINI a n d Lo F A S O . " Sulla essenza della antracosi polmonare. "
La Medicina del lavoro, Milan, 1928.
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C E S A - B I A N C H I , D. " S t a u b i n h a l a t i o n
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COMESSATTI, G. " Considerazioni critiche sulla patogenesi dell' enfisema
totale del polmone cosi d e t t o professionale. " / / Lavoro, 1905.
DEVOTO, L. " Il polmone nelle sue prime difese contro polveri e batterii. "
Il Lavoro, 1911.
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Società L o m b a r d a di

Sulla cosi detta malattia polmonare dei minatori.
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della Società Italiana di Medicina interna, R o m e , 1913.
La lesioni non tubercolari dell' apice polmonare.
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della Società Italiana de Medicina interna, Genoa, 1914.
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DEVOTO, L. " Le affezioni polmonari da polveri e la tubercolosi del polmone."
La Medicina del Lavoro, 1925.
" Pneumoconiosi nei suoi inizii. " Ibid.
" I danni delle polveri e le malattie polmonari." Il Policlinico,
Rome, 1929.
" Atmosfera polverosa e malattie polmonari. " La Medicina del
lavoro, Milan, 1929.
and CESA-BIANCHI, D. " La patologia polmonare da inalazioni
di polveri. " // Ramazzini, Aug.-Sept. 1911.
FELIZIANI. " Sulla genesi dell' antracosi polmonare. " 77 Policlinico, sez.
medica, 1906.
FERRANNINI, L. Gli effetti delV inalazione di pulviscolo di farina nei mugnai.
Atti del III Congresso nazionale per le malattie del lavoro, Turin, 1911.
" Pneumoconiosi da pulviscolo di cemento (Silicosi). " Studium,
1928, No. 3.
FIORI, E. " Contributo alla Clinica ed alla Radiologia delle pneumoconiosi
rare: pneumoconiosi da bario. " L'Ospedale maggiore, Milan, 1926.
FRASCHETTI, V. " Inchiesta sull'industria del marmo in Rome. " Boll.
Uff. municipale Lavoro, 1919.
GABRIELLI, G. La Pneumoconiosi nei zolfalari. Io Congresso nazionale per
le Malattie del Lavoro, Palermo, 1907.
Sulla patogenesi dell' antracosi polmonare. " Società italiana di
Patologia, Palermo, 1908.
GIGLIOLI, J. Contributo alla tisi dei minatori. II o Congresso nazionale per le
Malattie del Lavoro, Florence, 1909.
" La cosi detta tisi dei minatori. " Il Ramazzini, 1910, Nos. 3-4.
Un centro tipico di tisi dei minatori in Italia. Second International
Congress on Occupational Diseases, Brussels, 1912.
GIORDANO, A. " La malattie degli zolfatari. " Bollettino della Società
d'Igiene, 1897.
La theapneumoconioso. Io Congresso nazionale per le Malattie del
Lavoro, Palermo, 1907.
GUERRA-COPPIOLI, L. " Sull'origine dell' antracosi polmonare. " Il Ramazzini, 1911.
MARCELLO. Le malattie del lavoro dei figulinai in Sardegna. Società tra i
cultori delle Scienze mediche e naturali in Cagliari, 1908.
MAZZITELLI, M. " La lavorazione del marmo nelle cave e negli opifici di
• Carrara. " Studium, 1929.
MEDA, G. Quadro radiologico della pneumoconiosi. VII 0 Congresso
nazionale di Medicina del Lavoro, 1927.
MOSCATI, G. Effetti della penetrazione d'amido nelle vie aeree. VIII o Congresso di Fisiologia, 1911.
PESENTI. La patologia del lavoratori del cemento e del gesso. First International ón Occupational Diseases, Milan, 1906.
PiERACciNi, G. " L'arte ceramica e la patologia del lavoro. " Il Ramazzini, 1907.
" La patologia professionale degli stradini e parastradini. " La
medicina del Lavoro, 1926.
Pi E ROTTI. Le malattie degli operai attendenti alla lavorazione del cotone a
Pontedera. First International Congress on Occupational Diseases, Milan,
1906.

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POLLINI, L. Sulla presenza di polvere di carbone nei polmoni dei bambini.
III o Congresso nazionale per le malattie professionali, Turin, 1911.
RANELLETTI, A. La morbilità e la mortalità nelle industrie polverose in Roma.
VII 0 Congresso nazionale per le malattie professionali, Venice, 1924.
ROMDY. "Sull'origine intestinale della pneumoconiosi. " Il Ramazzini,
1908.
ROTA and FINZI. La patologia dei lavoratori di cemento e di calce nel circondario dì Casale Monferrato. First International Congress on Occupational
Diseases, Milan, 1906.
RUATA. " L'origine della pneumoconiosi. " Bollettino delle Scienze Mediche?
1908.
SCARPA. Industria dell' amianto e tubercolosi. XVIII o Congresso della
Società italiana di Medicina interna, 1908.
SORRENTINI, E. "Un caso di pneumoconiosi da farina di grano." Studium,
1923.
TASSINARI. " Ricerche nell' aria di una fabbrica di tessuti. " Annali
d'Igiene sperimentale, 1892.
TEDESCHI, E. Le lesioni non tubercolari dell' apice polmonare. XXIV o
Congresso della Società italiana di medicina interna, Genoa, 1914.
and ABBO. Contributo allo studio delle malattie professionali degli
organi respiratorii da inalazioni.
TOMMASI-CRUDELI. Destino della polvere introdotta nel polmone. Soc. it. di
Patologia, Modena, 1907.
VENCO. " Il lavoro della operaie nella confezione del seme bachi. " Unione
femminili, 1902-1903.
VERNARECCI. Morbidità e moralità in alcuni mestieri polverosi in Roma,
VII 0 Congresso nazionale per le malattie professionali, Venice, 1924.

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APPENDIX
Professor Loriga, when showing his collection of radiograplis,
distributed to the Members of the Committee the following four short
summaries describing the research engaged in by his collaborators.
He distributed also a volume containing the original reports, presented
by the Italian Ministry of Corporations.

PNEUMOCONIOSIS IN MARBLE WORKS
BY DR. GIACOMO BIANCHI,
DIRECTOR

OF THE ANTITUBERCULOSIS

DISPENSARY AT MASSA

In my capacity of Director of the Antituberculosis Dispensary of Massa
for some years past I have devoted attention to the possible presence
amongst the marble workers of a pneumoconiosis lesion. I have
subjected to careful clinical and radiological examination a group
of about 250 workers engaged in work in more or less closed workrooms,
such as sculptors, rough hewers, modellers and workers in the grinding
rooms.
There were excluded all cases of suspected syphilis and other chronic
lesions, with the result that the study covered seventy-three workers
engaged in marble, having no inherited disease or previous disease
history and free from definite or suspected symptoms of affections of
the respiratory passages which might come under the category of common
infections.
Thus, as can be seen on the radiograms shown, radiography has
revealed diffuse nodes of thickened tissue, spread over almost the whole
respiratory surface. In these cases there can only be determined a slight
percentage (20 per cent.) of functional alterations with symptoms of
chronic bronchitis and equally of pulmonary emphysema.
I then engaged in experimental research by exposing several series
of rabbits to marble dust inhalation in the workrooms and killing
them after a long period ; one series of animals was killed after exposure
lasting over two years.
It was recognised that all the animals suffered from the bronchopulmonary lesions described in the text, clearly revealed by the accompanying microphotographs of histological preparations which show in
an evident manner the presence of marble crystals, in particular in the
sub-pleural network, in the peribronchial connective tissue and in the
lymphatic ganglions.
On the basis of these clinico-radiological examinations and experimental researches I have arrived at the following conclusions:
\.

The marble dust inhaled during work by the men in marble
workshops causes anatomo-pathological lesions characterised by
diffuse foci of peribronchitis and interstitial pneumonia.

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2. The above-mentioned lesions can be observed radiologically
amongst workers exposed for several years to the dust and they
are accentuated in proportion to the time spent in the workshops.
3. The anatomo-pathological lesions do not cause functional disturbances except in the case of a small proportion of the workers and
it is not possible to deny that inherent constitutional factors are
connected with the appearance of these functional disturbances.
PULMONARY ASBESTOSIS
BY DR. DOMENICO LOVISETTO
My investigations have dealt with workers handling pure asbestos,
and asbestos mixed in very small quantities with cotton or other vegetable fibres. They relate to two distinct periods: the first extending
from 1902-1912 and the second from 1912 to the present time. I have
considered it advisable to keep the data relative to these two periods
separate since the first relates to workers employed on the manufacture
of asbestos under very unfavourable and unhealthy conditions as
regards the industrial organisation, as well as the type of worker
employed.
Very frequently workers suffer from forms of rheumatism, of bronchial
pneumonia and some of them from tubercular affections. Patients
suffering from chronic broncho-pulmonary forms of disease of a nontubercular character were in general men and women who had worked
for several years in the said establishment; the morbid process with
slow but progressive evolution was characterised by absence of fever
and spitting of blood. The initial symptoms affected the upper respiratory
passages, with persistent cough particularly trying during the winter
season with little or no expectoration.
In the most severe cases (workers engaged in the industry for many
years in the most dusty workrooms) besides the above-mentioned
symptoms there was noted diffuse broncho-pulmonary pneumonia
especially at the basis of the thorax with symptoms of pulmonary
sclerosis.
I have- never known patients to die of these disease forms.
I also visited each year workers presenting manifest signs of tubercular
lesions. A careful examination of these cases and a conscientious study
of their case history led me to the conclusion that these tuberculous
complications, almost always affecting young workers, only occurred
in the case of workers with hereditary predisposition or who had suffered
from lesions rendering them susceptible to tuberculosis prior to commencing work in the asbestos industry or again to those who had lived
with tuberculosis patients.
At the end of this period my personal experiments led me to conclude
that asbestos dust is dangerous on account of the irritation which it
causes in the respiratory tract and that in proportion to the amounts
of dust inhaled and the years spent under the conditions described, it
may cause a clinical picture similar to that designated in English
" pulmonary asbestosis "; on the other hand it cannot set up tuberculosis.
Where this disease occurs it must be considered as stimulation of earlier
latent tubercular foci or it is a question of causes other than inhalation
of asbestos dust.
In the second period extending from 1912 to the present time and
following on the erection of a factory construction complying with the

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507

most hygienic modern precepts, conditions amongst the workers have
greatly improved and further the workers were only engaged after
selection by thorough medical examination. It must also be remembered
that the periodical medical examination reveals at the outset the presence
of morbid symptoms even when these are still very slight.
A conscientious examination of all workers in the factory has led
to the following conclusions.
Workers who have only worked with asbestos for two or three years
generally suffer from redness of the throat and from frequent and
violent coughing not, however, accompanied by expectoration; they
show no other subjective symptoms.
On the other hand amongst workers who have been working upwards
of five years in the factory and who by reason of the process on which
they are engaged are exposed to the inhalation of dust in greater
quantities, I have been able to note slight signs of pulmonary changes.
During examination of the thorax I have often observed a slight limitation of inspiratory movement and on percussion more or less obvious
dullness at the bases, more frequently to the right than left side with
diminution of the respiratory murmur.
Amongst those with over ten years' exposure to the inhalation of
asbestos dust I have noted in addition to the above-mentioned symptomatology, some generalised pleuritic rubs with very harsh vesicular
rales. Amongst these workers the size of the heart especially the right
side seems almost always considerably enlarged and the second pulmonary sound accentuated. There is neither fever nor night sweats. At
times the patients suffer from gastric troubles though only to a slight
extent. In more serious cases a certain degree of anorexia is noted
which usually makes its appearance after the twentieth year of employment. An examination of the sputum of those patients suffering from
expectoration disclosed almost always the presence of particles of
asbestos.
Whilst radiographic examination of workers engaged for a few years
only, and of those but little exposed to the inhalation of the dust is
almost always negative, amongst the others on the contrary I found
very frequently the presence of more or less intense and diffuse shadows
particularly corresponding to the base with hilar markings and diminished
chest expansion. A short rest is quite sufficient for rendering these
patients once more fit for work.
During the five years three deaths occurred amongst workers in the
factory and they were due: the first to arteriosclerosis,the second to
broncho-pneumonia in the form of influenza and the third to tuberculosis.
probably due to family infection.
Amongst all the patients examined during these last months, three
only showed symptoms sufficient to warrant suspension of work.
It transpired from the history of these three patients that two of
them (the first and the third cases) had worked on asbestos for about
ten years, whilst the second had only followed the occupation for three
years, and that though showing symptoms characteristic of those who
inhale asbestos dust over a long period, they showed morbid phenomena
of varying types modifying the characteristic asbestosis lesion.
In the first case there was anorexia, dyspnoea, intermittent fever,
marked loss of weight, on examination of the patient: generalised
pleuritic friction, diminution of the respiratory movement, more marked
on the right side, dullness at both bases, with attenuated vesicular
murmur and very harsh respiration at the bases. On radiographic

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examination there was noted considerable reduction of the transparency
of the two lungs, especially of the lower lobes and at the bases, increase
of radiographic density in the hilar regions with intensely opaque
striation, which became thickened and irradiated in the pulmonary
parenchyma. Dyspnoea and anorexia are the symptoms currently
noted amongst those workers who have for long years inhaled asbestos
dust, but the fever has a different aetiology.
In fact the first patient at the age of twenty had suffered from serofibrous pleurisy, and a considerable decrease in weight (10 kg.) which
occurred quite recently, fever, generalised friction of the pleura, diminution of the transparency of the right lung, point to the presence of a
lesion, probably tuberculous, of the pleura and the right apical region.
In this case I think that a lesion, probably tuberculous with slow
evolution, became superimposed on a fairly marked pneumoconiosis.
The same may be said of the second patient. In fact the case in
question was one of an emaciated individual who at nineteen years
of age had suffered from dry pleurisy and who last year had been
spitting blood; morbid processes of the pleura are present and are still
active. It should be noted that the aetiological factor " asbestos "
assumes a lesser importance since the patient had been employed in
the factory for nine years only and had been engaged on an operation
which was almost free from dust production.
In the third case the patient in question was a woman who had lived
for years with a tubercular husband and who had been working for
ten years in a very dusty atmosphere manipulating blue asbestos, which,
as is well known, contains the kind of dust which exerts the strongest
effect. She showed besides a very advanced degree of pneumoconiosis
and in addition pleurisy as demonstrated with proof by the radiographic
examination which revealed in a clear manner the presence of pleurodiaphragmatic adhesions. The presence of blood-stained sputum likewise
points to a pulmonary affection of another type.
Examination of the sputum has shown in the three cases the presence
of asbestos fibres. The Koch bacillus test for tuberculosis was negative.
In conclusion, inhalation of asbestos dust in the long run causes
pneumoconiosis; the period required for the manifestation of this
pathological state is at least five years. There is a direct ratio between
the quantity of dust inhaled and the pneumoconiosis; the higher is the
dust concentration the less time is necessary for the manifestation of
fibrosis. It can reach complete development after a period of seven to
nine years and it can cause death after thirteen years on condition
that the individual is continuously exposed to the risk in a very dusty
atmosphere.
When the cause of the inhalation of the asbestos dust is withdrawn
the pneumoconiosis process is generally arrested.
The functional injuries caused by the inhalation of asbestos dustoccur very slowly and are characterised by dyspnoea on effort, and by
a slight insufficiency of the right heart, the patient after being attacked
may work for a long time with brief spells of rest.
It is very doubtful whether pulmonary asbestosis favours the occurrence of acute pulmonary affections though the anatomical conditions
of the sclero-fibrous lung which cause a slowing down of the blood
circulation in the lung (pulmonary stasis) may justify the supposition
of a more ready development of the pathogenic germs in the respiratory
passages.
Pulmonary asbestosis is a disease in itself which must not be confused
with other diseases of the lungs; it is an occupational disease noninfectious and non-contagious. It is of slow progressive evolution but

PNEUMOCONIOSIS

ITALY

509

when the irritant action of the asbestos dust inhaled has ceased the
fibrous process is generally arrested.
Cases with a fatal issue are rare and at the present time, with modern
means of protection, with highly perfected exhaust and ventilation
apparatus they should no longer occur.
Pulmonary tuberculosis is on the other hand an infectious disease
of slow progressive and quite characteristic evolution ; and the anatomopathological data and pathogenesis are likewise typical.
It may be conceded that the inhalation of particles of asbestos, by
causing chronic irritation of the respiratory passages of the lung, may
favour in a limited number of cases, installation of the Koch bacillus.
CLINICAL AND RADIOLOGICAL NOTES ON PNEUMOCONIOSIS
DUE TO ASBESTOS
BY DR. GIOVANNI MUSSA
Dr. Mussa reports the result of examinations of workers employed in
the Nola Canavese factory for the treatment of asbestos and india
rubber.
All the workers who have worked for some time in the establishment
show lesions of pneumoconiosis which can be recognised clinically and
radiologically.
Very often previous case history provides no positive data and
individuals showing lesions in a fairly advanced state do not feel any
particular discomfort.
The first signs experienced subjectively are: breathlessness on slight
fatigue, dry cough and later expectoration of small quantities of mucous.
Clinical examination reveals in many of the cases more or less accentuated dullness in the right infraspinous fossa of the scapula—region in
which the vesicular rales are harsher and the vocal and tactile tremor
more accentuated.
There is sometimes cardiac transversal dilatation; the apex beat is
displaced a little beyond the nipple line; the second sound more accentuated at the base, sometimes with duplication of the aortic second
sound.
The radioscopie examination reveals: marborisation distributed
bilaterally in the hilar and perihilar zones which in the most advanced
cases considerably reduces transparency. Sometimes there is infiltration
of the bases. The apices are almost always free and motile. Examination of the sputum has not revealed the presence of asbestos crystals.
No case of association of pneumoconiosis with tubercular lesions was
met with.
RADIOLOGICAL AND CLINICAL STUDIES EFFECTED AMONGST
THE CARRARA MARBLE WORKERS
BY DR. LUIGI TURANO
DIRECTOR, INSTITUTE OF RADIOLOGY,

CIVIL

HOSPITAL,

CARRARA

I have examined 105 workers in regard to each of whom, subsequent
to clinical examination, and wherever possible, examination of the
sputum, radioscopie and radiological examinations were made. I have
examined workers employed in marble grinding and in other workshops

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where there was intense grinding, taking care to examine workers of all
ages, with all grades of working experience (in point of time—maximum
fifty years) and from all kinds of work: sculptors, rough hewers, sawyers,
polishers.
I have met with pleuritic lesions (remains of basal pleurisy, interlobular hyperplasia, etc.) in a proportion of about 10 per cent, and these
in view of their extent I am tempted to connect with the effect of dust
inhalation, for though the dust does not become accumulated on account
of its facility for becoming dissolved in the respiratory parenchyma it
nevertheless produces very probably pleuritic reactions by reason of the
continuous irritation which it sets up.
I must state that in all those cases in which I found alterations of the
pleura there were no tubercular antecedents (with the exception of two
cases), but on the other hand as will be seen later there were clearly
noted changes in the radiograph of the lungs.
I only found 4 per cent, of cases of calcification, a percentage which
it will be agreed is too low and which rules out of account the possibility
of carbonate of lime—inhaled, even in a continuous and intense degree
as is the case for workers in the marble industry — becoming localised
and accumulating in the pulmonary tissues.
The fact which struck me next was, however, that of having found in
28 per cent, real changes in the radiograph of the lung, consisting in a very
marked reinforcement of the latter, in an arborescent aspect and a
thickening of the vessels themselves.
Now if all the radiographs shown be examined this strongly reticulated
aspect of the vascular network, the alterations in which may be due to
the following causes, will be clearly seen :
(1) either the vessels are affected by the thickening process (very
probably phenomena of endoperiarteritis) as found in the case of
workers subjected to dust inhalation, as has been clearly demonstrated by pathological anatomy;
(2) or there are phenomena of actual lymphangitis, as shown by
certain radiographs;
(3) or the vascular network which in many cases stands out against
the great transparency of the pulmonary field may be interpreted
as a change of slight extent due to emphysema which reaches a
high incidence rate among the workers.
However that may be, the facts which I have just mentioned provide
such ample evidence, that it is unnecessary to insist further on the fact ;
on the other hand I can merely advance hypotheses relative to the
interpretation of the symptoms, since it is evident that only verification
by post-mortem examination can reveal the truth.
The above-mentioned alterations correspond to what I had noted with
regard to the initial stage of pneumoconiosis, for they are lesions of slight
importance. In no case did I find distinctly diffuse nodular pictures as are
usually met with in pneumoconioses and especially in those produced by
silica and by iron.
On the other hand, the observations which I have made in regard to
radiographs of tubercular marble workers established bacteriologically
are interesting.
In the case of five workers who showed the Koch bacillus in the
sputum and who had a previous tubercular history the radiological
examination provided strange pictures as will be seen on the relative
plates. In one of them is seen opacity of the medial region of the left
lung with dissemination of small shadows certain of which show blurred

PNEUMOCONIOSIS IN ITALY

511

outlines, others clear outlines, whilst the apical and subapical regions are
perfectly free.
In another case on the other hand there is seen (fig. 4)1 in correspondence
with the lower region of the right lung an opaque patch as large as a
tangerine with blurred outlines, whilst the remaining parts of the lung
and in consequence the apices and the subclavicular regions are perfectly
free.
It is unnecessary for me to stop to demonstrate the fact that such
radiological pictures are very rare, I might even say atypical in proportion
to the ordinary aspects of pulmonary tuberculosis, which we have the
opportunity of observing. Yet this atypical character, these strange
forms of tuberculosis which occurred in the case of two workers—
sculptors who had been working one for 27 years and the other for
5 years on white and coloured marbles—are due according to available
evidence to associated tuberculosis and pneumoconiosis; that is to say,
that the silica dust contained even in very slight quantity in the marbles,
in particular in the coloured marbles, had in my view, on account of
conditions which we are unable to detect, encountered special predisposition suitable to its fixation and . association with tuberculosis, thus
rendering possible pulmonary tuberculosis in sites which are atypical for
this disease.
I must in closing recall that studies particularly of a statistical nature
conducted by the Director of the Health Bureau of Carrara, Dr.Mazzitelli, have clearly revealed the fact that tuberculosis at Carrara does not
show special gravity as revealed by the mortality rate for workers. Yet
this infection does not however on the other hand, as erroneously believed
by some, follow a particularly benign course, first because the marble dust
becomes dissolved in the pulmonary tissues 'and consequently the
tubercular lesions are not iniluenced by inhalation of marble dust.
In conclusion the changes met with amongst Carrara marble workers
may be classed in the initial stage of pneumoconiosis, that is to say
comprising the least serious forms of the disease, such as the very marked
reinforcement of the pulmonary outline, due as demonstrated by the
personal observations just quoted, to the processes of arteritis and
lymphangitis, and in certain cases equally to conditions of emphysema
usually present amongst those workers.
I have also found frequent pleuritic changes which can be related
to inhalation of marble dust, but never however lesions of the pulmonary
parenchyma.
The radiological aspect of pulmonary tuberculosis amongst the workers
examined is on the other hand highly important, since it shows an
atypical picture on which are noted lesions with unusual sites and
apical and subclavicular regions unaffected. It is this fact which has
led me to admit the probability of a combination of pneumoconiosis and
tuberculosis.
Finally statistical as well as radiological data justify absolute exclusion
of the theory of a particular benign or malignant course of tuberculosis
amongst marble workers, as likewise of any kind of predisposition to the
said specific disease.
1
This refers to the radiographs exhibited by Dr. Loriga, which are not
reproduced here.

SILICOSIS IN THE NETHERLANDS
BY DR. W. R. H. KRANENBURG,
MEDICAL ADVISER TO THE FACTORY INSPECTORATE AT THE HAGUE

INTRODUCTION

Our knowledge of silicosis is based chiefly on information obtained
through the introduction of the Stonemasons Act and the medical
examinations of adult workers in the stonemasons' industry established
in pursuance of that Act.
PREVIOUS HISTORY

" Stonemasons' disease " was for many years classified with
tuberculosis, where at the present time it would in many cases
be more accurately diagnosed as pseudo-tuberculosis. This is not
a matter for surprise when it is considered that, in the light of
our present knowledge, the symptoms of this disease may take a
form similar to those of lung tuberculosis, and when the statistics
of that time are studied.
According to Sommerfeld1, on a medical examination of
2,013 stonemasons in 1899,169 were tuberculous, while 10.8 per cent.
were noted as strongly suspected of tuberculosis.
The higher death-rate than in less unhealthy occupations, which
was to be expected from the bad health conditions among stonemasons, appears from two Dutch statistical returns relating to
death-rate according to occupation calculated for various age-groups
for ninety-six occupations and combinations of occupations.
During the years 1891-1896 the death-rate among stonemasons
1
Verhandlungen der Deutschen Gesellschaft für öff. Gesundheitspflege zu
Berlin, Sitzung vom 26. März 1900.

SILICOSIS IN THE NETHERLANDS

513

calculated for all men between eighteen and fifty years of age
was greater than in any other occupation and the same was the case
in the period 1896-1900. Even such injurious occupations as
compositor, cigar maker and diamond cutter show a considerably
lower death-rate.
It is noteworthy that in the age-group 18-24 years the death-rate
differs little from the average for all occupations, while the highest
death-rate is to be noted in the age-group 36-50 years. The difference
in the mortality figures increases with the length of employment
in the occupation. In the statistics covering the same period of
five years relating to causes of death according to occupation and
age, the mortality from diseases of the respiratory organs in the
age-group 18-50 years is seen to be considerably higher among
stonemasons than the average for all occupations.
In the period 1886-1898 Sommerfeld mentions that out of
952 stonemasons 1 dying in those years, 87 per cent, died of diseases
of the respiratory organs, in connection with which it should be
remembered that in Germany a great deal of sandstone is worked,
as was formerly the case in the Netherlands, while in Belgium a
large quantity of limestone from the local quarries is worked.

ENQUIRIES PRECEDING THE INTRODUCTION OF THE STONEMASONS
ACT, 1911

Various important enquiries into the life and health of
stonemasons in the Netherlands were carried out which, as a result
of the indisputable evidence of the unfavourable health conditions,
led to the introduction of this Act.
In the annual reports of the Factory Inspectorate for 1903
and 1904, a detailed and carefully prepared report was published
by the then assistant factory inspector, C. J. P. Zaalberg, relating
to conditions and evils in the stonemasons' industry.
In 1906 177 stonemasons were examined by Dr. Elias 2 in
Rotterdam, but without an X-ray examination. As a result of
symptoms agreeing with those in tuberculosis, 22 stonemasons
were considered as suffering from tuberculosis and a number of
others as more or less suspect.
1
2

Workers in stone, not quarry workers.
S. ELIAS: lets over steenhouwers en hun vak.
1909.

Rotterdam, Immig & Zn.,
33

514

PAPERS PRESENTED TO THE CONFERENCE

In the same year a Commission x was appointed, on the proposal
of the Directorate of the Social-Technical Association of Democratic
Engineers and Architects, to carry out a more thorough enquiry
into the injurious effects of stonemasons' work and the necessary
measures for remedying the evils. With the co-operation of various
doctors 356 stonemasons were medically examined, with the result
that 52 were found to be obviously suffering from lung tuberculosis
and 62 suspected of this disease. No sufficient grounds were found
for the high death-rate from tuberculosis in the use and abuse of
alcohol, fatiguing labour, or the vibration of the chest from the
stroke of the hammer.
The microscopic structure of various kinds of stone dust examined
confirmed the impression that granite and sandstone constituted
a danger owing to the fine texture of the dust and the small cohesion
of the dust particles. Even then the question was discussed whether
the inhaling of particular kinds of dust prepares the ground for
the tubercle bacillus.
Various data given below are taken from the report of this
Commission.
Kinds of Stone
Natural stone is worked in the Netherlands for various purposes
in a great variety of kinds and is for the most part imported from
abroad.
Natural stone is only found in the Netherlands itself in certain
places in the south of the country ; limestone in the Pieters Mountain
near Maastricht in South Limburg; sandstone and limestone
near Kunrade. A kind of freestone is used on a large scale in the
Netherlands for engineering works and in domestic building, which
is generally known to stonemasons as " blue stone " and which is
a natural limestone obtained from a number of Belgian quarries.
In addition to this limestone other kinds of limestone are employed,
such as Morley, Roche d'Euville and Savonnière, from the quarries
in the north and north-east of France, and marble from Italy,
Belgium and Greece. Granite is imported from Sweden,
Norway, Germany and Scotland. The dust both from the Belgian
limestone and the French limestone is regarded by stonemasons as
less troublesome than sandstone dust. The use of sandstone is
chiefly confined to monumental buildings and to decoration, while
1

S T E E N H O U W E R S A R B E I D EN S T E E N H O U W E R S Z I E K T E :

1910.

Rapport.

Rotterdam,

SILICOSIS IN THE NETHERLANDS

515

building proper is carried out with brick. In addition to the abovementioned sandstone quarried in the country, sandstone from
Teutoburg, Oberkirchen, Bentheim, Gildehausen, Bremer and now
also Nivelstein sandstone, imported from Germany, and Bollendorf,
Pilsen, La Rochette, Udelfangen and Borne sandstone from
Luxemburg are worked.
As the result of many years' experience the Dutch stonemasons
regard the Teutoburg as the most injurious to health of all kinds
of sandstone, the Oberkirchen, Bentheim and Gildehausen, among
others, as somewhat less injurious, while the Bremer sandstone is
also considered as among the dangerous kinds. The Udelfangen
and Borne sandstones are less feared and are assimilated to such
limestones as d'Euville, Morley, etc.
It has been shown in a remarkable way by a chemical analysis
for determining the lime content of various kinds of stone, carried
out by the chemical engineer De Voogt in his laboratory, on the
proposal of Sleeswijk1, of Delft, that a parallel exists between
the estimate of the dangerousness of particular kinds of stone
from sandstone to limestone and the presence or absence in greater
or less degree of lime.
The following table gives a summary of these results:
Sandstone
free from lime

Limestone, Belgian limestone,
and lime sandstone containing lime

Oberkirchen
Bentheim
Gildehausen
Red Bremer

Udelfangen sandstone contains 13 per
cent. lime.
Roche d'Euville limestone 16.7 per cent.
Hard Morley limestone 17.9 per cent.
Soft Morley limestone 27.2 per cent.
Belgian limestone 20.4-21.4 per cent.
Shell limestone 25.7 per cent.

The mixture of lime seems to exercise a favourable influence on
the dangerousness of sandstone. The same appears to apply to
clay and coal dust 2 .
Collis and Gilchrist 3 however observed in coal-heavers after
several years' work " signs similar to those widely regarded as
characteristic of silicotic fibrosis ".
1

Bedrijfshygiënische vraagslukken Tijdschr. v. Soc. Hyg., 19th Year, 1917,
No. 4.
2

HEFFERMANN and GREEN:

Journal of Industrial Hygiene, Vol. X, 1928,

No.8 10, p. 272.
Journal of Industrial Hygiene, Vol. X, 1928, No. 4, p. 109.

516

PAPERS PRESENTED TO THE CONFERENCE

Stonemasons' Tools
The tools most in use in stone working are illustrated in figs. 1,
and 2. Nos. 1-7 (fig. 1x) are chisels of various kinds and weights
which are manipulated by means of a wooden hammer varying
in form and weight ; the pointed chisel (3 and 4) is used for cutting
away larger protrusions on the stone; the Bouchard chisel (7)
is used for obtaining an equally rough pointed surface. All these
tools, in the working of stone, give rise to dust. The fact of the
toothed chisel (6) becoming blunt and consequently unuseable
has led to the invention of a handle provided with a slot in which
an inset piece with teeth of various kinds is inserted (6a), which
has proved economically more advantageous.
In addition to the chisels, the tools shown in fig. 2, Nos. 10, 11,
12, 13 and 14, are in use.
The Bouchard hammers (10 and 11), heavy iron hammers with
wooden handles, are chiefly used in the working of Belgian limestone.
On sandstone the point of the hammer soon becomes blunt, which
is uneconomical. The stonemason's beam (13 and 14) is used for
the same purpose as the Bouchard hammer and consists of from
ten to seventeen pointed chisels placed side by side and fixed by a
wedge in an iron frame with an iron handle. These, tools are much
heavier and consequently much more fatiguing to work than
ordinary chisels, while the creation and dispersion of dust is
considerably greater.
Working Position
It is obvious that the chance of inhaling dust is influenced by the
position of the stonemason while cutting. The cutting of the stone
is the dangerous work which is generally carried out in a sitting
position, in connection with which a crouched position is to be
condemned. (See fig. 3.)
Age of Commencing Work
In the enquiry by the Commission into the age at which stonemasons commence work, it was found that formerly even children
of ten, eleven and twelve years of age in not inconsiderable numbers
(106 out of 356 stonemasons examined) chose this dangerous
occupation as their calling.
1

The illustrations (figs 1-4) are given after p. 534.

SILICOSIS IN THE NETHERLANDS

517

Hours of Work
The hours of work varied from 10 to 13 per day. Piecework
led to great over-exertion owing to the desire to earn a great deal
in a short time.
Housing Conditions and Workplaces
The housing conditions were not worse than with other classes
of workers. Workplaces were generally in a miserable condition,
lacking sufficient ventilation, too low and too small. The lack of
open spaces and open sheds for outdoor work in fine weather were
among the defects noted.
Abuse of Alcohol
Irregular living and abuse of drink are commonly regarded as
causes of the outbreak of " stonemasons' disease ". As regards
the abuse of drink, this was certainly considerable, especially
among pieceworkers, although it is well known that a noticeable
diminution is observable in this respect.
Conclusions
The conclusions of this important report are, briefly stated, the
following: tuberculosis among stonemasons should be regarded as
an occupational disease. The health conditions of stonemasons
in the Netherlands are very unsatisfactory, the death-rate from
lung tuberculosis and diseases of the respiratory organs abnormally
high. Stone dust, and particularly the dust arising in the working
of many kinds of sandstone, must be regarded as the primary
cause of the abnormal sickness and mortality figures. The working
of Belgian limestone and other kinds of limestone is less prejudicial
to health. The introduction of a law for the combating and
prevention of " stonemasons' disease " is considered as urgent.
Measures for Protection
The following are considered as measures for the protection of
health: preliminary medical examination of young workers before
entering the occupation, not earlier than sixteen years of age,
followed by periodical re-examination; removal from the occupation
of cases of incipient tuberculosis, and at the same time the assimilation of this occupational disease to an industrial accident;
limitation of hours of work to eight hours a day, with regulation

518

PAPERS PRESENTED TO THE CONFERENCE

of rest periods; strict regulations relating to the arrangement and
use of workplaces; the requirement that certain kinds of stone
should be worked in a moist condition; prohibition of the working
of certain kinds of sandstone, together with prohibition of their
importation, and prohibition of the use of the stonemason's beam.
The wishes expressed on the basis of this report, and the minimum
demands made for measures for the protection of stonemasons, led
in a short time to the introduction of the desired legislation.
THE STONEMASONS ACT,

1911-19211

This Act, containing regulations relating to the special risks
to safety and health connected with the work of stonemasons, came
into force in 1913 2 and was amended in 1921 3.
Its principal provisions are summarised below.
The employer must see that the workplaces and their accessories
and the methods of work comply with certain regulations 4. The
distance between the chisels used by persons doing stonemason's
work on different pieces of work must be at least 70 centimetres,
when working sandstone on one and the same block 1% metres,
in the case of stone other than sandstone at least 1 metre except
in the case of fine work. Stones worked, being sandstones or other
stones, which absorb water without involving any serious difficulty
in working, must be kept moist. The use of the stonemason's beam
in such work is prohibited and also the use of the Bouchard hammer,
where the same weighs more than 31/4 kilograms, except in working
granite. An open space for working in the open air must be available
in the workplace. The hours of work per day, which were originally
limited to nine for workers over seventeen years of age and seven
and a half for young workers under seventeen years of age, have
since the amendment of the Act in 1921 been fixed at eight hours
a day and forty-five hours a week for workers over eighteen years
of age and seven and a half hours a day and forty-two hours a
week for workers under that age. The rest period after three and
a half hours of work must be at least half an hour. Piecework is
prohibited for young persons under eighteen years of age. Employment in stonemason's work is prohibited for young persons under
fourteen years of age.
1
2
8
4

Staatsblad 315, Act of 7 October 1911.
1 March (sections 2 and 4 on 1 May).
11 Nov. 1921, Staatsblad 1167.
Steenhouwersbesluit 1913, Staatsblad No. 38, amended 1923, Staatsblad
No. 297.

SILICOSIS IN THE NETHERLANDS

519

COMPULSORY MEDICAL EXAMINATION

Every stonemason under twenty-one years of age must be
in possession of a stonemason's card, which is issued to him after
medical examination carried out free of charge, if it does not appear
t h a t the performance of stonemason's work will give rise to any
special danger to his health. If the examination took place before
eighteen years of age, the stonemason's card ceases to be valid
after one year and a fresh examination must take place. A person to
whom a card is refused may, within fourteen days of the date borne
b y the notification of such refusal, apply to the Minister of Labour,
Commerce and Industry for a re-examination, for which one or
more medical practitioners are designated.
The compulsory examination of adult stonemasons, that is to
say, at twenty-one years of age and over, was introduced for the
first time after the amendment of the Act in 1921. A stonemason's
card is issued irrespective of the result of the examination. If at the
date of the examination the stonemason is eighteen years of age
or older, the card ceases to be valid after the expiry of three years
from t h a t date. Before 1921 an adult stonemason could be medically
examined free of charge voluntarily with a view to ascertaining
whether the performance of stonemason's work would involve
special danger to his health.
Compulsory Examination of Stonemasons
under Twenty-One Years of Age1
Medical examinations before and after entering the occupation
are at present carried out by five medical practitioners in permanent
service belonging to the Central Service of the Factory Inspectorate
and by private medical practitioners appointed in accordance
with a specified scheme. Examination has in certain respects a
preventive effect, in so far as it dissuades persons of weak constitution from choosing the stonemason's trade, in the anticipation
t h a t they will be rejected. Examination has resulted in the weeding
out of young persons with defective lungs. During the first 3 ears
after the Act came into force not a few young persons were rejected.
Thus in 1913, out of 266 examined, 29 were rejected; in 1914, out
of 254 examined, 23 were rejected; while in 1924 and 1925 only
one person was rejected out of 120 and 146 respectively examined.
1
DEPARTMENTAL COMMITTEE FOR THE DIAGNOSIS OF SILICOSIS: Home Office,
London, 1929. (Cf. "The Value of Initial and Periodic Examination.")

520

PAPERS PRESENTED TO THE

CONFERENCE

The grounds for rejection are various: mostly lung defects, also
general debility, kidney diseases, curvature of the spine, chronic
otitis media, insufficient nasal respiration, etc. It has not been
possible up to now to take X-ray photographs of the lungs of
young persons between fourteen and eighteen years of age.
Compulsory Examination of Adult Stonemasons
The compulsory medical examination of adult stonemasons,
that is to say, at twenty-one years and over, is based on section 3,
subsections (1) and (8) of the Stonemasons Act, 1921. The periodical examination takes place at the expiration of three years from
the time when a stonemason's card was issued irrespective of the
result of the examination. There is no question therefore of rejection, as in the case of stonemasons under twenty-one years of age.
If the result of the examination so requires, the examining medical
practitioner gives the stonemason instructions as to the precautions
to be adopted in connection with his work and the manner in which
he should live in order to avoid injury to his health, so far as possible.
Co-operation of the Factory Inspectorate with the Public Health
Inspectorate and the Consultation Offices for Tuberculosis
This co-operation has made it possible to obtain a considerable
number of X-ray photographs of stonemasons examined in the
Consultation Offices for tuberculosis in various localities in the
Netherlands. The supplementing of clinico-physical examination
by an X-ray photograph has proved of great importance for forming
an opinion of lung affections due to the inhaling of stone dust.
Medical Examination of Stonemasons
As a general rule every stonemason is examined, in accordance
with a uniform scheme for the whole country, by two medical
practitioners, one a medical officer in the Factory Inspectorate
and one an examining medical practitioner of the Consultation
Office for Tuberculosis. Where this is not possible, the examination
is carried out by two medical officers of the Factory Inspectorate.
The stonemason is summoned to attend for examination at a
specified centre by the district chief of the Factory Inspectorate.
The first general examination of adult stonemasons took place
in 1923, the second in 1926 and the third in 1929, so that it has been
possible, although not in a large number of cases, to compare with

SILICOSIS IN THE NETHERLANDS

521

each other the clinico-physical condition of the lungs of the same
person at the three dates and three X-ray photographs.
The subjoined table gives a survey of the total number examined
and the X-ray photographs taken in the above-mentioned years.

Year

X-ray photographs

Number examined

1923
1926
1929

Total taken

With positive results

274
111
69

232
97
57

963
889
799

1
In addition a number of X-ray examinations were made without photographs being
taken.

How indispensable X-ray examination is as a supplement to
clinico-physical examination for the purpose of judging the state
of health may be seen from the subjoined table taken from the
first general examination of 1923.
CLINICAL

AND

X-RAY

EXAMINATION

274

CASES,

CLASSIFIED

ACCORDING TO THE NUMBER OF YEARS OF EMPLOYMENT
IN THE OCCUPATION
Lung

Affections

noted in

1923

Years of employment
0-5

Clinical, affection;
X-ray examination,
no affection
Clinical, no affection;
X-ray, affection
Clinical, affection;
X-ray, affection
Clinical, no affection;
X-ray, no affection

—

5-10 10-20 20-30 30-40 40-50 50-60

Total
examined

135

105

33
20

274

From the above figures it will be seen that in nearly half the
number of cases the X-ray examination gave more information
than the physical examination. In a corresponding statement
on 69 cases from the general examination in 1929, lung affections

522

PAPERS PRESENTED TO THE CONFERENCE

are not shown clinically in 19 cases, but are shown in the X-ray
examination, and in 38 cases both clinically and by X-rays.
Subjective Complaints and Objective Phenomena
It is noticeable that in the general examination of stonemasons
in 1923, 1926 and 1929, few complaints were received as to the
state of health of the patients; most of them felt quite well, though
a certain number complained of shortness of breath when moving.
Here and there men complained of coughs with little or no sputum,
which explains why altogether an examination of the sputum was
made in only 48 cases, with positive results as to the presence of
tubercle bacilli in 11 cases. After inhaling stone dust for many
years, complaint was made of irritation in the throat and a stifling
feeling in the breast, with relative shortness of breath, an inclination
to cough and expectoration, especially on rising in the morning.
Generally speaking, percussive irregularities are few and auscultatory phenomena more striking: rough, heightened or weakened
respiratory rustling, lengthened or jerky breathing in one or both
apices or other places, also cracking and dry snoring noises, varying
in strength and area, seldom damp or crapitating. Coughing and
sputum which is not characteristic often only occur when bronchitis
appears as a complication.
The X-ray picture x of pneumonoconiosis, due to the dust of
various kinds of stone, does not differ in its various degrees from
those given for silicosis by various investigators 2 : (1) enlarged
hilus-shadow, increased appearance of the retiform tissue and linear
shadows; (2) increased appearance as in (1), and the appearance
over a wide area of stippled shadows (mottling), and (3)
appearance as in (2) and nodular shadows, large close mottling.
The question of the mutual relations between pneumonoconiosis
and tuberculosis, whether the tuberculosis only appears in later
years as an infection on a foundation of silicosis-—tubérculo-silicosis
—or the silicosis is secondary to tuberculosis latent in youth and
manifesting itself later—silico-tubérculosis—appears to be more
1
Out of 274 cases radiologically examined, 42 showed no affection. For
information as to the special cases. (139) of silicosis, reference should be made
to the reports on this head concerning stonemasons employed for many years
in the occupation in the medical examinations of the Factory Inspectorate
in 1923. Not all cases are summarised, where there are similar cases with
insignificant differences. (Centraal Verslag der Arbeidsinspectie over 1923.
Algemeene Landsdrukkerij, 1924.)
2
Jarvis, Sutherland and Bryson.
Irvine includes incipient mottling in
the first stage.

523

SILICOSIS IN THE NETHERLANDS

and more answered in this sense 1, that each of the two processes
favours the development of the other, and that the tubercle bacillus,
appearing as a secondary factor, often seriously threatens health
and life. In this connection the case is noteworthy of a stonecutter
forty-seven years old who, on a clinical and X-ray examination,
showed an affection of the apex of the right lung without exhibiting
radiologically any degree of silicosis after thirty-four years' work
on sandstone.
A concise critical survey of the position of the question of silicosis
and tuberculosis appeared in connection with the proceedings of
the Fourth Meeting of the Permanent International Committee
for the Study of Occupational Diseases at Lyons in 1929 under the
signature of Böhme in Klinik und Silicosis II, which also contained
a study by Mavrogordato on the aetiology of silicosis.
The clinical distinction between tubérculo-silicosis and silicotubercdlosis2, as Watkins-Pitchford justly remarks, makes no
essential difference to the fundamental pathological processes.
Since 1923, 16 stonemasons have died, of whom 9 died from
pulmonary tuberculosis; only in 2 cases was it possible to confirm
the clinico-radiological examination by a post-mortem examination.
Dutch stonemasons generally die at home and not in a hospital,
so that a post-mortem examination rarely takes place. That in a
number of cases the triad—clinico-physical examination, X-ray
examination, and post-mortem examination—is necessary for the
definitive judgment of the process is obvious. On a post-mortem
examination of a stonemason sixty-six years old, numerous permanent foci were found in both lungs, and here and there caverns
with secondary tuberculosis of the wall, although the X-ray
photograph had not sufficiently demonstrated this. The man died
of hœmorrhage from a cavern as large as a fist.
Dust Content of the Air in Working Various Kinds of Stone
A certain number of analyses of air for determining the dust
content were made by the factory inspector, Schölte, close to the
mouth of a stonemason. When working moist Oberkirchen sandstone the results were 45.8, 99 and 109 mg. per cubic metre of air;
[Text continued on page 526.]
1
B Ö H M E and L U C A N U S : Deutsche Medizinische
No. 38, p . 1604.
2
W A T K I N S - P I T C H F O R D : Journal of Industrial
April 1927.

Wochenschrift,
Hygiene,

53rd Year,

Vol. I X , No. 4,

524

PAPERS PRESENTED TO THE CONFERENCE

In 1923
Years
Age in
occupation

Kinds of stone worked in order
of working
from youth onward
before 1923

Clinico-physical results
1923

1926

1929

Belgian limestone, sandstone, r _marble

—

Snoring
sounds
2 apices

Percussion dull
left u p p e r

—

Belgian limestone, sandstone (not much)
Belgian limestone

—

4
5

34
35

21
23

—

Snoring
sounds

Belgian limestone
Belgian limestone, sandstone (not much)
Belgian limestone, marble
(not much)
Sandstone, Belgian limestone, granite

7 53

Sandstone, Belgian limestone, granite
Belgian limestone

Belgian limestone

13 46

Belgian limestone, granite, sandstone
Sandstone, Belgian limestone
Belgian limestone, marble
(very rarely)
Belgian limestone, sandstone
All kinds of stone

1
2

Snoring sounds

—

Snoring sounds

—

Snoring sounds

Percussion dull
left upper
Snoring sounds

•—

W e a k breathing right
As in 1923

—

Percussion
dull left

Heightened
breathing

—

•—

Snoring sounds

Snoring
sounds right.
Weak
breathing
Percussion
dull, right
upper

•

—

Belgian limestone, marble, Snoring sounds,
sandstone
weak breathing
All kinds of stone
Snoring sounds
Belgian limestone, sandstone
Belgian limestone, sandstone (rarely)
Belgian limestone, sandstone (rarely)
Sandstone, Belgian limestone
Belgian limestone, sandstone
Sandstone, Belgian limestone
Marble, Belgian limestone,
sandstone (seldom)

—
Bronchial
breathing
right

—

Snoring sounds

—

•

—

Snoring sounds

Heightened
breathing
left upper

•

Marble, Belgian limestone,
sandstone (seldom)

First stage : hilum shadows and linear shadows (and reticular).
Second stage: mottling.

SILICOSIS IN THE NETHERLANDS

525

X-ray results
Various observations
1923

1926

1929

—

Stippled
lung 2

Snowstorm
lung 3
1st stage
(incipient)
Stippled lung

1923-29, Belgian limestone worked.

Stippled lung
Stippled lung

Same kinds of stone as before 1923
Same kinds of stone as before 1923

1st stage
(incipient)
Same

Same

Same kinds of stone as before 1923

Same

1923-29, Belgian limestone; cough

Same

1923-29, Belgian limestone,
worked
1923-29, Belgian limestone

Same

More linear
shadows
Same

1st stage
(incipient) '
—

1st stage
(incipient)
1st stage
(incipient)
1st stage
(incipient)
1st stage
(incipient)
• 1st stage
(incipient)
1st stage
(incipient)
1st stage
(incipient)

1926-29, marble worked

Same
Same
Stippled lung

More linear
shadows
Same
1st stage

Same kinds of stone as before 1923

marble

1923-29, Belgian limestone, sandstone
1926-29, Belgian limestone, not much
sandstone
1923-29, no stone cut
For 2 y2 years short breathing, same
kinds of stone
1923-29, same kinds of stone

Stippled lung

Same

1923-29, Belgian limestone, sandstone

Stippled lung
Stippled lung

Same
Increase

Same
Same

<• 1923-26, Belgian limestone and marble
1 1926-29, sandstone
1926-29, Belgian limestone worked

Stippled lung

Same

Same kinds of stone as before 1923

Stippled lung

Same

Stippled lung

Same

In 1926 left more linear shadows, same
kinds of stone
Same kinds of stone as before 1923

Stippled lung

Same

1926-29, all kinds worked

Stippled lung

Same

1926-29, sandstone worked

Stippled lung

Same

Increase
stippled lung
Same

Stippled lung

Same

Same kinds of stone as before 1923

Stippled lung

Same

1926-29, Belgian limestone, marbled
worked

1923-29, sandstone, Belgian limestone

• Third stage: shadows as first and second stage and nodular shadows, large close mottling.

526

PAPERS PRESENTED TO THE CONFERENCE

1923

Kinds of stone worked in order
Years
of working
from youth onward
Age in
occubefore 1923
pation

Clinico-physical results
1923

1926

1929

Same

26 42

27 36

Belgian limestone, much
Weakened
breathing apices
sandstone
Sandstone (much)

28 61

Marble

29 43

All kinds of stone

30 47

Snoring sounds

31 44

Belgian limestone, not
much sandstone
Belgian limestone, sandstone

Snoring sounds

More
snoring sounds

32 61

Snoring sounds

Same

33 56

Belgian limestone, sandstone
Sandstone, Belgian limestone, marble

Weakened
breathing

Same

Snoring
sounds and
percussion
dull
Percussion
dull upper
Same

34 40

—

Much sandstone

Percussion
dull right

Snoring sounds Percussion dull
both apices
Snoring sounds

• — -

Snoring
sounds
Snoring
sounds left
lower back
and
weakened
breathing

with dry stone 58.7 and 87.3 mg. ; in working dry Belgian limestone,
58.5 and 159.4 mg. per cubic metre of air.
Teleky 1 reports a typical case of silicosis ( " snowstorm lung "),
notwithstanding that the stone was worked in a moist condition,
affecting a stonemason, who had worked on moist sandstone for
fourteen and a half years.
Kinds of Stone Worked according to Quartz Content
It has already been mentioned that the stones worked by stonemasons in the Netherlands are sandstones free from lime, sandstones
containing lime and limestones with varying lime content, including
Belgian limestone and marble, and also granite.
On the first general examination of stonemasons in 1923 it was
found that the working of sandstone had gradually diminished,
on the two later periodical examinations that Belgian limestone was
chiefly worked, and also marble and granite, and to a lesser extent,
1

TELEKY:

Reichsarbeitsblatt,

1929, N o . 26, I I I , p . 229.

527

SILICOSIS IN THE NETHERLANDS

X-ray results
Various observations
1923

1926

1929

Snowstorm lung
(incipient)
Snowstorm lung

Same

Increase

Increase
since 1923

Increase

Snowstorm lung

Increase

Snowstorm lung

Increase

Same
as in 1926
Increase

Short breath, habitual cough,
no sputum, only marble
1923-26, much sandstone; 1926-29, all
kinds, short breathing, cough

Snowstorm lung
(incipient)
Snowstorm lung

Same

1923-29, Belgian limestone and granite

Same

Increase

1923-26, sandstone 1 year; 1926-29,
all kinds of stone; before 10 years
sandstone

Snowstorm lung
(incipient)
Snowstorm lung

Same

Increase

Snowstorm lung

Same

1923-26, sandstone, half year,
1926-29, Belgian limestone
1923-29, no stone worked

1923-26, sandstone
1923-26, Belgian limestone and marble;
1926-29, Belgian limestone and sandstone; cough, short breath
Percussion over both lungs slightly dull ;
1923-29, sandstone

sandstone. A new kind of sandstone worked in recent years is the
Nivelstein * sandstone already mentioned, in which the quartz
grains are held together by a quartz-like cement and not by lime,
clay, iron oxide, glauconite, or other cements 2. The Netherlands
sandstone from Kunrade is very rich in quartz. An analysis showed
sand and insoluble silicates 54.17 per cent., calcium carbonate
39.6 per cent., clay and iron oxide 4.8 per cent., and traces of
magnesium carbonate. No special experience as to the danger
of the working of this kind of stone exists as yet. The hardness
of sandstone is determined by the size of the granules and the
nature of the cement. If the injurious agent in the various morbid
changes in lung tissue presenting the clinico-radiological character
of silicosis is held to be quartz, Si0 2 , it is important to know the
quartz content of the kinds of stone in use in order to form an
1
2

Onderzoek Technische Hoogeschool, Delft.
THIELE and SAUPE:

" D i e Staublungenerkrankungen

der Sandstein-

arbeiter". Schriften aus dem Gesamtgebiet der Gewerbehygiene, Neue Folge,
1927, No. 17.

528

PAPERS PRESENTED TO THE CONFERENCE

opinion as to the danger to health in working these various kinds of
stone. . This applies to the various kinds of Belgian limestone,
other limestones, and also to marble and various kinds of granite.
The following analysis is given of limestone of Belgian origin:
CaC0 3 95.67 per cent., Si0 2 2.56 per cent., and small quantities
MgC08 and Fe 2 0 3 .
The Maastricht limestone (Netherlands) already mentioned
contains, according to a three-fold analysis, chiefly calcium carbonate and also Si0 2 in quantities from 0.38 to 2.25 per cent. The
Kunrade limestone also contains only small quantities. Shell
limestone, a limestone with pipe clay as cement, is practically
speaking free from quartz according to German analyses 1.
Marble 2 may contain quartz, according to an analytical examination by Riddell and Rothwell of the dried lungs of a marble
worker; the ash contained on analysis 2.34 per cent, quartz, while
that of the lungs of town dwellers contained 0.60, 1.28 and
2.67 per cent.
Granite 3 from the Fichtelgebirge (Germany) contains 30 per cent.
quartz without cement, the quartz being found between the
other constituents.
Comparison of the X-ray Photographs in a Number of Cases of the
Same Stonemason Examined in 1923,1926 and 1929
For the purposes of this comparison thirty-four cases have
been selected which present a compendious picture. The X-ray
photographs were taken in the same consulting offices for tuberculosis in Amsterdam, The Hague and Utrecht. The medical
examinations were conducted by the same doctors.
The number of years in the occupation varies, as shown by the
subjoined table, from fifteen to fifty years. From the abovementioned report of 274 X-ray photographs taken in 1923, it
appears that affections of the lungs demonstrable by X-ray examination only appear after five years' stonemason's work, and
between the fifth and tenth years, and in increasing degree up to
thirty to forty years' work in the occupation.
In the column indicating the kinds of stone worked these are
mentioned in the order in which they were worked from youth
onward.
1
2
3

Ibid.
Journal

of Industrial

Hygiene,

KOELSCH and KAESTLE:

M a y 1928, p . 147.

Die gewerbliche

S u p p l e m e n t No. 15 to Zentralblatt

Staublungenerkrankung

für Gewerbehygiene,

p . 72.

1929.

SILICOSIS IN THE

529

NETHERLANDS

The particulars of the clinico-physical results give a compendious
statement of the relatively few phenomena in general.
From this table it will be seen t h a t before 1923 2 out of the
34 stonemasons had worked sandstone alone all their lives, 4 had
worked successively sandstone and Belgian limestone, 16 Belgian
limestone and sandstone, 4 Belgian limestone only, one Belgian
limestone and marble, 1 marble only, and 6 sandstone, Belgian
limestone and granite.
In the period 1923 to 1929, the number of sandstone workers
increased to 4, the number of Belgian limestone, limestone and
marble workers together from 6 to 11. The increase of silicosis
from 1923 to 1929 appears from the following:
Year

No affection

Stage I

Stage II

Stage III

1923
1929

8
9

11
15

9
10

Out of 6 stonemasons (Nos. 1 to 6) with no signs of affection
in 1923, No. 1 worked from 1926 to 1929 on marble alone, before
that chiefly on Belgian limestone, and to a small extent on sandstone,
and in 1929 was shown to have a snowstorm lung. Stonemasons
Nos. 3 and 4 worked before and after 1923 on Belgian limestone
only, and in 1929 each had a stippled lung, while stonemason
No. 5 showed practically the same symptoms after a large amount
of work on Belgian limestone and a small amount on sandstone
both before and after 1923. Out of the above 34 cases, not one
appears to have improved, even where, as in cases 12 and 27, no
stonemason's work was carried out for as long as six years. On the
contrary, a change for the worse is observable in case No. 27, who
had previously worked considerably on sandstone, notwithstanding t h a t he worked no stone at all from 1923 to 1929, while in
case No. 28, who had worked all his life exclusively on marble, and
in 1923 already showed signs of a snowstorm lung, an aggravation
was observable in 1926. Altogether, 18 out of the 34 cases are shown
to have become worse either in 1926 or in 1929.
Stonemason No. 22 shows in 1929 an aggravation of his stippled
lung after working on sandstone from 1926 to 1929 and previously
on sandstone and Belgian limestone, while No. 32 shows similar
phenomena, at least to the eye, and the same is the case with
No. 34, who had worked largely on sandstone all his life. It is
34

530

PAPERS PRESENTED TO THE

CONFERENCE

worthy of remark that out of the 9 stonemasons presenting the
typical phenomenon of snowstorm lung, 1 had never worked on
sandstone, 2 only on sandstone, and the other 6 sometimes Belgian
limestone and sometimes sandstone, and, to a small extent, granite.
Influence of Various Kinds of Stone
From the X-ray photographs taken in connection with the
general examination of stonemasons in 1923, a number have been
selected relating to stonemasons who in the course of their lives
had worked on certain kinds of stone and others who had worked
on more than one kind of stone, for comparison of the condition
of the lungs in connection with the number of years' employment
in the occupation 1.
KINDS OF STONE WORKED AND NUMBER OF YEARS' EMPLOYMENT
IN
Condition

of the Lungs

10-20
20-30
30-40
40-50
50-60

No
affection I

Stages

1
1

1
2
1
2

16
1

No
. SecII I l l tion I

as shown by X-Ray

Belgian
limestone

Sandstone
Years
in
occupation

OCCUPATION

5
1

1
7

9
9
4
1
1
24

Sandstone, Belgian limestone,
granite

Marble

Stages

No
affecII I l l tion

7 1
14 5
9 3
5 2
2 37 11

Examination

1
1
2

2
1
1

Stages

No
affecII I I I tion I

_
-

1 - 1
6

Stages
II I I I

12
3
15 20
8
6
3
3

38 32 15

1
3
1

5
4
6

Among these 90, there are 3 cases of silicosis + tuberculosis (sputum positive).

From the above table it appears that out of 16 sandstone workers,
2 were already in the second stage and 5 in the third stage of silicosis
after twenty to thirty years' employment in the occupation, as
compared with the Belgian limestone workers, among whom, out
of a total of 74 stonemasons, after the same number of years'
employment in the occupation, only 5 were in the second stage
and none in the third stage. Among the 90 stonemasons who
worked various kinds of stone, thus including sandstone, the pro1

These photographs are reproduced after p. 534.

SILICOSIS IN THE NETHERLANDS

531

portion is more unfavourable than in the case of the Belgian
limestone workers, taking the third stage as the test, although
relatively favourable in comparison with the sandstone workers.
A striking fact is the large number of Belgian limestone
workers (18) showing no affection after ten to thirty years' employment in the occupation, as against only 4 stonemasons working
on all kinds of stone.
The third stage of silicosis is found among Belgian limestone
workers in smaller numbers (2) after forty to sixty years'
employment, and therefore after a greater number of years'
employment than in the case of sandstone workers (7).
One question that arises is: why, in a particular case, the working
on sandstone only produces no silicosis, and the working on Belgian
limestone, with a low quartz content and much lime, does
produce it ?
Workplace and Manner of Living
The condition of workplaces, although improved in many cases,
still leaves much to be desired.
The stonemason's manner of living, compared with an earlier
period, twenty to thirty years ago, has changed for the better,
especially as regards abuse of alcohol. The irregular life of a
stonemason working at piecework in company with others of
youthful years, away from their homes, with insufficient rest at
night, and abuse of alcohol, has injured the health of many for the
rest of their lives. At the first general examination in 1923, 194 of
the 963 stonemasons examined stated that they had drunk a great
deal of alcohol in their youth.
A number of stonemasons have died during or shortly after work
in the restoration of churches and other monumental buildings
in which large quantities of sandstone are worked.
Dust Goggles and Respirators
Dust goggles or respirators are seldom used and certainly not
regularly.
The wearing of a respirator while engaged in strenuous work
becomes burdensome in the long run. By way of experiment a
stonemason wore a respirator every day for a month during his
work. After a certain time, the pores were stopped up with stone
dust clogged together with the moisture from breathing.

532

PAPERS PRESENTED TO THE CONFERENCE

INSTRUCTION OF STONEMASONS

Under section 9 of the Stonemasons Act, 1921, provision is made
for instructions respecting the nature of the dangers to which
stonemasons are exposed, and in regard to which precautions are
to be taken ; the printed instructions must be affixed in the workplace and a copy on a smaller scale delivered to the stonemason
personally. In addition to this, since 1923, in most of the large
towns lectures have been delivered and discussions held by the
medical adviser and the medical practitioners attached to the
factory inspectorate.
The use of sandstone alone as little as possible remains of
great importance.
ASSIMILATION TO ACCIDENTS FOR THE PURPOSES OF COMPENSATION

Preparations are being made for the assimilation of this occupational disease to an accident in pursuance of section 87 (a) of the
Accident Act, 1921, as amended in 1928 1.
CONCLUSIONS

The introduction and application of the Stonemasons Act has
led to a clearer insight into the character of the " stonemasons'
disease " and a more intelligent procedure in combating it by the
improvement of the working conditions and personal hygiene
of stonemasons.
The preliminary medical examination and annual re-examination
of young stonemasons to a considerable extent prevents persons
suffering from lung tuberculosis entering upon and continuing in
stonemasons' work.
The periodical (three yearly) medical examination of adult
stonemasons has shown the indispensability of X-ray examination
for forming an opinion of lung affections.
The working of sandstone alone must be regarded as more
injurious to the lungs than the working of limestone alone. The
working of sandstone alone does not always lead to symptoms of
silicosis and, on the other hand, the working of limestone alone
(Belgian limestone, marble) does not prevent silicosis in a serious
1

Staatsblad No. 223, 1928.

SILICOSIS IN THE NETHERLANDS

533

form. The working of sandstone and limestone alternately appears
to produce less serious results in the same period than the working
of sandstone alone.
Compulsory medical examination both in the form of preliminary
examination and periodical re-examination should be introduced
for sand-blowers as well as for stonemasons.
Silicosis as an occupational disease of stonemasons should be
assimilated to an accident for the purposes of the application
of the Accident Act.

APPENDIX
Silicosis and Sand-Blowing
Considerable use is now made in industry of the sprinkling of quartz
sand (river sand) on metal objects for the purpose of cleaning and in the
etching of glass. Sand-blowing is carried out by blowing fine dry sand '
from a pipe under air pressure, the pipe being directed by hand on to
the piece of work and the worker standing in a closed room with his
eyes and face protected by a dust helmet into which fresh air is introduced from without by a tube at the back. In cleaning smaller objects
the latter are carried in a closed box with a glass front along the stationary blow pipe, while the worker outside the box directs the pipe on to
the object to be cleaned, his hands and arms being placed in leather
or rubber gloves with armpieces attached to openings in the front of the
said box.
The dust helmet is burdensome when working for a long time continuously at blowing and is therefore frequently taken off, when the
continued scattering of dust by other workers in the same room leads to
unavoidable inhalation. The wearing of a suitable respirator for a short
time might be used as a remedy for this. A forty-four-year-old sandblower in an engineering works died after three years' employment on
such work. On the post-mortem examination silicosis was found to be
present in an advanced stage, but there were no signs of tuberculosis.
The man had frequently worked without a helmet. In the blowing
of sand on metal objects it is beaten to a fine powder and the raising
and dispersion
of dust is enormous. It is well known that serious lung
affections 2 in the form of silicosis in its various stages arise also among
this class of workers. In a cycle factory in the Netherlands an X-ray
photograph was taken of a worker who complained of shortness of breath
and the result showed the characteristics of snowstorm lung, although
the man had inhaled no dust during the last few years but had previously
done so in considerable quantities.
1
Steel granules are not used (Centraal Verslag der Arbeids ins pectie Nederland, 1925).
2
Zentralbl. für Gewerbehygiene, May 1928, p. 149.

534

PAPERS PRESENTED TO THE CONFERENCE

The quantities of SiOa that a lung can contain appear from an analysis
of the dried lungs of a sandblower by Riddell and Rothwell ', in which
16.83 per cent. SiOa was found.
There has been no regular medical examination of sandblowers in
the Netherlands, nor yet in Germany 2.
In the work already referred to, Das Sandstrahlgebläse, the measures
for preventing the injurious effects arising from the use of sandblowing
apparatus are particularly described.
On a lesser scale than in industry sandblowing is used in the cleaning
of the fronts of buildings. By this process brick, sandstone and limestone
are restored to their natural colour. To prevent the dispersal in the
surrounding space of the dust from the powdered sand, a large awning
is suspended from 1 to 2 metres from the front, so that the worker who
remains for a long time in a thick cloud of dust is insufficiently protected
by his mask. In this case also signs of pneumonoconiosis in a serious
form are found.

Loe. cit.
Das Sandstrahlgebläse : Schriften aus dem Gesamtgebiet der Gewerbehygiene, 1928, Neue Folge, No. 21, p. 45.
2

tía

f^mmmm^ím^mi:iamM^^^*^'¡Wi

FIG.

Silicosis in Hie Netherlands.
[To face p. 534.]

FIG.

FIG. 3. — Stonemason at work (in good sitting position).

X-Ray Photographs of Various Cases

III

D. J., No. 29: 43 years of age; 27 years stonemason in 1923, before and after that date worked
all kinds of stone.
X-ray photo. I: snowstorm lung, 1923. I l l : snowstorm lung, 1929, increased.

III

Ph. G. M., No. 27: 36 years of age; 21 years stonemason in 1923; before that date much sandstone;
from 1923 to 1929 did not work in stone, nevertheless increased.
X-ray photo. IT: snowstorm lung, 1926, increased. I l l : snowstorm lung, 1929, increased.

Ill

I
A M., No. 23: 44 years of age; 30 years stonemason in 1923. Before and after, sandstone and Belgian limestone.
X-ray photo. " I: stippled lung 1923 (2nd stage). I l l : stippled lung 1929, remained the same since 1923.

A. V., No. 11-: 27 years of age; 14 years stonemason in 1923; before then all kinds of
stone; after then not much sandstone.
X-rav photo : incipient fibrous lung (1st stage)
1926, the same as in 1923 and 1929.

J. F. S. : 44 years of age; 32 years stonemason
in 1923, before then all kinds of stone;
died 1925. On post-mortem = silicosis
+ tuberculosis.
X-ray photog.: silicosis (3rd stage), right
more than left.

J. J. W.: 64 years of age; 52 years stonemason in
1923; before and after, Belgian limestone only.
X-ray photo: snowstorm lung.

P. V.: 61 years of age; 49 years stonemason in
1923, before and after, marble only.
X-ray photo : snowstorm lung 1926, increased
after 1923, and remained the same in 1929.

VIH

F. v. B.: 44 years of age; 30 years stonemason in 1926,
before and after, only sandstone.
X-ray photo : no affection.

SILICOSIS

THE

UNITED

BY DR. ALBERT E.
OF

THE

UNITED

STATES

RUSSELL,

PUBLIC

HEALTH

SERVICE

INTRODUCTION

Silicosis is rather widespread in the United States: it has been
found to exist with a rather high incidence in a number of industries.
There are other industries in which only a few workers are occasionally
exposed to siliceous dust, but in which the effect of the exposure in
these few dusty occupations is great enough to produce silicosis in a
moderately advanced condition in a short time.
The principal industries in which silicosis occurs in its greatest incidence are enumerated below. It is not implied that all the workers
in these industries are exposed to excessive amounts of dust.
Mining :
Anthracite coal
Bituminous coal
Gold
Silver
Zinc
Lead
Copper
Quarrying :
Granite
Sandstone
Limestone
Slate
Flint
Rock crystal (quartz)
»Stone (finishing) :
Granite
Sandstone
Building stone (various grades)
Pottery :
Emery wheels
Carborundum

Abrasive :
Sand
Sandpaper
Grinding
Glass
Mineral earth:
Silica flour
Sand
Spray coating:
Plumbing materials
Refractories :
Silica bricks
Construction :
Railways
Highways
Tunnels
Rock drillers in general

536

PAPERS PRESENTED TO THE

CONFERENCE

A number of occupations in industries are productive of dust, while
the general nature of the industry in which it is carried on might not
indicate that any dust hazard was prevalent. These are enumerated
here:
Sand-blasting
Moulding (ores)
Grinding

Buffing
Cleaning
Polishing

There are numbers of dusty industries and occupations in the
United States which do not necessarily present silica hazards, but
they have an excess of dust, and in most of them silica is found in
a small percentage, and no doubt plays its role in causing an excessive
morbidity from respiratory diseases. Some of these are enumerated
here:
Cement
Marble

finishing

Graphite
Coal cleaning

Smelting :
Textiles :
Steel
Cotton
Copper
Woollen
Lead
Zinc
Grain elevators:
Construction:
Wheat
Building
Oats and other grain
House wrecking
Studies on the problems of dust removal are being made in laboratories at Harvard, Yale, and other universities. Much valuable work
in this direction has been done by the U.S. Bureau of Mines at laboratories in Pittsburgh and in mines. The manufacturers of exhaust
and ventilating equipment have also contributed greatly by study and
experimentation to the improvement of dusty conditions in industry.
A very valuable experiment is being carried on in mines in Oklahoma.
The Bureau of Mines, the Metropolitan Life Insurance Company, and the
State of Oklahoma have combined to study the effects and remedies
of the dust hazards encountered in mining.
The United States Public Health Service has made studies of certain
industries to cover the various types of dust:
1.
2.
3.
4.
5.
6.

The cement industry, representing calcium dust.
Silver polishing, representing metal dust.
The granite industry, representing silica dust.
The coal industry, representing carbon dust.
The cotton industry, representing vegetable dust.
Street sweeping, representing municipal dust.

These studies have been completed and two have been published ;
others are in p ocess of preparation.
Some of the industries wheie silicosis has been found in excess are
briefly reviewed here.

SILICOSIS IN THE UNITED STATES

537

MINING

Mining is one oí the largest industries in the united States.
It is widespread, being carried on in some measure in practically
every State. Silicosis is a hazard which seems to be common to
most mining operations. Its incidence and severity vary according
to the variety of dust encountered and its concentration.
The efficiency of exhaust systems throughout the different mines
varies greatly. Many companies are keenly interested in providing
exhaust systems, and others give more attention to other problems.
The principal groups of mines in the United States are those
producing the following ores:
Coal
Copper
Lead
Zinc

Iron
Aluminium
Gold
Silver, etc.

During recent years there has been much more machinery
employed in mining than formerly, most of which is impelled by
compressed air or electricity. These newer methods have increased
the dust hazards to an appreciable degree. The coal miners, for
instance, are reputed to have more pneumonoconiosis in recent years
than in the days when mining was accomplished by older methods.
The United States Bureau of Mines has been a very valuable
agency in assisting in the alleviation of dust and other hazards in
mines. The Bureau maintains a very excellent laboratory at
Pittsburgh and at experimental mines near by. The Bureau
workers have co-operated with mine operators and other agencies
and are rendering a service which would otherwise be unobtainable.
The chief surgeon and other medical personnel of the Bureau of
Mines are supplied by the United States Public Health Service.
Coal Mining
Coal is produced in thirty of the forty-eight States and in
Alaska. Six of these States produce less than 100,000 tons
annually.
There are two varieties of coal produced in the United States,
viz. anthracite and bituminous.
Anthracite Coal
Anthracite coal is produced in Pennsylvania. There are other
deposits of anthracite (or near-anthracite), but these are not great

538

PAPERS PRESENTED TO THE

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enough to produce in paying quantities. There were 157,743 wage
earners in the anthracite coal industry in 1923 (U.S. Census).
These were located in three counties in Pennsylvania.
Anthracite coal occurs in Pennsylvania in large veins and at
varying depths. In earlier days there were out-croppings, which
were mined with steam shovels in pit mines, but at present the
mines are all underground. The mine shafts and tunnels are large
and afford good opportunity for general ventilation. Anthracite
coal has been produced on a large scale longer than bituminous
coal.
The rock which is associated with anthracite coal contains
31 per cent, of free silica, and the possibilities of the occurrence
of silicosis are obvious. The following table gives the percentage
of silica in several industrial dusts which we have studied.
TABLE I.

CHEMICAL AND PETROGRAPHIC ANALYSIS OF THE DUST
IN EACH

Silver polishing:
Hollow-handle making room
Wet pumice (two samples averaged)
Brass foundry
Cement:
Pack house
Crusher house, raw mill, stone house
Soft coal (bituminous) :
Coal dust
Rock dust
Hard coal (anthracite) :
Coal dust
Rock dust
Granite :
Average

STUDY

Total silica
(Percentage)

Quartz
(free silica)
(Percentage)

22.2
70.5
73.3

1.7
Less than 0.5
19.0

21.2
16.8

Less than 1.0
6.5

1.2
54.0

High
?

High

1.5
31.0

70.0

35.2

The anthracite miners develop acute bronchitis and, later,
emphysema and miner's asthma. These chronic conditions,
together with the effect of some rock dust, make it very difficult,
even for those who are specialised in tuberculosis, to diagnose
pulmonary tuberculosis. Obviously, tuberculosis is easily overlooked among coal miners. Routine sputum analysis will often
give information as to whether or not a tuberculous infection is
present.
The dust counts made in the anthracite mines studied by the

SILICOSIS IN THE UNITED STATES

539

Public Health Service showed that the dustiness encountered
by workers in the various occupations averaged as follows :
Miners and mine labourers . . . .
Rock workers
Drivers and runners
Others

Million particles per cu. ft.
124.2
81.9
36.5
2.3

It was shown by pétrographie analysis that a sample of coal dust
from the anthracite mines contained 1.5 per cent, of crystalline
silica as quartz.
The incidence of tuberculosis among coal miners has been a
much debated subject; we found among those included in our study
that tuberculosis did occur. In considering the causes of deaths
from 1906 to 1926 in Wilkes-Barre, Pa., located in the heart of the
anthracite region (deaths from all external causes were excluded,
also data of the epidemic years), it was found that the cause of
11.4 per cent, of the deaths of coal miners was given as tuberculosis,
while 6.5 per cent, of the deaths of other adult males in the same
area was stated to be due to this disease (see figs. 1 and 2).
The earlier workers in anthracite coal mines in Pennsylvania
were principally from Wales and Cornwall, England. At present,
however, these people are in the minority, and Slavs and Southern
Italians compose the greater numbers. The morbidity records
which we have for a group of these miners show that alcoholism was
a frequent cause of absence from work.
Bituminous Coal
Bituminous or soft coal is found in larger quantities in the United
States than anthracite and is distributed over a much greater area.
The deposits are usually in " drifts ", for which reason the plan of
the mines is different from those of anthracite coal. Most of the
bituminous mines are entered horizontally, usually from a mountain side. The overlying stratum is of sandstone in some of the
larger areas, schists and other varieties of stone in others. The
drifts are low in many places, and necessarily the chambers and
tunnels are small. This fact augments the dust hazards of bituminous mining. There were 545,798 wage earners in bituminous
coal mines in 1919 (U.S. Census). Much of the coal is cut with
machines and then loaded with shovels. Coal-loading machines
are being introduced—their use lessens the amount of dust. Rock
drilling is supposed to be done when the other operations are not
in progress. (From a previous table it may be seen that analysis

540

PAPERS PRESENTED TO THE CONFERENCE

shows that some of this rock (sandstone) contains 54 per cent.
of quartz.)
The following figures show the extent of dustiness to which each
one of these workers is exposed.
Coal cutter (machine operators)
Coal loader
Rock driller

Million particles per cu. ft.
. .
112.3
112.3
78.1

The pneumonoconiosis of the bituminous coal miners is quite
different from that of the anthracite miners, whose X-rays have
been shown herein. The bituminous miners have not had asthma
in the same incidence as the anthracite miners. In fact, miners'
asthma among bituminous miners is considered to be rare.
The incidence of tuberculosis, likewise, has not been shown
to be as great among bituminous miners as among anthracite miners.
It will be seen from the accompanying prints 1 that the pneumonoconiosis of these workers is apparently not so severe as that of
anthracite miners (film 3).
The coal is carried out of the mines usually by a small electric
train. The silica hazard in these mines is augmented by the use
of sand on the tracks of the coal trains ; the sand becomes pulverised
and the motion of the trains fans it into the air. In many of these
mines (especially the smaller ones) ventilation is accomplished
through the same tunnel, increasing the silica hazard by the diffusion
of this dust. Conditions could be alleviated by the use of a material
other than sand to increase the friction of the car wheels on the
track.
From the accompanying print it may be seen that the motormen
on these coal trains de^ eloped silicosis. No doubt the pneumonoconiosis of the other mine workers is influenced by this sand dust
(film 4).
Gold Mining
Gold is mined in California, Colorado, Nevada, South Dakota, and
Utah. It occurs in other States, also, but is not mined extensively
in those States. The mining is accomplished in California partly by
hydraulic methods which eliminate the silica hazard ; but as a rule
there is a silica hazard in all the gold mines in the United States.
Gold is invariably found deposited in quartzite rock, the percentage of quartz, however, varying in different localities. Silicosis
is known to occur in excess at most of the mines.
1

These prints are given after p. 562.

SILICOSIS IN THE UNITED STATES

541

It is said to occur with less frequency in the Colorado mines,
which are moist, and naturally less dust is created in the mining
process. The ore is found combined with volcanic rock which
contains more than 20 per cent, of quartz. The altitude of these
mines is above 10,000 feet, and belief is held by some that the
cases of silicosis eliminate themselves because of dyspnoea, the
affected workers seeking lower countries before diagnosis is made.
In Utah the mines are hot, and cooling air must be supplied for
the comfort of the workers. The heat dries the mines, thus
augmenting the dust hazards. The workers in these mines are
reputed to have a high incidence of silicosis.
One of the oldest and largest gold mines in the United States
is located in the Black Hills of South Dakota. The sick-benefit
association of this mining company has reported the illness (eight
days or longer) of its members to the Public Health Service over
a period of five years. When the rates of illness among these gold
miners are compared with those of other sick-benefit associations,
it is found that the miners have 2.5 times as many respiratory
attacks as the other groups. When the comparison is made in
regard to each condition, it is found that influenza and grippe are
3.7 times as great among the miners. The outstanding condition,
however, is pulmonary tuberculosis, which has an incidence
8.7 times as great as that of the other groups. This finding was
to be expected, since we know that the workers are exposed to
excessive amounts of a highly siliceous dust. No doubt these cases
of tuberculosis are complications of silicosis, although we have no
examinations of X-ray prints to furnish proof of this opinion.
Granite Manufacturing
The granite industry is one of the largest in the United States
in the production of stone. It is excelled only by the marble,
limestone and sandstone industries as to amount produced.
Granite is used in monumental work principally, while marble,
sandstone, and limestone are used more extensively as building
materials.
The manufacturing of granite into monuments requires more
manual labour than that of other stone, because of the extreme
hardness of granite. The softer stones (marble, sandstone, and
limestone) are easily manufactured with machinery, and much
of the dust hazard is thereby eliminated.
The large granite centres in the United States are located in

542

PAPERS PRESENTED TO THE

CONFERENCE

Vermont, New Hampshire, Maine, Massachusetts, Connecticut,
Rhode Island, New York, Minnesota, Wisconsin, and Georgia.
There are numerous other localities where granite is found, but
production is not carried on extensively in these places.
The hazard from granite is based upon its free silica (quartz)
content, which ranges from 25 to 35 per cent.
A report of a study made by the United States Public Health
Service of the dust hazard in this industry has recently been
published—Public Health Bulletin No. 187. In this study it was
shown that the workers engaged in finishing granite were exposed
to dust in the concentration of 40 to 65 million particles per cubic
foot (i.e. particles less than 10 microns in diameter). The general
plant atmosphere averaged 20 million particles per cubic foot.
TABLE II. —

CLASSIFICATION OF OCCUPATIONS INTO DUST COUNT
GROUPS
Average dust count.
(Million particles per
cubic foot)

Group

Occupation

Number
of men

Hand pneumatic tool operators
Carvers; letterers
Others

565
24
25

59.8
37.0

68
20
16

44.0
27.1

146

20.2

Surface machine operators
Tool grinders
Others

Lumpers
Boxers 8
Polishers
Cranemen
Bedsetters
Tool carriers
Mechanics
Labourers

Polishers 2
Sand blast operators
Sawyers
Blacksmiths
Others 8 (no specific dust count,
but low)

17
4
10
10

9.0 '
6.2
4.6
2.5

More than
average plant
dustiness

Average
plant
dustiness

Less than
average
plant
dustiness

1
Hand pneumatic tool cutters during most of their time in granite, but before or later
were
in other occupations.
2
All
in Group C, except in one plant (where they had a separate shed).
3
Occupations were: derrickmen (22), engineers (10), machinists (9), foremen, manufacturers (9), etc.

The workers were grouped according to the intensity of exposure
and are considered throughout the morbidity and mortality study

SILICOSIS IN THE UNITED STATES

543

in these groups. Groups A and B were exposed to averages
of about 27 million particles per cubic foot, and the average for
some in this group reached 60 million; Group C averaged about
20 million particles; Group D averaged 10 million or less. Table II
explains this classification.
Each part of the study (X-ray, physical examination, sickness
records, and mortality) showed a direct relation to the extent of
dust exposure and damage to the lungs and the extreme likelihood
of final superimposition of a fatal tuberculosis.

FIG. 1. — Persons with and without silicosis in the
four dust count groups, by length of service.

The physique of the granite cutters was every good, and they
usually remained in the industry after apprenticeship. Their
wages were good ($8-$20 per day), and they worked forty hours a
week for one half of the year and forty-four hours a week for the
other half. The living conditions were usually very good.
Pleurisy (dry) was a common finding among the granite workers,
The pulmonary disability (silicosis and tuberculosis) varied directly
with the length of exposure. There was a tendency for patients
about to break down with tuberculosis to have more respiratory
diseases than they had had before this period. Silicosis was found

544

PAPERS PRESENTED TO THE CONFERENCE

among many of the workers, in groups A and B after two years'
service ; after longer exposure silicosis occurred among them almost
universally. Fig. 1 explains the incidence of silicosis among the
various groups by length of service.
The amount of sickness from all causes showed a direct relation
to intensity of exposure to dust. The following graph shows that
length of service and intensity of exposure caused an increase in
the incidence of sickness in Groups A and B (fig. 2).

300

340
J 20
300
280
2i0

A — - ^
?•
y

/
/ A

200
180

/ /
/ /

100
•u

^ 0

220

100

/ /

Z40

120

'**••*">».

^" V .
^••^CondD

"N.

40
20
0

10
Experience

20
in G-romVe

30
(years)

FIG. 2. — Incidence of sickness from all causes
in the four dust count groups by length of service.
Eight days and more (rate per 1,000).

The following graph compares the frequency of sickness of
granite workers with that of certain other industrial groups.
The group " General Sick Benefit " is given to represent more or
less average industrial workers. From this graph it will be seen
that the workers in dusty trades have a much greater incidence of
all respiratory conditions (fig. 3).

SILICOSIS IN THE UNITED STATES

545

COMPARISON OF FREQUENCY OP ABSENCE DUE TO
SICKNESS AMONG GRANITE WORKERS WITH T H A T IN
CERTAIN OTHER INDUSTRIAL CROl/PS -

FIG.

EICHT OAYS • - mow

The sickness rates from tuberculosis (superimposed on silicosis)
is next compared with those of other industries. Here we see the
great preponderance of the incidence of tuberculosis. In the same
graph the death rates of the various groups are compared with
those of adult males in rural Vermont. It should be noted that
the hard-rock gold miners used herein had not been in the industry
as long as the granite workers (figs. 4 and 5).
When tuberculosis became a complication of silicosis, it usually
made a rather sudden onset and pursued an unremitting course to a
fatal ending. None of the cases became arrested. The age at
death of these workers averaged 49 years, which included a few
who indoubtedly had a latent tuberculosis on entering the trade,
in which instance the disease resembled tuberculosis not complicated
by silicosis ; these latter cases, however, were few. It was difficult
35

546

PAPERS PRESENTED

TO THE

CONFERENCE

tas

70-

Annual frequency of
from
Tuberculosis

60
g SO
o

absences

C f i - h t ¿Ay» »"J

i; 4 0
«V.

m.-.)

§30
o
i 20
«j

a.
.«.io1.4
Granite
5 20
o

workers

HardrocX r
* ¡ron
CU
Cernen!. Steel
„„„

9 S CS) Annual death-rate
per 1,000
from
Tuberculosis

General
,,A
benefit

persons

S 15
§ 10
i.
u
a.

2.3
C
Heaths

Rural
Vermont
Age 20-59

» From beginning of study to working up of report—about three
years—among 972 workers: A, fil4; B, 104; C, 146; D, 108.

FIG. 4. — (A) Annual frequency of absences from tuberculosis (eight days and
I." more) ; (B) Annual death rate per 1,000 persons from tuberculosis.
GO
Pneumatic
Tool
Cutters —

L 40

v
O.
«I
I.

«JO

£
^20
s

<»r
10

FIG. 5. — Age curve of mortality from tuberculosis among hand-pneumatic
tool cutters and in rural Vermont (males).

SILICOSIS IN THE UNITED STATES

547

to obtain specimens of sputum for analysis, but when the sputum
was examined, it was usually found that the first specimen contained
tubercle bacilli in great numbers. The length of a case of tuberculosis among these workers was usually about fifteen months, and
termination was always death.
Tuberculosis occurred in the families of granite workers, but
perhaps less frequently than in general practice, because of the
excellent hygienic conditions of their homes; and also, the disease
came on at an age (about fifty) when the children were no longer
little, many of them being either grown up and at work or away at
school.
Pneumatic tools were first employed in the granite industry
about the beginning of the present century, and the tuberculosis
rate has increased rapidly with their use. It is doubted if the
maximum rate of tuberculosis has been reached. Since the
introduction of the pneumatic method the rate has risen in proportion to the length of time for which they have been used, as
follows:
1.5 per 1,000 . .
10.8 „
„
. .
19.5 „
„
. .

1890-1894
1910-1914
1924-1926 (period of study)

Studies were made of many of the exhaust and ventilating
systems in use in the local plants, and in no instance were they
found to be adequate. A plant in another city was found to have
an excellent system, by which, if it were properly maintained and
operated, a safe atmospheric condition could be obtained. A
paper on " The Efficiency of Dust-Removal Systems used in
Granite Cutting " was presented in Public Health Reports,
18 October 1929. This paper gave specifications for exhaust and
ventilating systems, together with dust counts found under
varying conditions.
The accompanying X-ray pictures show silicosis and tuberculosis
complicating it in granite workers. Tuberculous lesions in the
base of the lung (usually right) were found as a rule among these
cases. (See bulletin.) (Films 5 and 6.)

Granite Quarrying
Much of the quarrying of granite is accomplished by a wet
process, and very little dust is generated. The worker is able, too,

548

PAPERS PRESENTED TO THE CONFERENCE

to stand away from the pneumatic drill, which is attached to a
stand. After being removed, the stones must be split into smaller
sizes, and some dust in encountered here, but perhaps not in
quantities sufficient to produce marked silicosis, and quarry
workers in granite are certainly not reputed to have a high incidence
of tuberculosis.

Cutters
60

Lumpers
Monufocture

rS
Other occupations
in Granite
industry

rhlishers

Tool grinders

^30

Quarry

fteoistrotion am
'l^aS-9
Occupied
males

FIG. 6. — Proportionate mortality from tuberculosis l
in specific occupations of granite industry compared
with data for occupied males. Registration Area, 1908-9.
1

Many were previously granite cutters.

The precaution taken to keep down dust in granite quarries is
the provision of hose and water to keep the drill moist during the
cutting operations. The splitting of the blocks is accomplished
out in the open and usually after the stone has been removed from
the quarry pit.
Sometimes a stone finisher will change his occupation to
quarrying, and should he develop silicosis, its background might be
his former occupation. A careful occupational history is necessary
before silicosis can definitely be accredited to the occupation which

SILICOSIS IN THE UNITED STATES

54Q

the worker followed immediately before his illness. Although the
quarry worker in granite handles siliceous materials, it is thought
that the hazard from dust is small.
It may be seen from the graph on page 548 (fig. 6) that the deaths
of quarrymen from tuberculosis were less than those of occupied
males in the registration area in 1908-1909.

MARBLE

Vermont, Georgia, and Tennessee are the principal marble
producing States. Vermont was the pioneer in production of large
amounts. Marble dust contains about 1 per cent, crystalline
silica, with about 98 per cent, calcium. No silicosis has been shown
among these workers. The Vermont State Sanitarium for Tuberculosis is only a few miles from one of the largest marble works, and
according to its records, marble workers (unless they have
previously worked in granite) are seldom admitted to the institution
for treatment. Dr. E . J . Rogers, physician in charge of institutions
and clinics for tuberculosis in Vermont, states that these workers
rarely have tuberculosis. The calcium present in marble dust may
be a factor in causing such a low incidence of tuberculosis among
this group of workers. Tuberculosis has likewise not been reported
to be in excess at other (newer) marble centres.
(Vermont marble must not be confused with Vermont granite.)

SANDSTONE

The sandstone industry in the United States centres in and around
the States of Ohio and Indiana. The contact of the worker with
the stone in quarrying and finishing is not so close as in the case
of granite. Sandstone is less resistant and can be made into
fiinished products by machinery much more easily than granite.
Therefore it would not be supposed that workers in sandstone
would be exposed to as much dust as granite workers. Certainly
they are exposed to much less dust than miners, since much of
their work is accomplished above ground and in the open.
A study which was made in one of these quarry sections was
reported in the Journal of Industrial Hygiene in September 1929
(Vol. II, No. 7). Of 919 workers, 409 were found to be negative

550

PAPERS PRESENTED TO THE CONFERENCE

for silicosis. The median age, however, of this negative group
was twenty-seven years, and the average time of exposure to dust
was less than four years. It was shown that by the time the
workers were thirty-six years old and had had an exposure to dust
of 7.41 years that 238 had " increased fibrosis ". The incidence
of silicosis increased with age and length of exposure, and the
number of cases of tuberculosis also increased likewise. If these
findings exemplify the silicosis hazard in the sandstone industry,
we see that this hazard constitutes quite a health problem. The
incidence of tuberculosis as a complication of silicosis in sandstone
workers is much less than in the granite stone industry, being
obviously a matter of intensity of exposure. There were no dust
counts made in this study of sandstone, but from the nature of the
occupations in this industry it is certain that the granite workers
are exposed to much greater quantities of dust than this group
of workers.
SPRAY COATING

The number of workers in this occupation has greatly increased
in the United States in the past few years. There has been greater
demand for plumbing materials, incident to the construction and
modernising of homes, and the spraying of paints has in many
instances replaced the older methods of brushing. The tremendous
growth of the automobile industry has necessitated rapid methods
of painting.
A committee on spray-coating selected by the National Safety
Council recently studied the situation. Evidently lead is the main
hazardous material encountered in the spraying of paints, but
siliceous materials are occasionally employed. In the manufacturing of plumbing materials (bath-tubs, wash-basins, etc.), silica is
frequently encountered. Erroneous ideas have prevailed as to the
safety of " wet dust ", but such dust has been shown to be capable
of producing extensive silicosis. Vitreous enamel is stated to
contain 43 to 47 per cent, of silica (much of which is evidently in
the form of silicates). The committee recommends the use of a
bisilicate of lead, which would lessen the hazard from both silica
and lead. I he committee also urged adequate exhaust systems
for the spray booths and showed that with a poor ventilating
system the air contained 445 million particles per cubic foot and
that with exhausts of a better variety the counts showed only from
5 to 24 million particles per cubic foot.

SILICOSIS IN THE UNITED STATES

551

SAND BLASTING

The use of sand blasting in the industries has become very
widespread in the United States within a very short time. Many
large manufacturers find use for sand blasting in some of their
processes, whereas they have no other dusty trades.
From my own observations, I am convinced that sand blasting,
unless done under proper conditions, is capable of producing
silicosis more quickly than almost any other trade carried on in the
United States. The sand-blasting machinery producers have taken
cognisance of the great hazards of the trade and have instigated
research towards instituting methods of control. Equipment for
dust alleviation is available, but its efficiency depends upon its
design, its proper installation, and its maintenance. Recently,
blasting with steel grit has been tried, and obviously much less dust
is produced with this medium, but the result is not the same as when
sand is used; instead of a cut surface, more of a hammered effect is
obtained. More recently carborundum has been used and with
success. I believe that in time carborundum or other silicon
carbide products will replace the use of sand or fine pebbles.
There are more than 10,000 workers in the United States
employed in sand blasting, and as the labour turnover in this
trade is great, many more people are exposed. Because of the
delayed effect of silica dust in the lungs, it would be impossible to
estimate the role which sand blasting plays in mortality from
tuberculosis and other respiratory diseases.
Sand blasters nearly always use masks or helmets to protect
them from dust. In some cases the operator does not wear a mask,
but stands outside the cabinet and looks through a window and
operates the hose through an aperture covered with burlap. The
inadequacy of such equipment is great and cannot be too strongly
condemned.
The Public Health Service and the National Safety Council have
undertaken co-operative studies of sand blasting in the United
States. The complete report of this work will be published jointly
and will be available for distribution next year. The findings,
although not yet complete, show that the dust concentration in
two of the rooms in which counts were made reached 1,706.6 and
1,171.2 million particles per cubic foot. Helmets with positive air
pressure were worn by operators, and samples of air taken from
under the helmets contained 17.3 and 13.3 million particles per
cubic foot, respectively. This is above the standard set for granite,

552

PAPERS PRESENTED TO THE CONFERENCE

which is 10 million particles; also, sand contains a higher percentage
of silica than granite. That these are dangerous amounts is quite
evident, and forced ventilation of the sand-blast rooms is obviously
very necessary. The accompanying X-ray print and history are
from a patient who wore a helmet while at work (film 7).
The influence of positive pressure may be seen from the following
statements. The air of one. of the sand-blast rooms contained
894.7 million particles and the air from under the helmet with
positive air pressure contained 8.4 million particles per cubic foot.
A test was made in which the helmet was used without air supply.
The room dustiness in this instance was 1,568.0 million particles,
and the air under the helmet contained 437.7 million particles per
cubic foot.
Case of silicosis in a sand-blaster. Patient wore a mask.
W.M. : aged 46 years ; Mulatto.
Sandblaster 7 years.
History of past health showed no diseases of any importance. No
history of tuberculosis in family. Five years after this X-ray was
made, patient died of tuberculosis (tubercle bacilli in sputum). (Film 7.)
ROCK DRILLING

Rock drillers are exposed to rock dust, which dust is produced
in great quantities, by the pneumatic drills with which their work is
accomplished. Moreover, the workers are usually labouring in
" rooms ", tunnels, or pits where natural ventilation is of little
assistance.
Rock drilling is done extensively in the construction of highways,
railways, tunnels, and excavation for buildings. An engineer
engaged in inspection of construction work stated recently that on
the island of Manhattan (New York City) alone there were 20,000
rock drillers. The rock in which these 20,000 drillers are working
contains over 50 per cent, of quartz. This means that, when the
labour turnover is considered, over 20,000 persons a year are
exposed to dangerous amounts of silica. A study was made of
rock drillers engaged in subway construction on Manhattan island
and was reported in the Journal of Industrial Hygiene, February
1929. Fifty-seven per cent, of the workers examined were found
to have silicosis, and tuberculosis was found (by X-ray) to be
present in 9 per cent, of the cases examined.
Because of the insidious nature of silicosis the incidence of both
silicosis and tuberculosis will no doubt greatly increase among
these workers, inasmuch as they have undergone intensive exposure
to rock dust in recent years.
Attention is being given to methods of dust prevention, but

553

SILICOSIS IN THE UNITED STATES

the nature of the work and its frequent use in isolated situations,
as in foundation work, construction of highways (rural), etc.,
make the problem of the prevention of dust more than difficult.
THE ABRASIVE INDUSTRY

In the abrasive industry, which manufactures a number of
products, sand is invariably used. In some instances natural
sand constitutes a large part of the abrasive material.
E. R. Hayhurst and other writers state that " during the last fifteen
years of observations in the State of Ohio, there have appeared fewreports of silicosis and these usually from the abrasive industries "
{Journal of Industrial Hygiene, Sept. 1929, Vol. XI, No. 7).
I saw a worker suffering from moderately advanced silicosis
who described his exposure to silica dust as occurring when he
dumped sand on hot electric elements to be burned with other
substances to produce abrasive material. He stated that great
clouds of dust arose from the hot furnace and remained in the
air for several hours. X-rays of a number of workers in this
industry show that there was definite silicosis present, although
in the early stages. These workers change their occupations
frequently and do not have as many years of exposure as workers
in a more skilled trade.
In a number of abrasive industries a silica hazard exists without,
perhaps, attaining a degree sufficient to produce the great excess
of tuberculosis that is found in other dusty trades.
Grinding is an occupation in the abrasive industry in which
silicosis is known to occur in excess and with such severity that
tuberculosis is a frequent complication. From the following table
it will be seen that the workers in this occupation have an excessive
death rate from tuberculosis.
TABLE III.

MORTALITY FROM TUBERCULOSIS OF THE LUNGS IN A
CONNECTICUT AXE FACTORY, 1 9 0 0 - 1 9 1 9

Death rate
per 100,000
State of Connecticut
State of Connecticut (male population)
Axe factory district (3 towns, entire population)
Employees of axe factory (all)
Employees of axe factory, polishers and grinders
Employees of axe factory, others

150
170
200
650
1,900
160

This table was prepared by Professor C. E. A. Winslow, of Yale University, and Sanitary Engineer Leonard Greenburg, U.S. Public Health Service.

554

PAPERS PRESENTED TO THE

CONFERENCE

COPPER MINING AND SMELTING

The mining and refining of copper in the United States requires
the services of over 60,000 persons. The largest copper mines
are located in Arizona, Utah, Montana, and Michigan, the producing being indicated by the order given. Copper miners are
reputed to have a high incidence of tuberculosis, and it is known
t h a t silicosis is quite prevalent among them. The incidence and
severity of the condition depends on the variety of rock dust
encountered and its concentration. The latter is better controlled
in some localities than in others. Some of the big copper producers
have installed elaborate ventilating systems and have incidentally
been able to salvage enough ore to pay for the cost of operation
of the exhaust system.
The smelting of copper also involves silica hazards; and inasmuch as arsenic is frequently found in connection with copper,
a hazard from arsenic is also frequently encountered.
SAND

The use of sand seems to increase in America with each year.
In 1921 845,008 tons of sand were produced in the United States,
and greater quantities arc used at present. The following
industries use it in their processes of manufacturing:
Glass
Foundries
Paving
Filter
Ballast
Sandblast

Refractories
Abrasives
(1) Grinding
(2) Polishing
(3) Cleaning

Sand varies in its content of free silica, but the amount present
in it is always so great that the variations do not make much
difference. As a causative agent of silicosis, sand rates very high.
The harmful effects of sand are well illustrated in the following
quotation from a personal letter to me from one of the most
eminent X-ray men in the United States:
We have just completed the examination of a few interesting cases.
These men have been engaged as labourers in a plant where sand is
pulverised to be used in the manufacture of sand soaps and other
articles where pulverised sand is the essential part of the goods produced.
It has been noted that a mottling, such as we have designated as the
second stage of silicosis, is present in some of the men as early as

SILICOSIS IN THE UNITED STATES

555

three months after starting the occupations. Massive consolidations
were present within a year, and equal to those seen in hard rock
miners of several years. In other cases, there was the conglomerate
mottling indicative of the third stage, occurring in less than a year.
The men stated that the sand, before pulverisation, was heated to
a high temperature, and when it escaped upon their skins, it would
burn them, and it would take at least two weeks before their skins
became sufficiently tough to handle the sand. We were wondering
whether this hot sand, when in the finely divided state, was at a
sufficiently high temperature to destroy the cilia in the lower air
passages, because of the very quick presence of fibrosis.
We thought this group of individuals might be of interest to you
to present at South Africa.
POTTERY

INDUSTRY

Ohio leads in the United States in the number of pottery workers,
employing almost 14,000 wage earners in this industry. New
Jersey is second, with over 6,000 wage earners, and New York
has about 3,000.
Silicosis has been known to occur among potters for a number
of years, the silica dust being encountered in the glazing of pottery
with silica flour. There are a few other occupations in which
dust is generated, but these are of minor importance.
The silicosis of potters is of such severity that tuberculosis is a
frequent complication; the tuberculosis does not usually occur,
however, until about middle age or later. Newer methods are
being employed in this industry and will no doubt lessen the amount
of dust and consequently the incidence and severity of silicosis and
tuberculosis among potters. One of the leading pottery companies
in the United States has recently completed a very modern plant,
during the planning and construction of which attention was given
to the elimination of dust hazards.
Lead poisoning is also a hazard in this industry.
The print shows early silicosis in a potter (see film 8).
COMPENSATION FOR SILICOSIS IN THE UNITED STATES OF AMERICA

There are two groups of compensation laws in the United States
of America—federal laws and State laws.
The Government of the United States pays compensation for
silicosis under the Act which refers to civil employees of the United
States and to persons whose employment entails movement from
one State to another, as in the case of transport workers. An
instance here is the Longshoremen's Act.
Silicosis is not directly named in a law allowing compensation

556

PAPERS PRESENTED TO THE CONFERENCE

in the United States, but the language of the laws is sufficiently
broad to cover occupational diseases in general, and silicosis is
clearly included.
When a civil employee of the United States develops silicosis, he
must file a claim ; and quite unlike many of the States, the Federal
Government sends a physician to examine the patient, and consider
the case, which is then presented to the Employees' Compensation
Commission where the award is made. Everything is accomplished
without expense to the patient. He need not employ lawyers to
present his case for him.
The case is considered as an injury produced by the inhalation of
harmful dusts. The interpretation of the word " injury " includes
not only accidental injuries, but also " such occupational disease or
infection as arises naturally out of such employment " (section 40,
Longshoremen's and Harbour Worker's Act, 1927). Specific
occupational diseases such as silicosis are not defined, but the
interpretation given above has been used to include silicosis, and
compensation is paid the worker or his relatives.
The following States have legislation, as outlined below, which
permits compensation within the confines of their own boundaries :
California
Connecticut
Maine
Maryland
Minnesota

New Hampshire
New Jersey
Ohio
Rhode Island
Wisconsin

The other States have no definite laws whereby the worker may
obtain compensation. Some manufacturers in these other States
feel morally obligated for silicosis and there have been instances
in which a voluntary compensation has been paid. The amount
paid varies, of course, according to circumstances, such as length
of service, financial condition of the plant, etc. A number of
plants in these States carry insurance on the workers which covers
occupational diseases.
California
Article 20 of the State's Constitution has permitted statutes to
be made covering workmen's compensation and insurance. Under
a certain section the term " injury " is defined as follows: " The
term ' injury ' as used in this Act, shall include any injury or
disease arising out of employment . . . "

SILICOSIS IN THE UNITED STATES

557

Under the Statutes of California an industrial accident commission, which is composed of three members, has been constituted,
and has complete jurisdiction over injuries covered by this Article,
in regard to treatment, compensation, etc.
Connecticut
The physicians in Connecticut are required by law to report
occupational diseases in the same way in which contagious diseases
are reported. Section 2146 of the General Statutes of 1918 reads
as follows:
Every physician having knowledge of any person whom he believes
to be suffering from poisoning of lead, phosphorus, arsenic, brass,
wood-alcohol, mercury or their compounds, or from anthrax, or from
compressed-air sickness, or any other disease, contracted as a result
of the nature of the employment of such persons, shall, within fortyeight hours, mail to the Commissioner of Labour and Factory Inspection a report stating the name, address and business of his employer,
the nature of the disease, and such other information as may reasonably
be required by said Commissioner '.
Section 5388, dealing with compensation of workmen for injuries,
states that the word " injury " shall be construed to include any
disease which is due to causes peculiar to the occupation and
which is not of a contagious, communicable, or mental nature.
It is evident that silicosis is covered. The Act states further:
" If an injury arises out of and in the course of employment, it
shall be no bar to a claim for compensation t h a t it cannot be
traced to a definite occurrence which can be located in point of
time and place. "
Under authority of this Act, five commissioners are appointed
in Connecticut to hear such cases and are given power to make
decisions granting compensation and to do other things necessary
in the administration of the Act.
Maine
In the State of Maine, silicosis is not compensable. The State
requires its physicians to report cases to the State Board of Health.
No doubt the collection of data on occupational diseases will be
very important in obtaining a law for compensation of disabled
workers.
1
Obviously silicosis would be included in reportable occupational diseases
under the heading of " any other disease, contracted as a result of the nature
of employment by such person ".

558

PAPERS PRESENTED TO THE CONFERENCE

Maryland
The same statements apply to Maryland as to Maine.
Minnesota
The physicians of Minnesota are not required to report silicosis.
The workmen's compensation law does not include silicosis in its
schedule, but according to section 67 (10) of the Statutes, claims for
the compensation of silicosis may be made.
Nothing in this Act shall affect the rights of an employee to recover
compensation in respect to a disease to which this section does not
apply, if the disease is an accidental personal injury within the meaning
of other provisions of this Act.
New

Hampshire

The physicians of New Hampshire are required to report certain
occupational diseases which are listed for them, and also " any other
ailment or disease contracted as result of the nature of the patient's
employment ".
New Jersey
Silicosis is not compensable in New Jersey. The Compensation
Act schedules a number of occupational diseases, but leaves out
silicosis and adds : " Compensable occupational diseases shall not
include any others than those scheduled. "
New

York

In the State of New York, again, we find the words " injury "
and " personal injury " coming to the aid of silicotic patients. The
law in this State does not specify that silicosis is a compensable
disease, yet compensation is allowed because of the injury silica
dust has done to the lungs.
Section 2, paragraph 7, of the Statute reads: " ' Injury ' and
' personal injury ' mean only accidental injuries arising out of and
in the course of employment, and such diseases or infection as may
naturally and unavoidably result therefrom ".
While silicosis is not mentioned, it is certain t h a t it comes under
t h e heading of an " injury ", and still more emphatically so when it
is complicated by tuberculosis. The phrase " diseases or infection
as may naturally and unavoidably result therefrom " would make
silicosis compensable. Further, section 48 of the Act makes t h e
matter a bit clearer : " Nothing in this section shall affect the right

SILICOSIS IN THE UNITED STATES

559

of an employee to recover compensation in respect to a disease to
which this section does not apply, if the disease is an accidental
personal injury within the meaning of sub-division 7 of section 2 ".
Five industrial commissioners are appointed by the Governor
and are charged with the administration of the provisions of the
Act and with the care of the State insurance fund, which is a State
fund created for the purpose of insuring its employees against
liability and of assuring the persons entitled to compensation.
The fund consists of premiums, and employers and employments
are prorated in collecting these premiums, in accordance with the
difference in the extent of industrial hazards in their establishments.
The physicians in New York State are required to report
industrial poisonings according to a list; silicosis does not, however,
appear on the list.
Ohio
Ohio, like many other industrial States, requires the reporting
of occupational diseases, but omits silicosis from the list of such
diseases.
The Compensation Act does not specially mention
silicosis, but the term " occupational disease " automatically
includes it in the list of compensable conditions.
Section 35 of the Act reads as follows :
For the purpose of providing compensation to workmen and their
dependants, for death, injuries or occupational disease occasioned in
the course of such workmen's employment, laws may be passed establishing a State fund to be created by compulsory contribution thereto
by employers, and administered by the State, determining the terms
and conditions upon which payment shall be made therefrom. . . .
Such compensation shall be in lieu of all other rights to compensation,
or damages, for such death, injuries, or occupational disease, and any
employer who pays the premium or compensation provided b y law,

passed in accordance herewith, shall not be liable to respond in
damages at Common Law or by statute for such death, injuries, or
occupational disease.
Rhode Island
In Rhode Island the physicians are required by law to report
occupational diseases according to a list which is provided them,
and silicosis is not included. The list carries this phrase, which
obviously includes silicosis : " Any other ailment or disease as a
result of the nature of the patient's employment."
Wisconsin
The physicians of this State are likewise required to report
occupational diseases from a list which omits silicosis.

560

PAPERS PRESENTED TO THE CONFERENCE

The Act (Compensation of Workmen), under section 102, paragraph 34, states that the provisions include in addition to occupational injuries, all other injuries, together with occupational
diseases growing out of and incidental to employment. Thus
silicosis is included as a compensable disease.
An industrial commission, as in many other States, administers
the intentions of this Act. Appeals are also heard by this commission, and if further recourse is necessary, may be taken to the
Supreme Court.
Other States have legislation pending and several have attempted
to pass a Silicosis Act which would specifically make silicosis
compensable.
The great difficulty in obtaining compensation for silicosis is
due to the fact that the disease is so insidious in its development
that the patient may have changed from a dusty occupation
before his illness becomes manifest. In such instances it is not
a simple matter to tie up the disease definitely with the former
occupation. Labour turnover is greatest in dusty occupations
and in other hazardous trades. The great incidence of tuberculosis
as a complication and usually as the immediate cause of disability,
together with the inability of the medical profession, as a rule,
to differentiate between silicosis and tuberculosis or to recognise
their co-existence, makes the workers' chances fewer for obtaining compensation, even when the law allows compensation for
silicosis.
Statistical studies of silicosis in the United States have been
made by Frederick L. Hoffman, L.L.D., of the Prudential Life
Insurance Company, and were published by the Bureau of Labour
Statistics, Department of Labour, Bulletin No. 231, Mortality
from Respiratory Diseases in Dusty Trades (Inorganic Dusts),
and Bulletin No. 293, The Problem of Dust Phthisis in the Granite
Stone Industry.
Among the earlier studies that included the clinical consideration
of silicosis was that made by Dr. A. J. Lanza, then of the United
States Public Health Service, on the occurrence of silicosis among
workers in zinc mines in Missouri. His work was published as
U.S. Public Health Service Bulletin No. 85, and U.S. Bureau of
Mines Bulletin No. 132.
Dr. L. U. Gardner has contributed materially to the knowledge
of the pathology of silicosis by his animal experimentation, using
different kinds of dusts. His studies were published in the
American Review of Tuberculosis.

SILICOSIS IN THE UNITED STATES

561

Other studies of lesser magnitude have been made and have
been published in current journals.
The report here presented is by no means inclusive as regards
the incidence of silicosis in the United States, but rather covers
briefly the industries in which this disease is most common.
Silicosis, being so very insidious in its onset, unless the exposure
is overwhelming, goes unrecognised in many instances for this
reason. Other reasons for the non-recognition of silicosis are the
fact that disability per se comes late in the disease, and the fact
that when tuberculosis complicates it, the superimposed disease
overshadows the silicosis. With the increase of study of industrial
diseases we may hope that silicosis will be more easily recognised
and that more definite data will be available concerning its
occurrence.

OCCUPATIONAL

ENVIRONMENT

Uses of silica

Types of silica used

Abrasive uses:
In scouring and polishing soaps and
powders.
In sandpaper
In sand-blast work
Metal bulling, burnishing and polishing .
For sawing and polishing marble, granite,
etc.
As whetstones, grindstones, buhrstones,
pulpstones, oilstones, etc.
Tube-mill lining
Lithographers' graining sand . . .
Tube-mill grinding pebbles
In tooth powders and pastes
Wood polishing and finishing
Refractory uses: In making silica Are brick
and other refractories.
Metallurgical uses:
In making silicon, ferrosilicon, and silicon
alloys of other metals, such as copper.
As a flux in smelting basic ores . . . .
Foundry-mold wash
Foundry parting sand
Chemical industries:
As a lining for acid towers
As a filtering medium
In the manufacture of sodium silicate . . .
In the manufacture of carborundum
Paint: As an inert extender

. . . .

Mineral fillers: As a wood filler
In fertilisers
In insecticides
As a filler in rubber, hard rubber pressed and
molded goods, phonograph records, etc.
In road asphalt surfacing mixtures . . . .
Ceramic uses: In the pottery industry as an
ingredient of bodies and glazes.
In the manufacture of ordinary glass . . .
In the manufacture of fused-quartz chemical
apparatus, such as tubes, crucibles, and
dishes.
Decorative materials: In the manufacture of
gems, crystal balls, table tops, vases,
statues, etc.
Insulation :
Heat insulation for pipes, boilers, furnaces, kilns, etc
Sound insulation in walls, between floors,
etc.
Structural materials: Sand-line brick . . .
Optical quartz: For the manufacture of lenses
and accessories for optical apparatus.

Quartz, quartzite, flint, chert, sandstone, sand, tripoli,
and diatomaceous earth; all in ilnely ground state.
Quartz, quartzite, flint, sandstone, and sand ; coarsely
ground and closely sized.
Quartz, quartzite, sandstone, and sand, crushed into
sharp angular grains uniform in size.
Ground tripoli and other forms of ground silica.
Sharp, clean sand graded into various sizes.
Massive sandstone from very fine to moderately
coarse grained.
Chert, flint, and quartzite in dense, solid blocks.
Medium to fine sand or rather coarsely ground silica
and tripoli.
Rounded flint pebbles.
Various forms of pure silica finely ground.
All forms of silica ground to medium fineness.
Fairly pure quartzite known as gannister; not less
than 97 per cent. SiOa nor more than 0.40 per cent.
alkalis, tightly interlocking grains desired.
Moderately pure sand, massive crystalline quartz,
sandstone, quartzite, or chert.
Massive quartz and quartzite.
Ground sandstone, quartz, and tripoli.
Fine sand and ground tripoli.
Massive quartz or quartzite.
Massive diatomaceous earth and tripoli, sand, finely
granular quartz or quartzite, finely ground tripoli,
diatomaceous earth, and other forms of silica.
Pure pulverised quartz sand, pure tripoli, and diatomaceous earth.
Pure quartz sand.
Finely ground crystalline quartz, quartzite, and flint;
also finely ground sandstone, sand, and tripoli.
Finely ground crystalline quartz, quartzite, flint,
tripoli, and other types of ground silica.
Finely ground silica of all types.
Flint, tripoli, and chert, and other amorphous silica
preferred ; also all other forms of very pure silica,
all finely ground.
Pure quartz sand.
Very pure massive quartz preferred.
Rock crystal, amethyst, rose quartz, citrine quartz,
smoky quartz, Chrysoprase, agate, chalcedony, opal,
onyx, sardonyx, jasper, etc.
Massive and ground diatomaceous earth.
Do.
Moderately pure, sharp, angular sand, preferably
finer than 20-mesh, together with a small percentage of finely pulverised silica.
Clear, colourless, flawless rock crystal or massivecrystallised quartz.

BIBLIOGRAPHY

SOSMAN, R . B . The Properties of Silica. American Chemical Monograph
Series. 865 p p . 1927.
MineraR O G E R S , A. F . " N a t u r a l History of t h e Silica Minerals." American
logist, Vol. X I I I , 1928, p p . 73-92.
Gesteine.
R O S E N B U S C H . Mikroskopische
Physiographic
der
Mineralien und
B a n d I, zweite Hälfte. B y O. M U G G E , 1925.
LADOO, R. B . Nonmetallic
Minerals;
Occurrence, Preparation,
Utilisation.
McGraw-Hill Book Co., N e w York, 1925. (This w o r k is p a r t i c u l a r l y
valuable on the industrial uses of silica.)

FILM 1.— Anthracite coal miner for thirty-five years.

FILM 2.— Anthracite coal miner for twenty-eight years.
Tuberculosis and anthracosis.
Sputum contained
tubercle baccilli.

FILM 3 . — Coal (bituminous) miner for eighteen years.

FILM 4.—• Motorman (coal train) for seven years. Exposed
to dust from sanding the tracks.

FILM 5. — Silicosis in a granite worker.
An early
tuberculosis is in evidence in the base ot the right lung.

FILM 0. — Silicosis and tuberculosis in a granite worker.
Tuberculosis lesion in base of right lung. Cavitation
present.
Tubercle baccilli were found in sputum.
Basal tuberculosis was common among these workers.

FILM 7. — Sand blaster. Silicosis (tuberculosis two years
later).

FILM 8. — Silicosis in a pottery worker.

563

SILICOSIS IN THE UNITED STATES

APPENDIX

INHALATION OF ASBESTOS DUST: ITS EFFECT UPON
PRIMARY TUBERCULOUS INFECTION
BY LEROY

U. GARDNER AND DONALD E.

CUMMINGS

The following is a summary of a preliminary report on the
experimental investigation of inhaled asbestos dust, dealing with
the reaction in normal and tuberculous animals.
The complete
report will be submitted for publication in the Journal of Industrial
Hygiene.
Guinea-pigs have been exposed for eight hours daily for periods as
long as two and a third years to an atmosphere containing approximately 35 million particles of asbestos dust (Canadian chrysotile)
1.5/1* and less in diameter. Rabbits and albino rats have been likewise
exposed for shorter periods (330 days).
The experiments demonstrate that fibrous structures at least as
long as 200 /* can pass the protective mechanism of the upper respiratory
tract and enter the lung. Anatomic evidence of injury to this mechanism
is wanting.
Inhaled asbestos dust does not penetrate to the terminal alveoli of
the lung as is the case with a particulate substance like quartz. The
major portion is held up in the respiratory bronchioles. There phagocytosis takes place, and there the material remains localised, at least
for a period of two and a third years. Phagocytes containing asbestos
particles migrate into the lateral alveoli given off from the walls of
the bronchioles, and considerable numbers ultimately penetrate into
the adjacent connective tissues. In the guinea-pig, transportation of
dust particles to intrapulmonary arid mediastinal lymphoid tissues is
so slow that changes in these structures play little part in the early
development of asbestosis. In the rabbit, dust cells begin to appear
in the lymphoid tissues of the lung within sixty days after starting
the inhalation; thereafter, they are found in increasing numbers.
In the guinea-pig, fibrosis in the walls of the respiratory bronchioles
and their lateral alveoli is first manifested after 500 days' exposure.
Thereafter this type of reaction progressively increases in intensity
and extent. The resulting atelectasis is responsible for a gland-like
appearance, which is due to the contraction of the included alveoli
and a consequent compression of the epithelial lining cells. In the
rabbit sufficient time has not yet elapsed for fibrosis to be expected.

564

PAPERS PRESENTED TO THE CONFERENCE

In the lungs of guinea-pigs, asbestosis bodies, apparently identical
with those described in the human being, have developed after an
exposure of approximately seventy days. In the rabbit these structures
have not been discovered after exposures as long as 330 days. In the
albino rat they are very rare. Only two small typical forms have been
discovered in one animal exposed for seventy days. The prevalence
of chronic infections of the lung in all members of this series is possibly
responsible.
Asbestosis bodies apparently fail to form in the tracheobronchial
lymph nodes. They may be transported in small numbers to these
tissues and to areas of chronic pleurisy. They have not been discovered
in the peritoneal cavity 100 days after injection of dust. In the subcutaneous tissue of the groin, typical forms were found 102 days after
the injection of 3 milligrams of dust.
Asbestosis bodies are not present in asbestos dust previous to contact
with animal tissues. They are produced by oxidation and hydrolysis
of the chrysotile molecule. The formation of these structures is the
first direct evidence that the body is capable of effecting chemical
changes in inhaled silicate particles. The chemical processes involved
have been discussed in extenso. Attempts at artificial production of
asbestosis bodies in vitro have been partially successful; solutions of
ferric chloride and sodium silicate have been made to combine in the
presence of a fibre to produce more or less typical forms. The asbestosis
body is therefore analogous to the well known " silica garden ".
Attempts to produce asbestosis bodies in vivo by the injection of dusts
containing iron salts and silicates have thus far failed. The failure
to produce them in tissues other than the lung and subcutaneous of
guinea-pigs and man has not been explained.
Comparison between the localisation and the reaction to asbestos
and other types of inhaled dusts has been shown. The points at which
inhaled dust is localised in the lung or lymph nodes vary with the
type. Granite remains within the pulmonary air spaces and produces
no local reaction of fibroblasts for several years. In the tracheo bronchial
lymph nodes characteristic silicotic nodules develop within two years.
Carborundum likewise has failed to affect the stroma of the lung even
in four years, but fibrosis in the lymph nodes has been observed.
Quartz is rapidly concentrated by migrating phagocytes in the pulmonary and mediastinal lymphoid tissues. In these places it provokes
an early and rapid multiplication of fibro-blasts. Asbestos, as it is
inhaled, is concentrated in respiratory bronchioles and their lateral
alveoli. Phagocytes carry it into the walls, where fibroblasts are
stimulated.
Lymph stasis plays little part in early asbestosis; the structure of
this dust tends to localise it within the lung from the start. Lymph
vessels are dilated in the absence of detectable obstruction. The dilatation
may be a direct result of pulmonary irritation.
Primary tuberculous infection is influenced only to a limited degree
by inhaled asbestos. This effect has been tested by inhalation infection
of attenuated tubercle bacilli (strain Rx). One group of guinea-pigs
was infected at the outset of dust inhalation; a second group, two
years after beginning dust exposure. In normal guinea-pigs such
infection produces tubercles in the lung and tracheobronchial lymph
nodes comparable to the primary complex in man. The lesions caseate
and the pulmonary foci heal by resolution. Spread of the infection
with macroscopic disease in other viscera is very rare. In the first
asbestos group infected, 32.2 per cent, of the animals showed some

SILICOSIS IN THE UNITED STATES

565

evidence of spreading tuberculosis. New disease was sharply localised
to areas where dust reaction had occurred. Rarely small cavities
developed in such secondary foci. The tendency to healing by fibrosis
was marked; at autopsy 40 per cent, of the cases showed healed fibrosis
tuberculosis; macroscopic disease in the spleen and sometimes the
liver was common. Dissemination appeared to begin in primary
tubercles contiguous to foci of dust reaction. The contrast with animals
similarly infected but exposed to quartz dust is marked. In them
every exposure longer than five months resulted in generalised chronic
tuberculosis of the lungs and other viscera.
For the second asbestosis group infected, the record is not yet
complete. In them the localisation of the infection was atypical.
Many bacilli were trapped in foci of dust reaction. Some produced
local tubercles; others immediately entered the dilated lymph vessels
and were transported to the tracheobronchial lymph nodes. Tuberculosis in these nodes sometimes occurred without involvement of the
lung. Early diseases in the spleen and hepatic lymph nodes was the
rule. The ultimate outcome of infection in this group has not yet
been observed.
The combined action of asbestos dust and tubercle bacilli in the
lung produced more fibrosis than did either agent acting independently.

THE MEDICAL EXAMINATION OF
NATIVE LABOURERS ON ENGAGEMENT
AT THE GOLD MINES OF THE
WITWATERSRAND
BY

GIRDWOOD,

M.B.,

CH.B.

(EDIN.),

CHIEF

MEDICAL

OFFICER, WITWATERSRAND NATIVE LABOUR ASSOCIATION, LTD.,
JOHANNESBURG

There are approximately 200,000 natives working on the gold
mines of the Witwatersrand. A little more than half this number
is drawn from areas within the Union of South Africa, of which
the largest portion consists of the Xosa, Fingo and Pondo tribes
of the Transkei (Cape Province), and the smallest portion comprises tribes drawn from Zululand and the Northern Transvaal.
Basutos, Bechuanas and Swazis come from the three British
Protectorates, and constitute the second largest portion.
All these natives are known as British South African natives.
The balance of the natives is obtained from Portuguese East
Africa south of Latitude 22° South, and are known as East Coast
natives.
METHODS OF RECRUITMENT AND TERMS OF SERVICE

British South African Natives
Almost one-half of these natives are not " recruited ", but voluntarily
come to the Witwatersrand and seek employment on the mines. The
remaining natives engage through the representatives of the Native
Recruiting Corporation stationed in the native territories, who advance
the natives money to provide for the needs of their families and for the
train fare and food to Johannesburg.
The non-recruited native on his arrival on the Witwatersrand selects
a mine and engages himself for a period of service mutually agreed with
the mine authorities, sometimes on a monthly basis.
The recruited native nominates a mine on attestation, and in the
majority of cases is required to contract for a period of nine months.
In both cases the agreement of service is ratified by the issue to the
native and the employer of a service contract prescribed by the
Government.

' WITWATERSRAND : MEDICAL EXAMINATION OF NATIVES

567

Service beyond the registered period is terminable by the giving of
seven days' notice on either side.
East Coast Natives
All these natives are dealt with by the Witwatersrand Native Labour
Association.
Those seeking mine employment voluntarily make their way to one
of the many camps maintained by the Association in Portuguese East
Africa. From these camps the natives are drafted, either by steamer,
railway or motor transport, to the Association's centralising depot at
Ressano-Garcia, within five miles of the eastern border of the Union.
The natives are forwarded twice weekly by rail from Ressano-Garcia
to the Association's main distributing depot at Johannesburg.
East Coast natives are initially contracted for 313 shifts worked, but,
in terms of the Convention recently concluded between the Portuguese
and Union Governments, may re-engage for a further period or periods
not exceeding 156 shifts worked, upon the completion of which the
native may be called upon by the Portuguese authorities to return
to Portuguese territory.

MEDICAL

EXAMINATION

IN THE

NATIVE

TERRITORIES

The British South African non-recruited native naturally has
no medical examination prior to reaching the Witwatersrand;
but all British South African recruited natives, with the exception
of a few from areas where medical officers are not available, are
examined by the local medical officers—usually Government
district surgeons.
For the guidance of these medical officers a schedule has been
drawn up by the Transvaal Mine Medical Officers' Association,
and in it special attention is directed to diseases of the lungs.
The East Coast native has no searching medical examination
until his arrival at the Association's depot at Ressano-Garcia,
and only natives who are obviously ill or diseased are eliminated
at the various camps.
At Ressano-Garcia, where the Association has a large depot
and hospital, the Association's medical officers (one whole-time
and one part-time) examine and (where necessary) re-vaccinate the
natives, comprising gangs of 300-400 twice weekly, and those
deemed fit for mine work are forwarded to Johannesburg.
At the request of the Tuberculosis Research Committee these
natives have, during the last eighteen months, been given an
intradermal tuberculin injection immediately prior to their departure for Johannesburg, and the reaction is recorded on their

568

PAPERS PRESENTED TO THE CONFERENCE

passports twenty-four to forty-eight hours later, on their arrival
in Johannesburg, and the medical histories followed up during
the period of the natives' stay on the mines.
MEDICAL

EXAMINATION

ON THE

WITWATERSRAND

All natives for employment on gold mines, non-recruited as
well as recruited, and from whatever areas, are given a strict
medical examination at the Witwatersrand Native Labour Association's central depot at Johannesburg, before being registered to
the various mines.
After registration the natives are again subjected to a further
medical examination by the mine medical officer on their arrival at
each mine, and any who are considered to be unfit to commence
work are returned to the W.N.L.A. depot for re-examination
—clinical and radiographic—and possibly for detention in the
depot hospital.
The only difference in the methods followed for the examination
of the non-recruited and the recruited natives is that, in the case
of the former, the mine examination takes place first, upon the
native applying for employment.
DETAILS OF MEDICAL EXAMINATION AT THE CENTRAL DEPOT

There are usually about 170,000-180,000 recruits examined
annually at the W.N.L.A. central depot, and the numbers presented
for examination daily vary from 300 to 1,200.
A staff of six whole-time medical officers perform these
examinations.
On arrival at the depot, every native takes a bath and is given
soft paraffin soap with which to cleanse himself. His clothes are
deverminised in a steam disinfector. These precautions are
necessary owing to the prevalence of typhus fever in the native
territories.
After the clothes have been dealt with the natives are drafted
in batches to the examination rooms, where they are first taught
to breathe properly by trained native orderlies, i.e. in a manner
suitable for auscultation. This may appear unnecessary, but in
practice it is found to be essential and saves a great deal of time,
for some of the natives are very nervous and apprehensive.
The boys are then lined up naked, in rows of about twenty-five,

WITWATERSRAND : MEDICAL EXAMINATION OF NATIVES

569

before each medical officer, who carefully auscultates the chest,
front and back, and a mark is made on the boy's chest on the
detection of any abnormality, however slight. He is thereupon
removed to a special examining room for re-examination by one
of the medical officers, whose whole time is thus occupied. If considered necessary, the native is detained in hospital and X-rayed;
his medical and labour history are enquired into, and a bacteriological examination is made of his sputum.
On the completion of auscultation of each row, an inspection
is made of the limbs, eyes, glands and for the presence of any
venereal disease, and those passed fit are sent to the depot Pass
Office for registration.
A medical officer, when he has become accustomed to doing this
work and has developed the power of concentration, is able to
examine about sixty natives per hour, but requires a break of about
half an hour after two hours' work. To many it may appear impossible to examine such a number with any degree of accuracy, but
it must be realised that all that is demanded of the medical officer
is the detection of an abnormality and not a diagnosis of the
condition. After doing this work for several years the W.N.L.A.
medical officers have naturally become proficient in the use of
the stethoscope.
Occasionally defects are missed at this examination, but this
is more likely to occur at the close of a heavy day.
It is on account of this possibility that a second examination
is carried out by each mine medical officer, where the natives
arrive on the mines in smaller numbers.
Every day, in spite of the schooling, there is always a number
of natives who will not, or cannot, breathe suitably. It has been
found necessary to X-ray the chests of such natives, for experience
has proved a large proportion to have tuberculosis or silicosis.
In many cases the poor breathing is done wilfully, the native
hoping to escape detection by so doing.

DISPOSAL OF UNFIT NATIVES

Natives found unfit at the central depot, including those returned
after the examination by medical officers on the mines, are dealt
with as follows:
1. Natives who are ill are put in hospital and treated, and if the
disease has been of a serious character are repatriated on convalescence.

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2. Natives who are out of condition or merely " train-weary " are
weighed and detained, under medical supervision, in the depot for a
fortnight or longer. During this time the natives are periodically
examined and only passed out when sufficiently improved for underground mine work. Those natives who do not improve to any extent
are usually put on light surface mine work and not allowed to work
underground until passed as fit therefor.
3. Natives with chest abnormalities are detained in hospital for
investigation and treatment. Natives found to be non-tuberculous
are discharged from hospital and afforded mine surface work.
All tuberculous cases, incipient or otherwise, are repatriated
to their homes and warned not to return for mining employment.
Silicotic or tuberculo-silicotic cases are transferred to the miners'
phthisis wards for examination by the Miners' Phthisis Medical
Bureau, a body of medical men appointed by the Government
to examine mine natives with pulmonary tuberculosis or silicosis
with a view to determining the degree for compensation in terms
of the Miners' Phthisis Act. Such natives are repatriated when
fit to travel to their homes.

GENERAL REMARKS

An attempt has been made to give a brief résumé of the medical
examination, as conducted on the Witwatersrand, of natives engaged
for employment on the gold mines.
It is realised that this examination, thorough as the time-limit
permits, is by no means definitely conclusive, but the whole problem
is an extremely important and difficult one. It is felt that, whatever
other method the circumstances may allow, it would still lend itself
to criticism.
From the foregoing it will be realised that one of the chief difficulties
is the large number of natives who have to be dealt with daily, and their
examination completed, as far as possible, on the same day.
A stethoscopic examination alone (which is all that time permits)
has its limitations. Early silicotic and early hilus tuberculous cases are
missed, and obviously it is impossible to subject every native to a
radiographic examination.
A radioscopie examination was undertaken, and over 2,000 natives
were screened, but without the success hoped for. Obvious tuberculous
or tuberculo-silicotic cases were detected, but all early conditions
were not made apparent.
Another great difficulty is that a population which is extremely
susceptible to tuberculosis has to be examined; many have the disease
in a latent, undetectable form which, under their pastoral home conditions, would remain quiescent, but which, after the increased stress
and strain of a few months' mining work, develops into an acute
tuberculosis.

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571

STATISTICAL TABLE

The subjoined table gives the numbers dealt with and the causes
and percentages of rejections at the W.N.L.A. central depot from
January to December 1928:

Class

Causea of rejection

Total
examined

Total
rejected

44,668

Percentage
of rejection

Tuberculosis

Defective
lungs

Other
causes

3,782

272

960

2,550

8.69

14,642

217

112

1.48

50,921

2,429

118

836

1,475

4.66

40,525

1,011

368

609

2.49

14,348
2,946

225
5

14
4

116
1

95
0

1.56

168,050

7,669

481

2,393

4,795

4.56

Per cent.
E a s t Coast recruits
E a s t Coast
re-engagements
British South
African recruits
British South African
non-recruited
British South African
re-engagements
Contractors' n a t i v e s
Total

SANATORIUM TREATMENT OF MINERS'
PHTHISIS PATIENTS
BY

A. D. PRINGLE,

M.B., CH.B., M.D., MEDICAL SUPERINTENDENT,

TRANSVAAL MINERS' PHTHISIS SANATORIUM

PROVISION FOR HOSPITAL CARE AND TREATMENT

The number of cases of miners' phthisis occurring in the early
days of mining on the Rand with a considerable number of deaths
drew the attention of the industry to the necessity of making
some hospital provision for the treatment and care of such persons.
In 1908 negotiations took place with the Government, and in
1910—the Government contributing a site of 20 acres with a small
building thereon—the Chamber of Mines erected and equipped the
Springkell Sanatorium at a cost of some £50,000. To this Sanatorium were admitted all cases, whether of silicosis only or of
silicosis complicated with tuberculosis.
In 1916 it was suggested that the purely silicotic cases should
be housed in an institution quite separate from that in which there
were cases of pulmonary tuberculosis, and with this end in view,
in 1917, the Estate of the Wedge Farm was purchased by the
Chamber of Mines, where a large and commodious country house
was converted and adapted for use as a recuperative hospital much
on the same lines as some of the earlier sanatoria in Scotland.
Of course additions were necessary but in the end suitable provision
was made for fifty beds. The entire cost of building and equipment
in this instance was borne by the industry. Both these sanatoria
are situated within a few miles of Johannesburg and are easy of
access. Considerable provision is made for the free transport of
patients and also for their relations and friends who wish to visit
them.

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573

In so far as Springkell is concerned, the annual cost of upkeep
is in the neighbourhood of £20,000; with the exception of a £5,000
grant from the Government, this is borne by the Chamber of Mines.
Since 1920, a limited number of paying cases have been admitted
from the Military Pensions Department and from the Municipalities.
In respect of Wedge Farm the annual cost of upkeep is in the
neighbourhood of £7,000 per annum—all provided by the industry.
When first opened, Springkell had accommodation for seventytwo patients; this has since been increased to a hundred.
The maximum accommodation at Wedge Farm is for fifty
patients.
Climatically, the situation of both these institutions is ideal from
a sanatorium point of view. Springkell has a northern aspect,
situated in well-wooded country, with a hill on the south side
protecting it from the occasional cold winds of the winter months.
The Wedge Farm Sanatorium is situated on an estate well sheltered
with trees. On the High Veld generally, and particularly within
a few miles of the northern side of Johannesburg, the climate is
ideal; with an altitude of just under 6,000 feet it is never very hot
in summer, and only occasionally is it uncomfortably cold in
winter. The protective quality of the Witwatersrand ridge can
be felt immediately a short journey is made to the south. In
winter it is very much colder in Johannesburg, and the winds are
more persistent and constant. Sunlight we have practically every
day of the year. I do not suppose that we have more than three
days out of the 365 when the sun does not shine for the greater
part of the day. Our rainfall averages about 20 inches per annum
and is precipitated within the limited period of the summer months,
and then almost invariably at night—occasionally in the late
afternoon.
The grounds of both institutions are suitably laid out, and with
the surrounding open country provide plenty of scope for exercise.
There is a remarkable absence of dust.
The administration of both institutions is in the hands of what
is known as the " Miners' Phthisis Sanatorium Board " ; its functions
are purely of a hospital nature. (This Board must not be confused
with the Miners' Phthisis Board, which deals with financial matters,
principally in respect of the compensation of silicotic and tubercular
ex-miners.) The Sanatorium Board consists of representatives
of the gold mining industry and of the Government, one of the
latter's representatives being selected with particular reference to
looking after the interests of the miners.

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The cases admitted to either institution come from the body of
men who have left the mines.
T Y P E OF D I S E A S E

Those conversant with the literature of silicosis are well aware of the
changes that have taken place in the type of the disease, as advance has
been made year after year in controlling the dust underground. Only
the earlier practitioners on the Rand could correctly describe both the
clinical and pathological conditions that obtained in the early days.
The names of Dr. Louis Irvine, the late Dr. Macaulay, Dr. Loeser and
Dr. Andrew Watt are well known in this respect. Dr. Andrew Watt
was in an unusually strong position, in that he made himself an expert
radiographer to assist him in diagnosing the large number of cases that
came to him. All experienced physicians on the Reef agree that the
former cases of massive fibrosis caused by dust are no longer seen—•
nowadays, the silicosis is much more patchy in its distribution and the
tuberculosis element predominates. Among post-mortems that I have
done at Springkell, this change in the type of disease is confirmed,
and among outstanding features one would mention the very patchy
distribution of dust, the tendency for deposit at the posterior margins
of the lungs, and particularly in some cases tough, hard fibrosis round
the roots of the lung. The last mentioned has an important clinical
significance in that where this condition arises early in the mining
career of the individual, incapacitation soon results, an incapacitation
out of all proportion to the amount of dust in the general structure of
the lung. Clinically, these cases early exhibit marked short-windedness,
and an attack of bronchitis in these cases quickly develops further into
emphysema, and, before long, involvement of the heart.
TREATMENT

With the tendency in latter years for the tuberculosis element
to be more pronounced, it cannot be expected t h a t the treatment
of cases of tuberculosis complicated with silicosis is much different
from the main principles of routine treatment adopted in hospitals
and sanatoria for pure pulmonary tuberculosis in other countries.
In so far as cases of pure silicosis are concerned, a great deal
depends on the amount of dust a patient may have in his lungs and
whether he is free or not from secondary infections of the pneumococcal and streptococcal varieties.
We may take it, then, that in so far as the ante-primary or
primary stage silicotic individual is concerned, institutional treatment is required solely as a recuperative measure in general, and in
particular for any accidental affection he may have, such as
bronchitis, asthma, and troubles of this type.
But with respect to the cases of miners suffering from pure
tuberculosis or silicosis complicated with tuberculosis, the routine

WITWATERSRAND : SANATORIUM TREATMENT

575

treatment that is adopted for pulmonary tuberculosis in every
hospital and sanatorium obtains, with the reservation t h a t in
some respects particular attention is given to some outstanding
symptomatic and objective conditions.
Cough
With this symptom the great majority of cases do not differ from the
purely tubercular, but in a few the cough is of a markedly paroxysmal
nature, so severe as to cause vomiting, loss of wind and collapse. The
usual well-known sedative cough mixtures are exhibited, and in a limited
number the simple remedy of black currant infusion; a glass of hot milk
will alleviate a cough that keeps the patient awake.
Dyspnoea
The pure tuberculosis patient has this complaint, but the miner with
a lot of dust has it aggravated. The attacks come with lightning
suddenness and cause the patient great alarm and distress. When it
threatens to be dangerous, and particularly when it is so bad as to render
the patient almost helpless, the quickest and most satisfactory treatment
is a hypodermic injection of ^6 8 r m - °f morphia. Probably, before one
reaches this line of treatment, turpentine stupes, cough mixtures and
stimulants are tried. They help a little, but the good effect does not last.
Apart from the two above-mentioned troublesome conditions,
treatment resolves into general hospital care and discipline, and the
exhibition of such special forms of medication as are advocated from
time to time.
General
All patients sleep on open verandahs, balconies, shelters, or
open-air wards. The principles of constant rest in bed for some
cases and graduated exercise for others are observed. Meals are
taken at regular hours, with rest before and after.
Special
attention is directed to try and meet the vagaries of a patient's
appetite. I mention this, because at Springkell this feature stands
out. It requires at times a lot of personal attention to detail,
and certainly makes ward work heavier.
The preparations of malt and cod liver oil, pure cod liver oil, and.
emulsions cannot be freely given in a locality where the atmospheric
temperature is uniformly mild and warm. As a matter of fact,
my experience among tubercular patients is that where the appetite
is good and the ordinary meals satisfactorily taken, these " extras "
are of little avail. There is a limited number of individuals who do
benefit by these preparations, b u t the general routine use of cod
liver oil is contra-indicated here, as in such a number of cases
patients appear to contract dyspepsia and become " liverish "
(patients' word).

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Of the more direct methods of attack on the disease, we have
tried here during recent years, amongst others, Bruschettini's
Vaccine, Sodium Morrhuate, Dreyer's Diaplyte Vaccine, and
Sanocrysin. These have been extensively tried in Europe, and
there is no need to discuss them fully. Sodium Morrhuate gave
good results in a few cases—we cannot say more; Sanocrysin was
given in a series of thirty-three cases. Of these, sixteen went to
•work or were well enough to work, six improved considerably in
general health, in seven treatment had to be stopped, and four died.
Early and advanced cases were treated, gradual dosage used,
doses varied from 0.15 to 1 grm., and the reactions were of the
same type met with wherever Sanocrysin has been used. The
digestive and gastric upset was, however, predominant, and in one
case a very severe skin reaction (with constitutional symptoms)
occurred even although only a stage of small dosage had been
reached. Early and advanced cases were treated, both among
miners and non-miners.
Collosol Antimony (1 c.c. twice a week) is being tried and appears
to benefit some cases; I have not had long enough experience of it
to speak more definitely.
Solarium Treatment.
This has never been the success in South Africa that it has been in
European countries and the reasons are obvious : in the summer months
direct exposure to the sun, except under most careful conditions, is too
risky—the sun is too hot. This form of treatment is not the success in
pulmonary cases as it is with bone and joint disease. In South Africa
there is only very little trouble of the last-mentioned description among
children. Occasionally one does come across a pulmonary tuberculosis
patient who co-operates heartily and intelligently with the physician
and in some of these cases good results are obtained. Note we are at
26° S. latitude on the Rand—at Cape Town the conditions may be more
favourable for this form of treatment.
Collapse Therapy
Artificial pneumo-thorax is used, but I think the percentage of cases
that are amenable to this particular therapy is of the same small percentage as obtains in other countries. With a tendency now for there
to be more of the tubercular factor in the pulmonary troubles of underground workers, the field for the use of artificial pneumo-thorax will
extend from year to year, and I know of one physician who uses this form
of treatment in cases of pulmonary tuberculosis among ex-miners.
Effect of Locality and Altitude
At the Sanatorium, our altitude is 5,600 feet, latitude 26° South
(Cape Town is at sea level, latitude 34° South).

WITWATERSRAND : SANATORIUM TREATMENT

577

In sanatoria, the time inevitably comes when some patients ask for
a " change ", either to another institution or discharge to go to a different
locality. In the majority of cases with silicosis and pulmonary tuberculosis, the coast towns are not favourable. Cape Town in the winter
months has a cold, wet and rainy season, somewhat resembling parts
of Great Britain—it is in great contrast to the sharp bracing winter of
the Transvaal uplands. Durban, also a coastal town, is very hot and
humid in summer—the stimulating effect on body metabolism of our
perfect Transvaal climate during most of the year must resemble the
same conditions as obtain in the situations of the Swiss Sanatoria.
Apart from climatic change, it is a good thing to give periodical leave of
absence to patients who show a tendency to become " stale ". They
return with improved appetites and settle down more contentedly for
further treatment.
Quack Remedies and Patent Medicines
We have had our full share of these; their names are legion; and the
faith of human patients in the alluring label remains unshaken until
too late. The most recent was a " remedy " widely advertised along
the Reef; and our opposition and condemnation of it threatened a libel
action; but we stood our ground and the case fizzled out. The " remedy"
claimed to cause the lungs to excrete or throw off the particles of silica !
A second patent remedy was an electrical contraption of wires and wood
Jor enveloping the chest. A third consisted of an oil saturated with fine
coal dust ; this was taken " per os ", the coal intended to cause excretion
of silica ; the inventor apparently knew nothing of Haldane's and
Mavrogordato's work. But the promising cures not materialising,
combined with the unpleasant taste of the oil, soon finished off this
remedy.
SYMPTOMS

I will now deal briefly with our local experience with some of the
symptoms commonly met with in cases of pulmonary tuberculosis.
Haemorrhage
It does not appear that among miners with tuberculosis infection
there is any greater percentage of haemoptysis cases than there is
among the non-mining tubercular community, and the characteristic features of haemoptysis are the same. It is confirmed t h a t
only a very small number of cases of pulmonary haemorrhage are
immediately fatal. These are of the sudden overwhelming type
when death occurs within a few seconds. The great majority of
•cases of haemorrhage apart from the above, vary in quantity from
mere " colour " up to a pint or two pints of blood. Most of these
-cases recover from the haemorrhage. To control this haemorrhage,
the injection of morphia hypodermically is the only satisfactory,
.and certainly the quickest method of arrest. Hypodermic injection
37

578

PAPERS PRESENTED TO THE

CONFERENCE

of haemoplastic serum and collosal calcium do help, but they are
not the bedrock of treatment which enables the physician to leave
the patient with an easy mind. In respect of the two latter methods
of treatment mentioned, in my experience it is wrong, and may be
dangerous, to exhibit them too early. The theoretical basis of the
arrest of pulmonary haemorrhage is to cause the quick clotting of
the blood to close up the source of the bleeding. But there are some
cases apparently in which haemoplastic and calcium may induce
such clotting that the patient is embarrassed by the collection of
blood clots in the bronchi, and his suffocation may be caused
by his inability to get rid of such clots quickly. I would cite one
case of a heavily built man who was having a moderately severe
haemorrhage only, but whom I found quite unconscious and
cyanosed. The heroic method I adopted was on these lines.
I argued that if left as he was he must surely die—it was imperative
to get some air into the lungs; and I therefore hoisted up his legs
and stood him on his head. Immediately large clots of blood were
ejected from the bronchi; and within a few minutes the patient
restored to the prone position was resting comfortably in his bed.
Sweating
Night sweats do not appear to be so frequent among miners
affected with tuberculosis as with non-miners. I have not had
any success with pharmacopoeial remedies well known to all. I
believe rather that as good results as any will be obtained by using
the sleeping mat as advocated by Marcus Patterson, and also in
some cases by the use of autogenous vaccines.
Loss of Appetite and Loss of Weight
Among miners, this complaint appears to have the same features
as among non-miners. As a general rule, where the appetite
remains good, not only will the weight take care of itself, but thia
type of patient always stands a better chance of eventual recovery.
Gastritis and Intestinal Upset
These are commonly met with in all cases of pulmonary tuberculosis.
Tubercular Laryngitis
Over a period exceeding twelve years I have not yet found a caseamong miners. It may be mere coincidence: if it is not, it is a.

WITWATERSRAND : SANATORIUM TREATMENT

579

remarkable feature. In the more advanced cases nearing the fatal
termination of their disease, one gets tubercular ulcers in the
pharynx, and I have no doubt that in a percentage of these cases
some infiltration of the larynx would be found at post-mortem
examinations.
Tubercular Testis and Fistula in Ano
Both these combinations appear to occur less among miners than
in non-miners.
Alcoholism
This bugbear of all hospitals and institutions that house patients
over an extended period is also among our administrative problems.
Speaking of alcoholism per se with respect to its relation to prognosis
in cases of pulmonary tuberculosis, I must say that excessive
imbibing of alcohol periodically by a certain type of patient does
not appear to have any devastating effect in respect of accelerating
the progress of the disease. The prognosis is worse only when
alcoholism is associated with unusually bad living conditions with
concomitant bad feeding, poverty, and undue exposure to inclement
weather conditions.
Infectious Element of the Disease
At the Springkell Sanatorium we have an annual admission rate
of more than 100 tuberculosis-infected ex-miners, and this institution
has been open for the admission of patients for some eighteen years.
I do not know of an instance of any member of the family of a
tubercular miner having contracted the disease from living in the
same house with such tubercular individual. It is just possible
that the standard of living among miners in the Transvaal is
higher than it is among the poorer tubercular, badly-housed
families in Europe; this observation applying to food, clothing
and accommodation; the equable climate and strong sunlight-attack
on the bacilli may be the real controlling factors.
INSTITUTIONAL MONOTONY

We do our best to try and relieve this by granting patients
perhaps a little more freedom and leave than has hitherto been
considered necessary. In addition, there is a reading room,
billiard room, a very good library, and the daily newspapers with
the European magazines are easily available. There is a bowling

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green, and a particularly fine " open air " concert pavilion where
entertainments are frequently given. A large wireless installation
has been established which receives from the Johannesburg
Broadcasting Station ; and several patients have their own individual
receivers.
OCCUPATIONS

Whenever and wherever possible, if the patient is fit, he is given
occupation if he wants it; and we have had, and have, patients
doing the following work: Office clerks, telephone operators
(these must be negative tuberculosis sputum cases), motor-drivers,
painters, carpenters, bricklayers, gardeners, and handymen.
.Patients are also employed in poultry keeping, the Sanatorium
providing buildings, runs, and fowls; the patient does the work and
buys the food—we purchase the eggs. We have tried giving
patients outside work to do of the farm-labouring description;
but it has consistently failed.
THE FACTOR OF DISABILITY

Among miners and ex-miners, there is great variation in respect
of disability among individuals classified in the same group, whether
that group be Pure Tuberculosis only, Primary Silicosis, Silicosis
in the Secondary Stage, or Silicosis complicated with Pulmonary
Tuberculosis. With any tubercular factor in lung disease, the
activity or dormant condition of the infection generally determines
the degree of disability. There is marked difference in the disabling
factor of silicosis when this is still in the primary stage. Possibly,
however, the most important consideration must be the presence or
absence of secondary infections—bronchitis the most common.
Lastly, the general health of the individual complicates the situation. " Phthisis " is so much talked about that the individual fails
to realise that the cause of his disability may be disease or disorder
in some organ of the body other than the lungs.
This variation in disability is commented on here owing to its
influence in advising patients with respect to occupations. The
types of patients we admit to this institution will never establish
a colony like that at Papworth—the local conditions are so
entirely different. Those with a knowledge of the efforts made by
the Miners' Phthisis Board to establish ex-miners on land settlements will all agree that these ventures have been disappointing.
I must here take the opportunity of making some observations with

WITWATERSRAND: SANATORIUM TREATMENT

581

respect to the disposal of the ex-miner patient after he leaves the
institution. Finding suitable employment for these patients is
with us just as acute now as was the same problem for the partially
incapacitated ex-soldier immediately after the Great War. Only
the very smallest percentage will ever make even a bare living on
the land, and even these must have very little physical incapacitation and some capital. A few million pounds of good money have
been lost in this country by unfortunates who had dreams of
combining an " open-air " life with occupations such as farming,
poultry-keeping, and vegetable gardening. The average tubercular
patient is entirely unfitted for this kind of work. 1 now advise all
discharged patients to t r y and get back to the job for which they
were trained and to which they are used, and not to be obsessed
unduly with the " open-air " factor. This advice can be taken
by non-miners if they so choose, with reservations for such as school
teachers (sputum positive tuberculosis) who come in contact with
young children. Those who handle foodstuffs (grocers, butchers,
bakers, dairymen, and the like) are definitely debarred from
returning to their previous occupation. But the ex-miner obviously
cannot return to underground work, and only a small number have
been trained in some other occupation before they took up mining.
A few ex-underground workers, such as timbermen, builders, and
mechanics, can get work of this nature on the surface ; but for the
rest the problem is very difficult. Certain it is t h a t they are better
off to continue as employees even at small pay rather than sink
such money as they may have in agricultural and farming adventures.
STAFFING

In respect of the Sanatorium at Springkell, the nursing staff required
does not differ essentially from staffing in similar institutions in other
parts of the world.
At the Wedge Farm, however, where patients of the recuperative
convalescent type are admitted, the staffing is very small, consisting
of a matron and two nurses for an average of roughly forty patients.
It is seldom that nursing is required for very bad bed cases. For the
benefit of those accustomed to the staffing of hospitals in Europe it might
be mentioned that a great deal of the ward work, such as scrubbing
floors and sweeping, is done by native boys. The employment of native
boys for this work at the two sanatoria under consideration is made
easier by the fact that only males are admitted.
TRANSFERS

Wedge Farm Sanatorium is reserved for silicotic cases, and Springkell
for tubercular patients. It is unknown for a silicotic patient to develop
tuberculosis while resident at Wedge; but patients still classified as

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being " without tuberculosis " are sometimes admitted to Wedge and on
examination by the Medical Officer are found to be suffering from active
pulmonary tuberculosis or give a positive tuberculosis sputum; they
are, naturally, immediately sent to the proper institution.
The most common aetiological factor in the superimposition of pulmonary tuberculosis are attacks of " bad cold ", influenza, and pneumonia.
ADMISSIONS,

SPRINGKELL

Since this Sanatorium was opened in 1911, 2,482 miners and nonminers have been admitted. Up to 31 March 1929, roughly one-third
have died, 1,530 have been discharged, and at that date there were still
remaining in the Sanatorium eighty-four patients.
DISCHARGES

These numbered 1,530. The average length of residence of a patient
at Springkell is about four months. Were it not for certain economic
conditions, and the fact that miners reside here as free patients, I have
no doubt that the number of discharges would be higher and the term
of residence of shorter duration.
DEATHS

Deaths at Springkell average roughly one-third of the admissions.
The death rate is an appalling one to quote, but as a criticism of
curative treatment it is useless and misleading.
Springkell having been originally built b y an industrial body,
the factor of being able to select one's cases does not exist. We
admit cases in all stages of the disease; and in the very early years,
owing to certain local conditions, apparently the great majority
of cases admitted were very advanced and in some instances
moribund. Within the last ten years I doubt whether there has
been a genuine case of death ascribable solely to a heavy deposit
of dust in the lungs. In practically all the silicotic cases t h a t
remain free from the tubercular complication and that now have a
fatal termination, the cause of death is something other than lung
trouble. In my experience at the Wedge Farm the great majority
are due to cardiac and renal trouble, and these cardiac and renal
conditions do not appear to differ in any way from those obtaining
among the civilian population who have not worked underground.
A certain number of deaths, in so far as the lungs are concerned,
are precipitated by influenza, acute bronchitis and pneumonia.
Apart from pulmonary tuberculosis (or its complications) as the
cause of death, in a certain percentage of cases the cause of death
is from some malady not connected with silicosis or pulmonary
tuberculosis. On the average at Springkell this figure amounts to

WITWATERSRAND : SANATORIUM TREATMENT

583

1 0 per cent, of the total deaths ; and at the Miners' Phthisis Board
for the years 1922-1927 the number of deaths stated as being " due
to causes other than miners' phthisis " among the beneficiaries
under the Act was as high as 22 per cent. The age at death
remained at an average of forty-five years, but recently is higher.
The amount of dust a patient may have and the degree of tubercular
infection do influence prognosis, it is true; but I hold that the factor
of individual resistance to tubercular disease is very great. Patients
have been admitted with definite pulmonary tuberculosis and have
survived for thirteen years; others admitted with apparently the
same degree of infection do not live thirteen months.
It has previously been mentioned that within the last nine years
we have admitted at Springkell non-miners as well as miners;
and this enables me to say that the non-miner with pulmonary
tuberculosis stands no better chance than the miner with silicosis
complicated with tuberculosis; at any rate, in the average age at
death of the two classes the non-miner dies at an earlier age, but in
some of these cases the illness probably was contracted earlier
in life.
RESISTANCE TO DISEASE

Early practitioners on the Reef will recollect the very great
number of years that some individuals continued their underground
work with apparent immunity from pulmonary tuberculosis, in
spite of the fact that they had in their lungs heavy deposits of dust.
In recent years there is no question of doubt, but that the silicotic
element has been greatly diminished; and yet a large number of
miners become fatally ill with pulmonary tuberculosis. Whether
in the old days the rapid formation of lung fibrosis did in some way
protect the individual from secondary infections it is hard to say;
the fact does remain, however, among cases of pulmonary tuberculosis sent to the Sanatorium, that the presence of some silicosis
in the lung does not make the vast difference in prognosis that one
might expect.
Nationality may be one of the factors. In the very early days
the British miners predominated; latterly the South African born
miners predominate. In particular, the number of Cornish and
North Country miners has diminished to a most remarkable extent.
After some years spent among these pure tuberculosis, and silicosis
plus tuberculosis patients, one gets the impression that there are
certain individuals who follow definite types in the manifestation
of the disease itself. One finds burly heavily built men where the

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tendency is not for pulmonary tuberculosis to dominate the clinical
course, but rather a development of such conditions as bronchitis
and asthma; in these cases there is only negligible loss of flesh, and
in the end trouble is nearly always cardiac. On the other hand
one admits tall, gaunt, lightly built miners where the tubercular
disease follows definitely the destructive course t h a t obtains among
members of the non-mining community.
TABLE I. —

ADMISSIONS AT SPRINGKELL AND WEDGE

FARM

SANATORIA, FROM 1 JANUARY 1 9 1 2 TO 3 1 MARCH 1 9 2 9
Springkell
Year ended
Miners
31 December

1912
1913
1914
1915
1916
31 March
1918
(15 months)
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929

131
157
143
108
108
141
142
99
150
148
145
136
135
108
112
118
124

Non-Miners

—
—
.—
—
—
17
13
17
14
21
25
25
36
30
45

Wedge Farm :
Miners only

—
—
—
—
65
79
93
86
67
84
87
74
100
102
85

(a) During the year 1917, it was decided to have the future financial
and statistical years not as for a calendar year, but for a period of twelve
months beginning on 1 April one year and ending on 31 March
of the year following. Financial and statistical figures had, however,
already been included for the year 1916 as ending on 31 December.
Under the new conditions inaugurated in 1917, the statistical figures
therefore were made up for a period of fifteen months from 1 January
1917 to 31 March 1918. From 1 April 1918, all annual figures are
calculated for the period 1 April to 31 March accordingly.
(¿>) The Wedge Farm Sanatorium was opened only in June 1918.
The number of admissions (65) was therefore for a period of nine months
only—June 1918 to 31 March 1919.
(c) In so far as the admissions to Springkell are concerned, it will be
noted that in the figures as from 1919 onwards there are three columns ;
1 and 2 showing admissions of miners and non-miners to Springkell, and
column 3 showing the number of admissions to Wedge Farm.

WITWATERSRAND: SANATORIUM TREATMENT

585

(d) At the Wedge Farm it is not always sickness that determines
a patient's admission. The economic factor at times bulks very
largely. The ex-miner who has left his work in the ante-primary and
primary stages of silicosis does not receive an annual pension, but is
granted a lump sum. In a great many cases this lump sum soon
disappears either through indiscretion or through unwise adventures
into investments or occupations where the capital has been lost. These
unfortunates often find it difficult to get employment, and just as often
are admitted to Wedge Farm to give them an opportunity to rest up
for a while until they can get a job.

TABLE II.

ANNUAL ADMISSIONS AT SPRÍNGKELL

Miners
Year

Total

1920
1921
1922
1923
1924
1925
1926
1927
1928
1929

116
163
165
159
157
160
133
148
148
169

Non-miners:

Silicosis and
tuberculosis

Pure
tuberculosis

Tuberculosis

84
123
128
127
107
119
97
100
102
112

15
27
20
18
29
16
11
12
16
10

17
13
17
14
21
25
25
36
30
47

The Medical Bureau was established in 1917. It was only a
natural sequence t h a t among a group of specialists who concentrated
on the examination of lungs, clinically and radiographically, as
the years progressed their estimation of the degrees of silicosis
should be modified. Any such modification would naturally mean
t h a t once the new standard was accepted a number of miners would
become classified as having silicosis where previously a negative
result would be given. This may account partly for the variations
in the table above. With respect to miners classified as suffering
from pulmonary tuberculosis only, there is no indication, so far as
the classification is concerned, whether such pulmonary tuberculosis
is purely fibrotic and inactive (old tuberculosis fibrosis) or whether
the disease is in an active condition.
It will be noticed t h a t the percentage of discharges on annual
admissions shows small variation, remaining within recent years
more or less constant between 60 and 70 per cent.—this is, respecting
the miners admitted.

586

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TABLE III.

DISCHARGES
Miners

Springkell
Year ended

31 December 1911
1912
1913
1914
1915
1916
31 March
1918
(15 months)
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929

Non-miners

Wedge

PerPerPercentage Admis- Dis- centage
DisAdmis- Dis- centage
Admisof
of
of
sions charges admis- sions charges admissions cbarges admissions
sions
sions
34
131
157
143
108
108

5
67
103
102
83
58

14.7
51.1
65.6
71.3
76.9
53.7

141
142
99
150
148
145
136
135
108
112
118
122

67
91
65
76
74
90
96
89
74
71
79
79

47.5
64.1
65.6
50.7
50.0
62.1
70.6
65.8
68.5
63.4
67.0
64.7

65
79
93
86
67
84
87
74
100
102
85

45
64
88
77
66
85
90
76
92
95
93

69.2
81.0
94.6
89.5
98.5
101.2
103.4
102.7
92.0
93.1
109.4

17
13
17
14
21
25
25
36
30
47

3
3
10
8
14
14
14
27
36
32

17.7
23.1
58.8
57.1
66.7
56.0
56.0
75.0
120.0
68.0

For the miners admitted at Wedge Farm, the percentage rate
of discharges on admissions is very high, emphasising:
(a) The economical factor already mentioned in the notes on the
Wedge Farm admissions.
(b) The factor of disability. To have such a high percentage rate,
it must follow that the general health of the Wedge Farm admissions
is good.
Non-miners. — Except for the extraordinary figure for 1918, the
discharge percentage rate remains fairly constant from about
60 to 70 pei cent.
In the table given above, there has been a tendency since 1916
for the percentage death rate on admissions to become less each
year at Springkell. Within recent years it has remained fairly
stable at 30 per cent, or a little over. This rate is in sharp contrast
with the very low rate for the purely silicotic cases at Wedge Farm.
Among non-miners there appears to be more variation—the
figures ranging from 14 to 46 per cent.

WITWATERSRAND : SANATORIUM TREATMENT

587

DEATHS

TABLE IV.

Miners
Year ended

31 December 1911
1912
1913
1914
1915
1916
31 March
1918
(15 months)
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929

TABLE V.

Non-miners

Wedge

Springkell

PerPerPercentage Admiscentage
AdmisAdmis- Deaths centage
of
of
of
Deaths
Deaths
sions
admis- sions
admis- sions
admissions
sions
sions

34
131
157
143
108
108

1
46
48
36
41
53

2.9
35.1
30.6
25.2
37.9
49.1

141
142
99
150
148
145
136
135
108
112
118
124

59
50
48
63
52
56
42
50
33
58
36
37

41.9
35.2
48.5
42.0
35.2
38.7
30.9
37.0
30.6
51.8
30.5
29.8

3.1
3.8
2.2
2.3
1.5
2.4
2.3
2.7
1.0
1.9
4.7

65
79
93
86
67
84
87
74
100
102
85

17
13
17
14
21
25
25
36
30
45

5
6
5
2
7
7
11
4
5
7

TOTAL DEATHS AND AVERAGE AGE AT DEATH IN
SPRINGKELL SANATORIUM
Miners and nonminers

Year ended

31 December 1911
1912
1913
1914
1915
1916
31 March
1918
(15 months)
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929

Miners

Non-miners

Total
deaths

Average
age at
death

Total
deaths

Average
age at
death

Total
deaths

1
46
48
36
41
53

41.0
41.3
43.4
42.6
42.4

1
46
48
36
41
53

41.0
41.3
43.4
42.6
42.4

—
—
—
—
—

59
50
53
69
57
58
49
57
44
62
41
44

43.8
45.7
42.90
45.4
44.23
48.46
46.30
47.10
45.34
47.68
51.8
56.2

59
50
48
63
52
56
42
50
33
58
36
37

43.8
45.7
43.4
45.28
44.79
48.79
46.50
47.06
46.24
48.34
52.0
57.7

—
5
6
5
2
7
7
11
4
5
7

Average
age at
death

38.2
43.16
38.4

39.5
42.28
47.42
42.63
35.50
51.8
48.1

588

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In table V, the figures apparently point that among miners
the tendency is for the age at death to advance. Among nonminers, the average age at death is lower for every year since these
two classes of cases have been admitted. The lowest average age at
death is thirty-five for non-miners; and for a period covering the
same number of years, forty-four for miners.

PERSONAL EXPERIENCES
OF MINERS' PHTHISIS ON THE R A N D ,
FROM 1903 TO 1916
BY A . H . W A T T , M.B., CM. (EDIN.), F.R.C.S. (EDIN.), HON. CONSULTING
PHYSICIAN TO THE JOHANNESBURG HOSPITAL

In this paper I shall only attempt to give my personal experiences
of mining conditions and of the incidence and nature of miners'
phthisis between the years 1903 until the formation of the Miners'
Phthisis Medical Bureau in 1916.
If I should appear to use the first personal pronoun too frequently
I hope I shall be pardoned.
At the latter end of 1902 I was appointed Medical Officer to one
of the large mining groups on the Witwatersrand, and 1 had the
advantage of having charge of what, in those days, was a wellequipped small hospital for European employees. In close
proximity, there was a Chemical and Metallurgical Laboratory,
the staff of which was keen and alive to the importance of
the problem of trying to combat the disease by preventive methods
in allaying dust and providing pure air underground. The industry
owes much to the vision and initiative of the Consolidated Gold
Fields of South Africa in providing means to carry out experiments
and investigations into underground conditions affecting the health
of their employees, and in starting reforms, before any legislation
made these compulsory.
After the occupation of Johannesburg, during the Anglo-Boer
War, the mines gradually started work. They had been lying idle
for over two years, and the miners had either been on service or had
been at the Coast or in England.
The mining population in those days was a very different one
from what it became later. The managers and officials were mostly
of American nationality and a very large proportion of the miners

590

PAPERS PRESENTED TO THE

CONFERENCE

were Cornish or North Countrymen. They practically had all come
from overseas and there were very few South African born miners or
officials. The miners were skilled men and had spent their lives
from boyhood in the practice of their trade. They had lived under
conditions where they had been exposed to the infection of tuberculosis from infancy, and were born of parents who had likewise been
exposed. Consequently, they had an immunity to tuberculous
infection, and the type of miners' phthisis they developed was
more of what we classified as pure silicosis, or tubérculo-silicosis,
in contrast to the commoner type which developed later—silicotuberculosis. After the Anglo-Boer War the Deep Level Mines
began to be developed. In some, at this time, the shafts had
struck the Reef at great depth, and some had not got down to it.
Ventilation was bad; the formation of dust was practically
unhindered. The practice of blasting the " cut " and the " round "
in the same shift was universal. Work was paid for by results, and
the earnings of men were large. The attitude was " Let us eat,
drink and be merry, for to-morrow we die ".
Very soon the price had to be paid. Many men died or became
unable to carry on any work on account of increasing dyspnoea.
Cough was not a predominant symptom except in the early morning,
on rising. These patients coughed until vomiting was induced
without bringing up much expectoration. Ultimately, in very
many cases, cardiac failure either sudden and acute, or chronic,
supervened, and death resulted without obvious signs of tuberculous
infection. Pneumonia, in those days, was a very fatal disease.
Sanitation above and below ground was primitive, and there was no
water-borne system of sewerage in existence. The water supply
was bad, and careful people boiled all the water and milk they
consumed. Enteric fever was prevalent.
A Commission was appointed by Lord Milner, in 1903, to enquire
into the prevalence of silicosis, and although the medical examinations were not conducted by specialists and X-ray examination
was not then employed, about 20 per cent of the miners examined
showed signs and symptoms of pulmonary disease.
The late Dr. Donald Macaulay and Dr. L. G. Irvine, the present
Chairman of the Miners' Phthisis Medical Bureau, were working
at the silicosis problem, and read papers on the subject to the
Chemical and Metallurgical Society.
In 1911 another Commission was appointed to report upon the
incidence of Miners' Phthisis. This Commission reported, as the
result of the examination of 3,136 miners at work, that 32 per cent.

MINERS' PHTHISIS ON THE RAND, 1903-1916

591

were classed as having miners' phthisis in one or other of its stages.
The means of arriving at an accurate diagnosis were not so refined
as they are now, and the men were only examined once.
Owing to the generosity of the Board of the Simmer and Jack
Hospital, I had been permitted to purchase three X-ray machines,
discarding the first ones purchased as improved machines were
produced. A standard of X-ray diagnosis had thus been arrived
at, but it was not possible to get good plates with the short exposures
t h a t obtained then. Films with double screening had not been
introduced, and gas tubes were in use.
An attempt was made to correlate the X-ray appearances of
films, taken during life and after death, with the signs, symptoms
and post-mortem appearances—macroscopic and microscopic.
Chemical estimations were also made by the late Dr. Jas. Moir as
to the character and amount of inorganic material in the lungs.
The men were examined by a number of different medical men, and
their standard of normality naturally varied. The majority of the
members of the Commission were engaged in practice, and the work
had to be carried out in time taken from their practices.
The Commission classified cases of miners' phthisis into four
stages :
Class I.
Class II.
Class III.
Class IV.

Borderland cases, 5.5 per cent.
Early cases, 21 per cent.
Intermediate or advanced fibrosis 1 , r
Advanced cases incapable of work / " "

These figures do not include any miners living on the Rand who
had already relinquished work.
The opinion was formed t h a t a miner might develop miners'
phthisis after two years' work underground, but not sooner.
In 1912, Dr. L. G. Irvine and the author read a paper before the
Transvaal Medical Society on miners' phthisis, the causation, signs.
and symptoms, stages, pathology, diagnosis and treatment of the
disease; in which X-ray prints of silicosis were shown.
As a result of the report of the Commission, the first Miners'
Phthisis Act was passed and came into operation on 1 August 1912.
Under the Act, miners' phthisis was defined as silicosis of the lungs
and silicosis had to be found to be present by definite physical signs
before any case could be described as miners' phthisis.
Pure tuberculosis was not miners' phthisis and was n o t
compensatable.
In a later Act pure tuberculosis was made a
compensatable condition when it occurred in miners. Any.under-

592

PAPERS PRESENTED TO THE CONFERENCE

ground worker found to be suffering from open tuberculosis was
removed by law from underground work, as he was considered a
source of infection to his fellow-workers.
An advisory Medical Committee was appointed to examine
applicants for benefits under the Act. This Board consisted of
three practitioners, each, for the East and. West Rand and six
practitioners for the Central Area. X-ray examination was
recognised as an aid to diagnosis, but was not universally employed.
The examiners were not whole-time men. Each applicant had to be
examined independently by two members, and on their report his
case was dealt with by the Miners' Phthisis Board and compensation
paid or not.
I think all will agree that the work of this first Advisory Committee was not entirely satisfactory. The members were engaged
in general practice and their standards were unequal.
Previous to starting work underground every miner had to be
medically examined. This examination was carried out by the
mine doctor. Here again, the personal element entered and
standards varied. For example, a man might be rejected by one
doctor and go to another on a different mine and be passed, and,
once being in possession of a certificate of fitness, would be permitted
to work on any mine on the Reef.
The Commission had scheduled the Mines of the Transvaal as
either phthisis-producing or non-phthisis mines. All the gold
mines of the Witwatersrand were in the former category.
Another result of the Commission's Report was the formation
of the Miners' Phthisis Prevention Committee. This Committee
(consisting of Government officials, mining officials and workmen,
chemists, consulting engineers and medical men) co-ordinated all
the work which had been and was being done for the prevention
of the disease, and they issued a report in 1916, as the result of
which the present Miners' Phthisis Medical Bureau came into being.
The work and functions of the Medical Bureau is dealt with by the
Chairman of the Bureau.
Such is a short sketch of the history of miners' phthisis before
the formation of the Bureau. My personal experience and that of
my colleagues are contained in the paper " Silicosis on the Witwatersrand ", published as an appendix to the report of the Miners'
Phthisis Prevention Committee in 1916.
But much work and research had been done in the meantime.
I can only speak of work done in the Deep Level Mines of the
Consolidated Gold Fields Group.

MINERS' PHTHISIS ON THE RAND,

1903-1916

593

It was recognised from post-mortem examinations that the dust
factor was the first problem to be tackled. I well remember going
underground in 1903 to watch the effect of dust-laying appliances
in drilling with machine drills. When the drill was working, it was
impossible to see the face a few feet away, and we all came to the
surface covered with white dust. This was the usual experience,
not only with machine drillers, but the " hammer boys ", especially
those drilling upper holes, came to the surface with their faces and
upper parts of the body white with dust.
Mr. McArthur Johnston, soon after, started sampling the air by
•the sugar tube method. This was a fairly accurate method of
estimating the quantity of dust but not the size of the particles.
It was, however, an index of the efficiency of the dust-allaying
methods with which we were experimenting.
It was recognised from the investigation of the various Commissions that the rock drill miner, especially the machine developer,
acquired the disease sooner than the miner who did not work with
machines. This was probably due to the inhalation of fine dust
produced in drilling. But there were other factors. The blasting
of " cut and round " in the same shift, for example. The miner first
blasted the cut and then returned to the face, as soon as possible,
to charge and blast the round. In doing so, he not only inhaled
dust produced by blasting but also the fumes of the explosives used.
In the early days, cases of gassing were frequent, but the miner
appeared to acquire a degree of immunity to the effects of " gas "
provided that the detonation of the explosive was complete;
.unfortunately, this was not always the case.
Blasting accidents where the miner and his " boys " sustained
terrible injuries, often entailing the loss of sight, were common.
Methods used to prevent the formation of dust were experimented
upon and developed, and they all entailed the use of water. Whether
this is the ideal method of dealing with the problem is now in doubt.
The manager of the Simmer Deep Mine had had much experience
in coal mining in Scotland, where much attention had to be paid
to ventilation. The Simmer Deep about 1911-1912 was the
deepest mine on the Rand. The temperatures were high (average
wet bulb, 80° E.).
In July a ventilation exhaust fan had been installed at the Rudd
Shaft of the Simmer Deep. The adjacent shafts on either side were
thus downcast shafts. The Rudd Shaft was used entirely for
ventilation. Before the installation of the fan the amount of air
-coming out of the,shaft was 105,703 cubic feet per minute. Shortly
38

594

PAPERS PRESENTED TO THE

CONFERENCE

after, 200,000 cubic feet were passed. The purity of the air was.
tested by its C0 2 content. There was a great improvement as the
result of more efficient ventilation.
In 1907, in sampling one of the main air ways of the Jupiter, the
adjoining mine to the Simmer Deep, and connected with it, 0.57 per
cent. C0 2 was contained in the air, whereas in sampling a " dead
end " in the Simmer Deep in 1912, 0.15 per cent, was found and in
the upcast air in the shaft it was 0.17 per cent.
In every operation of mining, dust was raised, so that the disease
was not confined to the driller, but the lasher and trammer and
every man working underground, including shift bosses, samplers
and mine captains, were liable to contract miners' phthisis.
Attempts were made to reduce the dust by wetting the downcast
shafts, by making the air from the workings pass through screens
of vapour formed by ordinary gas burners through which clean
water was forced by gravitation, by watering the rock which was
being shovelled or moved, by watering down the working places
after blasting, and by using jets of water into the holes when
drilling and by use of the water blast after blasting. Rock drills
with hollow drills to convey water during drilling were introduced
later.
What perhaps did more good than any of these was the introduction of blasting in one shift, only, in the twenty-four hours and the
prohibition of blasting " cut and round " in the same shift.
Single shift blasting was first introduced on the Simmer and
Jack Mine, and considerably later became universal.
About this time, as the result of examinations by the medical
examiners, the opinion was formed that a miner could possibly
develop silicosis two years after he started underground work in
these mines.
In 1907 a strike occurred, and, as a result, many overseas-born
miners left the country for good. This was due partly to economic
conditions and partly to the high morbidity amongst underground
men.
Home-born miners, now, do not come in large numbers to the
Witwatersrand, on account of the strictness of the initial examination by the Miners' Phthisis Medical Bureau. A very high standard
of general health is required, and if there is any evidence of pulmonary abnormality they are rejected and stranded in this country.
A new type of miner was introduced from the South African veld
and farms. He came of a race quite well developed and set up
physically but with little acquired immunity to tuberculosis, and

MINERS' PHTHISIS ON THE RAND,

1903-1916

595*

the type of the disease, miners' phthisis, began to change and
become more of an infective type.
Accurate figures are not available, as the present Miners' Phthisis
Medical Bureau had not been started.
On the Simmer and Jack an investigation was made as to t h e
amount of infection which existed underground and on the surface.
Visible samples of sputum in the ladderways and workings were
collected and examined. Samples were also taken on the surface
and from the compound rooms. More samples were found to be
tuberculous underground than on the surface, but this might be due
to the effect of dryness and sunlight on the surface. The results
only proved that there was a good deal of open tuberculosis on the
mines.
At the end of 1913 a number of white rats were placed underground at the top of a stope where air containing fumes and dust
after blasting passed. These rats were killed after varying times
spent underground, and excellent specimens of silicotic lungs were
obtained.
These specimens formed the basis of a report by
Dr. Pratt-Johnson, which is contained in the paper presented to the
Miners' Phthisis Prevention Committee in 1916 by the writer and
colleagues.
It had been asserted that animals did not develop silicosis underground, but wild rats had only been examined—and they probably
had not lived long underground—and some ponies on the Crown
Mines.
Perhaps a similar experiment, under working conditions, would
help to test Dr. Haldane's thesis that dusting with coal dust would
be as efficient as water in preventing silicosis.
The Witwatersrand Mines still produce silicosis, but it takes very
much longer to develop.
The type of the disease has changed,and tuberculosis predominates—pure tuberculosis is now compensatable.
Miners' phthisis is a compensatable disease, and finality has not
apparently been reached as to how much compensation a sufferer
is to receive.
The payment of compensation is a very great burden on
the industry and may make the difference as to whether a low-grade
mine may run at a profit or not. Therefore, apart from the
humanitarian aspect, the prevention of miners' phthisis is a
problem of great economic importance.
The man starting underground work to-day is in the A l Class
owing to selection at the initial examination of the Miners' Phthisis

596

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Medical Bureau, and it should be our endeavour to keep him so by
improving underground conditions, by providing healthy living
conditions on the surface, and by obtaining his co-operation in
preventing the disease.
The amount of dust in the underground workings has been very
much reduced, but in the deep level mines this reduction has been
obtained by saturating the mine air with moisture. Cases of heat
stroke are becoming not uncommon, especially amongst natives
who have not become accustomed to working in places with a high
wet bulb temperature, although attempts to get them " into
training " before putting them to work in hot places are invariably
made.
I have not discussed the question of miners' phthisis in natives,
as it is many years since I have had practical experience in dealing
with this part of the problem. The native is more prone to pure
tuberculosis and acute diseases of the lung than the European,
but does not develop silicosis so rapidly, probably because he has
frequent long spells when he goes back to his kraal to live the life
of a gentleman attended by as many wives as he can afford, and,
lastly, by the anatomical arrangements of his air passages. The
South African native is not a mouth-breather.
I have not attempted to give any statistics or figures. These
will be available in other papers. The Witwatersrand has led the
way in the study of this very ancient disease, because, unfortunately
the disease has been more prevalent here than in any part of the
world, and the opportunity for research and study has been made
possible by the generosity and business acumen of the leaders of
the industry.

THE F U N C T I O N S
OF THE MINERS' PHTHISIS MEDICAL B U R E A U
AND THE GENERAL SYSTEM OF MEDICAL
EXAMINATIONS CONDUCTED UNDER T H E
MINERS' PHTHISIS ACT
BY L. G. I R V I N E , M.A., M.D., CM., B.SC. (PUB.H.) (ED™.),
CHAIRMAN, MINERS' PHTHISIS MEDICAL BUREAU

The Miners' Phthisis Medical Bureau was instituted under
the Miners' Phthisis Act of 1916, and commenced its work on
1 August of that year. It is a body of whole-time Government
medical officials and has been since the above date responsible
for conducting or directing all medical examinations under the
Miners' Phthisis Acts.
Its first Chairman was Dr. W. Watkins-Pitchford, who already
held and continued to hold the post of Director of the South
African Institute for Medical Research. Partly owing to this
conjunction of offices on the part of the first Chairman, the Bureau
has, since its inception, occupied premises in the Institute block
of buildings. The arrangement has proved useful in many ways,
especially owing to the proximity which it affords the Bureau to
well-equipped laboratories.
Administratively, however, the
Bureau is a totally distinct organisation. It is strictly and solely
a Government institution in the Department of Mines. All appointments to it are made by the Minister of Mines and Industries.
On Dr. Watkins-Pitchford fell the heavy task of organising the
new institution, and he continued to direct its activities for a
period of ten years. In September 1926, he was succeeded as
Chairman by the present writer, when the personal connection
with the Institute terminated.
The examining medical officers composing the Bureau at
first numbered six; later, as the amount of work increased, the
number rose to ten, and for the past few years it has been eight.
The senior examiner, Dr. C. C. Murray, is also Vice-Chairman.

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PAPERS PRESENTED TO THE

CONFERENCE

Dr. W. Steuart has since the inception of the Bureau occupied the
part-time post of radiologist. The official pathologist (Dr. A. Sutherland Strachan) is Lecturer on Pathology at the University of the
Witwatersrand and a member of the pathological staff of the
South Africa Institute for Medical Research. The Bureau has
thus the advantage of obtaining an independent pathological
opinion in arriving at decisions in cases which involve pathological
investigation. A secretary and a technical and clerical staff of
nineteen complete the establishment.
In respect of all miners of European extraction, termed officially
" European miners ", the chief duties of the Bureau are as follows :
1. To conduct an " initial examination " of all persons who desire
to enter for the first time upon work underground in any of the gold mines
of the Witwatersrand area—called " the scheduled mines ".
2. To conduct a " periodical examination " of all working miners,
with the object of detecting cases of silicosis, tuberculosis with silicosis,
or simple tuberculosis which may arise amongst them.
3. To conduct a " benefits examination " of all claimants for awards
under the Act as possible subjects of one or other of these diseases.
4. To investigate and decide all claims preferred by the dependants
of deceased miners, on the ground that such miners had been the subjects
of silicosis or tuberculosis.
The precise scope of these examinations will be explained
more fully later on.
The similar examinations of Eurafrican and Asiatic miners,
termed " Non-European miners ", are also carried out directly
by the Bureau.
In respect of the very large number of " native labourers "
employed in the industry, the official initial examination is carried
out at the central depot of the Witwatersrand Native Labour
Association by the medical staff of that organisation. The periodical
examinations are conducted on the mines by the mine medical
officers. All of these officials act as medical examiners under the
Miners' Phthisis Act. The Bureau exercises a general supervision
over all of these examinations by means of periodical visits of
inspection to the mines. All native labourers suspected by the mine
medical officers of being the subjects of tuberculosis or silicosis
are, however, sent forward to the Bureau for final examination
and disposal by it. This is the general system.
The Bureau is also charged with the compilation of a statistical
account of the incidence of silicosis and tuberculosis as shown by
the results of the examinations made during each year. This

WITWATERSRAND : MINERS' PHTHISIS MEDICAL BUREAU

599

statement is published in the annual Report of the Chairman
of the Bureau.
A general idea of the amount of work performed by the Bureau
in each year may be gained from the following table.
TABLE I. — SUMMARY OF THE WORK OF THE BUREAU FOR THE YEAR
ENDING 3 1 JULY 1 9 2 8

Nature of examination or Investigation

Examinations for " initial " certificate
(Europeans)
Examinations for " periodical " certificate
(Europeans)
Examinations for " special " certificate
(Europeans)
" Benefits examinations " (Europeans)
Claims in respect of deceased European miners
Claims for allowances to children of beneficiaries
Examinations of non-European miners during
life
Examinations in respect of deceased
non-European miners
Examinations of native labourers during life
Examinations in respect of deceased native
labourers
Total routine examinations

Supplementary

Number of
examinations

Number of
individuals
dealt with

9,251

8,122

26,394

14,726

2,507
3,900
449
87

1,523
3,463
428
85

108

104

9
1,795

429

45,077

30,684

Investigations

Post-mortem examinations:
Europeans
Others
Admissions to Bureau Ward for special
observation
Special visits to sick miners at their homes
Visits of inspection to scheduled mines
Total
Daily average

227
438
558
39
149

—

46,488
153

—

The Bureau possessed on 31 July 1928 medical and radiographic
records of 71,288 European miners, and 21,736 non-European
miners and native labourers. During the year a total of 42,524 portrait negatives of European miners were made, for purposes of
identification. Natives are identified by fingerprints. The number
of radiographs produced during the year was 36,660.

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CONFERENCE

All pathological investigations made on behalf of the Bureau
are carried out at the South African Institute for Medical Research.
The amount of this work, as shown by the number of specimens
examined and reported upon during the year was as follows:
lungs (pairs), 665; specimens of urine, 657; specimens of sputum,
23,426; specimens of blood, 962 (Wassermann test, 733;,
General, 229); specimens of faeces, 87; miscellaneous, 3.
The wealth of pathological material made available through
the work of the Bureau is thus apparent. This circumstance has
enabled the Bureau to carefully correlate the results of pathological, radiological and clinical examination in a large series
of cases, and it is upon the results of such a correlation that its
standards of diagnosis are based.
The routine of examination to which each person is subjected
at each examination in any of the jour classes mentioned is as follows:
(1) his photograph is taken for purposes of identification, and his
signature is also photographed on the same negative; (2) a radiograph of his chest is taken; (3) his weight and height are measured,
in trousers and socks, without boots; (4) he is subjected to a
clinical examination by a member or members of the Bureau. All
persons who are considered by the examining medical officer
to be probable or are actual subjects of silicosis or tuberculosis are
examined by at least two members of the Bureau.
The examinations are completed each day before 2.30 p.m.,
when the Bureau meets as a whole to decide upon all cases examined
during the day. The examiner or examiners in each case report to
the Bureau the result of their examination, the radiograph of the
examinee is inspected, and if the case is in any way doubtful it is
then discussed by the Bureau. The final decision is in all cases taken
by the Bureau as a whole. Any possible personal idiosyncrasy on the
part of individual examiners is thus eliminated and a uniformity of
standards as far as possible secured. But the Bureau maintains a
continuous investigation of its material and methods, in order, if
possible, to improve the latter and to secure the greatest efficiency
possible.
In addition to this routine procedure, free use is made by the
Bureau of the Observation Ward in the building occupied by it.
Any man in respect of whom special observation is required is
admitted to the Observation Ward for a period of three days. His
temperature is recorded, the sputa of three consecutive days and
the urine examined, a Wassermann test is made, and any other
laboratory investigations which may be required are carried out.

WITWATERSRAND : MINERS' PHTHISIS MEDICAL BUREAU

601

During the year, 543 European miners were in this way admitted
to the Observation Ward or, in a few cases, to the General Hospital,
Johannesburg, for special observation.
Miners of whom examination for the purposes of the Act is
required, and who are too ill to be brought to the Bureau, are
examined at their homes by a member of that body ; thirty-nine such
visits were paid during the year.
Further, a " review " examination is readily granted by the
Bureau in the interval between the statutory examinations, in
the case of miners in respect of whom the Bureau is informed that
the health of the individual has deteriorated since the last examination, or in the case of applicants for the initial certificate whose
health appears to have improved; 923 such examinations were
made during the year.
The system of examinations would thus appear to be as thorough
and elastic as is possible in the circumstances which necessitate
dealing with over 30,000 individuals annually.
Some comments on each class of examination may perhaps
be of interest, and it may be well to deal first with the examination
of European miners and later with that of non-European miners
and native labourers.
EXAMINATIONS OF EUROPEAN MINERS

Examination for the Initial Certificate
The " initial certificate " is a certificate of fitness for underground
work granted by the Bureau after examination, and the Act
requires that any person who desires to enter for the first time
upon employment as a " full-time " miner in a scheduled mine
must possess such a certificate. The initial certificate certifies that
the holder "is free from any disease of the lungs and respiratory
organs, and is in other respects physically fit for underground work".
All certificates issued by the Bureau are in card form, bearing on
the back a photograph of the holder and of his signature, and
specifying the date on which the certificate ceases to be valid. The
initial certificate is valid for six months. At the end of that period
the holder, provided that he has in the interval been employed
as a " full-time " miner, becomes entitled to appear at a " periodical
examination " as a " working miner ".
The object of the initial examination is to debar all persons
who have or appear to have more than an average liability to
contract silicosis or tuberculosis from entering upon underground

602

PAPERS PRESENTED TO THE CONFERENCE

work in scheduled mines. The standard of selection adopted must
accordingly be a reasonably strict one. The following were the
general results during the year 1927-1928:
TABLE

II.

•—

RESULTS

INITIAL

EXAMINATIONS

(EUROPEANS), 1927-1928
Total

Born
in South
Africa

Born
overseas

Number of candidates examined

8,122

6,696

1,426

Percentage rejected:
Temporarily
Permanently

43.34
18.62

—

Number of examinees passed

3,090

2,435

655

Percentage of examinees passed in
each class

38.04

36.37

45.93

The high preponderance of South African born candidates is
a prominent feature. It will be noted that only 18.6 of the total
examinees were permanently rejected, while the " temporary "
rejections amounted to over 43 per cent. The latter class comprises
those in whom the Bureau finds defects in health or physique which
may be remediable. These persons are eligible for re-examination
after the lapse of such a period as may, in the opinion of the
Bureau, suffice for the removal of these defects, and experience
has led that body to give a rather wide latitude in this direction,
especially to young and immature would-be recruits. A considerable
proportion of such candidates eventually succeed in obtaining an
initial certificate.
One very important result of the initial examination has
been to introduce into the general body of working miners a
gradually increasing number of men of specially selected physique.
Those of this selected class who had not worked underground on
the Rand prior to 1 August 1916, and who have not had previous
service in other mines elsewhere, are termed the " new Rand
miners ". These men now number over 8,300 and constitute
over 54 per cent, of the total body of working miners. The fact that
these men have up to the present shown surprisingly low attackrates for silicosis appears to indicate that the system of selection
provided by the inital examination of the Bureau has filled an
important preventive function.

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The Periodical Examination
By the " periodical examination " is meant the statutory
examination of all " working miners " with the object of detecting
the presence or absence of compensatable disease amongst them.
The term " working miner " includes, along with all " full-time "
miners working beneath the surface, all persons working on or
about crusher-stations, or in a sample crushing room or assay
office, or in a change-house or on any tailings dump. All of these
classes of employee are included under the Act as " working miners "
and are subjected to the " periodical examination ". The
" full-time " miners working underground form the vast majority.
The four other classes are included — change-house attendants
in order to exclude tuberculous subjects from that employment,
the others because their occupation is considered to expose them to
some risk of contracting silicosis.
" Working miners " who are in employment must present
themselves for examination at intervals of not more than
six months. Those who are not employed remain eligible for the
periodical examination for an indefinite period, prodded that they
present themselves for examination at intervals of not more than
two years from the date of expiry of the last periodical certificate
issued to them. If they fail to do so, they are subjected again to an
" initial " examination. As a result of this provision the number
of working miners examined in each year by the Bureau usually
exceeds the average number of miners in actual employment
underground by about 40 per cent. The provision permits the
miner to leave the mines for considerable periods without forfeiting
his eligibility to return to underground employment later on.
The " periodical certificate ", which is issued by the Bureau after
examination to the " working miners ", certifies simply that the
holder " is not suffering from tuberculosis ", and entitles him to
continue in or offer himself for employment in any of the occupations specified above. Once it has been granted, the certificate
is periodically renewed in the case of all miners who remain eligible
and submit themselves for examination, unless the holder is
found upon examination to be suffering from tuberculosis or
tuberculosis with silicosis. In the latter event the miner i& debarred
from all further underground work in the scheduled mines. Any
miner who has accepted an award as the subject of silicosis is
likewise debarred from further underground work in these mines
and ceases therefore to be eligible for a periodical certificate.

604

PAPERS PRESENTED TO THE

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The purpose of the periodical examination is, as has been stated,
the detection and notification of all cases of the three " compensatable
diseases " — " simple silicosis ", " tuberculosis with silicosis "
and "simple tuberculosis"—which exist amongst the "working
miners ".
By " simple silicosis " is meant silicosis without a definitely
recognisable or " o v e r t " tuberculosis; by "tuberculosis with
silicosis " is meant silicosis with overt tuberculosis; and by " simple
tuberculosis " is meant tuberculosis of the respiratory organs,
without detectable silicosis.
Any " working miner " who is found to be suffering from one
or other of these conditions is notified to that effect. If his condition
is one of tuberculosis with silicosis or simple tuberculosis, he is
obliged to relinquish underground work immediately. If he is
found to have simple silicosis, it is optional for him to apply to the
Board for an award of compensation and to leave underground
work, or to remain at work and postpone taking an award. Should
the miner, however, remain at work for a period of longer than
three months after receipt of a notification that he has silicosis, he
forfeits during his lifetime all right to an award, other than that
to which he would have been entitled at the date of his first
notification. Few miners, however, continue to work underground
after they have been notified as being silicotic. In 1927-1928
there were at work only 144 unretired silicotic miners, a very
considerable majority of whom were mine officials.
The subjoined table illustrates the scope and general results
of the periodical examinations conducted during the past
three years:
TABLE

III.

RESULTS OF PERIODICAL

EXAMINATIONS

THREE YEARS 1926-1927 TO 1928-1929

Number of examinations made
Number of individual miners
examined
Cases detected:
Unretired " old " cases of silicosis
" New " Cases:
Simple Silicosis
Tuberculosis with Silicosis
Simple Tuberculosis

FOR

THE

(EUROPEANS)

1926-1927

1927-1928

1928-1929

24,815

26,542

27,073

13,654

14,726

15,492

127

144

154

364
21
42

283
0
32

270
5 »
44

i These cases occurred in unretired silicotic miners.

WITWATERSRAND : MINERS' PHTHISIS MEDICAL BUREAU

605

It may be added that, during 1927-1928, no fewer than 318 additional examinations were made for special reasons in the interval
between the statutory examinations, and that, of the " working
miners " examined, 203 were admitted to the Observation Ward
for more detailed examination.
Examinations for the "Special" Certificate
The " special " certificate is granted by the Bureau, after
examination, to a number of persons whose work takes them
underground from time to time, but who are not " full-time "
miners. Surface artisans going underground now and then for repair
work or for similar occasional duties, mine inspectors, some mine
managers and others who do not spend their full time underground
fall into this class. These persons also are examined by the Bureau
once in six months, particularly since most of them have been at
one time full-time miners and had then been exposed to the ordinary
risk of contracting silicosis. Such special examinations number
about 2,500 per year in respect of some 1,500 persons so employed.
A very few cases of silicosis or tuberculosis are detected from time
to time amongst these men, and those who are so detected are
compensatale under the provisions of the Act.
" Benefits Examinations "
" Benefits examinations " are carried out in claims for awards
made by or in respect of living miners. It is to be noted that,
in the case of claims for awards made by miners who have been
found to have silicosis or tuberculosis or both conditions at a
periodical examination, no further examination is required precedent to the first grant of benefits. When, however, such miners make
application for further awards, they become subject to the " benefits
examination " of the Bureau. A small number of retired miners,
who have not previously been found at a periodical examination
to have silicosis or tuberculosis, and who apply for awards, are
also included in the " benefits " return.
The main object of the " benefits examination " is thus the
re-examination of existing beneficiaries, in order to ascertain
whether they have progressed to a further stage of the disease
and have therefore become entitled to further awards.
The number of benefits examinations conducted in 1927-1928
was 3,900 in respect of 3,463 persons. The extent to which

606

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re-classification takes place is indicated by the fact that, in this
one year, out of 2,709 silicotic beneficiaries examined, 502 were
certified to have become entitled to further awards, and 291
of these to have become entitled to receive life-pensions.
Claims made in respect of Deceased Miners
During the year the number of claims made by dependants
of deceased miners numbered 428. A large number of these claims
were made in respect of miners who had died overseas regarding
whom the Bureau had had no previous information or opportunity
of securing that an adequate examination was made during life,
and in such cases particularly a large amount of enquiry and
expenditure of time was frequently necessary to enable the Bureau
to obtain sufficiently reliable information to enable it to come to a
just decision on the presumptive evidence available. The great
importance in the interests of the dependants of such a simple procedure as a sputum examination in cases of suspected tuberculosis
is very frequently entirely overlooked by the medical men who
attend such cases during life, and the extremely valuable evidence
afforded by a radiograph in cases where the presence of silicosis
has not previously been demonstrated, but is merely presumed,
is very far from being adequately realised, even in centres where
a radiographic examination is readily procurable. The Bureau deals
with such cases on their merits, but is sometimes placed in much
difficulty owing to the paucity of reliable evidence of the actual
condition present at death.
Appeal Examinations
The Miners' Phthisis Act of 1925 established a Medical Board
of Appeal with power to revise decisions of the Bureau in respect
of examinations involving a possible grant of an award. Two of
its three members had previously acted for many years as members
of the Bureau. In 1927-1928 the Board of Appeal, according to
the returns notified by it to the Bureau, considered 722 cases referred
to it, and the Bureau's decision was altered in respect of 44 of these.
EXAMINATIONS OF NON-EUROPEAN MINERS

The number of non-European miners employed underground
amounted in 1927-1928 to 426 persons; 104 claims were made by

WITWATERSRAND:

M I N E R S ' PHTHISIS MEDICAL BUREAU

607

non-European miners or ex-miners, 42 of whom were found to have
silicosis, 8 to have tuberculosis with silicosis, and 8 to have simple
tuberculosis. By the courtesy of the Witwatersrand Native Labour
Association, these examinations and the initial and periodical
examinations of non-Europeans are carried out by members of the
Bureau at the central depot of the Association.
EXAMINATIONS OF NATIVE MINE LABOURERS

The native labourers undergo, as in the case of European miners,
an " initial " and "periodical" examination, and also an additional
examination, termed a " final " examination, on the termination
of their underground employment. The magnitude of this task
becomes apparent from the fact that some 194,000 natives were
employed upon the mines during 1927-1928, and that the total
complement is replaced to the extent of approximately 90 per cent.
during each year. These examinations are not carried out directly
by the Bureau, but by the mine medical officers acting as examiners
under the Act. The Bureau, however, exercises a general supervision
and control over this work, mainly by means of periodical visits
of inspection by delegated members of that body to the different
mines. Drs. C. C. Murray and G. H. Knapp have carried out this
important function for many years. Each mine is visited several
times in each year.
The Act prescribes that all medical officers in medical charge of
natives on the mines should hold whole-time appointments, except
in the case of a few small mines, to which the Minister is empowered
to grant exemption from this provision. The mine medical service
on 31 July 1928 comprised thirty-six whole-time and four part-time
appointments, including in these the medical staff of the Witwatersrand Native Labour Association Central Depot, at which
the " initial " examination of all native recruits is conducted.
The general system of procedure in regard to native labourers
may be briefly summarised:
1. The initial examination is in practice a threefold process. There
is a preliminary medical examination in the recruiting areas, a principal
and official medical examination at the Native Labour Association'^
Depot, and a supplementary examination by the mine medical officer.
2. The periodical examination under the Regulations of the Act
of 1925 consists of two parts:
(i) Each native employee, whether working on surface or underground,
is weighed, obligatorily every three, months, actually according to the general
practice once in six weeks. Any native who has lost 5 lbs. in weight

608

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between two successive examinations, or 6 lbs. between three successive
examinations, is set apart for stethoscopic examination by the mine
medical officer. It has been found that approximately 66 per cent, of
bacteriologically verified cases of simple tuberculosis amongst mine
natives have previously shown a loss of weight of this amount at their
periodical examinations. This appears to be the limit of the efficiency
of this method of mass examination, which has been adopted in view
of the large number of natives concerned and the necessity of not interfering unduly with their daily routine of work and meals.
(ii) An additional separate stethoscopic examination is made of all
natives who hace worked upon any one mine for a period of five years or
more. The object of this examination is particularly the detection of
possible cases of silicosis or tuberculosis with silicosis in those natives
who have worked underground for long periods.
3. The final examination. Every native employed underground
undergoes, on leaving underground employment, a " final " stethoscopic
examination, and can only be discharged if he is found by the medical
officer to be free from silicosis and tuberculosis.
These are the examinations prescribed under the Act.
In
addition, the mine medical officers, on their own initiative, have
adopted the system of making a stethoscopic examination of
all natives who are admitted to the mine hospital for any cause.
Finally, during the past three years the Chamber of Mines
has instituted an annual radiographic examination of all natives
who have worked on any one mine for five years or more, the
results of which have had the great practical value of demonstrating that no large number of undetected cases of silicosis
had existed on the mines.
The system as a whole draws round the mine native labourers
a serviceably close net of opportunities for the detection of silicosis
and tuberculosis.
The Act prescribes t h a t all native labourers in whom a medical
" examiner " finds signs of tuberculosis or silicosis should be sent
forward for examination and final disposal by the Bureau. In
practice all such cases are transferred to the Central Hospital
of the Witwatersrand Native Labour Association. Here a radiograph
is taken of their chests, their sputum and urine are examined, and
the weight and temperature recorded. They are then clinically
examined by a member of the Bureau and the final decision is taken
by that body on the evidence.
The following are the results of the examination of such
cases by the Bureau during 1927-1928.
Average number of natives employed
Average number employed underground
Suspected cases sent forward for examination by the
Bureau

193,076
147,375
1,795

WITWATERSRAND:

M I N E R S ' PHTHISIS MEDICAL HUREAU

Number of cases of compensatable disease detected amongst
these
viz. simple silicosis
tuberculosis with silicosis
simple tuberculosis

609

1,352
209
409
746

The total number of cases of active tuberculosis detected was
1,155, or 5.89 per 1,000 of the total complement.
The periodical examination of the mine natives thus serves an
important preventive function by eliminating from the underground
complement cases, which, if they remained, would be potential
sources of dissemination of tuberculous infection.

THE FUNCTIONS AND EXPERIENCE OF THE
MEDICAL BOARD OF APPEAL APPOINTED
UNDER THE MINERS' PHTHISIS ACT
BY MEMBERS OF THE APPEAL BOARD

The Medical 'Board of Appeal was established under the Miners*
Phthisis Consolidating Act of 1925. The Board consists of three
members and a Secretary appointed by the Minister of Mines and
Industries. The functions of the Medical Board of Appeal are:
(1) The examination of any " miner " who is dissatisfied, on medical
grounds, with the certificate of the Medical Bureau on any periodical
examination, or on any examination for benefits, provided that he has
not accepted any benefits under such an award made as a result of such
certificate and provided further that he gives notice of appeal within
three months after the receipt by him of the Medical Bureau's certificate
of such examination. (The periodical examination is a compulsory
six-monthly examination by the Medical Bureau of all working miners;
if silicosis or tuberculosis is detected, a certificate by the Bureau must
be issued accordingly.)
(2) The reviewing of the case of any deceased " miner " whose
dependant is dissatisfied with the Medical Bureau's decision as to the
cause of such miner's death.
The word " miner " is defined in the Act as *' any person (other
than a native labourer) who is or has been employed underground
at a scheduled mine in any of the occupations specified in the Act ".
It is obvious from the above that the native underground worker
has no right of appeal.
Every appellant is X-rayed and independently examined,
clinically, by all three members of the Medical Board of Appeal.
In the case of post-mortem claims all the pertinent records are
considered, and, when available, the lungs are inspected. The
lungs of deceased miners, on whom autopsies are performed, are
preserved for six months.

WITWATERSRAND : MEDICAL HOARD OF APPEAL

611

A provision of the Act requires the Medical Bureau and the
Miners' Phthisis Board to produce, if requested, to the Medical
Board of Appeal all records in their possession in respect of any
appellant.
The Medical Board of Appeal was established as a result of an
insistent demand by miners and beneficiaries who, rightly or
wrongly, felt that they were not getting what they considered a
" square deal " from the Medical Bureau.
Before the establishment of the Medical Bureau in August 1916,
large numbers of miners were compensated in either the primary
or secondary stage of silicosis on certificates issued by two or three
doctors from a panel appointed by the Government; when these
cases came to be reviewed by the Medical Bureau it was found
that a large percentage of them were not the subject of silicosis
at all and were certified by the Bureau accordingly. This was
undoubtedly one of the main factors that led to distrust of and
dissatisfaction with the Medical Bureau. Another important
factor in this respect is the irresponsible manner in which some
medical practitioners will certify, without a thorough scientific
investigation, that a particular miner is suffering from silicosis or
tuberculosis or both when, in fact, he is free from disease of the
lungs and may be suffering from a totally different complaint; a
climax is reached when an inexperienced doctor, after post-mortem
examination, certifies the presence of silicosis in lungs which show
at most a slight excess of pigment. It is to be regretted that, in
these cases of difference of opinion between private medical
practitioners and the Medical Bureau, the latter should be suspected
of incompetence or wilful injustice to the miner.
The constitution of the Medical Board of Appeal was a matter
of some difficulty for the Minister of Mines, who had to make the
appointments. The Act requires that the Appeal Board shall
consist of three medical practitioners with special knowledge of
diseases of the lungs and respiratory organs. The Minister realised
that the appointment to the Medical Board of Appeal of medical
men who were not at least as experienced as members of the Medical
Bureau, would be ridiculous and might easily wreck the working
of the Act ; he therefore decided to divorce two of the senior members
from the Bureau for appointment to the Board of Appeal.
This step has caused considerable dissatisfaction among miners,
the contention being that these two members would be loth to
upset the decisions of a body (the Medical Bureau) to which they
formerly belonged. Why this suspicion should arise in the case of

612

PAPERS PRESENTED TO THE

CONFERENCE

medical men promoted to a higher body, and not in the case of the
legal profession, is quite incomprehensible.
When it is considered that the Medical Board of Appeal has to
review the decisions of an expert and highly organised and
competent body such as the Medical Bureau, it is not to be expected
that a large percentage of the decisions by that body will be altered
on appeal. The members of the Medical Bureau work at high
pressure, year in and year out, handling on an average nearly
150 cases per day; it is therefore impossible for them to devote
to each individual case the time which the Medical Board of Appeal
are able to do; as a direct result of this the Medical Board of
Appeal is able, occasionally, to detect signs of very early silicosis
or of tuberculosis which may have escaped notice previously; but
these cases are really extraordinarily few in number.
It must be remembered that the law allows a period of three
months from the date of the Bureau's last certificate within which
a miner may give notice of appeal; it therefore often happens that
the appellant does not appear before the Medical Board of Appeal
until three or four months after his examination by the Bureau;
during this time it is quite possible that silicosis or tuberculosis,
undetected or perhaps only slightly suspected at the previous
examination, may become manifest ; this does, in fact, happen in a
not inconsiderable number of cases.
In some cases the certificate of the Medical Bureau is altered by
the Appeal Board, not because any new facts have been elicited,
but because, in considering all the evidence which was previously
available to the Bureau, the Medical Board of Appeal comes to a
different conclusion. Since, according to the Act, the decision
of the Medical Board of Appeal is final, it behoves this body, as it
always earnestly endeavours, to neglect no line of investigation that
may elucidate doubtful points in any particular case; in cases of
genuine doubt, the benefit thereof is given to the appellant,
especially in post-mortem claims.
Copies of the certificate of the Medical Board of Appeal are issued
to the Miners' Phthisis Board and the Medical Bureau in every
case; where the certificate of the Medical Bureau is altered, the
reasons for such alteration are notified to that body.
The appellants who appear before the Appeal Board may be
divided into two classes:
(1) Miners who are certified by the Bureau to be free from silicosis
and tuberculosis.

WITWATERSRAND : MEDICAL BOARD OF APPEAL

613

(2) Miners who have been certified by the Bureau to be in the anteprimary or primary stage of silicosis and those who have been certified
to have tuberculosis without silicosis.
Class 1 consists mainly of working miners, but there are included
in this class also miners who have ceased work on scheduled mines
anything up to twenty or more years ago, and beneficiaries who
were compensated by the old administration before August 1916,
when the Medical Bureau was established, and who were
subsequently certified by the Bureau to be not suffering from
silicosis or tuberculosis. In this class, then, the Medical Board
of Appeal must decide whether the appellant has silicosis or
tuberculosis or both, or whether he is free from these diseases.
It may be necessary, here, to draw attention to the fact that the
term " miners' phthisis " does not appear in any of the provisions
of the Miners' Phthisis Act; silicosis and pulmonary tuberculosis
are the only two terms employed to denote disease which is
compensatable under the Act.
The question now arises: What is silicosis ? The Act does not
define the term " silicosis ", but it is now generally accepted in
South Africa that silicosis is a generalised nodular fibrosis of the
lungs caused by the inhalation, over a long period, of minute
particles of siliceous dust. We have no intention of entering upon
a description of the several stages of silicosis either from the pathological or clinical point of view; nor shall we refer to the changes
resultant upon infection by the tubercle bacillus. The remarks
which follow apply to " simple silicosis ", i.e. silicosis without any
clinically obvious tuberculous infection. Before dealing with the
clinical diagnosis of a slight degree of simple silicosis, it is necessary
to refer very briefly to the naked-eye appearances of a silicotic lung.
For the purpose of administering the Act it is the considered
opinion of the Medical Board of Appeal and of the Medical Bureau
that it is not practicable to recognise any but macroscopic signs in
the post-mortem diagnosis of silicosis. The earliest silicotic changes
detectable by the naked eye are :
1. Enlarged, pigmented and fibrosed root-glands.
2. Sub-pleural plaque formation.
3. The presence, throughout the lung tissue, of more or less evenly
distributed, discrete, small-sized, pigmented fibrotic nodules which
project from the cut surface and are palpable.
These changes occur in the order given above ; the root glands may
be affected, as described, without any involvement of the lung

614

PAPERS PRESENTED TO THE CONFERENCE

substance. A few scattered sub-pleural plaques may be palpable
without any nodules being present in the lung, but we have never
seen silicosis of the lung without palpable sub-pleural plaques.
It may be asserted, therefore, that, if the pleura presents a normal
appearance, section of the lung will not reveal any silicosis.
These small fibrotic nodules are represented in the X-ray picture
by small round shadows which are more or less well defined and
give the skiagram a typical " mottled " appearance.
According to the Act a person shall be deemed to have silicosis in
the ante-primary (first) stage when it is found that the earliest
detectable specific physical signs of silicosis are present. It is
possible, in the majority of cases, for the expert ear to diagnose
stethoscopically the presence of ante-primary stage silicosis; this
diagnosis is based on a peculiar harshening and thinning of the
brêath-sounds with a slightly reduced air entry ; this change in the
character of the breath-sounds is, however, so subtle in early silicosis
and is so often produced by other conditions that it cannot be said
to be specific of silicosis.
In the ante-primary stage of silicosis there is no appreciable
diminution of the range of chest expansion and there are no
constitutional disturbances. It may be stated dogmatically,
therefore, that the earliest detectable physical sign which can be
said to be definitely specific of silicosis is the fine uniform mottling
of the radiograph produced by the resistance of silicotic nodules
to the passage of the Rontgen rays ; in our experience there is no
other condition that can produce this X-ray picture in an
apparently healthy subject.
A mere increase or accentuation of linear or branching shadows
in the radiograph caused by peribronchial and perivascular fibrosis
due to other conditions, e.g. chronic bronchitis, tuberculosis,
chronic cardiac disease, etc., must not be confused with the typical
radiographic appearances due to silicosis. It is hardly necessary
to mention that, for the purpose of the radiographic diagnosis of
early silicosis, the X-ray film must be technically perfect.
As regards the inspection of X-ray films, we know of no artificial
illumination which can compare with sunlight reflected from a
white surface.
With reference to pulmonary tuberculosis, a provision of the
Miners' Phthisis Act reads as follows:
A person shall for the purposes of this Act be deemed to be suffering
from tuberculosis whenever it is found either:
(a) that such person is expectorating the tubercle bacillus, or

WITWATERSRAND : MEDICAL BOARD OF APPEAL

615

(¿>) that such person has closed tuberculosis to such a degree as
seriously to impair his working capacity, and render prohibition
of his working underground advisable in the interests of bis
health.
We do not intend discussing the diagnosis of early pulmonary
tuberculosis ; the extreme difficulty of arriving at a definite diagnosis
in early sputum free cases is known well enough to all experienced
workers in this sphere.
In order to make a diagnosis of closed tuberculosis in any
particular case, we consider it essential that there should be present
a combination of signs from the following three groups:
1. Constitutional signs and symptoms, e.g. anorexia, loss of weight,
fever, lassitude, languid and hollow- or deep-eyed appearance, night
sweats, etc.
2. Physical signs in chest, e.g. localised flattening of chest wall,
restricted movement, impaired note on percussion, signs of consolidation,
crepitations, etc.
3. Radiographic evidence, i.e. the presence of abnormal shadows
of varying degree in the lung field.
In Group 1 nearly all the signs are the result of toxaemia which
may be caused by conditions other than tuberculosis.
In Group 2 the signs may be produced by many conditions, e.g.
catarrhal infections, unresolved pneumonias, bronchiectasis, pleural
effusions, empyema, new-growth, gumma, etc.
In Group 3 shadows may be caused by thickened pleura, unresolved pneumonia, empyema, pleural effusion, new-growth,
gumma, etc.
It is obvious, therefore, that a diagnosis of closed tuberculosis
ought to be made only after a very careful and painstaking consideration of the whole symptom-complex, and after exclusion, by
appropriate investigation, of the many conditions which so
frequently produce signs and symptoms simulating those of
pulmonary tuberculosis. Haemoptysis, for example, is sometimes a
very early and important sign of pulmonary tubercle, but no
clinician of experience would dream of making a diagnosis of
pulmonary tuberculosis on this sign alone.
It is true that with long experience one is able, or one thinks one
is able, to differentiate between the X-ray appearances caused by
various lung conditions, but it is also true that with longer experience
one becomes convinced, especially if one is also a clinician, that it is
foolish to make a diagnosis of a lung condition from radiographic
signs only.

616

PAPERS PRESENTED TO THE CONFERENCE

We have seen radiographic shadows similar to those produced by
tuberculous consolidation disappear like magic after anti-syphilitic
treatment in Wassermann + + cases, and after no treatment at
all in cases of unresolved and clinically unsuspected localised
pneumonias; we have seen a bilateral primary alveolar carcinoma
with abcess formation give X-ray appearances identical with
those of silicosis with tuberculous consolidation; a myxosarcoma
simulating hydatid cyst and cases of generalised nodular tuberculosis with radiographic features almost indistinguishable from
those of silicosis. Whereas in the diagnosis of early silicosis the
radiographic is the most, if not the only, reliable sign, in the
diagnosis of early pulmonary tuberculosis it must in the majority
of cases take the place of corroborative evidence only; in fact,
in quite a number of positive sputum cases there are no radiographic
abnormalities at all.
A certificate by the Medical Board of Appeal to the effect that a
miner is suffering from pulmonary tuberculosis becomes a legal
document; on the one hand it means the disbursement of a large
sum of money; on the other, if the person so certified is a working
miner, he is legally debarred from work in a scheduled mine and will
have great difficulty in obtaining employment elsewhere.
The matter is therefore a serious one, and a diagnosis of pulmonary
tuberculosis should be made only when definite evidence of the
disease is present; a diagnosis of so serious a disease ought never to
be made in a haphazard manner, as is unfortunately only too often
done, and the diagnosis should never be based on suspicion only.
There is a vast difference between suspecting the presence of the
disease and making a definite diagnosis; it is this difference which
accounts for the large number of miners who are certified by
irresponsible medical practitioners to have pulmonary tuberculosis
and who are found by the Medical Board of Appeal or the Medical
Bureau not to have the disease.
In the second class of appellants it is a question for the Appeal
Board to decide whether the stage in which the appellant has been
classified by the Medical Bureau is the correct one or not.
In a few cases the Bureau's certificate of ante-primary stage may
be altered to primary stage, but the majority of alterations in
this class are due to the decision of the Medical Board of Appeal
that the silicosis in either the ante-primary or the primary stage
already certified by the Bureau is complicated by the presence of
pulmonary tuberculosis either open or closed.
For the purposes of the Act a person is deemed to have silicosis

WITWATERSRAND:

M E D I C A L BOARD

OF APPEAL

617

in the secondary (pensionable) stage when it is found that he has
definite and specific physical signs of silicosis, and that capacity
for work is thereby seriously and permanently impaired, or when it
is found that he has tuberculosis with silicosis; in the latter case
the degree of silicosis is not qualified.
It is a peculiar, yet well-known, fact that if a miner on the Rand
suffers from any chronic disease causing loss of weight, lassitude,
cough, shortness of breath, etc., he becomes obsessed with the idea
that " miners' phthisis " is at the bottom of his trouble. It is
quite impossible to convince a miner suffering from serious cardiac
disease that his cough and dyspnoea are due to his heart condition,
or, in other cases, that his symptoms of ill-health are due to chronic
bronchitis, chronic malaria, pyorrhoea, or anaemia, etc. Similarly,
it is difficult for dependants of deceased miners who may have had
a slight silicosis to realise that there are many causes of death to
which silicosis does not predispose or contribute.

STATISTICAL ACCOUNT
OF T H E INCIDENCE AND P R O G R E S S I O N
O F S I L I C O S I S A M O N G S T T H E GOLD M I N E R S
OF THE WITWATERSRAND
BY

D. SPENGE FRASER, F.F.A., A.I.A.,

AND L. G. I R V I N E , M.A., M.D., CM., B.SC. (PUB. H.) ( E D I N . )

Definitions
In this discussion we shall employ the term " simple silicosis " to
connote a condition of silicosis without obvious or overt tuberculosis,
the term " tuberculosis with silicosis " to connote a condition of silicosis
accompanied by obvious or overt tuberculosis, and the term " simple
tuberculosis " to designate a condition of tuberculosis unaccompanied
by detectable silicosis.
By the " prevalence " of any one of these conditions for any year is
meant the total number of cases of that condition detected in that year
amongst the " working miners " examined, and by the " prevalence
rate " the ratio per cent, of the number of such cases to the total number
of working miners. " Prevalence " thus includes the " new " cases which
arise in the year specified plus the " old " cases of miners who have
contracted the disease in previous years, but who have not retired from
work underground.
By the " production " of any one of these conditions one means the
number of " new " cases of that condition which are detected in any
one year amongst miners who have been previously examined and
found to be free from that condition. By the " production rate " is
meant the ratio per cent, of the number of new cases of tbe particular
condition specified to the number of such working miners examined.
The terms " ante-primary ", " primary ", and " secondary " stages
of silicosis have the meanings set out in the Act of 1925.
The term " working miner " designates any European eligible for
the " periodical " examination of the Bureau and includes, in addition
to miners working below ground, a comparatively small additional
number of persons working in assay offices, on or about crusher stations,
in change houses and on tailings dumps.
The term " scheduled mines " designates the mines of the Witwatersrand area which are scheduled as " phthisis-producing " under the
Miners' Phthisis Act.
The first and major portion of this paper deals with the statistics
of silicosis amongst European miners, but reference is made in the
concluding section to the incidence of silicosis and tuberculosis amongst
native mine labourers employed on the scheduled mines.

WITWATERSRAND: SILICOSIS STATISTICS

619

I. — Evidence regarding the Prevalence of Silicosis
during the Period prior to 1 August 1917
Accurate data regarding the production of silicosis were not
available prior to the year 1917-1918, i.e. the year following the
institution of the Medical Bureau. In 1916-1917 the Bureau carried
out a complete examination of all working miners, but the cases
detected during t h a t year represent " prevalence ", not " production ". Unfortunately, therefore, no accurate information exists
regarding the production of the disease at the time when conditions
were at their worst.
There exist, however, certain data regarding the earlier periods
from which some idea of the prevalence of silicosis during these
years may be gained.
The two important landmarks in our local knowledge of the
disease, during t h a t time, are the Report of the first " Miners'
Phthisis Commission " issued in 1903 and the Report of the
" Miners' Phthisis (Medical) Commission " issued in 1912. Some
additional but less comprehensive information is also obtainable
from the Report of the " Mining Regulations Commission " issued
in 1910.
These items of evidence have already been referred to in the
" Review of the History of Silicosis on the Witwatersrand ",
which forms one of this series of contributions, and it is
unnecessary therefore to discuss them in detail. For the sake
of completeness, however, a brief reference to this evidence may
be made here.
(1) The first official mention of " miners' phthisis " occurs in the
Report of the Government Mining Engineer (Transvaal) for the Six Months
ending 31 December 1901, in which it is stated that of 1,377 rockdrill
miners, known to have been employed on the Rand prior to the outbreak
of the South African War, 225 had died during the war period or up to
the beginning of 1902. This represents an average annual mortality of
some 73 per 1,000, but it must be recollected that it refers to a single
occupational group and not to the whole body of working miners.
(2) The Report of the Miners' Phthisis Commission of 1902-1903
contains more extensive, but (for reasons for which the Commissioners
were not responsible) far from complete information regarding the
position at that time. Out of 4,403 miners officially stated to have been
working underground in the gold mines of the Witwatersrand 1,210 were
examined on behalf of the Commission: it is definitely stated that even
on the mines on which this examination was carried out there were a good
many abstentions. Of those examined 187, or 15.4 per cent., were
certified to be affected by " miners' phthisis " and 88, or a further
7.3 per cent., were suspected cases. The prevalence rate was thus found

620

PAPERS PRESENTED TO THE CONFERENCE

to be about 23 per cent., but this figure for the reasons given is probably
an understatement. Over 90 per cent, of this first generation of Rand
miners were of overseas origin, coming mostly from England, and over
80 per cent, had had previous mining experience elsewhere. The average
duration of service amongst the small number of purely Transvaal
miners affected was seven years, and in those of this group who had
worked only on machine drills it was 5.75 years.
(3) The " Mining Regulations Commission " which reported in 1910
devoted much attention to the question of miners' phthisis.
From evidence submitted in a statement by Drs. Macaulay and
Irvine on the " Conditions affecting the Health of Underground Workers
on the Mines of the Witwatersrand ", the Commission reached certain
conclusions regarding the comparative mortality from the causes
specified below of underground workers and of adult non-mining males.
Taking the mortality from each of the causes specified amongst all
non-mining adult males on the Witwatersrand during the period 1905
to 1907 as unity, the comparative mortality amongst underground
employees for the same years is given as :
Phthisis, 6.3,
Other respiratory diseases, 1.7
All other diseases, 0.84.
The comparison is only an approximation, since the size of the two
populations compared was only approximately known, no determination
of the age distribution of the two populations compared was possible,
and deaths from phthisis amongst retired miners occurring outside the
Witwatersrand area were not included. The authors of the statement
referred to also showed that the age period of highest mortality from
phthisis amongst miners (thirty-six to forty years) fell somewhat later than
that amongst the general adult male population: this is now recognised
as a characteristic feature of " dust phthisis ". They also showed by
reference to data presented in a Report on Miners'1 Phthisis at Bendigo
by Dr. W. Summons that, although the deaths from phthisis apparently
affected a smaller proportional section of mine employees on the Rand,
the development of the disease appeared with us to be more rapid.
Over 80 per cent, of the phthisis deaths on the Rand lay between the
ages of thirty and forty-five, attaining a maximum between thirty-five
and forty. At Bendigo the main distribution lay more evenly between
forty and sixty-five, reaching a maximum between fifty and
fifty-five years.
(4) The next important item of evidence is furnished by the Report
of the " Miners' Phthisis (Medical) Commission " which was issued
in 1912. There were examined by this Commission 3,146 miners or
about 27 per cent, of all the miners employed. The Commission divided
cases of the disease into four stages. In the first of these, however,
there were no definite physical signs of its presence, and the tentative
diagnosis rested on symptoms and. history alone. Excluding these
doubtful cases, which amounted to 5.5 per cent, of the total number of
men examined, the number of those showing definite physical signs of
the disease amounted to 26.1 per cent, of the total. The majority of
these cases, however, showed no impairment of working capacity.
One cannot conclude from these figures that the true prevalence of
miners' phthisis was greater than it had been in 1903, neither on the
other hand can one find that any marked change had taken place since
the former date.

621

WITWATERSRAND : SILICOSIS STATISTICS

Machine men were, as expected, found to be the heaviest sufferers,
but no occupational group, including the supervisory staff was free
from risk of attack.
Of those whose mining experience had been gained solely in
South Africa, the average age of those slightly but definitely affected
was 35 years, with an average underground service of 7.2 years. For those
employed only in South Africa, and only on rockdrills, the corresponding
figures were 33.6 and 6.5 years. A prevalence rate of 26 per cent, amongst
the miners then employed would represent a total number of existing
cases of nearly 3,000.
(5) The Miners' Phthisis Act of 1912 introduced a system of compensation for those affected by the disease. From this date, therefore, we
have the additional information provided by the number of original
awards granted annually by the Miners' Phthisis Board to living miners.
These were as follows:
TABLE I.

ORIGINAL AWARDS FOR SILICOSIS OR

TUBERCULOSIS

WITH SILICOSIS GRANTED BY THE MINERS' PHTHISIS BOARD,

1912-1916

Year

First stage
silicosis

Second stage
silicosis,
including
tuberculosis
with silicosis

Total

1912-1913
1913-1914
1914-1915
1915-1916

698
1,087
912
540

1,632
993
367
243

2,330
2,080
1,279
783

Total, 1912-1916

3,237

3,235

6,472

Unfortunately only approximate conclusions can be drawn from
these figures regarding the probable production of " new " cases of
silicosis during these four years.
There certainly existed at the outset of the period a large number of
accumulated " cases, which had first arisen in previous years. The
figures also do not represent the outcome of a systematic examination
of all working miners, but are awards granted to those who made
voluntary application. Finally, owing to the system of medical
examination then employed, the medical standard of selection for awards
was far from being uniform.
But if we assume, as appears reasonable, that the number of
" accumulated " cases amongst working and retired miners was
about 3,000, the figures suggest that some 800 to 900 " new " cases were
arising yearly. Support is given to this deduction from the fact that
after some 6,500 cases had thus during these four years been awarded
compensation and debarred from continuing their employment underground, the Medical Bureau in 1916-1917 detected at " periodical " and
' benefits " examinations 907 cases of primary and secondary silicosis
amongst the miners who were actually at work during that year. This
deduction is merely an approximation. It suggests, however, that the

622

PAPERS PRESENTED TO THE CONFERENCE

number of cases of silicosis produced during each of these years was
about three times as great as that arising annually during the two
years 1927 to 1929.
II. — The Production of Simple Silicosis from 1917 to 1929
We possess in the annual Reports of the Miners' Phthisis Medical
Bureau accurate statistics of the production of silicosis since
1917-1918, based on the number of cases detected at the " periodical "
examinations of the working miners. The cases shown in these
returns do not quite represent all the " new " cases which have
arisen amongst the miners who have been at work since August
1917, since a certain number of miners, particularly in the first
two years of the period were first detected not at a " periodical "
but at a " benefits " examination. Since, however, these did not
amount over the whole period to as much as an additional 7 per cent.
the data obtained from the periodical examinations give a substantially accurate representation of the position.
Table II, reproduced from the Report of the Medical
Bureau for the year ending 31 July 1929, provides the general
data for the subsequent discussion. The salient features of this
table are shown also in block diagram in fig. 1 (p. 628), which hasbeen prepared by the kindness of Mr. H. Goodwin from the similar
diagram published in recent Bureau Reports.
It has been found convenient for the purposes of this discussion
to divide the returns into four triennial periods, each of which
is found to have certain characteristic statistical features. It will
be observed that the number of cases of tuberculosis with silicosis,
although very important during the first period, has since then
undergone a steady although not altogether uniform decline, and
during the fourth triennial period has become insignificant. Having
mentioned this fact, we propose to deal in this discussion solely
with the production of cases of " simple silicosis ".
This has shown, as will be seen from table II, col. 2, rather
remarkable variations from year to year, which require explanation.
It may be well therefore to have clearly in mind the factors which
may influence the figures of production in a population such as.
we are dealing with.
Factors which Influence the Production of Silicosis
Four such factors exist, the effect of each of which is independent
of that of the others.

623

WITWATERSRAND: SILICOSIS STATISTICS
TABLE I I . —

NEW CASES OF SILICOSIS, TUBERCULOSIS WITH SILICOSIS,

AND SIMPLE TUBERCULOSIS DETECTED

AT PERIODICAL EXAMINATIONS,

1917-1918 TO 1928-1929
Tuberculosis
Simple silicosis
with silicosis
Number
of cases
ProMiners
ProNum- duction
examin- Primary Ante- duction
ber
of
rate
ed
rate
and prim- per
cases
per
seary
cent.
cent.
condary
(3)
(5)
(4)
(1)
(2 a) 1 (2 6)

Simple tuberculosis

(6)

(7)

1917-1918
1918-1919
1919-1920

13,474
14,071
14,664

0.259
0.256
0.266

Total 1917-1918 to
1919-1920

42,209

35
36
39
(Open 18)
(Closed 21)
110

Annual average

14,070

1920-1921

13,641

1921-1922

13,450

1922-1923

12,689

Total 1920-1921 t o
1922-1923
A n n u a l average
1923-1924

Year
(1 August to 31 July)

1.179
153
349
2.539
398 (556) 2.787

900
(1,456)
300
(485)
17 219

2.195
3.551

116
120
24

0.861
0.852
0.163

260

0.616

Production
rate
per
cent.

0.260

1.757

0.125

254

1.951

0.178

255

2.049

0.150

39,780
13,260
12,159

752
251
1 318

1.916

0.151

2.652

60
20
20

1924-1925

12,587

427

3.438

0.222

1925-1926

12,823

490

3.859

0.055

1,237
412
0 364

3.328
2.691

55
18
2

0.146

1926-1927

37,569
12,523
13,654

1927-1928

14,726

283

1.941

0.000

1928-1929

15,492

270

1.761

0.032

Total 1923-1924 t o
1925-1926
A n n u a l average

Number of
cases

0.165

0.015

44
0.322
(Open 25)
(Closed 19)
22
0.164
(Open 14)
(Closed 8)
25
0.197
(Open 17)
(Closed 8)
91
0.228
30
11
0.090
(Open 10)
(Closed 1)
18
0.143
(Open 10)
(Closed 8)
61
0.476
(Open 30)
(Closed 31)
90
0.239
30
42
0.308
(Open 22)
(Closed 20)
32
0.217
(Open 23)
(Closed 9)
44
0.284
(Open 36)
(Closed 8)
118
0.269
39
1918-1919. With these-

Total 1926-1927 t o
43,872
917
2.111
7
0.016
1928-1929
14,624
306
2
A n n u a l average
i Three cases of secondary stage silicosis were detected in 1917-1918, and 2 In
exceptions the cases in col. (2 a) are primary stage cases only.
Note — The figures in brackets in col. (2) and (3) represent the numbers and rates of production which
would result from allotting the 556 " new " cases of ante-primary silicosis detected in 1919-1920 to the
three years 1917-1918, 1918-1919, and 1919-1920.

624

PAPERS PRESENTED TO THE

CONFERENCE

(1) The occupational and hygienic factors which produce the disease. —
It is obvious that the worse the underground conditions the greater
the number of cases of silicosis which will be produced, and the better
the conditions become the fewer the cases which will arise. But changes
in occupational conditions take time to produce their effects. The cases
of silicosis which actually arise in any year represent on the average the
cumulative effect of the occupational conditions obtaining during the
previous ten years or so. The average duration of underground service
in scheduled mines, worked by those miners who have actually in any
year become silicotic, has amounted during the years under discussion
to from nine years and five months at the beginning to twelve years
and eight months at the end of the period.
One cannot therefore account for the striking variations which are
shown in the production of simple silicosis during these twelve years by
corresponding sudden changes in the occupational factor. The effect
of the latter can only be approximately measured when the influence of
other disturbing factors has been excluded.
(2) Obviously also the number of cases produced will depend on the
number of working miners examined—these numbers are shown in
col. 1 of table I J. But what is of more importance from our point of
view is the number of miners working at each year of underground service.

TABLE III.

INCIDENCE RATES PER CENT. FOR SIMPLE SILICOSIS

AMONGST ALL MINERS WORKING IN EACH YEAR OF UNDERGROUND SERVICE IN THE PERIODS SPECIFIED

Years of
underground
service

—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
—
1
a

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20

Incidence rates
for primary
silicosis,

1918 t o 1920 1
(A)

0.00
0.03
0.08
0.21
0.74
1.78
2.97
4.21
6.00
8.94
13.00
13.91
14.28
14.46
14.56
14.60
14.58
14.48
14.33
14.13

Incidence rates
for ante-primary
silicosis, 2
1920 to 1923
(B)

The 'Standard' rates
0.00
0.03
0.05
0.14
0.34
0.85
1.55
2.70
4.12
5.00
5.60
6.10
6.50
6.79
6.98
7.06
7.10
7.11

7.09
7.04

Incidence rates
for ante-primary
silicosis,
1928-1929
(C)

0.00
0.00
0.00
0.06
0.22
0.46
0.77
1.22
1.81
2.55
3.24
3.70
4.09
4.51
5.31
6.22
6.52
6.70
6.75
6.68

Including 5 cases of secondary silicosis detected in this period.
Including 24 cases of primary silicosis detected in this period.
JVote. — The rates shown are " graduated " rates prepared from the observed data,
for the periods specified, published in the annual Reports of the Medical Bureau.

625

WITWATERSRAND: SILICOSIS STATISTICS

Other things being equal, the incidence of silicosis is a function of duration
of service, the liability to attack increasing with increase in the number
of years worked.
This feature is very clearly apparent in the data shown in table III.
If we select the results shown in col. B as a standard, chosen because
during these years the production of silicosis was fairly uniform, one
finds that at the fifth year of service the incidence was 0.34 per cent.,
at the tenth year 5 per cent, and at the fifteenth year 6.98 per cent. It
will be seen that up to the sixth year the incidence is very slight; these
" short service " miners, as Dr. Mavrogordato pointed out some years
ago, produce very little silicosis. But amongst the " long service " miners
with over six years' service, the incidence rises sharply thereafter to the
levels shown. It follows, therefore, that provided the incidence rates
remain constant over a series of years, the number of cases of silicosis
which are produced will directly depend almost wholly upon the number
of miners who are working in the later years of service. This is an
important consideration, inasmuch as since 1917-1918 the mining
population on the Witwatersrand has steadily become a more settled
population, and there has been in consequence a progressive increase
in the number of miners working in the later years of service.
This feature is clearly shown in table IV.
TABLE IV.

DISTRIBUTION OF WORKING MINERS IN THE

UNDER-

MENTIONED YEARS IN TERMS OF YEARS OF SERVICE WORKED

Year

Total
working
miners
examined

Total in 1st Total with
to 6th years
over six
Number
years of
of work
working
(' short serwork
in 7th to
vice' miners) (' long ser- 12th years
vice' miners)
(D)

Number
working
in 13th year
or over
(E)

(A)

(B)

1917-1918
1918-1919
1919-1920

14,519
14,719
15,056

10,719
10,345
9,868

3,802
4,374
5,188

3,929
4,668

445
520

1920-1921
1921-1922
1922-1923

13,470
13,282
12,542

8,146
7,146
5,914

5,324
6,136
6,628

4,881
5,551
5,890

443
585
738

1923-1924
1924-1925
1925-1926

12,026
12,449
12,698

4,469
4,772
4,792

7,157
7,677
7,906

6,127
6,395
6,321

1,030
1,282
1,585

1926-1927
1927-1928
1928-1929

13,525
14,582
15,333

5,667
6,683
7,470

7,858
7,899
7,863

5,919
5,502
4,943

1,939
2,397
2,920

(C)

It will be seen from these data (col. C) that whereas in 1917-1918 the
miners with over six years' service numbered only 3,672 or 26 per cent.
40

626

PAPERS PRESENTED TO THE CONFERENCE

of the whole, their number thereafter steadily increased to 7,906 in
1925-1926, since which date it has remained approximately constant.
But, even so, this " older " group of miners has itself been steadily
becoming " older " in general composition. In the first triennial period
the miners with over twelve years' service, who have the highest attack
rates, made up (col. E) only about one-tenth of the " long service " group.
In 1923-1924 they had risen to about one-seventh and in 1928-1929 to
well over one-third of all miners having more than six years' service.
Other things being equal, the effect of this remarkable change must have
been to cause a continuous increase in the number of cases of silicosis
arising from year to year. It has had such a result, but, owing to the fact
that other factors have influenced the position, it has not had the full
effect which it otherwise would have had. One such factor has been
a steady but not altogether uniform decline in the incidence rates at
each year of service, which is well shown in table III.
(3) The third factor which may influence the number of cases of
silicosis is a modification of the standard of selection of diagnosis of cases,
on the part of the medical examiners, i.e. in the present case on the part
of the Medical Bureau. If the Bureau improves its technical standard
of diagnosis, so that it is enabled to detect silicosis at an earlier stage
than formerly, there will naturally be for the time an increase in the
number of cases detected. But that increase, so far as it is material,
will be temporary only. A liberalisation in the standard of selection of
this nature only effects a material increase in the number of cases
detected when it is being applied for the first time, and when accordingly
two grades of the disease are being taken out at once. Once it has been
applied to the whole body of working miners, the temporary increase
practically disappears. A striking example of the effect of this factor
is shown in table II under the year 1919-1920, when the ante-primary
stage of the disease was first made compensatable. In that year there
were detected under the old standard (the primary stage) 398 cases
(col. 2 a), and under the new standard (the ante-primary stage) 556 cases
(col. 2 b) producing the high peak of 954 cases in all for this one year
alone (cf. fig. 1).
(4) A fourth factor which may influence the production of silicosis
is a possible alteration in the general physique of the working miners. This
factor has also been operative during the years under review, since the
effect of the initial examination of the Bureau has been to introduce into
the general body of working miners a specially selected body of men,
whom we call the " new Rand miners ", and who in 1928-1929 numbered
over 8,300 or 54.5 per cent, of the whole body. But the effect of this
intrusion did not make itself felt to any noticeable extent until well
after the period 1920 to 1923. Even in 1924-1925 only 716 of these men
had passed the six years' line and only an insignificant number had then
reached their ninth year of work.
These considerations make it plain t h a t in discussing the actual
production of silicosis during these twelve years one has to bear
in mind that there have been four independently variable factors
influencing the position, an alteration in any one of which will
affect the number of cases of silicosis which are detected from.
year to year.

WITWATERSRAND : SILICOSIS STATISTICS

627

Discussion of the Course of Production of Silicosis
from 1917-1918 to 1928-1929
Bearing these considerations in mind we may now consider in
detail the returns presented in table II and fig. 1.
Period 1917 to 1920. — It will be seen that during the first three years
there was a staircase rise from 153 cases of primary silicosis (with a very
few secondary stage cases) in 1917-1918 to 398 cases in 1919-1920, capped
by a peak of 556 cases of " ante-primary " silicosis in the latter year.
(1) The rise in the production of primary silicosis is not difficult to
explain. These were war years during which a large number of the
" long service " miners were absent on active service and their places
were filled by new recruits. With the termination of the war and the
return to work of many former miners the number of " long service "
miners (table IV, col. C) rose from about 3,800 in 1917-1918 to about
5,200 in 1919-1920. This fact explains a large part of the increase
although not all of it.
It was also found, however, that the attack-rate for silicosis amongst
the " long service " miners was in the two later years practically double
(6.79 and 6.84 per cent.) what it had appeared to be in 1917-1918
(3.42 per cent.). The difference is probably to be accounted for by the
fact that under the Act of 1916 it was not compulsory for the Bureau
when it found a miner to have silicosis to notify him to that effect.
As a consequence, many miners who were at work in 1917-1918, instead
of appearing at a periodical examination, applied for a benefits examination, and those who were found at such an examination to be silicotic
did not figure as they otherwise would have done in the " periodical "
returns. The return of cases of silicosis detected at periodical examinations
in 1917-1918 was thus artificially lowered. The Act of 1917 by making
it compulsory for the Bureau to notify all individuals who were found
at a periodical examination to have silicosis removed this source of
confusion in later years.
(2) The second feature of these three years is the very large total
return of cases of silicosis for 1919-1920. These figures, as we have said,
are the result of a change in the standard of diagnosis on the part of the
Medical Bureau. Up to 1919-1920 the standard of diagnosis had been
what was termed the " primary " stage of silicosis. It was based on the
implication of the Act of 1916 that some amount of disability should
be present before a case of silicosis was to be regarded as compensatable.
This attitude rested on the analogy of compensation for physical
" injury ". It was however soon felt that since silicosis is in the majority
of cases a progressive disease, the miners affected by it should become
compensatable at its " earliest detectable " stage, whether disability
was present or not. This change was introduced by the Act of 1919 and
the " earliest detectable " stage was labelled the " ante-primary "
stage. In 1919-1920 accordingly 556 cases of ante-primary stage silicosis
were detected, the majority being accumulated cases, although all may
reasonably be presumed to have arisen during the period 1917 to 1920.
The returns for 1919-1920 illustrate on a large scale the effect of a change
in the Medical Bureau's standard of diagnosis. The 556 cases of
" ante-primary " stage silicosis plus the 398 cases of primary stage
silicosis detected, made a total for the year of 954 cases.

628

PAPERS PRESENTED TO THE CONFERENCE

FIG.

PRODUCTION OF SILICOSIS IN ALL FORMS

FROM

1917-1918 TO 1928-1929
Hew cw$eo

Sunple

ô i l û s c o i o cuid óf

5 ¿ l t c o o w d e t e c t e d annually amoriqot

T u i h e r c u l o ^ i o »vitti

mineo

examined.

p e r i o d i c a l , e x e u n i n d t i o n o from 1917-16 onwardo, i n c l u d i n g fcfte
5 5 6 caoeo

cX A n t e - Ternary

SiUcoow-o f t r o t

detected,

-vrj

1920.
5 i m p l e SiHccoi-o
Tubercutooiô r à l n S ï l i c c o v î The 'Standard

Ling

Lifjbï

uobtokeo li 1700
b*x>ken

dra^o boriyDnVoJU*, a t the level 2 5 1

t e p e o e n t e *be av»truj« n u m b e r of «TOCO of S i m p l e S i l i c a t o de7«cled
frcm

1920 >o 1 9 2 5 .

D u r i n g >be y e a r o f r o m
h a û taXen p l a c a

1Ç25 - 2 4 o n w a r d o

a. o l e a d . ^

increaoe

ir» t h e n u m b e r of m i n e r a w o r k i n g in Ific lar>gef

p e r í o d o of u n d e r g r o u n d , s e r v i c e .
T h e 'Line o f E x p e c t e d I n c r e a s e ' i o d - i c a l e o ^b« Limih o f fbc i n c r e a o e
in c a o e o w b i c n > b i o f a c t o r w o u l d h a v e o c c a s i o n e d b a ¿ l m e a t t a c k
rcl&ô o b t a i n i n g ir? The - » V a n d a r d y e a o 1920 to *92S w/ncu'^ed forree«!
The s h a d e d portions of >be vettïcal colu-nrvd e c t £ n d i n g a b o v e tft*> t
Xùje of exceeded f^o«aoc , T, 'Aff ^ « a « rÇ2i ha i'iT.Q represent ifl* s^rp&o
rocifaö* io o o c o <3*>ïched. x b i c h w a o a t t r i b u t a b l e ta ifj« r*f¡i7ew*7t
" ; s&anúcua- of ¿U<ia-nc*oio employed by Hv b u r e a u
»r iamporajw <li«tu>baflCe i>3 proaiJcT'ior) o u a ^ a n c d , b y
>f?K>
•V lo «Seco ht» l».ve di-^CLppeaJ-s-d. irj lije rçhjrf) for l<}2ff -- 2Í7 . m e
nu*A QfcaXer iobkui^e >n c a * c o "5 Í Q i Q - 2 0 wB«.
y « a « of < ; t . - . - : - *—- <
neUcoJtfd. >>y 4h¿Uli>ro

_¿2S^
"

Si^'pii itmpßf
*!<9-. ;

19a1Q24

2.8
118

Símete

'•!¿7¿.

•564.';

eligís
427

19251016
7
190

'3*7
2

19271928

Simple Snlico3¿

1926'9*9
5
7.10

16+

Total St'Ti"G»«o

X i n e of
*Exp«cleCl '
Irxceaoe.

^«ar.
Caoeo
per
•5 c o r

1292.
1217

9tr

M7 ï
3»7

2«27
2111

T h r « yearly
Toïalo.

ft-odwcïiotv
m t * ò p+r
100,000.

WITWATERSRAND : SILICOSIS STATISTICS

629

Period 1920 to 1923. — The next three years witnessed a remarkable
change. The obvious temporary " skimming " effect of the introduction
of a more liberal standard of diagnosis has disappeared and the
production falls in a very striking way. Further, although the number
of " long service " miners continued to increase from about 5.200 in
1919-1920 to some 6,600 in 1922-1923 (table IV, col. C), and one would
therefore have expected that the number of cases of silicosis would also
have increased, this did not happen because simultaneously the attack
rale for silicosis amongst the " long service " miners jell. Their attack rate
had averaged, in the first three years, 5.8 per cent. — it fell to an average
of 3.8 per cent, in 1920 to 1923. It dropped quite suddenly from
6.8 per cent, in 1919-1920 to 3.9 per cent, in 1920-1921. One may regard
the first three years as having been the last in which the production
substantially reflected the cumulative effect of the conditions which had
obtained in the period from 1906 or 1907 onwards to the date of the
detection of these cases. The second three years represent the culmination
of the first decade of the better conditions, which began about 1911
and 1912. A comparison of the rates of incidence per year of underground
service shown for the cases detected in these two respective periods in
table III, cols. A and B, confirms the view that we are here dealing with
two different types of case, two different " generations " of miners.
It must be remembered in this connection that in few cases, particularly
in these earlier years, was a miner's service unbroken.
At all events the one tendency—a fall of 35 per cent, in the average
attack rate of the " long service " miners—cancelled the effects of the
other, namely, a 35 per cent, increase in their average number, and the
production of silicosis remained practically stationary. The standard of
diagnosis of the Medical Bureau also remained practically the same for
these three years so that no disturbing influence arose from this factor.
The production of silicosis during this period was thus moderate and
fairly uniform. We have therefore selected these years (1920 to 1923)
as " standard years " by reference to which the production of silicosis
in the succeeding years could be measured, and with this object we have
taken the rates of incidence at each year of service worked which
obtained during this period, and which are shown in table III, col. B,
as " standard rates " of incidence.
Period 1923 to 1926. — The next three years show a different state of
affairs. There is again a staircase rise in the production of silicosis to a
second peak of 490 cases in 1925-1926 comparable on a smaller scale to
the peak of 1919-1920, and due in part to a similar cause. The total
increase in these three years over the annual average of 251 cases for the
" standard " years 1920 to 1923 was 485 cases in all (table II, col. 2).
This increase aroused some alarm and created some misgiving as to the
efficacy of the preventive measures employed. But, as Dr. Mavrogordato
was the first publicly to point out, ithad quite an innocent explanation.
The position has been fully analysed in the recent Reports of the Medical
Bureau. The falling attack rates (3.9, 3.8 and 3.7 per cent.) of the
" long service " miners during this period did not at all suggest that
occupational conditions had in recent years altered for the worse.
The explanation of the increase lay in quite another direction. Reference
to table IV will show that there had been going on during these years
a steady increase in the number of miners at work in the later periods
of underground service in which the liability to silicosis is highest.
Making the assumption that the attack rates at each year of underground
service which had obtained in the period 1920 to 1923 had remained

630

PAPERS PRESENTED TO THE CONFERENCE

constant, one applied these rates to the number of miners working at
each corresponding respective year of underground service during each
of the three official years 1923 to 1926. The result was to show an
" expected " increase during these respective years of 60, 95 and
120 cases or 275 cases in all, constituting 57 per cent, of the total increase
of 485 cases. (Cf. table V.)
TABLE V. —

COMPARISON OF ACTUAL AND " E X P E C T E D " INCREASE

IN CASES OF SIMPLE SILICOSIS, 1 9 2 3 TO 1 9 2 9
Actual less expected
Year

Actual

Expected

Annual average,
1920-1923
(standard)

251

1923-1924
1924-1925
1925-1926

319
428
490

311
346
371

1926-1927
1927-1928
1928-1929

364
283
270

387
410
426

Plus

Minus

8
82
119
23
127
156

There still remained, however, a considerable surplus increase of
209 cases, 8, 82 and 119 in the respective years, which could not be
explained in this way. The residual increase was attributable to a
second factor which became operative during these years, namely,
to a further liberalisation in the standard of diagnosis of the " earliest
detectable " stage of silicosis, which was attained during this period by
the Medical Bureau owing mainly to improvements in radiographic
technique, and to the consequent possibility of a more exact correlation
of the results of clinical, radiographic and pathological investigation
in a large series of individual cases. The operation of this process,
which was substantially completed in 1925-1926, was to repeat, although
on a smaller scale, the peak of 1919-1920. Since December 1925, the
effects of the process described have been accentuated to some extent
by the additional cases resulting from the decisions of the Medical
Board of Appeal, which commenced its work at that date. These are
included in and go to augment the returns shown in table II.
From the result of this investigation it was possible to predict that
the temporary increase due to the operation of this process of deeper
selection of cases would shortly disappear. This prediction was realised.
In 1926-1927 the number of cases of simple silicosis detected dropped
from the 490 cases of the previous year to 364.
Period 1926 to 1929. — The next three years show a decided falling
tendency in the production of silicosis (table II, col. 2).
The sudden drop of 126 cases in the production for the year 1926-1927
was attributable mainly to the substantial completion of the process of
deeper selection of cases by the Medical Bureau, which had been proceeding
during the previous years. Some such fall had been predicted. But

WITWATERSRAND: SILICOSIS STATISTICS

631

reference to table V shows that not only had the obvious surplus increase
due to this factor totally disappeared, but that the actual number of cases
had dropped below the " expected " number by 23. The further fall
to 283 cases in 1927-1928 and to 270 cases in 1928-1929, is even more
satisfactory because it has been effected in face of a further increase in the
number of miners working in the later years of service (table IV). In
1925-1926 there were at work 1,585 miners with over twelve years'
service—in 1928-1929 their number had risen to 2,920.
If one makes allowance for the influence of this latter factor
one may state, with entire confidence, that the true production
of silicosis when measured, as it can only accurately be measured, by the
respective incidence rates of the disease amongst miners at work in the
corresponding respective years of underground service, has undergone
a decided improvement since the period 1920 to 1923. Reference to
table V or fig. 1 will show that had the rates of the " standard " period
remained constant, the number of cases of silicosis to be " expected "
in 1928-1929 would have been 426 — they were actually instead 270,
a decline below the " expected " number of over 36 per cent. The
comparative rates of incidence are given for 1928-1929 and 1920 to 1923
in table III. When, further, one compares the former with the rates
obtaining for the primary stage of the disease in 1918 to 1920 the improvement is even more decided. In this respect it is well to note that
90 per cent, of the 270 cases of silicosis detected in 1928-1929 had.
commenced work on the Rand prior to August 1916, prior, that is, to
the commencement of the " present-day " period of preventive policy.
The figures appear to indicate that there has been, during the past three
years, a decided fall in the true incidence rates of the disease similar
to that which occurred after 1919-1920. It is mainly in these later
years that one would expect the results of the improved preventive
policy introduced in 1916-1917 to effect a substantial modification of
the production of the disease.
The Present Position and the Future Outlook Regarding
the Production of Simple Silicosis
It is important from the point of view of the outlook regarding
the probable course of production of silicosis in the near future to
analyse a little more fully the reasons for the decline below the
" expected " standard during the past three years. The actual
amount is indicated in the last vertical column of table V, and
in fig. 1.
For this purpose it is desirable to follow the recent practice of
the Medical Bureau, and divide the body of working miners into
three classes for separate consideration. These classes are:
Class A — " new Rand miners ", i.e. miners who have worked only in
the mines of the Witwatersrand, and only since 1 August 1916.
Class B — " old Rand miners ", i.e. miners who have worked only in
the mines of the Witwatersrand, but who commenced work before
1 August 1916.
Class C — " miners, Rand and elsewhere ", i.e. miners who have
worked on the mines of the Witwatersrand and also in mines elsewhere.

632

PAPERS PRESENTED TO THE

CONFERENCE

The particular importance of Class A lies in two facts: (1) that
all of these miners have passed the " initial examination " of
the Medical Bureau, and (2) that they have been exposed solely
to the improved occupational conditions existing since 1916, and
have not been affected in any way by mining work elsewhere. This
class is naturally a growing one and numbered, in 1928-1929,
8,360 out of the total of 15,333 working miners at that date, or
54.5 per cent. Nevertheless, no miner of Class A had at that date
worked for more than thirteen years, and only an insignificant
number had reached their thirteenth year of service. In time, but
not for a very considerable time, the production of simple silicosis
for all miners will depend mainly on the production in this class.
Class B has formed in the past the most numerous group, but
it is naturally a decreasing class, and in 1928-1929 it included
only 5,672 persons, or 37 per cent, of the total body of working
miners. It is still, however, the most important group for the
production of silicosis, contributing 197 of the 270 cases of simple
silicosis which arose during that year.
Class C is likely always to be a small class, the number of miners
included in it in 1928-1929 being 1,301, or 8.5 per cent, of all the
working miners. But it contributed during the year more than
its proportionate quota of cases.
TABLE VI.

COMPARISON OF ACTUAL AND " E X P E C T E D " CASES IN

THE THREE

CLASSES OF WORKING MINERS, DURING THE

YEARS 1926 TO 1929
Cases of simple silicosis
Year

Class A
Actual

1926-1927
1927-1928
1928-1929

Totals
Actual less expected
Ratio of actual to
expected

Class B

Expected

Actual

Expected

Class C
Actual

Expected

9
11
22

48
67
84

301
215
197

293
297
295

54
57
51

46
46
47

199

713

885

162

139

—1172

21 °/
/o

81 /o

— Ì

117 °/
/o

WITWATERSRAND : SILICOSIS STATISTICS

633

A comparison of the " expected " cases, according to the production rates for the standard years 1920 to 1923 (table III, col. B)
with the actual cases of simple silicosis arising in each of these
three classes during the past three years leads to the following
interesting results.
It is only necessary to emphasise here the very low production
in Glass A. This production, however, is as yet dependent upon
the rates for the first thirteen years of service only. For that
period the incidence rates for each year are for this class very much
below the rates for the other two classes, and the curve of incidence
does not as yet show any tendency to swing upwards to meet the
curves of the other classes in later years. But it is impossible to be
too definite with regard to the future. One cannot, of course,
anticipate that production rates of the same low order will continue
when the " new Rand miners " advance into the later years of
underground service. But there is no reason to suppose that even
then their incidence rates will reach the relatively higher rates
hitherto shown by the two other classes, since the causes producing
such low production in the past should have a similar effect at later
years of service.
The difference in production rates between the " new " and
the " old Rand miners " is due to the facts that the former are
specially selected men, and that they have throughout their total
period of service been subjected to improved occupational conditions.
There are no data which enable one to state how much of the
difference can be ascribed to each of these causes. One may
reasonably ascribe the decline below the " expected " production
which has likewise become evident during the past two years
amongst the " old Rand miners " (table VI) to the fact that with
each succeeding year a larger proportion of the service of the
members of this group also has been passed under improved
occupational conditions. The higher production of the " miners,
Rand and elsewhere " may reasonably be ascribed to the effect of
previous mining work elsewhere.
All of this is re-assuring; nevertheless we must add a word of
caution. Although one is justified in concluding that the Rand has
turned a big corner in the matter of silicosis, one does not anticipate
that the actual number of cases detected will show any significant
further decrease in the immediate future. For although the
" new Rand miners " with their relatively lower attack-rates arcbecoming more numerous, nevertheless the older miners who
remain — and there are still over 5,000 of them — are every year

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growing older in years of service, and therefore more liable to
contract silicosis. The one factor will probably for some time
balance the other, and one does not therefore anticipate much,
if any, actual decrease in the number of " new " cases of simple
silicosis which will arise for some years to come. That is the
position to-day.
One may in conclusion discuss briefly certain other minor factors
that may or may not influence production.
The age of the miner would not appear to exert much influence
upon production, the data being inconclusive.
It is similarly not possible to say whether miners born in South
Africa are subject to higher or lower production rates than those
born overseas. The evidence indicates that there is no significant
difference.
The particular class of underground occupation engaged in is
certainly an important factor in production. No satisfactory
statistics have however been accumulated on this subject, partly
because such information has not been required for any particular

TABLE VII.

NEW CASES OF SIMPLE SILICOSIS DETECTED

AMONGST MINERS

WHO HAVE WORKED UNDERGROUND ONLY IN SCHEDULED MINES, DISTINGUISHING BETWEEN MACHINE-DRILLERS AND OTHERS WITH PRODUCTIONRATES PER CENT. •— 1 AUGUST 1 9 2 7 TO 3 1 JULY 1 9 2 8
Machines only

Machines and other work
Over 50 %
machines

No machines

Up to 50 %
machines
Cases
Number
of
exam- silicosis
ined and proandpercentage ductionrate
of total percent.
(7)
(6)

Number
examined
and
percentage
of total

Cases of
silicosis
and
productionrate
per cent.

(1)

(2)

(3)

U p t o 6 t h year

6,255

55
(0.88)

0
(0.000)

465
(7.43)

1
(0.215)

1,085
0
4,650
2
(17.35) (0.000) (74.34) (0.043)

7th to 12th
year

5,023

6
47
(0.93) (12.766)

736
(14.65)

37
(5.027)

2,466
1,794
57
13
(48.70) (2.330) (35.72) (0.725)

13th t o 18th
year

1,876

19
2
(1.01) (10.526)

245
913
47
699
26
27
(13.06) (11.020) (48.67) (5.148) (37.26) (3.720)

Period Worked

Total
miners
examined

Number
examined
and percentage
of total
(4)

Cases of
silicosis
and productionrate
per cent.
(5)

Number
examined
and percentage
of total

Cases
of silicosis
and productionrate
per cent.

(8)

(9)

WITWATERSRAND: SILICOSIS STATISTICS

635

purpose, and partly because miners frequently change from one
class of occupation to another. The respective proportions of
miners engaged in occupations that are more or less hazardous
probably do not differ appreciably from year to year, although
in each year they may be made up of different individuals, and the
factor of occupation has therefore not influenced statistics dealing
with the miners as a whole. There can be no doubt, however,
that production is higher among machine-drillers, and amongst
those handling broken rock, than amongst those in other occupations, and the factor of occupation would need to be taken into
account should the financial system be revised to include differential
payment according to occupation. Table VII, showing the
production of silicosis for the year 1927-1928 for machine-drillers
and others, is of interest (it is taken from the Bureau Report for
the year ended 31 July 1928, page 25).

III. — The After-History of Cases of Silicosis and the Progression
of the Disease
It has been shown that there has been a considerable decline
in the production of silicosis, but unfortunately this has not been
accompanied by a corresponding fall in the progression of silicosis,
and instead the disease has become of a more infective, and therefore of a more progressive, type. This phenomenon has been
discussed in other papers of this series. It may indeed be stated
that the importance of the production of a new case of silicosis
in the ante-primary stage lies, not in the fact that the miner has
silicosis in that stage, but in the likelihood that the disease will
progress, first to the primary stage and then to the secondary
stage, within a relatively short period.
It thus becomes of importance to measure the rate of progression
of the disease. The progression is measured by the " stages "
of the disease, and for this purpose the " secondary " stage is
treated as including cases of silicosis plus tuberculosis.
Comparison of Progression in Cases originally Certified Respectively
as Primary and as Ante-Primary Silicosis
The following table traces the subsequent history (so far as it is
known) of 895 cases originally certified as being in the primary

636

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stage of silicosis during the three years from 1 August 1917 to
31 July 1920:
TABLE VIII.

SUBSEQUENT HISTORY OF ORIGINAL PRIMARY STAGE

CASES CERTIFIED DURING THE THREE YEARS

1917-1920

Died during year
Transfers
while
to
Total
secondsurviv- ary stage
ing
in
in
during
primary secondprimary secondyear
stage ary stage
stage ary stage
Surviving as

New
End
„
„
„
„
„
,,
„
,,

cases
First year
Second year
Third year
Fourth year
Fifth year
Sixth year
Seventh year
Eighth year
Ninth year

895
781
718
645
595
532
456
390
324
289

895
854
816
777
730
696
648
602
557
523

73
98
132
135
164
192
212
233
234

84
48
60
41
53
62
51
52
24

11
23
26
38
24
34
31
31
23

30
15
13
9
10
14
15
14
11

iVole. — The first year represents a period of between one year and two years and averages
about eighteen months.

The percentage of these original primary cases surviving in the
primary and secondary stages, and the percentage who have died
from the outset, at the end of the third, sixth and ninth years
respectively are as follows :

Percentage
Surviving as p r i m a r y
„
„ secondary
Died while primary
„
„
secondary

End of
third year

End of
sixth year

End of
ninth year

72.1
14.7

51.0
21.4

32.3
26.2

6.5
6.7

10.2
17.4

14.6
26.9

The following table traces the subsequent history (so far as it is
known) of another group of cases, namely, the 728 cases originally
certified as being in the ante-primary stage of silicosis during the
three years 1920-1923, and the 1,235 cases similarly certified in the
ante-primary stage during the three years 1923-1926:

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WITWATERSRAND : SILICOSIS STATISTICS
TABLE IX.
CERTIFIED

SUBSEQUENT HISTORY OF ORIGINAL ANTE-PRIMARY

RESPECTIVELY

DURING

THE PERIODS

Transfers during year to

Surviving as
anteprimstage

Total
prim- second- surviving
ary
ary
stage
stage

Certified during th e period 1920-192 Ì
728
New cases
—
—
636
22
46
End First year
542
100
37
„ Second year
429
161
70
„ Third year
320
105
197
„ Fourth year
241
208
140
„ Fifth year
192
198
167
„ Sixth year
Certified during th e period 1923-192
1,235
New cases
—
1,016
116
End First year
774
283
„ Second year
593
376
„ Third year

—
49
81
129

CASES

1 9 2 0 - 1 9 2 3 AND 1 9 2 3 - 1 9 2 6
Died during year while

in
prim- second- anteprimary
ary
ary
stage
stage
stage

in
in
prim- second stage stage

728
704
679
660
622
589
557

46
63
86
81
59
32

28
30
45
59
62
47

18
7
5
8
5
9

—
3
2
6
1
3

6
15
12
24
27
20

1,235
1,181
1,138
1,098

117
195
159

56
56
71

46
16
11

1
3
6

7
24
23

Note. — The first year represents a period of between one and two years and averages about eighteen
months.

The percentages of these original ante-primary cases surviving
in the various stages, and the percentages of those who have
died from the outset, at the end of the third and sixth years,
are as follow:

End of
third year

End of
sixth year

1923-1926
cases :
End of
third year

59.0
22.1
9.6

26.4
27.2
22.9

48.0
30.5
10.4

4.1
.7
4.5

7.1
2.1
14.3

5.9
.8
4.4

1920-1923 cases
Percentage

Surviving as ante-primary
„ primary
„
,, secondary
Died while ante-primary
„
primary
„
„ secondary

These figures lead to certain interesting comparisons. At the
end of the sixth year, out of the 895 original primary cases
certified during the three years 1917-1920, 27.6 per cent, had
died and 21.4 per cent, survived in the secondary stage, while
out of the 728 original ante-primary cases certified during the

638

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three years 1920-1923, 23.5 per cent, had died and 22.9 per cent.
survived in the secondary stage. Bearing in mind that the anteprimary stage is an earlier stage of the disease than the primary
stage, the comparison shows that there has been a higher rate of
progression among original ante-primary cases, and it exemplifies
the change in the form of the disease to a more infective type.
A comparison of the percentages " surviving " and " died " at
the end of the third year for original, ante-primary cases certified
respectively during the three years 1920-1923 and during the
three years 1923-1926 shows that the change to a more infective
type of disease has continued within recent years.
These conclusions might have been reached by other methods.
If the original ante-primary cases be traced until they die in the
ante-primary stage or until they progress to a further stage, the
average annual rate of progression among those surviving in the
ante-primary stage at the beginning of each year is, to the primary
stage 17.2 per cent., to the secondary stage 3.0 per cent., total
20.2 per cent. The first year (averaging eighteen months) following
the date of certification has been omitted, since for this period
there is a halt in the progression of the disease, the total annual
rate of progression being only 8.2 per cent. If the primary cases
who have been transferred from the ante-primary stage be similarly followed until they die in the primary stage or until they
reach the secondary stage, the average annual rate of progression
to the secondary stage among those surviving in the primary
stage at the beginning of each year is found to be 20.2 per cent.
This rate of 20.2 per cent., applicable to the progression to the
secondary stage of primary stage cases who have been transferred
from the ante-primary stage, may be contrasted with the annual
rate of progression to the secondary stage applicable to original
primary cases certified during the three years 1917-1920, which
was found to be 8.3 per cent.
The reasons for these results have already been discussed.
The original ante-primary cases, and particularly those certified
in more recent years, are representative of a different body of
miners from those originally certified in the primary stage
during the three years 1917-1920, they have worked under
different conditions during the greater part of their underground
employment, and they are subject to a more infective type of
silicosis.
It is desirable to emphasise an important change that has
taken place in the general body of miners. In the early days

WITWATERSRAND : SILICOSIS STATISTICS

639

the immense majority of the miners were men of overseas birth
who had been drawn from older mining communities which had
long been industrialised, but in later years, and especially since
1907, there has been a steady increase in the number of South
African-born miners, who are drawn mainly from the rural districts, and who now constitute over 70 per cent, of the working
miners. When a pastoral or agricultural population turns to
industry, a rise in the tuberculosis rate of that population is to
be expected, and this rise will be accentuated if the industry
selected should be a phthisis-producing industry. This, as
Drs. Mavrogordato and Irvine have recently put it, is largely
the position in South Africa to-day. Although the increasing
proportion of South African-born miners has apparently not led
to an increase in the production of new cases of silicosis, there
can be little doubt that it has been an important influence in the
change in the nature of the disease to a more infective and
progressive type.
The annual rate of mortality amongst ante-primary cases while they
remained in the ante-primary stage, but excluding the first year,
averaged 1.7 per cent. During the first year, when the rate of
progression was low, the annual rate of mortality was 2.3 per cent.
The annual rate of mortality among primary cases transferred from
the ante-primary stage, while they remained in the primary stage,
was 1.9 per cent.
The corresponding annual rate of mortality
among the cases originally certified primary during the period
1917-1920, while they remained in the primary stage, was
2.3 per cent. These figures do not call for any remark except
that a low rate of progression would appear to be accompanied
by a rather higher rate of mortality.
Mortality of Miners in the Secondary Stage of Silicosis
It is more important to consider the mortality of miners in the
secondary stage, where the " secondary " stage has again been
taken to include cases of silicosis plus tuberculosis. Miners in
the secondary stage have since 1 August 1919 received monthly
allowances, and a mortality experience was taken out in respect
of all such miners, whenever certified, who were in receipt of
allowances during the nine years from 1 August 1919 to 31 July
1928; the experience covered 3,438 cases.
This investigation showed the following features:

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(a) The most important factor influencing mortality was the period
that had elapsed since miners were certified in the secondary stage.
(b) The ages of the miners were not a material factor, except at very
old ages, but the number of such miners was too small to influence the
general results.
(c) The mortality among miners with silicosis plus tuberculosis
was much heavier than among miners with silicosis in the secondary
.stage without tuberculosis.
(d) The mortality among miners certified in the later years under
review was lower, after taking into account the period elapsed since
-certification, than among miners certified in the earlier years.
These features, with the exception of t h a t mentioned under (b),
have now to be considered.
(a) The rates of mortality according to the period elapsed since
certification, calculated in respect of cases certified after 31 July
1919, were as follow:

Year after
certification

Annual rate of
mortality per cent

1st
2nd
3rd

18.7
21.3
19.1

4th
5th
6th

20.1
18.2
14.5

7 th
8th
9th

14:5} 9.0

16.2

(b) It will be observed t h a t the mortality is very heavy for
•some years following certification, but the survivors after a
number of years are subject to lower rates. This feature of the
lower mortality among the relatively few survivors after some
years is seen more clearly by considering the cases who were in
the secondary stage prior to 1 August 1919, and who are dealt
with in (c) below.
(c) The mortality was calculated separately for cases of silicosis
plus tuberculosis, and for cases of silicosis in the secondary stage
without tuberculosis, in respect of miners who were granted

641

WITWATERSRAND : SILICOSIS STATISTICS

allowances as from 1 August 1919 and who were in the secondary
stage prior to that date; the results are as follow:
Annual rate of mortality per cent.
Year from
1 August 1919

Silicosis plus
tuberculosis

Silicosis in secondary
stage without tuberculosis

1st
2nd
3rd

21.9
20.3
15.3

9.8
10.6
9.0

4th
5th
6th

12.1
14.8
12.7

9.8
7.9
9.2

7 th
8th
9th

13.1
10.1
7.9

7.8
9.3
6.5

This table gives results which were to be expected, but the
table is also of interest in showing the lower rates of mortality
among survivors who had been in the secondary stage for some
years.
(d) The feature of decreasing mortality according to the year
of certification is shown in the following table, which gives, in
respect of cases certified in the secondary stage after 31 July 1919,
the percentage of the actual deaths that occurred to the deaths
that would have been " expected " on the basis of the mortality
for all years combined.

Year certified
secondary

Percentage of actual
to expected deaths

1919-1920
1920-1921
1921-1922

110
137
99

1922-1923
1923-1924
1924-1925

95
119
89

1925-1926
1926-1927
1927-1928

88
75
88

All years

100
41

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This feature of decreasing mortality is thought to be temporary.
It will be observed that the mortality of the last four years has
remained fairly constant, and having regard to the more progressive type of disease shown in recent years, it would appear
that the mortality of future secondary cases should tend to be
higher.
Average Expectation of Progression in Cases Originally
Certified as Ante-Primary Stage Silicosis
A general summary of the results relating to the progression
and mortality of ante-primary cases certified from 1920-1921
onwards may be given in an interesting way. The average period
spent by a miner in the ante-primary stage, from the date of
certification until he dies in that stage or until he progresses to
a further stage, is 4.59 years. For a miner transferred to the
primary stage from the ante-primary stage, the average period
spent in the primary stage, from the time he is certified primary
until he dies in that stage or until he progresses to the secondary
stage, is 3.85 years. The average period spent by such a miner
in the secondary stage, from the time he is certified secondary
until he dies, is 7.26 years.
The average future lifetime of a miner certified in the anteprimary stage cannot, of course, be obtained by adding together
these three separate periods of years, because to do so would
leave out of account the fact that those dying while in the anteprimary or primary stage could have no lifetime in a further
stage or stages, and also the further fact that those progressing
direct from the ante-primary stage to the secondary stage could
have no lifetime in the primary stage. The figure has been
correctly calculated, and the average future lifetime, or expectation of life, of a miner certified to be in the ante-primary stageis 13.66 years.
Mean Duration of Underground Work and Average Working
Lifetime of a Miner
The mean duration of underground service in all the new casesof silicosis which have arisen amongst those miners who have
worked only in scheduled mines is shown below for each year
since 1918-1919 (the data are extracted from the Reports of the;
Medical Bureau):

WITWATERSRAND : SILICOSIS STATISTICS

Year certified

643

Mean duration of
underground service

1918-1919
1919-1920
1920-1921

9
9
9

2
6
1

1921-1922
1922-1923
1923-1924

9
9
10

7
5
3

1924-1925
1925-1926
1926-1927

10
10
11

3
10
9

1927-1928
1928-1929

12
12

1
8

The increase in the mean duration of underground service is
due not only to an improvement in underground conditions, but
to two other factors. The first of these factors is the progressive
intrusion into the body of working miners of a specially selected
group with relatively low attack-rates for the disease, namely,
the " new Rand miners ". The second influence is to be found
in the fact that the mining community has become more and
more a settled community with a continually increasing proportion
of miners with relatively long periods of underground service. Even
allowing for these two factors, however, the increase in the mean
duration of underground sen ice is undoubtedly a satisfactory
feature.
Although the mean duration of underground service among
miners contracting silicosis is of interest and has to be recorded,
it has to be pointed out that this mean duration does not represent
the average working lifetime of a miner, since it leaves out of
account the fact that many miners still working with relatively
long periods of underground service have not yet contracted
silicosis, and also the further fact that a number of miners have
left underground employment without contracting silicosis. It is
necessary, therefore, in considering the true average working
lifetime of a miner, to take these further factors into account.
The question of the average working lifetime is a difficult one
to answer. In the first place, the rate of production of silicosis
has been changing, and it is necessary to adopt a reasonable basis
for production; it was assumed that the rates of production of
simple silicosis during the year 1928-1929 would apply throughout

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the miner's working lifetime. Secondly, a miner may give up
underground employment owing to the contraction of simple
tuberculosis or of silicosis plus tuberculosis, the average rates
found to be applicable within the last few years were here adopted.
Thirdly, underground employment may be terminated owing to
death, which might occur through a mine accident or for some
other reason, or employment may be terminated through a
breakdown in health owing to a mine accident or otherwise.
Fourthly, it was presumed that miners would not voluntarily give
up underground work. On this basis (and the assumptions appear
to be reasonable) a miner might expect to have a working lifetime
of nearly eighteen years. We are of the opinion that this average
working lifetime of nearly eighteen years represents fairly the average
conditions existing at the present time.
It should be added that a miner commencing work now could
anticipate an average working lifetime considerably exceeding
eighteen years. It is impossible to state with any degree of definiteness what his future working lifetime is likely to be, since the
rates of production of " new Rand miners " are available for only
the first thirteen years of their underground service, and it is
impossible to say what the rates will be in later years, but there
can be no doubt that it will be considerably in excess of eighteen
years.
IV. — The Prevalence of Silicosis and Tuberculosis amongst
Native Labourers on the Gold Mines of the Witwatersrand
A brief reference may be made in conclusion to the general
statistics which are available regarding the prevalence of silicosis
and tuberculosis amongst native mine labourers.
Table X shows the general data regarding the prevalence of
simple silicosis, tuberculosis with silicosis, and simple tuberculosis
amongst native mine labourers employed on the mines of the
Witwatersrand since 1916-1917. The general system of detection
of these conditions amongst mine natives has been described in
other papers in this series.
A comparison of the returns here presented with those for
European miners in table II shows several very striking differences.
Although in the first two years 1917-1918 and 1918-1919 a
very considerable number of cases of silicosis complicated with
active tuberculosis was detected amongst the European working

TABLE

X. —

PREVALENCE

SIMPLE

SILICOSIS,

TUBERCULOSIS WITH

SILICOSIS, AND SIMPLE

TUBERCULOSIS

AMONGST NATIVE LABOURERS IN THE GOLD MINES OF THE WITWATERSRAND, 1 9 1 6 - 1 9 1 7 TO 1 9 2 7 - 1 9 2 8
19161917

19171918

19181919

19191920

19201921

19211922

19221923

19231924

19241925

19251926

19261927

19271928

Average number all mine
191,202 180,415 171,959 178,571 168,547 160,600 179,182 178,006 179,881 177,368 184,937 193,976
natives
A. — Cases simple silicosis detected
Prevalence rate per cent.

91
0.047

31
0.017

47
0.027

126
0.070

134
0.079

45
0.027

75
0.041

119
0.066

85
0.047

201
0.113

238
0.129

209
0.108

B. — Cases tuberculosis
with silicosis detected
Prevalence rate per cent.

252
0.131

232
0.128

378
0.219

394
0.220

276
0.163

203
0.126

327
0.182

312
0.175

359
0.200

434
0.245

409
0.221

397
0.204

C. — Cases simple tuberculosis detected
Prevalence rate per cent.

1,103
0.576

946
0.524

789
0.458

794
0.444

810
0.480

580
0.361

663
0.370

585
0.328

456
0.253

561
0.316

787
0.425

746
0.385

0.178

0.145

0.246

0.290

0.242

0.153

0.223

0.241

0.247

0.358

0.350

0.312

0.707

0.652

0.677

0.664

0.643

0.487

0.552

0.503

0.453

0.561

0.646

0.589

0.754

0.669

0.704

0.734

0.722

0.514

0.593

0.569

0.500

0.674

0.775

0.697

Combined prevalence
rates per cent. :
Silicosis in all forms (A 4B)
Tuberculosis in all forms
(B + C)
All compensatable diseases (A + B + C)

Note. — The returns for 1924-1925 onwards do not as in previous years include cases detected amongst the small numher of Eurafrican miners.

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miners, the number of cases of that condition has markedly
declined since that date, and during the past three years has
practically reached vanishing point. The number of cases of
" open " or active simple tuberculosis arising amongst European
miners has never for the last three triennial periods averaged
more than 0.18 per cent. The overwhelming majority of cases
of compensatable disease amongst European miners since
1919-1920, have been when first detected cases of simple or
uncomplicated silicosis.
The reverse is true of the native mine labourers, amongst whom
the great majority of cases of compensatable disease are cases of
active simple tuberculosis, or, in those with longer service, of active
tuberculosis preceded or accompanied by an element of silicosis.
The incidence of simple silicosis amongst the mine natives is
relatively small. The low figures for the prevalence of this condition
recorded for the first nine years may present an underestimate
of the true position, since at that time no systematic investigation
of the prevalence of silicosis amongst mine natives was made. But
in 1926 a systematic annual radiographic examination of all natives
with more than five years' service on any one mine was instituted
by the Chamber of Mines. The result, as the figures from 1925-1926
onwards indicate, has been to secure the detection of a considerably
larger number of cases of simple silicosis, but the prevalence rate
for this condition still remains low as compared with that amongst
European miners. It is not that the native labourer is less
susceptible to silicosis than the European miner, given an equal
intensity and an equal duration of exposure to dust. This was
shown by Dr. Watkins-Pitchford in the Bureau Report for
1923-1924. The difference is to be explained by the fact that
the service of the mine native is in general much shorter and less
continuous than that of the European miner.
On the other hand, the higher susceptibility of the African
native to tuberculosis is a matter of common knowledge, and
that disease frequently assumes in the native the acute " infantile "
type, particularly amongst new or recent recruits. Even so,
when judged by European or American standards, the incidence
of tuberculosis amongst mine natives, even when taken to include
cases of active tuberculosis with silicosis, is not alarming. But the
actual number of cases is considerable. It amounted in 1927-1928
to over 1,100 cases, each a potential source of dissemination of
infection.
It will be noted in the returns presented in table X that the

WITWATERSRAND: SILICOSIS STATISTICS

647

prevalence of simple tuberculosis fell steadily from 0.58 per cent.
in 1916-1917 to 0.25 per cent, in 1924-1925. During that period,
the general working conditions on the mines and the medical
system of detection of cases remained substantially unaltered.
The Miners' Phthisis Act of 1925, however, provided that the
medical service for mine natives should thereafter be a whole-time
service, and introduced further provisions to improve the methods
of detection employed. It will be noted that the number of cases
of all three of the conditions specified in the table underwent
thereafter a simultaneous increase. It is reasonable to assume
that much of this increase has been due to the improved system
of detection employed from 1924-1925 onwards. Sufficient time
has not however elapsed to determine whether the increase which
has been observed since that date will prove to be temporary
only, or will be found to be permanent.

REVIEW OF THE DEVELOPMENT
OF SILICOSIS LEGISLATION I N S O U T H
AFRICA, WITH PARTICULAR REFERENCE
TO C O M P E N S A T I O N
A. B. DU TOIT, B.A., CHAIRMAN, MINERS' PHTHISIS BOARD;
GEORGE E. BARRY, M.A. (OXON), LEGAL ADVISER, TRANSVAAL

CHAMBER OF MINES, AND MEMBER, MINERS' PHTHISIS BOARD;
AND

NORMAN P. DALE, SECRETARY, MINERS' PHTHISIS BOARD

It had long been known that miners engaged in metalliferous mining
in hard rock were prone to suffer, to a greater extent than did the general
population, from chronic disease of the lungs or respiratory organs.
This excessive incidence of lung disease is not a feature peculiar to
the mines in the Transvaal and has been the subject of serious attention
and of official investigation in almost every important mining area,
especially since the introduction, many years ago, of rockdrills into
mining practice.
In the Transvaal the excessively high mortality from miners' phthisis
which had occurred, especially amongst rockdrill miners, during and
just after the Anglo-Boer War arrested the attention of the Government
and the mining community; and in 1902 a Commission was appointed
to enquire into the extent to which the disease prevailed, to ascertain
its causes and to recommend preventive and curative measures. Since
then the subject of miners' phthisis has continuously occupied serious
attention; the nature, prevalence, causation and prevention of the
disease ; the benefits to be granted to persons suffering from the disease
and their dependants, and other matters incidental thereto, have been
investigated and reported upon by numerous Parliamentary Select
Committees and Commissions (judicial, medical and otherwise) and many
important papers bearing upon the disease have been contributed to
scientific societies, all of which have done much to elucidate the many
problems connected with the subject.
The earlier investigations and enquiries showed that preventive
measures had become an urgent necessity, and since then steps have
been taken, from time to time, by the Government in South Africa
and the mining industry to secure the better regulation of mining
work, to introduce methods to prevent the generation and dissemination
of dust in the mines, to improve the ventilation of the mines and to
protect the health and safety of persons working in the mines; and an
enormous advance has been made in this connection.
Four Commissions, in addition to the Commission of 1902 mentioned
above, have been appointed to investigate the subject of Miners' Phthisis
and other matters incidental thereto, namely:

SILICOSIS LEGISLATION IN SOUTH AFRICA

649

(i)

The Miners' Phthisis Medical Commission appointed under the
Miners' Phthisis Allowances Act, No. 34 of 1911, to enquire into
the prevalence of miners' phthisis and pulmonary tuberculosis
on mines within the Union of South Africa. This Commission,
which consisted of seven medical practitioners, reported on
2 February 1912.
(ii) Commission to enquire into the working of the Miners' Phthisis
Acts. This Commission reported on 7 December 1918.
(iii) Commission, with a Judge as Chairman, to enquire into the
working of the Miners' Phthisis Act, No. 40 of 1919. This
Commission reported on 16 April 1921.
(iv) Commission to enquire into the working and administration of
the Miners' Phthisis Acts, Consolidation Act, No. 35 of 1925t
which is at present in force. This Commission is at presen
carrying out its investigations.
Ten Select Committees on Miners' Phthisis have been appointed by
Parliament and these Committees reported on 23 May 1912; June 1914;
20 April 1916; 12 June 1917; 22 April 1918; 30 May 1919; 20 July 1920;
9 April 1924; 14 July 1925, and 25 March 1929.
Nine Acts, dealing with Compensation for persons found to be suffering
from miners1 phthisis (silicosis) and their dependants and other matters
incidental thereto, have been passed by the Parliament of the Union of
South Africa; namely:
(a) Miners' Phthisis Allowances Act, No. 34 of 1911.
(b) Miners' Phthisis Act, No. 19 of 1912.
(c) Miners' Phthisis Act, Amendment Act, No. 29
of 1914.
(d) Miners' Phthisis Act, No. 44 of 1916.
I Called the
(e) Miners' Phthisis Act, Amendment Act, No. 44
" prior Law "
of 1917.
(/) Miners' Phthisis Acts, Further Amendment
Act, No. 24 of 1918.
(g) Miners' Phthisis Act, No. 40 of 1919 (called the "'principal Act ")
(ft) Miners' Phthisis Act, Amendment Act, No. 35 of 1924 (called the
" previous Act ").
(/') Miners' Phthisis Acts, Consolidation Act, No. 35 of 1925 (the
" present Act ").
(Note. — Only the Acts of 1912, 1914, 1916, 1917 and 1918 are
included in the term " prior Law ".)
The Miners' Phthisis Allowances Act, No. 34 of 1911 (which is not
included in the prior Law), came into force on 12 May 1911, and was
superseded by the Miners' Phthisis Act, No. 19 of 1912, which came into
force on 1 August 1912, and was amended by the Miners' Phthisis Act,
Amendment Act, No. 29 of 1914, which came into force on 1 August 1914.
The Miners' Phthisis Act, No. 44 of 1916, came into force on 1 August
1916, repeals the Miners' Phthisis Acts of 1912 and 1914 (with the
exception of certain sections thereof), was amended by the Miners'
Phthisis Act, Amendment Act, No. 44 of 1917, which came into force
on 1 August 1917, and was further amended by the Miners' Phthisis Acts,
Further Amendment Act, No. 24 of 1918, which came into force on
22 May 1918. . The Miners' Phthisis Act, No. 40 of 1919 (the principal
Act), came into force on 1 August 1919, repeals the Miners' Phthisis Act

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of 1911, the unrepealed sections of the Miners' Phthisis Acts of 1912 and
1914 and the Miners' Phthisis Acts of 1916, 1917, and 1918 and was
amended by the Miners' Phthisis Act, Amendment Act, No. 35 of 1924
(the previous Act), which came into force on 1 August 1925. The
Miners' Phthisis Acts, Consolidation Act, No. 35 of 1925, the present
Act, came into operation on 1 August 1925, and repeals the Miners'
Phthisis Act, No. 40 of 1919 (the principal Act), and the Miners' Phthisis
Act, Amendment Act, No. 35 of 1924 (the previous Act). It consolidates
and amends the laws relating to miners' phthisis and is at present in
force.
The making of awards and payments of compensation to miners'
phthisis sufferers and their dependants is placed under a Board styled
the " Miners' Phthisis Board ", consisting of a Chairman and not less
than three or six other members who are appointed by the Government.
This Board has power to collect, by means of levies on the mines enumerated in the scheduled list published under the Miners' Phthisis Act, the
necessary funds for the payment of compensation and for carrying out
the other functions of the Board.
Since 1 August 1916 all medical matters and the certification of claims
for compensation were placed under a body of medical practitioners
styled the " Miners' Phthisis Medical Bureau ", consisting of a Chairman
and a number of medical practitioners appointed by the Government.
On 1 August 1925 a special Medical Appeal Board, consisting of a
Chairman and two medical practitioners having special knowledge of
diseases of the lungs and respiratory organs, was appointed by the
Government. The function of the Appeal Board is to deal with appeals
by persons who are dissatisfied with the decisions of the Medical Bureau.
SUMMARY OF COMPENSATION PROVIDED UNDER THE
M I N E R S ' PHTHISIS ACTS

The following is a summary of the main provisions under which
benefits were granted in terms of the above-mentioned Miners'
Phthisis Acts and the various regulations published under those
enactments. Unless an express statement to the contrary is made,
the Board was not precluded from granting benefits to miners and
dependants who were not resident in the Union of South Africa.
Miners' Phthisis Allowances Act, No. 34 of 1911
Allowances under this Act could be granted, in the absolute
discretion of the Board, to persons (and their dependants) who
were or had been employed in the scheduled mines (certain gold
mines in the Transvaal) and were wholly or partially incapacitated
by miners' phthisis (silicosis) from pursuing their avocations or
were suspended on account of such disease by any rule or
regulation in t h a t connection.
To all intents and purposes, the benefits under the Act were
ex-gratia grants pending the introduction of miners' phthisis

SILICOSIS LEGISLATION IN SOUTH AFRICA

651

legislation of a more comprehensive nature and any payments
made thereunder were to be deducted from the benefit to be
granted under any subsequent Miners' Phthisis Act. In cases
where further benefits were so granted, the awards have been
treated as original awards under such subsequent Act, the beneficiary being deemed to be a non-beneficiary for the purposes of
granting further benefits thereunder.
The funds under the control of that Board were limited and
in a number of cases benefits were refused, the applicant being
advised to re-apply at a later date. No benefits were provided
for the dependants of a deceased miner unless the miner had
been granted benefits under the Act. The provisions of the Act
and the Regulations thereunder precluded the Board from granting
benefits to miners not resident in the Union of South Africa.
Applicant miners were medically examined by the Miners'
Phthisis Medical Commission established under the Act to investigate and report upon the extent to which miners' phthisis was
prevalent amongst persons employed upon the scheduled mines
and awards were made on the certificates of that body.
The amount of the benefit in each case was limited to £250,
but, except in a few cases in which single sums of £100 to £250
were granted or in which the applicant and his wife and children
were repatriated and granted small monthly payments for a few
months, the award made was usually £15 to £20 payable immediately, to enable the applicant to discharge his debts, and £8 15s.
per mensem for a few months; in many cases the monthly
payments were prolonged until the next Miners' Phthisis Act
(No. 19 of 1912) came into operation on 1 August 1912.
Miners' Phthisis Act, No. 19 of 1912
Under this Act a miner in the earlier (primary) stage of miners'
phthisis (silicosis) became entitled to £8 per mensem for a period
not exceeding twelve months and in the later (secondary) stage
not exceeding £400 (lump sums being in each case payable at
the discretion of the Board for debts, repatriation, farming,
business, etc.). A miner granted £96 and thereafter found to be
in the later stage, became entitled to an amount not exceeding
£304 (£400 less £96).
The miner had, however, first to satisfy the Board that he had
been employed underground on the scheduled mines during the
four years immediately preceding the date of this claim, and if

652

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CONFERENCE

he had been so employed for a period or periods amounting to
less than two years during such four years he had also to satisfy
the Board that he had contracted miners' phthisis on the scheduled
mines.
Applicant miners were medically examined by two (or in special
cases three) medical advisers to the Board, the Mines Medical
Inspector and a number of medical practitioners being appointed
by regulation as medical advisers. Applicant miners resident
outside the Union of South Africa were examined and reported
upon by medical practitioners registered as such in the country
where the applicant resided, and the medical advisers granted
certificates after considering such reports. Awards were made in
accordance with the decisions of the medical advisers.
Dependants (wholly or partially dependent) of a deceased
beneficiary miner became entitled to an amount of £400 (less the
amount paid to the miner), payable in instalments, provided the
Board was satisfied that the miner died of miners' phthisis, and
dependants of a deceased non-beneficiary miner became entitled
to £400 (payable in instalments) provided the Board was satisfied
that the miner had died of miners' phthisis and was qualified to
receive an award under the Act, viz. if the miner had died prior
to the commencement of the Act (1 August 1912), the period of
four years mentioned above, during which the Board had to be
satisfied that the deceased had been a miner on scheduled mines,
was the four years immediately preceding the commencement of
the Act (1 August 1912), but if he died after the commencement
of the Act the said period was the four years immediately
preceding the date of the application by the dependants.
The Board could, in its discretion, contribute (in addition to
any benefits which could be granted to dependants) an amount
not exceeding £20 towards the reasonable expenses of medical
attendance and burial of a miner who died from miners' phthisis,
while a beneficiary under the Act or while his claim to any
benefit thereunder was being investigated.
A miner was defined by the Act as a person of European
descent who, before or after the commencement of the Act, performed or had performed as his regular occupation any class of
work underground (i.e. below the surface) on a scheduled mine
(excluding managers and managing directors).
A native (i.e. any member of the aboriginal races or tribes of
Africa) who had been employed underground as a native labourer
on the scheduled mines became entitled to an amount not exceeding

SILICOSIS LEGISLATION IN SOUTH AFRICA

653

£20 (to be assessed by the Director of Native Labour) if found by
the medical advisers to have had miners' phthisis in the earlier
(primary stage), and to an amount not exceeding £50 (to be
assessed as aforesaid) in the later (secondary) stage. In the event
of the death of such a native who had not been granted benefits, his
dependants became entitled to an amount of £10 if the Director
was satisfied that he had died from miners' phthisis and had a wife,
child, parent or other person dependent upon him.
Deductions amounting to 2% per cent, could be made by
the companies (which owned or worked the scheduled mines)
from the earnings of the miners employed by them, and the
companies were required to contribute to the funds of the Board
5 per cent, of such earnings during the two years ended 31 July 1914,
and thereafter iy2 per cent. Persons who were employed underground on the scheduled mines and who were neither Europeans
nor natives (i.e. coloured persons, Indians, Asiatics, etc.) could elect
that, for so long as they were so employed, the aforesaid deductions
should be made from their earnings by the mining companies.
Such a person, so electing, became entitled during the two years
ended 31 July 1914 to benefits, within the discretion of the Board,
not exceeding half those which could be granted to a miner, and
after 31 July 1914, to the benefits which could be granted to the
miner, according to the circumstances applicable to each case.
Failing such election, such a person became entitled to the benefits
prescribed by the Act for a native.
The Act of 1912 was amended by the next Miners' Phthisis Act
(No. 29 of 1914), which came into force on 1 August 1914.
Miners' Phthisis Act, Amendment Act, No. 29 of 1914
Under this Act the term " underground work " was extended to
include work " on or about the rock crushers in a crusher station "
and provision was made for a final decision by the Government
Mining Engineer as to whether any person was a " miner ". The
said official gave a general ruling that any person who spends, in
any month, more than half his working time underground or on or
about the rock crushers in a crusher station was to be deemed to be
a miner under the Act during that month.
The benefit to be granted to miners in the earlier stage of miners'
phthisis was increased by the Act to an amount not exceeding £200.
A miner who had been granted benefits (£96) under the 1912 Act,
or his dependants, could be granted, at the discretion of the Board,

654

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CONFERENCE

an amount not exceeding £100, provided the claimant was permanently resident in the Union of South Africa, was in need of
assistance and made application before 1 August 1915.
Dependants of a deceased miner who had died from any cause
became entitled to the balance of the award granted to the miner
before or after the commencement of the Act, provided the dependants applied within nine months from the date of his death.
Dependants of a beneficiary miner also became entitled to benefits
as provided by the 1912 Act for such cases, if pre-existent miners'
phthisis was the chief contributing factor in the causation of his
death, but, save as regards the dependants mentioned above, the
dependants of a deceased beneficiary or non-beneficiary miner
were required to make application within two years of the date of
death of the miner, failing which the benefit could not be granted.
Special provision was made for ex-gratia grants (not exceeding
£10,000 in all) to dependants of deceased non-beneficiary miners
who died of miners' phthisis prior to the commencement of the
1911 Act (12 May 1911), provided the dependants were permanently
resident in the Union of South Africa, were in need of assistance
and made application before 1 August 1915.
The Acts of 1912 and 1914 were repealed by the next Miners'
Phthisis Act (No. 44 of 1916), which came into force on 1 August
1916.
Miners' Phthisis Act, No. 44 of 1916
Under this Act, the benefits provided were :
An amount not exceeding £300 (in instalments) to a nonbeneficiary miner found, between 1 August 1916 and 1 August 1918,
to have primary silicosis; the unpaid balance to be granted in
instalments to his dependants, wholly or partially dependent, in
the event of his death. An amount of £400 (payable £10 per month
if married and £8 per month if unmarried) to a non-beneficiary
miner found, between 1 August 1916 and 1 August 1918, to have
secondary silicosis (the unpaid balance of £400 to be granted in
instalments to his dependants, in the event of his death), but if
the £400 had been paid to the miner, payments to him could be
continued until £750 had been paid, provided he was a permanent
resident in the Union of South Africa on and after 1 August 1916,
and was in need of financial assistance. An amount not exceeding
£375 (in instalments) to a miner found, after 1 August 1918 to have
silicosis (in either the primary or secondary stage) ; the unpaid
balance to be granted, in instalments, to his dependants, in the

SILICOSIS LEGISLATION IN SOUTH AFRICA

655

event of his death. An amount of £300 (in instalments) to a miner
found to have tuberculosis without silicosis, provided he was thereby
prevented, prior to 1 August 1917, from working underground on
scheduled mines and had been so employed after 1 May 1916; the
unpaid balance to be granted in instalments to his dependants, in
the event of his death. An amount not exceeding £750 (payable
£12 per month if married and £10 per month if unmarried) to a miner
found to have tuberculosis with silicosis provided he was thereby
prevented, prior to 1 August 1917, from working underground on
scheduled mines and had been so employed after 1 May 1916; the
unpaid balance to be granted in instalments to his dependants, in
the event of his death, if they were permanent residents in the
Union of South Africa on and after 1 August 1916.
The silicotic miner had, however, first to satisfy the Board that
he had been employed as a miner on scheduled mines after 1 August
1908, and, if he had been so employed for a period or periods
amounting to less than two years since that date, that he had
contracted silicosis on scheduled mines.
Dependants of a deceased miner whose claim was under investigation when he died became entitled to the. benefit (in instalments)
which he was then entitled to. Dependants of a non-beneficiary
miner (who had not lodged a claim with the Board, who had been
proved by post-mortem examination to have died from silicosis
or any other cause if silicosis was present as a contributing or
predisposing factor and who had qualified to receive a benefit
under the Act) became entitled to £300 (in instalments) if the miner
died between 1 August 1916 and 1 August 1918, and £375 (in
instalments) if the miner died after 1 August 1918.
A miner who had been granted benefits under the earlier Acts for
primary silicosis (£96, £196 or £200) became entitled, at the discretion of the Board, to a further amount not exceeding £100, provided
he was a permanent resident in the Union of South Africa on and
after 1 August 1916, was in need of financial assistance owing to
his suffering from silicosis and made application prior to 1 August
1917 (if such a miner was found to have secondary silicosis he became
entitled to the benefit—not exceeding £400—provided for such
cases under the earlier Acts less the amount paid to him for primary
silicosis); in the event of his death the balance to be granted, in
instalments, to his dependants. A miner who had been paid the
full amount of £400 under the earlier Acts for secondary silicosisbecame entitled to a further £350 (payable £10 per month if married
and £8 if unmarried), provided he was a permanent resident in the-

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Union of South Africa on and after 1 August 1916, and was in need
of financial assistance; in the event of his death the balance to be
granted in instalments to his dependants.
A miner who had been granted benefits for the primary stage and
thereafter was found to be in the secondary stage became entitled
to the secondary stage benefits, less the amount previously granted.
A miner who had silicosis but was not eligible for and had not
received a benefit under this or the earlier Acts could be awarded
an ex-gratia grant, and dependants of such a miner who had died
from silicosis or from a disease of which silicosis was a contributing
or predisposing factor could also be awarded an ex-gratia grant,
provided that, in both cases, the claimant was in need of financial
assistance, was a permanent resident in the Union of South Africa
on and after 1 August 1916 and applied before 1 August 1917;
the amount available for these grants being £20,000.
Applicant miners and native labourers were medically examined
by the Miners' Phthisis Medical Bureau which had been established
under the Act for this purpose, and benefits could only be granted,
under this Act, in accordance with the certificates of t h a t body.
The definitions of " miner " and of " underground work " in
this Act were the same as the definitions under the Act of 1912
as amended by the Act of 1914.
Provisions were made in this Act empowering the Board:
(i)

to acquire land to be devoted to small agricultural holdings and
to establish on such holdings beneficiary miners and other suitable
persons,
(ii) to assist financially, by means of loans or otherwise, in establishing or carrying on industrial undertakings which undertook to
employ or were employing, at the Board's request, beneficiaries
or dependants of beneficiaries,
(iii) to open and conduct a bureau, or co-operate with other labour
bureaux and other institutions, for obtaining employment for
beneficiaries or dependants of beneficiaries, and
(iv) to assist financially in defraying the expenses of transport of
beneficiaries to places where employment for them had been
obtained.
The provisions of Act No. 19 of 1912 regarding the following
were re-enacted:
(i)

contributions by the Board towards the funeral and medical
expenses of deceased miners,
(ii) benefits for miners' phthisis (silicosis) to natives and their
dependants, and
(iii) election by persons, other than miners or natives, to have deductions made by the mining companies from their earnings and the
benefits to be granted to such persons.

SILICOSIS LEGISLATION IN SOUTH AFRICA

657

A native labourer who had been employed underground on the
scheduled mines and who was discharged from such employment
after 1 August 1916 and prior to 1 August 1917, on the ground
that he had tuberculosis, became entitled to the benefits provided
in the Act for a native labourer for primary silicosis, if the
tußerculosis was not complicated by silicosis, or to the benefits
provided for secondary silicosis, if the tuberculosis was complicated
by silicosis.
The Act of 1916 was • amended by the next Miners' Phthisis
Act (No. 44 of 1917), which came into force on 1 August 1917.
Miners'1 Phthisis Act, Amendment Act, No. 44 of 1917
Under this Act the amounts to be granted to miners and
dependants were fixed at £300, £375, or £750 (as the case may be)
instead of " an amount not exceeding such sum " ; the amount for
secondary silicosis was increased from £400 to £750 (i.e. miner
—non-beneficiary under the Miners' Phthisis Acts of 1912 and
1914—need not necessarily be " resident " to qualify for the
additional £350, and the unpaid balance of the £750 could be
granted to his dependants, in the event of his death). The date
" 1 August 1917 " in the Act of 1916 was extended to " 1 August
1918 ". Dependants of a deceased miner who had been granted
£750 for tuberculosis with silicosis need not necessarily be
" resident " to qualify for the unpaid balance of the amount
awarded to the miner. Benefits for tuberculosis with or without
silicosis to be granted only if such tuberculosis was found at the
periodical examination of a miner (compulsory medical examinations, by the Miners' Phthisis Medical Bureau, of working miners,
at intervals of six months). Further benefits (subject to " residence " and otherwise, as in the Act of 1916) to a miner who
had been granted an award under the Acts of 1912-1914 for
primary silicosis, namely, £300 (less previous benefits of £96, £196,
£200 or £296, as the case may be) if found to have primary
silicosis, tuberculosis without silicosis or to be unfit for underground work by reason of silicosis though not primary or secondary,
and £750 (less previous benefits), if found to have secondary
silicosis. Further benefits (subject to " residence " and otherwise,
as in the Act of 1916), to a miner who had been granted an
award under the Acts of 1912-1914 for secondary silicosis (not
necessarily the full amount of £400), namely, £500 (less the
previous benefit) if found to have primary silicosis or to be unfit
42

658

PAPERS PRESENTED TO THE CONFERENCE

for underground work by silicosis, though not in either the
primary or secondary stage, and £750 (less the previous benefit),
if found to have secondary silicosis or tuberculosis with or without
silicosis. Ex-gratia grants, provided for miners and dependants
by the Act of 1916, could also be awarded (on the same terms
and conditions as to " residence " and otherwise, as in the Act
of 1916) to dependants of beneficiaries who died prior to 1 August
1916.
Provisions were made in this Act empowering the Board:
(i) to assist, by means of loans, beneficiaries who are already established in business or in farming operations, and
(ii) to contribute amounts not exceeding half the cost of establishing
and maintaining a sanatorium for purely silicotic patients.
The Acts of 1916-1917 were amended by the next Miners' Phthisis
Act (No. 24 of 1918), which came into force on 22 May 1918.
Miners' Phthisis Acts, Further Amendment Act, No. 24 of 1918
Under this Act the date " 1 August 1918 " in the Act of 1916
(before and after amendment by the Act of 1917) was extended
to " 1 August 1919 ". The ex-gratia grants, previously mentioned,
could also be awarded (on the same terms and conditions as before) ;
to dependants of deceased beneficiaries who had not received further
awards under the Acts of 1916 or 1917 (instead of dependants of
beneficiaries who had died before 1 August 1916) and a further
amount of £40,000 was available for the ex-gratia grants provided
by the Acts of 1916 and 1917 and this Act.
The Acts of 1916, 1917 and 1918 were repealed by the next
Miners' Phthisis Act (No. 40 of 1919) which came into force on
1 August 1919.
Miners'' Phthisis Act, No. 40 of 1919 (the Principal Act)
Under this Act a miner (non-beneficiary under the prior Law)
became entitled to a one-sum benefit, for the ante-primary or
primary stage of silicosis or tuberculosis without silicosis (calculated
on his month's earnings) as is provided in the present Act (No. 35
of 1925) (vide paragraph (/) hereof) and such a miner became
entitled to an award of a monthly allowance (pension) for secondary
silicosis or tuberculosis with silicosis (calculated on his month's
earnings) as is provided in the present Act (No. 35 of 1925) (vide
paragraph (/) hereof) except that the tuberculosis whether with or

SILICOSIS LEGISLATION IN SOUTH AFRICA

659

without silicosis was to be found at a periodical examination
(compulsory medical examinations, by the Miners' Phthisis Medical
Bureau, of working miners), that the silicotic miner had first to
satisfy the Board that he had been employed underground on
scheduled mines for at least two years since 1 August 1908, or that
he had contracted silicosis on such a mine and that additional
allowances could not be granted to a miner for more than three
of his children, for his invalid children who were over sixteen
years of age when the miner became entitled to the allowance or
for his stepchildren (unless they had been " adopted " before the
grant of any benefit to him).
The conditions, attached to awards of monthly allowances
(pensions) to miners and dependants under the Act of 1919, were
similar to the conditions attached to such awards under the present
Act (vide paragraph (/') hereof).
A miner who had been granted a one-sum benefit for ante-primary
silicosis could become entitled to a further one-sum benefit for
primary silicosis or tuberculosis without silicosis and a miner who
had been granted a one-sum benefit could become entitled to a
further award of a monthly allowance for secondary silicosis, but
in both cases only if he had applied for benefits within the prescribed
period of three months from the date on which he had been first
notified after 1 August 1919, that he had silicosis (in unsuccessful
appeals the period was one month from the date he was notified
of the result of the appeal).
Dependants of a deceased beneficiary miner (non-beneficiary
under the prior Law) became entitled to the balance of the award
made to the miner, but if the miner was in receipt of a monthly
allowance or had died from secondary silicosis or any other cause
if secondary silicosis was present as a contributing or predisposing
factor, the dependants became entitled to an award of a monthly
allowance. Dependants of a deceased non-beneficiary miner
became entitled to such benefit (for ante-primary or primary
silicosis) as the miner would have been entitled to, had he not died,
but, if secondary silicosis was the cause of his death or was present
as a contributing or predisposing factor in the causation of his
death, the dependants became entitled to an award of a monthly
allowance. Dependants of a deceased beneficiary miner to or in
respect to whom benefits had been granted under the prior Law
became entitled to awards of monthly allowances, if the miner
died prior to 1 August 1919, but, if the miner died after that date,
only if silicosis was present as a contributing or predisposing factor

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in the causation of his death ; these dependants had to apply before
1 August 1920, and had to be resident in Africa (south of the
Equator) on and after 31 July 1916, or the date of the miner's
death (whichever was the later). Dependants of a non-beneficiary
miner who had died between 31 July 1916 and 1 August 1919, and
had qualified to receive benefits under the prior Law, became
entitled to an award of a monthly allowance on the terms and
conditions precedent to the grant of such an award to the dependants
of a prior Law beneficiary miner who had died after 1 August 1919.
Dependants (other than the widow and a child under sixteen)
could not be granted an award of a monthly allowance unless they
were wholly dependent upon the deceased miner; the widow of a
miner could not be granted an award of a monthly allowance if
she had re-married ; and an allowance could not be granted for more
than three children of a deceased miner.
A miner who had been granted benefits under the prior Law on
the grounds of silicosis and had secondary silicosis or tuberculosis
with silicosis became entitled to an award of a monthly allowance,
provided he was resident in the Union of South Africa on and after
31 July 1916. A miner who had been refused the additional award
under the Acts of 1916, 1917 and 1918, owing to his not having
been resident in the Union of South Africa, as required by that
enactment, became entitled to that additional award if he returned
to South Africa before 1 June 1919 and was in necessitous circumstances.
Awards to miners, native labourers and dependants could only
be granted on certificates of the Miners' Phthisis Medical Bureau
which had been established under the Act of 1916.
The Board could, in its discretion, contribute in addition to any
benefit which could be granted to dependants an amount not
exceeding £25 towards the reasonable expenses of burial and of
medical attendance during the last illness of a deceased miner who
had been a beneficiary under this Act or the prior Law or who, in
the opinion of the Bureau, died from silicosis or from any other
cause if silicosis was present as a contributing or predisposing factor.
A miner was defined as any person (other than a native labourer
and therefore included a non-European, such as a coloured person,
Indian, Asiatic, etc.) who was employed underground on the
scheduled mines in any of the forty-five occupations specified in the
Act, or any other occupation which necessitated the incumbent
spending 100 or more working hours per month underground.
" Underground work " comprised work beneath the surface of a

SILICOSIS LEGISLATION IN SOUTH AFRICA

661

mine, upon or about rock crushers in a crusher station and in a
sample crushing room or assay office. Underground work on a
gazetted mine was deemed, for the purposes of granting benefits,
to be underground work on a scheduled mine.
The provisions of Act No. 44 of 1916 and Act No. 44 of 1917
regarding the following were re-enacted:
(i)
(ii)
(iii)
(iv)
(v)
(vi)

land settlement,
loans to industrial undertakings,
employment bureaux,
transport expenses of beneficiaries,
loans to beneficiaries, and
contributions for silicotic sanatorium.

Provisions were made in this Act empowering the Board,
(i) to provide for the training in trades and industries of beneficiaries,.
and
(ii) to establish co-operative workshops for beneficiaries.
The provisions of the Act of 1912 regarding deductions from
the earnings of miners for the purposes of the Board's funds,
which provisions had remained in force under the Acts of 1916,
1917 and 1918 were not re-enacted in this Act of 1919 (or any
subsequent Act).
An inspector of mines (employed underground in connection
with the scheduled mines) who retired from the public service
before attaining the age of retirement prescribed under the pension
statute applicable to him, and whose retirement was due to the
fact that he had contracted silicosis, became entitled either:
(i) to one year's salary which he had been in receipt of at the date
of his retirement, in addition to the pension payable to him under
such pension statute, or
(ii) to have five years added to his period of pensionable employment
for the purpose of calculating his pension on such retirement.
In the event of such an inspector having died, from silicosis
or from any other cause if silicosis was present as a contributing
or predisposing factor, before attaining the age of retirement, as
mentioned above, or within five years after retirement in the aforesaid circumstances, his dependants became entitled to an amount
representing one year's salary which he was in receipt of at the
date of his death, in addition to any other benefits allowed to
them by the pension statute in the event of his death while in
the public service.

662

PAPERS PRESENTED TO THE CONFERENCE

A native labourer who had been employed underground on
scheduled mines after 31 July 1912, and who had not been granted
benefits under this Act or the prior Law became entitled to
benefits—
(i) for silicosis in the ante-primary stage: twelve times his month's
earnings (as defined in the present Act (vide paragraph (/) hereof),
(ii) for silicosis in the primary stage or tuberculosis without silicosis:
eighteen times his month's earnings, and
(iii) for secondary silicosis or tuberculosis with silicosis: twenty-four
times his month's earnings.
In cases of tuberculosis with or without silicosis, he must
however have been so found at a " final " examination (compulsory
medical examination, by the Miners' Phthisis Medical Bureau, of
a native labourer when leaving his employment permanently or
otherwise, after having been employed underground on a scheduled
mine for a period exceeding one month).
In the event of the death of a native labourer who had not
been granted benefits under this Act or the prior Law and who
had died from silicosis or from any other cause if silicosis was
present as a contributory or predisposing factor, his dependants
became entitled to such benefits as the native labourer would
have been entitled to had he not died.
The Act of 1919 was amended by the next Miners' Phthisis
Act (No. 35 of 1924) which came into force on 1 August 1924.
Miners' Phthisis Act, Amendment Act, No. 35 of 1924
(the Precious Act)
Under this Act the miner or his dependants became entitled
to the additional benefits as if the miner had applied within the
prescribed period, provided he had ceased underground work on
scheduled mines within three months after the first notification
that he had silicosis.
A prior Law beneficiary miner or his dependants became entitled
to benefits, as if such prior Law benefit had not been made,
provided the miner had lawfully worked underground on scheduled
mines after the grant of such prior Law benefits.
Awards made from the Consolidated Revenue Fund (Special
Grants) to dependants of a prior Law beneficiary miner who had
died too late to enable them to apply before 1 August 1920 were
deemed to be awards lawfully made under the Act.
The date before which the dependants of a prior Law beneficiary

SILICOSIS LEGISLATION IN SOUTH AFRICA

663

miner (who died after 1 August 1919) had to apply for an award
of a monthly allowance was extended to twelve months from the
date of the miner's death, and, if the miner was in receipt of or
entitled to an award of a monthly allowance, silicosis need not,
necessarily, have been a contributing or predisposing factor in
the causation of his death.
Widows in receipt of monthly allowances became entitled to
a one-sum payment (twenty-four times such allowance) on
remarriage.
A South African widow who had left South Africa with her
husband (a prior Law beneficiary miner), and was therefore not
entitled to an award of a monthly allowance, became entitled to
such an award, as if she had been resident in South Africa at
the date of his death, provided she had returned to South Africa
within two years of the said date.
Additional allowances could be granted to and in respect to
children (under sixteen years of age) in excess of three in number.
The Acts of 1919 and 1924 were repealed by the present Act
(No. 35 of 1925) which came into force on 1 August 1925.
Miners'' Phthisis Acts, Consolidation Act, No. 35 of 1925
(the Present Act)
Under this Act benefits are granted by the Board to miners
and dependants of deceased miners: (1) who had contracted
silicosis during or in consequence of underground employment on
scheduled mines or a mine at any time on the list of scheduled
mines or on gazetted mines, or (2) who were found to have
tuberculosis without silicosis within twelve months of their having
ceased such underground work and had been employed on such
underground work for a period or periods amounting to at least
two years.
Dependants are such members of a deceased person's family
as were dependent upon him for maintenance and had not contracted a marriage since the date of his death, namely, his widow
and children under sixteen years of age (including illegitimate
children born before the date of the Bureau's certificate that he
had secondary silicosis or tuberculosis with silicosis), failing
whom, his other relatives by consanguinity or affinity in a
certain order of preference.
Awards to miners, native labourers and dependants can be
granted only on certificates from the Miners' Phthisis Medical

664

PAPERS PRESENTED TO THE CONFERENCE

Bureau (established under the Act for medical purposes) that
such miners or native labourers have silicosis or tuberculosis or
both those diseases and awards to dependants of a deceased
miner or native labourer can be granted only on certificates from
the said Bureau either that the deceased had silicosis or tuberculosis or both or that he had died from silicosis or from any
other cause with which silicosis was present as a contributing or
predisposing factor.
A miner or the dependants (of a deceased miner), dissatisfied
with the decision of the said Bureau, may appeal in the prescribed
manner from that decision to the Medical Board of Appeal, and
certain special cases of miners who went on active service and
who had been refused benefits under the Miners' Phthisis Acts
and also under the War Special Pensions Act, No. 42 of 1919,
can be dealt with by the Joint Medical Board. Under such circumstances the certificate of the Medical Board of Appeal or the
Joint Medical Board (as the case may be) is deemed to be the
certificate of the Bureau for the purposes of the Act.
Awards are calculated on the month's earnings of the miner
or native labourer being one-sixth part of the amount earned by
him for the 156 days he worked, as such, last prior to the date
he was first certified by the said Bureau to have developed silicosis
or tuberculosis to a degree entitling him to benefits under the
Act. A return of earnings for the number of days mentioned is
usually obtained from the mining company or companies concerned
but, if the amount of the earnings cannot be so ascertained, the
month's earnings of the miner or native labourer is to be determined
by the Board or the Director of Native Labour (as the case may
be). The month's earnings of a miner to or in respect to whom
benefits have been granted under the prior Law is deemed to be
£30. In cases where original awards are made after 1 August 1925,
fractions of £1 in the month's earnings of a miner are reckoned as £1
if the fraction is 10s. òr more and are disregarded if less than 10s.
A miner who has been granted benefits under the prior Law and
who has lawfully worked underground on scheduled mines after
the grant of such benefits is deemed to be a miner who has not
been granted benefits under the prior Law.
ONE-SUM AWARDS

A non-beneficiary miner who has silicosis in the ante-primary or
primary stage or tuberculosis without silicosis is entitled to an award

SILICOSIS LEGISLATION IN SOUTH AFRICA

665

payable in one sum. The award to a miner who has silicosis in
the ante-primary stage is calculated as follows:
Twelve times that part of his month's earnings which does not exceed
£29 3s. 4d.
Six times that part which exceeds £29 3s. 4d., but does not exceed
£37 10s.
Three times that part which exceeds £37 10s.
The amount of the award for silicosis in the primary stage is
that payable for the ante-primary stage with an addition of 50
per cent, and the amount of the award for tuberculosis without
silicosis is the same as that for the primary stage of silicosis. A
miner who has been granted a one-sum award for ante-primary
silicosis becomes entitled to a further one-sum award, 50 per cent.
of such previous award, for primary silicosis or tuberculosis
without silicosis, provided he had applied for benefits or ceased
underground work on scheduled mines within three months of the
date he was first notified after 1 August 1919 that he had silicosis.
One-sum awards could not be granted under the Acts in force
prior to the commencement of the principal Act (1 August 1919),
and the averages of the one-sum awards made, since that date, are :
£401 for ante-primary silicosis, without tuberculosis,
£581 for primary silicosis without tuberculosis, and
£534 for tuberculosis without silicosis; the maxima being £803, £1,216
and £805 respectively.
AWARDS PAYABLE

IN MONTHLY

INSTALMENTS

A miner who had been refused the additional benefits under the
Acts of 1916, 1917 and 1918, owing to his not having been resident
in South Africa as required by that enactment, becomes entitled
to that additional award if he returned to South Africa before
1 July 1924.
A miner who has been granted benefits under the prior Law and
who has silicosis in the ante-primary or primary stage or tuberculosis
without silicosis is entitled to an award, in such instalments as the
Board may decide, calculated, as mentioned above, on his month's
earnings (viz. £30), but the amount of the prior Law benefit must
be deducted from the amount so arrived at. (An amount of
£355 represents the award, for ante-primary silicosis, calculated
on month's earnings of £30, and an amount of £532 10s. represents
such an award for primary silicosis or tuberculosis without silicosis.)
A miner who has been granted benefits under the prior Law and who

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PAPERS PRESENTED TO THE CONFERENCE

has silicosis in the secondary stage or tuberculosis with silicosis is
entitled to an award, in such instalments as the Board may decide,
of £750 less the amount of such prior Law benefits, unless such miner
is entitled to an award of a monthly allowance, as mentioned below.
The dependants of a deceased miner are entitled to the award,
in such instalments as the Board may decide for the ante-primary,
primary or secondary stage of silicosis, or tuberculosis with or
without silicosis if the miner was, at the time of his death, entitled
to such an award, unless the dependants are entitled to an award
of a monthly allowance, as mentioned below.
AWARDS OF MONTHLY ALLOWANCES (PENSIONS)

A non-beneficiary miner who has silicosis in the secondary stage
or tuberculosis with silicosis is entitled to an award of a monthly
allowance.
A miner who has been granted a one-sum award becomes entitled
to a further award of a monthly allowance for secondary silicosis or
tuberculosis with silicosis, provided he had applied for benefits or
ceased underground work on scheduled mines within three months
of the date he was first notified after 1 August 1929 that he had
silicosis.
A miner who has been granted benefits under the prior Law and
who has silicosis in the secondary stage or tuberculosis with
silicosis is entitled to an award of a monthly allowance, provided
he was resident in South Africa on and after 31 July 1916 or the
date on which he was first granted any benefits (whichever is the
later).

The dependants of a miner who died after 1 August 1919, and
to or in respect to whom benefits had not been granted under the
prior Law, are entitled to an award of a monthly allowance: (1) if
the deceased miner was in receipt of or entitled to such an award,
or (2) if the Bureau certifies before or after his death that he had
silicosis in the secondary stage or tuberculosis with silicosis or
certifies that he died from silicosis or from any other cause with
which silicosis was present as a contributing or predisposing factor.
Under the principal Act, an award of a monthly allowance could
not be granted to the dependants of a deceased non-beneficiary
miner who had died from silicosis or from a cause with which
silicosis was present as a contributing or predisposing factor unless
the deceased miner had silicosis in the secondary stage at the time
of his death. In the other cases in which silicosis (though not

SILICOSIS LEGISLATION IN SOUTH AFRICA

667

in the secondary stage) was a factor in causation of death of the
miner, the dependants became entitled to the award, payable in
such instalments as the Board may decide, which the miner, had he
not died, would have been entitled to for silicosis in the ante-primary
or primary stage (as the case may be). The present Act
provides that in such a case the award; if granted to the widow and
children (under sixteen years of age) of a deceased miner, can be
converted into an award of a monthly allowance on certain conditions.
The dependants of a deceased miner to or in respect to whom
benefits had been granted under the prior Law are entitled to an
award of a monthly allowance: (1) if the deceased miner was in
receipt of or entitled to such an award, or (2) if the dependants were
resident in South Africa on and after 1 July 1916 or the date of the
miner's death (whichever is the later), and the Bureau certifies that
the miner died from silicosis or from any other cause with which
silicosis was present as a contributing or predisposing factor.
The dependants of certain deceased non-beneficiary miners were
refused ex-gratia grants under section 11 (b) of the Miners' Phthisis
Act, No. 44 of 1916, on the grounds that they were not in necessitous
circumstances, as required by that section. Provision is made in
the present Act for awards of monthly allowances to be granted to
the dependants in such cases, as if such prior Law awards had been
made.
A South African widow and the children (under sixteen years
of age) of a deceased miner who had left the Union of South Africa
with the miner and are, on that account, not entitled to an award
of a monthly allowance become entitled to such an award, as if
they were resident in the Union of South Africa at the time of his
death provided they have returned to the Union of South Africa
within two years of such date and have not since the date of such
return left the Union of South Africa for any purpose whatever.
CALCULATION OF MONTHLY ALLOWANCES

A monthly allowance granted to a miner is calculated as follows :
For the miner. — One-half of that part of his month's earnings which
does not exceed £20; one-quarter of that part which exceeds £20, but
does not exceed £28 6s. 8d., and one-twentieth of that part which
exceeds £28 6s. 8d.
For his wife. — If dependent upon him and if he was married to her
before 1 August 1919 or the date of the Bureau's certificate entitling him

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PAPERS PRESENTED TO THE CONFERENCE

to an award of a monthly allowance (whichever date is the later): onefifth of the total amount payable for the miner.
For each of his dependent children (legitimate and certain adopted and
stepchildren) not exceeding three in number, until such child attains the
age of sixteen years : one-tenth of the total amount payable for the miner.
For each such child in excess of three. — One-twentieth of such amount.
(i) The amount payable for a wife or child ceases upon the death of
such wife or child or on the marriage of such child.
(ii) An allowance is not payable to a miner for a wife or child of a
marriage contracted by the miner after 1 August 1919 or the date of the
Bureau's certificate entitling him to an award of a monthly allowance
(whichever date is the later).
(iii) An allowance is not payable to a miner for more than three
children for any period prior to 1 August 1924.
(iv) An allowance is not payable to a miner for his illegitimate
children.
(v) Subject to paragraph (ii) above, an allowance is payable to a
miner for a child born after the date of the Bureau's certificate entitling
him to an award of a monthly allowance.
(vi) An allowance is payable to a miner for an adopted child if
adopted before the date of the first certificate of the Bureau entitling him
to an award under the Act and if the child has been solely or mainly
dependent upon him since the date of adoption.
(vii) An allowance is payable to a miner for his dependent stepchildren if they are the legitimate children of his wife to whom he was
married before 1 August 1919, or the date of the Bureau's certificate
entitling him to an award of a monthly allowance (whichever date is the
later).
(viii) An allowance is payable to a miner for his child over the age
of sixteen years, if such child is, in the opinion of the Bureau, unable
to earn a living by reason of ill health or physical or mental incapacity,
and such an allowance can be continued for so long as, in the opinion
of the Board, it might reasonably have been expected that the miner
would have continued to contribute to the support of the child. (Such
a child is deemed, for the purposes of the Act, to be a child under sixteen
years of age.)
(ix) An allowance granted to a miner is payable from 1 August 1919
or from the date of the Bureau's certificate entitling him to such an award
or from the date the miner finally ceased underground work on scheduled
mines (whichever date is the latest), but if the miner was, for any reason,
not entitled to such an award under the principal Act or the previous
Act the allowance is not payable from a date prior to 1 August 1925.
A monthly allowance granted to the dependants of a deceased
miner is calculated as above, except t h a t :
(1) Widows and children (under sixteen years of age) are entitled to
double the allowance prescribed for the miner for his wife and children
(under sixteen years of age).
(2) Dependants wholly dependent, if the miner left no widow or child
under sixteen years of age, are entitled to the allowance which would have
been payable to the widow.

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669

(3) Dependants partly dependent if the miner left no dependants as
mentioned in (1) and (2) above, are entitled to an allowance equal to the
average monthly support accorded by the miner but not exceeding the
allowance which would have been payable to the widow.
(4) Children of a deceased miner include also:
(a) His unmarried illegitimate children if born before 1 August 1919,
or the date of the Bureau's certificate that he had silicosis in the
secondary stage or tuberculosis with silicosis (whichever date
is the later).
(b) His unmarried legitimate children of a marriage contracted
after the date of the Bureau's certificate entitling him to an
award of a monthly allowance.
(5) The allowance prescribed for the children mentioned in (4) above
(or any other dependant under sixteen years of age) is the same as that
prescribed for the legitimate children of the deceased miner.
(6) An allowance granted to the dependants of a deceased miner is
ayable from the date of death of the miner, but if the miner died before
August 1925, and the dependants were not entitled, for any reason,
to such an award under tne principal Act or the previous Act, the
allowance is payable from 1 August 1925.

A monthly allowance granted to a miner or dependant ceases in
the event of the death of such miner or dependant and the allowance
is reduced, accordingly, in the event of the death of any of the
dependants included in the award. An allowance granted to a
widow or dependant (other than a child under sixteen years of age)
ceases in the event of marriage, subject to the payment of twentyfour times the allowance payable for one month. An allowance
granted to a dependant (other than a widow or child under sixteen
years of age) is to be continued for so long as, in the opinion of the
Board, the deceased miner could reasonably have been expected to
continue to contribute to the support of the dependant.
The allowance granted to a beneficiary will cease and determine
when an amount of £750 has been paid, should the beneficiary have
been resident outside the Union of South Africa when the award
was made or should the beneficiary leave the Union of South Africa
permanently or without the written permission of the Board
granted for temporary purposes. In the case of a miner the amount
of £750 is calculated from the date of the award of a monthly
allowance ; in the case of a dependant from the date of the award
to the dependant, if the dependant was resident in the Union of
South Africa at the date of the miner's death but, if the dependant
was not so resident, from the date of the award of a monthly
allowance to the miner or the dependant (whichever is the earlier).
A beneficiary, in receipt of a monthly allowance, who desires to
leave South Africa for other than temporary purposes (i.e. per-

670

PAPERS PRESENTED TO THE CONFERENCE

manently) can be granted a passage by the Board to his or her
destination together with an amount for incidental expenses on the
journey.
Awards of monthly allowances could not be made under the Acts
in force prior to the commencement of the principal Act (1 August
1919) and the average amounts of the monthly allowance awards
made since that date are :
Miner: £17 19s. 7d. per mensem (for himself, his wife and two or three
children).
Widow of deceased miner: £4 18s. 4d. per mensem.
Children (not exceeding three and under sixteen years of age) of a
deceased miner: £2 9s. 3d. per mensem each.
Children (in excess of three and under sixteen years of age) : £1 4s. lOd.
per mensem each.
Other dependants : £4 Is. lOd. per mensem.
The amount of the maximum monthly allowance granted to a
miner (for himself) is £19 7s. 8d. ; the miner, being single, could not
be granted additional allowances for dependants; the award was
calculated on his month's earnings of £74 and he had previously
been granted a one-sum award of £1,216 for primary silicosis, being
the amount of the maximum one-sum award under the Act. The
amount of the maximum monthly allowances granted to a miner
(for himself and his dependants) is £28 Is. 3d., the miner having
been granted a monthly allowance for himself, his wife and eight
children. The amount of the maximum monthly allowance granted
to a widow (for herself) is £7 14s. 2d. and in the same case a monthly
allowance of £3 17s. Id. was granted to a child, the widow receiving
£11 lis. 3d. per mensem for herself and the child. The amount
of the maximum monthly allowance granted to the dependants of a
deceased miner is £2017s. 2d., allowances having been granted to the
widow and nine children. The largest number of children in respect
to whom additional allowances were granted to a miner is eleven,
the miner having been granted a monthly allowance of £23 l i s . 6d.
for himself, his wife and those eleven children. The largest number
of children of a deceased miner to whom a monthly allowance was
granted is nine (three cases), in one case the widow and those nine
children were granted a monthly allowance of £20 17s. 2d., as
mentioned above, and in the other two cases £20 13s. 6d. and
£19 17s. 2d.
Payments to the miners will, in many cases, continue for several
years and, on their demise, awards of monthly allowances will be
made to their dependants (mainly widows and children). Payments
in respect to children will, in almost all cases, continue until each

SILICOSIS LEGISLATION IN SOUTH AFRICA

671

child attains the age of sixteen years and it can be reasonably
anticipated that payments to the widows will continue, on an
average, for about twenty years and to the other dependants for
about ten years.
In numerous cases the beneficiaries (miners and dependants of
deceased miners) have been in receipt of monthly allowances since
the commencement of the principal Act (1 August 1919).
The Board may contribute (in addition to any benefit which can
be granted to dependants) an amount not exceeding £25 towards
the reasonable expenses of the burial of and medical attendance
during and incidental to the last illness of a deceased miner who
was a beneficiary under this Act, the previous Act, the principal
Act or the prior Law or who, in the opinion of the Miners' Phthisis
Medical Bureau, died from silicosis or any other cause if silicosis
was present as a contributing or predisposing factor.
A miner is defined as in the principal Act, and six occupations are
added to the forty-five occupations specified in t h a t Act. These
fifty-one occupations and any other occupation necessitating the
incumbent spending 100 or more hours per month underground
renders him a " miner " during the month in which he is so employed
and provision is made t h a t eleven occupations on the surface of a
mine (to which other such occupations can be added by Government
Notice) renders the incumbent a " miner " during each day he is
employed underground (if less than 100 hours per month). Two
such occupations have been added to the list by Government
Notice.
" Underground work ", as defined in the principal Act, is extended
to include also work in a change-house or on any tailings dump.
Provisions are made empowering the Board :
(i) to provide for the training in trades and industries of beneficiary
miners, their wives and children and beneficiary widows and children,
(ii) to conduct a bureau or to co-operate with other bureaux for the
purposes of obtaining employment for such persons as are mentioned in
(i) above,
(iii) to assist financially, by means of loans or otherwise, in establishing or carrying on any undertaking in which beneficiary dependants or
dependants of beneficiary miners are employed or will, at the Board's
request, be employed,
(iv) to assist financially in defraying the reasonable expenses
incidental to the transport of beneficiary miners, their wives and children
(under sixteen years of age) to places within the Union of South Africa
where employment for such miners has been obtained,
(v) to contribute an amount not exceeding half the cost of establishing and maintaining one or more sanatoria for purely silicotic patients,

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(vi) to establish or assist in establishing co-operative workshops for
such persons as are mentioned in (i) above, and
(vii) to condone the delay (due to certain circumstances arising out
of the 1914-1918 war) in cases where the making of an application or the
return to South Africa within a prescribed period is a condition precedent
to the grant of benefits under the Miners' Phthisis Acts.
The provisions of the principal Act and the prior Law regarding
land settlement and loans to beneficiaries established in business
or farming operations are not re-enacted in the present Act.
If an inspector (including an assistant inspector, deputy inspector,
or sub-inspector) of mines or an inspector of mining leases employed
in connection with the scheduled or gazetted mines contracts
silicosis or tuberculosis or both, he and his dependants are entitled
to benefits under the Act, as if he were a miner, in addition to the
pension or other benefit payable under any pensions statute
applicable to him.
The provisions of the principal Act regarding benefits, for silicosis
of tuberculosis or both, to native labourers and their dependants
are re-enacted in the present Act.

SUMMARY OF PROVISIONS TO MEET CLAIMS FOR COMPENSATION

The provision of compensation for claims by. sufferers and their
dependants, and the expenses of carrying out the various functions of the
Board, are provided out of a fund termed the Miners' Phthisis Compensation Fund, which is under the control of the Board.
For the purposes of this fund the Board has power to make quarterly
levies upon employers who own or work the scheduled mines (i.e. those
mines wherein the mineral dust is, in the opinion of the Minister of Mines,
of such a nature as to cause silicosis) to provide the amount which the
Board considers necessary for the purposes of the Compensation Fund
for the quarter.
(1)

Under the prior Law:
Compensation Fund. — Quarterly levies by Board of amount
actually required for payment of benefits. The amount levied to
be assessed in proportion to the average number of miners employed
per month by each employer during the period of three years
immediately preceding the quarterly levy. The Government
Mining Engineer to furnish the statement of average number of
miners.
Insurance Fund. — Every employer to make a contribution on
or before the tenth day of each month in respect of every person
•employed underground as a miner, or on or about rock crushers in a
•crusher station of a mine during the previous month. Such
contribution, from 1 August 1912 to 31 July 1914, to be 5 per cent.
of the earnings of each person so employed, the employer being
-empowered during this period, to recover from such employees one-

SILICOSIS LEGISLATION IN SOUTH AFRICA

673

half (50 per cent.) of the amount contributed to the Fund. From
1 August 1914 to 31 July 1919, the contribution by employers was
734 per cent, of such earnings, and in turn they were entitled to
recover one-third (33 Va per cent.) of the contributions to the Fund,
from the earnings of the particular employees.
(2) Under the Principal Act of 1919 the quarterly levy on each
employer was assessed as follows:
(a) 45 per cent, on the earnings of underground miners.
(b) 35 per cent, based on the silicosis rate of the mine.
(c) 20 per cent, based on the amount which the employer is assessed
for normal income tax during the last accounting period under the
Income Tax Act.
(3) Under the present Act of 1925 the amount levied quarterly from
each employer is assessed as follows:
(a) 30 per cent, based on the earnings of underground miners.
(b) 50 per cent, based on the silicosis rate of the mine.
(c) 20 per cent, based on the amount which the employer is assessed
for normal income tax during the penultimate accounting period
under the Income Tax Act.
From the commencement of the principal Act (i.e. 1 August 1919)
to 31 July 1925, an amount of £200,000 per quarter was levied by the
Board from the scheduled mines, except during the nine months ended
30 April 1922 when £150,000 was levied per quarter.
Under the present Act the levies have been maintained at £200,000
per quarter, except during the first two months after the Act came into
force, when the sum of £200,000 was levied for these two months.
Under the Act of 1924 a special fund termed the " Outstanding
Liabilities Fund " was incorporated under the Compensation Fund, and
in terms of that Act the Government Actuary was required to determine
annually the total outstanding liabilities of the Compensation Fund and
to apportion such liabilities between the various employers. The outstanding liability of each employer to the Compensation Fund becomes
immediately payable to the Board when the mine of the employer is
closed down or ceases operations. This provision was also incorporated
in the present Act, and by arrangements between the Board and the
various employers steps have been taken by the latter, where they are in
a financial position to do so, to set aside amounts annually against their
outstanding liabilities, based on the probable life of each mine. The
annual determination of the outstanding liabilities of the Compensation
Fund, as determined by the Government Actuary at 31 July 1929,
amounted to a present value of £8,296,365, against which the amount
standing to the credit of the Compensation Fund and the Outstanding
Liabilities Fund at that date amounted to £1,896,365, leaving a net
outstanding liability of £6,400,000.

STATISTICS

The following are brief particulars of the expenditure and awards
under the Miners' Phthisis Acts:
(1) Miners' phthisis compensation: annual expenditure in connection
with miners (excluding natives) and dependants:
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From

5.1911 to 31 .7.1912
.8.1912 to 31 .7.1913
.8.1913 to 31 .7.1914
.8.1914 to 31 .7.1915
.8.1915 to 31 .7.1916
.8.1916 to 31 .7.1917
.8.1917 to 31 .7.1918
.8.1918 to 31 .7.1919
.8.1919 to 31 .3.1920
.4.1920 to 31 .3.1921
.4.1921 to 31 .3.1922
.4.1922 to 31 .3.1923
1.4.1923 to 31 .3.1924
1.4.1924 to 31 .3.1925
.1925 to 31 .3.1926
1926 to 31 .3.1927
1927 to 31 .3.1928
1928 to 31 .3.1929
Total to 31.3.1929 is
Total to 30.9.1929 is

¿50,601
¿355,644
¿487,677
¿545,178
¿391,860
¿378,389
¿603,292
¿411,427
¿885,901
¿798,040
¿544,584
¿535,186
¿498,494
¿711,437
¿951,152
¿965,864
¿852,503
¿829,500
¿10,796,729
¿11,208,015

(2) The nine Acts can be divided into four groups because the basis
of compensation and benefits under each group differ, and therefore the
Acts under each group should be read together.
AVERAGE ANNUAL EXPENDITURE UNDER THE FOUR GROUPS

Group (A)
Acts of 1911,
1912 and 1914.
Group (B)
Acts of 1916,
1917 and 1918
Group (C)
Acts of 1919
and 1924.
Group (D)
The Consolidation
Act of 1925.

1.5.1911
to
31.7.1916
1.8.1916
to
31.7.1919
1.8.1919
to
31.7.1925
1.8.1925

31.7.1929

¿372,354
per annum
¿469,811
per annum
¿693,526
per annum
¿911,747
per annum

(3) Miners' phthisis compensation expenditure in connection with
native labourers and their dependants. —• The total amount paid under
the various Acts up to 31 July 1929 is £702,036.
Monthly expenditure. — The average monthly expenditure on compensation in respect of miners' phthisis sufferers (excluding natives) and
their dependants during the last five years amounted to approximately
£72,000.
The cost of administration in connection with the Miners' Phthisis
Board, the Miners' Phthisis Medical Bureau and the Miners' Phthisis
Medical Board of Appeal, which is borne by the Government, during the
past year amounted to approximately £53,000.
The number of miners (excluding natives) and the number of widows
of miners who have been awarded compensation under the various
Miners' Phthisis Acts up to 31 October 1929, amount t o :
(a) Miners
13,866
{b) Widows
5,093

THE ACTUARIAL VALUATION OF THE
OUTSTANDING LIABILITIES UNDER THE
SOUTH AFRICAN MINERS' PHTHISIS ACT
BY

D. SPENCE FRASER,

ACTUARY TO THE

MINERS'

F.F.A., A.I.A.,

PHTHISIS

BOARD

The outstanding liabilities, and their gradual redemption by the
mines, form an important part of the general system that has been
adopted in the Union for financing the benefits granted in respect of
miners' phthisis. This financial system is not necessarily the most
suitable for adoption in other countries, and it is well to preface this
paper with a brief review of the financial systems that may be adopted.
The assessment method will first be described. Each year's income
would be just sufficient to meet the payments falling due during the year
and no fund would be accumulated. This is the method adopted, for
example, by the Dominions for financing old-age pensions to the general
population, each year's payments being met by the Government out of
its revenue for the year, and no moneys being kept in hand in respect of
future payments under existing pensions Or of the accruing liability
in respect of those approaching the age when pensions become payable.
While it is possible to defend the method in the case of a Government
dealing with the general population, the method is not a sound one for
financing miners' phthisis benefits.
Payments of benefits are likely to be lower in the early years and to
increase later. This would certainly be so if, as is likely, the benefits
take the form of pensions or payments by instalments, and the difficulty
would be accentuated if there should be more than one stage of the disease
so that the miner might progress from the first stage to the second stage
(and possibly to a third stage) and receive further benefits. Under a
sound financial method the payments should, as far as possible, be
equalised from year to year.
If the time should arrive when the mining or other industry would
cease to exist, there would be a large outstanding liability, no fund would
be available to meet it, and future payments of benefits would have
to be made by the Government out of its own revenue. These payments
might be a heavy burden on the country, especially as the Government
would also lose the taxation it would doubtless have imposed on the
industry. This difficulty would arise before the industry had actually
ceased to exist, because for some years previously the miners' phthisis
benefits would probably form too heavy a burden for the declining
industry and the Government would be compelled to come to its
assistance.
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The insurance method will now be considered. Under the contracts
issued by a life assurance company, premiums are paid in advance and
the company accumulates a fund which, together with future premiums,
is sufficient to meet its liability for all future claims. On a claim arising,
the money is available to meet it ; if the claim should take the form of a
pension, the capitalised value of the pension would be available.
The insurance method is undoubtedly the best that can be used for
financing miners' phthisis benefits provided circumstances permit of its
adoption. Contributions would be paid in advance during the working
lifetime of the miners, and when miners are certified to have miners'
phthisis, the money would be available to pay immediate benefits and
also to meet future benefits payable to the miners on reaching a further
stage or stages of the disease, and to their dependants on their death.
It may not be out of place to issue a warning to those contemplating
an insurance scheme. It is impossible to estimate accurately in advance
the various contingencies that it is necessary to take into account in the
calculation of the contributions and in the periodical valuations, and
it is therefore essential that there should be a quick and easy means of
adjusting the contributions according to the actual experience. It will
be necessary to amend the basis of calculations frequently, and any
consequent change required in the contributions should receive immediate
effect.
A disadvantage of the insurance method is that it necessitates the
accumulation of a large fund. This fund would be in the nature of a
trust fund, since it would all be required, together with future contributions, to meet future payments of benefits. Unfortunately, legislators
do not always appreciate the object of such a fund, and they might be
tempted to use the fund as an easy means of increasing the benefits
without any further apparent cost to the country. It is therefore
desirable that the insurance fund should be called by such a name, and
protected by such legislative provisions, that it cannot be used for any
other purpose than that for which it has been accumulated.
The insurance method cannot always be adopted, since usually
benefits would be granted only after the mining or other industry had
been in existence for some years, by which time a substantial liability
would have accumulated.
Modified assessment and insurance methods. — Various modifications
of the assessment and insurance methods might be adopted. The
assessment method may be modified by making each year's income
exceed each year's payments, so that a fund, whether adequate or not,
would be accumulated against future liabilities.
The insurance method could be modified in many ways, and usually
the modification would depend upon the circumstances of the particular
industry and country. The natural modification would be to provide
that benefits for miners' phthisis to be created in the future would be
met by insurance contributions and by an accumulated insurance fund,
while benefits for miners' phthisis created in the past would be met by
assessment contributions. The contributions for past phthisis might be
made rather larger than assessment contributions in order gradually to
overtake the existing liability and ultimately to attain a pure insurance
method. .

OUTSTANDING LIABILITIES OF S.A. ACT

677

METHODS ADOPTED IN THE UNION

The financial method which has been adopted in the Union
during the last few years is of such a special nature that in order
to understand why it was adopted it is desirable to review the
methods previously employed.
The first Compensation Act was passed in 1911, and was only
intended to deal with the position temporarily while a comprehensive
measure was being discussed.
In 1912 an Act was passed which laid down a financial basis
on a modified insurance method. The benefits were financed
by means of two funds, the Miners' Phthisis Compensation Fund
and the Miners' Phthisis Insurance Fund. The Compensation
Fund was responsible for the payment of benefits " to persons
entitled thereto who make application for such payment within
the period of two years immediately succeeding the commencement
of this Act " or to whom allowances were granted under the 1911
Act. The Fund consisted of: (a) quarterly levies on the mines,
(¿>) interest on any investments, (c) a contribution of £100,000 from
the Government for the purpose of assisting the poorer mines
and (d) the balance of the fund under the 1911 Act. The Insurance
Fund was responsible for the payment of other benefits, that is,
in respect of persons entitled thereto making application after the
expiration of two years from the commencement of the Act. The
Fund was financed by contributions from the mines and from
miners, which were at the rate of 5 per cent, of wages (2y2 per cent.
from mines and 2% per cent, from miners) during the first two
years of the Act and at the rate of 7% per cent, of wages (5 per cent.
from mines and 2% per cent, from miners) thereafter. The Fund
also received the interest earned on its investments, together
with any fines imposed for the contravention of Mining Regulations
dealing with the prevention of miners' phthisis.
Amending Acts were passed in 1914, 1916, 1917 and 1918, which
all gave additional benefits, but while the Government contributed
in part to some of these additional benefits, the general financial
system was not affected. The benefits payable under these Acts
were in the form of lump sums payable by monthly instalments.
In 1919 a further Act was passed which provided for amounts
payable in one sum for the first two stages of the disease, and for
monthly allowances or pensions payable to miners in the third
stage or to the dependants of such miners. At the same time a new
financial system was introduced.

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The amount of the Insurance Fund, about £675,000, was transferred to the Compensation Fund, which Fund alone is responsible
for the payment of benefits. Quarterly levies are imposed on the
mines for " such an amount as may in the opinion of the Board
be required during that period of three months for the purposes
of the Compensation Fund ". This quarterly levy has been at
the rate of £200,000 (except for three quarters when it was £150,000),
since the commencement of the Act. The Act also required mines
to pay certain amounts on closing down, but these amounts were
found to be less than the proper share of the outstanding liability
that should be paid by such mines and this provision was amended
in 1924. In 1924, and again in 1925, further Acts were passed
granting further benefits and modifying the payments by mines
upon closing down.
When a mine closes down, it is required to pay its correct
proportion of outstanding liability. The first calculation of
outstanding liability as defined by the 1924 and 1925 Acts was
made as at 31 July 1922, and after taking into account the amount
of the Compensation Fund, it amounted to £4,650,000. The 1924
and 1925 Acts added greatly to the outstanding liability, which
by 31 July 1929 had increased to £6,400,000. The proportion of
the outstanding liability due from a mine upon closing down is
paid into a separate Outstanding Liabilities Fund, but from this
Fund a certain amount is transferred each year to the Compensation
Fund for current purposes.

OUTSTANDING LIABILITY

The explanation of the calculation of the outstanding liability
will be facilitated by taking, as an example, the typical case of a
miner whose monthly earnings were £35 3s. 4d. and who has a
wife and one child under age sixteen. On being certified in the
ante-primary stage of silicosis (which is the first stage of the disease)
and leaving underground employment, he would receive £386.
Should he progress to the primary stage, he would receive a further
£193. If he had been first certified in the primary stage the award
would have been £579. Should he further progress to the secondary
stage of silicosis, he would receive a monthly allowance or pension;
the annual amount would be £149 2s. in respect of himself,
£29 16s. 5d. in respect of his wife, and £14 18s. 2d. in respect of
his child, giving a total of £193 16s. 7d. A miner suffering from

OUTSTANDING LIABILITIES OF S.A. ACT

679

tuberculosis is regarded for the purpose of benefits as if he were in
the primary stage of silicosis, and one suffering from silicosis plus
tuberculosis as if he were in the secondary stage of silicosis, and the
primary and secondary stages will be taken to include such cases.
If a miner in the secondary stage should die, his dependants would
receive a pension which in our typical case would be £89 9s. 2d.
If a miner in the ante-primary stage or primary stage should
die, and if the Medical Bureau should certify that he died from
silicosis or from any other cause with which silicosis was present as
a contributing or predisposing factor, his dependants would receive
the same pension as if the miner had been in the secondary stage,
that is, in our typical case, £89 9s. 2d. The miners are practically
all Europeans, but include a few coloured persons.
Natives are also entitled to certain benefits which are paid direct
by the mines to the Director of Native Labour on the natives'
behalf, except that if a native should have worked on a mine that
has closed down and he should afterwards be entitled to benefit,
the amount would be paid from the Compensation Fund. There
are other miscellaneous benefits such as the payment of funeral
expenses.
The Compensation Fund is also responsible for payments to the
Board's Trades and Industries Fund, contributions to the Sanatorium and the like, as well as gratuities to retiring officers of the
Board or to the dependants of deceased officers; but under the
law such payments are not taken into account in calculating the
outstanding liability.
A description of the items taken into account in ascertaining
the outstanding liability each year is contained in the following
ten paragraphs, and it should be explained that no statistics
are given since they are dealt with in a separate paper reviewing
the statistics of miners' phthisis. The rate of interest used in
discounting estimated future payments is taken throughout at
4% per cent, per annum.
(1) Existing monthly allowances or pensions to dependants. —
The pensions to widows and children of deceased miners are easily
valued, the widows' pensions ceasing on death or remarriage
(though on remarriage she receives two years' pension) and the
children's pensions ceasing on death or attainment of age sixteen.
Other dependants may be included where the miners left no widows.
The mortality of widows is taken according to a standard table,
and their rates of remarriage are based upon their own experience.

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(2) Existing pensions to miners. — In valuing the pensions to
miners, it is necessary to take into account the chance of their
wives dying during their lifetime, of children dying or attaining
age sixteen, and of further children being born, since these contingencies would affect the amount payable. The mortality of
miners is taken according to a special mortality table, based upon
the experience of miners in the secondary stage; in this experience
the age is neglected and the mortality depends upon the time
elapsed since miners were certified.
Under this head there is also included the value of reversionary
pensions to dependants on the future death of miners at present
in receipt of pensions. The contingencies stated above and in item
(1) have to be taken into account, including, it will be observed,
the chance of a present wife remarrying after the miner's death.
(3) Future awards to miners in the primary stage and to their
dependants. — Miners in the primary stage must either: (a) die
while still in the primary stage, or (b) progress to the secondary
stage, and the rates of mortality and of progression have been
calculated from the accumulated past experience.
If the miner dies while in the primary stage, there has to be
taken into account the chance of silicosis being a contributing or
predisposing factor, together with the value of the pension that
would then be payable to his dependants.
In the case of miners progressing to the secondary stage, the
value of the benefit at the time of being certified in the secondary
stage can be calculated on the lines laid down in item (2), and
would include the value of the reversionary pension to dependants
on the subsequent death of the miner.
(4) Future awards to miners in the ante-primary stage and to
their dependants. — In the case of miners at present in the anteprimary stage the calculations are rather more complicated,
because the miner may: (a) die while still in the ante-primary
stage, (b) progress to the primary stage, (c) progress to the primary
and secondary stages during the same year, or (d) progress direct
to the secondary stage. The rates for these contingencies have
been calculated from the accumulated data.
For miners dying in the ante-primary stage the present value
of the pensions to dependants (provided silicosis was a contributing
or predisposing factor in death) is calculated on the same lines
as the similar liability in the previous item.

OUTSTANDING LIABILITIES OF S.A. ACT

681

Miners progressing to the primary stage will receive a lump sum,
and in addition there has to be included the liability for death
while in the primary stage or progression to the secondary stage
as in the previous item.
For miners progressing to the primary and secondary stage in
the same year, the liability at the time of progression is represented
by the lump sum on becoming primary and by the pension to
the miner on becoming secondary and to his dependants on his
subsequent death as in item (2).
For miners progressing direct to the secondary stage, no lump
sum is payable, and the liability at the time of progression is
calculated as in item (2).
(5) Future awards to prior Law miners and to their dependants. —
Prior Law miners are those miners who received benefits under the
Acts (excluding the 1911 Act) prior to the 1919 Act.
Where prior Law miners are at present in receipt of monthly
allowances, the value of the reversionary pensions to their dependants are already included under item (2).
Certain benefits may still be payable to prior Law miners, and
if they receive pensions their dependants will also receive reversionary pensions. Certain dependants of prior Law miners (who
are not entitled themselves to further benefits) are also entitled to
pensions on the death of the miners if silicosis was a contributing
or predisposing factor towards death.
It is difficult to obtain an accurate estimate under this item.
The number of prior Law miners can be estimated and a further
estimate made of the number of miners or their dependants likely
to benefit in the future, from which the liability can be calculated.
Alternative calculations are made by a process of extrapolation
from the awards granted in recent years. The method of calculation
is not satisfactory, but fortunately the class is a decreasing one.
(6) Future awards to miners certified by the Bureau who have
not yet received awards and to their dependants. — Certain miners
who have been certified by the Bureau as having silicosis or tuberculosis are still working at the date of valuation. Those with
tuberculosis must give up underground work, and those with
silicosis must give up work within three months or else forfeit
certain benefits. Excluding miners with silicosis who have not
given up underground work within three months, the liability
for those in the ante-primary stage is the lump-sum award plus

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an amount calculated as in item (4); for those in the primary stage
the lump-sum award plus an amount calculated as in item (3);
and for those in the secondary stage an amount calculated as in
item (2). For those who did not give up work within three months,
only the reduced benefits would be taken into account.
(7) Balances of lump-sum awards and similar items. — Certain
benefits are payable by instalments to prior Law miners, and some
balances are still outstanding. Benefits under the later law may,
in certain circumstances, be payable by instalments at the discretion
of the Board. In certain cases where miners have gone overseas
the total amount payable is limited to £750. In all these cases
the liability is taken as the balance still outstanding.
(8) Future awards to working miners not yet certified. — The rate
of production of silicosis or tuberculosis increases with the period
the miners have worked underground, and the outstanding liability
at any time must be debited, in respect of the past service of
working miners, with a portion of the cost of future awards to
miners who are still working and who are free from silicosis or
tuberculosis. It is to be noted that in a pure insurance scheme a
considerable liability would be included under this head.
An alternative way of regarding this item would be to assume
that all the mines closed down at the date of valuation, in which
case there can be no doubt that many of the miners working at the
date of valuation would be found subsequently to be suffering
from silicosis.
It is difficult to obtain an accurate estimate. There are two
methods of approach indicated above, that is: (a) to estimate the
present value of future awards to the present working miners,
and to debit part of that present value to the service of such
miners prior to the date of valuation, and (b) to assume all the
mines closed down, and to estimate the present value of future
awards to such miners on the basis of specially reduced rates of
production. Neither of these methods is satisfactory, but between
the two it is possible to decide upon an amount.
(9) Miscellaneous items. — Under this item are included a few
miscellaneous items such as funeral expenses and the liability
for the benefits to native labourers after a mine has closed
down.

OUTSTANDING LIABILITIES OF S.A. ACT

683

(10) The amount of the Compensation and Outstanding Liabilities
Funds. — The amounts of the liability under the first nine items
are added together, and the amount of the Compensation and
Outstanding Liabilities Funds is deducted therefrom, the balance
forming the outstanding liability at the date of valuation.
The outstanding liability represents the amount that it is
estimated would be required, in addition to the amount standing
at the credit of the Compensation and Outstanding Liabilities
Funds, if all the Mines closed down as at the date of valuation.
The outstanding liability is apportioned among the mines concerned, and on any such mine closing down during the year following
the date of valuation, it is required to pay its portion of the outstanding liability. The amount is paid into the Outstanding
Liabilities Fund, from which every year there is transferred to the
Compensation Fund for current purposes the total interest earned
on the Fund together with 5 per cent, of the amount of the mean
Fund, this annual transfer being intended to give, in a rough and
ready way, the amount required each year to finance the awards
in respect of phthisis created by the mines that have closed down
and have paid their portions of outstanding liability. It should
be added that from a purely financial point of view there is no
object in having two separate Funds, but from a wider practical
point of view it is desirable that there should be a separate Outstanding Liabilities Fund, in order to emphasise that the moneys
are trust moneys paid into the Fund for the special purpose of
financing the awards for which the portions of outstanding liability
have been paid.
There is another matter of interest in connection with the outstanding liability. The amounts to be paid by mines closing
down in the future are high, and it is desirable that the Board
should have security for their due payment. It has been arranged
that the mines (with the exception of a few poor mines) will set
aside sums annually which, accumulated with interest over their
probable future lifetime, should amount to the estimated amounts
payable when they close down. The question of the formation
of a Trust Fund to deal with the accumulation of these annual
sums is at present under consideration. It should be noted that
if a mine should close down and be unable to meet the whole of its
outstanding liability, the shortage would, at the next valuation
and apportionment, be automatically allocated as an addition to
the outstanding liabilities of the remaining mines.

684

PAPERS PRESENTED TO THE CONFERENCE

QUARTERLY LEVIES

In order to have a proper appreciation of the nature of the outstanding liability, it is desirable to explain the relation between the
quarterly levies and the outstanding liability.
It is first necessary to state the annual charges t h a t must be
met from the levies or other sources if the outstanding liability,
after taking closed mines into account, is to remain constant from
year to year. These annual charges are as follow:
(a) The outstanding liability calculated at any 31 July will, if
correctly estimated, provide for all payments of benefit in respect of
phthisis created up to that date, and the current levies must therefore
pay for the cost of any present and future awards in respect of phthisis
created during the ensuing year. Though not strictly accurate, this
amount may be taken as the cost of the awards to miners under new cases
of phthisis certified during the year, and of future awards to such
miners and their dependants.
(b) The next charge consists of the annual interest on the outstanding
liability, this interest being calculated at the valuation rate of 4% per
cent. If all the mines actually closed down at the date of valuation,
the total outstanding liability would be received in cash or securities,
and interest would be earned thereon. With the possible exception of
the portion of the outstanding liability paid in respect of any
mines closing down during the year, no interest is earned on the
outstanding liability, and this interest has consequently to be met out
of current levies.
(c) The last charge consists of a number of miscellaneous items
which are not taken into account in calculating the outstanding liability.
Such items comprise the appropriation to the Trades and Industries
Fund, gratuities to officers, and other items of a similar nature.
Let the position be considered in 1925 when the 1925 Act granting
further benefits had become law, and when the outstanding liability
had become part of the financial system. The levies were to be
for such amounts as would be required for the purposes of the
Compensation F u n d ; these purposes were naturally interpreted
to mean the current payments, but instead it should be taken as the
annual charges, which are at present, and have been for some time,
in excess of current payments. It was also the intention of the
financial system that the " annual transfer " from the Outstanding
Liabilities Fund to the Compensation Fund should likewise be
used for these purposes. The quarterly levies should therefore
be for such amounts t h a t the annual amount payable in levies,
together with the " annual transfer ", should be sufficient to meet

OUTSTANDING LIABILITIES OF S.A. ACT

685

the annual charges. Let it be considered how this system would
work in different circumstances.
If the mines remained at the same working capacity from year
to year, and no new mines were opened, then as the mines closed
down the levies and the outstanding liability would both be affected.
The " annual transfer " would increase, while the number of new
cases of silicosis, with fewer miners, would gradually decrease,
and the result would be that the total levies would decrease to such
an extent that the levies on each remaining mine should remain
approximately constant ; if the rate of production should decrease,
the levies on each mine should similarly decrease. The outstanding
liability would be gradually reduced because of the payments by
mines closing down (after allowing for the " annual transfers ")
and the reduction would approximately be of such an extent that
the portion of outstanding liability applicable to each remaining
mine should remain constant. When the last mine closed down,
the total amount standing to the credit of the Outstanding Liabilities Fund and of the Compensation Fund should be sufficient to
meet all future liabilities.
If the mines should expand and new mines should open, the
position would be more favourable, because the outstanding liability,
representing the accumulated liability of past years, would be
spread over more mines and over larger mines, and it would become
a smaller burden relative to the increased operations of the mines.
The outstanding liability would, in theory, remain for a longer time
than if no new mines were opened or if other mines had not expanded,
because it would be payable in part by mines with longer lifetimes,
but in practice the outstanding liability would finally become
unimportant and could be met by a margin in levies.
The actual position has been unfavourable in one aspect, and
favourable in another. The levies plus " annual transfers " have
not been sufficient to meet the annual charges, and although a
number of mines have closed down and paid substantial sums for
outstanding liability, the total outstanding liability has increased
instead of decreased. The favourable feature has been that the
remaining mines have expanded to a sufficient extent to maintain
the output of gold, so that the mines have, as a whole, further
resources to meet the increased burden. Special circumstances
existed to increase the annual charges within recent years, and it
is hoped that, with the reduction in new cases of silicosis, the
position will soon be reached when without any increase in levies
the annual charges will be met by " annual transfers " and by

686

PAPERS PRESENTED TO THE CONFERENCE

levies. It should also not be overlooked that substantial sums
have already been set aside on trust by the mines towards meeting
their outstanding liabilities.
The financial system thus adopted in the Union, while dictated
by the fact that a very heavy liability was thrown on the industry
by means of the 1919 and later Acts without adequate funds to
meet it, may be regarded as working satisfactorily. As stated
earlier, however, it is not necessarily the system that should be
adopted in other countries.

THE WORK
OF THE MINERS' PHTHISIS BOARD AND
OF THE MINING INDUSTRY IN PROVIDING
EMPLOYMENT FOR SILICOSIS SUFFERERS
AND THEIR DEPENDANTS
BY C.

BOARD;

WILLIAMS,

DEPUTY

C. S. RAATH,

AND B. G. 0 .

CHAIRMAN, MINERS'

MEMBER, MINERS' PHTHISIS

PHTHISIS
BOARD;

O R P E N , PRESIDENT, ASSOCIATION OF MINE

MANAGERS

The following notes are in respect of European miners and
their dependants.
EMPLOYMENT OF SILICOSIS SUFFERERS

The employment of silicotics has engaged the attention of the
mining industry since the passing of the first Miners' Phthisis Act
of 1911 and its subsequent Amendments of 1912, 1914, 1916, 1917,
1918, 1919, 1924 and 1925.
In October 1916 a Silicotic Employment Office was opened under
the aegis of the Association of Mine Managers in order to assist
phthisis beneficiaries to find employment. The running expenses
of this office were provided by the Transvaal Chamber of Mines.
The following classes of work were reserved for silicotics, as far
as possible, on the mines; they were also reserved for employees
who had been permanently injured by accident:
Banksmen.
Motor attendants.
Motor trolly drivers.
Meter house attendants.
General surface work (unskilled). •
Preparation and cartage of mining timber.
Caretakers, single quarters.
Recreation hall and swimming bath attendants.
On sorting stations when separated from crushers.
Ore loading and transport work.
Jumpermen or drill sorters on surface.
Surface sandfilling.
Reduction works assistants (unskilled).

688

PAPERS PRESENTED TO THE CONFERENCE

Secretarial, time office, etc.
Firemen.
Stationary engine-drivers.
Surface pump stations.
Compound guards and watchmen.
As a result of enquiries which have from time to time been
made, the maximum number of jobs on the mines which might
be filled by silicotics provided that suitable men were available
and the jobs became vacant, is estimated to be in the neighbourhood
of 1,000.
The work of the Silicotic Employment Office was carried on
until the passing of the 1925 Act. It was thereafter agreed by all
parties concerned that the matter of finding employment for beneficiary silicotic miners should be taken over by the Miners' Phthisis
Board.
In June 1926 the appointment of an official under the control
of that Board took place.
This official was designated the Employment Officer and the
position, since its inception, has been filled very ably by Mr.
W. J. Carbis, himself a silicotic, who has now taken over all the
work originally carried out by the Silicotic Employment Office.
The Secretarial Department of the Association of Mine Managers,
however, still keeps in touch with the matter and continues to
compile statistics in connection therewith.
Records to date show that:
The total number of applications registered from October 1916
to 31 August 1929 was
The total number of individuals for whom employment
has been found during this period was
The total number of jobs found for these men during this
period has been
There are still on the books

5,223
3,875
6,119
344

Employment was found for these men on gold, platinum, coal,
base metal and asbestos mines, on railways, farm settlements, and
various industrial undertakings in the Union of South Africa.
The miners who first became beneficiaries under the original
Act were principally, what is termed in this country, " oversea
men ", drawn from the mining districts of Great Britain, chiefly
from the counties of Cornwall, Cumberland, Northumberland and
Durham. A large percentage of these men returned to their native
homes on becoming silicotic. In fact, it has been authoritatively
stated that, up to date, 75 per cent, of the miners who have
contracted miners' phthisis are overseas men.

PROVISION OF EMPLOYMENT FOR SILICOTICS

689

Then followed the 1914 Act, passed shortly before the outbreak
of the Great War. It is remarkable t h a t a large number of men
who had been certified to be in the early stages of silicosis, joined
various field units in which they served. Many of these men served
to the conclusion of hostilities. A number of silicotics, who remained
on the Witwatersrand, were able to obtain employment rendered
vacant by the more fit men who had joined the Army.
During an official business visit to Great Britain in 1926, Mr.
C. J. Williams observed t h a t many men, who were in the first
stages of silicosis, and who had returned to England, were engaged
in various occupations there, principally mining, and appeared t o
be as competent to do the work as those men who had not been
declared silicotic.
In this connection, it might be of interest to- quote from a
Memorandum prepared by the Chairman of the Miners' Phthisis
Medical Bureau (Dr. Watkins-Pitchford) in 1919, in response t o
certain enquiries made by the Silicotic Employment Office:
The ante-primary stage of silicosis is not associated with any apparent
impairment of capacity for work. Workers'who are certified to be in
this stage are usually men in good health and able to perform a full
day's work. A complete abandoning of hard-rock mining and the
following of some wholesome occupation should secure that the prospect
of life and health of such men is little if at all depreciated.
The primary stage of silicosis is associated with some impairment of
the capacity for work although the impairment is not of a serious and
permanent nature. In the great majority of instances the reduced
capacity for work is not admitted by the man himself; he is, usually,
to all appearances, in vigorous health.
Silicosis is not a communicable disease: it can be contracted only by
the long-continued inhaling of dust containing minute particles of free
silica. The association of silicotic with non-silicotic workers is entirely
free from risk to the latter.
A more recent statement made by the present Chairman of the
Medical Bureau, Dr. L. G. Irvine, in an address delivered to the
Association of Mine Managers on 20 July 1928 is also of interest:
Dust per se, of course, can and does produce a fibrosis of the lungs
which affects particularly their expansibility. But an uncomplicated
dust fibrosis, at all events as dust conditions are to-day, will not very
seriously incapacitate a man, nor will it directly kill him.
The following information regarding the incidence of miners'
phthisis is derived from the returns of the Miners' Phthisis Medical
Bureau :

690

PAPERS PRESENTED TO THE CONFERENCE

EUROPEAN MINERS: NEW CASES OF SIMPLE SILICOSIS, TUBERCULOSIS
WITH SILICOSIS, AND SIMPLE TUBERCULOSIS, DETECTED AT
PERIODICAL EXAMINATIONS, 1917-1918 TO 1927-1928
Simple silicosis
Year

Primary
and secondary

1917-18
1918-19
1919-20

153
349
398 +

1920-21
1921-22
1922-23

17
5
2

1923-24
1924-25
1925-26

1
1

1926-27
1927-28

Ante-primary

[ 1,456

(556) J
219 1
254 }

752

255 J
318 1
427 \ 1,237

490 J
364
283

Total

Tuberculosis
with
silicosis

116
120
24

Simple
tuberculosis

Total
silicosis

269
469
422 + (556)

1,716

35
36
39

17
24
19

253
283
276

•

812

44
22
25

20
28
7

339
456
497

[ 1,292

11
18
61

2
0

366
283

[

649

42
32

4,469

365

. .

There are at present living in South Africa, south of the Equator,
approximately :
Suffering from silicosis in ante-primary stage
In the primary stage
In the secondary stage (tuberculosis plus silicosis)
Simple tuberculosis
Total

. . .

Men
2,500
2,350
2,200
360
7,410

With regard to the number of silicotics employed in various
parts of the Union of South Africa, Mr. Williams has made the
following estimate:
On surface work, scheduled mines . .
On mines other than scheduled . . . .
By municipalities on the Witwatersrand
By private industries and persons . . .
By railways and public works . . . .
On relief works
On alluvial diggings
Engaged in farming operations . . . .
Established in business
Total

800
450
250
350
200
250
350
350
100
3,100

INTERNATIONAL

LABOUR

OFFICE

STUDIES AND REPORTS
Series F (Industrial Hygiene) No. 13

SILICOSIS
( SUPPLEMENT )

Resolutions adopted by the
International Conference held at Johannesburg
43-27 August 1930

BIBLIOTHEQUE DU B.LT.
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CH = 1211 GENÈVE 22
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GENEVA
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!0P. 1

1930

PRINTED BY ALBERT KUNDIG
GENEVA

RESOLUTIONS
ADOPTED BY THE SILICOSIS CONFERENCE

I. Report upon the Medical Aspects of Silicosis, including /Etiology,
Pathology and Diagnostics
Reporters: Drs. L. U. GARDNER, E. L. MIDDLETON
and

A. J. ORENSTEIN

1. The Conference confined its discussion almost entirely to
silicosis, as the other pneumonoconioses are, with the possible
exception of asbestosis, in the present state of available information,
of less importance, and furthermore have not been subjected to
sufficiently detailed study.
2. Silicosis is a pathological condition of the lungs due to inhalation of silicon dioxide. It can be produced experimentally in
animals.
3. To produce the pathological condition, silica must reach the
lungs:
(a) in a chemically uncombined condition, although the dust
inhaled may be either a natural mixture of silicon dioxide
with other dusts, such as occurs in granite, or an artificial
mixture, such as scouring powder;
(b) in fine particles of the order of less than ten microns. There
is no evidence as to the lowest limit of size in which the
particles may be capable of producing the disease ;
(c) in sufficient amount, and over a certain period of time; these
two factors are reciprocal variants. The minimum of these
two respective factors has not yet been determined.
1
Dr. W. STEUART was unable to participate in the preparation of this report.
He submitted a memorandum which is reproduced later as an Appendix. The
report, including the memorandum, was adopted by the Conference at its
Eleventh Sitting, 25 August 1930.

— 4 —

4. Silica dust plays the dominant role in the production of
silicosis, admixture of other dusts tending to modify the picture in
the direction of that of other pneumonoconioses, in some relation
to the proportion of free silica inhaled.
5. There is experimental evidence that the solubility of silica
in the tissues is an essential factor in the causation of silicosis.
6. Infection of the lung with B. tuberculosis or other pathogenic
organisms, whether it occurs before, simultaneously with, or
subsequent to the development of silicosis, alters the disease and
influences it unfavourably, tuberculous infection being particularly
unfavourable.
7. The establishment of a silicotic process in a lung renders the
subsequent inhalation of other dusts, in themselves relatively
innocuous, capable of producing serious pneumonoconiosis.
8. It was suggested that intermittency of employment retards
the onset of silicosis, but the evidence adduced in support of this,
though suggestive, is not conclusive, when the total period of
exposure is not affected. .
9. It was agreed that the microscopic pathological changes
which may be produced by the prolonged inhalation of silica dust
are:
(c) The development of a condition designated in South Africa
as a dry bronchiolitis, characterised by an accumulation of
dust-filled phagocytes in or in relation to the terminal
bronchioles, with possibly some desquamation of their
epithelium.
(b) The accumulation of dust-containing phagocytes about and
in the intra-pulmonary lymphoid tissue, and their transportation through the lymphatics into the tracheo-bronchial
lymph nodes.
(The conditions described above under (a) and (b) do not
constitute the disease silicosis.)
(c) The gradual development of fibrous tissue within such
accumulations of phagocytes and the formation of characteristic nodules of hyaline fibrous tissue.
(d) Degenerative changes in these foci.
(e) The hyaline nodules increase in size by extension at their
periphery.

— 5 —

Coalescence of adjacent nodules takes place and brings
about involvement of further areas of the lung.
(The conditions described under (c), (d) and (e) constitute
the disease silicosis.)
10. Macroscopically the changes observed in silicosis are :
(a) In the early stage. A variable number of palpable pearlywhite nodules up to 2 or 3 mm. in diameter on the pleural
surface of the lung. On section, the cut surface of the lung
is studded with pigmented foci, widely scattered, a moderate
proportion of which are only just palpable. The tracheobronchial lymph nodes are slightly enlarged and deeply
pigmented, and may exhibit foci of fibrous induration.
(b) Later stages. The fibrotic nodules are increased in number,
size and density, and coalescence of these may be found.
The portion of the lung between the fibrotic nodules may be
emphysematous. The tracheo-bronchial lymph nodes may
be smaller in size than those seen in the early stage and are
fibrosed.
11. The presence of tuberculous infection usually modifies the
pathological appearance. Special attention was drawn to the
three following types :
(a) In which the picture of silicosis above described may be
little, if at all, modified, but in which only a biological test
can demonstrate the presence of B. tuberculosis.
(b) In which the coexistence of silicosis and typical tuberculosis
lesions is easily recognisable.
(c) In which the presence of tuberculosis is easily recognisable,
but the existence of silicosis is more difficult to determine.
12. There is evidence that with B. tuberculosis, in vitro the
period before growth becomes apparent is shortened in the presence
of silica, and that in vivo an environment favourable to the continued
growth of the bacillus is produced in the presence of silica, but the
virulence apparently remains unaltered.
13. In massive silicosis cardiac hypertrophy and subsequent
dilatation may occur. In silicosis with infective processes, cardiac
changes may also occur.
14. No evidence was adduced in regard to involvement of
kydney or liver.

— 6 —

15. For the diagnosis of silicosis as a disease it is necessary to
take into consideration :
(a) the employment history ;
(b) the symptoms and physical signs ;
(c) the radiological findings.
16. The disease can conveniently be divided into three stages,
designated " first ", " second ", and " third " stages.
17. In the differential diagnosis of silicosis from other pneumonoconioses a history must be established of exposure to inhalation of
silica dust in a quantity reasonably commensurate with the clinical
and radiological findings.
18. In the " first stage " symptoms referable to the respiratory
system may be either slight or even absent. Capacity for work may
be slightly impaired. There may be a departure from the normal
in percussion and in auscultatory signs, and the radiograph must
show an increased density of linear shadows, and the presence of
discrete shadows, indicative of nodulation.
19. In the " second stage ", there is an increase of the physical
signs observable in the " first stage ", and the radiograph shows an
increase in the number and size of the discrete shadows indicative of
nodulation with a tendency to their confluence. There must be
some degree of definite impairment of working capacity.
20. In the "-&8±- stage " all the above conditions are grossly
accentuated and indications of areas of massive fibrosis are usual.
There is serious or total incapacitation.
21. Pulmonary tuberculosis may be present in any of the above
described " stages " of silicosis, altering the symptoms, physical
signs and radiographic appearances, and the degree of working
capacity. Its presence must therefore influence the " stage "
classification of the individual, which classification must in these
circumstances be based more on the degree of loss of working
capacity than on physical signs and radiographic appearances.
22. Radiographs may frequently be met with which show a
slight, moderated, or well marked increase beyond the normal
in radiating linear shadows. These may or may not be due to
fibrosis.

— 7 —

23. The inhalation of asbestos dust produces a definite pneumonoconiosis, which may occur also in association with tuberculosis,
and deaths have been recorded.
This pneumonoconiosis is associated with the presence in the lungs
of " asbestosis bodies ", but the mere presence of these bodies in the
lungs or sputum does not constitute evidence of the disease.
For the diagnosis of this pneumonoconiosis the same criteria as
described for silicosis should be applied, mutatis mutandis.
There is not at present sufficient evidence to show definitely to
what extent tuberculosis and this type of pneumonoconiosis react
upon one another.
26. There are other dusts, such as those from marble, coal,
carborundum, etc., which may contain small quantities of silica
and which produce demonstrable lung changes, radiographically
resembling in some cases the appearances observed in early silicosis.
There is not a sufficient body of evidence available to enable a
definite statement to be made of pathological changes in man.
In animal experiments, the inhalation of carborundum dust over
a period of four years has produced fibrosis only in the tracheobronchial lymph nodes; the lungs were entirely free of fibrotic
changes. This, and collateral observations on inhaled granite and
asbestos dusts suggest the hypothesis that to produce pulmonary
fibrosis a sufficient concentration of a relatively insoluble dust must
be brought by the activity of phagocytic cells into intimate contact
with connective tissues. With the dusts last mentioned the
migration of phagocytes, for at least a prolonged period, is ineffective
in establishing such contact in the lung. Only in the tracheobronchial nodes are these conditions realised during a period of
four years.
25. The Reporters beg to recommend that appropriate action
be taken:
(a) To establish an international classification of silicosis on the
lines indicated in paragraphs 16 to 21 inclusive.
(b) To enquire into the possibility of establishing an internationally comparable technique of radiography, and terminology of radiographic findings.
(c) To institute further studies in the correlation of radiographic
appearances, morbid anatomy and symptomatology of silicosis and silicosis with tuberculosis.

— 8—
(d) It is desirable that further scientific research into the aetiology, pathology and diagnosis of silicosis and other dust
diseases should be undertaken on an international basis,
at an early date.

APPENDIX
Memorandum on Radiography of Silicosis
By Dr. W.

STEUART

With a view to obtaining uniformity in films of the thorax in cases
of silicosis a description of the technique used at the Miners'
Phthisis Bureau is given in detail.
The transformer receives three phase current and the secondary
current is rectified by means of six valve tubes. Its output is
much in excess of the capacity of present X-ray tubes.
The X-ray tube used is a metallic DN type. The distance from
focus to film is 48 inches.
The length of exposure and penetration vary with the antero
posterior thickness of the examinee according to the following
table :
Depth of thorax in inches

Time in seconds

Kilovolts

7
'%
8
8X/2
9
9%
10
10%
11
11%
12
12%

0.1
0.11
0.12
0.15
0.175
0.2
0.22
0.23
0.24
0.25
0.26
0.26

61
61
61
62
62
63
63
64
64
65
65
66

F i l a m e n t current
4.3 amperes

Current through t u b e 200 M.A.

The man lies in the prone position on the casette with the tube
above him.
Kodak films and Agfa intensifying screens are employed. If
other makes of screens and films are preferred allowance should

— 9 —
be made in exposure and penetration as films and screens differ
considerably as regards speed.
Casettes are such that uniform contact between films and screens
is secured.
The developing solution is made up according to Kodak's formula,
but to every 5 gallons 4 lb. of sodium carbonate and 4 lb. of sodium
sulphide are added.
The temperature of the developer is 65° F. and the time of
development is five minutes.
Terms used in indicating the diagnosis on X-ray report form:
1. Normal thorax. — This is taken as that of a healthy youth
of about eighteen.
The heart occupies a left medial position and is approximately
triangular in shape, its shadow accounts for about one third of the
area of the thoracic shadow. Its size and shape vary.
The right hilus is seen as a faint rather small shadow but the left
is hidden by the heart.
The diaphragm is dome shaped on each side, the right being
higher than the left. Its level is variable.
The pulmonary tissues throw no shadows so that between the ribs
the skiagram should be uniformly clear.
Radiating from each hilus faint shadows can be made out due to
the roots of the bronchial tree of bronchi vessels and supporting
tissues.
The costal cartilages are transradient.
2. Rather more fibrosis than usual. — This is really the normal
thorax and is seen in healthy adults, but through the continuous
inhalation of dust, smoke, etc., the hilus and bronchial tree shadows
become accentuated, otherwise the picture is that of a normal
thorax.
3. More fibrosis than usual. — This is an extension of the previous
condition. The hilus shadows are denser and the bronchial tree
shadows are more numerous and found throughout the thorax.
It is seen in old people, in cases of chronic bronchitis, asthma,
and in old healed infections. Though not an absolute bar to
underground work it is a factor that goes far in deciding the rejection
of an applicant for mining work.
Then come a series of classifications of conditions that arise from
gold mining, viz.:

— 10 —
4.

Commencing generalised fibrosis.

Moderate generalised fibrosis.

Well marked fibrosis.

Very well marked fibrosis.

8. Gross fibrosis. The commencing generalised fibrosis shows
itself on the Witwatersrand after five or more years depending on
the particular work done and the idiosyncrasy of the miner. It is
a further accentuation of " more fibrosis than usual " and here
and there small pin head shadows can be made out, the first indication of the typical " mottling " of silicosis.
Thereafter the mottling is common to all the others, the chief
indication of the amount of fibrosis being the size of the nodules.
The nodule or unit of mottling varies from about one twentieth
of an inch (1.25 mm.) in diameter in moderate generalised fibrosis to
about a quarter of an inch (7 mm.) in gross fibrosis. These figures
are of course merely approximate and not absolute.
9. Fibrosis partly or mainly silicotic in type. — This is deduced
when the nodules are clearly cut in outline and uniform in distribution throughout the lung.
10. Fibrosis partly or mainly infective in type. — A slow infective
process has the effect of increasing the size of the nodules in certain
areas so that there is no uniform distribution as in pure silicosis.
The outline of the nodules becomes fluffy instead of sharply defined.
The usual infection is tuberculous, but syphilis and other chronic
infective process may cause the same appearances.
11. Appearances suggestive of tuberculosis, r-^- lung. — A
sudden increase in the density of the hilus shadows, increased apical
density or patchy shadows in other lung areas lead to the initialing
of this item in the report.
12. Apparently definite tuberculosis, ^j- lung. — Tuberculosis
is often so well established in periodical cases that there is practically
no doubt as to the meaning of the shadows shown. The appearance
can best be described by imagining some French chalk being thrown
on the film and then rubbed round with the fingers. In the shadows
produced dark areas of varying size may possibly be seen due to
cavities.

— 11 —
The word " apparently " is retained because occasionally syphilis
causes much the same kind of shadow.
13. Peribronchial thickening; hilus thickening. — From the
experience obtained since the commencement of examining individuals who wished to take up mining, it has been found that the
accentuation of the shadows cast by the larger branches of the
bronchial tree (called by the Bureau " Peribronchial thickening ")
and of the hilus shadows is a definite indication of tuberculous
susceptibility and examinees are frequently rejected on this account.
14. Pleural thickening r-~ side.
15. Pleural effusion ^0£ side.
Both of these conditions are readily noted by a radiographical
examination and are considered important on account of their
possible association with tuberculosis.

16. Consolidation —- side. — This diagnosis is given in the case
of any dense shadow that does not alter its size and shape in different
positions of the subject. The causes of consolidation are so numerous
that unless there is some special indication in size, shape or position
no diagnosis is attempted except possibly a query.
17. Heart, asthenic or vertical in type. — Although the heart
shadows vary to a considerable extent within normal bounds,
individuals having a tubular shaped heart or one casting a very
small shadow, are regarded as " suspect " by the members of the
Bureau for the same reasons noted in 13, 14 and 15.
18. Heart enlarged. — In most cases of cardiac disease and pericarditis the heart shadow usurps more than its normal share of the
thoracic space, and attention is always drawn to this variation, as
cardiac disability is often ascribed by outside medical practitioners
as being due to silicosis.
19. Aorta enlarged and aortic aneurysm. — These items have
frequently to be initialed and are often associated with patchy
shadows suggestive of tuberculosis which however disappear after
a course of appropriate treatment for specific disease.
20. Other changes, viz.:
(1) Aerophagy. — Occasionally at the left base it will be found
that the phrenic shadow is pushed up into the thorax and that
below it a negative shadow is shown. This is due to the subject

— 12 —
swallowing air which distends the stomach and may cause discomfort.
(2) Aneurysm of heart. — The condition is very rare, only one
case in 80,000 persons having been noted at the Bureau.
(3) Atelectasis. — Due to obstruction of a bronchus, gives a fanshaped shadow radiating from direction of lung root which is as
dense as a consolidation shadow.
(4) Azygos lobe. — In about one case in twenty thousand there
is an abnormal azygos vein which leads to a shadow in the upper
lobe of the right lung.
(5) Bronchiectasis. — This is indicated in skiagrams by No. 13,
" peribronchial thickening ". A definite diagnosis however can
only be given after a lipiodol injection.
(6) Bronchitis. — Chronic bronchitis gives the picture described
in No. 3, " more fibrosis than usual ".
(7) Calcification. — Calcium is deposited in old inflammatory
foci and in costal cartilage. It is often deposited in silicotic nodules
and in lymphatic glands at the root of the lung. Its presence is
indicated by an increased density of the shadow.
(8) Carcinoma. ••— Carcinoma may occur as a primary or
secondary condition.
In the former case it leads to a consolidated area which increases
in size. In the latter several shadows are seen which are circular
and become larger and larger in diameter until the patient succumbs.
(9) Emphysema. ••— The lung tissue becomes more transradient
so that other shadows are accentuated owing to the increased
contrast.
(10) Empyema. — The shadow is very dense and may occupy
any part of the lung field.
(11) Hodgkins disease. — The thoracic involvement causes a
dense mediastinal shadow.
(12) Hydatid cyst. — This is indicated by a dense oval shadow
with a uniform contour.
(13) Liver and subphrenic abscess normally occur on the right
side. The diaphragm is pushed up into the thorax.
(14) Miliary tuberculosis. ••— The appearance is practically the
same as a moderate generalised fibrosis mainly silicotic in type.

— 13 —
(15) Pneumonia. — The shadow is dense and varies in size
according to the severity of the disease.
(16) Pneumothorax. •-— The collapsed lung can be seen in the
root area. It is surrounded by a uniform negative shadow stretching
to the periphery.

II.

Report of the Sub-Committee on Preventive Measures x
Reporters: Dr.

LORIGA,

Dr.

BADHAM

and Mr.

ROBERTS

1. The Conference dealt with the matter of prevention at its
sessions held on Friday afternoon and Saturday morning, 15 and 16
August 1930.
The first six papers and the papers presented b y the visiting
members, were taken as read, and discussed on broad lines,
members having remarks to make calling freely upon their experience
in regard to one or other of the various aspects of the question.
The feeling of the Conference was t h a t the present opportunity
should be used for an interchange of ideas with a view to mutual
inspiration which would be of value in future research, rather than
t h a t it should be used for the purpose of arriving at conclusions and
the making of recommendations.
2. It was generally agreed that so far as the present heading is
concerned, the disease which it is sought to prevent is t h a t which
arises from the inhalation of free silica (Si0 2 ) as distinct from silica
in chemical combination with other substances.
3. From the information supplied b y various members, the
disease becomes noticeable after differing periods of exposure to
siliceous dust, depending, apparently, upon:
(a)

The amount of dust inhaled ;

(b)

the percentage of free silica contained therein;

(c)

the size-frequency (or fineness) of the particles inhaled;

(d)

the nature and sort of such other substances (including
vapours and gases) as may be inhaled simultaneously, or
otherwise ;

Adopted by the Conference at its Twelfth Sitting, 26 August 1930.

— 14 —
(e)
(/)

the powers of resistance of the individual concerned;
the presence or absence of a complication by an infective
process.

In regard to (a), it was agreed that by the use of water and
other preventive measures the dust contents of air can fairly readily
be reduced to ordinarily invisible amounts. In Australian experience this represents something in the neighbourhood of 4 or 5
milligrams per cubic metre, or say 400 or 500 particles per cubic
centimetre when the particles are from 1 to 10 microns with a
size-frequency ratio of 3. It was, however, evident from the
discussion that it is impossible, under existing conditions, properly
to correlate dust determinations made in different countries, in
different industries and for different purposes, as well as for
different immediate objects.
With regard to (b), it appeared from the information placed before
the Conference that silicosis can be contracted through inhaling for
a sufficient period dust containing percentages of silica varying
from say 95 per cent, down to from 30 to 35 per cent, and even
lower.
In regard to (c), it was pointed out that with existing preventive
measures carried out in certain mining areas there are now relatively
few large particles in the air ; and it appeared from the discussion
that the greatest amount of harm is done by particles of less than
say 3 microns in size. Some of the evidence seemed to suggest that
particles of an ultra-microscopic size are factors in the causation of
the disease, but evidence in this direction was not conclusive.
In regard to (d), the experience on the subject of certain members
went to show that while exposure to various other dusts simultaneously with silica might affect the development of silicosis, the
suggestion that other dusts might be used as an antidote against
silica should be treated with great caution and reserve. Further
research in this direction is urgently called for. It was pointed
out that experimental evidence and practical experience under
working conditions had shown that prior or subsequent inhalation
of other dusts in no way delayed the development of silicosis.
In the course of the discussion under this heading some reference
was made to the alleged immunity from silicosis in some districts
where quartz in company with non-siliceous rock is mined, but it
was pointed out that further investigation had shown in the one case
that the allegation was unfounded in that the existence of silicosis

— 15 —
had been obscured by the migratory nature of the working population; while in other cases it appeared that by reason, possibly,
of the absence of laws relating to compensation, the medical
evidence is not so complete as it might otherwise be, and there
is sufficient room for doubt as to the exact position of the workers
vis-à-vis silicosis. In all cases where there are laws relating to the
compensation of silicotics it is but natural that the examination of
the workers will be more thorough.
In regard to (e), it was generally agreed that this is an important
feature, and there was a certain consensus of opinion that alternative
employment and periods free from exposure to siliceous dust tended
to increase the resistance and thereby delay the development of
silicosis.
4. The discussion on methods for the prevention of dust and the
inhalation thereof fell, on broad lines, under the following
headings :
(a) the use of water;
(b) exhaust draught applied at or near the point of origin of the
dust;
(c) dust traps and masks;
(d) ventilation ;
(e) other methods.
There was something said in favour of each of the methods
referred to. It was agreed that no one method is applicable in
all circumstances, but that in most cases, and especially in mining,
there should be a combination of methods.
With regard to water, it was pointed out that, as far as the
Witwatersrand was concerned, it is used in three different ways,
namely :
(1) to prevent the formation of dust during the drilling of holes,
in blasting, and the handling of broken rock ;
(2) for the wetting of all surfaces with a view to securing a "fly
paper " effect in retaining dust which might settle on those
surfaces ;
(3) for spraying into the air in order to allay dust which had been
formed.
In regard to (1) it was generally agreed that the application of
water at the site of percussion or fracture tends to minimise the
formation of dust, but attention was drawn to the fact that in several

— 16 —
operations, e.g. rock drilling, stone cutting, grinding, etc., sparks
accompanied by dust escape even when the surfaces concerned are
actually under a film of water. •
In regard to (2), the view was expressed that since there is no
particular reason why dust particles of the order of less than
3 microns should settle on the roof and sides of working places,
and that they would settle on the floor only after many hours,
the value of these wetted surfaces "as dust catchers is probably
small.
With regard to (3), it was pointed out that the dust particles with
which the Conference was concerned are of the same order in size as
micro-organisms, and that no one nowadays would expect to catch
micro-organisms by means of a spray. In this connection it was
mentioned as a matter of interest that Lord Lister, in his famous
address delivered at Berlin, had stated that he felt ashamed of
ever having suggested such a possibility in surgery.
The consensus of opinion was that as sprays are of little value for
removing fine dust from the air and that since,. further, a humid
atmosphere and the presence of droplets had been shown experimentally to increase the risk of various infections their use should
be restricted.
This view, however, does not necessarily apply to water blasts used
on the Witwatersrand when firing in development ends, since
while such blasts might not catch much of the finer dust (except by
the subsequent condensation of water vaporised by the heat
generated in blasting) they put into solution some of the noxious
gases and wet the broken rock so as to prevent the escape of the
dust when that rock comes to be handled.
In regard to (b), it was mentioned that exhaust draught was
of great value in those processes of manufacture where there
is an objection to the use of water. In some cases water cannot be
used for fear of spoiling the material, and in other cases the workmen
at times turn it off because it makes them wet. In all such cases,
exhaust hoods should, if applicable, be used. It is necessary,
however, that these hoods should be placed in close proximity
to the work, and that regard should be had to the direction
and speed of rotating objects. As an example of what could be
done in manufacturing processes by the use of exhaust draught,
cases were mentioned of a decrease in the incidence of silicosis
which had followed the abandonment of wet grinding in favour
of dry grinding with suitably applied exhaust draught. It was
also pointed out that before exhaust draught was used for the

— 17 —
dry grinding of metals this process was much more dangerous
than wet grinding, but that since the introduction of efficient
exhaust draught with dry grinding the position had been
reversed.
(1) Dust traps. — As an example of the application of this
method to the drilling of holes in mines, mention was made of an
apparatus (such as is referred to on page 114 of the main volume)
wherein the drill steel operates through an artificial collar held
against the face of the rock; and through which ejector induced
suction led the dust produced in drilling into a dust trap or filter.
This apparatus was said to be very effective and popular in certain
collieries to which laws relating to silicosis had recently been
applied.
(2) Masks. — It appeared from the experience of members that
workmen submit readily to their use only when discomfort from the
inhalation of noxious dust could thereby be avoided.
In some circumstances loose fitting masks of the pressure type
wherein a constant supply of fresh air under positive pressure
is led in through a flexible tube, have proved very efficacious.
Such masks, however, are useful only when the wearers can
perform their work without the necessity of moving from place
to place. The same applies to tight-fitting masks supplied with
air at normal pressure through a tube from a distant source.
Other masks wherein air was inspired through a filtering medium
such as cotton wool, sponges, etc., and expired through a light nonreturn valve, were also described.
Reference was also made to masks in which the air to be inspired
is made to pass through a tortuous path and impinge on damp
surfaces which will retain the dust.
The feeling of the Conference was that while the masks at present
available may be of some value in special circumstances, and particularly in those cases where the formation of dust (and the consequent necessity for precautions) is intermittent; they are so
unwieldy or interfere so much with respiration that their constant
use is impracticable during hard work and especially in a hot and
humid atmosphere.
In regard to (d)—Ventilation—there was but little direct discussion, it being agreed that good fresh air ventilation was desirable,
and indeed essential. It was emphasised, however, that to be
effective the ventilation currents must be properly split and directed
so as to sweep all dust-laden air out of the mine or works, as the

— 18 —
case may be, in much the same way as dangerous gases are swept
out of collieries.
With regard to (e)—Other Methods—mention was made of the
fact that some years ago an endeavour had been made on the
Witwatersrand to prevent the roof and sides of main intake airways
from drying up (and, incidentally, to secure the " fly paper "
effect referred to in 4 (2) and in the remarks thereon) by spraying
those surfaces with solutions containing molasses, calcium chloride',
and other hygroscopic substances, but it had been found that these
preparations absorb moisture so readily that they soon trickle
down into the gutters.
In discussion on this matter it was pointed out that if there really
are any advantages to be derived from the " fly paper " effect,
these solutions, and other sticky substances, could again be tried
in the event of it being found possible at a later date materially
to reduce the humidity of the ventilating currents. It was also
suggested that these solutions might be used instead of plain water,
for preventing the formation of dust in drilling, blasting, and the
handling of rock.
In dealing with the dust formed by blasting, especially by blasting
in development ends, a suggestion was put forward that it might be
possible to project into the air at the time of blasting relatively
large particles of some innocuous flocculent dust which in its
settlement or progress through the mine would catch the harmful
dust in much the same manner as micro-organisms are caught in
water purification plants.
A further suggestion put forward was that saturated steam might
be of some value, it having been found effective in industry in
certain special circumstances.
A still further suggestion put forward was that the escape of dust
from drill holes might be prevented by the use of a preparation
producing a foam.
5. During the course of the discussion, reference was made to
the difficulties experienced by investigators in the different countries
in properly appreciating each others findings. Some of those
difficulties arise from there being no accepted standards for comparisons in regard to various conditions, dust counts, and so on; and
others, through lack of a uniform terminology. The Conference,
therefore, decided to put forward the following suggestions in the
hope that those investigators who were in a position to do so, and
particularly the Research Division of the International Labour

— 19 —
Office, would take them up so as to pave the way for some decisions
and recommendations at a future Conference.
(1) While the methods of conducting and other details
relating to the routine sampling of air are best left to each
local authority, it seems highly desirable that for certain
special critical and scientific studies of dust particles in air and
their effects, there should be established some standard method
which for this special purpose would permit of inter-industrial
and inter-national comparisons; in this connection it is
suggested that the instruments at present approved by the
various experts should be taken into consideration. The
results of these investigations should be communicated to the
Research Division of the International Labour Office for
correlation.
(2) That as photographic and photo-electric cell methods of
dust determination have been successfully applied in certain
special circumstances, research should be undertaken with
regard to such methods, with a view to ascertaining their
adaptability in other circumstances.
(3) In view of the chemical theory of the causation of
silicosis, the importance of estimating the size frequency of
particles has increased owing to the fact that the surface
exposure (which varies greatly with different sized particles)
is the chief factor in the amount of silica which goes into
solution. It is suggested, therefore, that investigators should
include in their work determinations of the size frequency of
particles.
(4) (a) The Conference urges that the investigations
suggested in paragraph (1) should be undertaken with the least
possible delay in all countries which are interested in the
problem.
In view of the thoroughness and outstanding work of research
already carried out on the Witwatersrand, and in view of the
special facilities which exist in that area, the Conference
attaches special importance to the investigations which may be
undertaken on the Witwatersrand and ventures to express the
hope that they will be initiated at the earliest possible moment.
(b) The Conference recommends that as soon as the
standard method referred to in paragraph 1 has been perfected
it should be applied for the purpose of making at least one
complete survey of the dust concentration in dusty industries

— 20 —

throughout the world. The results of this survey should
be communicated to the International Labour Office.
(c) The Conference considers that the survey recommended
in (b) should include an investigation into the relative size
frequency of the dust particles.
Every effort should be made to emphasise the fact that the
prevention of silicosis must be achieved by means of a whole
series of provisions relating to hygiene in mines'—viz. chiefly
by reducing production and diffusion of dust, by maintaining
the purity of the air, and by means of personal hygiene.
(5) That no opportunity should be lost of stressing the
importance of general and localised ventilation as one of the
best hygienic measures in dusty industries.
(6) That the personal protection of the workers should not
be exclusively confined to such protective measures as, for
instance, the wearing of masks, but should be supplemented
by secondary measures such as the provision of suitable change
houses and shelters, and by the regulation of working hours, etc.
(7) That many of the points raised in the prevention and
control of dust call urgently for investigation by the physicists.
Note. — The present report does not concern itself with medical
methods of prevention of silicosis.

III. Report on Prognosis, After-Care and Compensation *
Reporters: Dr. CUNNINGHAM, Professors HALL and KOELSCH, together
with Dr. BADHAM (co-opted)
In presenting our report it has seemed best to deal with each
subject separately.
Prognosis
This subject may be considered under four headings :
Question 1 : What is the prospect of a man exposed to free silica dust
as regards acquiring silicosis ?
This has been considered to depend on various factors:
(a) The nature, silica-content, size of particles, and concentration
of the particular dust to which he is exposed.
Adopted by the Conference at its Twelfth Sitting, 26 August 1930.

— 21 —
Concerning many of these points exact information is not forthcoming and it is desirable that further scientific investigations should
be carried out and the results carefully compared with the incidence
of silicosis amongst the workers.
(b) Period of exposure to dust.
(i) Length of service.
That this is a factor of importance is in accordance with the
views expressed by members of the Conference from every
country represented.
The length of service necessary to acquire silicosis may be
considerably prolonged by improvement in other factors.
(ii) Intermittence of exposure.
On this point the evidence forthcoming was not conclusive.
(c) Age of worker.
There is no evidence that per se this plays any important part.
(d) Physique of worker.
This is a factor of-primary importance. An initial medical
examination to ensure a certain standard of physique should be
generally adopted in those industries in which the risk of exposure
to silica dust is great.
Periodic medical examination of such workers is also essential.
(e) Race.
There is no evidence that this is a factor of importance.
Question 2 : What is the prognosis in a case of silicosis if the affected
man leaves the industry at the first stage of the disease (anteprimary stage of South African legislation) ?
The evidence on this point as regards various industries and from
different countries is somewhat conflicting.
In South Africa on the whole the evidence shows that the downward progress of the disease is in most cases not arrested on leaving
the industry.
In this connection the questions of so-called infective cases, of
reduced economic conditions of life, and of the associated mental
worries probably play no inconsiderable part.
The view taken by the Medical Bureau in regard to the so-called
" infective types " of silicosis is that they do not come under the
classification of tuberculosis with silicosis unless the conditions in
respect of tuberculosis as laid down in the Act are complied with.

— 22 —

The prognosis in such cases of infective silicosis is much less serious
than in cases of tuberculosis with silicosis as the term is used in the
Act. Such cases may live for many years in comparative comfort
unless active tuberculosis intervenes. The preceding evidence
points to the urgent necessity of further experimental study of the
exact conditions connected with silicosis of infective type.
Question 3: What is the prognosis in a case of simple silicosis if he
remains in the industry after the first stage (ante-primary)
declares itself ?
The evidence from South Africa suggests that in so far as mining
is concerned the continuation in underground employment of
sufferers from silicosis will aggravate the progress of the disease,
except in certain selected mining occupations.
As, owing to economic factors connected with compensation,
only a very small number of the silicotics in South Africa do remain
at work underground after the disease has declared itself, the
evidence on this point is somewhat indefinite. It is stated, however,
that there are at present about 150 men in this position, and it is
said that their progress is no worse than those who have left the
mines. Among these 150 men, however, are included a considerable number of higher officials whose duties do not now expose them
considerably to dust and whose economic position remains as good
as before.
It is desirable to obtain exact information as to how far continuation at work in occupations involving exposure to silica dust
will influence the progress of the disease.
Question 4: What is the prognosis in a case of silicosis with tuberculosis ?
(N.B. Before attempting to summarise the views of the Conference on this point it is desirable to make clear exactly what
we mean. According to the terminology used in South African
legislation " tuberculosis means tuberculosis of the lungs or of the
respiratory organs " and is deemed to be present " wherever it is
found by the Bureau either (a) that such person is expectorating the
tubercle bacillus, or (b) that such person has closed tuberculosis
to such a degree as seriously to impair his working capacity and
render prohibition of his working underground advisable in the
interests of his health ".)

— 23 —

This is always serious.
It is worse:
(i) when the tubercular infection occurs at the outset of
silicosis;
(ii) in younger than in older subjects;
(iii) than in cases of tuberculosis alone.
Recommendations
Prognosis of Silicosis
1. Exact information is not forthcoming concerning many of the
points relating to the nature, silica-content, size of particles and
concentration of dust to which a man may be exposed and it is
desirable that further scientific investigations should be carried out
and the results carefully compared with the incidence of silicosis
amongst the workers.
2. The physique of the worker is a factor of primary importance.
An initial medical examination to ensure a certain standard of
physique should be generally adopted in those industries in which
the risk of exposure to silica dust is great.
Periodic medical examination of such workers is also essential.
3. The evidence points to the urgent necessity of further
experimental study of the exact conditions connected with silicosis
of infective type.
4. It is desirable to obtain exact information as to how far
continuation at work in occupations involving exposure to silica
dust will influence the progress of the disease.
Compensation from the Medical Point of View
1. Silicosis complicated or not by tuberculosis constitutes an
occupational disease which may involve reduction of working
capacity.
2. It should be left to competent authorities to decide, in
accordance with their particular conditions, whether other forms
of pneumonoconiosis should be regarded as occupational diseases.
3. In establishing the amount of disability, account should be
taken of the clinical and functional condition as a whole.
4. The determination of disability should be entrusted to an
independent medical expert, or body of experts, possessed of the

— 24 —

requisite clinical and technical knowledge, and having at his or
their disposal suitable apparatus for effecting the examination.
5. It is suggested that removal from all industrial occupations
involving exposure to noxious dust should be enforced in all cases
of open tuberculosis.
6. Where legislation provides for the compulsory removal from
occupations involving exposure to silica dust of workers affected
by silicosis, it is suggested that such compulsory removal should not
necessarily be applied to workers who have been in the same
industry for a period of not less than fifteen years and have reached
the age of forty-five years.
After-Care
1. Sanatorium treatment should be provided for suitable cases.
2. Hitherto most of the rehabilitation schemes have been
unsuccessful. Further investigation into this problem is urgently
called for.