Silica baseline survey

Annex 2 Construction sector

EXECUTIVE SUMMARY

This Silica Baseline Survey aims to develop baseline intelligence on exposure and the control of respirable crystalline silica in key industry sectors. These sectors are:

Brickworks and Tile Manufacture
Stonemasonry
Quarrying
Construction

The objectives are:

1) to establish whether exposure control practices (both the application of engineering controls and the use of RPE) are adequate to reduce exposures below the WEL for RCS

2) to form an opinion about the long-term reliability of the controls

3) to identify common causes of failures of exposure control

4) to provide data by which the effect of HSE interventions can be assessed.

This annexe to the main SBS report includes the site visit data and detailed discussion of observations in the Construction sector.

Main Findings

Many activities in construction are capable of generating dust and RCS concentrations considerably above WELs, possibly more so as higher powered tools develop. Exposure above the WEL was measured at four sites out of the 9 visited and was foreseeable in a fifth case.

The employers visited had underestimated the extent of exposures, and in many cases had not made the implementation of exposure control a priority.

Assessment of "control competence," i.e. the robustness of the systems underpinning the effectiveness of engineered exposure controls or Respiratory Protective Equipment, suggests that employers who have made assessments are likely to maintain effective ongoing exposure control, those who have not are not likely to achieve control.

Adoption of engineered controls as standard would in most cases reduce exposures to within WELs. Conversely, where controls are not applied (e.g. dry grit-blasting buildings or cutting out mortar without effective on-tool extraction) exposures can greatly exceed WELs.

RPE competency is not adequate to ensure reliable protection when engineered controls are not applied. Where high-value plant has been introduced (e.g. rock-drilling machines in tunnelling, crushers at recycling plants) dust suppression measures are more likely to have been installed than where small items of plant are in use.

The activities considered and the sites visited were a very small proportion of a very large and diverse industry: The data is insufficient to allow any wider extrapolation (either to activities not examined or to other employers) but it is considered that an important general principle has been illustrated. This is that in the absence of a formal approach and structured controls unacceptable exposures are likely to occur.

METHODS

SITE SELECTION

Due to the nature of the industry’s structure (composed of large numbers of small and micro-businesses as well as large organisations) a comprehensive survey to identify the distribution of good and bad hygiene practice across the construction would have been difficult and very expensive. The principal focus was therefore on businesses whose operations involved construction activities known to pose significant risk of exposure to RCS, in particular:

• Businesses utilising plant & equipment capable of generating significant concentrations of dust (e.g.hand-held power tools).

• Activities where developments in dust control technology may have led to the possibility of reductions in RCS exposures.

Initial discussions with businesses were undertaken in order to determine the type and standard of any engineering control measures employed to deal with dust hazards. In considering their exposure control strategies good practice was identified by items such as innovative or well-designed engineering controls, good health & safety management etc. Bad practice included evidence of overexposures, ineffective or poorly designed engineering controls and poor health & safety management.

Information published by the UK Office of National Statistics (ONS) was consulted to explore the breadth of the industry and to suggest high-risk activities. Construction forms Division 45 of the ONS "UK Standard Industrial Classification of Economic Activities 2003 – SIC (2003.)" The range and detail of the subdivisions within Division 45, Construction is shown in Appendix C.

A limited range of Construction activities were selected for monitoring visits, including highway (footpath) maintenance, concrete recycling, blast cleaning and tunnelling operations.

Construction businesses of differing size and capacity were included, ranging from small businesses through a local authority Direct-Labour Organisation to the concrete-recycling plants of a business with a nationwide presence.

After a sufficient number of suitable sites had been identified in each area those selected for inclusion in the survey, with the exception of those previously visited by HSE, were chosen at random. The baseline survey field studies for the construction sector comprised twelve visits to sites and the field studies were conducted by representatives of HSL between December 2005 and May 2007.

The majority of sites volunteered to participate in the survey. Some sites were visited with a representative from HSE FOD.

ASSESSMENT OF CONTROLS

The objective of the SBS was to gather information on the current effectiveness of RCS exposure control in the selected parts of UK industry as well as to measure exposures. A full explanation of the procedure adopted is given in the SBS main project report, but is summarised briefly below.

An important aspect of this study is that control competence is not judged simply by measurement of exposures. The success of exposure control depends on the correct application of a wide variety of measures. Control of emission at source (by engineered controls) is recognised as the most effective measure, but in some circumstances is not practicable, and the use of RPE is necessary to maintain exposure at a safe level. However the ongoing effectiveness of all exposure control regimes depends on the underpinning actions being maintained, termed “competency” here. The SBS site visits assessed the resilience of the control regime by considering the robustness of the range of factors involved. This technique was applied because it was expected to give a better assessment of whether exposures would be likely to remain within the WEL than would a single day’s measurement. The views and professional opinion of the visiting occupational hygienist were therefore captured in a structured way that allowed an objective assessment of competence to be made. The same criteria could then be used at some future date to judge change.

It should be noted that the Control competence ratings ranged from 0 to 5, where 0 indicated manifest failure and was numerically valid.

A similar assessment was made of the effectiveness of the RPE regime if use was necessary to maintain control of exposure. For RPE competence a rating of N/A was included instead of 0, which indicated adequate control by other methods. However this does not address the residual need which has to be acknowledged, e.g. for circumstances when engineered controls have to be worked on. The factors considered are shown in the site competency assessment checklists, which are reproduced in appendix 5 of this annexe. A shift in the profile of these indicators will provide strong evidence of the desired improvements in the industries. The factors themselves are shown below:

“Control competence” was assessed by

• Comprehensiveness of COSHH assessment
• Awareness of literature and information sources
• Application of appropriate, effective, well maintained controls at process
• Degree of management and operator understanding of exposures
• Level of operator training
• Designation of areas and use of RPE when appropriate
• Well informed management
• Competence of supervision

i.e. overall evidence of coordinated approach to control – skills and knowledge available

“RPE competence” was assessed by

• Verifiable policy on RPE linked to COSHH assessment.
• Face fit testing programme
• Equipment routinely available and range of products available through selection process
• Appropriate storage facilities
• Initial training and refresher training
• Operator understands role of RPE in controlling exposure
• Clearly defined roles and responsibilities

Achievement of a rating of 4 for control competence and, if necessary, for RPE competence, was intended to identify sites which "achieved the COSHH Essentials standard”. This indicated a system of exposure control sufficiently robust that ongoing compliance with the WEL could be anticipated. A grade of 5 would have indicated exemplary performance in every aspect of control: it was not seen anywhere.

Worker exposure to airborne respirable dust and RCS was measured during the time on site and generated a further input to the baseline survey. It has to be recognised that the results of the monitoring show exposures as they were on the day, when a visit was made by appointment.

EXPOSURE MONITORING

Worker exposure to airborne respirable dust and RCS was measured during the time on site and generated a further input to the baseline survey. It has to be recognised that the results of the monitoring show exposures as they were on the day, when a visit was made by appointment.

A summary describing the activity, conditions, controls and data from each site report is shown in Appendix B of this document, together with a summary line that is carried forward to the overall data table, included as table 6 in Appendix A.
RESULTS

Control and RPE competence assessments

Of the 8 sites awarded a rating for adequacy of control measures, 3 sites achieved a rating of 4, i.e. achieved a level of control that would be deemed appropriate as per COSHH Essentials. One was allocated 3 and the remaining four sites received ratings of 2.

The average rating awarded across the nine sites was Rating 3, which can be summarised as 'Occasional overexposure. Reasonable awareness of hazard and risk and desire to improve.' This summary of control could be considered to appropriately reflect the overall picture of the industry obtained from this study. Although the result of a very small sample, the bimodal distribution is noteworthy.

Of the 7 sites awarded a rating for adequacy of RPE, no sites achieved a rating of 4, i.e. they did not achieve a satisfactory standard where there would have been strong evidence of selection of suitable and adequate equipment and good practices in use.

Three sites achieved a rating of 3 and the remaining five sites were awarded a rating of 2. One site was not awarded a rating as RPE was neither provided nor utilised.

The average rating awarded across the eight sites was Rating 2, i.e. ‘RPE used to achieve adequate control. Evidence of provision of suitable and adequate equipment but strong evidence of poor practices in use’.

The principal issue identified with the provision and use of RPE was the lack of face fit testing conducted. Regulation 7 of COSHH states that the initial selection of RPE (full / half face masks including disposables) should include fit testing to ensure that the correct device has been chosen (in terms of size and fit etc.). All site H & S representatives [officials] to whom this non-compliance was identified said that they would address this issue as soon as possible or that they had already taken steps to achieve compliance.

Note: No rating was made at any site where RPE was neither provided nor utilised. None of these sites had a standard of control deemed appropriate as per COSHH Essentials i.e. all were awarded competency ratings of lower than 4. Therefore it can be assumed that the reasons that RPE was not introduced may have been because of a false assumption that existing control was satisfactory at these sites.

Exposure monitoring:

Of 29 personal measurements of exposure made during the study, 4 (or 14%) indicated 8-hour TWA exposure above the (new) WEL of 0.1 mg.m-3 RCS. All 4 samples came from different sites: 2 were taken during the removal of mortar prior to repointing buildings, one was from a concrete recycling plant and the other was taken during the grit-blasting of a sandstone building façade. This reflects the observations of control competence, in that the inability to apply controls to adequately "engineer out" exposure in over half the sites visited would be expected to have influenced exposures. Two assessments of exposure made during tunnelling work indicated that with the installed dust suppression on the equipment, rock drilling would not be likely to cause exposure above the WELs for RCS.  Shotcreting, however, generated particulate that might cause exposure to respirable dust above the WEL.

In the rest of the survey 4 samples also revealed exposure to respirable dust above 4 mg.m-3 , the threshold at which it becomes a "Substance Hazardous to Health" and thus within the scope of the COSHH regulations. These samples were all from building restoration or maintenance operations, characterised by small peripatetic teams often working as franchisees of organisations with a national presence principally in a marketing role or supplying equipment.

