AN INDUSTRIAL HYGIENE CHARACTERIZATION OF EXPOSURE TO DIESEL EMISSIONS IN AN UNDERGROUND COAL MINE

ABSTRACT

Problems exist in the United States' effort to achieve energy self-sufficiency. Increasing coal production to assure energy self-sufficiency is a prime problem for the rest of the century and beyond. The use of diesels in underground coal mines has been suggested as a mining method to aid in this needed, increased production. Many questions exist about the effects on humans in such environments. 

NIOSH Division of Respiratory Disease Studies has undertaken a research effort to characterize the environments of existing diesel coal mines. The results of one of the studies will be presented. Preliminary assessments of carbon monoxide, nitrogen dioxide, C I-C 5 aldehydes and organic acids, aliphatic hydrocarbons, sulfates, total and respirable dust, and polycyclic aromatic hydrocarbons (PAH) are presented. Nitrogen dioxide and total aldehydes are suggested as possible species to quanitify diesel exposure.

METHOD

Certain chemical species known to be present in diesel exhaust were selected for study . These were particulates, nitrogen dioxide, carbon monoxide, carbon dioxide, cyclohexane extractable hydrocarbons, aldehydes, aliphatic hydrocarbons, organic acids, and sulfates. The collection and analytical methods are summarized in Table 1. The sampling plan was to place a sampler on each major piece of equipment within the breathing zone of the operator. Area samples were also taken in the intake air, the return air, at the haulage station, and at the feeder-breaker as located on the map in Fig. 1. Samples were positioned so as not to interfere with mining operations. The samplers were put in place before mining began and collected after mining was finished to obtain full shift samples. Gas detector tubes for CO, CO2, SO2, and NO2 were collected on a time-available basis.

RESULTS

As seen in Table 2, production from the mine varied widely. Day-to-day variability in the sampler, therefore, is to be expected. Mining operations frequently encounter equipment problems requiring maintenance and causing delays. This problem is reflected in the various down times; when no coal was being mined. Ventilation rates also varied throughout the tunnel network and from shift to shift. This too is responsible for some of the sample variability. Table 2 shows the ventilation rate for the section return to illustrate this point.

Table 3 presents the results of total and respirable dust measurements. The total dust measurements are divided into area and breathing zone samples. Both kinds of samples show the wide variability, reflected in the geometric standard deviation, that would be predicted from the production ventilation variability. The highest area level was obtained from the return air, which is basically the exhaust ventilation for that portion of the mine. The highest breathing zone sample was obtained for the continuous miner operator, which is considered a category that normally experiences higher dust levels, whether the mine is diesel or not. Respirable dust data are shown in Table 4. The conclusions concerning total dust are the same for respirable dust, though on the average, levels are slightly lower except for return air.

Nitrogen dioxide data in Table 5 are 8-h time-weighted averages (TWA). The NIOSH recommended standard for nitrogen dioxide exposure contains a fifteen-minute ceiling value of 1 ppm. While the observed 8 h averages were well below this value, there is no way to determine from these measurements if the limit was exceeded during any 15 rain period. However, these results are important in evaluating the diesel contribution to mine contamination since combustion is the only nitrogen dioxide source in this mine.

Data on cyclohexane extractable material shown in Table 6 were collected on the total and respirable dust samples. Although the means are low, there are excursions above the 1979 TLV of 0.2 m g / m 3 shown in the range. The aldehyde data in Table 7 show relatively low levels on the average; however, these may serve as an indicator of the diesel exposure.
The data in Table 8 relating other measurements show the relatively low levels of other species. The measurement of total hydrocarbons, however, was affected by the high moisture content of the mine atmosphere. Future studies should therefore avoid this methodology.

