One Hundred Years of Federal Mining Safety and Health Research

Novel approaches undertaken by NIOSH staff have recently identified counties in the coalfields
with high rates of rapid pneumoconiosis progression among active miners [Antao et al. 2005,
2006]. The reasons for this apparent rapid progression and continuing occurrence of progressive
massive fibrosis are not entirely clear. However, they may result from a combination of
inadequacies in the present dust limit and its method of enforcement. Certainly, these
occurrences point to the need for continued monitoring activities to track disease and for
continued research on enhanced exposure assessment and dust control.
6.2.3 Personal Dust Monitor (PDM)
In 1996, the Secretary of Labor asked NIOSH to develop a better dust monitoring instrument for
coal mining. At that time, the coal mine personal sampler, a rugged and reasonably accurate
instrument, had been in use for about 30 years. Nevertheless, because the internal filter must be
weighed in a lab, there was always a delay of a week or more in getting measurement results
back to the mine operator. Meanwhile, the miners themselves seldom had any knowledge of
their dust exposure measurements. This delay meant that miners could be exposed to excessive
dust levels without having the chance to immediately correct the problem and avoid
overexposures.
Initial work to develop a better dust monitoring instrument focused on a machine-mounted areasampling
monitor, but NIOSH found this to be inadequate for compliance sampling of miners’
dust exposure. Further, NIOSH findings showed no consistent relationship between personal
sampling equipment worn by workers and area samples.
The work was then redirected in 1999 to develop a mass-based, continuous dust monitor that was
small and light enough to be worn by the workers. Called a personal dust monitor, or PDM, it
retained most of the features of the previous machine-mounted area monitor. One of the most
important of these features was its ability to read out the gravimetric dust level during the work
shift and to predict the full-shift dust level if nothing changed in the mining situation. This
allowed workers and mine management to immediately correct dust controls to lower dust levels,
thereby avoiding overexposure of the workers. At the end of the shift, the PDM data could be
downloaded into a computer and stored for future reference. The concept was to empower
miners and mine management to act on possible dust overexposures in real time. Conveniently,
the dust monitor was built into a miner’s cap lamp unit so that miners were putting on their dust
monitors when they put on their cap lamps. The PDM underwent an extensive field evaluation
to assess accuracy, reliability, and acceptance by mine workers, and results of the field
evaluation were very positive (see Figure 39).
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