Abstract
A 3-year project focusing on the depth profiling of particles and giving their elemental characterizations at various depths has suggested that the reaction of lung tissues to coal mine dust exposures may be dependent upon coal rank-related surface coating of the particles, and ultimately upon specific quartz bioavailability. Previous research clearly indicates a coal rank relationship for the incidence of coal workers' pneumoconiosis and a hypothesized inhibitory role of clays on quartz fibrogenicity. Specifically, epidemiological studies conducted in 1961 and 1963 showed a greater disease incidence for a given cumulative dust exposure among Pennsylvania coal miners who worked in higher rank coal seams. Workers in anthracite mines had a higher incidence of coal workers' pneumoconiosis and progressive massive fibrosis than miners who worked in lower rank coal at equal cumulative exposures. This rank effect in Pennsylvania extended to all ranks of coal seams, that is, the lower the rank, the lower the disease incidence at equal cumulative exposures. Depth profiling data collected over a 5-year period provide evidence for a corresponding rank effect for the bioavailability of respirable quartz particles. This article will focus on the inhibitory effects of clays, the previous results of depth profiling, and the bioavailability findings for various coal seams of various rank. In relating the findings and inferences from various research projects, we will provide evidence to support a need for determining the bioavailability of respirable quartz particles in coal mine dust samples. Eventually these determinations may need to be made routinely yet cost efficiently; thus, there may also be a need for a new analytical technique to determine the bioavailability of quartz in respirable dust samples.