VARIABILITY OF PARTICLE SIZE-SPECIFIC FRACTIONS OF PERSONAL COAL-MINEDUST EXPOSURES

This study estimated the ratio of the tracheo-bronchial dust fraction to the fraction collected by a respirable dust sampler for a variety o f job classifications found in conventional, continuous, and longwall coal mining sections. The ratios could then be applied in epidemiologi c studies to existing respirable dust measurements to estimate thoraci c mass concentrations for evaluation of the relative importance of the respirable and thoracic dust fractions to obstructive lung disease. D ata collected include particle size distributions from four U.S. under ground coal mines using eight-stage personal cascade impactors. A tota l of 180 samples were examined by mine, occupation and occupations gro uped by proximity to the mine face, and by mining technology. Several fractions-that collected by the IO-mm nylon cyclone, the American Conf erence of Governmental Industrial Hygienists respirable and thoracic p articulate mass fractions, and the estimated alveolar and tracheo-bron chial deposition fractions-were estimated. These were not significantl y different when grouped by occupation, by proximity of work to the mi ne face, or by the type of mining technology in use. Distributions fro m one mine varied from the others, perhaps because it used diesel equi pment in the haulage ways, which contributed to the fine aerosol fract ions. Results suggest that although the tracheo-bronchial dust fractio n may contribute to the development of obstructive lung disease, occup ation specific tracheo-bronchial dust fractions are not likely To prod uce stronger exposure-response estimates than the historically collect ed respirable dust concentrations.