Further studies of simple pneumoconiosis in relation to airborne dust exposures underground

This report contains results fron further studies of Pneumoconiosis Field Research data. The analyses described are concerned with the same 4122 coal-face workers whose X-ray changes over 10 years were examined initially three years ago. The earlier analyses were used as a basis for recommendations which led to the adoption of tho current gravimetric dust standards.The first of a set of three studios reported now, gives details of higher nodical risks associated with prolonged exposure to airborne dust for men whose X-rays already show dust retention, as opposed to those whose X-rays show no evidence of dust. It was calculated previously that young men entering tho industry and spending a 35-year period at the coal-face would experience a risk of about 3.4% of ending tho period with category 2 simple pneumocooniosis, if the average dust concentration, over 35 years, to which they were exposed did not exceed m4.3 mg/m3. It appears now that for men who already have some dust in their lungs including those with category 1 simple pneunocordosis) the risk of reaching category 2 sinple pneumoconiosis in ten years is about twice that estimated, over 35 years and at the sane average dust concentration, for men with no signs of dust on their X-rays.The second study shows that estimates of individual non’s dust exposures available now, yield correlations with X-ray changes which arc essentially similar to those reported three years ago, when only colliery mean dust concentrations for 20 pits were available.The third section of the report presents further results fron analyses of individual men’s dust exposures. The effects of age, previous exposure to dust, and the composition of dust sampled over 10 years are considered. It is shown that the most important single factor associated with changes in the X-rays is the ten-year exposure to the mass of all the respirable airborne dust. The number of years spent previously in dusty environments (or alternatively the age of the man concerned) contribute to increased risks, but those effects are small compared with the measured exposures ovor ton years. A relatively small additional effect associated withexposure to quartz dust is apparent for some men, but this result is not consistent for all the miners studied. It is suggested that further analyses of research data arc required before generalisations can bo made from these findings. “”