A two part study was conducted to investigate silica (14808607) in lungs of coal miners at autopsy. The prevalence of silicosis at death in coal miners in relation to mining and job categories was investigated in the first part. Lung tissue sections submitted to the National Coal Workers Autopsy Study (NCWAS) for the period 1971 through 1980 were assessed for the presence of silicotic lesions in the pulmonary parenchyma and tracheobronchial lymph nodes. Examination of the tissue sections for the 3,365 coal miners in the study population indicated that 12.6 percent had silicosis, 45.6 percent had macules, 18.9 percent had nodules, and 5.5 percent had progressive massive fibrosis. Silicosis usually occurred against a background of coal workers pneumoconiosis; only 7.2 percent of lungs without coal workers pneumoconiosis showed silicosis. Transportation workers showed the highest prevalence of silicosis, while workers primarily engaged in surface activities at underground mines have the lowest prevalence. Geographical area affected the prevalence of silicosis, with the highest prevalence in miners from Pennsylvania, West Virginia, Wyoming, and Utah. Years in underground mining was found to be clearly correlated with prevalence and severity of silicosis. The second part studied the particle size distributions and number of particles in coal miners lungs. Particulate burdens were determined for lung specimens from 21 coal miners by scanning electron microscope based automated image analysis. Results were compared with those for urban dwellers. In spite of the specimens being chosen to represent a wide range of exposure and medical history, particle size data were similar. Median circular area equivalent diameters for exogenous particles were found to range from 0.47 to 0.87 micrometers (microm); for silica, median diameters ranged from 0.50 to 0.83microm. For specimens from urban dwellers, more than 70 percent of the median diameters for silica fell between 0.5 and 0.8microm.
Final Report, CAN 106, 42 pages, 21 references