Rank of coal and coal workers pneumoconiosis.

Regional differences in the prevalence and severity of coal workers pneumoconiosis have most often been attributed to the rank of coal mined; the higher the rank of the coal, the greater the prevalence of the pulmonary disease. A quantitative, morphologic study was undertaken of lung and heart structure of 312 Appalachian miners who were classified by rank of coal mined. Chronic cor pulmonale was common in all groups. Pulmonary fibrosis increased with the number of parenchymal silica crystals and with bronchiolar goblet cell hyperplasia, an evidence of chronic bronchitis. The association of pneumoconiosis with coal rank in Appalachia is probably fortuitous; the prevalence and severity of the disease are more likely related to chronic bronchitis and exposure to silica.