Coal mine health seminar. A joint staff conference of the Bureau of Mines and the National Institute for Occupational Safety and Health. Washington, DC: U.S. Department of the Interior, Bureau of Mines, IC 8568, 1972 Jan; :10-17
Prevalence of coal workers' pneumoconiosis (CWP) among working coal miners at underground mines in the United States was investigated in two studies. In the first, miners received chest X-rays, simple breathing tests, and completed a detailed medical and occupational history. X-rays were classified by three physicians using the UICC Cincinnati Classification system. More than 9000 workers in nine states were examined, including both bituminous and anthracite miners in Pennsylvania. In the coal operators' examination study, X-ray films were read by three categories of trained readers of ascending expertise. In this study, 56731 miners in 19 states were X-rayed. In the first study, 70 percent of workers examined were free of CWP. Twenty one percent of all miners had category 1 CWP, 5.7 percent of miners had category 2 CWP, 0.6 percent had category 3 CWP, and 2.4 percent had complicated CWP. Among Pennsylvania miners, 14.3 percent of anthracite miners had complicated CWP while only 2.3 percent of bituminous miners were so diagnosed. In the coal operators' examination study, 70.3 percent were asymptomatic, 7.9 percent had category 1 CWP, 3.1 percent had category 2 CWP, and 0.2 percent had category 3 CWP. Complicated CWP was seen in 1.2 percent of miners. The author concludes that differences in the results of the two studies are such that it is not advisable to merge the results in their present form. Differences arise because the two studies differ materially in the composition of the sample, in the procedures for obtaining a final interpretation of the X-ray, and in the quality of the films.