Prevalence of silicosis at death in underground coal miners.

This study was initiated by the National Institute for Occupational Safety and Health (NIOSH) and the Bureau of Mines (BOM) to determine the prevalence and pathological features of silicosis in coal miners. The population base was 3,365 autopsied underground miners whose records were submitted to the U.S. National Coal Workers' Autopsy Study between 1971 and 1980. This program is voluntary and covers an estimated 10% of all coal workers who die. The mean age at death of the population was 62 years, of whom 75% were current or ex-smokers at the time of death. The average work tenure was 26 years. Lung sections from all cases were reviewed and the type and severity of pneumoconiosis documented. These findings were correlated with years of mining, job history, and geographic location of mine. Classical silicotic nodules were found in 12.5% of the population. There was a significant relationship between length of underground mining and prevalence and severity of silicosis consistent with a dose-response effect. The study also showed that job category and geographic location of the mine were important determinants of silicosis prevalence and that silicosis was strongly associated with higher categories of coal workers' pneumoconiosis.