Mortality among U.S. underground coal miners: a 23-year follow-up.

BACKGROUND The mortality experience over 22-24 years of 8,899 working coal miners initially medically examined in 1969-1971 at 31 U.S. coal mines was evaluated. METHODS A cohort life-table analysis was undertaken on underlying causes of death, and proportional hazards models were fitted to both underlying, and underlying and contributing causes of death. RESULTS Elevated mortality from nonviolent causes, nonmalignant respiratory disease (NMRD), and accidents was observed, but lung cancer and stomach cancer mortality were not elevated. Smoking, pneumoconiosis, coal rank region, and cumulative coal mine dust exposure were all predictors of mortality from nonviolent causes and NMRD. Mortality from nonviolent causes and NMRD was related to dust exposure within the complete cohort and also for the never smoker subgroup. Dust exposure relative risks for mortality were similar for pneumoconiosis, NMRD, and chronic airways obstruction. CONCLUSIONS The findings confirm and enlarge upon previous results showing that exposure to coal mine dust leads to increased mortality, even in the absence of smoking.