Risks of Occupational Respiratory Diseases among U.S. Coal Miners

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Abstract
The excess (exposure-attributable) risks of certain respiratory diseases and outcomes were estimated for U.S. coal miners exposed to respirable coal mine dust for various durations and concentrations, including a 45-year working lifetime at the current 2-mg/m3 standard. Multiple linear and logistic regression models were used to compute predicted prevalence and excess risk of disease, using data and regression results from published epidemiological studies of U.S. coal miners. Disease outcomes evaluated include simple coal workers' pneumoconiosis, progressive massive fibrosis, and clinically significant deficits in lung function, measured as forced expiratory volume in 1 second of < 80% or < 65% of predicted normal values. Point estimates of excess risk of progressive massive fibrosis ranged from 1/1000 to 167/1000 among coal miners exposed to respirable coal mine dust at a mean concentration of 2 mg/m3 for 45 years. This range reflects coal rank and study differences. Point estimates for an excess risk of forced expiratory volume in 1 second of 3 and durations as low as 15 years (most coal ranks). Sources of uncertainty associated with these results were considered. Based on these and previous analyses, U.S. coal miners are predicted to have a substantial risk of developing occupational respiratory diseases from working lifetime exposures to respirable coal mine dust at the current 2-mg/m3 standard. To reduce this risk, the National Institute for Occupational Safety and Health (NIOSH) recommends that worker exposures to respirable coal mine dust be kept below 1.0 mg/m3 during each work shift (as a time-weighted average concentration for up to 10 h/day during a 40-hour workweek).