Emphysema and pulmonary impairment in coal miners: Quantitative relationship with dust exposure and cigarette smoking

Coal miners have been shown to be at increased risk of developing chronic obstructive pulmonary diseases including emphysema. The objective of this study was to determine whether lifetime cumulative exposure to respirable coal mine dust is a significant predictor of developing emphysema at a clinically-relevant level of severity by the end of life, after controlling for cigarette smoking and other covariates. Clinically-relevant emphysema severity was determined from the association between individuals’ lung function during life (forced expiratory volume in one second, FEV1, as a percentage of predicted normal values) and emphysema severity at autopsy (as the proportion of lung tissue affected). In a logistic regression model, cumulative exposure to respirable coal mine dust was a statistically significant predictor of developing clinically-relevant emphysema severity, among both eversmokers and never-smokers. The odds ratio for developing emphysema associated with FEV1 <80% at the cohort mean cumulative coal dust exposure (87 mg/m 3 x yr) was 2.30 (1.46-3.64, 95% confidence limits), and at the cohort mean cigarette smoking (among smokers: 42 packyears) was 1.95 (1.39-2.79).