Morbidity and Mortality among Underground Coal Miners
thesisposted on 10.12.2012 by Judith M. Graber
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Background: Although often hidden from the public’s view, morbidity and mortality from coal mining remain important public health issues in the United States and internationally. The research goals of this project were to examine the contribution of dust exposures to mortality among underground coal miners in the U.S. and to describe the occurrence of respiratory disease among Ukrainian coal miners. Methods: In the U.S., vital status and cause(s) of death were determined for a cohort of 9,033 miners after an average 37 years of follow-up. Mortality was evaluated with life-table analysis; associations with dust exposures were examined using Cox proportional hazard regression. In Ukraine, cross-sectional health surveys were conducted among stratified random samples of working and former coal miners. Sample weights were developed and used for all analysis to account for the sampling design and non-response. Results: U.S.: Among 5,925 deaths, excess mortality was seen for chronic obstructive pulmonary disease (COPD) (SMR = 1.11; 95% CI 0.99, 1.24), pneumoconiosis (SMR=77.68; 95% CI 70.24, 85.69), and lung cancer (SMR=1.08; 95% CI 1.00, 1.18). Coal-mine dust (CMD) exposure was a significant predictor of non-malignant respiratory disease (NMRD) and lung cancer mortality (hazard ratio for lung cancer given mean cohort exposure= 1.70; 95% CI 1.02, 2.83). Ukraine: Respiratory symptom prevalence was higher among former compared with current miners (shortness of breath: 35.6% vs. 5.1%; chronic bronchitis: 18.1% vs. 13.9%). A significant exposure-response relationship was seen with respiratory symptoms in former miners with years mining and among current miners with years working at the face. Conclusions: Our findings expand upon previous results showing that coal mining puts workers at increased risk for morbidity and mortality from NMRD. A novel finding from the U.S. study was the increased risk of lung cancer mortality and that the risk increased with CMD exposure. The findings on disease occurrence in Ukrainian miners are the first published in the Western literature. A healthy worker effect was seen both studies, which may have downwardly biased our estimates of disease prevalence and mortality.