Diesel Exhaust Exposure and Cause-Specific Mortality in the Diesel Exhaust in Miners Study II (DEMS II) Cohort

Abstract

BACKGROUND: With the exception of lung cancer, the health effects associated with diesel exhaust for other cancers and nonmalignant health outcomes are not well understood. OBJECTIVES: We extended the mortality follow-up of the Diesel Exhaust in Miners Study, a cohort study of 12,315 workers, by 18 y (ending 31 December 2015), more than doubling the number of observed deaths to n = 4,887, to evaluate associations between mortality and diesel exhaust exposure. METHODS: Quantitative estimates of historical exposure to respirable elemental carbon (REC), a surrogate for diesel exhaust, were created for all jobs, by year and facility, using measurements collected from each mine, as well as historical measurements. Standardized mortality ratios (SMRs) and hazard ratios (HRs) were estimated for the entire cohort and by worker location (surface, underground). RESULTS: We observed an excess of death for cancers of the lung, trachea, and bronchus (n = 409; SMR = 1:24; 95% CI: 1.13, 1.37). Among workers who ever worked underground, where the majority of diesel exposure occurred, excess deaths were evident for lung, trachea, and bronchus cancers (n = 266; SMR = 1:26; 95% CI: 1.11, 1.42). Several nonmalignant diseases were associated with excess mortality among workers ever-employed underground, including ischemic heart disease (SMR = 1:08; 95% CI: 1.00, 1.16), cerebrovascular disease (SMR = 1:22; 95% CI: 1.04, 1.43), and nonmalignant diseases of the respiratory system (SMR = 1:13; 95% CI: 1.01, 1.26). Continuous 15-y lagged cumulative REC exposure <1,280 lg/m3-y was associated with increased lung cancer risk (HR = 1:93; 95% CI: 1.24, 3.03), but the risk declined at the highest exposures (HR = 1:29; 95% CI: 0.74, 2.26). We also observed a significant trend in non-Hodgkin lymphoma (NHL) risk with increasing 20-y lagged cumulative REC (HRTertile3 vs: Tertile1 = 3:12; 95% CI: 1.00, 9.79; p-trend = 0:031). DISCUSSION: Increased risks of lung cancer mortality observed in the original study were sustained. Observed associations between diesel exposure and risk of death from NHL and the excesses in deaths for diseases of the respiratory and cardiovascular system, including ischemic heart disease and cerebrovascular disease, warrant further study and provide evidence of the potential widespread public health impact of diesel exposure.