Reanalysis of Diesel Engine Exhaust and Lung Cancer Mortality in the Diesel Exhaust in Miners Study Cohort Using Alternative Exposure Estimates and Radon Adjustment

Abstract

The Diesel Exhaust in Miners Study (DEMS) (United States, 1947-1997) reported positive associations between diesel engine exhaust exposure, estimated as respirable elemental carbon (REC), and lung cancer mortality. This reanalysis of the DEMS cohort used an alternative estimate of REC exposure incorporating historical data on diesel equipment, engine horsepower, ventilation rates, and declines in particulate matter emissions per horsepower. Associations with cumulative REC and average REC intensity using the alternative REC estimate and other exposure estimates were generally attenuated compared with original DEMS REC estimates. Most findings were statistically nonsignificant; control for radon exposure substantially weakened associations with the original and alternative REC estimates. No association with original or alternative REC estimates was detected among miners who worked exclusively underground. Positive associations were detected among limestone workers, whereas no association with REC or radon was found among workers in the other 7 mines. The differences in results based on alternative exposure estimates, control for radon, and stratification by worker location or mine type highlight areas of uncertainty in the DEMS data.

Figure 1.

Respirable elemental carbon (REC) metrics, Diesel Exhaust in Miners Study (DEMS), United States, 1947–1997. The solid line shows a metric derived in part from extrapolated carbon monoxide measurements, as developed and used by Attfield et al. (1) and Silverman et al. (2) (DEMS_REC). The dashed line shows a metric derived from diesel engine horsepower and mine air ventilation, without extrapolation from carbon monoxide measurements, as developed and used by Crump et al. (10) (ALT_REC). A) Mine A, limestone; B) Mine B, potash; C) Mine D, potash; D) Mine E, salt (halite); E) Mine G, trona; F) Mine H, trona; G) Mine I, trona; H) Mine J, potash.