Diesel exhaust and lung cancer mortality in potash mining

Background Findings from experimental studies on rodents and from epidemiol ogical studies suggest that diesel exhaust may cause lung cancer. There is evidence that in several occupations, e.g, truck drivers and railway worker s, the risk of lung cancer increases with duration of employment, and expos ure to diesel exhaust provides the most likely explanation for these elevat ions of risk. Methods We investigated the association between lung cancer mortality and e xposure to diesel exhaust in a cohort study. The cohort comprised 5,536 mal e potash miners who were followed from 1970 to 1994. Exposure was assessed from concentration measurements of the total carbon (i.e., elemental and or ganic carbon in total) in personal dust samples. The concentration values w ere multiplied by years of exposure to give a quantitative exposure measure . The concentration levels ranged from 0.12 to 0.39 mg/m(3) total carbon in fine dust. Work histories and smoking habit data were obtained from medica l company records. Causes of death were ascertained from death certificates . Results During the follow-up period, 424 deaths were recorded, including 13 3 of cancer 38 of lung cancer: The relative risk of lung cancer between two groups with high and low exposure was 2.2 (95% confidence interval 0.8-6.0 ). With Cox regression, we found a lung cancer relative risk 1.7 (0.5-5.8) after twenty years of exposure. Extensive scrutiny proved smoking not to be a confounder in this study. Conclusions The principal finding of the study is a doubling of relative lu ng cancer risk after twenty years of exposure in the workplaces with highes t exposure. However; the observed elevation is nonsignificant even at a 90% level. Further follow-up is intended to enhance the study power. Am. J. In d. Med. 36:415-422, 1999. (C) 1999 Wiley-Liss, Inc.