Diesel exhaust exposure and lung cancer: Adjustment for the effect of smoking in a retrospective cohort study

Background The extent that cigarette smoking may confound the relationship between diesel exhaust exposure and lung cancer was assessed in a retrospec tive cohort study of 55,395 U.S. railroad workers followed from 1959 to 197 6. Methods The relative risk (RR) of lung cancer due to diesel exhaust was ind irectly adjusted using job-specific smoking data from a case-control study Of railroad workers who died between 1981-1982 and from a survey of 514 liv ing workers from an active railroad in 1982. Adjustment factors were develo ped based on the distribution of job specific smoking rates. Results The unadjusted RR for lung cancer was 1.58 (95% CI = 1.14-2.20)for workers aged 40-44 in 1959, who experienced the longest possible duration o f exposure, and the smoking adjusted RR was 1.44 (1.01-2.05). Conclusions After considering differences in smoking rates between workers exposed and unexposed to diesel exhaust in a relatively large blue-collar c ohort, there were still elevated risks of lung cancer in workers in jobs wi th diesel exhaust exposure. Published 2000 Wiley-Liss, Inc.