ARTICLE The Diesel Exhaust in Miners Study: A Nested Case–Control Study of Lung Cancer and Diesel Exhaust

The question of whether diesel exhaust causes lung cancer in humans has been investigated in many studies since the 1980s. In 1989, the International Agency for Research on Cancer (IARC) classified diesel exhaust as a “probable ” carcinogen (IARC classification: Group 2A) based on “sufficient ” experimental evi-dence and “limited ” evidence of carcinogenicity in humans (1). Two meta-analyses (2,3) of epidemiological studies have estimated the summary relative risk for lung cancer for those ever occupa-tionally exposed to diesel exhaust as 1.33 (95 % confidence interval [CI] = 1.24 to 1.44) (2) and 1.47 (95 % CI = 1.29 to 1.67) (3), based on more than 35 studies. A pooled analysis (4) of 13 304 case sub-jects and 16 282 control subjects from 11 lung cancer case–control studies in Europe and Canada yielded an odds ratio (OR) of 1.31 (95 % CI = 1.19 to 1.43) for subjects in the highest vs lowest quartile of cumulative diesel exposure based on a job exposure matrix (4). Although these meta-analyses (2,3) and the pooled analysis (4) suggest a modest but consistent effect, the excesses are in a range that could be explained by confounding (5), particularly fro