DIESEL EXHAUST EXPOSURE AND LUNG-CANCER

We evaluated the relation between occupational exposure to diesel exha ust and cancer of the lung in a meta-analysis of 29 published cohort a nd case-control studies. Twenty-one of the 23 studies meeting the incl usion criteria hail observed relative risk estimates greater than one. Pooled effect measures weighted by study precision indicated an incre ased relative risk (RR) for lung cancer from occupational exposure to diesel exhaust [RR = 1.33; 95% confidence interval (CI) = 1.24-1.44]. Subanalysis of case-central (RR = 1.33; 95% CI 1.18-1.51) vs cohort st udies (RR = 1.33; 95% CI = 1.21-1.47) and of studies that controlled f or smoking (RR = 1.35; 95% CI = 1.20-1.52) vs those that did not (RR = 1.33; 95% CI = 1.20-1.47) produced results that did not differ from t hose of the overall analysis. On the other hand, cohort studies using internal comparisons (RR = 1.33; 95% CI = 1.29-1.58) showed higher rel ative risks than those using external comparisons (RR = 1.22; 95% CI = 1.04-1.44). Heterogeneity between studies was reduced when we stratif ied studies by the occupational setting in which exposure occurred. A positive duration-response relation was evident in those studies that were stratified by employment duration. This meta-analysis supports a causal association between increased risks for lung cancer and exposur e to diesel exhaust.