A review of cancer risk in the trucking industry, with emphasis on exposure to diesel exhaust.

Two large cohort studies of members of US unions in the trucking industries provided some evidence of an increased risk of lung cancer. However, no increased risk was reported in comparisons with an external (unexposed) population, the evidence of an association rests on the results of analyses by duration of employment, or by estimated exposure to elemental carbon. These estimates are subjects to uncertainties and potential misclassification bias. In addition, residual confounding by tobacco smoking and by other occupational exposures cannot be excluded. The hypothesis of carcinogenicity of diesel exhaust (DE) is biologically plausible; an IARC Working Group has recently concluded that the evidence is sufficient to classify DE as human carcinogen. This review of studies of truck drivers illustrates the problems of epidemiology of DE-exposed workers, and stresses the need for careful consideration to potential sources of bias and confounding.