Lung cancer and diesel exhaust: a review

The evidence from animal studies indicates that organic extracts of diesel particulate are mutagenic and carcinogenic. Of four animal inhalation studies, two have been positive and two have been largely negative. The most recent data indicate that inhalation studies may be positive only with high doses of exhaust. Human studies of diesel-exposed occupations have been inconclusive. These studies have focused on truck drivers, bus drivers and garage workers, railroad workers, and heavy equipment operators. Most human studies have not been able to estimate exposure to diesel exhaust. Negative studies have frequently suffered from insufficient potential latency. Positive studies have often failed to control for smoking, and have sometimes involved confounding occupational exposures. In general, the occupational epidemiology of diesel-exposed workers is made difficult by the fact that many of the suspected toxic components of diesel-exhaust are also present in cigarette smoke and in ambient air. There are two ongoing epidemiologic studies in the United States, focusing on railway workers and truck drivers, which attempt to overcome prior difficulties. Preliminary data from the study of truck drivers indicates an excess of lung cancer among workers in the trucking industry compared to the U.S. population, but these data need to be controlled for smoking and analyzed according to diesel exposure.