DIESEL-ENGINE EXHAUST AND LUNG-CANCER - AN UNPROVED ASSOCIATION

The risk of lung cancer associated with diesel exhaust has been calcul ated from 14 case-control or cohort studies. We evaluated the findings from these studies to determine whether there is sufficient evidence to implicate diesel exhaust as a human lung carcinogen. Four studies f ound increased risks associated with long-term exposure, although two of the four studies were based on the same cohort of railroad workers. Six studies were inconclusive due to missing information on smoking h abits, internal inconsistencies, or inadequate characterization of die sel exposure. Four studies found no statistically significant associat ions. It can be concluded that short-term exposure to diesel engine ex haust (<20 years) does not have a causative role in human lung cancer. There is statistical but not causal evidence that long-term exposure to diesel exhaust (>20 years) increases the risk of lung cancer for lo comotive engineers, brakemen, and diesel engine mechanics. There is in consistent evidence on the effects of long-term exposure to diesel exh aust in the trucking industry. There is no evidence for a joint effect of diesel exhaust and cigarette smoking on lung cancer risk. Using co mmon criteria for determining causal associations, the epidemiologic e vidence is insufficient to establish diesel engine exhaust as a human lung carcinogen.