Leukemia in petroleum refinery workers: a review of recent studies.

A previous review of the published epidemiologic literature on cancer risk in workers in the petrochemical industry indicated excess risks of leukemia and several other cancers. Here we update this review, focusing on the risk of hematologic cancers (for example, leukemia and lymphoma) reported in studies of oil refinery workers published in the last ten years. Limitations of recent studies are discussed, including the dilution of highly exposed groups of workers with workers with little or no exposure. We consider the evidence for a "safe level" or threshold of benzene exposure in the light of its ability to cause several types of damage, including damage to stem cells which may cause a variety of malignancies. We conclude that there is evidence of a slight increase in mortality from leukemia among oil refinery workers, particularly among those employed before 1950. And continuing exposures to benzene and other carcinogens occurring in this industry should be controlled.