Cancer in relation to occupational exposure to perchloroethylene.

Exposure to perchloroethylene (PCE) occurs in a number of occupational settings in which organic solvents are used, and, in particular, is widely prevalent in the dry-cleaning industry. This review summarizes the results of studies of the occurrence of the individual types of cancer in dry cleaners. Two of those cancers of greatest a priori concern (because of results in PCE-exposed experimental animals)--liver cancer and leukemia--have not occurred with increased frequency among persons employed in the dry-cleaning industry. Rates were elevated by about a factor of two for esophageal and bladder cancers, but not increased clearly for any other site. The excess mortality from esophageal cancer was well beyond the limits of chance, based on a total of 23 deaths that occurred in the two principal cohort-studies of dry cleaners. There was some indication of a particularly high risk associated with prolonged employment and a long interval since first employment. However, the possible confounding effect of the combination of cigarette smoking and heavy alcohol consumption, a very strong risk factor for the development of esophageal cancer, could be taken into account only partially in these studies. With regard to bladder cancer, the limited data available suggest that the observed increased risk could be due to exposure to other solvents than PCE used in dry cleaning. The potential influence of occupational exposure to PCE on the occurrence of esophageal and bladder cancer needs continued examination in further follow-up of existing cohorts of dry cleaners, the assembly of additional cohorts, and in large case-control studies that ascertain occupational exposures in some detail.