Critical review of the epidemiological literature on occupational exposure to perchloroethylene and cancer

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Abstract
Of an estimated 500,000 workers in the USA potentially exposed to perchloroethylene (PCE), the largest share is employed in the dry-cleaning industry. PCE, a non-flammable solvent, has commercial applications as a chemical intermediate, metal degreaser and, since the 1950s, primary solvent in the dry-cleaning industry. The International Agency for Research on Cancer (IARC) currently finds sufficient evidence to designate PCE as carcinogenic in animals, with limited evidence in humans. With regard to occupational exposure through dry-cleaning, PCE is considered to be possibly carcinogenic to humans. This review was conducted to assess the current epidemiological literature on PCE and specific cancers. A comprehensive search was conducted to identify all available epidemiological literature pertaining to the carcinogenic effects of PCE. Forty-four papers that provided reasonable data on up to 17 cancer sites were critically reviewed in the context of the available background literature for each cancer site and were assessed on the basis of specified methodological and scientific quality criteria. While all the epidemiological studies selected for review investigated similar exposure–health outcome relationships, there was a broad diversity of proxy measurements of exposure to PCE, as well as numerous specific cancer outcomes of interest. The widespread lack of valid exposure measurements or other adequate indicators of potential for exposure were consistent limitations. We found no evidence of an association between breast, prostate, skin or brain cancer and exposure to PCE. A relationship between PCE and cancer of the following sites was considered unlikely: oral cavity, liver, pancreas, cervix lung. Scientific evidence was inadequate for laryngeal, kidney, esophageal and bladder cancers. The current epidemiological evidence does not support a conclusion that occupational exposure to PCE is a risk factor for cancer of any specific site. Priority areas in which additional data are most needed include cancers of the esophagus and bladder.