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Several large-scale studies of cancer mortality and cancer incidence among workers exposed to tetrachloroethylene in dry-cleaning and laundering have been reported. In addition there are two general population drinking water studies, and a number of case-control studies. The latter have been uninformative with regard to the carcinogenic potential of tetrachloroethylene in humans. The occupational mortality studies have generally been limited by the lack of clear information on the levels of exposure to tetrachloroethylene, and by possible confounding due to exposure to other solvents among the subjects studied. In this regard, the widespread use of tetrachloroethylene in the dry cleaning industry did not begin until the 1960s, and assuming a latency for tumour development of 15-20 years, the cancer deaths observed in some of the studies for periods up to 1980-82, if occupationally related, would be attributable to exposure conditions prior to the widespread use of tetrachloroethylene. In those studies where cancer mortality could be distinguished among workers employed in establishments using tetrachloroethylene only, no increases in the risks for liver and renal cancers were observed. In this sub-cohort of tetrachloroethylene-exposed dry-cleaners, elevated mortality was seen only in relation to cancer of the oesophagus, buccal cavity and pharynx, and tongue. The anatomical location of these tumours suggests a role for a locally acting carcinogen, which is not supported by the available genotoxicity and animal carcinogenicity database. Latency considerations for this study also argue against a possible role for tetrachloroethylene. In cancer incidence studies, no increases in risks from exposure to tetrachloroethylene for any specific type of cancer, including risks for liver and renal cancers, have been observed. Furthermore, a recent critical review of the epidemiological literature on occupational exposure to tetrachloroethylene and cancer has considered that the current evidence does not support a conclusion that occupational exposure to tetrachloroethylene is a risk factor for cancer of any specific site, although a firm conclusion cannot be drawn based on the available data. Similarly, no convincing evidence is available for an increased risk of cancer (total cancer, or any specific type of cancer) arising from exposure to tetrachloroethylene in drinking water. Overall, a variety of epidemiological studies have shown no good evidence for an increased risk of carcinogenicity in humans resulting from exposure to tetrachloroethylene. 

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