Carcinogenicity

There is limited evidence in humans of tetrachloroethylene carcinogenicity and sufficient evidence in experimental animals. Consequently, tetrachloroethylene is assigned to Group 2A; it is probably carcinogenic in humans (IARC, 1995).

There are many studies on the risk of cancer from tetrachloroethylene exposure. They have shown a possible association of tetrachloroethylene with cancer of the larynx (Vaughan et al., 1994), tongue (Vaughan et al., 1994; Ruder et al., 2001), lung (Blair et al., 1979; Duh and Asal, 1984; Ruder et al., 2001), liver (Blair et al., 1979; Lynge and Thygesen, 1990), kidney (Katz and Jowett, 1981; Duh and Asal, 1984; reviewed in McLaughlin and Blot, 1997), urinary tract (Katz and Jowett, 1981; Brown and Kaplan, 1987; Ashengrau et al., 1994; Ruder et al., 2001), oesophagus (Vaughan et al., 1994; Weiss, 1995; Ruder et al., 2001), intestine (Ruder et al., 2001), lymphatic and haematopoeitic system (Blair et al., 1990), including leukaemia (Blair et al., 1979; Ashengrau et al., 1994), breast (Ashengrau et al., 1998) and cervix (Blair et al., 1979; Ruder et al., 2001). Some of these findings (e.g., excess cancers of the lung, larynx, oesophagus and cervix) may be due to confounding factors and represent tobacco and alcohol use and socioeconomic status.

These studies are very variable. Many involved dry cleaners (e.g., Blair et al., 1979; Katz and Jowett, 1981; Duh and Asal, 1984; Brown and Kaplan, 1987; Blair et al., 1990; Vaughan et al., 1994; Weiss, 1995; Ruder et al., 2001), who may be exposed to several solvents but primarily tetrachloroethylene. There are also studies involving tetrachloroethylene exposure though contaminated drinking water (Ashengrau et al., 1994), where tetrachloroethylene leached into water from the lining of water pipes. Other studies have looked at aircraft manufacturing workers who are exposed to a number of solvents, (Boice et al., 1999) and workers exposed to chlorinated aliphatic hydrocarbons (Heinemann et al., 1994). In all of these studies individual solvent exposure could not be assessed.

Several studies, mainly by the National Toxicology Program (NTP) and National Cancer Institute (NCI), have demonstrated that tetrachloroethylene is carcinogenic in experimental animals (reviewed in ECETOC, 1990; BUA, 1996). Increased rates of hepatocellular carcinoma have been demonstrated in male and female B6C3F1 mice. Male and female F344 rats had an increased incidence of mononuclear cell leukaemia when treated with tetrachloroethylene, but this strain is known to have a high and variable incidence of this condition and it was probably a strain specific effect. There was no increased incidence of mononuclear cell leukaemia in Osborne-Mendel or Sprague-Dawley rats. Male F344 rats (more than females) have also been shown to develop renal damage when treated with tetrachloroethylene. This damage could represent a preliminary stage of tumourigenesis. All these findings are apparently the result of species-specific effects and are probably not applicable to humans (ECETOC, 1990; BUA, 1996). This is true for both liver (Schumann et al., 1980; Odum et al., 1988) and renal (Green et al., 1990) carcinogenicity.

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