Water Quality Standards

Summary information extracted from: Guidelines for drinking-water quality, 2nd ed. - Vol. 1. Recommendations. - Geneva, World Health Organization, 1993. pp. 63-64.

Tetrachloroethene has been used primarily as a solvent in dry-cleaning industries and to a lesser extent as a degreasing solvent. Tetrachloroethene is widespread in the environment and is found in trace amounts in water, aquatic organisms, air, foodstuffs, and human tissue. The highest environmental levels of tetrachloroethene are found in the commercial dry-cleaning and metal-degreasing industries. Emissions can sometimes lead to high concentrations in ground water. Tetrachloroethene in anaerobic ground water may degrade to more toxic compounds, including vinyl chloride.

At high concentrations, tetrachloroethene causes central nervous system depression. Lower concentrations of tetrachloroethene have been reported to damage the liver and the kidneys.

IARC has classified tetrachloroethene in Group 2B. It has been reported to produce liver tumours in male and female mice, with some evidence of mononuclear cell leukaemia in male and female rats and kidney tumours in male rats. The overall evidence from studies conducted to assess genotoxicity of tetrachloroethene, including induction of single-strand DNA breaks, mutation in germ cells, and chromosomal aberrations in vitro and in vivo, indicates that tetrachloroethene is not genotoxic.

In view of the overall evidence for non-genotoxicity and evidence for a saturable metabolic pathway leading to kidney tumours in rats, it is appropriate to use a NOAEL with a suitable uncertainty factor. A 6-week gavage study in male mice and a 90-day drinking-water study in male and female rats both indicate a NOAEL for hepatotoxic effects of 14 mg/kg of body weight per day. A TDI of 14 µg/kg of body weight was calculated by applying an uncertainty factor of 1000 (100 for intra- and interspecies variation and an additional 10 for carcinogenic potential). In view of the database on tetrachloroethene and considerations regarding the application of the dose via drinking-water in one of the two critical studies, it was considered unnecessary to include an additional uncertainty factor to reflect the length of the study. The guideline value for tetrachloroethene is 40 µg/litre (rounded figure) for a drinking-water contribution of 10%.