Tetrachloroethene
(also known as tetrachloroethylene or perchloroethylene) (endorsed 1996)
Guideline
Based on health considerations, the concentration of tetrachloroethene in drinking water should not exceed 0.05 mg/L.
General description
Tetrachloroethene is used as a solvent in the dry-cleaning industry. It may be present in drinking water through contamination of water sources by spills or discharges. In the United Kingdom and the United States it has occasionally been detected in drinking water at concentrations below 0.001 mg/L. It has been found at higher concentration in contaminated groundwater.
The odour threshold in water is 0.3 mg/L.
Tetrachloroethene is widespread in the environment through use in dry-cleaning and as a metal-degreasing fluid. It has been reported in trace amounts in food, water, aquatic organisms and human tissue.
Typical values in Australian drinking water
Tetrachloroethene has not been found in Australian drinking waters. It is included here to provide guidance in the unlikely event of contamination, and because it has been detected occasionally in drinking water supplies overseas.
Treatment of drinking water
Tetrachloroethene can be removed from drinking water by adsorption onto granular activated carbon or by aeration.
Measurement
A solvent extraction procedure is suitable for the analysis of tetrachloroethene (USEPA Draft Method 551 1990). Sodium chloride is added to the sample and tetrachloroethene extracted using methyl tert-butyl ether. The extract is then analysed using gas chromatography with an electron capture detector. The limit of determination is approximately 0.000004 mg/L (4 ng/L).
Health considerations
Tetrachloroethene is rapidly absorbed after ingestion or inhalation. It is eliminated primarily by the lungs. In the body it is slowly metabolised to trichloroacetic acid.
An extensive review and summary of the human and animal toxicity data for tetrachloroethene is available (IPCS 1984).
The most notable acute effect of short-term exposure is depression of the central nervous system. Short-term studies of up to 3 months using mice and rats reported weight loss, and found some evidence of liver and kidney toxicity at high doses (400 mg/kg body weight per day).
Inhalation exposure to impure tetrachloroethene at 100 ppm and above in air caused hepatocellular carcinomas in mice. Exposure at 200 ppm in air increased the incidence of leukaemia in rats.
Mutagenic activity was not observed in most tests with a number of strains of bacteria. No chromosome aberrations were observed using rat or mouse cells, or human lymphocytes.
The International Agency for Research on Cancer has concluded that tetrachloroethene is possibly carcinogenic to humans (Group 2B, inadequate human data but sufficient evidence in animals) (IARC 1987).
Derivation of guideline
The guideline value of 0.05 mg/L for tetrachloroethene in drinking water was determined as follows:
where:
14 mg/kg body weight per day is the no-effect level from a 90-day drinking water study using rats and mice (Buben and O’Flaherty 1985, Hayes et al. 1986).
70 kg is the average weight of an adult.
0.1 is the proportion of total daily intake attributable to the consumption of water.
2 L/day is the average amount of water consumed by an adult.
1000 is the safety factor in using the results of an animal study as a basis for human exposure (10 for interspecies variations, 10 for intraspecies variations and 10 to account for possible carcinogenicity). An additional factor for the less than lifetime study was not applied as long-term carcinogenicity bioassays were available.
The World Health Organization guideline value of 0.04 mg/L was based on an adult body weight of 60 kg. The difference in guideline values is not significant.
References
Buben JA, O’Flaherty EJ (1985). Delineation of the role of metabolism in the heptatoxicity of trichloroethylene and perchloroethylene: A dose effect study. Toxicology and Applied Pharmacology, 78:105–122.
Hayes JR, Condie LW, Borzelleca JF (1986). The subchronic toxicity of tetrachloroethylene (perchloroethylene) administered in the drinking water of rats. Fundamental and Applied Toxicology, 7:119–125.
IARC (International Agency for Research on Cancer) (1987). IARC Monographs on the Evaluation of Carcinogenic Risks to Humans: Overall Evaluations of Carcinogenicity. An updating of IARC monographs volumes 1 to 42. World Health Organization, IARC, Supplement 7.
IPCS (International Programme on Chemical Safety) (1984). Tetrachloroethylene. Environmental Health Criteria, 31. World Health Organization, IPCS.
USEPA Draft Method 551 (1990). Determination of chlorination disinfection by-products and chlorinated solvents in drinking water by liquid–liquid extraction and gas chromatography with electron capture detection. United States Environmental Protection Agency, Environmental Monitoring and Support Laboratory (EMSL), Cincinnati, Ohio.
Last updated
