Trichloroethylene (TCE)

(endorsed 1996)

Guideline

Data are inadequate to set a guideline value for trichloroethylene in drinking water.

General description

TCE may be present in drinking water as a result of direct contamination of water sources, or from atmospheric contamination of rainfall. In the United States, TCE has been detected in the water supplies of about 20% of cities tested, with mean concentrations of 0.02 mg/L or less.

TCE is used in cleaning fluids, as an industrial solvent and as a degreaser for metal components. The most significant route of exposure to humans is inhalation, particularly from use as a cleaning fluid.

Typical values in Australian drinking water

TCE 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

TCE can be removed from drinking water by aeration, or by adsorption onto granular activated carbon.

Measurement

A solvent extraction procedure is suitable for the analysis of TCE (USEPA Draft Method 551 1990). Sodium chloride is added to the sample and TCE 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 0.000002 mg/L (2 ng/L).

Health considerations

TCE is readily absorbed by all routes of exposure and distributed to all tissues. It is metabolised to reactive epoxides and the trichloro derivatives of acetaldehyde, ethanol and acetic acid.

An extensive review and summary of the human and animal toxicity data for trichloroethylene is available (IPCS 1985).

In humans, TCE is a known central nervous system depressant and has been used as a general anaesthetic. Liver damage has been reported in people occupationally exposed to high concentrations.

There is some evidence that TCE induces liver and lung tumours in various strains of mice. In an inhalation study, TCE produced a dose-related increase in malignant lymphomas in female mice exposed to 100 ppm or above in air. TCE is a weakly acting mutagen in bacteria and yeast.

The International Agency for Research on Cancer has concluded that TCE is not classifiable as to its carcinogenicity in humans (Group 3, inadequate evidence in humans and limited evidence in animals) (IARC 1987).

Derivation of guideline

The World Health Organization health-based guideline value of 0.07 mg/L was based on a 6-week feeding study using mice which identified a low-effect level but not a no-effect level. No long-term studies are available to establish a no-effect level. The data were not considered to be sufficient to set an Australian guideline.

References

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) (1985). Trichloroethylene. Environmental Health Criteria, 50. 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.