1,1,1-Trichloroethane

(endorsed 1996)

Guideline

Data are inadequate to set a guideline value for 1,1,1-trichloroethane in drinking water.

General description

1,1,1-Trichloroethane may be present in drinking water as a result of contamination from industrial discharges and spills. In the United States, 1,1,1-trichloroethane has occasionally been found in water supplies at concentrations ranging from 0.0002 mg/L to 0.02 mg/L.

It is widely used as a cleaning solvent, and is used to clean electrical equipment, motors, electronic components, printed circuit boards, photographic film, and various metal and plastic parts. It is also used as a lubricant in metal-cutting oils and as a component in inks, correction fluid and drain cleaners.

Typical values in Australian drinking water

1,1,1-Trichloroethane 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

1,1,1-Trichloroethane can be removed from drinking water by adsorption onto granular activated carbon, by aeration and by boiling. If aeration is used for removal, consideration should be given to effects associated with inhalation.

Measurement

A solvent extraction procedure is suitable for the analysis of 1,1,1-trichloroethane (USEPA Draft Method 551 1990). Sodium chloride is added to the sample and 1,1,1-trichloroethane 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 0.000008 mg/L (8 ng/L).

Health considerations

1,1,1-Trichloroethane is absorbed rapidly and efficiently from the human gastrointestinal tract and the lungs. It is metabolised to a very limited extent (probably less than 6%) by both humans and animals.

An extensive review and summary of the human and animal toxicity data for 1,1,1-trichloroethane is available (IPCS 1992).

Inhalation of high concentrations of 1,1,1-trichloroethane has proved fatal, causing acute congestion of the lungs, fluid build-up and fatty deposits in the liver.

In animals, long-term studies have reported diminished body-weight gains at high doses (above 350 mg/kg body weight) but data were insufficient to determine no-effect levels. Liver tumours were observed in mice, but not in rats, fed 1,1,1-trichloroethane for 2 years; however, the study reported a high number of accidental deaths in both the control and study groups, and the results may not be significant.

Mutagenic activity has been reported in tests with some strains of bacteria, but not others.

The International Agency for Research on Cancer has concluded that 1,1,1-trichloroethane is not classifiable as to its carcinogenicity in humans (Group 3, no adequate data in humans, inadequate evidence in animals) (IARC 1987).

Derivation of guideline

The World Health Organization health-based guideline value of 2 mg/L was based on a short-term inhalation study. The data were not considered to be sufficient to set an Australian guideline.

Reference

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) (1992). 1,1,1-Trichloroethane. Environmental Health Criteria, 136. 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 (ESML), Cincinnati, Ohio.