Carbon tetrachloride

(endorsed 1996)

Guideline

Based on health considerations, the concentration of carbon tetrachloride in drinking water should not exceed 0.003 mg/L.

General description

Carbon tetrachloride is not produced in drinking water as a by-product of chlorination, but it may be present in chlorine used for disinfection. It has occasionally been found overseas as a contaminant in drinking water supplies at concentrations less than 0.003 mg/L.

The major use of carbon tetrachloride is in the commercial production of chlorofluorocarbons which are used as refrigerants, foam-blowing agents and solvents. It is also used in the manufacture of paint and plastics.

Typical values in Australian drinking water

Preliminary data indicate that concentrations of carbon tetrachloride in major Australian reticulated supplies are significantly less than 0.001 mg/L.

Treatment of drinking water

Carbon tetrachloride can be removed from drinking water by adsorption onto granular activated carbon.

Measurement

A solvent extraction procedure is suitable for the analysis of carbon tetrachloride (USEPA Draft Method 551 1990). Sodium chloride is added to the sample and carbon tetrachloride 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

Carbon tetrachloride is absorbed readily from the gastrointestinal tract, the respiratory tract and the skin. It is distributed to all major organs, with highest concentrations in fatty tissues. It is metabolised in the liver to chloroform and other products, and excreted in breath, urine and faeces.

In humans, acute inhalation can result in central nervous system depression, and kidney and liver toxicity. Occupational exposure to carbon tetrachloride by inhalation has been associated with cancer of several organs but the evidence is inconclusive. No data are available on the effects of long-term ingestion of carbon tetrachloride. In animals, the effects of long-term exposure include toxicity to the liver and kidney. Liver tumours have been reported in studies with mice, rats and hamsters, but at doses higher than those that cause liver toxicity.

Carbon tetrachloride does not exhibit any evidence of mutagenic activity in tests with bacteria or cultured liver cells.

The International Agency for Research on Cancer has concluded that carbon tetrachloride is possibly carcinogenic to humans (Group 2B, inadequate evidence in humans but sufficient evidence in animals) (IARC 1987).

Derivation of guideline

The guideline value of 0.003 mg/L for carbon tetrachloride was determined as follows:

$$\text{ 0.003 mg/L   } = \dfrac{\text{ 1.2 mg/kg body weight per day x 70 kg x 0.1   }}{\text{ 2 L/day x 1000   }} \times \dfrac{\text{ 5   }}{\text{ 7   }}$$

where:

• 1.2 mg/kg body weight per day is the no-effect level based on a 90-day gavage study using mice (Condie 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 for less than lifetime study). An additional factor of 10 for carcinogenicity was not applied as tumours occur at doses that have already resulted in liver toxicity.

• 5/7 is used to convert data based on a 5 day per week gavage study to a 7-day week equivalent.

The World Health Organization guideline value of 0.002 mg/L was based on an adult body weight of 60 kg. The difference in the guideline values is not significant.

References

Condie LW, Laurie RD, Mills T, Robinson M, Bercz JP (1986). Effect of gavage vehicle on hepatotoxicity of carbon tetrachloride in CD-1 mice: Corn oil versus Tween-60 aqueous emulsion. Fundamental and Applied Toxicology, 7:199–206.

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.

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.