Water Quality Standards

Summary information extracted from: Guidelines for drinking-water quality, 2nd ed. - Vol. 1. Recommendations. - Geneva, World Health Organization, 1993. pp. 57-58.

Carbon tetrachloride is used principally in the production of chlorofluorocarbon refrigerants. It is released into air and water during manufacturing and use. Although available data on concentrations in food are limited, the intake of carbon tetrachloride from air is expected to be much greater than that from food or drinking-water. Concentrations in drinking-water are generally less than 5 µg/litre.

Carbon tetrachloride has been classified in Group 2B by IARC. It can be metabolized in microsomal systems to a trichloromethyl radical that binds to macromolecules, initiating lipid peroxidation and destroying cell membranes. It has been shown to cause hepatic and other tumours in rats, mice, and hamsters after oral, subcutaneous, and inhalation exposure. The time to first tumour has sometimes been short, within 12–16 weeks in some experiments.

Carbon tetrachloride has not been shown to be mutagenic in bacterial tests with or without metabolic activation, nor has it been shown to induce effects on chromosomes or unscheduled DNA synthesis in mammalian cells either in vivo or in vitro. It has induced point mutations and gene recombination in a eukaryotic test system.

Carbon tetrachloride, therefore, has not been shown to be genotoxic in most available studies, and it is possible that it acts as a non-genotoxic carcinogen. The NOAEL in a 12-week oral gavage study in rats was 1 mg/kg body weight per day. A TDI of 0.714 µg/kg of body weight (allowing for 5 days per week dosing) was calculated by applying an uncertainty factor of 1000 (100 for intra- and interspecies variation, and 10 for evidence of possibly non-genotoxic carcinogenicity). No additional factor for the short duration of the study was incorporated. It was considered to be unnecessary because the compound was administered in corn oil in the critical study and available data indicate that the toxicity following administration in water may be an order of magnitude less. The guideline value derived from this TDI, based on 10% allocation to drinking-water, is 2 µg/litre (rounded figure).