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International Agency for Research on Cancer (IARC) - Summaries & Evaluations


VOL.: 20 (1979) (p. 401)

5. Summary of Data Reported and Evaluation

5.1 Experimental data

Chloroform was tested in three experiments in mice and in one in rats by oral administration. It produced hepatomas and hepatocellular carcinomas in mice, malignant kidney tumours in male rats and tumours of the thyroid in female rats. Chloroform was also tested in one experiment by subcutaneous injection and in one by intraperitoneal injection in mice: these experiments were considered to be inadequate.

Chloroform is foetotoxic; it was not mutagenic in the bacterial systems tested.

N.B. - Subsequent to the meeting of the Working Group, the Secretariat became aware of the results of 3 studies, in which mice, rats and dogs were administered toothpaste containing chloroform by gavage or in gelatin capsules on 6 days per week for 80 weeks (mice and rats) or 71/2 years (dogs), followed by observation periods ranging from 15-24 weeks. No treatment-related increase in the incidence of tumours was observed in rats receiving 60 mg/kg bw/day chloroform (Palmer et al., 1979) or in dogs receiving 15 or 30 mg/kg bw/day (Heywood et al., 1979). In mice, benign and malignant tumours of the kidney occurred in 8/38 male ICI mice administered 60 mg/kg bw/day chloroform, but no such tumours occurred in females given that dose, or in males and females receiving 17 mg/kg bw/day or in controls. In a second experiment in mice, 7 benign and 2 malignant tumours of the kidney occurred among 49 male CFLP (ICI-redefined) mice given 60 mg/kg bw/day chloroform in toothpaste base compared with 6 benign kidney tumours among 237 male mice given the toothpaste base without chloroform. In a third experiment, groups of C57BL, CBA, CF/1 or ICI male mice received 60 mg/kg bw/day chloroform in toothpaste base or toothpaste base alone; 2 additional groups of male ICI mice received 60 mg/kg bw/day chloroform in arachis oil or arachis oil alone. Two benign and 3 malignant tumours of the kidney occurred among 47 ICI male mice given chloroform in toothpaste base, and 3 benign and 9 malignant tumours of the kidney occurred among 48 ICI male mice given chloroform in arachis oil. One benign tumour of the kidney occurred in each group of respective controls. No kidney tumours occurred in treated C57BL or CBA mice; and no increased incidence of malignant kidney tumours was seen in CF/1 male mice (1/48 treated and 2/45 controls) (Roe et al., 1979).

5.2 Human data

No case reports or epidemiological studies were available to the Working Group.

The past use of chloroform as an anaesthetic and its present use in drugs and cosmetic products, as an insecticidal fumigant and as an industrial solvent indicate that widespread human exposure occurs. This is confirmed by many reports of its presence in air, water and foods.

5.3 Evaluation

There is sufficient evidence that chloroform is carcinogenic in mice and rats. In the absence of adequate data in humans, it is reasonable, for practical purposes, to regard chloroform as if it presented a carcinogenic risk to humans.

For definition of the italicized terms, see Preamble Evaluation.

Previous evaluation: Vol. 1 (1972)

Subsequent evaluations: Suppl. 7 (1987); Vol. 73 (1999)

Last updated:30 September 1999

See Also:
        Chloroform (CHEMINFO)
        Chloroform (EHC 163, 1994)
        Chloroform (IARC Summary & Evaluation, Supplement 7, 1987)
        Chloroform (IARC Summary & Evaluation, Volume 1, 1972)
        Chloroform (ICSC)
        Chloroform (PIM 121)