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

1,1,1-TRICHLOROETHANE
(Group 3)

For definition of Groups, see Preamble Evaluation.

VOL.: 71 (1999) (p. 881)

CAS No.: 71-55-6

5. Summary of Data Reported and Evaluation

5.1 Exposure data

1,1,1-Trichloroethane is a solvent. It has been detected in waste-, ground, drinking- and ambient water as well as in ambient and urban air.

5.2 Human carcinogenicity data

An increased risk for central nervous system and multiple myeloma was reported from a cohort study of workers exposed to 1,1,1-trichloroethane in Finland. These findings were not confirmed by two case–control studies carried out in the United States and Canada, while an increased risk for cancer of the lung and kidney was shown in the Canadian study.

5.3 Animal carcinogenicity data

1,1,1-Trichloroethane was tested for carcinogenicity by oral administration in rats in two experiments and in mice in one experiment. Although leukaemia was seen in both sexes of rats in one study and a few liver tumours occurred in male mice, the results of these studies were considered to be inadequate for evaluation. 1,1,1-Trichloroethane was tested by inhalation in rats in two experiments and in mice in one experiment. No chemically related increase in tumour incidence was observed in either rats or mice in one adequate study. Another inhalation study was considered to be inadequate.

In a multistage study for g-glutamyltranspeptidase (g-GT)-positive foci in the liver of male rats, neither single administration of 1,1,1-trichloroethane by gavage after a two-thirds partial hepatectomy followed by treatment with phenobarbital (initiation study) nor repeated administration of 1,1,1-trichloroethane by gavage after a two-thirds partial hepatectomy and initiation with N-nitrosodiethylamine (promotion study) increased the number of g-GT-positive foci.

5.4 Other relevant data

Absorption of 1,1,1-trichloroethane vapour is mainly through the respiratory tract. It is rapidly eliminated from blood. Metabolism plays a minor role in this process, more than 90% being eliminated unchanged, both in exposed people and rodents. The main metabolites are trichloroethanol, trichloroacetic acid and carbon dioxide.

1,1,1-Trichloroethane is neurotoxic and hepatotoxic, following exceptionally high exposure concentrations of people and also in rodents. No structural damage has been reported in reproductive toxicity studies in rats and mice, but delayed development, particularly of neurological attributes, has been reported in one study with mice.

1,1,1-Trichloroethane covalently bound to DNA, RNA and protein in mice and rats but did not induce micronuclei or abnormal sperm head morphology in mice in vivo. It induced chromosomal aberrations and cell transformation in mammalian cell cultures and it showed inconclusive evidence of sister chromatid exchange induction. It did not induce unscheduled DNA synthesis or gene mutation in mammalian cells in vitro. 1,1,1-Trichloroethane did not cause mutation in plants or sex-linked mutation in Drosophila. It did not induce DNA damage, gene conversion, mutation or aneuploidy in yeast or genetic crossing-over or aneuploidy in fungi, but it was mutagenic to some bacterial strains.

5.5 Evaluation

There is inadequate evidence for the carcinogenicity of 1,1,1-trichloroethane in humans.

There is inadequate evidence for the carcinogenicity of 1,1,1-trichloroethane in experimental animals.

Overall evaluation

1,1,1-Trichloroethane is not classifiable as to its carcinogenicity to humans (Group 3).

For definition of the italicized terms, see Preamble Evaluation.

Previous evaluations: Vol. 20 (1979); Suppl. 7 (1987)

Synonyms


Last updated: 13 April 1999





















    See Also:
       Toxicological Abbreviations
       Trichloroethane, 1,1,1- (EHC 136, 1992)
       Trichloroethane, 1,1,1- (WHO Food Additives Series 16)
       Trichloroethane, 1,1,1- (PIM 540)