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

(Group 3)

For definition of Groups, see Preamble Evaluation.

VOL.: 52 (1991) (p. 243)

CAS No.: 124-48-1

5. Summary of Data Reported and Evaluation

5.1 Exposure data

Chlorodibromomethane has limited commercial use but is used industrially as a chemical intermediate. It is found in chlorinated drinking-water as a consequence of the reaction between chlorine, added during drinking-water treatment, and natural organic substances in the presence of bromide. The major route of human exposure is via drinking-water. Chlorodibromomethane has been detected in chlorinated drinking-water in many parts of the world; it is not normally present in untreated water. It is a major component of organohalide emissions from marine algae.

5.2 Experimental carcinogenicity data

Chlorodibromomethane was tested for carcinogenicity in two-year studies by oral gavage in male and female B6C3F1 mice and Fischer 344 rats and in a lifetime study in CBA x C57Bl/6 hybrid mice by administration in drinking-water. In B6C3F1 mice, it produced a significant increase in the incidence of hepatocellular neoplasms in females and a marginal increase in males. Chlorodibromomethane did not increase the proportion of rats with tumours at any site relative to that in controls. There was no increase in tumour incidence in CBA x C57Bl/6 hybrid mice given chlorodibromomethane in drinking-water.

5.3 Human carcinogenicity data

No relevant data were available to the Working Group.

5.4 Other relevant data

Chlorodibromomethane was mutagenic to bacteria. In single studies, it induced mitotic recombination, but not mutation, in yeast, chromosomal aberrations in cultured mammalian cells and sister chromatid exchange in cultured human cells. Sister chromatid exchange but not micronuclei were observed in rodents treated in vivo.

5.5 Evaluation

There is inadequate evidence for the carcinogenicity of chlorodibromomethane in humans.

There is limited evidence for the carcinogenicity of chlorodibromomethane in experimental animals.

Overall evaluation

Chlorodibromomethane is not classifiable as to its carcinogenicity to humans (Group 3).

For definition of the italicized terms, see Preamble Evaluation.

Subsequent evaluation: Vol. 71 (1999)


Last updated: 13 April 1999

    See Also:
       Toxicological Abbreviations
       Chlorodibromomethane  (IARC Summary & Evaluation, Volume 71, 1999)