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

(Group 3)

For definition of Groups, see Preamble Evaluation.

Supplement 7: (1987) (p. 149)

CAS No.: 75-45-6

A. Evidence for carcinogenicity to humans (inadequate)

A small study of 539 refrigeration workers exposed to a mixture of chlorofluorocarbons, including chlorodifluoromethane, for at least six months with up to 30 years' follow up was uninformative with regard to the carcinogenic hazard of this chemical (6 deaths due to cancer, 5.7 expected; 2 deaths from lung cancer, 1.0 expected) [ref: 1].

B. Evidence for carcinogenicity to animals (limited)

Chlorodifluoromethane was tested for carcinogenicity in rats by oral administration and in mice and rats by inhalation. Oral administration to rats yielded no increase in tumour incidence in one study. A study by inhalation in mice gave inconclusive results for males and negative results for females. One study by inhalation in rats was inadequate, while in another, males exposed to the highest concentration had a marginal increase in the incidence of subcutaneous fibrosarcomas and Zymbal-gland tumours and negative results were obtained for female rats [ref: 1].

C. Other relevant data

No data were available on the genetic and related effects of chlorodifluoromethane in humans. Chlorodifluoromethane did not induce dominant lethal mutations in rats or chromosomal aberrations in bone-marrow cells of mice treated in vivo. It did not induce unscheduled DNA synthesis in human cells in vitro or mutation in cultured Chinese hamster V79 cells. It did not induce mutation or mitotic gene conversion in yeast, either after direct exposure or in a host-mediated assay. It was mutagenic to plants and bacteria [ref: 2].

Overall evaluation

Chlorodifluoromethane 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)

Also see previous evaluation: Vol. 41 (1986)


1. IARC Monographs, 41, 237-252, 1986

2. IARC Monographs, Suppl. 6, 150-151, 1987


Last updated: 13 April 1999

    See Also:
       Toxicological Abbreviations
       Chlorodifluoromethane (ICSC)
       Chlorodifluoromethane  (IARC Summary & Evaluation, Volume 41, 1986)
       Chlorodifluoromethane  (IARC Summary & Evaluation, Volume 71, 1999)