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

(Group 3)

For definition of Groups, see Preamble Evaluation.

VOL.: 71 (1999) (p. 721)

CAS No.: 74-83-9
Chem. Abstr. Name: Bromomethane

5. Summary of Data Reported and Evaluation

5.1 Exposure data

Exposure to methyl bromide may occur in its production, in pest control and in fumigation of soil. Methyl bromide is naturally produced in oceans. It is commonly detected in ambient air and at low levels in water.

5.2 Human carcinogenicity data

One cohort study of workers at three chemical manufacturing plants included a subgroup with potential exposure to methyl bromide, among whom there were two deaths from testicular cancer (0.11 expected).

5.3 Animal carcinogenicity data

Methyl bromide was tested by oral administration in rats and by inhalation in mice and rats. In one 90-day study by oral administration in rats, methyl bromide was reported to produce squamous-cell carcinomas of the forestomach. In a second, 25-week study designed to investigate further the findings of the previous study, early hyperplastic lesions of the forestomach developed after 25 weeks of continuous treatment by gavage. In two inhalation studies in mice, no significant increase in the incidence of tumours was observed. In one inhalation study in rats, an increase in the incidence of adenomas of the pituitary gland was observed in high-dose male rats. In another study in rats, no increase in tumour incidence was observed.

5.4 Other relevant data

Methyl bromide is metabolized by glutathione conjugation and excreted as carbon dioxide. In animal studies, it caused toxicity and irritation and organ toxicity in many organs. It binds covalently to DNA in vitro and also in various organs in the rat in vivo. Methyl bromide is mutagenic in bacteria; it induces gene mutations and sister chromatid exchanges in vitro in mammalian cells. Methyl bromide gave positive results for several genetic activity end-points in Drosophila.

5.5 Evaluation

There is inadequate evidence in humans for the carcinogenicity of methyl bromide.

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

Overall evaluation

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

For definition of the italicized terms, see Preamble Evaluation.

Previous evaluations: Vol. 41 (1986); Suppl. 7 (1987)


Last updated: 13 April 1999

    See Also:
       Toxicological Abbreviations
       Methyl Bromide (EHC 166, 1995)
       Methyl bromide (ICSC)
       Methyl bromide (PIM 340)
       Methyl bromide (FAO Meeting Report PL/1965/10/2)
       Methyl bromide (FAO/PL:CP/15)
       Methyl bromide (FAO/PL:1967/M/11/1)
       Methyl bromide (FAO/PL:1968/M/9/1)
       Methyl bromide (WHO Pesticide Residues Series 1)