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


VOL.: 30 (1983) (p. 103)

CAS No.: 121-75-5
Chem. Abstr. Name: Butanedioic acid,[(dimethoxyphosphinothioyl)thio]-, diethyl ester

5. Summary of Data Reported and Evaluation

5.1 Experimental data

Malathion and its metabolite malaoxon were tested for carcinogenicity in mice and rats by administration in the diet. No evidence of carcinogenicity was found.

There was no evidence of teratogenicity or embryotoxicity in rats given maternally tolerated doses of malathion during pregnancy. In animals fed very high doses for two generations, malathion had no effect on reproduction other than to decrease survival in the first generation and to reduce growth in the second generation of rats.

Malathion was not mutagenic in most studies of bacteria or in two studies of yeast. No mutagenic action was observed in Drosophila melanogaster. Malathion increased sister chromatid exchange frequency in cultured mammalian cells but did not induce unscheduled DNA synthesis. Chromosomal aberrations were increased in certain types of cultured mammalian cells and in mice treated in vivo with malathion. Dominant lethal tests in mice were reported to be negative. There is thus limited evidence for the mutagenicity of malathion.

5.2 Human data

Malathion was introduced in 1950. Its production, formulation and widespread use as an insecticide in a variety of agricultural, vector control and household applications are potential sources of exposure, both of workers and of the general population.

No data were available to evaluate the teratogenic effects of malathion in humans. The available data were insufficient to evaluate the chromosomal effects of malathion in humans.

No case report or epidemiological study of the carcinogenicity of malathion alone was available to the Working Group. (See, however, the section 'Cancer Epidemiology of Pesticide Manufacturers, Formulators and Users', in this volume.)

5.3 Evaluation

The available data do not provide evidence that malathion or its metabolite malaoxon is carcinogenic to experimental animals. No data on humans were available.

The available data provide no evidence that malathion is likely to present a carcinogenic risk to humans.

Subsequent evaluation: Suppl. 7 (1987) (p. 62: Group 3)


Last updated: 16 April 1998

    See Also:
       Toxicological Abbreviations
       Malathion (ICSC)
       Malathion (FAO Meeting Report PL/1965/10/1)
       Malathion (FAO/PL:CP/15)
       Malathion (FAO/PL:1967/M/11/1)
       Malathion (JMPR Evaluations 2003 Part II Toxicological)
       Malathion (FAO/PL:1968/M/9/1)
       Malathion (FAO/PL:1969/M/17/1)
       Malathion (AGP:1970/M/12/1)
       Malathion (WHO Pesticide Residues Series 3)
       Malathion (WHO Pesticide Residues Series 5)
       Malathion (Pesticide residues in food: 1977 evaluations)
       Malathion (Pesticide residues in food: 1984 evaluations)
       Malathion (Pesticide residues in food: 1997 evaluations Part II Toxicological & Environmental)