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


VOL.: 30 (1983) (p. 131)

5. Summary of Data Reported and Evaluation

5.1 Experimental data

Methyl parathion was tested for carcinogenicity in mice and rats by administration in the diet. No evidence of carcinogenicity was found.

Methyl parathion, administered intraperitoneally at maternally lethal doses, was teratogenic to mice. In rats, decreased viability and body weight were seen in the progeny of treated animals, but no teratogenicity was observed.

Methyl parathion was weakly or not mutagenic in bacterial systems and in Drosophila melanogaster, but it was mutagenic in yeasts. In mammalian cells, sister chromatid exchange and presumed gene mutations were induced, but neither chromosomal aberration nor unscheduled DNA synthesis was elicited. Chromosomal aberrations and dominant lethal mutations were not increased in mice treated with methyl parathion. There is sufficient evidence that methyl parathion is mutagenic in a variety of cellular systems, but insufficient evidence that it is mutagenic in mammals.

5.2 Human data

Methyl parathion was introduced in 1949. Its production, formulation and use as an insecticide on cotton and other crops are potential sources of exposure, both of workers and of the general population.

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

No case report or epidemiological study of the carcinogenicity of methyl parathion 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 methyl parathion is carcinogenic to experimental animals. No data on humans were available.

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

Subsequent evaluation: Suppl. 7 (1987)

Last updated: 16 April 1998

    See Also:
       Toxicological Abbreviations
       Methyl parathion (EHC 145, 1992)
       Methyl parathion (HSG 75, 1992)
       Methyl parathion (ICSC)
       Methyl Parathion (FAO Meeting Report PL/1965/10/1)
       Methyl Parathion  (IARC Summary & Evaluation, Supplement7, 1987)