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

(Group 2B)

For definition of Groups, see Preamble Evaluation.

VOL.: 53 (1991) (p. 267)

CAS No.: 62-73-7
Chem. Abstr. Name: Phosphoric acid, 2,2-Dichloroethenyl dimethyl ester

5. Summary of Data Reported and Evaluation

5.1 Exposure data

Dichlorvos has been used widely as an insecticide since 1961 to control internal and external parasites in livestock and domestic animals, to control insects in houses, and in crop protection.

Dichlorvos has been formulated for use as dusts, granules, pellets/tablets, impregnated resin strips and concentrates.

Household and public health uses represent the main sources of human exposure to dichlorvos. Exposure may also occur during its production and application.

5.2 Carcinogenicity in humans

One case-control study of leukaemia in the USA found an association with use of dichlorvos on animals; there were few exposed subjects, and they had potential exposure to many pesticides.

5.3 Carcinogenicity in experimental animals

Dichlorvos was tested for carcinogenicity by oral administration in two experiments in mice and in three experiments in rats. A few rare oesophageal squamous-cell tumours were found in mice treated with dichlorvos in the diet. A dose-related increase in the incidence of squamous-cell tumours (mainly papillomas) was noted in the forestomachs of mice that received dichlorvos in corn oil by gavage. In rats that received dichlorvos in water by gavage, a few squamous-cell papillomas of the forestomach were seen. In rats that received dichlorvos in corn oil by gavage, a dose-related increase in the incidence of mononuclear-cell leukaemia and an increased incidence of pancreatic acinar-cell adenomas were observed in males.

5.4 Other relevant data

A variety of studies in several species did not demonstrate developmental toxicity due to dichlorvos.

In vitro, dichlorvos phosphorylates esterases to a greater extent than it methylates nucleophiles; the likelihood of DNA methylation in vivo is extremely small.

Immunosuppression has been noted after short-term administration of high doses of dichlorvos which are associated with profound cholinergic hyperstimulation.

No data were available on the genetic and related effects of dichlorvos in humans.

Dichlorvos was not shown to have genetic activity in various assays in mammals in vivo. It induced gene mutation and chromosomal damage in cultured mammalian cells and in insects, plants, fungi, yeast and bacteria.

5.5 Evaluation

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

There is sufficient evidence in experimental animals for the carcinogenicity of dichlorvos.

Overall evaluation

Dichlorvos is possibly carcinogenic to humans (Group 2B).

For definition of the italicized terms, see Preamble Evaluation.

Previous evaluations: Vol. 20 (1979) (p. 97); Suppl. 7 (1987) (p. 62)

Synonyms for Dichlorvos

Last updated: 21 November 1997

    See Also:
       Toxicological Abbreviations
       Dichlorvos (EHC 79, 1988)
       Dichlorvos (HSG 18, 1988)
       Dichlorvos (ICSC)
       Dichlorvos (FAO Meeting Report PL/1965/10/1)
       Dichlorvos (FAO/PL:CP/15)
       Dichlorvos (FAO/PL:1967/M/11/1)
       Dichlorvos (FAO/PL:1969/M/17/1)
       Dichlorvos (AGP:1970/M/12/1)
       Dichlorvos (WHO Pesticide Residues Series 4)
       Dichlorvos (Pesticide residues in food: 1977 evaluations)
       Dichlorvos (Pesticide residues in food: 1993 evaluations Part II Toxicology)