Carcinogenicity of dimethoate.

Studies on the carcinogenicity of the insecticide dimethoate in animals were reviewed. Examination of histological sections showed that dimethoate is highly carcinogenic in Osborne-Mendel rats. Neoplasms at all sites, as well as malignant neoplasms, were increased in both low and high doses of dimethoate-treated male rats in the National Cancer Institute study. The malignant neoplasms were both carcinomas and sarcomas. Neoplasms of the endocrine organs, particularly carcinomas, were increased in male and female rats given dimethoate. These carcinomas were observed in the adrenal, thyroid, and pituitary glands. Neoplasms were also increased in the liver of male and female rats and in the reproductive organs of female rats given dimethoate. Male and female rats treated with dimethoate developed monocytic leukemia. There also were toxic changes in rats. Male rats had atrophy of the testes, chronic renal disease, parathyroid hyperplasia, and polyarteritis. Wistar male and female rats given dimethoate by gavage or intramuscularly developed a significant increase in malignant neoplasms, mainly sarcomas, and granulocytic leukemia. AB male and female mice also had an increased incidence of malignant neoplasms and granulocytic leukemia after dermal applications of dimethoate.