Carcinogenicity of picloram.

Two studies of the carcinogenicity of the herbicide picloram in animals were reviewed. Examination of histological sections showed that picloram is highly carcinogenic in rats and mice. Neoplasms at all sites, including malignant neoplasms, were increased in male and female rats given both low and high doses of picloram in the National Cancer Institute rat study. The malignant neoplasms were both carcinomas and sarcomas. Neoplasms of the endocrine organs, particularly carcinomas, were increased in male and female rats given picloram. 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 picloram. Male and female mice exposed to picloram developed neoplasms of the spleen in the National Cancer Institute mouse study. There were also toxic changes in rats and mice. Male rats had chronic renal disease, parathyroid hyperplasia, and polyarteritis. There was atrophy of the testes in both male rats and mice given picloram.