Malathion and its
oxygen analogue,
malaoxon, are carcinogenic in Osborne-Mendel and Fischer-344 rats. Benign and
malignant neoplasms at all sites were increased in Osborne-Mendel and Fischer-344 male and female rats ingesting
malathion. Both Osborne-Mendel and Fischer-344 male rats were more susceptible than the female rats. The organ sites were not the same for Fischer-344 and Osborne-Mendel rats. Osborne-Mendel rats developed
neoplasms of the endocrine organs, brain, and liver. Fischer-344 rats had
neoplasms of the adrenal medulla, organs with squamous cells, lung, and hematopoietic system. Fischer-344 male rats given
malathion were more susceptible to
chronic renal disease, parathyroid
hyperplasia, metastatic calcification, and
atrophy of the testes than were Osborne-Mendel male rats. They also had
ulcers of the forestomach.
Chronic renal disease and
atrophy of the testes affected the health of the animals and interfered with the development of
neoplasms.
Malathion increased the incidence of
neoplasms of the liver in B6C3F1 male mice. Male mice also had
atrophy of the testes. Benign and
malignant neoplasms at all sites, and in the endocrine organs, were increased in Fischer-344 male and female rats ingesting
malaoxon.
Neoplasms were present in the adrenal medulla, organs with squamous cells, liver, and hematopoietic system. Both male and female Fischer-344 rats receiving
malaoxon had
chronic renal disease and the male rats had parathyroid
hyperplasia and metastatic calcification.