Induction of tumors of the nasal cavity in rats by concurrent feeding of thiram and sodium nitrite

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Abstract
Simultaneous feeding to rats of thiram with sodium nitrate was carried out to assess the possibility of formation of carcinogenic N-nitroso derivatives in vivo. Following the administration of feed containing 500 ppm thiram plus 2000 ppm sodium nitrite for 104 wk, a high incidence of tumors of the nasal cavity was found in both sexes, 18 of 24 males and 15 of 24 females. No nasal cavity tumors were seen in untreated rats, or those given 500 ppm thiram or 2000 ppm sodium nitrite alone. A 20% incidence of papillomas of the forestomach was also seen in rats of both sexes given the combined treatment. The other significant difference in incidence of tumors between the rats given thiram with or without nitrite was a decreased number of animals with monocytic leukemia, which was a common neoplasm in untreated F-344 rats.