NTP Toxicology and Carcinogenesis Studies of C.I. Acid Orange 3 (CAS No. 6373-74-6) in F344/N Rats and B6C3F1 Mice (Gavage Studies).

The study investigated the toxicology and carcinogenic potential of C.I. Acid Orange 3, a dye used in semipermanent hair coloring, in F344/N rats and B6C3F1 mice. Over 2 years, rats and mice were administered the dye in varying doses. In rats, particularly females, there was clear evidence of carcinogenic activity, with transitional cell carcinomas of the kidney observed in high-dose female rats. Nonneoplastic kidney lesions were also noted in both species. However, no evidence of carcinogenic activity was found in male rats or in male and female mice. The study concluded that while C.I. Acid Orange 3 showed carcinogenic effects in female rats, it did not exhibit the same in male rats or mice.