National Toxicology Program technical report series
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Natl Toxicol Program Tech Rep Ser · Jun 1991
NTP Toxicology and Carcinogenesis Studies of 3,3'-Dimethylbenzidine Dihydrochloride (CAS No. 612-82-8) in F344/N Rats (Drinking Water Studies).
3,3'-Dimethylbenzidine dihydrochloride is one of five chemicals being evaluated in 2-year carcinogenicity and toxicity studies as part of the NTP's Benzidine Dye Initiative. This Initiative was designed to evaluate representative benzidine congeners, benzidine congener-derived dyes, and benzidine-derived dyes. 3,3'-Dimethylbenzidine dihydrochloride was nominated for study because of the potential for human exposure during production of bisazobiphenyl dyes and because benzidine, a structurally related chemical, is a known human carcinogen. Toxicology and carcinogenesis studies were conducted by administering 3,3'-dimethylbenzidine dihydrochloride (approximately 99% pure) in drinking water to groups of F344/N rats of each sex for 14 days, 13 weeks, or 9 or 14 months. ⋯ There was clear evidence of carcinogenic activity for female F344/N rats, as indicated by benign and malignant neoplasms of the skin, Zymbal's gland, clitoral gland, liver, oral cavity, small and large intestine, mammary gland, and lung. Increased incidences of neoplasms of the brain and mononuclear cell leukemia may have been related to chemical administration. Synonyms: o-tolidine dihydrochloride; 3,3'-dimethylbiphenyl-4,4'-diamine dihydrochloride; 3,3'-dimethylbiphenyl-4,4'-biphenyldiamine dihydrochloride; 4,4'-diamino-3,3'-dimethylbiphenyl dihydrochloride