Toxicology and carcinogenesis studies of HC Blue No. 1 (97% pure), a semipermanent hair dye, were conducted by administering the test chemical in feed for 103 weeks to groups of 50 F344/N rats and 50 B6C3F1 mice of each sex. The dietary concentrations used were 0, 1,500, or 3,000 ppm for rats and male mice and 0, 3,000, or 6,000 ppm for female mice. These concentrations were selected on the basis of results from single-administration gavage studies and 14-day and 13-week feed studies.
The survival of male and female rats and male mice was not affected by administration of HC Blue No. 1. Survival of high dose female mice was reduced (P<0.05); the early deaths in this group are believed to have been caused by hepatocellular carcinomas. Body weights of high dose rats and dosed mice were lower than those of the respective control groups; female rats and mice were more affected than were males.
Administration of HC Blue No. 1 produced significant positive trends in the incidences of male rats with hepatocellular neoplastic nodules/carcinomas (neoplastic nodules: control, 0/49; low dose, 0/50; high dose, 3/50; neoplastic nodules/carcinomas: 1/49; 0/50; 6/50). In male and female mice, both doses of HC Blue No. 1 increased the incidences of hepatocellular carcinoma (male: 11/50; 20/50; 30/50; female: 1/50; 24/48; 47/49) and the low doses increased the incidences of hepatocellular adenomas (male: 4/50; 17/50; 10/50; female: 2/50; 11/48; 4/49).
HC Blue No. 1 produced dose-related increases in the incidences of proliferative lesions of the lungs (adenomatous hyperplasia and alveolar/bronchiolar adenomas or carcinomas) in female rats (hyperplasia: 2/50; 5/49; 8/50; adenoma/carcinoma: 1/50; 3/49; 7/50).
In male mice, HC Blue No. 1 at the 6,000-ppm dose increased the incidences of thyroid gland follicular cell hyperplasia and adenomas (hyperplasia: 3/47; 7/49; 14/50; adenoma: 0/47; 0/49; 5/50).
HC Blue No. 1 was mutagenic in strains TA97, TA98, and TA100 of Salmonella typhimurium in the presence or absence of Aroclor-induced male Sprague-Dawley rat or Syrian hamster liver S9; HC Blue No. 1 was negative in strain TA1535. HC Blue No. 1 was mutagenic in the absence of activation in the L5178Y/TK+/- mouse lymphoma assay and induced unscheduled DNA synthesis in rat hepatocytes in vitro.
An audit of the experimental data was conducted for these carcinogenesis studies on HC Blue No. 1. No data discrepancies were found that influenced the final interpretations.
Under the conditions of these feed studies, there was equivocal evidence of carcinogenicity in male F344/N rats, since HC Blue No. 1 caused a marginal increase in the incidence of hepatocellular neoplastic nodules/carcinomas. For female F344/N rats, there was some evidence of carcinogenicity in that HC Blue No. 1 induced increased incidences of alveolar/bronchiolar neoplasms. There was clear evidence of carcinogenicity of HC Blue No. 1 for male and female B6C3F1 mice as shown by increased incidences of hepatocellular carcinomas. The incidences of follicular cell adenomas of the thyroid gland were also increased in male mice receiving HC Blue No. 1.