Toxicology and carcinogenesis studies of HC Blue No. 2 (approximately 98% pure), a semipermanent hair dye, were conducted by administering the test chemical in feed for 103 weeks to groups of 50 F344/N rats of each sex and for 104 weeks to groups of 50 B6C3F 1 mice of each sex. The dietary concentrations used were 0, 5,000, or 10,000 ppm for male rats and male mice and 0, 10,000, or 20,000 ppm for female rats and female mice. These concentrations were selected on the basis of results from single-administration gavage and 14-day and 13-week feed studies. For the 2-year studies, the average daily doses were approximately 195 and 390 mg/kg in male rats, 465 and 1,000 mg/kg in female rats, 1,320 and 2,240 mg/kg in male mice, and 2,330 and 5,600 mg/kg in female mice.
The survival of high dose male rats and male mice was better than that for controls, and the survival of dosed female rats was comparable to that of the controls. The survival of high dose female mice was reduced (P<0.05) relative to that of controls (control, 35/50; low dose, 27/50; high dose 19/50); this reduced survival was attributed to a reproductive tract infection. Final mean body weights relative to those of controls were depressed less than 10% in dosed male rats, whereas depressions of 13% and 22% were observed in the low dose and high dose groups of female rats. Final mean body weights for dosed male mice were within 5% of control values, but final mean body weights for dosed females were 15% (low dose) and 22% (high dose) lower than that of controls.
A dose-related increase in the incidence of hyperostosis of the skull was detected in rats (male, 5/50, 8/50, 25/49; female, 2/50, 19/50, 49/50) and in 1/49 high dose male and 4/50 high dose female mice. Mixed mesenchymal neoplasms of the kidney were detected in 2/50 high dose female rats; none was observed in any other group of female or male rats. This tumor is considered uncommon and has not been found in 1,863 historical control female F344/N rats. A negative trend in fibroadenomas of the mammary gland was seen in female rats (20/50, 10/50, 4/50).
A marginal (P=0.05) positive trend occurred in the incidence of lymphomas in male mice (1/50; 5/48; 8/49); the incidences in the dosed groups were not significantly greater than that in the controls when survival differences were taken into account.
HC Blue No. 2 was mutagenic for strains TA97 and TA98 but not for strains TA100 or TA1535 of Salmonella typhimurium in the presence or absence of Aroclor 1254-induced male Sprague-Dawley rat or Syrian hamster liver S9. HC Blue No. 2 was mutagenic in the mouse lymphoma L5178Y/TK+/- assay in the presence of Aroclor 1254-induced male F344/N rat liver S9.
An audit of the experimental data was conducted for these carcinogenic studies on HC Blue No. 2. No data discrepancies were found that influenced the final interpretations.
Under the conditions of these studies, there was no evidence of carcinogenicity in male and female F344/N rats or in male and female B6C3F 1 mice receiving HC Blue No. 2 in the diet at concentrations of 0.5% and 1.0% for males and 1.0% and 2.0% for females for 2 years. HC Blue No. 2 administration caused a dose-related increase in the incidence of hyperostosis of the skull in male and female rats.