Multigeneration reproduction and carcinogenicity studies in Sprague-Dawley rats exposed topically to oxidative hair-colouring formulations containing p- phenylenediamine and other aromatic amines

Abstract

Two-generation reproduction and chronic toxicity-carcinogenicity studies were conducted in Sprague-Dawley rats receiving topical applications of six oxidative hair-colouring formulations. These formulations were prepared as prototypes of permanent hair colourings using the base ingredients and primary intermediates and couplers most often used in this kind of product. Among the dyes included in the various formulations were p-phenylenediamine, p-toluenediamine, p-aminophenol, resorcinol, m-aminophenol, 1-naphthol, 2-amino-4-nitrophenol, 4-chlororesorcinol, p-aminodiphenylamine hydrochloride and N-methyl- p-aminophenol sulphate. The dye solutions were mixed with an equal volume of 6% hydrogen peroxide prior to application. In the reproduction study the samples were applied topically twice weekly throughout the growth, mating, gestation and lactation phases of the F 0 parents to the weaning of the F 1a and F 2b litters. Fertility, gestation and foetal viability indices and body weights were evaluated for the six treatment groups and these were compared with the values for the three concurrent control groups. Weanlings selected from the F 1a litters were the subjects for the lifetime carcinogenesis study. For 24 months they received twice-weekly topical applications of the same dyes as were administered to their parents. Clinical chemistry, haematological and urinalysis studies were performed at months 3, 12, 18 and 24, and five animals/sex/group were killed at month 12 and autopsied for histological examination of the rat tissues. All animals in the chronic study were evaluated for incidence of neoplastic and non-neoplastic lesions. In the reproduction phase the application of hair dyes had no adverse effect on the fertility of the males or females, or on gestation, lactation and weaning indices. The average number weaned per litter and the mean body weights of the weanlings were comparable among the treated and control groups. No treatment-related gross lesions were observed in any animals necropsied at month 12 or at study termination, or in any rats that died during the course of the carcinogenicity study. Comparison of the tumour incidences among the six treated and three control groups showed some significant variations among those tumours occurring most frequently in this strain of rats, and pituitary adenomas were also increased significantly ( P < 0.05) in the females of one of the treated groups. The incidence of this tumour is known to be high and variable in untreated female Sprague-Dawley rats. The fact that no pituitary carcinomas occurred in this group suggests that the distribution of these tumours was not related to the experimental treatments. None of the increases of pituitary tumours reported in this study were found to be consistently significant using P < 0.01; the value deemed necessary by statisticians at the National Toxicology Program to avoid false positive results. On the basis of the results of the studies reported here we conclude that the frequent topical application of oxidative hair dyes containing p-phenylenediamine and other commonly used intermediates and couplers has no adverse effects on reproduction and it does not increase the risk of developing cancer.