National Toxicology Program

TR-199
Bioassay of Selsun® for Possible Carcinogenicity

Chemical Formula: SeS₂·H₂O

A bioassay of Selsun® for possible carcinogenicity was conducted by applying this substance dermally to ICR Swiss mice. Selsun®, an antidandruff shampoo, contains 2.5% selenium sulfide.

Groups of 50 mice of each sex were exposed to 0.05 ml of 25% or 50% Selsun® in distilled water three times a week on a 2-x 3-cm clipped dorsal surface. Vehicle controls consisted of 50 mice of each sex that were clipped and treated with distilled water. Untreated controls consisted of 50 mice of each sex that were only clipped. Surviving mice were killed and necropsied at week 88.

Mean body weights of untreated control, vehicle control, low-dose, and high-dose groups were comparable throughout the bioassay. Amyloidosis was a factor in the deaths of most animals after 1 year. In male mice, alveolar/bronchiolar carcinomas or adenomas occurred witha dose-related trend that was significant (P=0.008). The result of the Fisher exact test comparing the incidence in the high-dose group with that in the vehicle controls is also significant, but the incidence of the high-dose group, when compared with that of the untreated controls, is not significant.

Under the conditions of this bioassay, dermal application of Selsun® was not carcinogenic for ICR Swiss mice. The study was limited, however, by the relatively short lifespan of this strain of mouse.

Report Date: August 1980

Target Organs from 2-year Studies

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