Early-life-stage toxicity tests of zinc pyrithione (Zpt) and commercial sha
mpoos containing or not containing Zpt were performed on zebra fish and Jap
anese Medaka. The results showed that Zpt induced significant teratogenic e
ffects on larvae of both species of fish. The two antidandruff shampoos con
taining Zpt induced the same teratogenic effects as Zpt, The calculated EC5
0 concentrations of Zpt for each of the shampoos were consistent with the E
C50 for Zpt concentrate. Furthermore, 23 other shampoos not containing Zpt
showed no teratogenic effects, These results strongly suggest that Zpt is t
he main factor in the antidandruff shampoos. (C) 1999 Academic Press.