Developmental evaluation of a potential non-steroidal estrogen: triclosan.

Triclosan is an antibacterial agent commonly used in industry and often detected in waste-water effluent. The potential of triclosan to act as an endocrine disruptor was examined because its chemical structure closely resembles known non-steroidal estrogens (e.g. DES, bisphenol A). Japanese medaka fry (Oryzias latipes) were exposed for 14 days beginning 2 days post-hatch to triclosan (100, 10, 1 micrograms/l), 17-beta estradiol (E2; 1 microgram/l), or a solvent control (ethanol). Two months post-exposure, the phenotypic sex of each adult was assessed visually using sexually dimorphic fin shape and size. The proportion of females in each group was similar for triclosan-exposed animals and solvent-treated controls (ethanol 53%, 1 ppb 58%, 10 ppb 45%, 100 ppb 36%) although E2 treatment did produce 92% female adults. Sexually dimorphic fin traits were quantified to look for potential effects of triclosan and E2 on the development of secondary sexual characters. These results do not support the hypothesis that triclosan is potently estrogenic. However, changes in fin length and non-significant trends in sex ratio suggest triclosan is potentially weakly androgenic.