LAUSR

Triclosan has been shown to have endocrine‐disrupting effects in aquatic organisms. In 2016, the US Food and Drug Administration banned the use of triclosan in consumer soaps. Before the ban, triclosan was reported at low concentrations in the aquatic environment, although the effect of triclosan on reproduction in teleost fish species is yet to be clarified. Here we investigated the effects of triclosan on embryo development and reproduction, and during the early life stage, in Japanese medaka (Oryzias latipes) by using Organisation for Economic Co‐operation and Development tests 229, 212 and 210, with minor modifications. In adult medaka, exposure to 345.7 μg l–1 suppressed fecundity and increased mortality but had no effect on fertility. Exposure to 174.1 or 345.7 μg l–1 increased liver vitellogenin concentration in females but decreased liver vitellogenin concentration in males. With triclosan exposure, mortality was increased dose dependently during the embryonic and early larval stages, and a particularly steep increase in mortality was observed soon after hatching. The lowest observed effect concentrations of triclosan in Japanese medaka obtained in the present study (mortality [embryonic and larval stages, 276.3 μg l–1; early life stage, 134.4 μg l–1; adult stage, 174.1 μg l–1], growth [134.4 μg l–1], vitellogenin [174.1 μg l–1], fecundity [345.7 μg l–1] and fertility [>345.7 μg l–1]) were at least 55 times (compared with the USA) and up to 13 400 times (compared with Germany) greater than the detected triclosan levels in the aquatic environment. These results suggest that triclosan may not be affecting fish populations in the aquatic environment.