Fish bile used to detect estrogenic substances in treated sewage water

Endocrine disrupting effects on fish associated with sewage treatment effluents have been demonstrated in several studies. To investigate if the effluents from two modern Swedish sewage treatment plants contained estrogenic substances, juvenile rainbow trout were exposed to sewage water before and after the last treatment step which is a sand filter. As a biomarker for estrogenic effect, vitellogenin was analysed in the blood plasma of the exposed fish. To identify substances possibly responsible for the effect, bile fluid from the exposed fish were analysed with GC/MS. Elevated levels of vitellogenin were only seen in the fish exposed at one of the sewage treatment plants, the one with shorter residence time in the biological treatment steps, which suggests that the residence time is of importance for the ability to reduce the amount of estrogenic substances in the sewage water. The highest elevation of vitellogenin was seen in the fish exposed to water before the sand filter, which indicates that the sand filter contributes to further reduction of estrogenic substances in the sewage water. In bile from the same group of fish, considerably higher concentrations of estrone, bisphenol A and 4-nonylphenol (4.0 Ag/g bile, 23 Ag/g bile and 24 Ag/g bile, respectively) were observed compared to bile from control fish (b0.04 Ag/g bile, 0.21 Ag/g bile, and 3.5 Ag/g bile, respectively). The more potent steroidal estrogens were suggested to be major contributors to the observed estrogenic effect, although xenoestrogens were detected at higher concentrations in the bile fluid.