Occurrence and ecotoxicological effects of free, conjugated and halogenated steroids of 17α-hydroxypregnanolone and pregnanediol in Swiss wastewater and surface water


Apart from estrogens, the occurrence and ecotoxicity of steroids in the aquatic environment is poorly known. Here we analyzed 33 steroids, including estrogens, androgens, progestins, and glucocorticoids in hospital wastewaters, river water and in municipal wastewater treatment plant (WTP) influents and effluents at different sites in Switzerland. In addition, wastewater from different treatment steps of two WTPs with advanced treatment, such as ozonation or pulverized activated carbon, were analyzed to study the steroid’s behavior during treatment. Considerable levels of different steroids occurred in hospital and raw municipal wastewater but they were low (lower than 1 ng/L) or below detection level in effluents of WTPs and river water. In WTP influents estrogens (estrone, 17β-estradiol, estriol), androgens (androstenedione, androsterone, trans-androsterone, testosterone), progestins and metabolites (medroxyprogesterone acetate, megestrol acetate, mifepristone, pregnanediol, 17α-hydroxypregnanolone, 17α-hydroxyprogesterone, and 21α-hydroxyprogesterone) were detected and removed effectively during biological treatment. Ozonation further removed the steroids. Exposure of zebrafish embryos demonstrated negligible effects of pregnanediol and 17α-hydroxypregnenolone, while mixtures that mimic wastewater and river water composition affected embryo development and led to alteration of steroidogenesis gene transcripts at ng/L concentrations. Although steroid concentrations are low in Swiss rivers, the possibility of additive effects may be of concern.