Occurrence and Ecotoxicological Effects of Free, Conjugated, and Halogenated Steroids Including 17α-Hydroxypregnanolone and Pregnanediol in Swiss Wastewater and Surface Water

Apart from estrogens, the occurrence and ecotoxicity of steroids in aquatic environments is poorly known. Here, we analyzed 33 steroids, including estrogens, androgens, progestins, and glucocorticoids, in hospital wastewaters, river water, and 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 zonation 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 the detection level in effluents of WTPs and river water. In WTP influents, estrogens (estrone, 17 beta-estradiol, and estriol), androgens (aridrostenedione, androsterone, trans-androsterone, and testosterone), progestins and metabolites (progesterone, medroxyprogesterone acetate, megestrol acetate, mifepristone, pregnanediol, 17 alpha-hydroxypregnanolone, 17 alpha-hydroxyprogesterone, and 21 alpha-hydroxyprogesterone) were detected and removed effectively during biological treatment. Ozonation further removed the steroids. Exposure of zebrafish embryos demonstrated negligible effects of pregnanediol and 17 alpha-hydroxypregnanolone, while mixtures that mimic wastewater and river water composition affected embryo development and led to the alteration of steroidogenesis gene transcripts at nanogram per liter concentrations. Although steroid concentrations are low in Swiss rivers, the possibility of additive effects may be of concern.