Biological responses in fish exposed to municipal wastewater treatment plant effluent <i>in situ</i>

Abstract Effluents from municipal wastewater treatment plants (MWTPs) are complex mixtures of chemicals including endocrine-disrupting compounds (EDCs) and 17?-ethynylestradiol (EE2). The objective this study was to evaluate selected responses two fish species, in different years, exposed situ MWTP effluent. Biological markers exposure (plasma vitellogenin (VTG) antioxidant enzymes) were measured species male fish, rainbow trout (Oncorhynchus mykiss) fathead minnow (Pimephales promelas), caged at sites associated with outfall. estrogenicity the final effluent 2010 determined be 17.0 + 0.4 ng/L estrogen equivalents (EEQ) reduced 7.5 2.9 EEQ after infrastructure upgrades. Pharmaceuticals personal care products surface water both years confirmed exposures each downstream site. Despite presence estrogenic effluent, no effluent-caged demonstrated plasma VTG induction. Minnows that received an intraperitoneal injection 5 mg/g EE2 showed induction field sites. In 2012, liver somatic index (LSI) increased exposure, as did changes enzymes, reactive oxygen (ROS) activity. Multiple biological mechanisms modified by multiple endpoints needed assess risk.