Pathway‐based approaches for assessment of real‐time exposure to an estrogenic wastewater treatment plant effluent on fathead minnow reproduction

Jenna E Cavallin, Kathleen M Jensen, Michael D Kahl, Daniel L Villeneuve, Kathy E Lee, Anthony L Schroeder, Joe Mayasich, Evan P Eid, Krysta R Nelson, Rebecca Y Milsk, Brett R Blackwell, Jason P Berninger, Carlie A LaLone, Chad Blanksma, Terri Jicha, Colleen Elonen, Rodney Johnson, Gerald T Ankley

Wastewater treatment plant (WWTP) effluents are known contributors of chemical mixtures into the environment. Of particular concern are endocrine-disrupting compounds, such as estrogens, that can affect hypothalamic-pituitary-gonadal axis function in exposed organisms. The present study examined reproductive effects in fathead minnows exposed for 21 d to a historically estrogenic WWTP effluent. Fathead minnow breeding pairs were held in control water or one of three effluent concentrations (5%, 20%, and 100%) in a novel on-site, flow-through system providing real-time exposure. Molecular and biochemical endpoints representing key events along adverse outcome pathways linking estrogen receptor activation and other molecular initiating events to reproductive impairment were examined. Additionally, chemical analysis of the effluent was used to construct a chemical-gene interaction network to aid in targeted gene expression analyses and identification of potentially impacted biological pathways. Cumulative fecundity was significantly reduced in fish exposed to 100% effluent but increased in those exposed to 20% effluent, the approximate dilution factor in the receiving waters. Plasma vitellogenin concentrations in males increased in a dose-dependent manner with effluent concentration; however, male fertility was not impacted. Although in vitro analyses, analytical chemistry, and biomarker responses confirmed the effluent was estrogenic, estrogen receptor agonists were unlikely the primary driver of impaired reproduction. The results provide insights into the significance of pathway-based effects with regard to predicting adverse reproductive outcomes. This article is protected by copyright. All rights reserved.