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

Abstract

Wastewater treatment plant (WWTP) effluents are known contributors of chemical mixtures into the environment. Of particular concern are endocrine-disrupting compounds, such as estrogens, which can affect the 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 1 of 3 effluent concentrations (5%, 20%, and 100%) in a novel onsite, flow-through system providing real-time exposure. The authors examined molecular and biochemical endpoints representing key events along adverse outcome pathways linking estrogen receptor activation and other molecular initiating events to reproductive impairment. In addition, the authors used chemical analysis of the effluent to construct a chemical-gene interaction network to aid in targeted gene expression analyses and identifying 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.

High‐resolution mass spectrometry of skin mucus for monitoring physiological impacts and contaminant biotransformation products in fathead minnows exposed to wastewater effluent

“…The authors also reported significant estrogenicity in the receiving waters as measured with an in vitro cell bioassay using T47D-KBluc cells, which detects estrogen receptor activation [10]. For the present exposures, Cavallin et al reported estrogenic activity (1.5À18.9 ng/L 17a-ethynylestradiol equivalents) in the effluent, using the T47D-KBluc cell bioassay [9]. For the present exposures, Cavallin et al reported estrogenic activity (1.5À18.9 ng/L 17a-ethynylestradiol equivalents) in the effluent, using the T47D-KBluc cell bioassay [9].…”

“…The exposure system employed in the present study has been described previously [9]. Briefly, sexually mature (5-6 mo old) fathead minnows were acclimated for 9 d in control sand-filtered (10 mm), ultraviolet (UV)-treated Lake Superior water at the Duluth US Environmental Protection Agency (USEPA) laboratory and subsequently transported as established pairs to the exposure unit at the Western Lake Superior Sanitary District WWTP.…”

“…In addition, partial least squares-regression models were constructed to identify possible covariance between the mucus metabolites (X-variables) and the various biological endpoints measured by Cavallin et al [9], each used individually as a single Y-variable per model [16,17]. Data were mean-centered and scaled to unit variance.…”

“…In the present study we report the use of untargeted highresolution mass spectrometry (MS)-based metabolomics with skin mucus collected from the fish exposed as part of the Cavallin et al study [9], to evaluate the utility of high-resolution MS for further elucidating biological impacts of the complex effluent. We evaluated both the sex-specific and non-sex-specific nature of the responses with regard to impacts on biochemical pathways and attempted to determine whether compensatory mechanisms resulting from 21 d of exposure could be observed.…”

Returning to normal? Assessing transcriptome recovery over time in male rainbow darter (Etheostoma caeruleum) liver in response to wastewater‐treatment plant upgrades

“…Application of transcriptomics in aquatic ecotoxicology represents a powerful genome-based tool that allows one to obtain detailed insight into toxicological responses [20]. However, only a small subset of these studies have examined molecular responses in wild fish populations residing downstream of MWWTP discharges [5,[22][23][24][25]. The oligonucleotide microarray is a tool that can provide insights into transcriptome patterns, allowing one to examine thousands of genes in unison.…”