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

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.

An inexpensive, temporally integrated system for monitoring occurrence and biological effects of aquatic contaminants in the field.

Assessment of potential risks of complex contaminant mixtures in the environment requires integrated chemical and biological approaches. In support of the US Great Lakes Restoration Initiative, the US Environmental Protection Agency lab in Duluth, MN, is developing these types of methods for assessing possible risks of aquatic contaminants in near-shore Great Lakes (USA) sites. One component involves an exposure system for caged fathead minnow (Pimephales promelas) adults suitable for the wide range of habitat and deployment situations encountered in and around the Great Lakes. To complement the fish exposure system, the authors developed an automated device for collection of composite water samples that could be simultaneously deployed with the cages and reflect a temporally integrated exposure of the animals. The present study describes methodological details of the design, construction, and deployment of a flexible yet comparatively inexpensive (<600 USD) caged-fish/autosampler system. The utility and performance of the system were demonstrated with data collected from deployments at several Great Lakes sites. For example, over 3 field seasons, only 2 of 130 deployed cages were lost, and approximately 99% of successfully deployed adult fish were recovered after exposures of 4 d or longer. A number of molecular, biochemical, and apical endpoints were successfully measured in recovered animals, changes in which reflected known characteristics of the study sites (e.g., upregulation of hepatic genes involved in xenobiotic metabolism in fish held in the vicinity of wastewater treatment plants). The automated composite samplers proved robust with regard to successful water collection (>95% of deployed units in the latest field season), and low within- and among-unit variations were found relative to programmed collection volumes. Overall, the test system has excellent potential for integrated chemical-biological monitoring of contaminants in a variety of field settings.