Citation:

Cavallin, J., J. Beihoffer, B. Blackwell, A. Cole, D. Ekman, R. Hofer, A. Jastrow, J. Kinsey, K. Keteles, J. Parman, D. Winkelman, AND Dan Villeneuve. Effects-Based Monitoring of Bioactive Compounds Associated with Municipal Wastewater Treatment Plant Effluent Discharge to the South Platte River. SETAC North America, Fort Worth, TX, November 15 - 19, 2020. https://doi.org/10.23645/epacomptox.13100378

Impact/Purpose:

The lack of established water quality criteria or guidelines for many contaminants of emerging concern (CECs) in surface waters represents a significant challenge to state and regional risk assessors charged with protecting our nations waters and associated aquatic ecosystems from harmful impacts of toxic chemicals. For example, recent contaminant and biological effects surveillance on the South Platte and Colorado rivers in Region 8 have detected complex mixtures of contaminants and estrogen receptor (ER), glucocorticoid receptor (GR), and peroxisome proliferator activated receptor (PPAR)-mediated biological activities in surface waters downstream of municipal waste-water treatments plants (WWTP). Their spatial and temporal variation in relation to discharge and flows, potential hazards to resident aquatic organisms, and whether adverse biological effects are occurring, are unknown. Environmental surveillance and monitoring approaches capable of detecting sublethal impacts of chemical contaminants in complex mixtures before they manifest into ecosystem-level impairments, are needed. Furthermore, approaches that provide the ability to relate these effects to potential causative agents and sources are critical for enabling Regional Offices to meet their mandates. The present RARE project (#2100) builds upon several years of preliminary chemical monitoring research on the S Platte River as a basis for further investigation of ER, GR, and PPAR-bioactive contaminants and potential responses elicited in caged fish.

Description:

The present study highlights the utility of bioeffects-based monitoring in conjunction with analytical chemical measurements of surface waters on the S. Platte River associated with a historically bioactive wastewater treatment plant effluent. Concurrent with chemical monitoring and in vitro bioactivity measurements, in situ caged fish systems were employed to evaluate the potential bioavailability of predicted biologically-active contaminants that can mimic the effects of hormones involved in regulating reproduction, sexual differentiation, stress responses, and lipid metabolism. Abstract: Previous studies have detected numerous contaminants of emerging concern (CECs), including pharmaceuticals, personal care products, and pesticides, as well as in vitro bioactivities in the South Platte River near Denver, Colorado, USA. CECs have the potential to perturb endogenous biological pathways in exposed organisms. To assess the spatial and temporal distribution of CECs, surface water samples were collected and analyzed bi-monthly throughout 2018 and 2019 at 10 sites along the S. Platte River and surrounding tributaries with varying proximities to a wastewater treatment plant (WWTP). Water samples were analyzed for a suite of pharmaceuticals, pesticides, steroid hormones, and wastewater indicators as well as screened for in vitro biological activities. In vitro multi-factorial Attagene assays, screening for agonistic activity against 25 human nuclear receptors, detected estrogen receptor (ER), glucocorticoid receptor (GR), and peroxisome proliferator activated receptor-gamma (PPAR) bioactivities in surface water samples near the WWTP discharge. Targeted in vitro transcriptional activation assays for ER, GR, and PPAR corroborated bioactivities for ER (up to 19 ± 6 ng/L 17β-estradiol equivalents) and GR (up to 77 ± 31 ng/L Dexamethasone equivalents), while PPAR activity was not confirmed. To evaluate the potential in vivo effects of contaminants, adult fathead minnows were caged at six locations upstream and downstream of the WWTP. After five days of exposure, muscle, livers, adipose, gonads, and brains were collected for measurement of targeted gene expression. Significant up-regulation of estrogen-responsive hepatic vitellogenin was observed in males exposed at sites with corresponding in vitro ER activity. Despite GR-activity in vitro, no site-related differences in GR-related gene expression were detected in female adipose or male livers, suggesting observed environmental concentrations of GR-active contaminants do not induce a detectable in vivo response. Consistent with the general lack of detectable in vitro PPARɣ activity, there were no significant effects on PPARɣ-related gene expression in the female adipose or male livers. Although the chemicals responsible for GR- and PPAR-mediated biological activities are still unknown, results from the present study provide insights into the significance of these bioactivities relative to in situ fish exposures. The contents of this abstract neither constitute nor reflect US EPA policy.

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