Potential Toxicity of Complex Mixtures in Surface Waters from a Nationwide Survey of United States Streams: Identifying in Vitro Bioactivities and Causative Chemicals

Moldable Plastics (Polycaprolactone) can be Acutely Toxic to Developing Zebrafish and Activate Nuclear Receptors in Mammalian Cells

Popularized on social media, hand-moldable plastics are formed by consumers into tools, trinkets, and dental prosthetics. Despite the anticipated dermal and oral contact, manufacturers share little information with consumers about these materials, which are typically sold as microplastic-sized resin pellets. Inherent to their function, moldable plastics pose a risk of dermal and oral exposure to unknown leachable substances. We analyzed 12 moldable plastics advertised for modeling and dental applications and determined them to be polycaprolactone (PCL) or thermoplastic polyurethane (TPU). The bioactivities of the most popular brands advertised for modeling applications of each type of polymer were evaluated using a zebrafish embryo bioassay. While water-borne exposure to the TPU pellets did not affect the targeted developmental end points at any concentration tested, the PCL pellets were acutely toxic above 1 pellet/mL. The aqueous leachates of the PCL pellets demonstrated similar toxicity. Methanolic extracts from the PCL pellets were assayed for their bioactivity using the Attagene FACTORIAL platform. Of the 69 measured end points, the extracts activated nuclear receptors and transcription factors for xenobiotic metabolism (pregnane X receptor, PXR), lipid metabolism (peroxisome proliferator-activated receptor γ, PPARγ), and oxidative stress (nuclear factor erythroid 2-related factor 2, NRF2). By nontargeted high-resolution comprehensive two-dimensional gas chromatography (GC × GC-HRT), we tentatively identified several compounds in the methanolic extracts, including PCL oligomers, a phenolic antioxidant, and residues of suspected antihydrolysis and cross-linking additives. In a follow-up zebrafish embryo bioassay, because of its stated high purity, biomedical grade PCL was tested to mitigate any confounding effects due to chemical additives in the PCL pellets; it elicited comparable acute toxicity. From these orthogonal and complementary experiments, we suggest that the toxicity was due to oligomers and nanoplastics released from the PCL rather than chemical additives. These results challenge the perceived and assumed inertness of plastics and highlight their multiple sources of toxicity.

Potential Hazards of Polycyclic Aromatic Hydrocarbons in Great Lakes Tributaries Using Water Column and Porewater Passive Samplers and Sediment Equilibrium Partitioning

The potential for polycyclic aromatic hydrocarbon (PAH)-related effects in benthic organisms is commonly estimated from organic carbon-normalized sediment concentrations based on equilibrium partitioning (EqP). Although this approach is useful for screening purposes, it may overestimate PAH bioavailability by orders of magnitude in some sediments, leading to inflated exposure estimates and potentially unnecessary remediation costs. Recently, passive samplers have been shown to provide an accurate assessment of the freely dissolved concentrations of PAHs, and thus their bioavailability and possible biological effects, in sediment porewater and overlying surface water. We used polyethylene passive sampling devices (PEDs) to measure freely dissolved porewater and water column PAH concentrations at 55 Great Lakes (USA/Canada) tributary locations. The potential for PAH-related biological effects using PED concentrations were estimated with multiple approaches by applying EqP, water quality guidelines, and pathway-based biological activity based on in vitro bioassay results from ToxCast. Results based on the PED-based exposure estimates were compared with EqP-derived exposure estimates for concurrently collected sediment samples. The results indicate a potential overestimation of bioavailable PAH concentrations by up to 960-fold using the EqP-based method compared with measurements using PEDs. Even so, PED-based exposure estimates indicate a high potential for PAH-related biological effects at 14 locations. Our findings provide an updated, weight-of-evidence-based site prioritization to help guide possible future monitoring and mitigation efforts. Environ Toxicol Chem 2024;43:1509-1523. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

High-Efficiency Effect-Directed Analysis Leveraging Five High Level Advancements: A Critical Review

Organic contaminants are ubiquitous in the environment, with mounting evidence unequivocally connecting them to aquatic toxicity, illness, and increased mortality, underscoring their substantial impacts on ecological security and environmental health. The intricate composition of sample mixtures and uncertain physicochemical features of potential toxic substances pose challenges to identify key toxicants in environmental samples. Effect-directed analysis (EDA), establishing a connection between key toxicants found in environmental samples and associated hazards, enables the identification of toxicants that can streamline research efforts and inform management action. Nevertheless, the advancement of EDA is constrained by the following factors: inadequate extraction and fractionation of environmental samples, limited bioassay endpoints and unknown linkage to higher order impacts, limited coverage of chemical analysis (i.e., high-resolution mass spectrometry, HRMS), and lacking effective linkage between bioassays and chemical analysis. This review proposes five key advancements to enhance the efficiency of EDA in addressing these challenges: (1) multiple adsorbents for comprehensive coverage of chemical extraction, (2) high-resolution microfractionation and multidimensional fractionation for refined fractionation, (3) robust in vivo/vitro bioassays and omics, (4) high-performance configurations for HRMS analysis, and (5) chemical-, data-, and knowledge-driven approaches for streamlined toxicant identification and validation. We envision that future EDA will integrate big data and artificial intelligence based on the development of quantitative omics, cutting-edge multidimensional microfractionation, and ultraperformance MS to identify environmental hazard factors, serving for broader environmental governance.

Linking Mechanistic Effects of Pharmaceuticals and Personal Care Products to Ecologically Relevant Outcomes: A Decade of Progress

There are insufficient toxicity data to assess the ecological risks of many pharmaceuticals and personal care products (PPCPs). While data limitations are not uncommon for contaminants of environmental concern, PPCPs are somewhat unique in that an a priori understanding of their biological activities in conjunction with measurements of molecular, biochemical, or histological responses could provide a foundation for understanding mode(s) of action and predicting potential adverse apical effects. Over the past decade significant progress has been made in the development of new approach methodologies (NAMs) to efficiently quantify these types of endpoints using computational models and pathway-based in vitro and in vivo assays. The availability of open-access knowledgebases to curate biological response (including NAM) data and sophisticated bioinformatics tools to help interpret the information also has significantly increased. Finally, advances in the development and implementation of the adverse outcome pathway framework provide the critical conceptual underpinnings needed to translate NAM data into predictions of the ecologically relevant outcomes required by risk assessors and managers. The evolution and convergence of these various data streams, tools, and concepts provides the basis for a fundamental change in how ecological risks of PPCPs can be pragmatically assessed. Environ Toxicol Chem 2024;43:537-548. © 2022 SETAC. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

High-Throughput Transcriptomics of Water Extracts Detects Reductions in Biological Activity with Water Treatment Processes

The presence of numerous chemical contaminants from industrial, agricultural, and pharmaceutical sources in water supplies poses a potential risk to human and ecological health. Current chemical analyses suffer from limitations, including chemical coverage and high cost, and broad-coverage in vitro assays such as transcriptomics may further improve water quality monitoring by assessing a large range of possible effects. Here, we used high-throughput transcriptomics to assess the activity induced by field-derived water extracts in MCF7 breast carcinoma cells. Wastewater and surface water extracts induced the largest changes in expression among cell proliferation-related genes and neurological, estrogenic, and antibiotic pathways, whereas drinking and reclaimed water extracts that underwent advanced treatment showed substantially reduced bioactivity on both gene and pathway levels. Importantly, reclaimed water extracts induced fewer changes in gene expression than laboratory blanks, which reinforces previous conclusions based on targeted assays and improves confidence in bioassay-based monitoring of water quality.

Assessment of bioactive chemicals in wastewater effluents and surface waters using in vitro bioassays in the Nakdong River basin, Korea

Organic micropollutants present in effluents of wastewater treatment plants (WWTPs) can negatively affect the quality of receiving waters or drinking water sources. The present work monitored the concentration of bioactive chemicals using a battery of in vitro bioassays in 14 WWTP effluents, 2 effluent-dominant streams, and 5 river waters in the Nakdong River basin, Korea, for a two-year period. The WWTP effluents showed AR/ERα/TRβ (androgen/estrogen/thyroid hormone) activities at a few to tens ng/L, PAH/PPARγ/p53 (polycyclic-aromatic-hydrocarbon/lipid metabolism/genotoxicity) activities at hundreds ng/L, and PXR/Nrf2 (xenobiotic metabolism/oxidative stress) activities at tens to hundreds μg/L as bioanalytical equivalent concentrations. The concentration level and type of bioactivities were statistically not affected by the source, season, or treatment processes of WWTPs for most endpoints. The effluent-dominant streams showed similar levels of AR/ERα/PAH/PXR/Nrf2 activities compared to the upstream WWTP effluents. The river waters showed lower levels of AR/ERα activities (by factors of 6 or 7) but had only slightly lower PAH/PXR/Nrf2 activities (within factors of 2) than the WWTP effluents when compared based on median concentration. Cytotoxicity was below the quantification limit (0.3 μg/L) in most effluent and river samples. For ERα/PAH/PXR/Nrf2, the median bioactivity levels of the river waters were higher than at least one of the effect-based trigger (EBT) values proposed in the literature. Further monitoring work and reliable/realistic EBT derivation are needed to determine possible ecological risks posed by the observed bioactivities.

Changes in chemical occurrence, concentration, and bioactivity in the Colorado River before and after replacement of the Moab, Utah wastewater treatment plant

Long-term (2010-19) water-quality monitoring on the Colorado River downstream from Moab Utah indicated the persistent presence of Bioactive Chemicals (BC), such as pesticides and pharmaceuticals. This stream reach near Canyonlands National Park provides critical habitat for federally endangered species. The Moab wastewater treatment plant (WWTP) outfall discharges to the Colorado River and is the nearest potential point-source to this reach. The original WWTP was replaced in 2018. In 2016-19, a study was completed to determine if the new plant reduced BC input to the Colorado River at, and downstream from, the outfall. Water samples were collected before and after the plant replacement at sites upstream and downstream from the outfall. Samples were analyzed for as many as 243 pesticides, 109 pharmaceuticals, 20 hormones, 51 wastewater indicator chemicals, 20 metals, and 8 nutrients. BC concentrations, hazard quotients (HQs), and exposure activity ratios (EARs) were used to identify and prioritize contaminants for their potential to have adverse biological effects on the health of native and endangered wildlife. There were 22 BC with HQs >1, mostly metals and hormones; and 23 BC with EARs >0.1, mostly hormones and pharmaceuticals. Most high HQs or EARs were associated with samples collected at the WWTP outfall site prior to its replacement. Discharge from the new plant had reduced concentrations of nutrients, hormones, pharmaceuticals, and other BC. For example, all 16 of the hormones detected at the WWTP outfall site had maximum concentrations in samples collected prior to the WWTP replacement. The WWTP replacement had less effect on instream concentrations of metals and pesticides, BC whose sources are less directly tied to domestic wastewater. Study results indicate that improved WWTP technology can create substantial reductions in concentrations of non-regulated BC such as pharmaceuticals, in addition to regulated contaminants such as nutrients.

Water, Water Everywhere, but Every Drop Unique: Challenges in the Science to Understand the Role of Contaminants of Emerging Concern in the Management of Drinking Water Supplies

The protection and management of water resources continues to be challenged by multiple and ongoing factors such as shifts in demographic, social, economic, and public health requirements. Physical limitations placed on access to potable supplies include natural and human-caused factors such as aquifer depletion, aging infrastructure, saltwater intrusion, floods, and drought. These factors, although varying in magnitude, spatial extent, and timing, can exacerbate the potential for contaminants of concern (CECs) to be present in sources of drinking water, infrastructure, premise plumbing and associated tap water. This monograph examines how current and emerging scientific efforts and technologies increase our understanding of the range of CECs and drinking water issues facing current and future populations. It is not intended to be read in one sitting, but is instead a starting point for scientists wanting to learn more about the issues surrounding CECs. This text discusses the topical evolution CECs over time (Section 1), improvements in measuring chemical and microbial CECs, through both analysis of concentration and toxicity (Section 2) and modeling CEC exposure and fate (Section 3), forms of treatment effective at removing chemical and microbial CECs (Section 4), and potential for human health impacts from exposure to CECs (Section 5). The paper concludes with how changes to water quantity, both scarcity and surpluses, could affect water quality (Section 6). Taken together, these sections document the past 25 years of CEC research and the regulatory response to these contaminants, the current work to identify and monitor CECs and mitigate exposure, and the challenges facing the future.

Photochemical mobilization of dissolved hydrocarbon oxidation products from petroleum contaminated soil into a shallow aquifer activate human nuclear receptors

Elevated non-volatile dissolved organic carbon (NVDOC) concentrations in groundwater (GW) monitoring wells under oil-contaminated hydrophobic soils originating from a pipeline rupture at the National Crude Oil Spill & Natural Attenuation Research Site near Bemidji, MN are documented. We hypothesized the elevated NVDOC is comprised of water-soluble photooxidation products transported from the surface to the aquifer. We use field and laboratory samples in combination with complementary analytical methods to test this hypothesis and determine the biological response to these products. Observations from optical spectroscopy and ultrahigh-resolution mass spectrometry reveal a significant correlation between the chemical composition of NVDOC leached from photochemically weathered soils and GW monitoring wells with high NVDOC concentrations measured in the aquifer beneath the contaminated soil. Conversely, the chemical composition from the uncontaminated soil photoleachate matches the NVDOC observed in the uncontaminated wells. Contaminated GW and photodissolution leachates from contaminated soil activated biological targets indicative of xenobiotic metabolism and exhibited potential for adverse effects. Newly formed hydrocarbon oxidation products (HOPs) from fresh oil could be distinguished from those downgradient. This study illustrates another pathway for dissolved HOPs to infiltrate GW and potentially affect human health and the environment.

Identification and Prioritization of Environmental Organic Pollutants: From an Analytical and Toxicological Perspective

Exposure to environmental organic pollutants has triggered significant ecological impacts and adverse health outcomes, which have been received substantial and increasing attention. The contribution of unidentified chemical components is considered as the most significant knowledge gap in understanding the combined effects of pollutant mixtures. To address this issue, remarkable analytical breakthroughs have recently been made. In this review, the basic principles on recognition of environmental organic pollutants are overviewed. Complementary analytical methodologies (i.e., quantitative structure-activity relationship prediction, mass spectrometric nontarget screening, and effect-directed analysis) and experimental platforms are briefly described. The stages of technique development and/or essential parts of the analytical workflow for each of the methodologies are then reviewed. Finally, plausible technique paths and applications of the future nontarget screening methods, interdisciplinary techniques for achieving toxicant identification, and burgeoning strategies on risk assessment of chemical cocktails are discussed.

Disclosing Environmental Ligands of L-FABP and PPARγ: Should We Re-evaluate the Chemical Safety of Hydrocarbon Surfactants?

Chemical contaminants can cause adverse effects by binding to the liver-fatty acid binding protein (L-FABP) and peroxisome proliferator-activated nuclear receptor γ (PPARγ), which are vital in lipid metabolism. However, the presence of numerous compounds in the environment has hindered the identification of their ligands, and thus only a small portion have been discovered to date. In this study, protein Affinity Purification with Nontargeted Analysis (APNA) was employed to identify the ligands of L-FABP and PPARγ in indoor dust and sewage sludge. A total of 83 nonredundant features were pulled-out by His-tagged L-FABP as putative ligands, among which 13 were assigned as fatty acids and hydrocarbon surfactants. In contrast, only six features were isolated when His-tagged PPARγ LBD was used as the protein bait. The binding of hydrocarbon surfactants to L-FABP and PPARγ was confirmed using both recombinant proteins and reporter cells. These hydrocarbon surfactants, along with >50 homologues and isomers, were detected in dust and sludge at high concentrations. Fatty acids and hydrocarbon surfactants explained the majority of L-FABP (57.7 ± 32.9%) and PPARγ (66.0 ± 27.1%) activities in the sludge. This study revealed hydrocarbon surfactants as the predominant synthetic ligands of L-FABP and PPARγ, highlighting the importance of re-evaluating their chemical safety.

Putative adverse outcome pathway development based on physiological responses of female fathead minnows to model estrogen versus androgen receptor agonists

Several adverse outcome pathways (AOPs) have linked molecular initiating events like aromatase inhibition, androgen receptor (AR) agonism, and estrogen receptor (ER) antagonism to reproductive impairment in adult fish. Estrogen receptor agonists can also cause adverse reproductive effects, however, the early key events (KEs) in an AOP leading to this are mostly unknown. The primary aim of this study was to develop hypotheses regarding the potential mechanisms through which exposure to ER agonists might lead to reproductive impairment in female fish. Mature fathead minnows were exposed to 1 or 10 ng 17α-ethynylestradiol (EE2)/L or 10 or 100 µg bisphenol A (BPA)/L for 14 d. The response to EE2 and BPA was contrasted with the effects of 500 ng/L of 17β-trenbolone (TRB), an AR agonist, as well as TRB combined with the low and high concentrations of EE2 or BPA tested individually. Exposure to 10 ng EE2/L, 100 µg BPA/L, TRB, or the various mixtures with TRB caused significant decreases in plasma concentrations of 17β-estradiol. Exposure to TRB alone caused a significant reduction in plasma vitellogenin (VTG), but VTG was unaffected or even increased in females exposed to EE2 or BPA alone or, in most cases, in mixtures with TRB. Over the course of the 14-d exposure, the only treatments that clearly did not affect egg production were 1 ng EE2/L and 10 µg BPA/L. Based on these results and knowledge of hypothalamic-pituitary-gonadal axis function, we hypothesize an AOP whereby decreased production of maturation-inducing steroid leading to impaired oocyte maturation and ovulation, possibly due to negative feedback or direct inhibitory effects of membrane ER activation, could be responsible for causing adverse reproductive impacts in female fish exposed to ER agonists.

Bioanalytical and chemical characterization of organic micropollutant mixtures in long-term exposed passive samplers from the Joint Danube Survey 4: Setting a baseline for water quality monitoring

Monitoring methodologies reflecting the long-term quality and contamination of surface waters are needed to obtain a representative picture of pollution and identify risk drivers. This study sets a baseline for characterizing chemical pollution in the Danube River using an innovative approach, combining continuous three-months use of passive sampling technology with comprehensive chemical (747 chemicals) and bioanalytical (seven in vitro bioassays) assessment during the Joint Danube Survey (JDS4). This is one of the world's largest investigative surface-water monitoring efforts in the longest river in the European Union, which water after riverbank filtration is broadly used for drinking water production. Two types of passive samplers, silicone rubber (SR) sheets for hydrophobic compounds and AttractSPETM HLB disks for hydrophilic compounds, were deployed at nine sites for approximately 100 days. The Danube River pollution was dominated by industrial compounds in SR samplers and by industrial compounds together with pharmaceuticals and personal care products in HLB samplers. Comparison of the Estimated Environmental Concentrations with Predicted No-Effect Concentrations revealed that at the studied sites, at least one (SR) and 4-7 (HLB) compound(s) exceeded the risk quotient of 1. We also detected AhR-mediated activity, oxidative stress response, peroxisome proliferator-activated receptor gamma-mediated activity, estrogenic, androgenic, and anti-androgenic activities using in vitro bioassays. A significant portion of the AhR-mediated and estrogenic activities could be explained by detected analytes at several sites, while for the other bioassays and other sites, much of the activity remained unexplained. The effect-based trigger values for estrogenic and anti-androgenic activities were exceeded at some sites. The identified drivers of mixture in vitro effects deserve further attention in ecotoxicological and environmental pollution research. This novel approach using long-term passive sampling provides a representative benchmark of pollution and effect potentials of chemical mixtures for future water quality monitoring of the Danube River and other large water bodies.

Evaluation of Complex Mixture Toxicity in the Milwaukee Estuary (WI, USA) Using Whole-Mixture and Component-Based Evaluation Methods

Anthropogenic activities introduce complex mixtures into aquatic environments, necessitating mixture toxicity evaluation during risk assessment. There are many alternative approaches that can be used to complement traditional techniques for mixture assessment. Our study aimed to demonstrate how these approaches could be employed for mixture evaluation in a target watershed. Evaluations were carried out over 2 years (2017-2018) across 8-11 study sites in the Milwaukee Estuary (WI, USA). Whole mixtures were evaluated on a site-specific basis by deploying caged fathead minnows (Pimephales promelas) alongside composite samplers for 96 h and characterizing chemical composition, in vitro bioactivity of collected water samples, and in vivo effects in whole organisms. Chemicals were grouped based on structure/mode of action, bioactivity, and pharmacological activity. Priority chemicals and mixtures were identified based on their relative contributions to estimated mixture pressure (based on cumulative toxic units) and via predictive assessments (random forest regression). Whole mixture assessments identified target sites for further evaluation including two sites targeted for industrial/urban chemical mixture effects assessment; three target sites for pharmaceutical mixture effects assessment; three target sites for further mixture characterization; and three low-priority sites. Analyses identified 14 mixtures and 16 chemicals that significantly contributed to cumulative effects, representing high or medium priority targets for further ecotoxicological evaluation, monitoring, or regulatory assessment. Overall, our study represents an important complement to single-chemical prioritizations, providing a comprehensive evaluation of the cumulative effects of mixtures detected in a target watershed. Furthermore, it demonstrates how different tools and techniques can be used to identify diverse facets of mixture risk and highlights strategies that can be considered in future complex mixture assessments. Environ Toxicol Chem 2023;42:1229-1256. © 2023 SETAC.

In vitro bioassays to monitor complex chemical mixtures at a carbon-based indirect potable reuse plant

Potable water reuse technologies are used to treat wastewater to drinking water quality to help sustain a community's water resources. California has long led the adoption of potable water reuse technologies in the United States and more states are exploring these technologies as water resources decline. Reuse technologies also need to achieve adequate reductions in microbial and chemical contaminant risks to meet public health goals and secure public acceptance. In vitro bioassays are a useful tool for screening if reuse treatment processes adequately reduce toxicity associated with a range of chemical classes that are contaminants of concern. In this study, we used an aryl hydrocarbon receptor (AhR) and an estrogen receptor luciferase bioassay to detect the presence of dioxin-like and estrogenic compounds across a 3800 m³/d carbon-based indirect potable reuse plant that uses carbon-based treatment (SWIFT-RC). Our results demonstrate significant removal of dioxin-like compounds across the SWIFT-RC treatment train. Estrogenicity declined across the treatment train for some months but was extremely variable and low with many samples falling below the method quantification level; consequently, we were not able to reliably determine estrogenicity trends for SWIFT-RC. Comparing the bioanalytical equivalent concentrations detected in the SWIFT-RC water with established monitoring trigger levels from the state of California suggests that SWIFT-RC produced water that met the bioassay guidelines. The log total organic carbon concentration and AhR assay equivalent concentrations are weakly correlated when data across all SWIFT-RC processes are included. Overall, this research demonstrates the performance of in vitro bioassays at a demonstration-scale carbon-based IPR system and highlights both the potential utility and challenges associated with these methods for assessing system performance.

AOP Report: Adverse Outcome Pathways for Aromatase Inhibition or Androgen Receptor Agonism Leading to Male-Biased Sex Ratio and Population Decline in Fish

Screening and testing of potential endocrine-disrupting chemicals for ecological effects are examples of risk assessment/regulatory activities that can employ adverse outcome pathways (AOPs) to establish linkages between readily measured alterations in endocrine function and whole organism- and population-level responses. Of particular concern are processes controlled by the hypothalamic-pituitary-gonadal/thyroidal (HPG/T) axes. However, the availability of AOPs suitable to meet this need is currently limited in terms of species and life-stage representation relative to the diversity of endpoints influenced by HPG/T function. In our report we describe two novel AOPs that comprise a simple AOP network focused on the effects of chemicals on sex differentiation during early development in fish. The first AOP (346) documents events starting with inhibition of cytochrome P450 aromatase (CYP19), resulting in decreased availability of 17β-estradiol during gonad differentiation, which increases the occurrence of testis formation, resulting in a male-biased sex ratio and consequent population-level declines. The second AOP (376) is initiated by activation of the androgen receptor (AR), also during sexual differentiation, again resulting in a male-biased sex ratio and population-level effects. Both AOPs are strongly supported by existing physiological and toxicological evidence, including numerous fish studies with model CYP19 inhibitors and AR agonists. Accordingly, AOPs 346 and 376 provide a basis for more focused screening and testing of chemicals with the potential to affect HPG function in fish during early development. Environ Toxicol Chem 2023;42:747-756. Published 2023. This article is a U.S. Government work and is in the public domain in the USA.

In vitro bioanalytical assessment of the occurrence and removal of bioactive chemicals in municipal wastewater treatment plants in Korea

Effluents of wastewater treatment plants (WWTPs) contain various organic micropollutants, some of which can exert negative effects on the quality of receiving waters or drinking water sources. This study monitored two full-scale WWTPs in Korea for the occurrence and removal of bioactive chemicals for a one-year period using a battery of in vitro bioassays as a complementary approach to chemical analysis. Bioassays covering different endpoints were employed, such as hormone receptor activation (AR and ERα), xenobiotic metabolism (PAH and PXR), oxidative stress response (Nrf2), and cytotoxicity. The WWTP influents showed AR, ERα, and PAH activities at ng/L - μg/L and PXR and Nrf2 activities at μg/L - mg/L as bioanalytical equivalent concentrations of a reference compound for each bioassay. These bioactivities decreased along with the WWTP treatment train, with significant removals achieved by the secondary biological treatment processes. Cytotoxicity was observed only for some municipal wastewater (M-WWTP) influents but was below the limit of quantification for most cases. The influent and effluent bioactivities observed in this study were mostly comparable to those reported in other WWTPs in the literature. Comparison of the bioactivities with the effect-based trigger (EBT) values indicates that the impact of WWTP effluents on receiving water quality was low for most endpoints. For Nrf2, however, further investigation is required to evaluate the observed high bioactivities compared with the current EBT. The observed ERα activity could partly be explained by the presence of some steroid estrogens. Overall, our results contribute to an important database for the concentrations and removal efficiencies of bioactive chemicals in WWTPs and demonstrate bioassays as a useful tool for urban water quality monitoring.

Prioritizing Pesticides of Potential Concern and Identifying Potential Mixture Effects in Great Lakes Tributaries Using Passive Samplers

To help meet the objectives of the Great Lakes Restoration Initiative with regard to increasing knowledge about toxic substances, 223 pesticides and pesticide transformation products were monitored in 15 Great Lakes tributaries using polar organic chemical integrative samplers. A screening-level assessment of their potential for biological effects was conducted by computing toxicity quotients (TQs) for chemicals with available US Environmental Protection Agency (USEPA) Aquatic Life Benchmark values. In addition, exposure activity ratios (EAR) were calculated using information from the USEPA ToxCast database. Between 16 and 81 chemicals were detected per site, with 97 unique compounds detected overall, for which 64 could be assessed using TQs or EARs. Ten chemicals exceeded TQ or EAR levels of concern at two or more sites. Chemicals exceeding thresholds included seven herbicides (2,4-dichlorophenoxyacetic acid, diuron, metolachlor, acetochlor, atrazine, simazine, and sulfentrazone), a transformation product (deisopropylatrazine), and two insecticides (fipronil and imidacloprid). Watersheds draining agricultural and urban areas had more detections and higher concentrations of pesticides compared with other land uses. Chemical mixtures analysis for ToxCast assays associated with common modes of action defined by gene targets and adverse outcome pathways (AOP) indicated potential activity on biological pathways related to a range of cellular processes, including xenobiotic metabolism, extracellular signaling, endocrine function, and protection against oxidative stress. Use of gene ontology databases and the AOP knowledgebase within the R-package ToxMixtures highlighted the utility of ToxCast data for identifying and evaluating potential biological effects and adverse outcomes of chemicals and mixtures. Results have provided a list of high-priority chemicals for future monitoring and potential biological effects warranting further evaluation in laboratory and field environments. Environ Toxicol Chem 2023;42:340-366. Published 2022. This article is a U.S. Government work and is in the public domain in the USA. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Review of ecologically relevant in vitro bioassays to supplement current in vivo tests for whole effluent toxicity testing - Part 1: Apical endpoints

Whole effluent toxicity (WET) testing is commonly used to ensure that wastewater discharges do not pose an unacceptable risk to receiving environments. Traditional WET testing involves exposing animals to (waste)water samples to assess four major ecologically relevant apical endpoints: mortality, growth, development, and reproduction. Recently, with the widespread implementation of the 3Rs to replace, reduce and refine the use of animals in research and testing, there has been a global shift away from in vivo testing towards in vitro alternatives. However, prior to the inclusion of in vitro bioassays in regulatory frameworks, it is critical to establish their ecological relevance and technical suitability. This is part 1 of a two-part review that aims to identify in vitro bioassays that can be used in WET testing and relate them to ecologically relevant endpoints through toxicity pathways, providing the reader with a high-level overview of current capabilities. Part 1 of this review focuses on four apical endpoints currently included in WET testing: mortality, growth, development, and reproduction. For each endpoint, the link between responses at the molecular or cellular level, that can be measured in vitro, and the adverse outcome at the organism level were established through simplified toxicity pathways. Additionally, literature from 2015 to 2020 on the use of in vitro bioassays for water quality assessments was reviewed to identify a list of suitable bioassays for each endpoint. This review will enable the prioritization of relevant endpoints and bioassays for incorporation into WET testing.

Review of ecologically relevant in vitro bioassays to supplement current in vivo tests for whole effluent toxicity testing - Part 2: Non-apical endpoints

Whole effluent toxicity (WET) testing uses whole animal exposures to assess the toxicity of complex mixtures, like wastewater. These assessments typically include four apical endpoints: mortality, growth, development, and reproduction. In the last decade, there has been a shift to alternative methods that align with the 3Rs to replace, reduce, and refine the use of animals in research. In vitro bioassays can provide a cost-effective, high-throughput, ethical alternative to in vivo assays. In addition, they can potentially include additional, more sensitive, environmentally relevant endpoints than traditional toxicity tests. However, the ecological relevance of these endpoints must be established before they are adopted into regulatory frameworks. This is Part 2 of a two-part review that aims to identify in vitro bioassays that are linked to ecologically relevant endpoints that could be included in WET testing. Part 2 of this review focuses on non-apical endpoints that should be incorporated into WET testing. In addition to the four apical endpoints addressed in Part 1, this review identified seven additional toxic outcomes: endocrine disruption, xenobiotic metabolism, carcinogenicity, oxidative stress, inflammation, immunotoxicity and neurotoxicity. For each, the response at the molecular or cellular level measured in vitro was linked to the response at the organism level through a toxicity pathway. Literature from 2015 to 2020 was used to identify suitable bioassays that could be incorporated into WET testing.

Wastewater toxicity removal: Integrated chemical and effect-based monitoring of full-scale conventional activated sludge and membrane bioreactor plants

The literature is currently lacking effect-based monitoring studies targeted at evaluating the performance of full-scale membrane bioreactor plants. In this research, a monitoring campaign was performed at a full-scale wastewater treatment facility with two parallel lines (traditional activated sludge and membrane bioreactor). Beside the standard parameters (COD, nitrogen, phosphorus, and metals), 6 polynuclear aromatic hydrocarbons, 29 insecticides, 2 herbicides, and 3 endocrine disrupting compounds were measured. A multi-tiered battery of bioassays complemented the investigation, targeting different toxic modes of action and employing various biological systems (uni/multicellular, prokaryotes/eukaryotes, trophic level occupation). A traffic light scoring approach was proposed to quickly visualize the impact of treatment on overall toxicity that occurred after the exposure to raw and concentrated wastewater. Analysis of the effluents of the CAS and MBR lines show very good performance of the two systems for removal of organic micropollutants and metals. The most noticeable differences between CAS and MBR occurred in the concentration of suspended solids; chemical analyses did not show major differences. On the other hand, bioassays demonstrated better performance for the MBR. Both treatment lines complied with the Italian law's "ecotoxicity standard for effluent discharge in surface water". Yet, residual biological activity was still detected, demonstrating the adequacy and sensitivity of the toxicological tools, which, by their inherent nature, allow the overall effects of complex mixtures to be taken into account.

Combining Passive Sampling with Suspect and Nontarget Screening to Characterize Organic Micropollutants in Streams Draining Mixed-Use Watersheds

Organic micropollutants (OMPs) represent an anthropogenic stressor on stream ecosystems. In this work, we combined passive sampling with suspect and nontarget screening enabled by liquid chromatography-high-resolution mass spectrometry to characterize complex mixtures of OMPs in streams draining mixed-use watersheds. Suspect screening identified 122 unique OMPs for target quantification in polar organic chemical integrative samplers (POCIS) and grab samples collected from 20 stream sites in upstate New York over two sampling seasons. Hierarchical clustering established the co-occurrence profiles of OMPs in connection with watershed attributes indicative of anthropogenic influences. Nontarget screening leveraging the time-integrative nature of POCIS and the cross-site variability in watershed attributes prioritized and confirmed 11 additional compounds that were ubiquitously present in monitored streams. Field sampling rates for 37 OMPs that simultaneously occurred in POCIS and grab samples spanned the range of 0.02 to 0.22 L/d with a median value of 0.07 L/d. Comparative analyses of the daily average loads, cumulative exposure-activity ratios, and multi-substance potentially affected fractions supported the feasibility of complementing grab sampling with POCIS for OMP load estimation and screening-level risk assessments. Overall, this work demonstrated a multi-watershed sampling and screening approach that can be adapted to assess OMP contamination in streams across landscapes.

Combining Polar Organic Chemical Integrative Samplers (POCIS) with Toxicity Testing on Microalgae to Evaluate the Impact of Herbicide Mixtures in Surface Waters

Pesticide risk assessment within the European Union Water Framework Directive is largely deficient in the assessment of the actual exposure and chemical mixture effects. Pesticide contamination, in particular herbicidal loading, has been shown to exert pressure on surface waters. Such pollution can have direct impact on autotrophic species, as well as indirect impacts on freshwater communities through primary production degradation. The present study proposes a screening method combining polar organic chemical integrative samplers (POCIS) with mode of action-specific toxicity testing on microalgae exposed to POCIS extracts as a standard approach to effectively address the problem of herbicide mixture effects detection. This methodology has been tested using Luxembourgish rivers as a case study and has proven to be a fast and reliable information source that is complementary to chemical analysis, allowing assessment of missing target analytes. Pesticide pressure in the 24 analyzed streams was mainly exerted by flufenacet, terbuthylazine, nicosulfuron, and foramsulfuron, with occasional impacts by the nonagricultural biocide diuron. Algae tests were more sensitive to endpoints affecting photosystem II and reproduction than to growth and could be best predicted with the concentration addition model. In addition, analysis revealed that herbicide mixture toxicity is correlated with macrophyte disappearance in the field, relating mainly to emissions from maize cultures. Combining passive sampler extracts with standard toxicity tests offers promising perspectives for ecological risk assessment. The full implementation of the proposed approach, however, requires adaptation of the legislation to scientific progress. Environ Toxicol Chem 2022;41:2667-2678. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Daphnia as a Sentinel Species for Environmental Health Protection: A Perspective on Biomonitoring and Bioremediation of Chemical Pollution

Despite available technology and the knowledge that chemical pollution damages human and ecosystem health, chemical pollution remains rampant, ineffectively monitored, rarely prevented, and only occasionally mitigated. We present a framework that helps address current major challenges in the monitoring and assessment of chemical pollution by broadening the use of the sentinel species Daphnia as a diagnostic agent of water pollution. And where prevention has failed, we propose the application of Daphnia as a bioremediation agent to help reduce hazards from chemical mixtures in the environment. By applying "omics" technologies to Daphnia exposed to real-world ambient chemical mixtures, we show improvements at detecting bioactive components of chemical mixtures, determining the potential effects of untested chemicals within mixtures, and identifying targets of toxicity. We also show that using Daphnia strains that naturally adapted to chemical pollution as removal agents of ambient chemical mixtures can sustainably improve environmental health protection. Expanding the use of Daphnia beyond its current applications in regulatory toxicology has the potential to improve both the assessment and the remediation of environmental pollution.

Using the Daphnia magna Transcriptome to Distinguish Water Source: Wetland and Stormwater Case Studies

A major challenge in ecotoxicology is accurately and sufficiently measuring chemical exposures and biological effects given the presence of complex and dynamic contaminant mixtures in surface waters. It is impractical to quantify all chemicals in such matrices over space and time, and even if it were practical, concomitant biological effects would not be elucidated. Our study examined the performance of the Daphnia magna transcriptome to detect distinct responses across three water sources in Minnesota: laboratory (well) waters, wetland waters, and storm waters. Pyriproxyfen was included as a gene expression and male neonate production positive control to examine whether gene expression resulting from exposure to this well-studied juvenoid hormone analog can be detected in complex matrices. Laboratory-reared (<24 h) D. magna were exposed to a water source and/or pyriproxyfen for 16 days to monitor phenotypic changes or 96 h to examine gene expression responses using Illumina HiSeq 2500 (10 million reads per library, 50-bp paired end [2 × 50]). The results indicated that a unique gene expression profile was produced for each water source. At 119 ng/L pyriproxyfen (~25% effect concentration) for male neonate production, as expected, the Doublesex1 gene was up-regulated. In descending order, gene expression patterns were most discernable with respect to pyriproxyfen exposure status, season of stormwater sample collection, and wetland quality, as indicated by the index of biological integrity. However, the biological implications of the affected genes were not broadly clear given limited genome resources for invertebrates. Our study provides support for the utility of short-term whole-organism transcriptomic testing in D. magna to discern sample type, but highlights the need for further work on invertebrate genomics. Environ Toxicol Chem 2022;41:2107-2123. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Prioritizing Pharmaceutical Contaminants in Great Lakes Tributaries Using Risk-Based Screening Techniques

In a study of 44 diverse sampling sites across 16 Great Lakes tributaries, 110 pharmaceuticals were detected of 257 monitored. The present study evaluated the ecological relevance of detected chemicals and identified heavily impacted areas to help inform resource managers and guide future investigations. Ten pharmaceuticals (caffeine, nicotine, albuterol, sulfamethoxazole, venlafaxine, acetaminophen, carbamazepine, gemfibrozil, metoprolol, and thiabendazole) were distinguished as having the greatest potential for biological effects based on comparison to screening-level benchmarks derived using information from two biological effects databases, the ECOTOX Knowledgebase and the ToxCast database. Available evidence did not suggest substantial concern for 75% of the monitored pharmaceuticals, including 147 undetected pharmaceuticals and 49 pharmaceuticals with screening-level alternative benchmarks. However, because of a lack of biological effects information, screening values were not available for 51 detected pharmaceuticals. Samples containing the greatest pharmaceutical concentrations and having the highest detection frequencies were from Lake Erie, southern Lake Michigan, and Lake Huron tributaries. Samples collected during low-flow periods had higher pharmaceutical concentrations than those collected during increased-flow periods. The wastewater-treatment plant effluent content in streams correlated positively with pharmaceutical concentrations. However, deviation from this correlation demonstrated that secondary factors, such as multiple pharmaceutical sources, were likely present at some sites. Further research could investigate high-priority pharmaceuticals as well as those for which alternative benchmarks could not be developed. Environ Toxicol Chem 2022;41:2221-2239. Published 2022. This article is a U.S. Government work and is in the public domain in the USA. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Advances in computational methods along the exposure to toxicological response paradigm

Human health risk assessment is a function of chemical toxicity, bioavailability to reach target biological tissues, and potential environmental exposure. These factors are complicated by many physiological, biochemical, physical and lifestyle factors. Furthermore, chemical health risk assessment is challenging in view of the large, and continually increasing, number of chemicals found in the environment. These challenges highlight the need to prioritize resources for the efficient and timely assessment of those environmental chemicals that pose greatest health risks. Computational methods, either predictive or investigative, are designed to assist in this prioritization in view of the lack of cost prohibitive in vivo experimental data. Computational methods provide specific and focused toxicity information using in vitro high throughput screening (HTS) assays. Information from the HTS assays can be converted to in vivo estimates of chemical levels in blood or target tissue, which in turn are converted to in vivo dose estimates that can be compared to exposure levels of the screened chemicals. This manuscript provides a review for the landscape of computational methods developed and used at the U.S. Environmental Protection Agency (EPA) highlighting their potentials and challenges.

Complex mixture toxicology: Evaluation of toxicity to freshwater aquatic receptors from biodegradation metabolites in groundwater at a crude oil release site, recent analogous results from other authors, and implications for risk management

Aquatic toxicity posed by the complex mixture of biodegradation metabolites and related oxygen-containing organic compounds (OCOCs) in groundwater at typical petroleum release sites is of concern to regulatory agencies; several are using results from laboratory studies in older literature that are not appropriate analogs for risk management. Recent field studies from typical sites and natural groundwater should be utilized. In this study, OCOCs downgradient of the biodegrading crude oil release at the USGS Bemidji site were tested for freshwater aquatic toxicity using unaltered whole groundwater samples. This type of testing is optimal because the entire mixture of OCOCs present is tested directly and assessment is not affected by analytical limitations. Ceriodaphnia dubia and Pimephales promelas were tested for toxicity using USEPA Methods 1002 and 1000, which estimate chronic toxicity. OCOCs in representative samples up to the maximum concentration tested of 1710 ug/L Total Petroleum Hydrocarbons (TPH) (nC10 to nC40; without silica gel cleanup) did not result in effects relative to the lab control for C. dubia survival, or for P. promelas survival or growth; and did not result in effects above background for C. dubia reproduction. This is consistent with findings using the same testing methods and species on samples from 14 biodegrading fuel release sites: OCOCs did not cause increased toxicity relative to background at a maximum tested concentration of 1800 ug/L TPH (nC10 to nC28). Based on their toxicity testing using the same species and USEPA methods on groundwater from a biodegrading diesel release site, Washington Department of Ecology recently set a freshwater screening level for OCOCs at 3000 ug/L TPH ("Weathered DRO"). These studies indicate that, in the absence of dissolved hydrocarbons, OCOCs in groundwater from typical biodegrading fuel or crude oil releases are not toxic to C. dubia or P. promelas at typical concentrations.

Identification of toxicity factors and causal analysis of toxicity in surface sediments from Liaohe river basin, Northeast China using an effect guidance strategy

Sediments play a pivotal role in maintaining the aquatic ecological status of rivers. However, the determination of the key toxicants that consider the combined effects of all sediment-related contaminants are still challenging and necessary for an appropriate sediment risk assessment. The effects of sediments on aquatic organisms have been reported in Liaohe River, but their key toxicity factors are not well known. To determine the key toxicity factors, twenty-six surface sediment samples from Liaohe River tributaries in Northeast China were collected. Acute toxicity test of midge larvae results showed that 6 of 26 tributaries had obvious toxic effects, with survival rates of 37%-57% (p < 0.05). The masking test showed that the main pollutants in the surface sediments of T7 and T16 were metals, that of T8 was an organic pollutant, those of T19 and T26 were organic pollutants and ammonia, and those of T17 were heavy metal and ammonia. Chemical analysis showed that the relatively high concentrations of ammonia were only presented in surface sediments of T17, T19, and T26, with PTU of 1.5, 1.2 and 1.1, respectively, whereas heavy metals were markedly high in surface sediments from T7 and T16, with PTU of 0.92 and 0.61, respectively. Interestingly, the observed toxicity in surface sediments agreed with the toxicity predicted by chemical analysis Moreover, the significant correlation between the survival and volume ratio of the sediment and overlying water confirmed ammonia nitrogen was key toxicity factor in T17, T19, and T26, whereas Cu was the key toxicity factor in T7 that cause the biological toxicity. In conclusion, the major toxic factors of ammonia and copper in the sediments were identified. Moreover, our study suggested that effect guidance strategy was an effective method for sediment quality assessment.

Risk-Based Prioritization of Organic Chemicals and Locations of Ecological Concern in Sediment From Great Lakes Tributaries

With improved analytical techniques, environmental monitoring studies are increasingly able to report the occurrence of tens or hundreds of chemicals per site, making it difficult to identify the most relevant chemicals from a biological standpoint. For the present study, organic chemical occurrence was examined, individually and as mixtures, in the context of potential biological effects. Sediment was collected at 71 Great Lakes (USA/Canada) tributary sites and analyzed for 87 chemicals. Multiple risk-based lines of evidence were used to prioritize chemicals and locations, including comparing sediment concentrations and estimated porewater concentrations with established whole-organism benchmarks (i.e., sediment and water quality criteria and screening values) and with high-throughput toxicity screening data from the US Environmental Protection Agency's ToxCast database, estimating additive effects of chemical mixtures on common ToxCast endpoints, and estimating toxic equivalencies for mixtures of alkylphenols and polycyclic aromatic hydrocarbons (PAHs). This multiple-lines-of-evidence approach enabled the screening of more chemicals, mitigated the uncertainties of individual approaches, and strengthened common conclusions. Collectively, at least one benchmark/screening value was exceeded for 54 of the 87 chemicals, with exceedances observed at all 71 of the monitoring sites. Chemicals with the greatest potential for biological effects, both individually and as mixture components, were bisphenol A, 4-nonylphenol, indole, carbazole, and several PAHs. Potential adverse outcomes based on ToxCast gene targets and putative adverse outcome pathways relevant to individual chemicals and chemical mixtures included tumors, skewed sex ratios, reproductive dysfunction, hepatic steatosis, and early mortality, among others. The results provide a screening-level prioritization of chemicals with the greatest potential for adverse biological effects and an indication of sites where they are most likely to occur. Environ Toxicol Chem 2022;41:1016-1041. Published 2022. This article is a U.S. Government work and is in the public domain in the USA. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Comprehensive assessment of NR ligand polypharmacology by a multiplex reporter NR assay

Nuclear receptors (NR) are ligand-modulated transcription factors that regulate multiple cell functions and thus represent excellent drug targets. However, due to a considerable NR structural homology, NR ligands often interact with multiple receptors. Here, we describe a multiplex reporter assay (the FACTORIAL NR) that enables parallel assessment of NR ligand activity across all 48 human NRs. The assay comprises one-hybrid GAL4-NR reporter modules transiently transfected into test cells. To evaluate the reporter activity, we assessed their RNA transcripts. We used a homogeneous RNA detection approach that afforded equal detection efficacy and permitted the multiplex detection in a single-well format. For validation, we examined a panel of selective NR ligands and polypharmacological agonists and antagonists of the progestin, estrogen, PPAR, ERR, and ROR receptors. The assay produced highly reproducible NR activity profiles (r > 0.96) permitting quantitative assessment of individual NR responses. The inferred EC50 values agreed with the published data. The assay showed excellent quality (<Z'>  = 0.73) and low variability (<CV> = 7.2%). Furthermore, the assay permitted distinguishing direct and non-direct NR responses to ligands. Therefore, the FACTORIAL NR enables comprehensive evaluation of NR ligand polypharmacology.

The Eco-Exposome Concept: Supporting an Integrated Assessment of Mixtures of Environmental Chemicals

Organisms are exposed to ever-changing complex mixtures of chemicals over the course of their lifetime. The need to more comprehensively describe this exposure and relate it to adverse health effects has led to formulation of the exposome concept in human toxicology. Whether this concept has utility in the context of environmental hazard and risk assessment has not been discussed in detail. In this Critical Perspective, we propose-by analogy to the human exposome-to define the eco-exposome as the totality of the internal exposure (anthropogenic and natural chemicals, their biotransformation products or adducts, and endogenous signaling molecules that may be sensitive to an anthropogenic chemical exposure) over the lifetime of an ecologically relevant organism. We describe how targeted and nontargeted chemical analyses and bioassays can be employed to characterize this exposure and discuss how the adverse outcome pathway concept could be used to link this exposure to adverse effects. Available methods, their limitations, and/or requirement for improvements for practical application of the eco-exposome concept are discussed. Even though analysis of the eco-exposome can be resource-intensive and challenging, new approaches and technologies make this assessment increasingly feasible. Furthermore, an improved understanding of mechanistic relationships between external chemical exposure(s), internal chemical exposure(s), and biological effects could result in the development of proxies, that is, relatively simple chemical and biological measurements that could be used to complement internal exposure assessment or infer the internal exposure when it is difficult to measure. Environ Toxicol Chem 2022;41:30-45. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Combining short-term bioassays using fish and crustacean model organisms with ToxCast in vitro data and broad-spectrum chemical analysis for environmental risk assessment of the river water (Sava, Croatia)

This study focused on the short-term whole organism bioassays (WOBs) on fish (Danio rerio) and crustaceans (Gammarus fossarum and Daphnia magna) to assess the negative biological effects of water from the major European River Sava and the comparison of the obtained results with in vitro toxicity data (ToxCast database) and Risk Quotient (RQ) methodology. Pollution profiles of five sampling sites along the River Sava were assessed by simultaneous chemical analysis of 562 organic contaminants (OCs) of which 476 were detected. At each sampling site, pharmaceuticals/illicit drugs category was mostly represented by their cumulative concentration, followed by categories industrial chemicals, pesticides and hormones. An exposure-activity ratio (EAR) approach based on ToxCast data highlighted steroidal anti-inflammatory drugs, antibiotics, antiepileptics/neuroleptics, industrial chemicals and hormones as compounds with the highest biological potential. Summed EAR-based prediction of toxicity showed a good correlation with the estimated toxicity of assessed sampling sites using WOBs. WOBs did not exhibit increased mortality but caused various sub-lethal biological responses that were dependant relative to the sampling site pollution intensity as well as species sensitivity. Exposure of G. fossarum and D. magna to river water-induced lower feeding rates increased GST activity and TBARS levels. Zebrafish D. rerio embryo exhibited a significant decrease in heartbeat rate, failure in pigmentation formation, as well as inhibition of ABC transporters. Nuclear receptor activation was indicated as the biological target of greatest concern based on the EAR approach. A combined approach of short-term WOBs, with a special emphasis on sub-lethal endpoints, and chemical characterization of water samples compared against in vitro toxicity data from the ToxCast database and RQs can provide a comprehensive insight into the negative effect of pollutants on aquatic organisms.

Cytotoxic and Transcriptomic Effects in Avian Hepatocytes Exposed to a Complex Mixture from Air Samples, and Their Relation to the Organic Flame Retardant Signature

Assessing complex environmental mixtures and their effects is challenging. In this study, we evaluate the utility of an avian in vitro screening approach to determine the effects of passive air sampler extracts collected from different global megacities on cytotoxicity and gene expression. Concentrations of a suite of organic flame retardants (OFRs) were quantified in extracts from a total of 19 megacities/major cities in an earlier study, and levels were highly variable across sites. Chicken embryonic hepatocytes were exposed to serial dilutions of extracts from the 19 cities for 24 h. Cell viability results indicate a high level of variability in cytotoxicity, with extracts from Toronto, Canada, having the lowest LC50 value. Partial least squares (PLS) regression analysis was used to estimate LC50 values from OFR concentrations. PLS modeling of OFRs was moderately predictive of LC50 (p-value = 0.0003, r² = 0.66, slope = 0.76, when comparing predicted LC50 to actual values), although only after one outlier city was removed from the analysis. A chicken ToxChip PCR array, comprising 43 target genes, was used to determine effects on gene expression, and similar to results for cell viability, gene expression profiles were highly variable among the megacities. PLS modeling was used to determine if gene expression was related to the OFR profiles of the extracts. Weak relationships to the ToxChip expression profiles could be detected for only three of the 35 OFRs (indicated by regression slopes between 0.6 and 0.5 when comparing predicted to actual OFR concentrations). While this in vitro approach shows promise in terms of evaluating effects of complex mixtures, we also identified several limitations that, if addressed in future studies, might improve its performance.

Effects-based monitoring of bioactive compounds associated with municipal wastewater treatment plant effluent discharge to the South Platte River, Colorado, USA

Previous studies have detected numerous organic contaminants and in vitro bioactivities in surface water from the South Platte River near Denver, Colorado, USA. To evaluate the temporal and spatial distribution of selected contaminants of emerging concern, water samples were collected throughout 2018 and 2019 at 11 sites within the S. Platte River and surrounding tributaries with varying proximities to a major wastewater treatment plant (WWTP). Water samples were analyzed for pharmaceuticals, pesticides, steroid hormones, and wastewater indicators and screened for in vitro biological activities. Multiplexed, in vitro assays that simultaneously screen for agonistic activity against 24 human nuclear receptors detected estrogen receptor (ER), peroxisome proliferator activated receptor-gamma (PPARγ), and glucocorticoid receptor (GR) bioactivities in water samples near the WWTP outflow. Targeted in vitro bioassays assessing ER, GR, and PPARγ agonism corroborated bioactivities for ER (up to 55 ± 9.7 ng/L 17β-estradiol equivalents) and GR (up to 156 ± 28 ng/L dexamethasone equivalents), while PPARγ activity was not confirmed. To evaluate the potential in vivo significance of the bioactive contaminants, sexually-mature fathead minnows were caged at six locations upstream and downstream of the WWTP for 5 days after which targeted gene expression analyses were performed. Significant up-regulation of male hepatic vitellogenin was observed at sites with corresponding in vitro ER activity. No site-related differences in GR-related transcript abundance were detected in female adipose or male livers, suggesting observed environmental concentrations of GR-active contaminants do not induce a detectable in vivo response. In line with the lack of detectable targeted in vitro PPARɣ activity, there were no significant effects on PPARɣ-related gene expression. Although the chemicals responsible for GR and PPAR-mediated bioactivities are unknown, results from the present study provide insights into the significance (or lack thereof) of these bioactivities relative to short-term in situ fish exposures.

Comparing conventional and green fracturing fluids by chemical characterisation and effect-based screening

There is public and scientific concern about air, soil and water contamination and possible adverse environmental and human health effects as a result of hydraulic fracturing activities. The use of greener chemicals in fracturing fluid aims to mitigate these effects. This study compares fracturing fluids marketed as either 'conventional' or 'green', as assessed by their chemical composition and their toxicity in bioassays. Chemical composition was analysed via non-target screening using liquid chromatography - high resolution mass spectrometry, while toxicity was evaluated by the Ames fluctuation test to assess mutagenicity and CALUX reporter gene assays to determine specific toxicity. Overall, the results do not indicate that the 'green' fluids are less harmful than the 'conventional' ones. First, there is no clear indication that the selected green fluids contain chemicals present at lower concentrations than the selected conventional fluids. Second, the predicted environmental fate of the identified compounds does not seem to be clearly distinct between the 'green' and 'conventional' fluids, based on the available data for the top five chemicals based on signal intensity that were tentatively identified. Furthermore, Ames fluctuation test results indicate that the green fluids have a similar genotoxic potential than the conventional fluids. Results of the CALUX reporter gene assays add to the evidence that there is no clear difference between the green and conventional fluids. These results do not support the claim that currently available and tested green-labeled fracturing fluids are environmentally more friendly alternatives to conventional fracturing fluids.

Orbitrap ESI-MS evaluation of solvent extractable organics from a crude oil release site

The concentrations of oxygen-containing organic compounds (OCOC), measured as dissolved organic carbon (DOC), in groundwater exceeds those of dissolved hydrocarbons, measured as total petroleum hydrocarbons (TPH), at a crude oil release site. Orbitrap mass spectrometry was used to characterize OCOC in samples of the oil, water from upgradient of the release, source area, and downgradient wells, and a local lake. Chemical characterization factors included carbon number, oxygen number, formulae similarity, double bond equivalents (DBE) and radiocarbon dating. Oil samples were dominated by formulae with less than 30 carbons, four or fewer oxygens, and a DBE of less than four. In water samples, formulae were identified with more than 30 carbons, more than 10 oxygens, and a DBE exceeding 30. These characteristics are consistent with DOC found in unimpacted water. Between 65% and 92% of the formulae found in samples collected within the elevated OCOC plume were also found in the upgradient or surface water samples. Evidence suggests that many of the OCOC are not petroleum degradation intermediates, but microbial products generated as a result of de novo synthesis by organisms growing on carbon supplied by the oil. Implications of these results for understanding the fate and managing the risk of hydrocarbons in the subsurface are discussed.

Effects of conventionally-treated and ozonated wastewater on mortality, physiology, body length, and behavior of embryonic and larval zebrafish (Danio rerio)

To date, micropollutants from anthropogenic sources cannot be completely removed from effluents of wastewater treatment plants and therefore enter freshwater systems, where they may impose adverse effects on aquatic organisms, for example, on fish. Advanced treatment such as ozonation aims to reduce micropollutants in wastewater effluents and, thus, to mitigate adverse effects on the environment. To investigate the impact and efficiency of ozonation, four different water types were tested: ozonated wastewater (before and after biological treatment), conventionally-treated wastewater, and water from a river (River Ruhr, Germany) upstream of the wastewater treatment plant effluent. Zebrafish (Danio rerio) embryos were used to study lethal and sublethal effects in a modified fish early life-stage test. Mortality occurred during exposure in the water samples from the wastewater treatment plant and the river in the first 24 h post-fertilization, ranging from 12% (conventional wastewater) to 40% (river water). Regarding sublethal endpoints, effects compared to the negative control resulted in significantly higher heart rates (ozonated wastewater), and significantly reduced swimming activity (highly significant in ozonated wastewater and ozone reactor water, significant in only the last time interval in river water). Moreover, the respiration rates were highly increased in both ozonated wastewater samples in comparison to the negative control. Significant differences between the ozonated wastewater samples occurred in the embryonic behavior and heart rates, emphasizing the importance of subsequent biological treatment of the ozonated wastewater. Only the conventionally-treated wastewater sample did not elicit negative responses in zebrafish, indicating that the discharge of conventional wastewater poses no greater risk to embryonic and larval zebrafish than water from the river Ruhr itself. The sublethal endpoints embryonic- and larval behavior, heart rates, and respiration were found to be the most sensitive endpoints in this fish early life-stage test and can add valuable information on the toxicity of environmental samples.

Risk Characterization of Environmental Samples Using In Vitro Bioactivity and Polycyclic Aromatic Hydrocarbon Concentrations Data

Methods to assess environmental exposure to hazardous chemicals have primarily focused on quantification of individual chemicals, although chemicals often occur in mixtures, presenting challenges to the traditional risk characterization framework. Sampling sites in a defined geographic region provide an opportunity to characterize chemical contaminants, with spatial interpolation as a tool to provide estimates for non-sampled sites. At the same time, the use of in vitro bioactivity measurements has been shown to be informative for rapid risk-based decisions. In this study, we measured in vitro bioactivity in 39 surface soil samples collected immediately after flooding associated with Hurricane Harvey in Texas in a residential area known to be inundated with polycyclic aromatic hydrocarbon (PAH) contaminants. Bioactivity data were from a number of functional and toxicity assays in 5 human cell types, such as induced pluripotent stem cell-derived hepatocytes, cardiomyocytes, neurons, and endothelial cells, as well as human umbilical vein endothelial cells. Data on concentrations of PAH in these samples were also available and the combination of data sources offered a unique opportunity to assess the joint spatial variation of PAH components and bioactivity. We found significant evidence of spatial correlation of a subset of PAH contaminants and of cell-based phenotypes. In addition, we show that the cell-based bioactivity data can be used to predict environmental concentrations for several PAH contaminants, as well as overall PAH summaries and cancer risk. This study's impact lies in its demonstration that cell-based profiling can be used for rapid hazard screening of environmental samples by anchoring the bioassays to concentrations of PAH. This work sets the stage for identification of the areas of concern and direct quantitative risk characterization based on bioactivity data, thereby providing an important supplement to traditional individual chemical analyses by shedding light on constituents that may be missed from targeted chemical monitoring.

Identifying Chemicals and Mixtures of Potential Biological Concern Detected in Passive Samplers from Great Lakes Tributaries Using High-Throughput Data and Biological Pathways

Waterborne contaminants were monitored in 69 tributaries of the Laurentian Great Lakes in 2010 and 2014 using semipermeable membrane devices (SPMDs) and polar organic chemical integrative samplers (POCIS). A risk-based screening approach was used to prioritize chemicals and chemical mixtures, identify sites at greatest risk for biological impacts, and identify potential hazards to monitor at those sites. Analyses included 185 chemicals (143 detected) including polycyclic aromatic hydrocarbons (PAHs), legacy and current-use pesticides, fire retardants, pharmaceuticals, and fragrances. Hazard quotients were calculated by dividing detected concentrations by biological effect concentrations reported in the ECOTOX Knowledgebase (toxicity quotients) or ToxCast database (exposure-activity ratios [EARs]). Mixture effects were estimated by summation of EAR values for chemicals that influence ToxCast assays with common gene targets. Nineteen chemicals-atrazine, N,N-diethyltoluamide, di(2-ethylhexyl)phthalate, dl-menthol, galaxolide, p-tert-octylphenol, 3 organochlorine pesticides, 3 PAHs, 4 pharmaceuticals, and 3 phosphate flame retardants-had toxicity quotients >0.1 or EARs for individual chemicals >10^-3 at 10% or more of the sites monitored. An additional 4 chemicals (tributyl phosphate, triethyl citrate, benz[a]anthracene, and benzo[b]fluoranthene) were present in mixtures with EARs >10^-3 . To evaluate potential apical effects and biological endpoints to monitor in exposed wildlife, in vitro bioactivity data were compared to adverse outcome pathway gene ontology information. Endpoints and effects associated with endocrine disruption, alterations in xenobiotic metabolism, and potentially neuronal development would be relevant to monitor at the priority sites. The EAR threshold exceedance for many chemical classes was correlated with urban land cover and wastewater effluent influence, whereas herbicides and fire retardants were also correlated to agricultural land cover. Environ Toxicol Chem 2021;40:2165-2182. Published 2021. This article is a U.S. Government work and is in the public domain in the USA. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Untargeted Lipidomics for Determining Cellular and Subcellular Responses in Zebrafish (Danio rerio) Liver Cells Following Exposure to Complex Mixtures in U.S. Streams

Surface waters often contain a variety of chemical contaminants potentially capable of producing adverse outcomes in both humans and wildlife due to impacts from industrial, urban, and agricultural activity. Here, we report the results of a zebrafish liver (ZFL) cell-based lipidomics approach to assess the potential ecotoxicological effects of complex contaminant mixtures using water collected from eight impacted streams across the United States mainland and Puerto Rico. We initially characterized the ZFL lipidome using high resolution mass spectrometry, resulting in the annotation of 508 lipid species covering 27 classes. We then identified lipid changes induced by all streamwater samples (nonspecific stress indicators) as well as those unique to water samples taken from specific streams. Subcellular impacts were classified based on organelle-specific lipid changes, including increased lipid saturation (endoplasmic reticulum stress), elevated bis(monoacylglycero)phosphate (lysosomal overload), decreased ubiquinone (mitochondrial dysfunction), and elevated ether lipids (peroxisomal stress). Finally, we demonstrate how these results can uniquely inform environmental monitoring and risk assessments of surface waters.

In vitro effects-based method and water quality screening model for use in pre- and post-distribution treated waters

Recent urban public water supply contamination events emphasize the importance of screening treated drinking water quality after distribution. In vitro bioassays, when run concurrently with analytical chemistry methods, are effective tools to evaluating the efficacy of water treatment processes and water quality. We tested 49 water samples representing the Chicago Department of Water Management service areas for estrogen, (anti)androgen, glucocorticoid receptor-activating contaminants and cytotoxicity. We present a tiered screening approach suitable to samples with anticipated low-level activity and initially tested all extracts for statistically identifiable endocrine activity; performing a secondary dilution-response analysis to determine sample EC₅₀ and biological equivalency values (BioEq). Estrogenic activity was detected in untreated Lake Michigan intake water samples using mammalian (5/49; median: 0.21 ng E2Eq/L) and yeast cell (5/49; 1.78 ng E2Eq/L) bioassays. A highly sensitive (anti)androgenic activity bioassay was applied for the first time to water quality screening and androgenic activity was detected in untreated intake and treated pre-distribution samples (4/49; 0.93 ng DHTEq/L). No activity was identified above method detection limits in the yeast androgenic, mammalian anti-androgenic, and both glucocorticoid bioassays. Known estrogen receptor agonists were detected using HPLC/MS-MS (estrone: 0.72-1.4 ng/L; 17α-estradiol: 1.3-1.5 ng/L; 17β-estradiol: 1.4 ng/L; equol: 8.8 ng/L), however occurrence did not correlate with estrogenic bioassay results. Many studies have applied bioassays to water quality monitoring using only relatively small samples sets often collected from surface and/or wastewater effluent. However, to realistically adapt these tools to treated water quality monitoring, water quality managers must have the capacity to screen potentially hundreds of samples in short timeframes. Therefore, we provided a tiered screening model that increased sample screening speed, without sacrificing statistical stringency, and detected estrogenic and androgenic activity only in pre-distribution Chicago area samples.

Environmental Risk of Pesticides for Fish in Small- and Medium-Sized Streams of Switzerland

This study assessed the acute and chronic risk of pesticides, singly and as mixtures, for fish using comprehensive chemical data of four monitoring studies conducted in small- and medium-sized streams of Switzerland between 2012 and 2018. Pesticides were ranked based on single substance risk quotients and relative contribution to mixture risk. Concentrations of the pyrethroid insecticides, λ-cyhalothrin, cypermethrin and deltamethrin, and the fungicides, carbendazim and fenpropimorph, posed acute or chronic single substance risks. Risk quotients of eighteen additional pesticides were equal or greater than 0.1, and thirteen of those contributed ≥30% to mixture risk. Relatively few substances dominated the mixture risk in most water samples, with chronic and acute maximum cumulative ratios never exceeding 5 and 7, respectively. A literature review of toxicity data showed that concentrations of several pesticides detected in Swiss streams were sufficient to cause direct sublethal effects on fish in laboratory studies. Based on the results of our study, we conclude that pesticides detected in Swiss streams, especially pyrethroid insecticides, fungicides and pesticide mixtures, pose a risk to fish health and can cause direct sublethal effects at environmental concentrations. Sensitive life stages of species with highly specialized life history traits may be particularly vulnerable; however, the lack of toxicity data for non-model species currently prevents a conclusive assessment across species.

Pathway-Based Approaches for Assessing Biological Hazards of Complex Mixtures of Contaminants: A Case Study in the Maumee River

Assessment of ecological risks of chemicals in the field usually involves complex mixtures of known and unknown compounds. We describe the use of pathway-based chemical and biological approaches to assess the risk of chemical mixtures in the Maumee River (OH, USA), which receives a variety of agricultural and urban inputs. Fathead minnows (Pimephales promelas) were deployed in cages for 4 d at a gradient of sites along the river and adjoining tributaries in 2012 and during 2 periods (April and June) in 2016, in conjunction with an automated system to collect composite water samples. More than 100 industrial chemicals, pharmaceuticals, and pesticides were detected in water at some of the study sites, with the greatest number typically found near domestic wastewater treatment plants. In 2016, there was an increase in concentrations of several herbicides from April to June at upstream agricultural sites. A comparison of chemical concentrations in site water with single chemical data from vitro high-throughput screening (HTS) assays suggested the potential for perturbation of multiple biological pathways, including several associated with induction or inhibition of different cytochrome P450 (CYP) isozymes. This was consistent with direct effects of water extracts in an HTS assay and induction of hepatic CYPs in caged fish. Targeted in vitro assays and measurements in the caged fish suggested minimal effects on endocrine function (e.g., estrogenicity). A nontargeted mass spectroscopy-based analysis suggested that hepatic endogenous metabolite profiles in caged fish covaried strongly with the occurrence of pesticides and pesticide degradates. These studies demonstrate the application of an integrated suite of measurements to help understand the effects of complex chemical mixtures in the field. Environ Toxicol Chem 2021;40:1098-1122. © 2020 SETAC. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Toxicity Testing of Effluent-Dominated Stream Using Predictive Molecular-Level Toxicity Signatures Based on High-Resolution Mass Spectrometry: A Case Study of the Lubbock Canyon Lake System

Current aquatic toxicity assessments usually focus on targeted analyses coupled with toxicity testing to determine the impacts of complex mixtures on aquatic organisms. However, based on this approach alone, it is sometimes difficult to explain observed toxicity from the selected chemical analytes. Recent analytical advances such as high-resolution mass spectrometry (HRMS) can improve the characterizations of the chemical composition of complex mixtures, but the intensive labor required to produce confident identifications limits its utility in high-throughput screening. In the present study, we evaluated a rapid workflow to predict potential toxicity signatures of complex water samples based on high-throughput, tentative HRMS identifications derived from database matching, followed by identification of chemical-ligand interactions and pathway identification. We tested the workflow with water samples from the effluent-dominated Lubbock Canyon Lake System (LCLS). Results across all sites showed that predicted toxicity signatures had little variation when correcting for HRMS false-positive rates. The most common pathways across sites were gonadotropin-releasing hormone receptor and α-adrenergic receptor signaling. Alterations to the predicted pathways were successfully observed in larval zebrafish exposures to LCLS water samples. These results may allow researchers to better utilize rapid assessments of HRMS data for the assessment of adverse impacts on aquatic organisms.

Assessing the Ecological Risks of Per- and Polyfluoroalkyl Substances: Current State-of-the Science and a Proposed Path Forward

Per- and poly-fluoroalkyl substances (PFAS) encompass a large, heterogenous group of chemicals of potential concern to human health and the environment. Based on information for a few relatively well-understood PFAS such as perfluorooctane sulfonate and perfluorooctanoate, there is ample basis to suspect that at least a subset can be considered persistent, bioaccumulative, and/or toxic. However, data suitable for determining risks in either prospective or retrospective assessments are lacking for the majority of PFAS. In August 2019, the Society of Environmental Toxicology and Chemistry sponsored a workshop that focused on the state-of-the-science supporting risk assessment of PFAS. The present review summarizes discussions concerning the ecotoxicology and ecological risks of PFAS. First, we summarize currently available information relevant to problem formulation/prioritization, exposure, and hazard/effects of PFAS in the context of regulatory and ecological risk assessment activities from around the world. We then describe critical gaps and uncertainties relative to ecological risk assessments for PFAS and propose approaches to address these needs. Recommendations include the development of more comprehensive monitoring programs to support exposure assessment, an emphasis on research to support the formulation of predictive models for bioaccumulation, and the development of in silico, in vitro, and in vivo methods to efficiently assess biological effects for potentially sensitive species/endpoints. Addressing needs associated with assessing the ecological risk of PFAS will require cross-disciplinary approaches that employ both conventional and new methods in an integrated, resource-effective manner. Environ Toxicol Chem 2021;40:564-605. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. This article has been contributed to by US Government employees and their work is in the public domain in the USA.

Assessment of source and treated water quality in seven drinking water treatment plants by in vitro bioassays - Oxidative stress and antiandrogenic effects after artificial infiltration

Drinking water quality and treatment efficacy was investigated in seven drinking water treatment plants (DWTPs), using water from the river Göta Älv, which also is a recipient of treated sewage water. A panel of cell-based bioassays was used, including measurements of receptor activity of aryl hydrocarbon (AhR), estrogen (ER), androgen (AR), peroxisome proliferator-activated receptor alpha (PPARα) as well as induction of oxidative stress (Nrf2) and micronuclei formation. Grab water samples were concentrated by solid phase extraction (SPE) and water samples were analyzed at a relative enrichment factor of 50. High activities of AhR, ER and AR antagonism were present in WWTP outlets along the river. Inlet water from the river exhibited AhR and AR antagonistic activities. AhR activity was removed by DWTPs using granulated activated carbon (GAC) and artificial infiltration. AR antagonistic activity was removed by the treatment plants, except the artificial infiltration plant, which actually increased the activity. Furthermore, treated drinking water from the DWTP using artificial infiltration exhibited high Nrf2 activity, which was not found in any of the other water samples. Nrf2 activity was found in water from eight of the 13 abstraction wells, collecting water from the artificial infiltration. No genotoxic activity was detected at non-cytotoxic concentrations. No Nrf2 or AR antagonistic activities were detected in the inlet or outlet water after the DWTP had been replaced by a new plant, using membrane ultrafiltration and GAC. Neither target chemical analysis, nor chemical analysis according to the drinking water regulation, detected any presence of chemicals, which could be responsible of the prominent effects on oxidative stress and AR antagonistic activity in the drinking water samples. Thus, bioanalysis is a useful tool for detection of unknown hazards in drinking water and for assessment of drinking water treatments.

Effect-Based Trigger Values for Mixtures of Chemicals in Surface Water Detected with In Vitro Bioassays

Effect-based trigger (EBT) values for in vitro bioassays are important for surface water quality monitoring because they define the threshold between acceptable and poor water quality. They have been derived for highly specific bioassays, such as hormone-receptor activation in reporter gene bioassays, by reading across from existing chemical guideline values. This read-across method is not easily applicable to bioassays indicative of adaptive stress responses, which are triggered by many different chemicals, and activation of nuclear receptors for xenobiotic metabolism, to which many chemicals bind with rather low specificity. We propose an alternative approach to define the EBT from the distribution of specificity ratios of all active chemicals. The specificity ratio is the ratio between the predicted baseline toxicity of a chemical in a given bioassay and its measured specific endpoint. Unlike many previous read-across methods to derive EBTs, the proposed method accounts for mixture effects and includes all chemicals, not only high-potency chemicals. The EBTs were derived from a cytotoxicity EBT that was defined as equivalent to 1% of cytotoxicity in a native surface water sample. The cytotoxicity EBT was scaled by the median of the log-normal distribution of specificity ratios to derive the EBT for effects specific for each bioassay. We illustrate the new approach using the example of the AREc32 assay, indicative of the oxidative stress response, and 2 nuclear receptor assays targeting the peroxisome proliferator-activated receptor gamma and the arylhydrocarbon receptor. The EBTs were less conservative than previously proposed but were able to differentiate untreated and insufficiently treated wastewater from wastewater treatment plant effluent with secondary or tertiary treatment and surface water. Environ Toxicol Chem 2021;40:487-499. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Effects-Based Monitoring of Bioactive Chemicals Discharged to the Colorado River before and after a Municipal Wastewater Treatment Plant Replacement

Monitoring of the Colorado River near the Moab, Utah, wastewater treatment plant (WWTP) outflow has detected pharmaceuticals, hormones, and estrogen-receptor (ER)-, glucocorticoid receptor (GR)-, and peroxisome proliferator-activated receptor-gamma (PPARγ)-mediated biological activities. The aim of the present multi-year study was to assess effects of a WWTP replacement on bioactive chemical (BC) concentrations. Water samples were collected bimonthly, pre- and post-replacement, at 11 sites along the Colorado River upstream and downstream of the WWTP and analyzed for in vitro bioactivities (e.g., agonism of ER, GR, and PPARγ) and BC concentrations; fathead minnows were cage deployed pre- and post-replacement at sites with varying proximities to the WWTP. Before the WWTP replacement, in vitro ER (24 ng 17β-estradiol equivalents/L)-, GR (60 ng dexamethasone equivalents/L)-, and PPARγ-mediated activities were detected at the WWTP outflow but diminished downstream. In March 2018, the WWTP effluent was acutely toxic to the fish, likely due to elevated ammonia concentrations. Following the WWTP replacement, ER, GR, and PPARγ bioactivities were reduced by approximately 60-79%, no toxicity was observed in caged fish, and there were marked decreases in concentrations of many BCs. Results suggest that replacement of the Moab WWTP achieved a significant reduction in BC concentrations to the Colorado River.