Assessing the Mixture Effects in In Vitro Bioassays of Chemicals Occurring in Small Agricultural Streams during Rain Events

Effect-directed analysis of endocrine and neurotoxic effects in stormwater depending discharges

The investigation of pollutant inputs via stormwater runoff and subsequent effects in receiving waters is becoming increasingly urgent in view of climate change with accompanying extreme weather situations such as heavy rainfall events. In this study, two sampling areas, one urban and one rural but dominated by a highway, were investigated using effect-directed analysis to identify endocrine and neurotoxic effects and potentially responsible substances in stormwater structures and receiving waters. For this purpose, a transgenic yeast cell assay for the simultaneous detection of estrogenic, androgenic, and progestogenic effects (YMEES) was performed directly on high-performance thin-layer chromatography (HPTLC) plates. Concomitantly, estrogens were analyzed by GC-MS/MS and other micropollutants typical for wastewater and stormwater by LC-MS/MS. Discharges from the combined sewer overflow (CSO) contribute a large portion of the endocrine load to the studied water body, even surpassing the load from a nearby wastewater treatment plant (WWTP). An effect pattern similar to the CSO sample was shown in the receiving water after the CSO with lower intensities, consisting of an estrogenic, androgenic, and progestogenic effect. In contrast, after the WWTP, only one estrogenic effect with a lower intensity was detected. Concentrations of E1, 17α-E2, 17β-E2, EE2, and E3 in the CSO sample were 2000, 410, 1100, 560, and 2700 pg/L, respectively. HPTLC-YMEES and GC-MS/MS complement each other very well and help to elucidate endocrine stresses. An Acetylcholinesterase (AChE) inhibitory effect could not be assigned to a causative compound by suspect and non-target analysis using LC-HRMS. However, the workflow showed how information from HPTLC separation, effect-based methods, and other meta-information on the sampling area and substance properties can contribute to an identification of effect-responsible substances. Overall, the study demonstrated that effect-based methods in combination with HPTLC and instrumental analysis can be implemented to investigate pollution by stormwater run-off particularly regarding heavy rain events due to climate change.

Neurotoxic mixture effects of chemicals extracted from blood of pregnant women

Human biomonitoring studies typically capture only a small and unknown fraction of the entire chemical universe. We combined chemical analysis with a high-throughput in vitro assay for neurotoxicity to capture complex mixtures of organic chemicals in blood. Plasma samples of 624 pregnant women from the German LiNA cohort were extracted with a nonselective extraction method for organic chemicals. 294 of >1000 target analytes were detected and quantified. Many of the detected chemicals as well as the whole extracts interfered with neurite development. Experimental testing of simulated complex mixtures of detected chemicals in the neurotoxicity assay confirmed additive mixture effects at concentrations less than individual chemicals' effect thresholds. The use of high-throughput target screening combined with bioassays has the potential to improve human biomonitoring and provide a new approach to including mixture effects in epidemiological studies.

Adaption and application of cell-based bioassays to whole-water samples

The increasing presence of contaminants of emerging concern in wastewater and their potential environmental risks require improved monitoring and analysis methods. Direct toxicity assessment (DTA) using bioassays can complement chemical analysis of wastewater discharge, but traditional in vivo tests have ethical considerations and are expensive, low-throughput, and limited to apical endpoints (mortality, reproduction, development, and growth). In vitro bioassays offer an alternative approach that is cheaper, faster, and more ethical, and can provide higher sensitivity for some environmentally relevant endpoints. This study explores the potential benefits of using whole water samples of wastewater and environmental surface water instead of traditional solid phase extraction (SPE) methods for in vitro bioassays testing. Whole water samples produced a stronger response in most bioassays, likely due to the loss or alteration of contaminants during SPE sample extraction. In addition, there was no notable difference in results for most bioassays after freezing whole water samples, which allows for increased flexibility in testing timelines and cost savings. These findings highlight the potential advantages of using whole water samples in DTA and provide a framework for future research in this area.

Application of in vitro bioassays to monitor pharmaceuticals in water: A synthesis of chronological analysis, mode of action, and practical insights

Pharmaceutical compounds in wastewater have emerged as a significant concern for the aquatic environment. The use of in vitro bioassays represents a sustainable and cost-effective approach for assessing the potential toxicological risks of these biologically active compounds in wastewater and aligns with ethical considerations in research. It facilitates high-throughput analysis, captures mixture effects, integrates impacts of both known and unknown chemicals, and reduces reliance on animal testing. The core aim of the current review was to explore the practical application of in vitro bioassays in evaluating the environmental impacts of pharmaceuticals in wastewater. This comprehensive review strives to achieve several key objectives. First, it provides a summary categorisation of pharmaceuticals based on their mode of action, providing a structured framework for understanding their ecological significance. Second, a chronological analysis of pharmaceutical research aims to document their prevalence and trends over time, shedding light on evolving environmental challenges. Third, the review critically analyses existing bioassay applications in wastewater, while also examining bioassay coverage of representative compounds within major pharmaceutical classes. Finally, it explores the potential for developing innovative bioassays tailored for water quality monitoring of pharmaceuticals, paving the way for more robust environmental monitoring and risk assessment. Overall, adopting effect-based methods for pharmaceutical monitoring in water holds significant promise. It encompasses a broad spectrum of biological impacts, promotes standardized protocols, and supports a bioassay test battery approach indicative of different endpoints, thereby enhancing the effectiveness of environmental risk assessment.

Macroinvertebrate communities respond strongly but non-specifically to a toxicity gradient derived by effect-based methods

Chemical pollution is one of the most important threats to freshwater ecosystems. The plethora of potentially occurring chemicals and their effects in complex mixtures challenge standard monitoring methods. Effect-based methods (EBMs) are proposed as complementary tools for the assessment of chemical pollution and toxic effects. To investigate the effects of chemical pollution, the ecological relevance of EBMs and the potential of macroinvertebrates as toxicity-specific bioindicators, ecological and ecotoxicological data were linked. Baseline toxicity, mutagenicity, dioxin-like and estrogenic activity of water and sediment samples from 30 river sites in central Germany were quantified with four in vitro bioassays. The responses of macroinvertebrate communities at these sites were assessed by calculating 16 taxonomic and functional metrics and by investigating changes in the taxonomic and trait composition. Principal component analysis revealed an increase in toxicity along a joint gradient of chemicals with different modes of action. This toxicity gradient was associated with a decrease in biodiversity and ecological quality, as well as significant changes in taxonomic and functional composition. The strength of the effects suggested a strong impact of chemical pollution and underlined the suitability of EBMs in detecting ecological relevant effects. However, the metrics, taxa, and traits associated with vulnerability or tolerance to toxicity were found to also respond to other stressors in previous studies and thus may have only a low potential as toxicity-specific bioindicators. Because macroinvertebrates respond integratively to all present stressors, linking both ecological and environmental monitoring is necessary to investigate the overall effects but also isolate individual stressors. EBMs have a high potential to separate the toxicity of chemical mixtures from other stressors in a multiple stressor scenario, as well as identifying the presence of chemical groups with specific modes of action.

Endocrine disrupting potential of total and bioaccessible extracts of dust from seven different types of indoor environment

Information on the indoor environment as a source of exposure with potential adverse health effects is mostly limited to a few pollutant groups and indoor types. This study provides a comprehensive toxicological profile of chemical mixtures associated with dust from various types of indoor environments, namely cars, houses, prefabricated apartments, kindergartens, offices, public spaces, and schools. Organic extracts of two different polarities and bioaccessible extracts mimicking the gastrointestinal conditions were prepared from two different particle size fractions of dust. These extracts were tested on a battery of human cell-based bioassays to assess endocrine disrupting potentials. Furthermore, 155 chemicals from different pollutant groups were measured and their relevance for the bioactivity was determined using concentration addition modelling. The exhaustive and bioaccessible extracts of dust from the different microenvironments interfered with aryl hydrocarbon receptor, estrogen, androgen, glucocorticoid, and thyroid hormone (TH) receptor signalling, and with TH transport. Noteably, bioaccessible extracts from offices and public spaces showed higher estrogenic effects than the organic solvent extracts. 114 of the 155 targeted chemicals were detectable, but the observed bioactivity could be only marginally explained by the detected chemicals. Diverse toxicity patterns across different microenvironments that people inhabit throughout their lifetime indicate potential health and developmental risks, especially for children. Limited data on the endocrine disrupting potency of relevant chemical classes, especially those deployed as replacements for legacy contaminants, requires further study.

Trace organic contaminants in lake waters: Occurrence and environmental risk assessment at the national scale in Canada

Numerous contaminants are produced and used daily, a significant fraction ultimately finding their way into natural waters. However, data on their distribution in lakes is lacking. To address this gap, the presence of 54 trace organic contaminants (TrOCs), representative of various human activities, was investigated in the surface water of 290 lakes across Canada. These lakes ranged from remote to highly impacted by human activities. In 88% of the sampled lakes, contaminants were detected, with up to 28 detections in a single lake. The compounds most frequently encountered were atrazine, cotinine, and deethylatrazine, each of which was present in more than a third of the lakes. The range of detected concentrations was from 0.23 ng/L to about 2200 ng/L for individual compounds, while the maximum cumulative concentration exceeded 8100 ng/L in a single lake. A risk assessment based on effect concentrations for three aquatic species (Pimephales promelas, Daphnia magna, and Tetrahymena pyriformis) was conducted, revealing that 6% of lakes exhibited a high potential risk for at least one species. In 59% of lakes, some contaminants with potential sub-lethal effects were detected, with the detection of up to 17 TrOCs with potential impacts. The results of this work provide the first reference point for monitoring the evolution of contamination in Canadian lakes by TrOCs. They demonstrate that a high proportion of the sampled lakes bear an environmentally relevant anthropogenic chemical footprint.

A multi-scenario risk assessment strategy applied to mixtures of chemicals of emerging concern in the River Aconcagua basin in Central Chile

Environmental risk assessments strategies that account for the complexity of exposures are needed in order to evaluate the toxic pressure of emerging chemicals, which also provide suggestions for risk mitigation and management, if necessary. Currently, most studies on the co-occurrence and environmental impacts of chemicals of emerging concern (CECs) are conducted in countries of the Global North, leaving massive knowledge gaps in countries of the Global South. In this study, we implement a multi-scenario risk assessment strategy to improve the assessment of both the exposure and hazard components in the chemical risk assessment process. Our strategy incorporates a systematic consideration and weighting of CECs that were not detected, as well as an evaluation of the uncertainties associated with Quantitative Structure-Activity Relationships (QSARs) predictions for chronic ecotoxicity. Furthermore, we present a novel approach to identifying mixture risk drivers. To expand our knowledge beyond well-studied aquatic ecosystems, we applied this multi-scenario strategy to the River Aconcagua basin of Central Chile. The analysis revealed that the concentrations of CECs exceeded acceptable risk thresholds for selected organism groups and the most vulnerable taxonomic groups. Streams flowing through agricultural areas and sites near the river mouth exhibited the highest risks. Notably, the eight risk drivers among the 153 co-occurring chemicals accounted for 66-92 % of the observed risks in the river basin. Six of them are pesticides and pharmaceuticals, chemical classes known for their high biological activity in specific target organisms.

Water Quality Monitoring with the Multiplexed Assay MitoOxTox for Mitochondrial Toxicity, Oxidative Stress Response, and Cytotoxicity in AREc32 Cells

Mitochondria play a key role in the energy production of cells, but their function can be disturbed by environmental toxicants. We developed a cell-based mitochondrial toxicity assay for environmental chemicals and their mixtures extracted from water samples. The reporter gene cell line AREc32, which is frequently used to quantify the cytotoxicity and oxidative stress response of water samples, was multiplexed with an endpoint of mitochondrial toxicity. The disruption of the mitochondrial membrane potential (MMP) was quantified by high-content imaging and compared to measured cytotoxicity, predicted baseline toxicity, and activation of the oxidative stress response. Mitochondrial complex I inhibitors showed highly specific effects on the MMP, with minor effects on cell viability. Uncouplers showed a wide distribution of specificity on the MMP, often accompanied by specific cytotoxicity (enhanced over baseline toxicity). Mitochondrial toxicity and the oxidative stress response were not directly associated. The multiplexed assay was applied to water samples ranging from wastewater treatment plant (WWTP) influent and effluent and surface water to drinking and bottled water from various European countries. Specific effects on MMP were observed for the WWTP influent and effluent. This new MitoOxTox assay is an important complement for existing in vitro test batteries for water quality testing and has potential for applications in human biomonitoring.

Occurrence of traffic related trace elements and organic micropollutants in tunnel wash water

Substantially polluted tunnel wash water (TWW) is produced during road tunnel maintenance. Previous literature has reported the presence of trace elements and polycyclic aromatic hydrocarbons (PAHs). However, it was hypothesized that other organic pollutants are present, and more knowledge is needed to prevent environmental harm. This study reveals for the first time the presence of four short- and 17 long-chained per- and polyfluoroalkyl substances (PFASs), three benzothiazoles (BTHs), six benzotriazoles (BTRs), four bisphenols, and four benzophenones in TWW from a Norwegian road tunnel over a period of three years. Concentrations of PAHs, PFASs, BTHs, and BTRs were higher than previously reported in e.g., road runoff and municipal wastewater. Trace elements and PAHs were largely particulate matter associated, while PFASs, BTHs, BTRs, bisphenols, and benzophenones were predominantly dissolved. 26 of the determined contaminants were classified as persistent, mobile, and toxic (PMT) and are of special concern. It was recommended that regulations for TWW quality should be expanded to include PMT contaminants (such as PFPeA, PFBS, BTR, and 4-OH-BzP) and markers of pollution (like 2-M-BTH, 2-OH-BTH, and 2-S-BTH from tire wear particles). These findings highlight the need to treat TWW before discharge into the environment, addressing both, particulate matter associated and dissolved contaminants.

Effect-based monitoring of two rivers under urban and agricultural influence reveals a range of biological activities in sediment and water extracts

Chemical contaminants, such as pesticides, pharmaceuticals and industrial compounds are ubiquitous in surface water and sediment in areas subject to human activity. While targeted chemical analysis is typically used for water and sediment quality monitoring, there is growing interest in applying effect-based methods with in vitro bioassays to capture the effects of all active contaminants in a sample. The current study evaluated the biological effects in surface water and sediment from two contrasting catchments in Aotearoa New Zealand, the highly urbanised Whau River catchment in Tāmaki Makaurau (Auckland) and the urban and mixed agricultural Koreti (New River) Estuary catchment. Two complementary passive sampling devices, Chemcatcher for polar chemicals and polyethylene (PED) for non-polar chemicals, were applied to capture a wide range of contaminants in water, while composite sediment samples were collected at each sampling site. Bioassays indicative of induction of xenobiotic metabolism, receptor-mediated effects, genotoxicity, cytotoxicity and apical effects were applied to the water and sediment extracts. Most sediment extracts induced moderate to strong estrogenic and aryl hydrocarbon (AhR) activity, along with moderate toxicity to bacteria. The water extracts showed similar patterns to the sediment extracts, but with lower activity. Generally, the polar Chemcatcher extracts showed greater estrogenic activity, photosynthesis inhibition and algal growth inhibition than the non-polar PED extracts, though the PED extracts showed greater AhR activity. The observed effects in the water extracts were compared to available ecological effect-based trigger values (EBT) to evaluate the potential risk. For the polar extracts, most sites in both catchments exceeded the EBT for estrogenicity, with many sites exceeding the EBTs for AhR activity and photosynthesis inhibition. Of the wide range of endpoints considered, estrogenic activity, AhR activity and herbicidal activity appear to be the primary risk drivers in both the Whau and Koreti Estuary catchments.

Sediment characteristics mediate mixture effect of metconazole and thiacloprid on the activity behavior of the amphipod Hyalella azteca

Pesticide mixtures occur frequently in freshwaters. Here, pesticides can persist over long periods and alter aquatic communities and ecosystems by causing chronic indirect effects. Particularly effects on activity behavior of organisms can be considered as starting points of cascading effects as they provide the basis for further sublethal responses such as reproduction or feeding. Therefore, the impact of two pesticides in combination, the fungicide metconazole and the insecticide thiacloprid, was evaluated on the immobilization and activity behavior of Hyalella azteca with varying sediment conditions. The results showed a change from additive effects to synergism in the mobility tests for sediment with higher contents of total carbon but not for the activity behavior tests using a Multispecies Freshwater Biomonitoring system. However, sediments with high carbon, nitrogen and phosphorous contents led to comparable activity behavior of H. azteca to control conditions after three days of contaminant exposure which was not the case in all other treatments. The autoregressive integrated moving average (ARIMA) forecast approach used showed that this activity behavior remained constant after recovery to pre-exposure levels at least for a time period of 16 h. This study showed that mobility and activity of H. azteca are largely affected by the exposure to pesticides, which is mediated by the structure of the sediment. However, further studies are needed that test activity behavior impairments in environments where the individuals are in direct contact with the sediment that may buffer the pesticide exposure from the water column.

In vitro bioassays for monitoring drinking water quality of tap water, domestic filtration and bottled water

BACKGROUND

Location-specific patterns of regulated and non-regulated disinfection byproducts (DBPs) were detected in tap water samples of the Barcelona Metropolitan Area. However, it remains unclear if the detected DBPs together with undetected DPBs and organic micropollutants can lead to mixture effects in drinking water.

OBJECTIVE

To evaluate the neurotoxicity, oxidative stress response and cytotoxicity of 42 tap water samples, 6 treated with activated carbon filters, 5 with reverse osmosis and 9 bottled waters. To compare the measured effects of the extracts with the mixture effects predicted from the detected concentrations and the relative effect potencies of the detected DBPs using the mixture model of concentration addition.

METHODS

Mixtures of organic chemicals in water samples were enriched by solid phase extraction and tested for cytotoxicity and neurite outgrowth inhibition in the neuronal cell line SH-SY5Y and for cytotoxicity and oxidative stress response in the AREc32 assay.

RESULTS

Unenriched water did not trigger neurotoxicity or cytotoxicity. After up to 500-fold enrichment, few extracts showed cytotoxicity. Disinfected water showed low neurotoxicity at 20- to 300-fold enrichment and oxidative stress response at 8- to 140-fold enrichment. Non-regulated non-volatile DBPs, particularly (brominated) haloacetonitriles dominated the predicted mixture effects of the detected chemicals and predicted effects agreed with the measured effects. By hierarchical clustering we identified strong geographical patterns in the types of DPBs and their association with effects. Activated carbon filters did not show a consistent reduction of effects but domestic reverse osmosis filters decreased the effect to that of bottled water.

IMPACT STATEMENT

Bioassays are an important complement to chemical analysis of disinfection by-products (DBPs) in drinking water. Comparison of the measured oxidative stress response and mixture effects predicted from the detected chemicals and their relative effect potencies allowed the identification of the forcing agents for the mixture effects, which differed by location but were mainly non-regulated DBPs. This study demonstrates the relevance of non-regulated DBPs from a toxicological perspective. In vitro bioassays, in particular reporter gene assays for oxidative stress response that integrate different reactive toxicity pathways including genotoxicity, may therefore serve as sum parameters for drinking water quality assessment.

Effect-Directed Analysis Combined with Nontarget Screening to Identify Unmonitored Toxic Substances in the Environment

Effect-directed analysis (EDA) combined with nontarget screening (NTS) has established a valuable tool for the identification of unmonitored toxic substances in environmental samples. It consists of three main steps: (1) highly potent fraction identification, (2) toxicant candidate selection, and (3) major toxicant identification. Here, we discuss the methodology, current status, limitations, and future challenges of EDA combined with NTS. This method has been applied successfully to various environmental samples, such as sediments, wastewater treatment plant effluents, and biota. We present several case studies and highlight key results. EDA has undergone significant technological advancements in the past 20 years, with the establishment of its key components: target chemical analysis, bioassays, fractionation, NTS, and data processing. However, it has not been incorporated widely into environmental monitoring programs. We provide suggestions for the application of EDA combined with NTS in environmental monitoring programs and management, with the identification of further research needs.

Mixture effect assessment applying in vitro bioassays to in-tissue silicone extracts of traditional foods prepared from beluga whale blubber

We complement an earlier study on the nutrient and environmental contaminant levels in Arctic beluga whale traditional foods by mixture effect assessment using in vitro bioassays. Mixtures were extracted by in-tissue sampling of raw blubber and several traditional food preparations including Muktuk and Uqsuq using silicone (polydimethylsiloxane, PDMS) as sampler. PDMS extracts persistent and degradable neutral organic chemicals of a wide range of hydrophobicity with defined lipid-PDMS partition ratios. The solvent extracts of PDMS were dosed in various reporter gene assays based on human cell lines. Cytotoxicity was consistent across all cell lines and was a good indicator of overall chemical burden. No hormone-like effects on the estrogen receptor, the progesterone receptor and the glucocorticoid receptor were observed but a few samples activated the androgen receptor, albeit with low potency. The peroxisome-proliferator activated receptor (PPARγ) was the most sensitive endpoint followed by activation of oxidative stress response and activation of the arylhydrocarbon (AhR) receptor. The detected pollutants only explained a small fraction of the experimental mixture effects, indicating additional bioactive pollutants. The effect levels of the extracted mixtures were higher than those observed in blubber extracts of dugongs living off the shore of Australia. Roasting over an open fire or food preparation near a smokehouse led to increased PAH levels that were reflected in increased oxidative stress response and activation of the AhR. So far in vitro assays have only been used to quantify persistent dioxin-like chemicals in food and feed but this pilot study demonstrates a much broader potential for food safety evaluations complementing chemical analytical monitoring.

A critical review on quantitative evaluation of aqueous toxicity in water quality assessment

Conventional chemical techniques have inherent limitations in detecting unknown chemical substances in water. As a result, effect-based methods have emerged as a viable alternative to overcome these limitations. These methods provide more accurate and intuitive evaluations of the toxic effects of water. While numerous studies have been conducted, only a few have been applied to national water quality monitoring. Therefore, it is crucial to develop toxicity evaluation methods and establish thresholds based on quantifying toxicity. This article provides an overview of the development and application of bioanalytical tools, including in vitro and in vivo bioassays. The available methods for quantifying toxicity are then summarized. These methods include aquatic life criteria for assessing the toxicity of a single compound, comprehensive wastewater toxicity testing for all contaminants in a water sample (toxicity units, whole effluent toxicity, the potential ecotoxic effects probe, the potential toxicology method, and the lowest ineffective dilution), methods based on mechanisms and relative toxicity ratios for substances with the same mode of action (the toxicity equivalency factors, toxic equivalents, bioanalytical equivalents), and effect-based trigger values for micropollutants. The article also highlights the advantages and disadvantages of each method. Finally, it proposes potential areas for applying toxicity quantification methods and offers insights into future research directions. This review emphasizes the significance of enhancing the evaluation methods for assessing aqueous toxicity in water quality assessment.

Identification of Mid-Polar and Polar AhR Agonists in Cetaceans from Korean Coastal Waters: Application of Effect-Directed Analysis with Full-Scan Screening

Major aryl hydrocarbon receptor (AhR) agonists were identified in extracts of blubber, liver, and muscle from six long-beaked common dolphins (Delphinus capensis) and one fin whale (Balaenoptera physalus) collected from Korean coastal waters using effect-directed analysis. Results of the H4IIE-luc bioassay indicated that the polar fractions of blubber and liver extracts from the fin whale exhibited relatively high AhR-mediated potencies. Based on full-scan screening with high-resolution mass spectrometry, 37 AhR agonist candidates, spanning four use categories: pharmaceuticals, pesticides, cosmetics, and natural products, were selected. Among these, five polar AhR agonists were newly identified through toxicological confirmation. Concentrations of polar AhR agonists in cetaceans were tissue-specific, with extracts of blubber and liver containing greater concentrations than muscle extracts. Polar AhR agonists with great log KOA values (>5) were found to biomagnify in the marine food chain potentially. Polar AhR agonists contributed 8.9% of the observed AhR-mediated potencies in blubber and 49% in liver. Rutaecarpine and alantolactone contributed significantly to the total AhR-mediated potencies of blubber, whereas hydrocortisone was a major AhR contributor in the liver of the fin whale. This study is the first to identify the tissue-specific accumulation of polar AhR agonists in blubber and liver extracts of cetaceans.

Chemical Mixtures and Multiple Stressors: Same but Different?

Ecosystems are strongly influenced by multiple anthropogenic stressors, including a wide range of chemicals and their mixtures. Studies on the effects of multiple stressors have largely focussed on nonchemical stressors, whereas studies on chemical mixtures have largely ignored other stressors. However, both research areas face similar challenges and require similar tools and methods to predict the joint effects of chemicals or nonchemical stressors, and frameworks to integrate multiple chemical and nonchemical stressors are missing. We provide an overview of the research paradigms, tools, and methods commonly used in multiple stressor and chemical mixture research and discuss potential domains of cross-fertilization and joint challenges. First, we compare the general paradigms of ecotoxicology and (applied) ecology to explain the historical divide. Subsequently, we compare methods and approaches for the identification of interactions, stressor characterization, and designing experiments. We suggest that both multiple stressor and chemical mixture research are too focused on interactions and would benefit from integration regarding null model selection. Stressor characterization is typically more costly for chemical mixtures. While for chemical mixtures comprehensive classification systems at suborganismal level have been developed, recent classification systems for multiple stressors account for environmental context. Both research areas suffer from rather simplified experimental designs that focus on only a limited number of stressors, chemicals, and treatments. We discuss concepts that can guide more realistic designs capturing spatiotemporal stressor dynamics. We suggest that process-based and data-driven models are particularly promising to tackle the challenge of prediction of effects of chemical mixtures and nonchemical stressors on (meta-)communities and (meta-)food webs. We propose a framework to integrate the assessment of effects for multiple stressors and chemical mixtures. Environ Toxicol Chem 2023;42:1915-1936. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Standard Versus Natural: Assessing the Impact of Environmental Variables on Organic Matter Decomposition in Streams Using Three Substrates

The decomposition of allochthonous organic matter, such as leaves, is a crucial ecosystem process in low-order streams. Microbial communities, including fungi and bacteria, colonize allochthonous organic material, break up large molecules, and increase the nutritional value for macroinvertebrates. Environmental variables are known to affect microbial as well as macroinvertebrate communities and alter their ability to decompose organic matter. Studying the relationship between environmental variables and decomposition has mainly been realized using leaves, with the drawbacks of differing substrate composition and consequently between-study variability. To overcome these drawbacks, artificial substrates have been developed, serving as standardizable surrogates. In the present study, we compared microbial and total decomposition of leaves with the standardized substrates of decotabs and, only for microbial decomposition, of cotton strips, across 70 stream sites in a Germany-wide study. Furthermore, we identified the most influential environmental variables for the decomposition of each substrate from a range of 26 variables, including pesticide toxicity, concentrations of nutrients, and trace elements, using stability selection. The microbial as well as total decomposition of the standardized substrates (i.e., cotton strips and decotabs) were weak or not associated with that of the natural substrate (i.e., leaves, r² < 0.01 to r² = 0.04). The decomposition of the two standardized substrates, however, showed a moderate association (r² = 0.21), which is probably driven by their similar composition, with both being made of cellulose. Different environmental variables were identified as the most influential for each of the substrates and the directions of these relationships contrasted between the substrates. Our results imply that these standardized substrates are unsuitable surrogates when investigating the decomposition of allochthonous organic matter in streams. Environ Toxicol Chem 2023;42:2007-2018. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

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.

Impact of a megacity on the water quality of a tropical estuary assessed by a combination of chemical analysis and in-vitro bioassays

Tropical estuaries are threatened by rapid urbanization, which leads to the spread of thousands of micropollutants and poses an environmental risk to such sensitive aqueous ecosystems. In the present study, a combination of chemical and bioanalytical water characterization was applied to investigate the impact of Ho Chi Minh megacity (HCMC, 9.2 million inhabitants in 2021) on the Saigon River and its estuary and provide a comprehensive water quality assessment. Water samples were collected along a 140-km stretch integrating the river-estuary continuum from upstream HCMC down to the estuary mouth in the East Sea. Additional water samples were collected at the mouth of the four main canals of the city center. Chemical analysis was performed targeting up to 217 micropollutants (pharmaceuticals, plasticizers, PFASs, flame retardants, hormones, pesticides). Bioanalysis was performed using six in-vitro bioassays for hormone receptor-mediated effects, xenobiotic metabolism pathways and oxidative stress response, respectively, all accompanied by cytotoxicity measurement. A total of 120 micropollutants were detected and displayed high variability along the river continuum with total concentration ranging from 0.25 to 78 μg L^-1. Among them, 59 micropollutants were ubiquitous (detection frequency ≥ 80 %). An attenuation was observed in concentration and effect profiles towards the estuary. The urban canals were identified as major sources of micropollutants and bioactivity to the river, and one canal (Bến Nghé) exceeded the effect-based trigger values derived for estrogenicity and xenobiotic metabolism. Iceberg modelling apportioned the contribution of the quantified and the unknown chemicals to the measured effects. Diuron, metolachlor, chlorpyrifos, daidzein, genistein, climbazole, mebendazole and telmisartan were identified as main risk drivers of the oxidative stress response and xenobiotic metabolism pathway activation. Our study reinforced the need for improved wastewater management and deeper evaluations of the occurrence and fate of micropollutants in urbanized tropical estuarine environments.

Characterization of micropollutants in urban stormwater using high-resolution monitoring and machine learning

Urban rainfall events can lead to the runoff of pollutants, including industrial, pesticide, and pharmaceutical chemicals. Transporting micropollutants (MPs) into water systems can harm both human health and aquatic species. Therefore, it is necessary to investigate the dynamics of MPs during rainfall events. However, few studies have examined MPs during rainfall events due to the high analytical expenses and extensive spatiotemporal variability. Few studies have investigated the occurrence patterns of MPs and factors that influence their transport, such as rainfall duration, antecedent dry periods, and variations in streamflow. Moreover, while there have been many analyses of nutrients, suspended solids, and heavy metals during the first flush effect (FFE), studies on the transport of MPs during FFE are insufficient. This study aimed to identify the dynamics of MPs and FFE in an urban catchment, using high-resolution monitoring and machine learning methods. Hierarchical clustering analysis and partial least squares regression (PLSR) were implemented to estimate the similarity between each MP and identify the factors influencing their transport during rainfall events. Eleven dominant MPs comprised 75% of the total MP concentration and had a 100% detection frequency. During rainfall events, pesticides and pharmaceutical MPs showed a higher FFE than industrial MPs. Moreover, the initial 30% of the runoff volume contained 78.0% of pesticide and 50.1% of pharmaceutical substances for events W1 (July 5 to July 6, 2021) and W6 (August 31 to September 1, 2021), respectively. The PLSR model suggested that stormflow (m³/s) and the duration of antecedent dry hours (h) significantly influenced MP dynamics, yielding the variable importance on projection scores greater than 1.0. Hence, our findings indicate that MPs in urban waters should be managed by considering FFE.

Temporal scales of pesticide exposure and risks in German small streams

Following agricultural application, pesticides can enter streams through runoff during rain events. However, little information is available on the temporal dynamics of pesticide toxicity during the main application period. We investigated pesticide application and large scale in-stream monitoring data from 101 agricultural catchments obtained from a Germany-wide monitoring from April to July in 2018 and 2019. We analysed temporal patterns of pesticide application, in-stream toxicity and exceedances of regulatory acceptable concentrations (RAC) for over 70 pesticides. On a monthly scale from April to July, toxicity to invertebrates and algae/aquatic plants (algae) obtained with event-driven samples (EDS) was highest in May/June. The peak of toxicity towards invertebrates and algae coincided with the peaks of insecticide and herbicide application. Future monitoring, i.e. related to the Water Framework Directive, could be limited to time periods of highest pesticide applications on a seasonal scale. On a daily scale, toxicity to invertebrates from EDS exceeded those of grab samples collected within one day after rainfall by a factor of 3.7. Within two to three days, toxicity in grab samples declined compared to EDS by a factor of ten for invertebrates, and a factor of 1.6 for algae. Thus, toxicity to invertebrates declined rapidly within 1 day after a rainfall event, whereas toxicity to algae remained elevated for up to 4 days. For six pesticides, RAC exceedances could only be detected in EDS. The exceedances of RACs coincided with the peaks in pesticide application. Based on EDS, we estimated that pesticide exposure would need a 37-fold reduction of all analysed pesticides, to meet the German environmental target to keep RAC exceedances below 1 % of EDS. Overall, our study shows a high temporal variability of exposure on a monthly but also daily scale to individual pesticides that can be linked to their period of application and related rain events.

Modernizing persistence-bioaccumulation-toxicity (PBT) assessment with high throughput animal-free methods

The assessment of persistence (P), bioaccumulation (B), and toxicity (T) of a chemical is a crucial first step at ensuring chemical safety and is a cornerstone of the European Union's chemicals regulation REACH (Registration, Evaluation, Authorization, and Restriction of Chemicals). Existing methods for PBT assessment are overly complex and cumbersome, have produced incorrect conclusions, and rely heavily on animal-intensive testing. We explore how new-approach methodologies (NAMs) can overcome the limitations of current PBT assessment. We propose two innovative hazard indicators, termed cumulative toxicity equivalents (CTE) and persistent toxicity equivalents (PTE). Together they are intended to replace existing PBT indicators and can also accommodate the emerging concept of PMT (where M stands for mobility). The proposed "toxicity equivalents" can be measured with high throughput in vitro bioassays. CTE refers to the toxic effects measured directly in any given sample, including single chemicals, substitution products, or mixtures. PTE is the equivalent measure of cumulative toxicity equivalents measured after simulated environmental degradation of the sample. With an appropriate panel of animal-free or alternative in vitro bioassays, CTE and PTE comprise key environmental and human health hazard indicators. CTE and PTE do not require analytical identification of transformation products and mixture components but instead prompt two key questions: is the chemical or mixture toxic, and is this toxicity persistent or can it be attenuated by environmental degradation? Taken together, the proposed hazard indicators CTE and PTE have the potential to integrate P, B/M and T assessment into one high-throughput experimental workflow that sidesteps the need for analytical measurements and will support the Chemicals Strategy for Sustainability of the European Union.

Contamination Pattern and Risk Assessment of Polar Compounds in Snow Melt: An Integrative Proxy of Road Runoffs

To assess the contamination and potential risk of snow melt with polar compounds, road and background snow was sampled during a melting event at 23 sites at the city of Leipzig and screened for 489 chemicals using liquid chromatography high-resolution mass spectrometry with target screening. Additionally, six 24 h composite samples were taken from the influent and effluent of the Leipzig wastewater treatment plant (WWTP) during the snow melt event. 207 compounds were at least detected once (concentrations between 0.80 ng/L and 75 μg/L). Consistent patterns of traffic-related compounds dominated the chemical profile (58 compounds in concentrations from 1.3 ng/L to 75 μg/L) and among them were 2-benzothiazole sulfonic acid and 1-cyclohexyl-3-phenylurea from tire wear and denatonium used as a bittern in vehicle fluids. Besides, the analysis unveiled the presence of the rubber additive 6-PPD and its transformation product N-(1.3-dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone (6-PPDQ) at concentrations known to cause acute toxicity in sensitive fish species. The analysis also detected 149 other compounds such as food additives, pharmaceuticals, and pesticides. Several biocides were identified as major risk contributors, with a more site-specific occurrence, to acute toxic risks to algae (five samples) and invertebrates (six samples). Ametryn, flumioxazin, and 1,2-cyclohexane dicarboxylic acid diisononyl ester are the main compounds contributing to toxic risk for algae, while etofenprox and bendiocarb are found as the main contributors for crustacean risk. Correlations between concentrations in the WWTP influent and flow rate allowed us to discriminate compounds with snow melt and urban runoff as major sources from other compounds with other dominant sources. Removal rates in the WWTP showed that some traffic-related compounds were largely eliminated (removal rate higher than 80%) during wastewater treatment and among them was 6-PPDQ, while others persisted in the WWTP.

Effect-Based Trigger Values Are Essential for the Uptake of Effect-Based Methods in Water Safety Planning

Effect-based methods (EBMs) using in vitro bioassays and well plate-based in vivo assays are recommended for water quality monitoring because they can capture the mixture effects of the many chemicals present in water. Many in vitro bioassays are highly sensitive, so an effect in a bioassay does not necessarily indicate poor chemical water quality. Consequently, effect-based trigger values (EBTs) have been introduced to differentiate between acceptable and unacceptable chemical water quality and are required for the wider acceptance of EBMs by the water sector and regulatory bodies. These EBTs have been derived for both drinking water and surface water to protect human and ecological health, respectively, and are available for assays indicative of specific receptor-mediated effects, as well as assays indicative of adaptive stress responses, apical effects, and receptor-mediated effects triggered by many chemicals. An overview of currently available EBTs is provided, and a simple approach is proposed to predict interim EBTs for assays currently without an EBT based on the effect concentration of the assay reference compound. There was good agreement between EBTs predicted using this simplistic approach and EBTs from the literature derived using more robust methods. Finally, an interpretation framework that outlines the steps to take if the effect of a sample exceeds the EBT was developed to help facilitate the uptake of EBMs in routine water quality monitoring and water safety planning for drinking water production. Environ Toxicol Chem 2023;42:714-726. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

pH-responsive λ-cyhalothrin nanopesticides for effective pest control and reduced toxicity to Harmonia axyridis

In this study, pH-responsive LC@O-CMCS/PU nanoparticles were prepared by encapsulating λ-cyhalothrin (LC) with O-carboxymethyl chitosan (O-CMCS) to form LC/O-CMCS and then covering it with polyurethane (PU). Characterization and performance test results demonstrate that LC@O-CMCS/PU had good alkaline release properties and pesticide loading performance. Compared to commercial formulations containing large amounts of emulsifiers (e.g., emulsifiable concentrate, EC), LC@O-CMCS/PU showed better leaf-surface adhesion. On the dried pesticide-applied surfaces, the acute contact toxicity of LC@O-CMCS/PU to Harmonia axyridis (H. axyridis) was nearly 20 times lower than that of LC EC. Due to the slow-releasing property of LC@O-CMCS/PU, only 16.38 % of LC was released at 48 h in dew and effectively reduced the toxicity of dew. On the pesticide-applied leaves with dew, exposure to the LC (EC) caused 86.66 % mortality of H. axyridis larvae significantly higher than the LC@O-CMCS/PU, which was only 16.66 % lethality. Additionally, quantitative analysis demonstrated 11.33 mg/kg of λ-cyhalothrin in the dew on LC@O-CMCS/PU lower than LC (EC) with 4.54 mg/kg. In summary, LC@O-CMCS/PU effectively improves the safety of λ-cyhalothrin to H. axyridis and has great potential to be used in pest control combining natural enemies and chemical pesticides.

A geospatial modeling approach to quantifying the risk of exposure to environmental chemical mixtures via a common molecular target

In the real world, individuals are exposed to chemicals from sources that vary over space and time. However, traditional risk assessments based on in vivo animal studies typically use a chemical-by-chemical approach and apical disease endpoints. New approach methodologies (NAMs) in toxicology, such as in vitro high-throughput (HTS) assays generated in Tox21 and ToxCast, can more readily provide mechanistic chemical hazard information for chemicals with no existing data than in vivo methods. In this paper, we establish a workflow to assess the joint action of 41 modeled ambient chemical exposures in the air from the USA-wide National Air Toxics Assessment by integrating human exposures with hazard data from curated HTS (cHTS) assays to identify counties where exposure to the local chemical mixture may perturb a common biological target. We exemplify this proof-of-concept using CYP1A1 mRNA up-regulation. We first estimate internal exposure and then convert the inhaled concentration to a steady state plasma concentration using physiologically based toxicokinetic modeling parameterized with county-specific information on ages and body weights. We then use the estimated blood plasma concentration and the concentration-response curve from the in vitro cHTS assay to determine the chemical-specific effects of the mixture components. Three mixture modeling methods were used to estimate the joint effect from exposure to the chemical mixture on the activity levels, which were geospatially mapped. Finally, a Monte Carlo uncertainty analysis was performed to quantify the influence of each parameter on the combined effects. This workflow demonstrates how NAMs can be used to predict early-stage biological perturbations that can lead to adverse health outcomes that result from exposure to chemical mixtures. As a result, this work will advance mixture risk assessment and other early events in the effects of chemicals.

Effect of Pesticides on Peroxisome Proliferator-Activated Receptors (PPARs) and Their Association with Obesity and Diabetes

Obesity and diabetes mellitus are considered the most important diseases of the XXI century. Recently, many epidemiological studies have linked exposure to pesticides to the development of obesity and type 2 diabetes mellitus. The role of pesticides and their possible influence on the development of these diseases was investigated by examining the relationship between these compounds and one of the major nuclear receptor families controlling lipid and carbohydrate metabolism: the peroxisome proliferator-activated receptors (PPARs), PPARα, PPARβ/δ, and PPARγ; this was possible through in silico, in vitro, and in vivo assays. The present review aims to show the effect of pesticides on PPARs and their contribution to the changes in energy metabolism that enable the development of obesity and type 2 diabetes mellitus.

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.

Modeling the Dynamics of Mixture Toxicity and Effects of Organic Micropollutants in a Small River under Unsteady Flow Conditions

The presence of anthropogenic organic micropollutants in rivers poses a long-term threat to surface water quality. To describe and quantify the in-stream fate of single micropollutants, the advection-dispersion-reaction (ADR) equation has been used previously. Understanding the dynamics of the mixture effects and cytotoxicity that are cumulatively caused by micropollutant mixtures along their flow path in rivers requires a new concept. Thus, we extended the ADR equation from single micropollutants to defined mixtures and then to the measured mixture effects of micropollutants extracted from the same river water samples. Effects (single and mixture) are expressed as effect units and toxic units, the inverse of effect concentrations and inhibitory concentrations, respectively, quantified using a panel of in vitro bioassays. We performed a Lagrangian sampling campaign under unsteady flow, collecting river water that was impacted by a wastewater treatment plant (WWTP) effluent. To reduce the computational time, the solution of the ADR equation was expressed by a convolution-based reactive transport approach, which was used to simulate the dynamics of the effects. The dissipation dynamics of the individual micropollutants were reproduced by the deterministic model following first-order kinetics. The dynamics of experimental mixture effects without known compositions were captured by the model ensemble obtained through Bayesian calibration. The highly fluctuating WWTP effluent discharge dominated the temporal patterns of the effect fluxes in the river. Minor inputs likely from surface runoff and pesticide diffusion might contribute to the general effect and cytotoxicity pattern but could not be confirmed by the model-based analysis of the available effect and chemical data.

Mixture Risk Assessment of Complex Real-Life Mixtures-The PANORAMIX Project

Humans are involuntarily exposed to hundreds of chemicals that either contaminate our environment and food or are added intentionally to our daily products. These complex mixtures of chemicals may pose a risk to human health. One of the goals of the European Union's Green Deal and zero-pollution ambition for a toxic-free environment is to tackle the existent gaps in chemical mixture risk assessment by providing scientific grounds that support the implementation of adequate regulatory measures within the EU. We suggest dealing with this challenge by: (1) characterising 'real-life' chemical mixtures and determining to what extent they are transferred from the environment to humans via food and water, and from the mother to the foetus; (2) establishing a high-throughput whole-mixture-based in vitro strategy for screening of real-life complex mixtures of organic chemicals extracted from humans using integrated chemical profiling (suspect screening) together with effect-directed analysis; (3) evaluating which human blood levels of chemical mixtures might be of concern for children's development; and (4) developing a web-based, ready-to-use interface that integrates hazard and exposure data to enable component-based mixture risk estimation. These concepts form the basis of the Green Deal project PANORAMIX, whose ultimate goal is to progress mixture risk assessment of chemicals.

Cumulative Risk Meets Inter-Individual Variability: Probabilistic Concentration Addition of Complex Mixture Exposures in a Population-Based Human In Vitro Model

Although humans are continuously exposed to complex chemical mixtures in the environment, it has been extremely challenging to investigate the resulting cumulative risks and impacts. Recent studies proposed the use of “new approach methods,” in particular in vitro assays, for hazard and dose−response evaluation of mixtures. We previously found, using five human cell-based assays, that concentration addition (CA), the usual default approach to calculate cumulative risk, is mostly accurate to within an order of magnitude. Here, we extend these findings to further investigate how cell-based data can be used to quantify inter-individual variability in CA. Utilizing data from testing 42 Superfund priority chemicals separately and in 8 defined mixtures in a human cell-based population-wide in vitro model, we applied CA to predict effective concentrations for cytotoxicity for each individual, for “typical” (median) and “sensitive” (first percentile) members of the population, and for the median-to-sensitive individual ratio (defined as the toxicodynamic variability factor, TDVF). We quantified the accuracy of CA with the Loewe Additivity Index (LAI). We found that LAI varies more between different mixtures than between different individuals, and that predictions of the population median are generally more accurate than predictions for the “sensitive” individual or the TDVF. Moreover, LAI values were generally <1, indicating that the mixtures were more potent than predicted by CA. Together with our previous studies, we posit that new approach methods data from human cell-based in vitro assays, including multiple phenotypes in diverse cell types and studies in a population-wide model, can fill critical data gaps in cumulative risk assessment, but more sophisticated models of in vitro mixture additivity and bioavailability may be needed. In the meantime, because simple CA models may underestimate potency by an order of magnitude or more, either whole-mixture testing in vitro or, alternatively, more stringent benchmarks of cumulative risk indices (e.g., lower hazard index) may be needed to ensure public health protection.

Non-target screening of micropollutants and transformation products for assessing AOP-BAC treatment in groundwater

Standard monitoring programs give limited insight into groundwater status, especially transformation products (TPs) formed by natural processes or advanced oxidation processes (AOP), are normally underrepresented. In this study, using suspect and non-target screening, we performed a comprehensive analysis of groundwater before and after AOP by UV/H₂O₂ and consecutively installed biological activated carbon filters (BAC). By non-target screening, up to 413 compounds were detected in the groundwater, with an average 70% removal by AOP. However, a similar number of compounds were formed during the process, shown in groundwater from three waterworks. The most polar compounds were typically the most stable during the AOP. A subsequent BAC filter showed removal of 95% of the TPs, but only 46% removal of the AOP remaining precursors. The BAC removal for polar compounds was highly dependent on the acidic and basic functional groups of the molecules. 49 compounds of a wide polarity range could be identified by supercritical fluid chromatography (SFC) and liquid chromatography (LC) with high resolution mass spectrometry (HRMS); of these, 29 compounds were already present in the groundwater. To the best of our knowledge, five compounds have never been reported before in groundwater (4-chlorobenzenesulfonic acid, dibutylamine, N-phenlybenzenesulfonamide, 2-(methylthio)benzothiazole and benzothiazole-2-sulfonate). A further five rarely reported compounds are reported for the first time in Danish groundwater (2,4,6-trichlorophenol, 2,5-dichlorobenzenesulfonic acid, trifluormethansulfonic acid, pyrimidinol and benzymethylamine). Twenty of the identified compounds were formed by AOP, of which 10 have never been reported before in groundwater. All detected compounds could be related to agricultural and industrial products as well as artificial sweeteners. Whereas dechlorination was a common AOP degradation pathway for chlorophenols, the (ultra-) short chain PFAs showed no removal in our study. We prioritized 11 compounds as of concern, however, the toxicity for many compounds remains unknown, especially for the TPs.

Monitoring Mixture Effects of Neurotoxicants in Surface Water and Wastewater Treatment Plant Effluents with Neurite Outgrowth Inhibition in SH-SY5Y Cells

Cell-based assays covering environmentally relevant modes of action are widely used for water quality monitoring. However, no high-throughput assays are available for testing developmental neurotoxicity of water samples. We implemented an assay that quantifies neurite outgrowth, which is one of the neurodevelopmental key events, and cell viability in human neuroblastoma SH-SY5Y cells using imaging techniques. We used this assay for testing of extracts of surface water collected in agricultural areas during rain events and effluents from wastewater treatment plants (WWTPs), where more than 200 chemicals had been quantified. Forty-one chemicals were tested individually that were suspected to contribute to the mixture effects among the detected chemicals in environmental samples. Sample sensitivity distributions indicated higher neurotoxicity for surface water samples than for effluents, and the endpoint of neurite outgrowth inhibition was six times more sensitive than cytotoxicity in the surface water samples and only three times more sensitive in the effluent samples. Eight environmental pollutants showed high specificity, and those ranged from pharmaceuticals (mebendazole and verapamil) to pesticides (methiocarb and clomazone), biocides (1,2-benzisothiazolin-3-one), and industrial chemicals (N-methyl-2-pyrrolidone, 7-diethylamino-4-methylcoumarin, and 2-(4-morpholinyl)benzothiazole). Although neurotoxic effects were newly detected for some of our test chemicals, less than 1% of the measured effects were explained by the detected and toxicologically characterized chemicals. The neurotoxicity assay was benchmarked against other bioassays: activations of the aryl hydrocarbon receptor and the peroxisome proliferator-activated receptor were similar in sensitivity, highly sensitive and did not differ much between the two water types, with surface water having slightly higher effects than the WWTP effluent. Oxidative stress response mirrored neurotoxicity quite well but was caused by different chemicals in the two water types. Overall, the new cell-based neurotoxicity assay is a valuable complement to the existing battery of effect-based monitoring tools.

Impact of various aeration strategies on the removal of micropollutants and biological effects in aerated horizontal flow treatment wetlands

Two aerated horizontal subsurface flow treatment wetlands were studied over two years for the removal efficacy with respect of conventional wastewater parameters, micropollutants and effect-based methods. One wetland served as control and was aerated 24 h d^-1 across 100% of the fractional length of the system. The second aerated horizontal flow treatment wetland was investigated under several aeration modes: first year with a zone of 85% aeration, followed by five months with a zone of 50% aeration and six months with a zone of 35% aeration. With 85% aeration, no significant difference in the removal efficacy as compared to the fully aerated control could be observed, except for E. coli, which were removed four times better in the control. No significant difference in removal efficacy for Total Organic Carbon, 5-day Carbonaceous Biochemical Oxygen Demand, caffeine, and naproxen were observed. A 50% non-aerated zone reduced the overall removal efficacy of biological effects. The highest removal efficacy for the moderately biodegradable micropollutants benzotriazole and diclofenac was observed in the system with 50% aeration. This could be due to the sharp increase of dissolved oxygen (DO) and oxidation reduction potential at the passage from the non-aerated to the aerated zone (at 75% of the fractional length). The internal concentration profiles of caffeine, ibuprofen and naproxen varied from 12.5%, 25%, 50% to 75% fractional length due to redox shift, DO variations and other conditions. A reduction of the aerated zone to 35% of the fractional length results in reduced treatment efficacy for benzotriazole, diclofenac, acesulfame and biological effects but 50% aeration yielded as much degradation as the fully aerated control. These results indicate that less aeration could provide similar effluent water quality, depending on the pollutants of interest. E. coli and biological effects were removed best in the fully aerated system.

Chemical and biological assessments of environmental mixtures: A review of current trends, advances, and future perspectives

Considering the chemical complexity and toxicity data gaps of environmental mixtures, most studies evaluate the chemical risk individually. However, humans are usually exposed to a cocktail of chemicals in real life. Mixture health assessment remains to be a research area having significant knowledge gaps. Characterization of chemical composition and bioactivity/toxicity are the two critical aspects of mixture health assessments. This review seeks to introduce the recent progress and tools for the chemical and biological characterization of environmental mixtures. The state-of-the-art techniques include the sampling, extraction, rapid detection methods, and the in vitro, in vivo, and in silico approaches to generate the toxicity data of an environmental mixture. Application of these novel methods, or new approach methodologies (NAMs), has increased the throughput of generating chemical and toxicity data for mixtures and thus refined the mixture health assessment. Combined with computational methods, the chemical and biological information would shed light on identifying the bioactive/toxic components in an environmental mixture.

pH-Dependent Partitioning of Ionizable Organic Chemicals between the Silicone Polymer Polydimethylsiloxane (PDMS) and Water

The silicone polymer polydimethysiloxane (PDMS) is a popular passive sampler for in situ and ex situ sampling of hydrophobic organic chemicals. Despite its limited sorptive capacity for polar and ionizable organic chemicals (IOC), IOCs have been found in PDMS when extracting sediment and suspended particulate matter. The pH-dependent partitioning of 190 organics and IOCs covering a range of octanol-water partition constants log K _ow from -0.3 to 7.7 was evaluated with a 10-day shaking method using mixtures composed of all chemicals at varying ratios of mass of PDMS to volume of water. This method reproduced the PDMS-water partition constant K _PDMS/w of neutral chemicals from the literature and extended the dataset by 93 neutral chemicals. The existing quantitative structure-activity relationship between the log K _ow and K _PDMS/w could be extended with the measured K _PDMS/w linearly to a log K _ow of -0.3. Fully charged organics were not taken up into PDMS. Thirty-eight monoprotic organic acids and 42 bases showed negligible uptake of the charged species, and the pH dependence of the apparent D _PDMS/w(pH) could be explained by the fraction of neutral species multiplied by the K _PDMS/w of the neutral species of these IOCs. Seventeen multiprotic chemicals with up to three acidity constants pK _a also showed a pH dependence of D _PDMS/w(pH) with the tendency that the neutral and zwitterionic forms showed the highest D _PDMS/w(pH). D _PDMS/w(pH) of charged species of more hydrophobic multiprotic chemicals such as tetrabromobisphenol A and telmisartan was smaller but not negligible. Since these chemicals show high bioactivity, their contribution to mixture effects has to be considered when testing passive sampling extracts with in vitro bioassays. This work has further implications for understanding the role of microplastic as a vector for organic micropollutants.

Extensive rain events have a more substantial impact than advanced effluent treatment on the endocrine-disrupting activity in an effluent-dominated small river

Wastewater treatment plants (WWTPs) remain an important primary source of emission for endocrine-disrupting compounds in the environment. As an advanced wastewater treatment process, ozonation is known to reduce endocrine-disrupting activity. However, it remains unclear to which extend improved wastewater treatment may reduce the endocrine-disrupting activity in the receiving water body. The present study investigated possible factors for the endocrine-disrupting activity in a small receiving water body, the Wurm River (North-Rhine Westphalia, Germany), up- and downstream of a local WWTP. The cell-based reporter gene CALUX® assay was applied to identify the endocrine-disrupting activity in the water, sediment, and suspended particulate matter. The water phase and the effluent sampling were primarily driven by applying the full-scale effluent ozonation (sampling campaigns in June 2017 and March 2019). In contrast, the sediment sampling aimed to compare the particle-bound endocrine-disrupting activity during dry (June 2017) and rainy summer (June 2018) seasons. The water phase showed low to moderate estrogenic/antiandrogenic activity. Advanced effluent treatment by ozonation led to a complete reduction of the endocrine-disrupting activity according to the limit of detection of the CALUX® assays. The suspended particulate matter originated from the water phase of the second sampling campaign revealed antiandrogenic activity only. Sediments at the sampling sites along the local WWTP revealed higher estrogenic and antiandrogenic activity after extensive rain events and were not affected by the ozonated effluent. Fluctuation patterns of the endocrine-disrupting activity in sediments were in line with fluctuated concentrations of polycyclic aromatic hydrocarbons. Rainwater overflow basin release was suggested as a vector for particle-bound and dissolved endocrine-disrupting activity in the receiving water body. The present study underlined the necessity for monitoring both water and sediment phases to achieve reliable profiling of the endocrine-disrupting activity. The receptor-mediated CALUX® assays were proven to be suitable for investigating the endocrine-disrupting activity distribution in different river compartments and WWTP effluents.

Effects of leachates from UV-weathered microplastic on the microalgae Scenedesmus vacuolatus

Plastics undergo successive fragmentation and chemical leaching steps in the environment due to weathering processes such as photo-oxidation. Here, we report the effects of leachates from UV-irradiated microplastics towards the chlorophyte Scenedesmus vacuolatus. The microplastics tested were derived from an additive-containing electronic waste (EW) and a computer keyboard (KB) as well as commercial virgin polymers with low additive content, including polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), and polystyrene (PS). Whereas leachates from additive-containing EW and KB induced severe effects, the leachates from virgin PET, PP, and PS did not show substantial adverse effects in our autotrophic test system. Leachates from PE reduced algae biomass, cell growth, and photosynthetic activity. Experimental data were consistent with predicted effect concentrations based on the ionization-corrected liposome/water distribution ratios (D_lip/w) of polymer degradation products of PE (mono- and dicarboxylic acids), indicating that leachates from weathering PE were mainly baseline toxic. This study provides insight into algae toxicity elicited by leachates from UV-weathered microplastics of different origin, complementing the current particle- vs. chemical-focused research towards the toxicity of plastics and their leachates.

Potential Human Health Hazard of Post-Hurricane Harvey Sediments in Galveston Bay and Houston Ship Channel: A Case Study of Using In Vitro Bioactivity Data to Inform Risk Management Decisions

Natural and anthropogenic disasters may be associated with redistribution of chemical contaminants in the environment; however, current methods for assessing hazards and risks of complex mixtures are not suitable for disaster response. This study investigated the suitability of in vitro toxicity testing methods as a rapid means of identifying areas of potential human health concern. We used sediment samples (n = 46) from Galveston Bay and the Houston Ship Channel (GB/HSC) areas after hurricane Harvey, a disaster event that led to broad redistribution of chemically-contaminated sediments, including deposition of the sediment on shore due to flooding. Samples were extracted with cyclohexane and dimethyl sulfoxide and screened in a compendium of human primary or induced pluripotent stem cell (iPSC)-derived cell lines from different tissues (hepatocytes, neuronal, cardiomyocytes, and endothelial) to test for concentration-dependent effects on various functional and cytotoxicity phenotypes (n = 34). Bioactivity data were used to map areas of potential concern and the results compared to the data on concentrations of polycyclic aromatic hydrocarbons (PAHs) in the same samples. We found that setting remediation goals based on reducing bioactivity is protective of both "known" risks associated with PAHs and "unknown" risks associated with bioactivity, but the converse was not true for remediation based on PAH risks alone. Overall, we found that in vitro bioactivity can be used as a comprehensive indicator of potential hazards and is an example of a new approach method (NAM) to inform risk management decisions on site cleanup.

Chemical mixtures in human post-mortem tissues assessed by a combination of chemical analysis and in vitro bioassays after extraction with silicone

Passive equilibrium sampling of chemical mixtures from different human post-mortem tissues (liver, brain (cerebrum and cerebellum), adipose tissue) and blood was combined with instrumental analysis using direct sample introduction (DSI) GC-MS/MS and bioanalytical profiling using in vitro bioassays targeting the activation of the aryl hydrocarbon receptor (AhR-CALUX), the adaptive stress response (AREc32) and cytotoxicity. The tissues stemmed from pathology samples collected in two German cities and covered males and females aged 21 to 100 with a mean age of 67 years. Neutral organic chemicals were extracted using polydimethylsiloxane (PDMS) at mass ratios of tissue to PDMS of approximately 6 for blood, 3 for adipose tissue and 10 for liver and brain. Amounts of chemicals in PDMS were converted to lipid-associated concentrations using previously measured partition constants that were chemical-independent despite covering eight orders of magnitude in hydrophobicity. Up to 35 of 99 targeted chemicals were detected in 6 tissues of 16 individuals (88 samples in total), among them legacy persistent organic pollutants (POP) such as DDT and derivatives and polychlorinated biphenyls (PCB) but also modern pesticides and chemicals present in consumer products. POPs were highest in adipose tissue and lipid-associated concentrations increased with age, while concentrations of fragrance materials such as galaxolide were independent of age. In tissues from the same individual, chemical concentrations mostly increased from similar levels in brain and blood to higher levels in liver and highest in adipose tissue. However, easily degradable chemicals such as phenanthrene were mainly detected in blood and brain, and very hydrophilic chemicals were least abundant in adipose tissue. The passive sampling method allows a direct comparison of chemical burden between different tissues and may have forensic applications, for example to study internal distributions or to use one tissue type as a proxy for others. The sum of concentrations of the detected chemicals was positively correlated with the bioassay responses but mixture modeling showed that the detected chemicals explained less than 2% of the activation of the AhR and less than 0.5% of cytotoxicity. This means that more than 10,000 chemicals would need to be included in an analytical method to capture all the effects with many chemicals potentially being below detection limits but still contributing to mixture effects. Therefore, we propose a smart combination of chemical analysis and bioassays to quantify priority chemicals but use bioassay responses as effect-scaled concentrations to capture the entire exposome in future epidemiological studies.

Suspect and non-target screening of contaminants of emerging concern in streams in agricultural watersheds

Surface water runoff is an important source of water contamination affecting nearby rivers and streams. Many rural creeks are documented habitats for important aquatic species and the focus of restoration activities. In this study, we collected creek water samples in watersheds with a range of commercial-to-agricultural land use during rain events, and applied suspect and non-target screening with high-resolution mass spectrometry (HRMS) to characterize the occurrence of contaminants of emerging concern (CECs). In total, 58 CECs were identified, and 36 of them were confirmed and semi-quantified with reference standards. Pesticides were detected in all land use, including urban/commercial areas. Some pesticides were observed at concentrations of >10,000 ng/L demonstrating the strong contamination input during rain events. Five pesticides (azoxystrobin, fludioxonil, 4-hydroxy-chlorothalonil, imidacloprid, 2-methyl-4-chlorophenoxyacetic acid) were prioritized based on their risk quotients. HRMS chemical profiles demonstrated the wide range of chemical exposures in a given stream system and that compounds associated with specific land uses occur across land uses. Temporal trends suggested that some CECs remain present in creek water for months, resulting in chronic exposures across the life stages of aquatic species. These findings highlight the potential for contamination from agricultural runoff and the associated ecological risk to aquatic species. SYNOPSIS: Suspect and non-target screening revealed the chronic occurrence of emerging contaminants in streams in agricultural catchments during rain events.

Large-scale sediment toxicity assessment over the 15,000 km of coastline in the Yellow and Bohai seas, East Asia

The Yellow and Bohai seas have long been contaminated by persistent toxic substances (PTSs) from numerous (un)known anthropogenic sources. In this study, we used Vibrio fischeri bioassay to evaluate ecotoxicological profiles associated with sedimentary PTSs contamination at a large marine ecosystem (LME) scale. A total of 125 surface sediments collected from the coastal areas of the Yellow and Bohai seas were analyzed both for aqueous and organic extracts. Not surprisingly, the results indicated site-dependent toxicities, but most sites were identified as non-toxic to V. fischeri. For aqueous extracts and organic extracts, 13% and 8% of samples, respectively exhibited marginal toxicity, while 0% and 2% of samples exhibited moderate toxicity. However, it should be noted that organic extracts (mean TU = 56) induced stronger toxicities than aqueous samples (mean TU = 0.4). This result generally back-supported the high toxicity potentials associated with sedimentary sink of organic pollutants. Several PTSs measured in the samples indicated a significant contribution to the observed V. fischeri toxicities. Of note, polycyclic aromatic hydrocarbons (PAHs; r = 0.28, p < 0.05), styrene oligomers (r = 0.41, p < 0.01), and alkylphenols (r = 0.38, p < 0.05) showed significant associations to the observed bacterial inhibition. Among PAHs, benzo[a]anthracene and phenanthrene exhibited a significant contribution to the observed V. fischeri toxicities. Meantime, salinity which reflects the distance from the point sources of land-driven pollutants along the rivers and estuaries in the Yellow and Bohai seas was a key environmental variable representing the sample toxicities. Overall, the present study provides baseline information for evaluating the potential sediment toxicity to implement responsible coastal management at an LME scale, and elsewhere.

Comprehensive characterization of tire and road wear particles in highway tunnel road dust by use of size and density fractionation

Tire and road wear particles (TRWPs) are a major component of non-exhaust traffic emissions, but knowledge about their physico-chemical properties is limited. Road dust of a highway tunnel was fractionated by size and density, and fractions were analyzed for TRWPs, metals, seven tire tread indicator chemicals (benzothiazoles, 6-PPD and DPG) and effects in in-vitro bioassays. TRWP content in tunnel dust was very high (11-12%). The peak of the TRWP mass distribution was in the size fraction 20-50 μm, with 31-36% of the total TRWP mass and a content of up to 260 mg/g. The mass of organic tire constituents peaked in the smallest analyzed size fractions (<20 μm) with 35-55% of their total mass. They also peaked in the density fraction 1.3-1.7 g/cm³, indicating a lower TRWP density and a higher contribution of TP to TRWP (approx. 75%) than expected. Video-based shape analysis and SEM showed elongated particles, likely TRWPs, to be present in those size and density fractions ascribed to TRWPs by chemical analysis. But also irregular heteroagglomerates could be found. Solvent extracts of size and density fractions induced effects in bioassays indicative of the activation of the arylhydrocarbon receptor (AhR-CALUX) and the adaptive response to oxidative stress (AREc32). Similar comprehensive characterization of road dust from other sites may be needed to decide on whether TRWPs occurring in high concentrations in tunnel dust are suited as representative test materials for analytical purposes and TRWP fate studies.

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.

Critical Membrane Concentration and Mass-Balance Model to Identify Baseline Cytotoxicity of Hydrophobic and Ionizable Organic Chemicals in Mammalian Cell Lines

All chemicals can interfere with cellular membranes and this leads to baseline toxicity, which is the minimal toxicity any chemical elicits. The critical membrane burden is constant for all chemicals; that is, the dosing concentrations to trigger baseline toxicity decrease with increasing hydrophobicity of the chemicals. Quantitative structure-activity relationships, based on hydrophobicity of chemicals, have been established to predict nominal concentrations causing baseline toxicity in human and mammalian cell lines. However, their applicability is limited to hydrophilic neutral compounds. To develop a prediction model that includes more hydrophobic and charged organic chemicals, a mass balance model was applied for mammalian cells (AREc32, AhR-CALUX, PPARγ-BLA, and SH-SY5Y) considering different bioassay conditions. The critical membrane burden for baseline toxicity was converted into nominal concentration causing 10% cytotoxicity by baseline toxicity (IC_10,baseline) using a mass balance model whose main chemical input parameter was the liposome-water partition constants (K_lip/w) for neutral chemicals or the speciation-corrected D_lip/w(pH 7.4) for ionizable chemicals plus the bioassay-specific protein, lipid, and water contents of cells and media. In these bioassay-specific models, log(1/IC_10,baseline) increased with increasing hydrophobicity, and the relationship started to level off at log D_lip/w around 2. The bioassay-specific models were applied to 392 chemicals covering a broad range of hydrophobicity and speciation. Comparing the predicted IC_10,baseline and experimental cytotoxicity IC₁₀, known baseline toxicants and many additional chemicals were identified as baseline toxicants, while the others were classified based on specificity of their modes of action in the four cell lines, confirming excess toxicity of some fungicides, antibiotics, and uncouplers. Given the similarity of the bioassay-specific models, we propose a generalized baseline-model for adherent human cell lines: log[1/IC_10,baseline (M)] = 1.23 + 4.97 × (1 - e^{-0.236 log D_lip/w}). The derived models for baseline toxicity may serve for specificity analysis in reporter gene and neurotoxicity assays as well as for planning the dosing for cell-based assays.

Exposure and Transport of Alkaloids and Phytoestrogens from Soybeans to Agricultural Soils and Streams in the Midwestern United States

Phytotoxins are naturally produced toxins with potencies similar/higher than many anthropogenic micropollutants. Nevertheless, little is known regarding their environmental fate and off-field transport to streams. To fill this research gap, a network of six basins in the Midwestern United States with substantial soybean production was selected for the study. Stream water (n = 110), soybean plant tissues (n = 8), and soil samples (n = 16) were analyzed for 12 phytotoxins (5 alkaloids and 7 phytoestrogens) and 2 widely used herbicides (atrazine and metolachlor). Overall, at least 1 phytotoxin was detected in 82% of the samples, with as many as 11 phytotoxins detected in a single sample (median = 5), with a concentration range from below detection to 37 and 68 ng/L for alkaloids and phytoestrogens, respectively. In contrast, the herbicides were ubiquitously detected at substantially higher concentrations (atrazine: 99% and metolachlor: 83%; the concentrations range from below detection to 150 and 410 ng/L, respectively). There was an apparent seasonal pattern for phytotoxins, where occurrence prior to and during harvest season (September to November) and during the snow melt season (March) was higher than that in December-January. Runoff events increased phytotoxin and herbicide concentrations compared to those in base-flow conditions. Phytotoxin plant concentrations were orders of magnitude higher compared to those measured in soil and streams. These results demonstrate the potential exposure of aquatic and terrestrial organisms to soybean-derived phytotoxins.

Removal of micropollutants and biological effects by conventional and intensified constructed wetlands treating municipal wastewater

Seven treatment wetlands and a municipal wastewater treatment plant (WWTP) were weekly monitored over the course of one year for removal of conventional wastewater parameters, selected micropollutants (caffeine, ibuprofen, naproxen, benzotriazole, diclofenac, acesulfame, and carbamazepine) and biological effects. The treatment wetland designs investigated include a horizontal subsurface flow (HF) wetland and a variety of wetlands with intensification (aeration, two-stages, or reciprocating flow). Complementary to the common approach of analyzing individual chemicals, in vitro bioassays can detect the toxicity of a mixture of known and unknown components given in a water sample. A panel of five in vitro cell-based reporter gene bioassays was selected to cover environmentally relevant endpoints (AhR: indicative of activation of the aryl hydrocarbon receptor; PPARγ: binding to the peroxisome proliferator-activated receptor gamma; ERα: activation of the estrogen receptor alpha; GR: activation of the glucocorticoid receptor; oxidative stress response). While carbamazepine was persistent in the intensified treatment wetlands, mean monthly mass removal of up to 51% was achieved in the HF wetland. The two-stage wetland system showed highest removal efficacy for all biological effects (91% to >99%). The removal efficacy for biological effects ranged from 56% to 77% for the HF wetland and 60% to 99% for the WWTP. Bioanalytical equivalent concentrations (BEQs) for AhR, PPARγ, and oxidative stress response were often below the recommended effect-based trigger (EBT) values for surface water, indicating the great benefit for using nature-based solutions for water treatment. Intensified treatment wetlands remove both individual micropollutants and mixture effects more efficiently than conventional (non-aerated) HF wetlands, and in some cases, the WWTP.

Water quality and ecological risks in European surface waters - Monitoring improves while water quality decreases

Aquatic ecosystems are at risk of being impaired by various organic chemicals, however comprehensive large-scale evaluations of waterbodies' status and trends are rare. Here, surface water monitoring data, gathered as part of the EU Water Framework Directive and comprising the occurrence of 352 organic contaminants (>8.3 mil. measurements; 2001-2015; 8213 sites) in 31 European countries, was used to evaluate past and current environmental risks for three aquatic species groups: fish, invertebrates, plants. Monitoring quality indices were defined per country and found to improve over time. Relationships became apparent between countries' monitoring quality index and their success in detecting contaminants. Across the EU, contaminants were more frequently found in recent years. Overall, 35.7% (n = 17,484) of sites exceeded at least one acute regulatory threshold level (RTL) each year, and average risks significantly increased over time for fish (τ = 0.498, p = 0.01) and aquatic invertebrates (τ = 0.429, p = 0.03). This indicates an increased chemical pressure to Europe's waterbodies and overall large-scale threshold exceedances. Pesticides were identified as the main risk drivers (>85% of RTL exceedances) with aquatic invertebrates being most acutely at risk in Europe. Agricultural land-use was clearly identified as the primary spatial driver of the observed aquatic risks throughout European surface waters. Issues in monitoring data heterogeneity were highlighted and also followed by subsequent improvement recommendations, strengthening future environmental quality assessments. Overall, aquatic ecosystem integrity remains acutely at risk across Europe, signaling the demand for continued improvements.