What you extract is what you see: Optimising the preparation of water and wastewater samples for in vitro bioassays

Comparative evaluation of SPE methods for biotoxicity assessment of water and wastewater: Linkage between chemical extracting efficiency and biotoxicity outcome

Biotoxicity assessment results of environmental waters largely depend on the sample extraction protocols that enrich pollutants to meet the effect-trigger thresholds of bioassays. However, more chemical mixture does not necessarily translate to higher combined biotoxicity. Thus, there is a need to establish the link between chemical extracting efficiency and biotoxicity outcome to standardize extraction methods for biotoxicity assessment of environmental waters. This study compares the performance of five different extraction phases in solid phase extraction (SPE), namely HLB, HLB+Coconut, C18 cartridge, C18 disk and Strata-X, and evaluated their chemical extracting efficiencies and biotoxicity outcomes. We quantitatively assessed cytotoxicity, acute toxicity, genotoxicity, estrogenic activity, and neurotoxicity of the extracts using in vitro bioassays and characterized the chemical extracting efficiencies of the SPE methods through chemical recoveries of 23 model compounds with different polarities and total organic carbon. Using Pareto ranking, we identified HLB+Coconut as the optimal SPE method, which exhibited the highest level of water sample biotoxicity and recovered the most chemicals in water samples. We found that the biotoxicity outcomes of the extracted water samples significantly and positively correlated with the chemical extracting efficiencies of the SPE methods. Moreover, we observed synchronous changing patterns in biotoxicity outcome and chemical extracting efficiencies in response to increasing sample volumes per cartridge (SVPC) during SPE. Our findings underscore that higher chemical extracting efficiency of SPE corresponds to higher biotoxicity outcome of environmental water samples, providing a scientific basis for standardization of SPE methods for adequate assessment of biotoxicities of environmental waters.

Migration of endocrine and metabolism disrupting chemicals from plastic food packaging

Plastics constitute a vast array of substances, with over 16000 known plastic chemicals, including intentionally and non-intentionally added substances. Thousands of chemicals, including toxic ones, are extractable from plastics, however, the extent to which these compounds migrate from everyday products into food or water remains poorly understood. This study aims to characterize the endocrine and metabolism disrupting activity, as well as the chemical composition of migrates from plastic food contact articles (FCAs) from four countries as significant sources of human exposure. Fourteen plastic FCAs covering seven polymer types with high global market shares were migrated into water and a water-ethanol mixture as food simulants according to European regulations. The migrates were analyzed using reporter gene assays for nuclear receptors relevant to human health and non-target chemical analysis to characterize the chemical composition. Chemicals migrating from each FCA interfered with at least two nuclear receptors, predominantly targeting pregnane X receptor (24/28 migrates). Moreover, peroxisome proliferator receptor gamma was activated by 19 out of 28 migrates, though mostly with lower potencies. Estrogenic and antiandrogenic activity was detected in eight and seven migrates, respectively. Fewer chemicals and less toxicity migrated into water compared to the water-ethanol mixture. However, 73 % of the 15 430 extractable chemical features also transferred into food simulants, and the water-ethanol migrates exhibited a similar toxicity prevalence compared to methanol extracts. The chemical complexity differed largely between FCAs, with 8 to 10631 chemical features migrating into food simulants. Using stepwise partial least squares regressions, we successfully narrowed down the list of potential active chemicals, identified known endocrine disrupting chemicals, such as triphenyl phosphate, and prioritized chemical features for further identification. This study demonstrates the migration of endocrine and metabolism disrupting chemicals from plastic FCAs into food simulants, rendering a migration of these compounds into food and beverages probable.

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.

Estrogenic activity in wastewater treatment plants through in vitro effect-based assays: Insights into extraction phase

Effluents of wastewater treatment plants can abundantly spread endocrine disrupting chemicals in the environment. To improve water quality monitoring, the use of effect-based tools that measure estrogenic activity has been suggested, however their results could be influenced by different factors. This study compared the estrogenic activity of wastewater samples extracted with two stationary phases and tested with two in vitro effect-based assays to investigate whether and how stationary phases and assays could influence biomonitoring data. During four seasonal periods, the effluents of six WWTPs located in northern Italy were sampled. After the extraction using two different stationary phases (HLB, C18), the samples (n = 72) were tested using two effect-based assays: a gene reporter luciferase assay on mammalian cells (MELN) and yeast estrogen screen assay (YES). The results showed that estrogenic activity of HLB extracts was significantly different from the activity of C18 extracts, suggesting that extraction phase can influence biomonitoring data. Moreover, the estrogenic activity was overall higher using gene reporter MELN assay than using YES assay, suggesting that, due to difference in cell membrane permeability and metabolic activation, the applied cell model can affect the biomonitoring results. Finally, from the comparison between the activity of the final effluent and the environmentally safe estrogenic levels in surface waters, MELN data suggested that the activity of this effluent may pose an environmental risk, while YES data showed that it should not be considered a threat to the receiving surface waters. This study pointed out that a standardized approach is needed to assess the estrogenic activity of waters; it reported important data to select the most suitable stationary phase for samples extraction (samples extracted with C18 sorbent showed higher estradiol equivalent concentration values) and the most appropriate bioassay (gene reporter luciferase MELN assay was more sensitive than YES assay) to assess the environmental risk, thus protecting human health.

In silico ecotoxicity assessment of pharmaceutical residues in wastewater following oxidative treatment

Advanced oxidation processes such as thermal plasma activation and UV-C/H2O2 treatment are considered as applications for the degradation of pharmaceutical residues in wastewater complementary to conventional wastewater treatment. It is supposed that direct oxidative treatment can lower the toxicity of hospital sewage water (HSW). The aim of this study was to predict the ecotoxicity for three aquatic species before and after oxidative treatment of 10 quantified pharmaceuticals in hospital sewage water. With the application of oxidative chemistry, pharmaceuticals are degraded into transformation products before reaching complete mineralization. To estimate the potential ecotoxicity for fish, Daphnia and green algae ECOSAR quantitative structure-activity relationship software was used. Structure information from pristine pharmaceuticals and their oxidative transformation products were calculated separately and in a mixture computed to determine the risk quotient (RQ). Calculated mixture toxicities for 10 compounds found in untreated HSW resulted in moderate-high RQ predictions for all three aquatic species. Compared to untreated HSW, 30-min treatment with thermal plasma activation or UV-C/H2O2 resulted in lowered RQs. For the expected transformation products originating from fluoxetine, cyclophosphamide and acetaminophen increased RQs were predicted. Prolongation of thermal plasma oxidation up to 120 min predicted low-moderate toxicity in all target species. It is anticipated that further degradation of oxidative transformation products will end in less toxic aliphatic and carboxylic acid products. Predicted RQs after UV-C/H2O2 treatment turned out to be still moderate-high. In conclusion, in silico extrapolation of experimental findings can provide useful predicted estimates of mixture toxicity. However due to the complex composition of wastewater this in silico approach is a first step to screen for ecotoxicity. It is recommendable to confirm these predictions with ecotoxic bioassays.

Impact of sample acidification and extract storage on hormone receptor-mediated and oxidative stress activities in wastewater

An underemphasized aspect of sampling strategies in effect-based in vitro testing is to determine suitable collection and preparation techniques. In the current study, the impact of sample acidification on bioactivities was assessed using in vitro bioassays for hormone receptor-mediated effects (estrogen receptor [ER] and androgen receptor [AR]) and the oxidative stress response (Nrf2 activity). Sampling was conducted at a recently upgraded Swedish wastewater treatment plant. Future plans for the treated wastewater include reuse for irrigation or as a potential drinking water source. In the AR and Nrf2 assays, acidification decreased bioactivities in the wastewater influent sample extracts, whereas acidification increased bioactivities following further treatment (disc filtration). In the ER assay, acidification had no impact on the observed bioactivities in the sample extracts. A secondary objective of the study was to assess the stability of the sample extracts over time. Lower activities were detected in the ER and AR assays in all extracts after storage for approximately 1 year. Nrf2 activities did not decrease over time, but rather increased in some of the acidified sample extracts. Overall, the findings suggest that sampling strategies involving acidification may need to be tailored depending on the selected bioassay(s) and the type of wastewater treatments being assessed.

Individual and combined ecotoxic effects of water-soluble polymers

Water-soluble polymers (WSPs) are a class of high-molecular-weight compounds which are widely used in several applications, including water treatment, food processing, and pharmaceuticals. Therefore, they pose a potential threat for water resources and aquatic ecosystems. We assessed the ecotoxicity of four WSPs-non-ionic polyacrylamide (PAM) and polyethylene glycol (PEG-200), anionic homopolymer of acrylic acid (P-AA), and cationic polyquaternium-6 (PQ-6)-as single compounds and in mixture. For this purpose in vitro and in vivo assays were used to record baseline toxicity, mutagenic potential, endocrine effects, and growth inhibition in the freshwater alga Raphidocelis subcapitata. Furthermore, the mixture toxicity of the two polymers P-AA and PQ-6 which showed effects in the algae tests was evaluated with the concentration addition (CA), independent action (IA), and generalized concentration addition (GCA) model and compared with experimental data. No toxic effects were observed among the polymers and their mixtures in the in vitro assays. On the contrary, in the growth inhibition test with R. subcapitata the cationic PQ-6 caused high inhibition while the anionic P-AA and its mixture with the cationic polymer caused low inhibition. The non-ionic polymers PEG-200 and PAM showed no effect in R. subcapitata in the tested concentration range up to 100 mg/L. The IA model represented the mixture effect of the combination experiment better than the CA and GCA models. The results indicate (1) that the toxic effects of anionic and cationic polymers are most likely due to interactions of the polymers with the surfaces of organisms or with nutrients in the water and (2) that the polymers elicit their effects through different mechanisms of action that do not interact with each other.

Application of Effect-Based Methods to Water Quality Monitoring: Answering Frequently Asked Questions by Water Quality Managers, Regulators, and Policy Makers

Effect-based methods (EBM) have great potential for water quality monitoring as they can detect the mixture effects of all active known and unknown chemicals in a sample, which cannot be addressed by chemical analysis alone. To date, EBM have primarily been applied in a research context, with a lower level of uptake by the water sector and regulators. This is partly due to concerns regarding the reliability and interpretation of EBM. Using evidence from the peer-reviewed literature, this work aims to answer frequently asked questions about EBM. The questions were identified through consultation with the water industry and regulators and cover topics related to the basis for using EBM, practical considerations regarding reliability, sampling for EBM and quality control, and what to do with the information provided by EBM. The information provided in this work aims to give confidence to regulators and the water sector to stimulate the application of EBM for water quality monitoring.

Identification of high-concern organic pollutants in tap waters from the Yangtze River in China based on combined screening strategies

Recently, numerous organic pollutants have been detected in water environment. The safety of our drinking water has attracted widespread attention. Effective methods to screen and identify high-concern substances are urgently needed. In this study, the combined workflow for the detection and identification of high-concern organic chemicals was established and applied to tap water samples from the Yangtze River Basin. The solid phase extraction (SPE) sorbents were compared and evaluated and finally the HLB cartridge was selected as the best one for most of the contaminants. Based on target, suspect and non-target analysis, 3023 chemicals/peaks were detected. Thirteen substances such as diundecyl phthalate (DUP), 2-hydroxyatrazine, dioxoaminopyrine and diethyl-2-phenylacetamide were detected in drinking water in the Yangtze River Basin for the very first time. Based on three kinds of prioritization principles, 49 ubiquitous, 103 characteristic chemicals and 13 inefficiently removed chemicals were selected as high-concern substances. Among them, 8, 31, 9, 3, 4 substances overlapped with the toxic, risky or high-concern chemicals lists in China, America, European Union, Japan, Korea, respectively. Specific management and removal strategies were further recommended. The workflow is efficient for identification of key pollutants.

Chemical and toxicological assessment of leachates from UV-degraded plastic materials using in-vitro bioassays

The broad use of plastics and the persistence of the material results in plastic residues being found practically everywhere in the environment. If plastics remain in the (aquatic) environment, natural weathering leads to degradation processes and compounds may leach from plastic into the environment. To investigate the impact of degradation process on toxicity of leachates, different types of UV irradiation (UV-C, UV-A/B) were used to simulate weathering processes of different plastic material containing virgin as well as recyclate material and biodegradable polymers. The leached substances were investigated toxicologically using in-vitro bioassays. Cytotoxicity was determined by the MTT-assay, genotoxicity by using the p53-CALUX and Umu-assay, and estrogenic effects by the ERα-CALUX. Genotoxic as well as estrogenic effects were detected in different samples depending on the material and the irradiation type. In four leachates of 12 plastic species estrogenic effects were detected above the recommended safety level of 0.4 ng 17β-estradiol equivalents/L for surface water samples. In the p53-CALUX and in the Umu-assay leachates from three and two, respectively, of 12 plastic species were found to be genotoxic. The results of the chemical analysis show that plastic material releases a variety of known and unknown substances especially under UV radiation, leading to a complex mixture with potentially harmful effects. In order to investigate these aspects further and to be able to give recommendations for the use of additives in plastics, further effect-related investigations are advisable.

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

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

The role of effect-based methods to address water quality monitoring in South Africa: a developing country's struggle

Water is an important resource, and it is a worldwide struggle to provide water of good quality to the whole population. Despite good governing laws and guidelines set in place to help protect the water resources and ensure it is of good quality for various consumers, the water quality in South Africa is worsening due to lack of management. The deteriorating infrastructure is becoming progressively worse, due to corruption and insufficient funds. The ever-increasing number of toxicants, as well as the identification of emerging chemicals of concern, are also challenges South Africa is facing. Chemical analysis cannot determine the total biological effect of a mixture of chemical compounds, but this shortcoming can be addressed by adding effect-based methods (EBMs) to water quality monitoring programmes. In this paper, the current status of water quality monitoring in South Africa is discussed, as well as the capacity of the country to add EBMs to its water quality monitoring programmes to protect and improve human and animal life. Created in Biorender.com.

Determination of cytotoxicity following oxidative treatment of pharmaceutical residues in wastewater

Pharmaceutical residues are released in the aquatic environment due to incomplete removal from wastewater. With the presence of multiple chemicals in sewage waters, contaminants may adversely affect the effectiveness of a wastewater treatment plant (WWTP). In certain cases, discharged metabolites are transformed back into their pristine structure and become bioactive again. Other compounds are persistent and can withstand conventional wastewater treatment. When WWTP effluents are released in surface waters, pristine and persistent chemicals can affect the aquatic environment. To complement WWTPs and circumvent incomplete removal of unwanted chemicals or pharmaceuticals, on-site wastewater treatment can contribute to their removal. Advanced oxidation processes (AOPs) are very powerful techniques for the abatement of pharmaceuticals, however, under certain circumstances reactive toxic by-products can be produced. We studied the application of on-site AOPs in a laboratory setting. It is expected that treatment at the contamination source can eliminate the worst polluters. Thermal plasma and UV/H₂O₂ oxidation were applied on simulation matrices, Milli-Q and synthetic sewage water spiked with 10 different pharmaceuticals in a range of 0.1 up to 2400 μg/L. In addition, untreated end-of-pipe hospital effluent was also subjected to oxidative treatment. The matrices were activated for 180 min and added to cultured HeLa cells. The cells were 24 h and 48 h exposed at 37 °C and subsequently markers for oxidative stress and viability were measured. During the UV/H₂O₂ treatment periods no toxicity was observed. After thermal plasma activation of Milli-Q water (150 and 180 min) toxicity was observed. Direct application of thermal plasma treatment in hospital sewage water caused elimination of toxic substances. The low cytotoxicity of treated pharmaceutical residues is likely to become negligible if plasma pre-treated on-site wastewater is further diluted with other sewage water streams, before reaching the WWTP. Our study suggests that AOPs may be promising technologies to remove a substantial portion of pharmaceutical components by degradation at the source. Further studies will have to be performed to verify the feasibility of upscaling this technology from the benchtop to practice.

Assessing the protection gap for mobile and persistent chemicals during advanced water treatment - A study in a drinking water production and wastewater treatment plant

Persistent and mobile (PM) chemicals spread quickly in the water cycle and can reach drinking water. If these chemicals are also toxic (PMT) they may pose a threat to the aquatic environment and drinking water alike, and thus measures to prevent their spread are necessary. In this study, nontarget screening and cell-based toxicity tests after a polarity-based fractionation into polar and non-polar chemicals are utilized to assess and compare the effectiveness of ozonation and filtration through activated carbon in a wastewater treatment and drinking water production plant. Especially during wastewater treatment, differences in removal efficiency were evident. While median areas of non-polar features were reduced by a factor of 270, median areas for polar chemicals were only reduced by a factor of 4. Polar features showed significantly higher areas than their non-polar counterparts in wastewater treatment plant effluent and finished drinking water, implying a protection gap for these chemicals. Toxicity tests revealed higher initial toxicities (especially oxidative stress and estrogenic activity) for the non-polar fraction, but also showed a more pronounced decrease during treatment. Generally, the toxicity of the effluent was low for both fractions. Combined, these results imply a less effective removal but also a lower toxicity of polar chemicals. The behaviour of features during advanced waste and drinking water treatment was used to classify them as either PM chemicals or mobile transformation products (M-TPs). A suspect screening of the 476 highest intensity PM chemicals and M-TPs in 57 environmental and tap water samples showed high frequencies of detection (median >80%), which indicates the wide distribution of these chemicals in the aquatic environment and thus supports the chosen classification approach and the more generally applicability of obtained insights.

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.

Evaluation of a full-scale wastewater treatment plant with ozonation and different post-treatments using a broad range of in vitro and in vivo bioassays

Micropollutants present in the effluent of wastewater treatment plants (WWTPs) after biological treatment are largely eliminated by effective advanced technologies such as ozonation. Discharge of contaminants into freshwater ecosystems can thus be minimized, while simultaneously protecting drinking water resources. However, ozonation can lead to reactive and potentially toxic transformation products. To remove these, the Swiss Federal Office for the Environment recommends additional "post-treatment" of ozonated WWTP effluent using sand filtration, but other treatments may be similarly effective. In this study, 48 h composite wastewater samples were collected before and after full-scale ozonation, and after post-treatments (full-scale sand filtration, pilot-scale fresh and pre-loaded granular activated carbon, and fixed and moving beds). Ecotoxicological tests were performed to quantify the changes in water quality following different treatment steps. These included standard in vitro bioassays for the detection of endocrine, genotoxic and mutagenic effects, as well as toxicity to green algae and bacteria, and flow-through in vivo bioassays using oligochaetes and early life stages of rainbow trout. Results show that ozonation reduced a number of ecotoxicological effects of biologically treated wastewater by 66 - 93%: It improved growth and photosynthesis of green algae, decreased toxicity to luminescent bacteria, reduced concentrations of hormonally active contaminants and significantly changed expression of biomarker genes in rainbow trout liver. Bioassay results showed that ozonation did not produce problematic levels of reaction products overall. Small increases in toxicity observed in a few samples were reduced or eliminated by post-treatments. However, only relatively fresh granular activated carbon (analyzed at 13,000 - 20,000 bed volumes) significantly reduced effects additionally (by up to 66%) compared to ozonation alone. Inhibition of algal photosynthesis, rainbow trout liver histopathology and biomarker gene expression proved to be sufficiently sensitive endpoints to detect the change in water quality achieved by post-treatment.

An in vitro-based hazard assessment of liquid smoke food flavourings

Liquid smoke products are widely used as a food additive to create a desired smoke flavour. These products may contain hazardous chemicals generated during the wood-burning process. However, the toxic effects of these types of hazardous chemicals constituting in the commercially available products are largely unknown. Therefore, a test battery of cell-based in vitro methods, covering different modes of actions of high relevance to human health, was applied to study liquid smoke products. Ten liquid smoke flavourings were tested as non-extracted and extracted. To assess the potential drivers of toxicity, we used two different solvents. The battery of in vitro methods covered estrogenicity, androgenicity, oxidative stress, aryl hydrocarbon receptor activity and genotoxicity. The non-extracted samples were tested at concentrations 0.002 to 1 μL liquid smoke flavouring/mL culture medium, while extracted samples were tested from 0.003 to 200 μL/mL. Genotoxicity was observed for nearly all non-extracted and all hexane-extracted samples, in which the former had higher potency. No genotoxicity was observed for ethyl acetate-extracted samples. Oxidative stress was activated by almost all extracted and non-extracted samples, while approximately half of the samples had aryl hydrocarbon receptor and estrogen receptor activities. This study used effect-based methods to evaluate the complex mixtures of liquid smoke flavourings. The increased bioactivities seen upon extractions indicate that non-polar chemicals are driving the genotoxicity, while polar substances are increasing oxidative stress and cytotoxic responses. The differences in responses indicate that non-extracted products contain chemicals that are able to antagonize toxic effects, and upon extraction, the protective substances are lost.

Plastic Products Leach Chemicals That Induce In Vitro Toxicity under Realistic Use Conditions

Plastic products contain complex mixtures of extractable chemicals that can be toxic. However, humans and wildlife will only be exposed to plastic chemicals that are released under realistic conditions. Thus, we investigated the toxicological and chemical profiles leaching into water from 24 everyday plastic products covering eight polymer types. We performed migration experiments over 10 days at 40 °C and analyzed the migrates using four in vitro bioassays and nontarget high-resolution mass spectrometry (UPLC-QTOF-MS^E). All migrates induced baseline toxicity, 22 an oxidative stress response, 13 antiandrogenicity, and one estrogenicity. Overall, between 17 and 8681 relevant chemical features were present in the migrates. In other words, between 1 and 88% of the plastic chemicals associated with one product were migrating. Further, we tentatively identified ∼8% of all detected features implying that most plastic chemicals remain unknown. While low-density polyethylene, polyvinyl chloride, and polyurethane induced most toxicological endpoints, a generalization for other materials is not possible. Our results demonstrate that plastic products readily leach many more chemicals than previously known, some of which are toxic in vitro. This highlights that humans are exposed to many more plastic chemicals than currently considered in public health science and policies.

Enhanced in vitro toxicity of plastic leachates after UV irradiation

Plastics can release numerous chemicals and thereby, contribute to the chemical pollution in aquatic systems. To which extent environmental degradation processes influence the release of plastic chemicals, is currently unknown and subject of research. We therefore evaluated aqueous leachates of 12 differently formulated plastics (e.g., pre-production, post-industrial and recycled pellets as well as final products) using in vitro bioassays and chemical analysis via LC-HRMS nontarget approach. We weathered these plastics by UV irradiation (UV-C and UV-A/B) under laboratory conditions in dryness and a subsequent leaching period in ultrapure water ('atmospheric' weathering) or directly in water ('aquatic' weathering, UV-A/B_aq). A dark control (DC) without UV light served as a reference treatment. Some plastics triggered several toxicological endpoints (low-density polyethylene recyclate (LDPE-R), starch blend (SB), bio-based polybutylene succinate (Bio-PBS) and polyvinyl chloride (PVC)), whereas others caused little to no effects (polyethylene terephthalate (PET), polystyrene (PS), polypropylene (PP) and LDPE). UV irradiation enhanced the plastics' toxicity, even for samples initially evaluated as toxicologically inconspicuous. The plastic samples caused oxidative stress (85%), baseline toxicity (42%), antiestrogenicity (40%) and antiandrogenicity (27%). Positive findings were measured after UV-C (63%) and UV-A/B_aq (50%) treatments, followed by UV-A/B (48%) and DC (33%). Overall, we detected between 42 (DC) and 2896 (UV-A/B_aq) chemical compounds. Our study demonstrates that differently formulated plastics leach toxic chemicals. UV exacerbates the plastics' toxicity by either generating active compounds and/or by facilitating their release. UV light even leads to the release of bioactive compounds from plastics of low chemical complexity. To prevent the exposure to plastic-associated chemicals, the application of chemicals could be reduced to a minimum, while on a regulatory level the evaluation of plastic eluates could be another focal point next to singular compounds.

Effect-based evaluation of ozone treatment for removal of micropollutants and their transformation products in waste water

The aim of this interdisciplinary research project in North Rhine-Westphalia (NRW), Germany, entitled "Elimination of pharmaceuticals and organic micropollutants from waste water" involved the conception of cost-effective and innovative waste-water cleaning methods. In this project in vitro assays, in vivo assays and chemical analyses were performed on three municipal waste-water treatment plants (WWTP). This publication focuses on the study of the in vitro bioassays. Cytotoxic, estrogenic, genotoxic and mutagenic effects of the original as well as enriched water samples were monitored before and after wastewater treatment steps using MTT and PAN I, ER Calux and A-YES, micronucleus and Comet assays as well as AMES test. In most cases, the measured effects were reduced after ozonation, but in general, the biological response depended upon the water composition of the WWTP, in particular on the formed by-products and concentration of micropollutants. In order to be able to assess the genotoxic and/or mutagenic potential of waste-water samples using bioassays like Ames test, Comet assay or micronucleus test an enrichment of the water sample via solid-phase extraction is recommended. This is in agreement with previous studies such as the "ToxBox"-Project of the Environmental Agency in Germany.

Reactivity-directed analysis - a novel approach for the identification of toxic organic electrophiles in drinking water

Drinking water consumption results in exposure to complex mixtures of organic chemicals, including natural and anthropogenic chemicals and compounds formed during drinking water treatment such as disinfection by-products. The complexity of drinking water contaminant mixtures has hindered efforts to assess associated health impacts. Existing approaches focus primarily on individual chemicals and/or the evaluation of mixtures, without providing information about the chemicals causing the toxic effect. Thus, there is a need for the development of novel strategies to evaluate chemical mixtures and provide insights into the species responsible for the observed toxic effects. This critical review introduces the application of a novel approach called Reactivity-Directed Analysis (RDA) to assess and identify organic electrophiles, the largest group of known environmental toxicants. In contrast to existing in vivo and in vitro approaches, RDA utilizes in chemico methodologies that investigate the reaction of organic electrophiles with nucleophilic biomolecules, including proteins and DNA. This review summarizes the existing knowledge about the presence of electrophiles in drinking water, with a particular focus on their formation in oxidative treatment systems with ozone, advanced oxidation processes, and UV light, as well as disinfectants such as chlorine, chloramines and chlorine dioxide. This summary is followed by an overview of existing RDA approaches and their application for the assessment of aqueous environmental matrices, with an emphasis on drinking water. RDA can be applied beyond drinking water, however, to evaluate source waters and wastewater for human and environmental health risks. Finally, future research demands for the detection and identification of electrophiles in drinking water via RDA are outlined.

Chemicals associated with biodegradable microplastic drive the toxicity to the freshwater oligochaete Lumbriculus variegatus

Microplastics (MPs) as complex synthetic pollutants represent a growing concern for the aquatic environment. Previous studies examined the toxicity of MPs, but infrequently used a natural particle control such as kaolin. The cause of toxicity, either the physical structure of the particles or chemical components originating from the MPs, has rarely been resolved. Moreover, the ecotoxicological assessment of biodegradable plastics has received little attention. To narrow down the main driver for toxicity of irregular biodegradable MPs, we conducted a series of 28-days sediment toxicity tests with the freshwater oligochaete Lumbriculus variegatus and recorded the number of worms and dry weight as endpoints. Therefore, MPs containing several biodegradable polymers were either mixed with the sediment or layered on the sediment surface with concentrations from 1 to 8.4% sediment dw^-1. Kaolin particles were evaluated in parallel as particle control. Furthermore, aqueous leachates and methanolic extracts as MP equivalents as well as solvent-treated, presumably pure MPs were investigated after mixing them into the sediment. Our results reveal that MP mixed with the sediment induced stronger adverse effects than layered MP. Kaolin particles caused no adverse effects. In contrast, they enhanced dry weight in both applications. The impact of aqueous leachates was comparable to the control without MPs, whereas methanolic extracts affected the worm number at the highest concentration with 100% mortality. Solvent-treated, presumably pure MP resulted in mostly higher worm numbers when compared to untreated MPs mixed into the sediment. This study demonstrates that MPs mixed into the sediment affect L. variegatus more than MPs that are layered on the sediment surface. Kaolin as a natural, fine-sized particle control created somewhat favorable conditions for the worm. The main driver for toxicity, however, proved to be chemicals associated with the plastic product and its previous content.

Assessment of chemical mixtures using biomarkers of combined biological activity: A screening study in human placentas

Humans are simultaneously exposed to complex mixtures of chemicals with limited knowledge on potential health effects, therefore improved tools for assessing these mixtures are needed. As part of the Human Biomonitoring for Europe (HBM4EU) Project, we aimed to examine the combined biological activity of chemical mixtures extracted from human placentas using one in vivo and four in vitro bioassays, also known as biomarkers of combined effect. Relevant endocrine activities (proliferative and/or reporter gene assays) and four endpoints were tested: the estrogen receptor (ER), androgen receptor (AR), and aryl hydrocarbon receptor (AhR) activities, as well as thyroid hormone (TH) signaling. Correlations among bioassays and their functional shapes were evaluated. Results showed that all placental extracts agonized or antagonized at least three of the abovementioned endpoints. Most placentas induced ER-mediated transactivation and ER-dependent cell proliferation, together with a strong inhibition of TH signaling and the AR transactivity; while the induction of the AhR was found in only one placental extract. The effects in the two estrogenic bioassays were positively and significantly correlated and the AR-antagonism activity showed a positive borderline-significant correlation with both estrogenic bioassay activities. However, the in vivo anti-thyroid activities of placental extracts were not correlated with any of the tested in vitro assays. Findings highlight the importance of comprehensively mapping the biological effects of "real-world" chemical mixtures present in human samples, through a battery of in vitro and in vivo bioassays. This approach should be a complementary tool for epidemiological studies to further elucidate the combined biological fingerprint triggered by chemical mixtures.

Genotoxic activities of wastewater after ozonation and activated carbon filtration: Different effects in liver-derived cells and bacterial indicators

Aim of this study was to investigate the impact of advanced wastewater treatment techniques (combining ozonation with activated carbon filtration) on acute and genotoxic activities of tertiary treated wastewater. Concentrated samples were tested in Salmonella/microsome assays. Furthermore, induction of DNA damage was measured in liver-derived cells (human hepatoma and primary rat hepatocytes) in single cell gel electrophoresis experiments, which are based on the measurement of DNA migration in an electric field. These cell types possess phase I and phase II enzymes, which catalyze the activation/detoxification of mutagens. Acute toxicity was determined with the trypan blue exclusion technique. We found no evidence for mutagenic effects of non-ozonated samples in several bacterial tester strains (TA98, TA100, YG7108, YG7104, YG7112 and YG7113) but clear induction of His⁺ mutants after O₃ treatment in two strains with defective genes encoding for DNA repair, which are highly sensitive towards alkylating agents (YG7108 and YG7104). These effects were reduced after activated carbon filtration. Furthermore, we detected a slight increase of mutagenic activity in strain YG1024 with increased acetyltransferase activity, which is sensitive towards aromatic amines and nitro compounds in untreated water, which was not reduced by O₃ treatment. A completely different pattern of mutagenic activity was seen in liver-derived cells; non ozonated samples caused in both cell types pronounced DNA damage, which was reduced (by ca. 25%) after ozonation. Activated carbon treatment did not cause a substantial further reduction of DNA damage. Additional experiments with liver homogenate indicate that the compounds which cause the effects in the human cells are promutagens which require enzymatic activation. None of the waters caused acute toxicity in the liver-derived cells and in the bacterial indicators. Assuming that hepatic mammalian cells reflect the genotoxic properties of the waters in vertebrates (including humans) more adequately as genetically modified bacterial indicators, we conclude that ozonation has beneficial effects in regard to the reduction of genotoxic properties of treated wastewaters.

Enhancing solar disinfection (SODIS) with the photo-Fenton or the Fe2+/peroxymonosulfate-activation process in large-scale plastic bottles leads to toxicologically safe drinking water

Solar disinfection (SODIS) in 2-L bottles is a well-established drinking water treatment technique, suitable for rural, peri‑urban, or isolated communities in tropical or sub-tropical climates. In this work, we assess the enlargement of the treatment volume by using cheap, large scale plastic vessels. The bactericidal performance of SODIS and two solar-Fe²⁺ based enhancements, namely photo-Fenton (light/H₂O₂/Fe²⁺) and peroxymonosulfate activation (light/PMS/Fe²⁺) were assessed in 19-L polycarbonate (PC) and 25-L polyethylene terephthalate (PET) bottles, in ultrapure and real water matrices (tap water, lake Geneva water). Although SODIS always reached total (5-logU) inactivation, under solar light, enhancement by or both Fe²⁺/H₂O₂ or Fe²⁺/PMS was always beneficial and led to an increase in bacterial elimination kinetics, as high as 2-fold in PC and PET bottles with tap water for light/H₂O₂/Fe²⁺, and 8-fold in PET bottles with Lake Geneva water. The toxicological safety of the enhancements and their effects on the plastic container materials was assessed using the E-screen assay and the Ames test, after 1-day or 1-week exposure to SODIS, photo-Fenton and persulfate activation. Although the production of estrogenic compounds was observed, we report that no treatment method, duration of exposure or material resulted in estrogenicity risk for humans, and similarly, no mutagenicity risk was measured. In summary, we suggest that SODIS enhancement by either HO^•- or SO₄^•--based advanced oxidation process is a suitable enhancement of bacterial inactivation in large scale plastic bottles, without any associated toxicity risks.

Post-treatment of ozonated wastewater with activated carbon and biofiltration compared to membrane bioreactors: Toxicity removal in vitro and in Potamopyrgus antipodarum

Wastewater treatment plants are major point sources of (micro)pollutant emissions and advanced wastewater treatment technologies can improve their removal capacity. While abundant data on individual advanced treatment technologies is available, there is limited knowledge regarding the removal performance of ozonation combined with multiple post-treatments and stand-alone membrane bioreactors. This is especially true for the removal of in vitro and in vivo toxicity. Therefore, we investigated the removal of 40 micropollutants and toxicity by a pilot-scale ozonation with four post-treatments: non-aerated and aerated granular activated carbon and biological filtration. In addition, two stand-alone membrane bioreactors fed with untreated wastewater and one MBR operating with ozonated partial flow recirculation were analysed. Aqueous and extracted samples were analysed in vitro for (anti)estrogenic, (anti)androgenic and mutagenic effects. To assess in vivo effects, the mudsnail Potamopyrgus antipodarum was exposed in an on-site flow-through system. Multiple in vitro effects were detected in conventionally treated wastewater including estrogenic and anti-androgenic activity. Ozonation largely removed these effects, while anti-estrogenic and mutagenic effects increased suggesting the formation of toxic transformation products. These effects were significantly reduced by granular activated carbon being more effective than biological filtration. The membrane bioreactor performed similarly to the conventional treatment while the membrane bioreactor with ozonation had a comparable removal performance like ozonation. Conventionally treated wastewater increased the growth of P. antipodarum. Ozonation reduced the reproduction indicating a potential formation of toxic transformation products. In the post-treatments, these effects were compensated or remained unaffected. The effluents of the membrane bioreactors induced reproductive toxicity. Our results show that ozonation is effective in further reducing toxicity and micropollutant concentrations. However, the formation of toxicity requires a post-treatment. Here, ozonation coupled to granular activated carbon filtration seemed the most promising treatment process.

Water toxicity evaluations: Comparing genetically modified bioluminescent bacteria and CHO cells as biomonitoring tools

The use of water for drinking and agriculture requires knowledge of its toxicity. In this study, we compared the use of genetically modified bioluminescent (GMB) bacteria whose luminescence increases in the presence of toxicants and Chinese Hamster Ovary (CHO) cells for the characterization of the toxicity of water samples collected from a lake and streams, hydroponic and aquaponic farms, and a wastewater treatment plant. GMB bacteria were used to probe genotoxicity, cytotoxicity and reactive oxygen species-induced effects in the whole water samples. Unlike GMB bacteria, the use of CHO cells requires XAD resin-based pre-concentration of toxic material present in water samples for the subsequent cytotoxicity assay. In addition to the examination of the toxicity of the water from the different sources, the GMB bacteria were also used to test the XAD extracts diluted to the concentrations causing 50% growth inhibition of the CHO cells. The two biomonitoring tools provided different results when they were used to test the above-mentioned diluted XAD extracts. A pre-concentration procedure based on adsorption by XAD resins with subsequent elution was not sufficient to represent the material responsible for the toxicity of the whole water samples toward the GMB bacteria. Therefore, the use of XAD resin extracts may lead to major underestimates of the toxicity of water samples. Although the toxicity findings obtained using the GMB bacteria and CHO cells may not correlate with each another, the GMB bacteria assay did provide a mechanism-specific biomonitoring tool to probe the toxicity of water samples without a need for the pre-concentration step.

Advancements in effect-based surface water quality assessment

Legally-prescribed chemical monitoring is unfit for determining the pollution status of surface waters, and there is a need for improved assessment methods that consider the aggregated risk of all bioavailable micropollutants present in the aquatic environment. Therefore, the present study aimed to advance effect-based water quality assessment by implementing methodological improvements and to gain insight into contamination source-specific bioanalytical responses. Passive sampling of non-polar and polar organic compounds and metals was applied at 14 surface water locations that were characterized by two major anthropogenic contamination sources, agriculture and wastewater treatment plant (WWTP) effluent, as well as reference locations with a low expected impact from micropollutants. Departing from the experience gained in previous studies, a battery of 20 in vivo and in vitro bioassays was composed and subsequently exposed to the passive sampler extracts. Next, the bioanalytical responses were divided by their respective effect-based trigger values to obtain effect-based risk quotients, which were summed per location. These cumulative ecotoxicological risks were lowest for reference locations (4.3-10.9), followed by agriculture locations (11.3-27.2) and the highest for WWTP locations (12.8-47.7), and were mainly driven by polar organic contaminants. The bioanalytical assessment of the joint risks of metals and (non-)polar organic compounds resulted in the successful identification of pollution source-specific ecotoxicological risk profiles: none of the bioassays were significantly associated with reference locations nor with multiple location types, while horticulture locations were significantly characterized by anti-AR and anti-PR activity and cytotoxicity, and WWTP sites by ERα activity and toxicity in the in vivo bioassays. It is concluded that the presently employed advanced effect-based methods can readily be applied in surface water quality assessment and that the integration of chemical- and effect-based monitoring approaches will foster future-proof water quality assessment strategies on the road to a non-toxic environment.

Selection of assay, organism, and approach in biomonitoring significantly affects the evaluation of genotoxic potential in aquatic environments

In this study, few different evaluation concepts were used for the assessment of genotoxic potential at the stretch of the Danube River identified as a significant hotspot of pollution originated through the untreated wastewaters. Three sites were chosen: one site upstream of the wastewater outlet in Novi Sad (Serbia), one at the outlet of wastewaters, and one site few kilometer downstream. Ex situ approach comprised prokaryotic SOS/umuC test on Salmonella typhimurium TA1535/pSK1005 and comet assay on human hepatoma cell line (HepG2). In situ approach was based on the active monitoring (cage approach) using freshwater mussels Sinanodonta woodiana and fish Cyprinus carpio. The comet and micronucleus assays were selected for evaluation of DNA damage in mussel haemocytes and fish blood cells. Within the ex situ part of the study, our results indicated that the eukaryotic model system is more sensitive compared to the prokaryotic one. In situ bioassays are recommended for obtaining a better insight into ecosystem status and in the case of our study the complete insight of genotoxic pressure. However, the choice of animals as bioindicators also has a significant impact on the quality of the obtained information. Differential response between fish and mussels was observed at the highly polluted site suggesting possible involvement of additional protective mechanism such as valve closure in mussels.

Exclusion of Estrogenic and Androgenic Steroid Hormones from Municipal Membrane Bioreactor Wastewater Using UF/NF/RO Membranes for Water Reuse Application

In the context of water scarcity, domestic secondary effluent reuse may be an option as a reliable source for alleviating acute water shortage. The increasing risks linked with the presence of natural steroid hormones and many emerging anthropogenic micropollutants (MPs) passing through municipal wastewater treatment works (MWWTWs) are of concern for their endocrine-disrupting activities. In this study, domestic wastewater treated by a full-scale membrane bioreactor (MBR) at an MWWTW in the Western Cape Province, South Africa, was used directly as the influent to a reverse osmosis (RO) pilot plant for the removal of selected natural steroid hormones 17β-estradiol (E₂) and testosterone (T) as a potential indirect water recycling application. Estrogenicity and androgenicity were assessed using the enzyme-linked immunosorbent assays (ELISA) and the recombinant yeast estrogen receptor binding assays (YES). The influent pH and flux did not influence the rejection of E₂ and T, which was most likely due to adsorption, size exclusion, and diffusion simultaneously. RO and nanofiltration (NF) exhibited excellent removal rates (>95%) for E₂ and T. All the E₂ effluent samples with MBR/ultrafiltration (UF), MBR/NF, and MBR/RO were lower than the US EPA and WHO trigger value of 0.7 ng/L, as well as the predicted no-effect concentration (PNEC) values for fish (1 ng E₂/L).

Systematic Review of Toxicity Removal by Advanced Wastewater Treatment Technologies via Ozonation and Activated Carbon

Upgrading wastewater treatment plants (WWTPs) with advanced technologies is one key strategy to reduce micropollutant emissions. Given the complex chemical composition of wastewater, toxicity removal is an integral parameter to assess the performance of WWTPs. Thus, the goal of this systematic review is to evaluate how effectively ozonation and activated carbon remove in vitro and in vivo toxicity. Out of 2464 publications, we extracted 46 relevant studies conducted at 22 pilot or full-scale WWTPs. We performed a quantitative and qualitative evaluation of in vitro (100 assays) and in vivo data (20 species), respectively. Data is more abundant on ozonation (573 data points) than on an activated carbon treatment (162 data points), and certain in vitro end points (especially estrogenicity) and in vivo models (e.g., daphnids) dominate. The literature shows that while a conventional treatment effectively reduces toxicity, residual effects in the effluents may represent a risk to the receiving ecosystem on the basis of effect-based trigger values. In general, an upgrade to ozonation or activated carbon treatment will significantly increase toxicity removal with similar performance. Nevertheless, ozonation generates toxic transformation products that can be removed by a post-treatment. By assessing the growing body of effect-based studies, we identify sensitive and underrepresented end points and species and provide guidance for future research.