Diagnosis of complex mixture toxicity in sediments: Application of toxicity identification evaluation (TIE) and effect-directed analysis (EDA)

"PAW" a smart analytical process assessing lipophilicity of solutes in mixtures

BACKGROUND

The analysis of mixtures of contaminants remains a challenging task in many fields, including water quality and waste management. For example, the degradation of industrial waste such as plastics, leads to complex mixtures with hundreds of organic contaminants and often non-referenced analytes. In such cases, non-targeted or effects-based analyses provide complementary information to classical targeted-analyses, regarding contaminants nature or properties (molecular mass, lability, toxicity). In this study, a novel analytical method is proposed to characterise mixtures of unknown organic contaminants, with a focus on the lipophilicity of solutes.

RESULTS

The proposed process, named "PAW" (Partition of Aqueous Waste), aims at the quantification of octanol-water partition coefficients (POW) of mixed organic analytes. The process is based on sequential liquid-liquid partition equilibria. The output result is a lipophilicity histogram of the solutes, screened according to the chosen detection method. The process quantifies the distribution of analytes as a function of their octanol-water partition coefficients, without requiring any identification or prior knowledge. The PAW process is applicable with various detectors (UV-Visible, total carbon, liquid scintillation, etc.) allowing to focus on specific families of contaminants (e.g. organic solutes, colloids, 14C-bearing, etc.). Experimental proofs of concept are proposed, illustrating process implementation and possible fields of application. The first example deals with purity analysis of synthetic radiolabeled compounds. The second example aims the monitoring of cellulose degradation and quantification of the lipophilicity of degradation products.

SIGNIFICANCE

The PAW analytical process seems especially useful for characterisation of mixtures containing both hydrophilic and lipophilic compounds, e.g. neutral and ionizable organic contaminants, hardly characterisable simultaneously by chromatographic methods. It could be complementary to more detailed targeted or screening analysis of samples and effluents. For example it may help assessing the composition and environmental fate of mixtures of unknown analytes, thus facilitating waste management or mitigation strategies.

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

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

Deep Learning Bridged Bioactivity, Structure, and GC-HRMS-Readable Evidence to Decipher Nontarget Toxicants in Sediments

Identifying causative toxicants in mixtures is critical, but this task is challenging when mixtures contain multiple chemical classes. Effect-based methods are used to complement chemical analyses to identify toxicants, yet conventional bioassays typically rely on an apical and/or single endpoint, providing limited diagnostic potential to guide chemical prioritization. We proposed an event-driven taxonomy framework for mixture risk assessment that relied on high-throughput screening bioassays and toxicant identification integrated by deep learning. In this work, the framework was evaluated using chemical mixtures in sediments eliciting aryl-hydrocarbon receptor activation and oxidative stress response. Mixture prediction using target analysis explained <10% of observed sediment bioactivity. To identify additional contaminants, two deep learning models were developed to predict fingerprints of a pool of bioactive substances (event driver fingerprint, EDFP) and convert these candidates to MS-readable information (event driver ion, EDION) for nontarget analysis. Two libraries with 121 and 118 fingerprints were established, and 247 bioactive compounds were identified at confidence level 2 or 3 in sediment extract using GC-qToF-MS. Among them, 12 toxicants were analytically confirmed using reference standards. Collectively, we present a "bioactivity-signature-toxicant" strategy to deconvolute mixtures and to connect patchy data sets and guide nontarget analysis for diverse chemicals that elicit the same bioactivity.

Rapid screening of acetylcholinesterase active contaminants in water: A solid phase microextraction-based ligand fishing approach

Effect-directed analysis (EDA) has been increasingly used for screening toxic contaminants in the environment, but conventional EDA procedures are often time-consuming and labor-extensive. This challenges the use of EDA for toxicant identification in the scenarios when quick answers are demanded. Herein, a solid phase microextraction ligand fishing (SPME-LF) strategy has been proposed as a rapid EDA approach for identifying acetylcholinesterase (AChE) active compounds in water. The feasibility of ligand fishing techniques for screening AChE active chemicals from environmental mixtures was first verified by a membrane separation method. Then, SPME fibers were prepared through self-assembly of boronic acid groups with AChE via co-bonding and applied for SPME-LF. As AChE coated SPME fibers selectively enriched AChE-active compounds from water, comparing sorbing compounds by the SPME fibers with and without AChE coating can quickly distinguish AChE toxicants in mixtures. Compared with conventional EDA, SPME-LF does not require repeating sample separations and bioassays, endowing SPME-LF with the merits of low-cost, labor-saving, and user-friendly. It is believed that cost-efficient and easy-to-use SPME-LF strategy can potentially be a rapid EDA method for screening receptor-specific toxicants in aquatic environment, especially applicable in time-sensitive screening.

Toxicity and chemical characterization of shale gas wastewater discharged to the receiving water: Evidence from toxicity identification evaluation

Flowback and produced water (FPW) generated from shale gas extraction is a complex mixture consisting of injected drilling fluid, deep formation water, and byproducts of downhole reactions. Limited knowledge is available regarding the impact of discharged FPW on surface water in China. With the development of shale gas exploitation, this emphasizes an urgent need for comprehensive assessments and stringent regulations to ensure the safe disposal of shale gas extraction-related wastewater. Herein, we explored potential impacts of treated shale gas wastewater discharged into a local river in southwest China through toxicity identification evaluation (TIE). Results revealed that organics and particulates significantly contributed to the overall toxicity of the treated FPW wastewater. Through target and suspect chemical analyses, various categories of organic contaminants were detected, including alkanes, aromatic hydrocarbons, biocides, phenols, and phthalates. Furthermore, non-target analysis uncovered the presence of surfactant-related contaminants in tissues of exposed organisms, but their contribution to the observed toxicity was unclear due to the lack of effect data for these compounds. Higher toxicity was found at the discharge point compared with upstream sites; however, the toxicity was rapidly mitigated due to dilution in the receiving river, posing little impact on downstream areas. Our study highlighted the importance of monitoring toxicity and water quality of FPW effluent even though dilution could be a viable approach when the water volume in the discharge was small.

Combining Passive Sampling and Dosing to Unravel the Contribution of Hydrophobic Organic Contaminants to Sediment Ecotoxicity

Contaminated sediments are ubiquitous repositories of pollutants and cause substantial environmental risks. Results of sediment bioassays remain difficult to interpret, however, as observed effects may be caused by a variety of (un)known stressors. This study aimed therefore to isolate the effects of hydrophobic organic contaminants from other (non)chemical stressors present in contaminated sediments, by employing a newly developed passive sampling-passive dosing (PSPD) test. The results showed that equilibrium partitioning between pesticides or polyaromatic hydrocarbons (PAHs) in contaminated sediments and a silicone rubber (SR) passive sampler was achieved after 1-3 days. Chlorpyrifos concentrations in pore water of spiked sediment matched very well with concentrations released from the SR into an aqueous test medium, showing that SR can serve as a passive dosing device. Subjecting the 96 h PSPD laboratory bioassay with nonbiting midge (Chironomus riparius) larvae to field-collected sediments showed that at two locations, concentrations of the hydrophobic organic contaminant mixtures were high enough to affect the test organisms. In conclusion, the developed PSPD test was able to isolate the effects of hydrophobic organic contaminants and provides a promising simplified building block for a suite of PSPD tests that after further validation could be used to unravel the contribution of hydrophobic organic chemicals to sediment ecotoxicity.

High-Throughput Effect-Directed Monitoring Platform for Specific Toxicity Quantification of Unknown Waters: Lead-Caused Cell Damage as a Model Using a DNA Hybrid Chain-Reaction-Induced AuNPs@aptamer Self-Assembly Assay

A high-throughput cell-based monitoring platform was fabricated to rapidly measure the specific toxicity of unknown waters, based on AuNPs@aptamer fluorescence bioassays. The aptamer is employed in the platform for capturing the toxicity indicator, wherein hybrid chain-reaction (HCR)-induced DNA functional gold nanoparticle (AuNPs) self-assembly was carried out for signal amplification, which is essential for sensitively measuring the sub-lethal effects caused by target compounds. Moreover, the excellent stability given by the synthesized DNA nanostructure provides mild conditions for the aptamer thus used to bind the analyte. Herein, ATP was treated as a toxicity indicator and verified using lead-caused cell damage as a model. Under optimized conditions, excellent performance for water sample measurement was observed, yielding satisfactory accuracy (recovery rate: 82.69-114.20%; CV, 2.57%-4.65%) and sensitivity (LOD, 0.26 µM) without sample pretreatment other than filtration, indicating the method's simplicity, high efficiency, and reliability. Most importantly, this bioassay could be used as a universal platform to encourage its application in the rapid quantification of specific toxicity in varied sources of samples, ranging from drinking water to highly contaminated wastewater.

Toxicity identification evaluation for hydraulic fracturing flowback and produced water during shale gas exploitation in China: Evidence from tissue residues and gene expression

Hydraulic fracturing flowback and produced water (HF-FPW) from shale gas extraction processes is a highly complex medium with potential threats to the environment. Current research on ecological risks of FPW in China is limited, and the link between major components of FPW and their toxicological effects on freshwater organisms is largely unknown. By integrating chemical and biological analyses, toxicity identification evaluation (TIE) was used to reveal causality between toxicity and contaminants, potentially disentangling the complex toxicological nature of FPW. Here, FPW from different shale gas wells, treated FPW effluent, and a leachate from HF sludge were collected from southwest China, and TIE was applied to obtain a comprehensive toxicity evaluation in freshwater organisms. Our results showed that FPW from the same geographic zone could cause significantly different toxicity. Salinity, solid phase particulates, and organic contaminants were identified as the main contributors to the toxicity of FPW. In addition to water chemistry, internal alkanes, PAHs, and HF additives (e.g., biocides and surfactants) were quantified in exposed embryonic fish by target and non-target tissue analyses. The treated FPW failed to mitigate the toxicity associated with organic contaminants. Transcriptomic results illustrated that organic compounds induced toxicity pathways in FPW-exposed embryonic zebrafish. Similar zebrafish gene ontologies were affected between treated and untreated FPW, again confirming that sewage treatment did not effectively remove organic chemicals from FPW. Thus, zebrafish transcriptome analyses revealed organic toxicant-induced adverse outcome pathways and served as evidence for TIE confirmation in complex mixtures under data-poor scenarios.

Organotin mixtures reveal interactions that modulate adipogenic differentiation in 3T3-L1 preadipocytes

Organotin chemicals (butyltins and phenyltins) are the most widely used organometallic chemicals worldwide and are used in industrial applications, such as biocides and anti-fouling paints. Tributyltin (TBT) and more recently, dibutyltin (DBT) and triphenyltin (TPT) have been reported to stimulate adipogenic differentiation. Although these chemicals co-exist in the environment, their effect in combination remains unknown. We first investigated the adipogenic effect of eight organotin chemicals (monobutyltin (MBT), DBT, TBT, tetrabutyltin (TeBT), monophenyltin (MPT), diphenyltin (DPT), TPT, and tin chloride (SnCl4)) in the 3T3-L1 preadipocyte cell line in single exposures at two doses (10 and 50 ng/ml). Only three out of the eight organotins induced adipogenic differentiation with TBT eliciting the strongest adipogenic differentiation (in a dose-dependent manner) followed by TPT and DBT, as demonstrated by lipid accumulation and gene expression. We then hypothesized that, in combination (TBT, DBT, and TPT), adipogenic effects will be exacerbated compared to single exposures. However, at the higher dose (50 ng/ml), TBT-induced differentiation was reduced by TPT and DBT when in dual or triple combination. We tested whether TPT or DBT would interfere with adipogenic differentiation stimulated by a peroxisome proliferator-activated receptor (PPARγ) agonist (rosiglitazone) or a glucocorticoid receptor agonist (dexamethasone). Both DBT50 and TPT50 reduced rosiglitazone-, but not dexamethasone-stimulated adipogenic differentiation. In conclusion, DBT and TPT interfere with TBT's adipogenic differentiation possibly via PPARγ signaling. These findings highlight the antagonistic effects among organotins and the need to understand the effects and mechanism of action of complex organotin mixtures on adipogenic outcomes.

An integrated screening strategy for novel AhR agonist candidate identification and toxicity confirmation in sediments

Organic contaminants showing aryl hydrocarbon receptor (AhR) agonist activity are commonly detected in areas disturbed by intense human activities and they can initiate a variety of biochemical, physiological, and toxicological effects. A new integrated screening strategy for AhR agonist candidate identification and toxicity confirmation was developed to characterize the AhR-active pollutants in sediments of the contaminated Daqing River basin (DRB) in North China. The specific objectives were to (i) determine the concentrations of known AhR agonists, (ii) identify the novel AhR agonist candidates from nontarget screening (NTS) with structure alerts, computational toxicology (CompTox) Dashboard bioassays, and in silico predictions, and (iii) evaluate contributions of AhR agonists to the overall potencies and characterize the distribution and source of these pollutants. Significant AhR-mediated potencies were observed in all sediment extracts by in vitro bioassays. Concentrations of polar target chemicals in sediment extracts were much lower than nonpolar target chemicals. A total of 19 known AhR agonists explained 11.3 % to 49.1 % of bioassay-derived AhR-mediated potencies and polychlorinated biphenyls (PCB) 126 and PCB169 were found to contribute significantly to the total effects. 21 compounds screened from NTS by AhR-related structure alerts and further confirmed toxicity by high-throughput bioassays and in silico predictions were selected as AhR agonist candidates. Most of them were substituted PAHs, biphenyls, quinones, substituted phenols and heterocyclic compounds, and they primarily originated from nearby manufacturing industries. Of these compounds, 1-methy-pyrene exhibited significant AhR-mediated potency. Follow up studies should focus on toxicological mechanism, source, and fate of these novel AhR agonists in water environment.

Combined toxicities of cadmium and five agrochemicals to the larval zebrafish (Danio rerio)

Different pollutants usually co-exist in the natural environment, and the ecological and health risk assessment of agrochemicals needs to be carried out based on the combined toxicological effects of pollutants. To examine the combined toxicity to aquatic organisms, the effects of cadmium (Cd) and five pesticides (acetamiprid, carbendazim, azoxystrobin, chlorpyrifos, and bifenthrin) mixture on zebrafish (Danio rerio) larvae were assessed. The data from the 96-h toxicity test indicated that bifenthrin possessed the highest toxicity to D. rerio with the LC₅₀ value of 0.15 mg L^-1, followed by chlorpyrifos (0.36 mg L^-1) and azoxystrobin (0.63 mg L^-1). Cd (6.84 mg L^-1) and carbendazim (8.53 mg L^-1) induced the intermediate toxic responses, while acetamiprid (58.39 mg L^-1) presented the lowest toxicity to the organisms. Pesticide mixtures containing chlorpyrifos and bifenthrin or acetamiprid and carbendazim showed synergistic impacts on the zebrafish. Besides, two binary combinations of Cd-acetamiprid and Cd-chlorpyrifos also displayed a synergistic effect on D. rerio. Our results offered a better idea of the mixed ecological risk assessment of Cd and different agricultural chemicals to aquatic organisms. Our findings better interpreted how the interaction between Cd and various agrochemicals changed their toxicity to aquatic vertebrates and provided valuable insights into critical impacts on the ecological hazard of their combinations.

Effect-directed analysis for revealing aryl hydrocarbon receptor agonists in sediment samples from an electronic waste recycling town in China

Exposure to electronic and electrical waste (e-waste) has been related to a few adverse health effects. In this study, sediment samples from an e-waste recycling town in China were collected, and aryl hydrocarbon receptor (AhR) agonists in the samples were identified using an effect-directed analysis (EDA) strategy. The CBG2.8D cell line reporter gene bioassay was used as a toxicity test, while suspect screening against chemical databases was performed for potential AhR agonist identification where both gas chromatography- and liquid chromatography-high resolution mass spectrometry analyses were run. When the original sample extract showed high AhR-mediated activity, sample fractionation was performed, and fractions exhibiting high bioactivity were chemically analyzed again to reveal the corresponding AhR agonists. In total, 23 AhR agonists were identified, including 14 commonly known ones and 9 new ones. Benzo [k]fluoranthene and 6-nitrochrysene were the dominant AhR agonists, covering 16-71% and 2.7-12%, respectively, of the AhR activation effects measured in the parent extracts. The newly identified AhR-active chemicals combined explained 0.13-0.20% of the parent extracts' effects, with 7,12-dimethylbenz [a]anthracene and 8,9,11-trimethylbenz [a]anthracene being the major contributors. A diagnostic isomer ratio analysis of polycyclic aromatic hydrocarbons suggested that the major source of AhR agonists identified in these e-waste related sediment samples were probably petroleum product combustion and biomass combustion. In the future, for a more comprehensive AhR agonist investigation, in-house chemical synthesis and purification, and, when necessary, a secondary sample fractionation, would be beneficial.

Effect-directed analysis of estrogenic chemicals in sediments from an electronic-waste recycling area

Electronic waste (e-waste) pollution is of great concern due to the release of hazardous chemicals during the improper e-waste disposal. Many chemicals leached from e-waste were reported to pose estrogenic effects. To date, little is known regarding the occurrence and biological effects of estrogenic chemicals in sediments near an e-waste area. In this study, an effect-directed analysis (EDA) is applied to determine the estrogenic chemicals in sediments of four sites collected from a typical e-waste recycling city in China. Following screening with the ER-CALUX assay, the extract of sample with the most potent effect was subjected in fractionation using reverse phase liquid chromatography. Based on a target analysis for the active fractions, four compounds, including estrone, 17β-estradiol, 17α-ethinylestradiol and bisphenol A, were identified, and these contributed to 17% of the total toxic effects in the sample. A further nontarget analysis screened four candidates, namely diethylstilbestrol (DES), hexestrol (HES), nandrolone and durabolin, and the total contribution was found to be 48% from the active sample. Specifically, DES and HES were only detected in the active sample and were found to be the primary drivers of estrogenic effects. An examination of the identified chemicals in the four sites indicated that these estrogenic chemicals may originate from e-waste recycling, livestock excretion and domestic waste. These findings uncovered the estrogenic pollutants in sediments from an e-waste area. Considering single endpoint in biological assay is not abundant to screen chemicals with different toxic effects, further EDA studies with multiple endpoints are required to better understand the occurrence of representative or unknown chemicals in e-waste-polluted areas.

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.

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

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

Overlooked environmental risks deriving from aqueous transformation of bisphenol alternatives: Integration of chemical and toxicological insights

Owing to the widespread prevalence and ecotoxicity of bisphenol alternatives such as bisphenol S, bisphenol F, and bisphenol AF, the past decade has witnessed the publication of a remarkable number of studies related to their transformation and remediation in natural waters. However, the reactivity, removal efficiency, transformation products (TPs), and mechanisms of such emerging pollutants by different treatment processes have not been well elucidated. Particularly, the transformation-driven environmental risks have been mostly overlooked. Therefore, we present a review to address these issues from chemical and toxicological viewpoints. Four degradation systems can be largely classified as catalytic persulfate (PS) oxidation, non-catalytic oxidation, photolysis and photocatalysis, and biodegradation. It was found that bisphenol alternatives possess distinct reactivities with different oxidizing species, with the highest performance for hydroxyl radicals. All systems exhibit superior elimination efficiency for these compounds. The inadequate mineralization suggests the formation of recalcitrant TPs, from which the overall reaction pathways are proposed. The combined experimental and in silico analysis indicates that many TPs have developmental toxicity, endocrine-disrupting effects, and genotoxicity. Notably, catalytic PS systems and non-catalytic oxidation result in the formation of coupling products as well as halogenated TPs with higher acute and chronic toxicity and lower biodegradability than the parent compounds. In contrast, photolysis and photocatalysis generate hydroxylated and bond-cleavage TPs with less toxicity. Overall, this review highlights the secondary environmental risks from the transformation of bisphenol alternatives by conventional and emerging treatment processes. Finally, future perspectives are recommended to address the knowledge gaps of these contaminants in aquatic ecosystems.

Acute toxicity assay using mysid as an alternative test organism in the assessment of the aqueous fraction of sediment

The evaluation of sediment quality through biological testing of the aqueous fraction can be applied in dredging situations and is associated with a small number of confounding factors. The use of test organisms that are relatively resistant to contaminants is recommended when working with complex mixtures such as sediments. In this study, the sensitivity of the mysid Mysidopsis juniae to ammonia (NH₃) and metals was investigated in acute toxicity laboratory tests and the results were compared to those obtained in the traditional test with sea urchin embryos and larvae. The ability of the toxicity identification and evaluation (TIE) technique, with the use of EDTA and sodium thiosulfate, to indicate the factors responsible for adverse effects was determined. The results indicate that mysids are almost 5 times more resistant than the sea urchin to ammonia (NH₃), more sensitive to Cd²⁺ and Ni²⁺ and more resistant to Zn²⁺ and Pb²⁺. With the TIE technique and with the use of EDTA as a complexing agent, a greater resolution was observed in the diagnosis of the presence of the metals Cd²⁺ and Ni²⁺, which could be applied to the aqueous fraction of the sediment.

Toxicity Identification Evaluation of Sediments from the Xihe River

In the present study, chinonomus riparius larvae were selected as a model organism, and 11 sediment samples from the Xihe River in Shenyang underwent toxicity identification evaluation (TIE) to identify sediment toxic pollutants. Heavy metals and organic pollutants were the main toxic pollutants through toxicity screening and characterization. The results of toxicity identification showed that the pollution level from Cd was most serious and that phenol and P-methyl phenol were the major organic pollutants. Moreover, a spiking test of Cd was conducted, which indicated that Cd was the main toxic pollutant of sediments at sites 4, 6, 7, 8, and 10. We confirm that TIE is the most effective method to determine the relationship between toxic effects and toxic pollutants. Environ Toxicol Chem 2021;40:3103-3110. © 2021 SETAC.

Toxicity assessment of urban marine sediments from Western Norway using a battery of stress-activated receptors and cell-based bioassays from fish

A luciferase reporter gene-based bioassay battery consisting of stress-activated receptors from fish, complemented with traditional fish cell-based bioassays, were used to assess the toxicity of marine sediment samples from the Byfjorden area around the city of Bergen (Norway). The reporter assays covered a wide range of cellular signalling and metabolic pathways, representing different molecular initiating events in the adverse outcome pathway framework. Cytotoxicity, generation of reactive oxygen-species, and induction of 7-ethoxyresorufin-O-deethylase activity were analysed using fish liver and gill cell lines. Chemical analyses of the sediment extracts revealed complex contamination profiles, especially at the innermost stations, which contained a wide array of persistent organic pollutants, polycyclic aromatic hydrocarbons, and metals. Sediment extracts from these sites were more potent in activating the stress-activated receptors than the other extracts, reflecting their toxicant profiles. Importantly, receptor- and cell-based bioassays complemented the chemical analyses and provided important data for future environmental risk assessments of urban marine sediments.

Protein-affinity guided identification of chlorinated paraffin components as ubiquitous chemicals

Chlorinated paraffins (CPs) have been extensively examined to identify their components. Short-chain CPs with a carbon number of 10-13 have been strictly restricted or banned due to their addition to the list of Persistent Organic Pollutants in the world. However, more constituents with potential toxicities in these complicated mixtures are still unclear. In the present study, a purification method based on the protein affinity of thyroid hormone-related proteins (transthyretin and thyroid receptor) was established. The protein-based affinity extraction coupled with high-throughput scanning successfully discover a new group of chlorinated compounds (CP(O₂)) in commercial CP mixtures. The CP(O₂)s were purified from the commercial mixtures and identified to be chlorinated fatty acid methyl esters (CFAMEs) with a carbon chain length of 17-19 and 3-11 chlorines by a combination of liquid-liquid extraction, hydrolysis, Fourier transform infrared spectrometry and Orbitrap mass spectrometry. The newly identified CFAMEs were found to be ubiquitous in the environmental matrices, and concentration ratios of ∑CFAMEs/∑CPs ranged from 0.01 to 35 in air, soil and food samples. CFAMEs were also detected in blood samples of general populations, and accumulated in humans through dietary uptake. CFAMEs can compete with T4 for binding TTR with higher potencies than CPs, possibly leading to disruptions of thyroid hormone homeostasis.

Toward Sustainable Environmental Quality: Priority Research Questions for Asia

Environmental and human health challenges are pronounced in Asia, an exceptionally diverse and complex region where influences of global megatrends are extensive and numerous stresses to environmental quality exist. Identifying priorities necessary to engage grand challenges can be facilitated through horizon scanning exercises, and to this end we identified and examined 23 priority research questions needed to advance toward more sustainable environmental quality in Asia, as part of the Global Horizon Scanning Project. Advances in environmental toxicology, environmental chemistry, biological monitoring, and risk-assessment methodologies are necessary to address the adverse impacts of environmental stressors on ecosystem services and biodiversity, with Asia being home to numerous biodiversity hotspots. Intersections of the food-energy-water nexus are profound in Asia; innovative and aggressive technologies are necessary to provide clean water, ensure food safety, and stimulate energy efficiency, while improving ecological integrity and addressing legacy and emerging threats to public health and the environment, particularly with increased aquaculture production. Asia is the largest chemical-producing continent globally. Accordingly, sustainable and green chemistry and engineering present decided opportunities to stimulate innovation and realize a number of the United Nations Sustainable Development Goals. Engaging the priority research questions identified herein will require transdisciplinary coordination through existing and nontraditional partnerships within and among countries and sectors. Answering these questions will not be easy but is necessary to achieve more sustainable environmental quality in Asia. Environ Toxicol Chem 2020;39:1485-1505. © 2020 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Evaluation of joint toxicity of heavy metals and herbicide mixtures in soils to earthworms (Eisenia fetida)

It is widely acknowledged that a simplified and robust approach to evaluating thecombined effects of chemical mixtures is critical for ecological risk assessment (ERA) of contaminated soil. The earthworm (Eisenia fetida) was used as a model to study the combined effects of polymetallic contamination and the herbicide siduron in field soil using a microcosm experiment. The responses of multiple biomarkers, including the activities of catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR) and acetylcholine esterase (AChE), the concentrations of glycogen, soluble protein (SP), malonaldehyde (MDA), and metallothionein (MT), and the neutral red uptake test (NRU), were investigated. Multivariate analysis, Principal Component Analysis (PCA) and Spearman's Rank Correlations analysis (BVSTEP) revealed that the activities of AChE and CAT and the NRU content were the prognostic biomarkers capturing the minimum data set of all the variables. Internal Cd (tissue Cd) in earthworms was closely related to the health status of worms under combined contamination of heavy metals and siduron. The integrated effect (E_mix) calculated based on the activities of AChE and CAT and NRU content using the stress index method had significantly linear regression with internal Cd (p<0.01). E_mix(10), E_mix(20), and E_mix(50) were then calculated, at 1.27, 1.63 and 2.71 mg/kg dry weight, respectively. It could be concluded that a bioassay-based approach incorporating multivariate analysis and internal dose was pragmatic and applicable to evaluating combined effects of chemical mixtures in soils under the guidance of the top-down evaluation concept of combined toxicity.

Identification of acetylcholinesterase inhibitors in water by combining two-dimensional thin-layer chromatography and high-resolution mass spectrometry

Effect-directed analysis (EDA) is increasingly used in environmental monitoring to detect and identify key toxicants. High-performance thin-layer chromatography (HPTLC) has proven to be a very suitable fractionation technique for this purpose. However, HPTLC is limited in its separation efficiency. Thus, separated fractions could still contain many different components and identification of the effective substances remains difficult. Therefore, in this study a workflow for selective EDA with two-dimensional HPTLC in combination with high-performance liquid chromatography-high-resolution mass spectrometry (HPLC-HRMS) was developed. The aim of the workflow was the stepwise reduction of the sample complexity in order to reduce the number of signals that could be responsible for the measured effects. As a consequence, the identification of effective substances should be facilitated. The acetylcholinesterase inhibition assay (AChE assay) for the detection of potential neurotoxic compounds was applied for biotesting. The transfer of effective zones from the first to the second dimension and also to the mass spectrometric measurement was enabled by extraction. A proof of concept was performed by spiking six acetylcholinesterase inhibiting substances into three different water matrices that were investigated with the developed workflow. The successful prioritization of all spiked compounds confirmed the efficiency of the workflow, regardless of the sample matrix. Biotesting of different water samples resulted in numerous potentially neurotoxic effects, which overlapped strongly in the first separation dimension. The higher peak capacity reached by two-dimensional HPTLC, on the other hand, resulted in discrete effective zones and enabled the identification of several compounds. For the substances lumichrome, a derivate of riboflavin and paraxanthine as well as for linear alkylbenzene sulfonates that were applied as anionic surfactants in detergents, the inhibiting effect to the AChE could be confirmed.

Identifying bioaccessible suspect toxicants in sediment using adverse outcome pathway directed analysis

Chemical mixtures are a common occurrence in contaminated sediment and determining causal relationship between sediment contamination and adverse outcomes is challenging. The bioavailability and choice of bioassay endpoints played important roles in elucidating causality. As such, bioaccessibility-based XAD extraction and adverse outcome pathway (AOP) guided bioassays were incorporated into an effect-directed analysis to more effectively determine sediment causality. XAD extracts of sediments from urban waterways in Guangzhou, China were examined using cell viability bioassays with four human tumor cells from lung, liver, breast, and bone marrow. Pronounced effects to SH-SY5Y cells were noted, thus neurotoxicity was subsequently focused in the AOP-guided bioassays. Intracellular calcium influx, mitochondrial membrane potential inhibition, reactive oxygen species generation, and cell viability were utilized as evidence for neurotoxicity AOP-guided analysis. Suspect toxicants were identified in active fractions using GC-MS. Toxicity confirmation was performed by evaluating toxicity contributions of the candidates to the pathway. Cypermethrin, bisphenol A, galaxolide, tonalide, and versalide were found as the major stressors across key events of the studied pathway. Moreover, good correlations among key events validated the feasibility of method to predict in vivo response, suggesting that considering bioavailability and AOP improved environmental relevance for toxicant identification in a complex mixture.

Examining the correlation between quantifiable SVOCs and organic carbon content or particulate size in benthic sediments as a function of ocean stratum

The raw analytical concentration values of semi-volatile organic compounds (SVOCs) in ocean sediments do not necessarily reflect the bioavailable fractions of SVOCs in the sediments due to factors such as the total organic carbon content of sediments (TOC) and the percentage of fine particles in sediments (% fines) as they are believed to affect the extraction efficiency of SVOCs from sediments. Corrective actions are therefore taken to minimize their influence on measurements. In doing so, a broad and uniform correlation is assumed to exist between the 'native' levels of SVOCs and TOC or % fines across ocean strata. However, the validity of this blanket assumption is not yet verified. In this study, we examined the strength of the assumption using DDTs, PAHs and PCBs levels in sediments from Santa Monica Bay (SMB), California, USA. (The distribution patterns of these SVOCs in SMB are known and reproducible for quality assurance.) As our results show, a uniform correlation between SVOC levels and TOC or % fines across strata is mostly absent. For example, PAH and PCB levels show negative correlation with TOC or % fines, and only in canyon sediments, DDT levels correlate positively with both TOC and % fines across at least three strata. Furthermore, the distribution of PAH molecules appears to be controlled by molecular size with smaller PAHs being found almost exclusively in the canyons. Our finding here, being the first of its kind, suggests that more work is needed to clarify the reporting of SVOC levels in ocean sediments.

Development of a separation framework for effects-based targeted and non-targeted toxicological screening of water and wastewater

An environmental water sample fractionation framework was developed based on effects-directed analysis (EDA) to detect known and unknown compounds of concern in different waters. Secondary effluent from a wastewater treatment plant was used to demonstrate the effectiveness of the developed framework for characterizing estrogenic compounds in the effluent. The effluent was spiked with known estrogenic compounds to validate the framework in a targeted approach and an unspiked sample was also investigated in a non-targeted approach. The framework separated compounds based on polarity and adsorption using liquid-liquid extraction followed by solid phase extraction. The targeted and non-targeted effluents generated six fractions each, which were assessed for estrogenic activity using an in vitro bioassay (yeast estrogen screen - YES). Three out of the six fractions in each case, along with the raw effluent, showed estrogen equivalent concentrations (EEQs) ranging between 1.0 and 3.0 μg/L. Directed by the assay results, these estrogenic fractions were further analyzed using liquid- and gas-chromatography coupled with mass spectrometry for compound identification. The developed separation framework coupled with a bioassay aided in identification of both known and unknown compounds producing estrogenic effects in the water sample. The approach of fractionation followed by concentration helped isolate and elevate contaminant levels without necessarily concentrating potential matrix effects that could cause interfering cytotoxicity and inhibition in the bioassay. The targeted analysis showed consistency between predicted and observed results, while the non-targeted analysis revealed the presence of three estrogenic compounds in the unspiked effluent: di-isobutyl phthalate, diethyl phthalate and benzophenone, that were confirmed with standards. The study mainly aimed at development and validation of a simple yet effective EDA framework with low cost techniques for water and wastewater toxicity screening and evaluation, and the results suggested that the developed framework could be used as a screening tool for isolating and identifying unknown compounds in a complex water sample.

Smarter Sediment Screening: Effect-Based Quality Assessment, Chemical Profiling, and Risk Identification

Sediments play an essential role in the functioning of aquatic ecosystems but simultaneously retain harmful compounds. However, sediment quality assessment methods that consider the risks caused by the combined action of all sediment-associated contaminants to benthic biota are still underrepresented in water quality assessment strategies. Significant advancements have been made in the application of effect-based methods, but methodological improvements can still advance sediment risk assessment. The present study aimed to explore such improvements by integrating effect-monitoring and chemical profiling of sediment contamination. To this end, 28 day life cycle bioassays with Chironomus riparius using intact whole sediment cores from contaminated sites were performed in tandem with explorative chemical profiling of bioavailable concentrations of groups of legacy and emerging sediment contaminants to investigate ecotoxicological risks to benthic biota. All contaminated sediments caused effects on the resilient midge C. riparius, stressing that sediment contamination is ubiquitous and potentially harmful to aquatic ecosystems. However, bioassay responses were not in line with any of the calculated toxicity indices, suggesting that toxicity was caused by unmeasured compounds. Hence, this study underlines the relevance of effect-based sediment quality assessment and provides smarter ways to do so.

Using the HPTLC-bioluminescence bacteria assay for the determination of acute toxicities in marine sediments and its eligibility as a monitoring assessment tool

For an integrated ecological risk assessment of marine sediment contamination, the determination of target-compound concentrations by e.g. mass spectrometric methods is not sufficient to explain sediment toxicity. Due to the presence of a multitude of environmental contaminants in this complex matrix causing a mixed toxicity, the identification and assessment of main toxicants is a challenge. One approach in identifying main toxicants is the application of effect-directed analysis (EDA). In this study, an EDA approach was developed using high performance thin layer chromatography (HPTLC) coupled to bioluminescence bacteria detection with Aliivibrio fischeri for the determination of marine sediments acute toxicity. In a first attempt, the HPTLC separation was optimized with a fast, two-step gradient to separate main hydrophobic organic contaminant (HOC) classes found in marine sediments. An easy-to-use evaluation script for the resulting bioluminescence inhibition images was programed using R. The developed method was applied to sediment extracts of two different sample sets: (i) Fourteen marine sediment samples from the German Bight representing a wide range of contaminant loads and sediment properties and (ii) sediment samples from a core representing temporal trends of contamination. Results from the HPTLC-bioluminescence bacteria assay were compared to HOC concentrations determined by GC-MS/MS. A correlation of the determined inhibition Γ-values for the PAH inhibition zone to PAH concentrations showed a very good agreement (R² = 0.91). The results of this study were used to evaluate the suitability of the EDA approach to be used as an assessment tool for marine sediments.

To freeze, or not to freeze: the impact of subzero temperature on quantifying organic contaminants in ocean sediments

Assessing the extent of ocean bed contamination by anthropogenic organic chemicals requires collecting and preserving the native state of sediments. The latter is particularly important since most sediment analyses are performed away from the sites of samples collection. Preservation, however, is presumptuous since commonly used sediment handling practices such as freezing are structurally disruptive, the impacts of which are not well understood. In this study, the impact of freezing on quantifying the total organic carbon (TOC) contents and the extent of PAH, DDT and PCB contamination in 17 split-paired sediment samples was investigated. The samples were collected from the Santa Monica Bay, California (USA). One-half of each split-pair was frozen at -20 °C and the other half was refrigerated at 4 °C for up to 11 days. The results suggest that no significant differences exist between the frozen and the refrigerated datasets for PCBs (F1,28 = 4.01, p > 0.05), DDTs (n = 16, t-Stat < t-Critical, p > 0.05) or TOC (n = 16, t-Stat < t-Critical, p > 0.05). The results however show that less PAHs were detected in the frozen sediments (F1,24 = 8.18, p < 0.05) than in the refrigerated sediments; the larger PAHs were affected the most. Interestingly, while benzo[a]pyrene, a large PAH molecule, was affected by this apparent temperature-induced difference, its structural isomer, benzo[e]pyrene, was not. Even more interesting was the finding that while non-coplanar PCBs were affected similarly, the coplanar PCBs were not. Overall, sediment freezing within this study's timeframe appears to offer little contextual advantage over sediment refrigeration.

Integrating multiple lines of evidence of sediment quality in a tropical bay (Guanabara Bay, Brazil)

The present study evaluated the ecological risk of metal contamination in sediments of Guanabara Bay (GB) by combining multiple lines of evidence (LOEs). Chemical analysis and a set of whole-sediment toxicity assays were conducted with Tiburonella viscana, Kalliapseudes schubartii, Anomalocardia flexuosa, and Nitocra sp. Results were integrated by multivariate analysis and qualitative methods. Additionally, a whole-sediment Toxicity Identification Evaluation technique (TIE) was applied to identify the chemical groups responsible for the effects. Sediments from harbor and industrial areas exhibited toxicity linked to moderate to high concentrations of Zn, Pb, Cu and Cr. The TIE technique confirmed such effects, but it also indicates the contribution of ammonia and organic compounds to the observed toxicity. Our results demonstrate that the combination of multiple LOEs improves the effectiveness of environmental risk assessment of chemical stressors and management of coastal ecosystems in tropical regions.

Understanding the bioavailability of pyrethroids in the aquatic environment using chemical approaches

Pyrethroids are a class of commonly used insecticides and are ubiquitous in the aquatic environment in various regions. Aquatic toxicity of pyrethroids was often overestimated when using conventional bulk chemical concentrations because of their strong hydrophobicity. Over the last two decades, bioavailability has been recognized and applied to refine the assessment of ecotoxicological effects of pyrethroids. This review focuses on recent advances in the bioavailability of pyrethroids, specifically in the aquatic environment. We summarize the development of passive sampling and Tenax extraction methods for assessing the bioavailability of pyrethroids. Factors affecting the bioavailability of pyrethroids, including physicochemical properties of pyrethroids, and quality and quantity of organic matter, were overviewed. Various applications of bioavailability on the assessment of bioaccumulation and acute toxicity of pyrethroids were also discussed. The final section of this review highlights future directions of research, including development of standardized protocols for measurement of bioavailability, establishment of bioavailability-based toxicity benchmarks and water/sediment quality criteria, and incorporation of bioavailability into future risk assessment and management actions.

Multiple lines of evidence of sediment quality in an urban Marine Protected Area (Xixová-Japuí State Park, SP, Brazil)

Marine Protected Areas (MPAs) aim to protect habitats, biodiversity, and ecological processes as a conservation tool. These areas have been affected by contamination, which threats the biodiversity and ecological functioning. In this study, we evaluated the sediment quality of Xixová-Japuí State Park (XJSP), an MPA located in an urbanized Bay (Santos, Southeast Brazil) by integrating multiple lines-of-evidence. Six sites were selected within the XJSP and analyzed for sediment chemistry, toxicity, and benthic community descriptors using Sediment Quality Triad approach (SQT). Whole-sediment Toxicity Identification Evaluation (TIE) was employed as a complementary line of evidence to confirm the presence of domestic effluent discharges as a potential stressor. The SQT showed that sediments collected within XJSP are impacted by contaminants, exhibiting chronic toxicity and changes in benthic community. TIE results indicated that trace metals, organic contaminants, and ammonia contributed to the observed effects. Our results also indicate a lack of effectiveness of MPA in protecting the biodiversity due to the contamination sources, which requires efforts to pollution control in order to ensure the environmental conservation and management plan goals.

Identifying Organic Toxicants in Sediment Using Effect-Directed Analysis: A Combination of Bioaccessibility-Based Extraction and High-Throughput Midge Toxicity Testing

Toxicity identification evaluation (TIE) and effect-directed analysis (EDA) were integrated to diagnose toxicity drivers in a complex system, such as sediment. In TIE manipulation, XAD resin was utilized as an amending agent for characterizing organic toxicants, which also facilitate a large-volume bioaccessibility-based extraction for EDA purposes. Both raw sediments in TIE and extract fractions in EDA were tested with Chironomus dilutus for toxicity using whole-sediment testing and a high-throughput microplate assay. This allowed for a direct link between whole-sediment TIE and EDA, which strongly strengthened the characterization and identification of toxicants. Sediments amended with XAD resin, as part of the TIE, significantly reduced midge mortality compared with unamended sediments, suggesting that organics were one class of main toxicants. On the basis of bioaccessible concentrations in sediment measured by XAD extraction, a group of previously unidentified contaminants, synthetic polycyclic musks (versalide, tonalide, and galaxolide), were found to explain 32-73% of the observed toxicity in test sediments. Meanwhile, three pyrethroids contributed to an additional 17-35% of toxicity. Surprisingly, the toxicity contribution of musks and pyrethroids reached 58-442 and 56-1625%, respectively, based on total sediment concentrations measured by exhaustive extraction. This suggested that total sediment concentrations significantly overestimated toxicity and that bioavailability should be considered in toxicity identification. Identifying nontarget toxicants sheds a light on application of the integrated TIE and EDA method in defining causality in a complex environment.

Emerging investigator series: effect-based characterization of mixtures of environmental pollutants in diverse sediments

This study investigated whether cell-based bioassays were suitable to characterize profiles of mixture effects of hydrophobic pollutants in multiple sediments covering remote Arctic and tropical sites to highly populated sites in Europe and Australia. The total contamination was determined after total solvent extraction and the bioavailable contamination after silicone-based passive equilibrium sampling. In addition to cytotoxicity, we observed specific responses in cell-based reporter gene bioassays: activation of metabolic enzymes (arylhydrocarbon receptor: AhR, peroxisome proliferator activated receptor gamma: PPARγ) and adaptive stress responses (oxidative stress response: AREc32). No mixture effects were found for effects on the estrogen, androgen, progesterone and glucocorticoid receptors, or they were masked by cytotoxicity. The bioanalytical equivalent concentrations (BEQ) spanned several orders of magnitude for each bioassay. The bioavailable BEQs (passive equilibrium sampling) typically were 10-100 times and up to 420 times lower than the total BEQ (solvent extraction) for the AhR and AREc32 assays, indicating that the readily desorbing fraction of the bioactive chemicals was substantially lower than the fraction bound strongly to the sediment sorptive phases. Contrarily, the bioavailable BEQ in the PPARγ assay was within a factor of five of the total BEQ. We identified several hotspots of contamination in Europe and established background contamination levels in the Arctic and Australia.

Improving the accuracy of effect-directed analysis: the role of bioavailability

Aquatic ecosystems have been suffering from contamination by multiple stressors. Traditional chemical-based risk assessment usually fails to explain the toxicity contributions from contaminants that are not regularly monitored or that have an unknown identity. Diagnosing the causes of noted adverse outcomes in the environment is of great importance in ecological risk assessment and in this regard effect-directed analysis (EDA) has been designed to fulfill this purpose. The EDA approach is now increasingly used in aquatic risk assessment owing to its specialty in achieving effect-directed nontarget analysis; however, a lack of environmental relevance makes conventional EDA less favorable. In particular, ignoring the bioavailability in EDA may cause a biased and even erroneous identification of causative toxicants in a mixture. Taking bioavailability into consideration is therefore of great importance to improve the accuracy of EDA diagnosis. The present article reviews the current status and applications of EDA practices that incorporate bioavailability. The use of biological samples is the most obvious way to include bioavailability into EDA applications, but its development is limited due to the small sample size and lack of evidence for metabolizable compounds. Bioavailability/bioaccessibility-based extraction (bioaccessibility-directed and partitioning-based extraction) and passive-dosing techniques are recommended to be used to integrate bioavailability into EDA diagnosis in abiotic samples. Lastly, the future perspectives of expanding and standardizing the use of biological samples and bioavailability-based techniques in EDA are discussed.