An alternative approach to risk rank chemicals on the threat they pose to the aquatic environment

Cardiac arrhythmias in fish induced by natural and anthropogenic changes in environmental conditions

A regular heartbeat is essential for maintaining the homeostasis of the vertebrate body. However, environmental pollutants, oxygen deficiency and extreme temperatures can impair heart function in fish. In this Review, we provide an integrative view of the molecular origins of cardiac arrhythmias and their functional consequences, from the level of ion channels to cardiac electrical activity in living fish. First, we describe the current knowledge of the cardiac excitation-contraction coupling of fish, as the electrical activity of the heart and intracellular Ca2+ regulation act as a platform for cardiac arrhythmias. Then, we compile findings on cardiac arrhythmias in fish. Although fish can experience several types of cardiac arrhythmia under stressful conditions, the most typical arrhythmia in fish - both under heat stress and in the presence of toxic substances - is atrioventricular block, which is the inability of the action potential to progress from the atrium to the ventricle. Early and delayed afterdepolarizations are less common in fish hearts than in the hearts of endotherms, perhaps owing to the excitation-contraction coupling properties of the fish heart. In fish hearts, Ca2+-induced Ca2+ release from the sarcoplasmic reticulum plays a smaller role than Ca2+ influx through the sarcolemma. Environmental changes and ion channel toxins can induce arrhythmias in fish and weaken their tolerance to environmental stresses. Although different from endotherm hearts in many respects, fish hearts can serve as a translational model for studying human cardiac arrhythmias, especially for human neonates.

Which pollutants and sources should be prioritized for control in multi-pollutants complex contaminated areas?

Risk assessment and source identification of multi-pollutants are essential for accurate control of soil contamination. However, complexity in pollutant properties and diversity in source types raise challenges to the target. Therefore, this study constructed a hierarchical ecological risk quantification method combined with risk ranking, risk of single pollutant using potential affected fraction (PAF), and joint risk of multi-pollutants employing msPAF. Taking regional contamination in South China as a case, the risk ranking was determined, while single and joint effects showed msPAF reaching 79.4 %, with risk as heavy metals (HMs) > per- and polyfluoroalkyl substances (PFASs) > polycyclic aromatic hydrocarbons (PAHs). Meanwhile, an integrated source apportionment method was established from three layers by principal component analysis to classify source types, multiple linear regression of distance to identify key sources, and positive matrix factorization to track omitted sources. Consequently, key sources were captured, with 80.8 %-93.2 % contribution of farmland and electroplating to three main HMs, 52.2 %-69.4 % contribution of roads to three main PAHs, and 71.1 %-73.2 % contribution of electroplating to two main PFASs. Further, omitted sources were tracked with contribution of 31.2 %-84.1 % to eight pollutants. The established methods can identify control targets, including high-risk pollutants and their key sources.

Hazards of antiviral contamination in water: Dissemination, fate, risk and their impact on fish

Antiviral drugs are a cornerstone in the first line of antiviral therapy and their demand rises consistently with increments in viral infections and successive outbreaks. The drugs enter the waters due to improper disposal methods or via human excreta following their consumption; consequently, many of them are now classified as emerging pollutants. Hereby, we review the global dissemination of these medications throughout different water bodies and thoroughly investigate the associated risk they pose to the aquatic fauna, particularly our vertebrate relative fish, which has great economic and dietary importance and subsequently serves as a major doorway to the human exposome. Our risk assessment identifies eleven such drugs that presently pose high to moderate levels of risk to the fish. The antiviral drugs are likely to induce oxidative stress, alter the behaviour, affect different physiological processes and provoke various toxicological mechanisms. Many of the compounds exhibit elevated bioaccumulation potential, while, some have an increased tendency to leach through soil and contaminate the groundwater. Eight antiviral medications show a highly recalcitrant nature and would impact the aquatic life consistently in the long run and continue to influence the human exposome. Thereby, we call for urgent ecopharmacovigilance measures and modification of current water treatment methods.

Agrochemical inputs to managed oil palm plantations are a probable risk to ecosystems: Results from a screening level risk assessment

Palm oil is a high value crop widely grown in the tropics. The management of palm oil is characterised by widespread agrochemical use. Here we report the results of a screening level risk assessment conducted from the available literature on the environmental concentration of agrochemicals in surface waters and soils in palm oil growing areas. To date, only a small number of published studies have measured pollutant concentrations in and around palm oil plantations. To identify potential high-risk contaminants, a standard SSD based risk assessment, establishing risk quotients for detected contaminants, was conducted in relation to available species sensitivity distributions. A probabilistic SSD based risk assessment, calculating potential risk distributions, was also conducted for contaminants with the required number of data points available. Metals were the most commonly detected (and measured) substances and also presented the greatest risk, especially copper and zinc, but also nickel, lead and cadmium. For these metals, environmental concentrations overlapped levels found to cause effects in toxicity studies, indicating the potential for adverse outcomes from exposure. To fully understand the extent of this risk, more detailed studies are needed that assess metal speciation states and bioavailability under the prevailing soil and water chemistry conditions in palm oil plots. Limited studies have measured pesticide concentrations in palm oil systems. In these few cases, only a few active substances have been measured. From the limited information available, potential risks are indicated due to the presence of some insecticides. However, fungicides are also widely used for palm oil disease management, but little data studies are available to assess both exposure and potential effects. To further assess the potential chemical footprint of different palm oil management practices, studies are needed that systematically assess pollutant levels across a range of chemical groups to consider effects within a mixture context.

Climate warming shifts riverine macroinvertebrate communities to be more sensitive to chemical pollutants

Freshwaters are highly threatened ecosystems that are vulnerable to chemical pollution and climate change. Freshwater taxa vary in their sensitivity to chemicals and changes in species composition can potentially affect the sensitivity of assemblages to chemical exposure. Here we explore the potential consequences of future climate change on the composition and sensitivity of freshwater macroinvertebrate assemblages to chemical stressors using the UK as a case study. Macroinvertebrate assemblages under end of century (2080-2100) and baseline (1980-2000) climate conditions were predicted for 608 UK sites for four climate scenarios corresponding to mean temperature changes of 1.28 to 3.78°C. Freshwater macroinvertebrate toxicity data were collated for 19 chemicals and the hierarchical species sensitivity distribution model was used to predict the sensitivity of untested taxa using relatedness within a Bayesian approach. All four future climate scenarios shifted assemblage compositions, increasing the prevalence of Mollusca, Crustacea and Oligochaeta species, and the insect taxa of Odonata, Chironomidae, and Baetidae species. Contrastingly, decreases were projected for Plecoptera, Ephemeroptera (except for Baetidae) and Coleoptera species. Shifts in taxonomic composition were associated with changes in the percentage of species at risk from chemical exposure. For the 3.78°C climate scenario, 76% of all assemblages became more sensitive to chemicals and for 18 of the 19 chemicals, the percentage of species at risk increased. Climate warming-induced increases in sensitivity were greatest for assemblages exposed to metals and were dependent on baseline assemblage composition, which varied spatially. Climate warming is predicted to result in changes in the use, environmental exposure and toxicity of chemicals. Here we show that, even in the absence of these climate-chemical interactions, shifts in species composition due to climate warming will increase chemical risk and that the impact of chemical pollution on freshwater macroinvertebrate biodiversity may double or quadruple by the end of the 21st century.

Assessing cardiovascular toxicity in zebrafish embryos exposed to copper nanoparticles

The toxicity of copper nanoparticles (CuNPs) to aquatic animals, particularly their effects on the cardiovascular system, has not been thoroughly investigated. In the present study, zebrafish embryos were used as a model to address this issue. After exposure to different concentrations (0.01, 0.1, 1, and 3 mg/L) of CuNPs for 96 h (4 to 100 h post-fertilization), cardiac parameters of the heart rate (HR), end-diastolic volume (EDV), end-systolic volume (ESV), stroke volume (SV), ejection fraction (EF), and cardiac output (CO), and vascular parameters of the aortic blood flow velocity (ABFV) and aortic diameter (AD) were examined by a video-microscopic method. Morphologically, CuNPs induced concentration-dependent pericardial edema. Although CuNPs did not alter the HR, they significantly reduced the EDV, SV, and CO at ≥0.1 mg/L, the ESV and EF at 3 mg/L, the ABFV at ≥0.1 mg/L, and the AD at ≥1 mg/L. Transcript levels of several cardiac genes, nppa, nppb, vmhc, and gata4, were also examined. CuNPs significantly suppressed nppa and nppb at ≥0.1 mg/L, gata4 at ≥0.01 mg/L, and vmhc at 1 mg/L. This study demonstrated that CuNPs can induce cardiovascular toxicity at environmentally relevant concentrations during fish embryonic development and highlight the potential ecotoxicity of CuNPs to aquatic animals.

Cross-Species Extrapolation of Biological Data to Guide the Environmental Safety Assessment of Pharmaceuticals-The State of the Art and Future Priorities

The extrapolation of biological data across species is a key aspect of biomedical research and drug development. In this context, comparative biology considerations are applied with the goal of understanding human disease and guiding the development of effective and safe medicines. However, the widespread occurrence of pharmaceuticals in the environment and the need to assess the risk posed to wildlife have prompted a renewed interest in the extrapolation of pharmacological and toxicological data across the entire tree of life. To address this challenge, a biological "read-across" approach, based on the use of mammalian data to inform toxicity predictions in wildlife species, has been proposed as an effective way to streamline the environmental safety assessment of pharmaceuticals. Yet, how effective has this approach been, and are we any closer to being able to accurately predict environmental risk based on known human risk? We discuss the main theoretical and experimental advancements achieved in the last 10 years of research in this field. We propose that a better understanding of the functional conservation of drug targets across species and of the quantitative relationship between target modulation and adverse effects should be considered as future research priorities. This pharmacodynamic focus should be complemented with the application of higher-throughput experimental and computational approaches to accelerate the prediction of internal exposure dynamics. The translation of comparative (eco)toxicology research into real-world applications, however, relies on the (limited) availability of experts with the skill set needed to navigate the complexity of the problem; hence, we also call for synergistic multistakeholder efforts to support and strengthen comparative toxicology research and education at a global level. Environ Toxicol Chem 2024;43:513-525. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Pharmaceuticals in the Aquatic Environment: No Answers Yet to the Major Questions

The presence of pharmaceuticals in the environment, especially the aquatic environment, has received a lot of attention in the last 20 plus years. Despite that attention, the two most important questions regarding pharmaceuticals in the environment still cannot be answered. It is not possible to put the threat posed by pharmaceuticals into perspective with the many other threats (stressors) facing aquatic organisms, such as low flows due to over-abstraction of water, inhibited passage of migratory species due to dams and weirs, diseases, algal blooms causing low oxygen levels and releasing toxins, eutrophication, climate change, and so on. Nor is it possible to identify which pharmaceuticals are of concern and which are not. Not only can these key questions not be answered presently, they have received extremely little attention, despite being identified 10 years ago as the two most important questions to answer. That situation must change if resources and expertise are to be effectively used to protect the environment. Environ Toxicol Chem 2024;43:589-594. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Parabens, Triclosan and Bisphenol A in Surface Waters and Sediments of Baiyang Lake, China: Occurrence, Distribution, and Potential Risk Assessment

The extensive use of the parabens triclosan (TCS) and bisphenol A (BPA) has potential adverse effects on human health and aquatic organisms. However, their monitoring information in freshwater lakes is still limited. This study simultaneously summarized the concentrations, spatial distribution characteristics, and correlations of four types of parabens, TCS, and BPA in the surface water and sediment of Baiyang Lake. Finally, the potential risks of target pollutants were evaluated from two aspects: human health risks and ecological risks. The average contaminations of target compounds in surface water and sediment-BPA, TCS, and ∑4 parabens-was 33.1, 26.1, 0.7 ng/L and 24.5, 32.5, 2.5 ng/g, respectively. The total concentration of target compounds at the inlet of the upstream Fu River and Baigouyin River is significantly higher than that near Hunan and the outlet. In addition, Spearman's correlation analysis showed a significant positive correlation between compounds. The health hazards of target compounds in surface water were all within safe limits. However, the risk quotient results indicate that in some locations in surface water, TCS poses a high risk to algae and a moderate risk to invertebrates and fish, and appropriate attention should be paid to these areas.

Significant improvement in freshwater invertebrate biodiversity in all types of English rivers over the past 30 years

There remains a persistent concern that freshwater biodiversity is in decline and being threatened by pollution. As the UK, and particularly England, is a densely populated nation with rivers of modest dilution capacity, this location is very suitable to examine how freshwater biodiversity has responded to human pressures over the past 30 years. A long-term dataset of 223,325 freshwater macroinvertebrate records from 1989 to 2018 for England was retrieved and examined. A sub-set of approximately 200 sites per English Region (1515 sites in total with 62,514 samples), with the longest and most consistent records were matched with predicted wastewater exposure, upstream land cover and terrain characteristics (latitude, altitude, slope gradient and flow discharge). To understand changes in macroinvertebrate diversity and sensitivity with respect to these parameters, the biotic indices of (i) overall family richness, (ii) Ephemeroptera, Plecoptera, Trichoptera (EPT) family richness, and (iii) the Biological Monitoring Working Party (BMWP) scores of NTAXA (number of scoring taxa) and (iv) ASPT (average score per taxon) were selected. A review of how close the BMWP scores come to those expected at minimally impacted reference sites was included. For all latitudes, altitudes, channel slope, river size, wastewater exposure levels, and differing proportions of upstream woodland, seminatural, arable and urban land cover, all diversity or sensitivity indices examined improved over this period, although this improvement has slowed in some cases post 2003. Mean overall family richness has increased from 15 to 25 family groups, a 66 % improvement. The improvement in mean EPT family richness (3 to 10 families, >300 % improvement), which are considered to be particularly sensitive to pollution, implies macroinvertebrate diversity has benefited from a national improvement in critical components of water quality.

Bioaccumulation of chemical elements at post-industrial freshwater sites varies predictably between habitats, elements and taxa: A power law approach

Elevated environmental levels of elements originating from anthropogenic activities threaten natural communities and public health, as these elements can persist and bioaccumulate in the environment. However, their environmental risks and bioaccumulation patterns are often habitat-, species- and element-specific. We studied the bioaccumulation patterns of 11 elements in seven freshwater taxa in post-mining habitats in the Czech Republic, ranging from less polluted mining ponds to highly polluted fly ash lagoons. We found nonlinear, power-law relationships between the environmental and tissue concentrations of the elements, which may explain differences in bioaccumulation factors (BAF) reported in the literature. Tissue concentrations were driven by the environmental concentrations in non-essential elements (Al, As, Co, Cr, Ni, Pb and V), but this dependence was limited in essential elements (Cu, Mn, Se and Zn). Tissue concentrations of most elements were also more closely related to substrate than to water concentrations. Bioaccumulation was habitat specific in eight elements: stronger in mining ponds for Al and Pb, and stronger in fly ash lagoons for As, Cu, Mn, Pb, Se, V and Zn, although the differences were often minor. Bioaccumulation of some elements further increased in mineral-rich localities. Proximity to substrate, rather than trophic level, drove increased bioaccumulation levels across taxa. This highlights the importance of substrate as a pollutant reservoir in standing freshwaters and suggests that benthic taxa, such as molluscs (e.g., Physella) and other macroinvertebrates (e.g., Nepa), constitute good bioindicators. Despite the higher environmental risks in fly ash lagoons than in mining ponds, the observed ability of freshwater biota to sustain pollution supports the conservation potential of post-industrial sites. The power law approach used here to quantify and disentangle the effects of various bioaccumulation drivers may be helpful in additional contexts, increasing our ability to predict the effects of other contaminants and environmental hazards on biota.

Gas chromatography-tandem mass spectrometric analysis of metaldehyde and its metabolite acetaldehyde in initial assessment of hemodialysis abatement of toxicity in live animals

Metaldehyde consumption by pets and other mammals constitute medical emergencies ideally requiring rapid poison removal. The purpose of this study was three-fold: 1) development of a sensitive method for metaldehyde quantitation in patient serum samples by gas chromatography combined with tandem quadrupole mass spectrometry (GC/MS/MS); 2) development of a sensitive method for quantitation of the volatile metaldehyde metabolite acetaldehyde by headspace analysis combined with GC/MS/MS; and 3) an initial assessment of the efficacy of combined dialysis and hemoperfusion treatments in diminishing toxin loads in canine victims of metaldehyde poisoning. Both mass spectrometric approaches relied on Multiple Reaction Monitoring (MRM) methodologies. Metaldehyde extracted via liquid-liquid partitioning from serum was detected with a limit of quantitation (LOQ) of 7.3 ± 1.4 ng/mL with linearity in the range 1-250 ng/mL with accuracy improved by inclusion of a deuterated metaldehyde internal standard. Acetaldehyde was determined to have an LOQ of 0.39 μg/mL with linearity in the range 1-1000 μg/mL. The developed methodologies were applied to canine samples taken over various time points during dialysis treatment. Two of three canine patients showed significant abatement of metaldehyde levels by over 50-fold from initial concentrations while a third was shown to be negative with no measureable metaldehyde. The toxic metabolite acetaldehyde was found in one of the metaldehyde-poisoned patients and the detected acetaldehyde was also reduced by roughly 200-fold during the course of treatment. The designed mass spectrometric techniques were thus successful in demonstrating the efficacy of the applied dialysis-hemoperfusion methods which may find wider applicability against other potentially lethal toxins in poisoned patients in future studies.

Adverse effects of the pesticide chlorpyrifos on the physiology of a damselfly only occur at the cold and hot extremes of a temperature gradient

Ecotoxicological studies considerably improved realism by assessing the toxicity of pollutants at different temperatures. Nevertheless, they may miss key interaction patterns between pollutants and temperature by typically considering only part of the natural thermal gradient experienced by species and ignoring daily temperature fluctuations (DTF). We therefore tested in a common garden laboratory experiment the effects of the pesticide chlorpyrifos across a range of mean temperatures and DTF on physiological traits (related to oxidative stress and bioenergetics) in low- and high-latitude populations of Ischnura elegans damselfly larvae. As expected, the impact of chlorpyrifos varied along the wide range of mean temperatures (12-34 °C). None of the physiological traits (except the superoxide anion levels) were affected by chlorpyrifos at the intermediate mean temperatures (20-24 °C). Instead, most of them were negatively affected by chlorpyrifos (reduced activity levels of the antioxidant defense enzymes superoxide dismutase [SOD], catalase [CAT] and peroxidase [PER], and a reduced energy budget) at the very high (≥28 °C) or extreme high temperatures (≥32 °C), and to lesser extent at the lower mean temperatures (≤16 °C). Notably, at the lower mean temperatures the negative impact of chlorpyrifos was often only present or stronger under DTF. Although the chlorpyrifos effects on the physiological traits greatly depended on the experimentally imposed thermal gradient, patterns were mainly consistent across the natural latitude-associated thermal gradient, indicating the generality of our results. The thermal patterns in chlorpyrifos-induced physiological responses contributed to the observed toxicity patterns in life history (reduced survival and growth at low and high mean temperatures). Taken together, our results underscore the importance of evaluating pesticide toxicity along a temperature gradient and of taking a mechanistic approach with a focus on physiology, to improve our understanding of the combined effects of pollutants and temperature in natural populations.

Chlorpyrifos induced autophagy and mitophagy in common carp livers through AMPK pathway activated by energy metabolism disorder

Water pollution caused by widely used agricultural pesticide chlorpyrifos (CPF) has aroused extensive public concern. While previous studies have reported on toxic effect of CPF on aquatic animal, little is known about its effect on common carp (Cyprinus carpio L.) livers. In this experiment, we exposed common carp to CPF (11.6 μg/L) for 15, 30, and 45 days to establish a poisoning model. Histological observation, biochemical assay, quantitative real-time polymerase chain reaction (qRT-PCR), Western blot, and integrated biomarker response (IBR) were applied to assess the hepatotoxicity of CPF in common carp. Our results displayed that CPF exposure damaged histostructural integrity and induced liver injury in common carp. Furthermore, we found that CPF-induced liver injury may be associated with mitochondrial dysfunction and autophagy, as evidenced by swollen mitochondria, broken mitochondrial ridges, and increased the number of autophagosomes. Moreover, CPF exposure decreased the activities of ATPase (Na⁺/K⁺-ATPase, Ca²⁺-ATPase, Mg²⁺-ATPase, and Ca²⁺Mg²⁺-ATPase), altered glucose metabolism-related genes (GCK, PCK2, PHKB, GYS2, PGM1, and DLAT), and activated energy-sensing AMPK, indicating that CPF caused energy metabolism disorder. The activation of AMPK further induced mitophagy via AMPK/Drp1 pathway, and induced autophagy via AMPK/mTOR pathway. Additionally, we found that CPF induced oxidative stress (abnormal levels of SOD, GSH, MDA, and H₂O₂) in common carp livers, which further contributed to the induction of mitophagy and autophagy. Subsequently, we confirmed a time-dependent hepatotoxicity caused by CPF in common carp via IBR assessment. Our findings presented a new insight into molecular mechanism of CPF induced-hepatotoxicity in common carp, and provided a theoretical basis for evaluating CPF toxicity to aquatic organisms.

Toxicity mechanisms and bioavailability of copper to fish based on an adverse outcome pathway analysis

Copper (Cu) exists in a variety of forms in different aquatic environments, and affects their bioavailability. In this study we provide a systematic review on toxicity of Cu which focuses on identifying evidence in the mechanisms of Cu toxicity, and apply an adverse outcome pathway (AOP) analysis to identify multiple potential mechanisms and their interactions of Cu toxicity to fish. This analysis process included the mechanisms of behavior toxicant, oxidative toxicant, ion regulation disruption toxicity, as well as endocrine disruption toxicity. It was found that at low levels of Cu exposure, swimming, avoid predators, locating prey and other sensory functions will be impaired, and the organism will suffer from metabolic alkalosis and respiratory acidosis following the inhibition of the carbonic anhydrase active. The main pathway of acute toxicity of Cu to fish is the inhibition of the Na⁺/K⁺-ATPase enzyme, and lead to reduced intracellular sodium absorption, as well as Cu-induced increased cell permeability, in turn resulting in increased sodium ion loss, leading to cardiovascular collapse and respiratory insufficiency. The endocrine disruption toxicity of Cu to fish caused growth inhibition and reproductive reduction. In addition, there are several key pathways of Cu toxicity that are affected by hardness (e.g., Ca²⁺) and intracellular DOC concentrations, including inhibiting Cu-induction, improving branchial gas exchange, altering membrane transport functions, decreasing Na⁺ loss, and increasing Na⁺ uptake. The results of the AOP analysis will provide a robust framework for future directed research on the mechanisms of Cu toxicity.

Biological-Activity-Based Prioritization of Antidepressants in Wastewater in England and Japan

Antidepressants are one of the most commonly prescribed pharmaceuticals. Although they have been frequently detected in aquatic environments around the globe, little is known regarding their adverse effects on humans and aquatic organisms. Recently, an in vitro monoamine transporter inhibition assay was developed to detect transporter-inhibitory activities of antidepressants in wastewater in Japan. However, it was unclear which antidepressants were responsible for transporter-inhibitory activities in wastewater. Herein, the per capita consumption of 32 antidepressants, their excretion of unchanged parent compounds, per capita water consumption, removal rate during wastewater treatment processes, and potency values from the monoamine transporter inhibition assay were used to prioritize antidepressants of concern in effluent wastewater in England and Japan. In both countries, sertraline and O-desmethylvenlafaxine had the highest contribution to inhibitory activities against the human serotonin transporter (hSERT) and zebrafish SERT (zSERT), respectively. It was found that the antidepressants inhibited the zSERT more strongly than the hSERT. The inhibitory activities found against the zSERT in wastewater in England and Japan were higher than thresholds for abnormal behavior in fish. The antidepressants prioritized in this study provide insight into launching environmental monitoring and ecotoxicological studies of antidepressants.

Releases of micropollutants from building surface materials into rainwater and snowmelt induced runoff

Building surface materials, exposed to wash-off by rainwater or snowmelt, are recognised as one of the significant urban diffuse pollution sources contributing to the impairment of stormwater quality. The pollution conveyed by roof runoff originates from two potential sources, migration of surface material constituents, or wash-off of pollutants deposited on the surface by atmospheric deposition. This study investigated the releases of metals and several groups of contaminants of emerging concern: alkylphenols, alkylphenol ethoxylates, and phthalates, from commercially available materials, which are commonly used on buildings and structure surfaces in the urban environment. The materials tested included the following: metal sheets of stainless steel, copper, zinc, galvanised steel, corten steel, corrugated and coated steel, coated zinc; and bitumen-based roofing felt and shingles, as well as polyvinyl chloride (PVC) from two manufacturers. The stainless steel was considered a control material serving to estimate pollutant contributions deposited on the pilot panels from the surrounding environment. Moreover, this study presents novel data on roof snowmelt induced runoff quality, not reported in the previous literature. The experimental setup consisted of 2-m² rectangular panels mounted in triplicates of each material and placed in an open-air setting on the campus of Luleå University of Technology, Sweden. Runoff leaving the gently sloping material panels was collected during 11 rain and three snowmelt driven runoff events occurring over a five-year period. The results showed that, in general, the micropollutant concentrations and loads were lower in snowmelt than rain induced runoff, and no decreasing trend was detected in the releases of phthalates or metals during the study period. Moreover, on a yearly basis, copper sheets were estimated to release 0.6 g/m² Cu to runoff, zinc and galvanised sheets 1.3 and 0.7 g/m² Zn, respectively, and, PVC sheets were estimated to release up to 78 mg/m² of diisononyl phthalate (DINP).

Dual effect of metals on branchial and renal Na,K-ATPase activity in thermally acclimated crucian carp (Carassius carassius) and rainbow trout (Oncorhynchus mykiss)

Heavy metals are harmful to aquatic animals by disrupting their ionic balance. Here, we compare the effects of three metals, zinc (Zn), nickel (Ni) and manganese (Mn) on Na,K-ATPase activity in gills and kidneys in fish species with different ecophysiological characteristics. Crucian carp (Carassius carassius), a cold-dormant species, and rainbow trout (Oncorhynchus mykiss), a cold-active species, were acclimated to 2 °C and 18 °C, and branchial and renal Na,K-ATPase activities were measure in the presence of Zn, Ni and Mn. Under basal conditions, species-, tissues- and temperature-dependent differences appeared in Na,K-ATPase activity. Renal Na,K-ATPase activity was higher in trout than carp, and cold-acclimation increased Na,K-ATPase activity in both species. Cold-acclimation reduced branchial Na,K-ATPase activity in carp, but no acclimation effect was found in trout. In both species and tissues, Zn stimulated Na,K-ATPase in concentration-dependent manner at 0.1 to 3 μM. At 30 µM, Zn strongly inhibited both branchial and renal Na,K-ATPase in both species. Inhibition by Zn was stronger in trout than carp, but no differences existed between acclimation groups in either species. Ni (0.1-3.0 µM) stimulated renal Na,K-ATPase in crucian carp but not in rainbow trout. At 30 µM, Ni depressed the renal Na,K-ATPase of carp back to the control level. Mn had no statistically significant effect on Na,K-ATPase in either species. At low concentrations, Zn and Ni impose an energetic cost to fish by increasing ATP consumption in Na,K-ATPase activity. At higher concentrations, Zn, but not Ni and Mn, strongly inhibit renal and branchial Na,K-ATPase. Due to differences in baseline activity level and acclimation-induced changes in renal and branchial Na,K-ATPase, metal pollution may impair ion regulation of fish in species-specific manner and depending on season.

Assessment of the exposure of two pesticides on common carp (Cyprinus carpio Linnaeus, 1758): Are the prolonged biomarker responses adaptive or destructive?

Chlorpyrifos (CPF) and cypermethrin (CYP) are two insecticides that have a proven negative effect on non-target aquatic organisms when they enter the surface waters. However, literature on the comparative effects of these pesticides on important aquaculture fish species, such as common carp (Cyprinus carpio Linnaeus, 1758) is not yet scientifically detailed, especially over the long-term. The idea of conducting a long-term exposure is to find out how the observed biomarkers would change compared to the short-term exposure. In the natural environment, toxicants are not present alone, but in combination. By monitoring the long-term impact of individual substances, the state of aquatic ecosystems exposed to various toxicants could be predicted. Thus, this study aimed to evaluate the toxicity of different concentrations of CYP (0.0002, 0.0003, and 0.0006 μg/L) and CPF (0.03, 0.05, and 0.10 μg/L) in 50-L glass tanks on C. carpio, exposed for 30 days under laboratory conditions. A set of histological and biochemical biomarkers in the gills and liver were applied with the chemical analyses of water and fish organs. Furthermore, the condition and hepatosomatic index were calculated to assess the physiological status of the treated carps. The behavioral responses were also monitored, and the respiration rate was analyzed. The results suggest that CYP had a more prominent effect on the histological structure of fish organs, biochemical responses of anti-oxidant enzymes, behavior, and respiration rate compared to the effect of CPF. In addition, the results also indicate that the liver is more susceptible to chronic and chemically induced cellular stress compared to the gills, with overall destructive changes in the histological biomarkers rather than adaptive. Regardless of the scenario, our results provide novel insights into pesticide exposure and the possible biological impacts on economically important freshwater fish, exposed to lower CYP and CPF concentrations, based on the EU legislation (maximum allowable concentrations, MAC-EQS).

Is water quality in British rivers "better than at any time since the end of the Industrial Revolution"?

We explore the oft-repeated claim that river water quality in Great Britain is "better now than at any time since the Industrial Revolution". We review available data and ancillary evidence for seven different categories of water pollutants: (i) biochemical oxygen demand (BOD) and ammonia; (ii) heavy metals; (iii) sewage-associated organic pollutants (including hormone-like substances, personal care product and pharmaceutical compounds); (iv) macronutrients (nitrogen and phosphorus); (v) pesticides; (vi) acid deposition and (vii) other variables, including natural organic matter and pathogenic micro-organisms. With a few exceptions, observed data are scarce before 1970. However, we can speculate about some of the major water quality pressures which have existed before that. Point-source pollutants are likely to have increased with population growth, increased connection rates to sewerage and industrialisation, although the increased provision of wastewater treatment during the 20th century will have mitigated this to some extent. From 1940 to the 1990s, pressures from nutrients and pesticides associated with agricultural intensification have increased in many areas. In parallel, there was an increase in synthetic organic compounds with a "down-the-drain" disposal pathway. The 1990s saw general reductions in mean concentrations of metals, BOD and ammonia (driven by the EU Urban Waste Water Treatment Directive), a levelling out of nitrate concentrations (driven by the EU Nitrate Directive), a decrease in phosphate loads from both point-and diffuse-sources and some recovery from catchment acidification. The current picture is mixed: water quality in many rivers downstream of urban centres has improved in sanitary terms but not with respect to emerging contaminants, while river quality in catchments with intensive agriculture is likely to remain worse now than before the 1960s. Water quality is still unacceptably poor in some water bodies. This is often a consequence of multiple stressors which need to be better-identified and prioritised to enable continued recovery.

Dissolved trace element concentrations and fluxes in the Irrawaddy, Salween, Sittaung and Kaladan Rivers

The Irrawaddy (Ayeyarwaddy) and Salween (Thanlwin) globally rank among the largest rivers for supplying dissolved and particulate material to the ocean. Along with the Sittaung and Kaladan rivers they have societal importance to Myanmar in terms water sources and food production. Despite their importance for global biogeochemical cycles and the ~50 million people who live in their catchments, the chemistry of these rivers is poorly known. This study presents a comprehensive survey of dissolved (<0.22 μm) trace element concentrations (Sr, Fe, Al, Ba, Mn, V, Rb, Cu, Zn, As, Li, Ni, Mo, Cr, U, Pb, Sb, Co, Cs, Tl and Cd) at 38 locations within these river catchments, spanning a period of 2 years. The results highlight the global importance of the Irrawaddy and Salween rivers for trace element global biogeochemical cycles; contributing between 1 and 17 % of global dissolved riverine fluxes to the land-ocean interface for the studied elements. Area normalized dissolved fluxes in these catchments are ~2 to 10 times higher than global average values for most elements, consistent with high rates of chemical weathering. In general, anthropogenic activities have yet to significantly perturb dissolved trace element fluxes in these river systems. The presented dataset should therefore serve as a useful 'natural' baseline, against which future perturbations driven by climate change and/or the development of Myanmar's mining industry could be assessed. Exceptions to this include As in the Sittaung River and Sb, Zn, Pb and As in the Salween River, which may already be significantly impacted by anthropogenic inputs. The former represents a water quality issue of concern for public health, and so constraining the exact sources of As in the Sittaung River should be considered a priority for future research.

A decade of monitoring micropollutants in urban wet-weather flows: What did we learn?

Urban wet-weather discharges from combined sewer overflows (CSO) and stormwater outlets (SWO) are a potential pathway for micropollutants (trace contaminants) to surface waters, posing a threat to the environment and possible water reuse applications. Despite large efforts to monitor micropollutants in the last decade, the gained information is still limited and scattered. In a metastudy we performed a data-driven analysis of measurements collected at 77 sites (683 events, 297 detected micropollutants) over the last decade to investigate which micropollutants are most relevant in terms of 1) occurrence and 2) potential risk for the aquatic environment, 3) estimate the minimum number of data to be collected in monitoring studies to reliably obtain concentration estimates, and 4) provide recommendations for future monitoring campaigns. We highlight micropollutants to be prioritized due to their high occurrence and critical concentration levels compared to environmental quality standards. These top-listed micropollutants include contaminants from all chemical classes (pesticides, heavy metals, polycyclic aromatic hydrocarbons, personal care products, pharmaceuticals, and industrial and household chemicals). Analysis of over 30,000 event mean concentrations shows a large fraction of measurements (> 50%) were below the limit of quantification, stressing the need for reliable, standard monitoring procedures. High variability was observed among events and sites, with differences between micropollutant classes. The number of events required for a reliable estimate of site mean concentrations (error bandwidth of 1 around the "true" value) depends on the individual micropollutant. The median minimum number of events is 7 for CSO (2 to 31, 80%-interquantile) and 6 for SWO (1 to 25 events, 80%-interquantile). Our analysis indicates the minimum number of sites needed to assess global pollution levels and our data collection and analysis can be used to estimate the required number of sites for an urban catchment. Our data-driven analysis demonstrates how future wet-weather monitoring programs will be more effective if the consequences of high variability inherent in urban wet-weather discharges are considered.

Worst-case ranking of organic chemicals detected in groundwaters and surface waters in England

The Environment Agency has been using Gas Chromatography-Mass Spectrometry (GC-MS) and Accurate-mass Quadrupole Time-of-Flight (Q-TOF) / Liquid Chromatography-Mass Spectrometry (LC-MS) target screen analysis to semi-quantitatively measure organic substances in groundwater and surface water since 2009 for GC-MS and 2014 for LC-MS. Here we use this data to generate a worst-case "risk" ranking of the detected substances. Three sets of hazard values relating to effects on aquatic organisms, namely Water Framework Directive EQSs, NORMAN Network PNECs (hereafter NORMAN PNEC) and chronic Species Sensitivity Distribution (SSD) HC50s from Posthuma et al., (2019) were used for the assessment. These hazard values were compared to the highest measured concentration for each chemical to generate a worst-case hazard quotient (HQ). Calculated HQs for each metric were ranked, averaged and multiplied by rank for detection frequency to generate an overall ordering based on HQ and occurrence. This worst-case approach was then used to generate ranking lists for GC-MS and LC-MS detected substances in groundwater and surface water. Pesticides in the top 30 overall ranked list included more legacy pesticides in groundwater and more current use actives in surface water. Specific uses were linked to some high rankings (e.g. rotenone for invasive species control). A number of industrial and plastics associated chemicals were ranked highly in the groundwater dataset, while more personal care products and pharmaceuticals were highly ranked in surface waters. Perfluoroalkyl and Polyfluoroalkyl Substances (PFAS) compounds were commonly highly ranked in both environmental compartments. The approach confirmed high rankings for some substance (e.g. selected pesticides) from previous prioritization exercises, but also identified novel substance for consideration (e.g. some PFAS compounds and pharmaceuticals). Overall our approach provided a simple approach using readily accessible data to identify substances for further and more detailed assessment.

Evolution of pesticide tolerance and associated changes in the microbiome in the water flea Daphnia magna

Exposure to pesticides can have detrimental effects on aquatic communities of non-target species. Populations can evolve tolerance to pesticides which may rescue them from extinction. However, the evolution of tolerance does not always occur and insights in the underlying mechanisms are scarce. One understudied mechanism to obtain pesticide tolerance in hosts are shifts toward pesticide-degrading bacteria in their microbiome. We carried out experimental evolution trials where replicated experimental populations of the water flea Daphnia magna were exposed to the pesticide chlorpyrifos or a solvent control, after which we performed acute toxicity assays to evaluate the evolution of chlorpyrifos tolerance. Additionally, we quantified changes in the microbiota community composition of whole body and gut samples to assess which sample type best reflected the pesticide tolerance of the Daphnia host. As expected, chlorpyrifos-selected clones became more tolerant to chlorpyrifos as shown by the higher EC_5048 h (36% higher) compared with the control clones. This was associated with shifts in the microbiome composition whereby the abundance of known organophosphate-degrading bacterial genera increased on average ~4 times in the chlorpyrifos-selected clones. Moreover, the abundances of several genera, including the organophosphate-degrading bacteria Pseudomonas, Flavobacterium and Bacillus, were positively correlated with the EC_5048 h of the host populations. These shifts in bacterial genera were similar in magnitude in whole body and gut samples, yet the total abundance of organophosphate-degrading bacteria was ~6 times higher in the whole body samples, suggesting that the gut is not the only body part where pesticide degradation by the microbiome occurs. Our results indicate that the microbiome is an important mediator of the development of tolerance to pesticides in Daphnia.

Proportional contributions to organic chemical mixture effects in groundwater and surface water

Semi-quantitative GC-MS and LC-MS measurements of organic chemicals in groundwater and surface waters were used to assess the overall magnitude and contribution of the most important substances to calculated mixture hazard. Here we use GC-MS and LC-MS measurements taken from two separate national monitoring programs for groundwater and surface water in England, in combination with chronic species sensitivity distribution (SSD) HC50 values published by Posthuma et al. (2019, Environ. Toxicol. Chem, 38, 905-917) to calculate individual substance hazard quotients and mixture effects using a concentration addition approach. The mixture analysis indicated that, as anticipated, there was an increased hazard from the presence of a cocktail of substances at sites compared to the hazard for any single chemical. The magnitude of the difference between the hazard attributed to the most important chemical and the overall mixture effect, however, was not large. Thus, the most toxic chemical contributed ≥ 20% of the calculated mixture effect in >99% of all measured groundwater and surface water samples. On the basis of this analysis, a 5 fold assessment factor placed on the risk identified for any single chemical would offer a high degree of in cases where implementation of a full mixture analysis was not possible. This finding is consistent with previous work that has assessed chemical mixture effects within field monitoring programs and as such provides essential underpinning for future policy and management decisions on how to effectively and proportionately manage mixture risks.

Transgenerational effects of zinc in zebrafish following early life stage exposure

Although toxic effects of zinc (Zn) have been well established in the different developmental stages in fish, long-lasting effects of Zn exposure during embryonic development have not been explored. Exposure to an environmentally relevant Zn concentration of 10 μM (650 μg/L) during the first five days after fertilization did not affect survival, body weight, malformations or overall hatching success of F0 and F1 larvae. Zn exposure did, however, result in delayed hatching in both the F0 and F1 generations and caused significant changes in homeostasis of Zn and selenium (Se) in F0 and F1 fish. This was especially pronounced when F1 embryos from Zn-exposed parents were treated with 30 μM (2000 μg/L) Zn. In the F0 generation, skewed sex ratio towards males and changes in homeostasis of Zn, Se and manganese (Mn) in the brain, gill, liver and gonad of adult fish were also observed. These changes were associated with altered expression of Zn- and Mn-regulatory genes and sex differentiation genes in F0 and F1 fish. The present study suggests that fish may carry memory from embryo-larval Zn exposure into adulthood and further to the next generation. The present study shows that ecotoxicological risk of an exposure to Zn during embryo-larval development may persist long after recovery and may also manifest in the F1 generation.

Ecotoxicological risk ranking of 19 metals in the lower Yangtze River of China based on their threats to aquatic wildlife

With thousands of chemicals discharged into the aquatic environment, it is necessary to identify those that are likely to be having the greatest impact on wildlife to better protect the ecosystem. A risk ranking approach was developed to compare the ecotoxicological risk of chemicals on aquatic wildlife with a wide range of environmental measurement data and ecotoxicity data. Nineteen metals including some rarely monitored ones including antimony (Sb), molybdenum (Mo), cobalt (Co), vanadium (V), titanium (Ti) and thallium (Tl) in the lower Yangtze River were risk ranked as a case study. The risk ranking approach was conducted in three tiers: general risk ranking, lethal effects vs. non-lethal effects risk ranking, and species group-specific risk ranking. Iron, copper and titanium were identified as being of greatest concern. The contamination of iron, zinc, copper and nickel was widespread and may have already harmed wildlife according to the overlap between ecotoxicity and monitored levels. Based on this analysis, the risk from copper and some rarely monitored metals (titanium and boron) may have been underestimated. Greater efforts to reduce copper, iron and titanium contamination could make an important difference to the health of Chinese freshwater organisms in the Yangtze River.

Synthetic surfactants in Swiss sewage sludges: Analytical challenges, concentrations and per capita loads

Surfactants are high-production-volume chemicals that are among the most abundant organic pollutants in municipal wastewater. In this study, sewage sludge samples of 36 Swiss wastewater treatment plants (WWTPs), serving 32% of the country's population, were analyzed for major surfactant classes by liquid chromatography mass spectrometry (LC-MS). The analyses required a variety of complementary approaches due to different analytical challenges, including matrix effects (which can affect adduct ion formation) and the lack of reference standards. The most abundant contaminants were linear alkylbenzene sulfonates (LAS; weighted mean [WM] concentration of 3700 μg g^-1 dry weight), followed by secondary alkane sulfonates (SAS; 190 μg g^-1). Alcohol polyethoxylates (AEO; 8.3 μg g^-1), nonylphenol polyethoxylates (NPEO; 16 μg g^-1), nonylphenol (NP; 3.1 μg g^-1), nonylphenol ethoxy carboxylates (NPEC; 0.35 μg g^-1) and tert-octylphenol (tert-OP, 1.8 μg g^-1) were present at much lower concentrations. This concentration pattern agrees with the production volumes of the surfactants and their fates in WWTPs. Branched AEO homologues dominated over linear homologues, probably due to higher persistence. Sludge concentrations of LAS, SAS, and NP were positively correlated with the residence time in the anaerobic digester. Derivation of the per capita loads successfully revealed potential industrial/commercial emission sources. Comparison of recent versus historic data showed a decrease in NPEO and NP levels by one or two orders of magnitude since their ban in the 1980s. By contrast, LAS still exhibit similar concentrations compared to 30 years ago.

Acute warming increases pesticide toxicity more than transgenerational warming by reducing the energy budget

There is increasing awareness that the toxicity of pesticides can to a large extent be modulated by warming, and that temporal exposure scenarios may strongly affect the impact of two stressors. Nevertheless, we lack information on how the exposure duration to warming may shape pesticide toxicity under warming. Furthermore, despite that bioenergetic responses have the potential to generate mechanistic insights in how toxicants interact with warming, this has been understudied in ecotoxicology. To investigate whether warming duration modifies pesticide toxicity, mosquito larvae were exposed to a control temperature at 20 °C or three warming treatments at 24 °C (acute, developmental and transgenerational warming), and to four pesticide treatments (solvent control, and three chlorpyrifos concentrations) in a full factorial design. Chlorpyrifos increased mortality, growth rate and the energy consumed, and reduced the AChE (acetylcholinesterase) activity, the energy available, and the net energy budget (estimated as cellular energy allocation). The warming treatments did not affect mortality, AChE activity, and the energy consumed. However, acute warming increased the growth rate and decreased the energy available, while both acute and developmental warming decreased the cellular energy allocation. A first key finding was that the lethal and sublethal effects of chlorpyrifos were less strong under warming because of a higher degradation in the medium under warming. A second key finding was that, among the warming treatments, the pesticide toxicity was more increased under acute warming than under transgenerational warming. This could be explained by the negative impact of acute warming but not transgenerational warming on the net energy budget. The results in this study provide mechanistic insights that the exposure duration to warming can play an important role in modulating the impact of pesticides under warming. Therefore, including ecologically relevant temporal scenarios of exposure to warming is important in ecotoxicological studies.

Watershed-Scale Risk to Aquatic Organisms from Complex Chemical Mixtures in the Shenandoah River

River waters contain complex chemical mixtures derived from natural and anthropogenic sources. Aquatic organisms are exposed to the entire chemical composition of the water, resulting in potential effects at the organismal through ecosystem level. This study applied a holistic approach to assess landscape, hydrological, chemical, and biological variables. On-site mobile laboratory experiments were conducted to evaluate biological effects of exposure to chemical mixtures in the Shenandoah River Watershed. A suite of 534 inorganic and organic constituents were analyzed, of which 273 were detected. A watershed-scale accumulated wastewater model was developed to predict environmental concentrations of chemicals derived from wastewater treatment plants (WWTPs) to assess potential aquatic organism exposure for all stream reaches in the watershed. Measured and modeled concentrations generally were within a factor of 2. Ecotoxicological effects from exposure to individual components of the chemical mixture were evaluated using risk quotients (RQs) based on measured or predicted environmental concentrations and no effect concentrations or chronic toxicity threshold values. Seventy-two percent of the compounds had RQ values <0.1, indicating limited risk from individual chemicals. However, when individual RQs were aggregated into a risk index, most stream reaches receiving WWTP effluent posed potential risk to aquatic organisms from exposure to complex chemical mixtures.

Which Micropollutants in Water Environments Deserve More Attention Globally?

Increasing chemical pollution of aquatic environments is a growing concern with global relevance. A large number of organic chemicals are termed as "micropollutants" due to their low concentrations, and long-term exposure to micropollutants may pose considerable risks to aquatic organisms and human health. In recent decades, numerous treatment methods and technologies have been proposed to remove micropollutants in water, and typically several micropollutants were chosen as target pollutants to evaluate removal efficiencies. However, it is often unclear whether their toxicity and occurrence levels and frequencies enable them to contribute significantly to the overall chemical pollution in global aquatic environments. This review intends to answer an important lingering question: Which micropollutants or class of micropollutants deserve more attention globally and should be removed with higher priority? Different risk-based prioritization approaches were used to address this question. The risk quotient (RQ) method was found to be a feasible approach to prioritize micropollutants in a large scale due to its relatively simple assessment procedure and extensive use. A total of 83 prioritization case studies using the RQ method in the past decade were compiled, and 473 compounds that were selected by screening 3466 compounds of three broad classes (pharmaceuticals and personal care products (PPCPs), pesticides, and industrial chemicals) were found to have risks (RQ > 0.01). To determine the micropollutants of global importance, we propose an overall risk surrogate, that is, the weighted average risk quotient (WARQ). The WARQ integrates the risk intensity and frequency of micropollutants in global aquatic environments to achieve a more comprehensive priority determination. Through metadata analysis, we recommend a ranked list of 53 micropollutants, including 36 PPCPs (e.g., sulfamethoxazole and ibuprofen), seven pesticides (e.g., heptachlor and diazinon), and 10 industrial chemicals (e.g., perfluorooctanesulfonic acid and 4-nonylphenol) for risk management and remediation efforts. One caveat is that the ranked list of global importance does not consider transformation products of micropollutants (including disinfection byproducts) and new forms of pollutants (including antibiotic resistance genes and microplastics), and this list of global importance may not be directly applicable to a specific region or country. Also, it needs mentioning that there might be no best answer toward this question, and hopefully this review can act as a small step toward a better answer.

Multigenerational effects modify the tolerance of mosquito larvae to chlorpyrifos but not to a heat spike and do not change their synergism

While interactions with global warming and multigenerational effects are considered crucial to improve risk assessment of pesticides, these have rarely been studied in an integrated way. While heat extremes can magnify pesticide toxicity, no studies tested how their combined effects may transmit to the next generation. We exposed mosquito larvae in a full factorial, two-generation experiment to a heat spike followed by chlorpyrifos exposure. As expected, the heat spike magnified the chlorpyrifos-induced lethal and sublethal effects within both generations. Only when preceded by the heat spike, chlorpyrifos increased mortality and reduced the population growth rate. Moreover, chlorpyrifos-induced reductions in heat tolerance (CTmax), acetylcholinesterase (AChE) activity and development time were further magnified by the heat spike. Notably, when parents were exposed to chlorpyrifos, the chlorpyrifos-induced lethal and sublethal effects in the offspring were smaller, indicating increased tolerance to chlorpyrifos. In contrast, there was no such multigenerational effect for the heat spike. Despite the adaptive multigenerational effect to the pesticide, the synergism with the heat spike was still present in the offspring generation. Generally, our results provide important evidence that short exposure to pulse-like global change stressors can strongly affect organisms within and across generations, and highlight the importance of considering multigenerational effects in risk assessment.

Turnover of lake sediments treated with sediment microbial fuel cells: a long-term study in a eutrophic lake

Sediment microbial fuel cells (SMFCs) have previously been successfully used to reduce phosphate release from the sediments of eutrophic lakes. In this study, we investigate the risk that SMFCs stimulate sediment decomposition with the unwanted side effect being the release of legacy pollutants stored in sediments. Electrode pairs (16 m² each) were installed in a eutrophic lake in Denmark and the electricity production was monitored over more than a year at three electrode fields. Equations were derived that allow calculation of the substrate turnover by the SMFCs from the working potential, the open circuit potential, and the external resistance of the SMFCs. The resulting turnover data suggest that the decomposition of the sediment is only slightly expedited by the SMFCs, and that the decomposition process is not significantly stimulated by the type of SMFCs installed in the lake. The measured maximum power density with stainless steel electrodes in the lake sediment was 0.9 mW/m², which was sufficient to reduce P outflux from sediment. At this power density, the decomposition half-life of the lake sediment (top 5 cm) is calculated to be 277 years, which is only about 10% of natural lake sediment decomposition half-lives. Higher power densities are not necessary for P fixation but inadvertently increase the risk that legacy pollutants buried in the sediment are released.

Evolution of tolerance to chlorpyrifos causes cross-tolerance to another organophosphate and a carbamate, but reduces tolerance to a neonicotinoid and a pharmaceutical

Exposure to pesticides is a major stressor in freshwater ecosystems. While populations can evolve tolerance to pesticides and thereby ensure their persistence in contaminated environments, this may have important consequences for their sensitivity to other pollutants. Indeed, tolerance to one pollutant may both increase (as a cost of tolerance) or decrease (cross-tolerance) the sensitivity to other pollutants. Despite the increasing concern of pharmaceuticals in waterbodies, no patterns of pesticide-induced (cross-)tolerance have been studied. We conducted 48 h acute toxicity assays with a range of concentrations of different pollutants to determine how the evolution of tolerance to the insecticide chlorpyrifos affects the sensitivity to other pesticides and a pharmaceutical in the water flea Daphnia magna, a keystone zooplankton species in aquatic food webs. We capitalized on an experimental evolution trial with chlorpyrifos, hence could unambiguously identify any patterns in increased tolerance or sensitivity to the other pollutants as a direct result of the evolution of tolerance to chlorpyrifos. We found that evolution of tolerance to chlorpyrifos conferred cross-tolerance to another organophosphate, namely malathion (mean change in EC_50,48h: factor 3.1), and to the carbamate carbaryl (factor 1.7), confirming that a shared mode of action favours the evolution of cross-tolerance. While the evolution of tolerance to chlorpyrifos did not affect the sensitivity to the pyrethroid esfenvalerate, it increased the sensitivity to the neonicotinoid imidacloprid as shown by the decrease in EC_50,48h (factor 0.6). Notably, we demonstrated for the first time that the evolution of tolerance to a pesticide increased the sensitivity to a pharmaceutical, namely fluoxetine (decrease in EC_50,48h with factor 0.7), thereby identifying an overlooked cost of tolerance to a pesticide. Given the increasing exposure to pesticides and pharmaceuticals, our results highlight that considering cross-tolerance and costs of tolerance is crucial in risk assessment of both pesticides and pharmaceuticals in aquatic ecosystems.

A comprehensive aquatic risk assessment of the beta-blocker propranolol, based on the results of over 600 research papers

A comprehensive aquatic environmental risk assessment (ERA) of the human pharmaceutical propranolol was conducted, based on all available scientific literature. Over 200 papers provided information on environmental concentrations (77 of which provided river concentrations) and 98 dealt with potential environmental effects. The median concentration of propranolol in rivers was 7.1 ng/L (range of median values of individual studies 0.07 to 89 ng/L), and the highest individual value was 590 ng/L. Sixty-eight EC50 values for 35 species were available. The lowest EC50 value was 0.084 mg/L. A species sensitivity distribution (SSD) provided an HC50 value of 6.64 mg/L and an HC5 value of 0.22 mg/L. Thus, there was a difference of nearly 6 orders of magnitude between the median river concentration and the HC50 value, and over 4 orders of magnitude between the median river concentration and the HC5 value. Even if an assessment factor of 100 was applied to the HC5 value, to provide considerable protection to all species, the safety margin is over 100-fold. However, nearly half of all papers reporting effects of propranolol did not provide an EC50 value. Some reported that very low concentrations of propranolol caused effects. The lowest concentration reported to cause an effect - in fact, a range of biochemical and physiological effects on mussels - was 0.3 ng/L. In none of these 'low concentration' papers was a sigmoidal concentration-response relationship obtained. Although inclusion of data from these papers in the ERA cause a change in the conclusion reached, we are sceptical of the repeatability of these 'low concentration' results. We conclude that concentrations of propranolol present currently in rivers throughout the world do not constitute a risk to aquatic organisms. We discuss the need to improve the quality of ecotoxicology research so that more robust ERAs acceptable to all stakeholders can be completed.

Steroid hormones in the aquatic environment

Steroid hormones are extremely important natural hormones in all vertebrates. They control a wide range of physiological processes, including osmoregulation, sexual maturity, reproduction and stress responses. In addition, many synthetic steroid hormones are in widespread and general use, both as human and veterinary pharmaceuticals. Recent advances in environmental analytical chemistry have enabled concentrations of steroid hormones in rivers to be determined. Many different steroid hormones, both natural and synthetic, including transformation products, have been identified and quantified, demonstrating that they are widespread aquatic contaminants. Laboratory ecotoxicology experiments, mainly conducted with fish, but also amphibians, have shown that some steroid hormones, both natural and synthetic, can adversely affect reproduction when present in the water at extremely low concentrations: even sub-ng/L. Recent research has demonstrated that mixtures of different steroid hormones can inhibit reproduction even when each individual hormone is present at a concentration below which it would not invoke a measurable effect on its own. Limited field studies have supported the conclusions of the laboratory studies that steroid hormones may be environmental pollutants of significant concern. Further research is required to identify the main sources of steroid hormones entering the aquatic environment, better describe the complex mixtures of steroid hormones now known to be ubiquitously present, and determine the impacts of environmentally-realistic mixtures of steroid hormones on aquatic vertebrates, especially fish. Only once that research is completed can a robust aquatic risk assessment of steroid hormones be concluded.

Unfolding the interaction between microplastics and (trace) elements in water: A critical review

Plastic and microplastic pollution is an environmental and societal concern. The interaction of plastic with organic chemicals in the environment has attracted scientific interest. New evidences have highlighted an unexpectedly high affinity of environmental plastics also for metal ions. The degree and typology of plastic ageing (including from mechanical, UV and biological degradations) appear as a pivotal factor determining such an interaction. These earlier evidences recently opened a new research avenue in the plastic pollution area. This review is the first to organize and critically discuss knowledge developed so far. Results from field and laboratory studies of metal accumulation on plastic are presented and the environmental factors most likely to control such an interaction are discussed. On the light of this knowledge, a generalist conceptual model useful for building hypotheses on the mechanisms at stake and directing future studies was elaborated and presented here. Furthermore, all available data on the thermodynamics of the plastic-metal interaction obtained from laboratory experiments are inventoried and discussed here, highlighting methodological and technical challenges that can potentially affect cross-comparability of data and their relevance for environmental settings. Finally, insights and recommendations on experimental approaches and analytical techniques that can help overtaking current limitations and knowledge gaps are proposed.

Cardiac Toxicity of Cadmium Involves Complex Interactions Among Multiple Ion Currents in Rainbow Trout (Oncorhynchus mykiss) Ventricular Myocytes

Cadmium (Cd²⁺ ) is cardiotoxic to fish, but its effect on the electrical excitability of cardiac myocytes is largely unknown. To this end, we used the whole-cell patch-clamp method to investigate the effects of Cd²⁺ on ventricular action potentials (APs) and major ion currents in rainbow trout (Oncorhynchus mykiss) ventricular myocytes. Trout were acclimated to +4 °C, and APs were measured at the acclimated temperature and elevated temperature (+18 °C). Cd²⁺ (10, 20, and 100 µM) altered the shape of the ventricular AP in a complex manner. The early plateau fell to less positive membrane voltages, and the total duration of AP prolonged. These effects were obvious at both +4 °C and +18 °C. The depression of the early plateau is due to the strong Cd²⁺ -induced inhibition of the L-type calcium (Ca²⁺ ) current (I_CaL ), whereas the prolongation of the AP is an indirect consequence of the I_CaL inhibition: at low voltages of the early plateau, the delayed rectifier potassium (K⁺ ) current (I_Kr ) remains small, delaying repolarization of AP. Cd²⁺ reduced the density and slowed the kinetics of the Na⁺ current (I_Na ) but left the inward rectifier K⁺ current (I_K1 ) intact. These altered cellular and molecular functions can explain several Cd²⁺ -induced changes in impulse conduction of the fish heart, for example, slowed propagation of the AP in atrial and ventricular myocardia (inhibition of I_Na ), delayed relaxation of the ventricle (prolongation of ventricular AP duration), bradycardia, and atrioventricular block (inhibition of I_CaL ). These findings indicate that the cardiotoxicity of Cd²⁺ in fish involves multiple ion currents that are directly and indirectly altered by Cd²⁺ . Through these mechanisms, Cd²⁺ may trigger cardiac arrhythmias and impair myocardial contraction. Elevated temperature (+18 °C) slightly increases Cd²⁺ toxicity in trout ventricular myocytes. Environ Toxicol Chem 2021;40:2874-2885. © 2021 SETAC.

Transgenerational exposure to warming reduces the sensitivity to a pesticide under warming

Despite the increased attention for temporal aspects of stressor interactions and for effects of warming in ecotoxicological studies, we lack knowledge on how different exposure durations to warming may affect pesticide sensitivity. We tested how three types of exposure duration to 4 °C warming (acute, developmental and transgenerational exposure to 24 °C vs 20 °C) shape the effect of the pesticide chlorpyrifos on two ecologically relevant fitness-related traits of mosquito larvae: heat tolerance and antipredator behaviour. Transgenerational (from the parental generation) and developmental (from the egg stage) warming appeared energetically more stressful than acute warming (from the final instar), because (i) only the latter resulted in an adaptive increase of heat tolerance, and (ii) especially developmental and transgenerational warming reduced the diving responsiveness and diving time. Exposure to chlorpyrifos decreased the heat tolerance, diving responsiveness and diving time. The impact of chlorpyrifos was lower at 24 °C than at 20 °C indicating that the expected increase in toxicity at 24 °C was overruled by the observed increase in pesticide degradation. Notably, although our results suggest that transgenerational warming was energetically more stressful, it did reduce the chlorpyrifos-induced negative effects at 24 °C on heat tolerance and the alarm escape response compared to acute warming. Our results provide important evidence that the exposure duration to warming may determine the impact of a pesticide under warming, thereby identifying a novel temporal aspect of stressor interactions in risk assessment.

The pace-of life explains whether gills improve or exacerbate pesticide sensitivity in a damselfly larva

Trait-based approaches are promising to make generalizations about the sensitivity of species and populations to pesticides. Two traits that may shape the sensitivity to pesticides are the surface area (related to pesticide uptake) and the metabolic rate (related to pesticide elimination). We compared the sensitivity of damselfly larvae to the pesticide chlorpyrifos and how this was modified by loss of external gills (autotomy, reducing the surface area) in both fast pace-of-life (high metabolic rate) and slow pace-of-life (low metabolic rate) populations of Ischnura elegans. The slow-paced populations were more sensitive to the pesticide than the fast-paced populations in terms of survival, growth and energy metabolism. This suggests the higher metabolic rate of fast-paced populations enabled a faster pesticide elimination. Pesticide exposure also reduced heat tolerance, especially in slow-paced larvae under hypoxia. Gill loss had opposite effects on pesticide sensitivity in slow- and fast-paced populations. In slow-paced larvae, gill loss lowered the sensitivity to the pesticide, while in fast-paced larvae, gill loss increased the sensitivity. This difference likely reflects the balance between the roles of the gills in pesticide uptake (more detrimental in slow-paced populations) and oxygen uptake (more important in fast-paced populations). Our results highlight the need to consider trait interactions when applying trait-based approaches to predict the sensitivity to pesticides.

Acclimation to cyclic hypoxia improves thermal tolerance and copper survival in the caridean shrimp Palaemon varians

In response to the continuous variation of environmental parameters, species must be able to adjust their physiology to overcome stressful conditions, a process known as acclimatization. Numerous laboratory studies have been conducted to understand and describe the mechanisms of acclimation to one environmental stressor (e.g. cyclic hypoxia), but currently our understanding of how acclimation to one stressor can change tolerance to a subsequent stressor is limited. Here, in two different experiments, we used the shrimp Palaemon varians to test how, following 28-days acclimation to cyclic hypoxia (mimicking a cyclic hypoxic regime currently found in its natural habitat), critical thermal maximum (CT_max) and sensitivity to copper (Cu²⁺) exposure (30 mgL^-1) changed in comparison to shrimp acclimated to normoxic conditions and then exposed to thermal stress or Cu²⁺. Acclimation to cyclic hypoxia improved both CT_max (~1 °C higher than controls) and survival to acute Cu²⁺ exposure (~30% higher than controls) and induced significant gene expression changes (i.e. up-regulation of heat shock protein 70 - HSP70, hypoxia inducible factor - HIF, phosphoenolpyruvate carboxykinase - PEPCK, glucose 6-P transporter - G6Pt, metallothionein - Mt, and down-regulation of hemocyanin - Hem) in animals acclimated to cyclic hypoxia. Our results demonstrate how acclimation to cyclic hypoxia improved tolerance to subsequent stressors, highlighting the complexity of predicting organismal performance in variable (i.e. where multiple parameters can simultaneously change during the day) environments.

Risks to aquatic environments posed by 14 pharmaceuticals as illustrated by their effects on zebrafish behaviour

The presence of pharmaceutical residues in aquatic ecosystems is a worldwide problem that may pose serious threats and challenges to the environment, especially to the safety of aquatic biota. In the present study, we investigated the effects of 14 environmentally relevant pharmaceutical compounds on individual and collective-related behaviours in juvenile zebrafish (Danio rerio) for 21 days. The tested concentrations of the compounds spanned three orders of magnitude. This study also compared the potential risks of these compounds in Chinese surface waters based on the data on their toxic effects or only on behavioural effects. In the case of individual behaviours, most antidepressants, but not anti-inflammatory agents or blood lipid-lowering agents, decreased fish locomotor activity (LMA) and individual social activity (IDS); however, all three classes of compounds induced significant disruptions in the light/dark transition locomotor response (LMR-L/D) performance, even at lower treatment levels (0.1-1 μg/L). Furthermore, collective behaviour (CLB) analysis suggested that most of the compounds significantly altered the group sociability of fish and frequently occurred at environmentally relevant concentrations. Finally, a risk assessment suggested that the presence of ibuprofen, fluoxetine, and venlafaxine in the surface waters of China poses a relatively high risk to fish, regardless of the risk ranking based on the data of the toxic or behavioural effects.

Occurrence of micropollutants in the Yesilirmak River Basin, Turkey

The European Water Framework Directive (WFD) (2000/60/EC) is the most visionary piece of European environmental legislation that aims to achieve good water status of both surface water and groundwater bodies. The Directive provides a fundamental basis for surface water monitoring activities in the European Member States. The objective of this study is to investigate the occurrence of micropollutants in the Yesilirmak River and to develop a cost-effective monitoring strategy based on spatiotemporal data. A 2-year seasonal monitoring program was conducted between 2016 and 2018, and the water samples were analyzed for 45 priority substances as defined by the WFD and 250 national river basin-specific pollutants. In the basin, 166 pollutants were quantified in at least one of the samples with individual concentrations ranging from 6 × 10^-6μg/L to 100 mg/L. Fifty-four pollutants with a frequency of occurrence greater than 5% were selected for further evaluation. Based on statistical evaluation of the data, 20 pollutants were identified as the pollutants of primary concern. These 20 pollutants were grouped under three categories (metals, biocides, and industrial organic compounds) and their spatiotemporal distributions in the basin were assessed to establish a monitoring strategy specific to each pollutant category. The results of the study revealed that the common season for the monitoring of all pollutant categories was the spring. This study provides a generic methodology for the development of a cost-effective water quality monitoring strategy, which can be applicable for use in different basins and pollutant datasets.

A review of distribution and risk of pharmaceuticals and personal care products in the aquatic environment in China

Due to the extensive use and pseudo-persistence of pharmaceuticals and personal care products (PPCPs), they are frequently detected in the aqueous environment, which has attracted global attention. In this paper, accumulation data of 81 PPCPs in surface water or sediment in China were reported. In addition, 20 kinds of PPCPs with high frequency were selected and their ecological risk assessment was conducted by risk quotient (RQs). The results indicated that the concentration detected in surface water and sediment ranged from ng/L (ng/kg) to μg/L (μg/kg) in China, which was similar to concentrations reported globally. However, contamination by certain PPCPs, such as caffeine, oxytetracycline, and erythromycin, was relatively high with a maximum concentration of more than 2000 ng/L in surface water. RQs revealed that 14 kinds of PPCPs pose no significant risk or low risk to aquatic organisms, while 6 kinds of PPCPs pose a high risk. Additionally, the pollution characteristics of PPCPs in each watershed are different. The Haihe River watershed and the central and lower Yangtze River were the regions of high concern for erythromycin. Triclosan has potential risks in the Pearl River watershed. This study determined the occurrence and risk of PPCPs in China in the past decade, providing a scientific basis for PPCPs pollution control and risk prevention.

Three decades of trace element sediment contamination: The mining of governmental databases and the need to address hidden sources for clean and healthy seas

Trace elements (TEs) frequently contaminate coastal marine sediments with many included in priority chemical lists or control legislation. These, improved waste treatment and increased recycling have fostered the belief that TE pollution is declining. Nevertheless, there is a paucity of long-term robust datasets to support this confidence. By mining UK datasets (100s of sites, 31 years), we assess sediment concentrations of arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), mercury (Hg), nickel (Ni), lead (Pb) and zinc (Zn) and use indices (PI [Pollution], TEPI [Trace Element Pollution] and I_geo [Geoaccumulation]) to assess TE pollution evolution. PI and TEPI show reductions of overall TE pollution in the 1980s then incremental improvements followed by a distinct increase (2010-13). Zn, As and Pb I_geo scores show low pollution, whilst Cd and Hg are moderate, but with all remaining temporally stable. I_geo scores are low for Ni, Fe and Cr, but increasing for Ni and Fe. A moderate pollution I_geo score for Cu has also steadily increased since the mid-1990s. Increasing site trends are not universal and, conversely, minimal temporal change masks some site-specific increases and decreases. To capture this variability we strongly advocate embedding sufficient sentinel sites within observation networks. Decreasing sediment pollution levels (e.g. Pb and Hg) have been achieved, but stabilizing I_geo and recently increasing TEPI and PI scores require continued global vigilance. Increasing Ni and Fe I_geo scores necessitate source identification, but this is a priority for Cu. Local, regional and world analyses indicate substantial 'hidden' inputs from anti-fouling paints (Cu, Zn), ship scrubbers (Cu, Zn, Ni) and sacrificial anodes (Zn) that are also predicted to increase markedly. Accurate TE input assessments and targeted legislation are, therefore, urgently required, especially in the context of rapid blue economic growth (e.g. shipping).

Identifying conserved polychaete molecular markers of metal exposure: Comparative analyses using the Alitta virens (Annelida, Lophotrochozoa) transcriptome

Polychaetes are vital for evaluating the effects of toxic metals in marine systems, and sensitive molecular biomarkers should be integral to monitoring efforts. However, the few polychaete markers that exist are inconsistent, even within the same species, failing to identify gene expression changes in metal-exposed animals incurring clear metabolic costs. Comparing previously characterised polychaete metal-responsive genes with those of another carefully selected species could identify biomarkers applicable across polychaetes. The ragworm Alitta virens (Sars, 1835) is particularly suited for such comparisons due to its dominance of fully saline coastal areas, widespread distribution, large biomass, and its phylogenetic position relative to other polychaete 'omic' resources. A transcriptome atlas for A. virens was generated and an RNASeq-qPCR screening approach was used to characterise the response to chronic exposures of environmentally relevant concentrations of copper and zinc in controlled mesocosms. Genes presenting dramatic expression changes in A. virens were compared with known metal-responsive genes in other polychaetes to identify new possible biomarkers and assess those currently used. This revealed some current markers should probably be abandoned (e.g. Atox1), while others, such as GST-Omega, should be used with caution, as different polychaete species appear to upregulate distinct GST-Omega orthologues. In addition, the comparisons give some indication of genes that are induced by metal exposure across phylogenetically divergent polychaetes, including a suite of haemoglobin subunits and linker chains that could play conserved roles in metal-stress response. Although such newly identified markers need further characterisation, they offer alternatives to current markers that are plainly insufficient.

Detecting the effects of chronic metal exposure on benthic systems: Importance of biomarker and endpoint selection

Understanding metal toxicity to benthic systems is still an ecotoxicological priority and, although numerous biomarkers exist, a multi-biomarker and endpoint approach with sediment as the delivery matrix combined with life-history relevant exposure timescales is missing. Here we assess potential toxicity by measuring a suite of biomarkers and endpoints after exposing the ecologically important polychaete Alitta(Nereis)virens to sediment spiked with environmentally relevant concentrations of copper and zinc (and in combination) for 3, 6 and 9 months. We compared biomarker and endpoint sensitivity providing a guide to select the appropriate endpoints for the chosen time frame (exposure period) and concentration (relevant to Sediment Quality Guidelines) needed to identify effects for benthic polychaetes such as A. virens. Target bioavailable sediment and subsequent porewater concentrations reflect the global contamination range, whilst tissue concentrations, although elevated, were comparable with other polychaetes. Survival reduced as concentrations increased, but growth was not significantly different between treatments. Metabolic changes were restricted to significant reductions in protein after 9 months exposure across all copper concentrations, and reductions in lipid at high copper concentrations (3 months). Significant changes in feeding behaviour and increases in metallothionein-like protein concentration were limited to the medium and high copper and zinc concentrations, respectively, both after 6 months exposure. Despite data highlighting A. virens' metal tolerance, DNA damage and protein concentrations are the most sensitive biomarkers. Copper and zinc cause biomarker responses at concentrations routinely found in coastal sediments that are characterised as low contamination, suggesting a reappraisal of the current input sources (especially copper) is required.

Prioritization of Pesticides for Assessment of Risk to Aquatic Ecosystems in Canada and Identification of Knowledge Gaps

Pesticides can enter aquatic environments via direct application, via overspray or drift during application, or by runoff or leaching from fields during rain events, where they can have unintended effects on non-target aquatic biota. As such, Fisheries and Oceans Canada identified a need to prioritize current-use pesticides based on potential risks towards fish, their prey species, and habitats in Canada. A literature review was conducted to: (1) Identify current-use pesticides of concern for Canadian marine and freshwater environments based on use and environmental presence in Canada, (2) Outline current knowledge on the biological effects of the pesticides of concern, and (3) Identify general data gaps specific to biological effects of pesticides on aquatic species. Prioritization was based upon recent sales data, measured concentrations in Canadian aquatic environments between 2000 and 2020, and inherent toxicity as represented by aquatic guideline values. Prioritization identified 55 pesticides for further research nationally. Based on rank, a sub-group of seven were chosen as the top-priority pesticides, including three herbicides (atrazine, diquat, and S-metolachlor), three insecticides (chlorpyrifos, clothianidin, and permethrin), and one fungicide (chlorothalonil). A number of knowledge gaps became apparent through this process, including gaps in our understanding of sub-lethal toxicity, environmental fate, species sensitivity distributions, and/or surface water concentrations for each of the active ingredients reviewed. More generally, we identified a need for more baseline fish and fish habitat data, ongoing environmental monitoring, development of marine and sediment-toxicity benchmarks, improved study design including sufficiently low method detection limits, and collaboration around accessible data reporting and management.