Ecotoxicological tests are usually designed to measure individual-level toxicity, such as impacts on survival rate and fecundity during specific life stages. To assess population-level chemical risk, ecotoxicological test results are often incorporated into theoretical population models. However, because test duration is generally shorter than the lifespan of the test species, not all survival and reproduction parameters required for constructing population models are measured. Current test protocols may therefore overlook individual-level chemical impacts crucial for population dynamics, potentially leading to inaccurate risk assessments. In this study, we evaluated the population-level relevance of the test protocols provided by the Organisation for Economic Co-operation and Development. We first compiled matrix population models that represented the full life cycles of the test species from published papers. We then aggregated the elasticities of the population growth rate to the parameters measured in the tests. The aggregated elasticity, ranging from 0 to 1, indicates how a slight change in vital rates measured in the test affects the population growth rate, representing the population-level relevance of the test protocols. The relevance score of each test was generally below 0.4, but varied depending on the endpoint type and the taxonomic group of the target species. Notably, tests designed for terrestrial invertebrates showed low relevance, indicating a substantial limitation in capturing individual-level defects that may lead to severe population decline in terrestrial invertebrates. Multiple tests targeting the same species covered the life history complementarily, and their combined use increased the population-level relevance. This study provides the overall landscape of the relevance of current ecotoxicological tests to population-level risk assessment, highlighting key directions to better align with population conservation.

Marine sediments play a key role in the biogeochemical cycle of mercury, acting as sinks that facilitate its accumulation in marine organisms and posing a risk to the food security of coastal communities and human health. This study determined the temporal dynamics and environmental variables that influence the transfer of total mercury in dry weight from sediments to fish in artisanal fishing areas of the Pacific and Caribbean coasts of Colombia. The concentrations of total mercury in dry weight were analyzed in the sediment, seston, and muscle (dry wt) of eight fish species caught using two artisanal fishing methods (net and hook), during dry and wet seasons. Biota-sediment accumulation factor (BSAF) was calculated to estimate the transfer of mercury from the sediments to fish. All fish had a BSAF of >1, indicating accumulation of total mercury in dry weight in fish tissues, and values of >2 on average, suggesting their potential as macroconcentrators. The BSAF was higher in demersal fish (family Lutjanidae; 56.7 ± 32.3), and in the Caribbean, where it was up to four times higher than that in the Pacific. The BSAF increased during the wet season, when the lowest concentrations of mercury were in the sediments, due to an increase in bioavailability associated with organic matter. The study identified three patterns of mercury transfer between species, influenced by variables such as organic matter content, total dissolved solids, and environmental mercury concentrations. These results demonstrate a complex dynamic of mercury mobilization controlled by environmental factors and highlight the importance of considering climatic conditions, habitat, and community composition in assessing mercury risks in coastal ecosystems.

In the absence of a robust database of adverse effects to aquatic biota from pharmaceuticals introduced into the environment, alternate approaches are needed to assess risk. One such approach is the Fish Plasma Model (FPM), which can be used to prioritize pharmaceuticals as a function of potential altered biological responses for fish exposed to these chemicals in receiving waters. Other published prioritization schemes assessing various apical effects include quantitative-structure activity relationships (QSARs), cellular assays, and biochemical markers. The FPM provides another line of evidence that is complementary to these approaches. We also examined potential effects due to human Ether-à-go-go-Related Gene (hERG) activity for the active pharmaceutical ingredients (APIs) as another potentially useful and complementary approach for prioritization. In this study we used the FPM to examine predicted effects for the most commonly prescribed pharmaceuticals, which allowed us to focus on the most environmentally relevant drugs potentially toxic to fish. Drugs with Cmax values were examined with a global database of surface water concentrations to predict potential risk for fish exposed to the most biologically active compounds. To prioritize the APIs most likely to cause adverse effects for fish, we limited the list to those with a Response ratio (RR; [plasma]/1%Cmax) ≥1 (n = 57), and those APIs without exposure concentrations exhibiting a 1%Cmax value ≤0.1 ng/mL (n = 50). The majority (n = 63) of the top prioritized APIs on this list fell into six drug classes: hormones (n = 21), antidepressants (n = 13), antihistamines (n = 8), anticholinergics (4), corticosteroids (4), and antihypertensives (n = 13). The FPM is advantageous because it is based on expected low-dose in-vivo biological effects resulting from chemicals designed to interact with a specific target. Currently, the FPM is mostly limited to pharmaceuticals; however, this approach can be expanded to other chemicals with toxicity data expressed as a plasma concentration.

Methyl 2-{[1-(5-fluoropentyl)-1H-indazole-3-carbonyl]amino}-3,3-dimethylbutanoate (5F-ADB), a potent synthetic cannabinoid, induces intense euphoria, hallucinations, and addiction, posing significant risks to human health. Current drug surveillance efforts lack data to identify drug abuse, and the environmental impacts of 5F-ADB entering aquatic systems via synthesis or use remain uncharacterized. To address these gaps, a multi-level assessment system (in vitro-invertebrate-vertebrate) was established to elucidate 5F-ADB metabolic pathways and identify robust biomarkers. Human liver microsomes (HLM), Daphnia magna, and zebrafish were exposed to 5F-ADB, with metabolites profiled using high performance liquid chromatography coupled with mass spectrometry (HPLC-MS). Metabolic pathways were inferred, and metabolite toxicity was evaluated. Results revealed 9, 11, and 22 metabolites in HLM, D. magna, and zebrafish models, respectively. Dominant pathways in HLM and zebrafish included ester hydrolysis, defluorinated-hydroxylation, and combined ester hydrolysis/defluorinated-hydroxylation. D. magna metabolism primarily featured defluorinated-hydroxylation, depentylation, and ester hydrolysis coupled with hydroxylation. Glucuronidation metabolites were exclusive to zebrafish. Based on abundance and stability, H-M4 (ester hydrolysis), D-M1 (ester hydrolysis/depentylation), and Z-M15 (ester hydrolysis/condensation) were identified as key biomarkers for HLM, D. magna, and zebrafish, respectively. Toxicity assessments indicated reduced toxicity for most metabolites versus 5F-ADB. However, H-M7, D-M7, D-M11, and Z-M15 (products of ester hydrolysis/condensation or defluorinated-hydroxylation/oxidation) exhibited comparable toxicity to the parent compound. Critically, D-M7 (defluorinated-hydroxylation/oxidation) demonstrated heightened hydrophilicity and potentially elevated ecotoxicity in D. magna, warranting further ecological risk investigation. This study provides the first multi-trophic metabolic characterization of 5F-ADB, delivering critical data for tracing illicit synthesis, monitoring drug-use distribution, and evaluating environmental hazards of synthetic cannabinoids.

Octamethylcyclotetrasiloxane (D4) is a cyclic volatile methylsiloxane compound associated with the production of polydimethylsiloxanes (PDMS). Depending on processing conditions, silicone fluids made by equilibration polymerization can contain residual D4 at parts-per-million to parts-per-hundred levels. When silicone fluids enter the environment through use or disposal, aquatic organisms may be exposed to residual D4. To accurately assess the contribution of D4 to the aquatic hazard of silicone fluids, knowledge of the partitioning behavior of D4 is needed. In this study, PDMS-to-air partition coefficients (KPDMS-air) for D4 were directly measured at 21 °C using a static equilibration method. The influence of various factors on KPDMS-air was explored, including the PDMS fluid viscosity (molecular weight), the D4 concentration in the polymer, addition of hydrophobized fumed silica to PDMS, and the presence of amine functional groups within the PDMS structure. For permethylated PDMS, log KPDMS-air values varied between 4.39 and 4.53. Incorporation of treated silica filler at up to 25%w/w had no impact on KPDMS-air, while introduction of (aminopropyl)methyl-dimethylsiloxy units to the polymer (3.7 wt% nitrogen) produced modestly lower log KPDMS-air, 4.19. The KPDMS-air values were combined with reported air-water partition coefficients (Kair-water) for D4 to calculate values of KPDMS-water based on the thermodynamic cycle. The resulting log KPDMS-water values ranged from 6.88 to 7.22, which were used to estimate the maximum attainable aqueous D4 concentrations for different polymer/water phase ratios. For a D4 content of 0.025% w/w in the polymer, the current threshold for classification of the polymer as hazardous to the aquatic environment, the maximum aqueous D4 concentration was ≤ 0.032 μg/L. These concentrations were at least 100-fold less than chronic aquatic toxicity thresholds derived from studies with D4, suggesting that the 0.025% w/w threshold is overly stringent in assigning aquatic hazard classifications to PDMS materials like those tested here.

Pharmaceuticals and personal care products (PPCPs) are widely detected in aquatic environments. However, recent studies on the environmental occurrence of currently used PPCPs in Japan are limited. In this study, a nationwide monitoring initiative focusing on PPCPs was undertaken to investigate the occurrence and fate of PPCPs in aquatic environments in Japan. A total of 700 samples were collected and analyzed from 2018 to 2022. Ninety-one PPCPs were detected in the analyzed samples. Three PPCPs (N, N-diethyl-meta-toluamide [DEET], salicylic acid, and crotamiton) were detected at particularly high frequencies, with a prevalence exceeding 99% of analyzed samples. Seasonal variations were observed for several PPCPs across multiple rivers, with concentrations generally increasing during fall/winter and decreasing during spring/summer (except DEET) throughout the sampling period. The detection frequencies and concentrations were higher in PPCPs with higher domestic prescription amounts. Some PPCPs, such as acetylsalicylic acid, exhibited low frequencies and concentrations despite high domestic prescription amounts, suggesting transformation into metabolites or degradates in the aquatic environment. The contribution of sewage treatment plant effluent to the PPCP concentrations in the environment was estimated by examining the correlation between each PPCP and sucralose concentration. Sewage effluents appeared to be a significant contributor to the majority of target PPCPs; however, DEET and certain other PPCPs may originate from alternate sources. This study is the first to provide a comprehensive assessment of the occurrence and fate of PPCPs in Japan's aquatic environment. Future research should assess the environmental and human health risks of these PPCPs and identify the occurrence of their metabolites or degradates in the aquatic environment.

Obtaining clean water is a global priority, as emphasized by the United Nations Sustainable Development Goal 6, which aims to ensure availability and sustainable management of water and sanitation for all. Pharmaceutical pollutants are becoming more prevalent in aquatic environments, triggering public health concerns, negative environmental impacts, and the development of antibiotic resistance. Microalgae hold great potential for bioremediation of antibiotics, although most of the studies to date supporting these observations rely on conditions where artificial wastewater contained one or a few antibiotics. In this study, Chlorella sorokiniana was used to assess the removal of a mixture of 10 antibiotics selected and tested considering environmentally relevant antibiotic concentrations based on data from the National Health Service (United Kingdom). The selected antibiotics had a risk quotient > 1 as calculated by the ratio of predicted environmental concentration (PEC) to predicted no effect concentration. The experimental antibiotic concentration tested for each antibiotic corresponded to their PEC values. After 19 days of incubation, the β-lactam class (amoxicillin, penicillin V, cephalexin) showed the highest percentage of removal (51-85), followed by trimethoprim (24), oxytetracycline (6), metronidazole (6), and sulfamethoxazole (2). Different mechanisms, that is, biodegradation, photodegradation, bioadsorption, and bioaccumulation, were involved at variable range. Increase in algal biomass was observed concomitantly to decrease in the concentration of the tested antibiotics, suggesting their use as a carbon source for cellular growth. In addition, levels of dissolved ammonium, nitrate, phosphate, and chemical oxygen demand, decreased by 88%, 22%, 100%, and 10%, respectively. Our study confirmed the ability of C. sorokiniana to biodegrade antibiotics while also effectively reducing key nutrient loadings.

Fish are exposed to countless chemicals over their lifetime, with the totality of internal exposure termed the eco-exposome. In vitro bioassays can be used to complement targeted chemical analysis to quantify the mixture effects of chemicals in fish and relate them to the effects measured in extracts of water and sediment. Fathead minnows (Pimephales promelas) were exposed in cages for 48 hr and 21 days at four field sites with diverse chemical profiles. Fish, water, and sediment were collected, extracted, and analyzed with four cell-based reporter gene assays. Water from all sites activated xenobiotic metabolism in vitro, whereas only water from a site near a wastewater treatment plant activated the estrogen receptor. Only 5% of water samples were above their effect-based trigger values (EBTs) for surface water, suggesting a low overall chemical burden. In contrast, 77% of bioactive sediment samples exceeded tentative sediment EBTs, suggesting the mixture effects of chemicals in the sediment are likely to be more problematic. Whole fish extracts activated the arylhydrocarbon receptor and oxidative stress response, with the greatest effect observed at a site affected by both legacy and more recent contamination. Interpretation of mixture effects in extracts from caged fish versus laboratory controls was confounded by background contamination of fish food, as well as endogenous chemicals. Comparison of measured mixture effects with mixture effects predicted from detected chemical concentrations and their relative effect potencies indicated that mixture effects in fish extracts were mainly dominated by chemicals detected in sediment. Sediment and water did not reliably serve as a proxy for the eco-exposome. Bioanalytical investigation of whole fish extracts provides a novel approach to comprehensively characterize the fish exposome.

Concerns about the toxic effects of chemical mixtures have led to regulatory organizations considering how best to address exposures to complex mixtures in the environment. The ubiquitous nature of metals means that they are always present in the environment, even if only at very low levels. It is appropriate to consider whether the mixtures of commonly regulated metals in the environment are likely to cause adverse effects on ecosystems if the environmental quality standards (EQSs) for all the individual metals are complied with. The total risk from four metals (copper, lead, nickel, and zinc) was evaluated in terms of the potential effects on freshwater benthic macroinvertebrate communities from the United Kingdom. The total risk was expressed as the sum of the individual risk characterization ratios for each metal (∑RCR). The ecological data are expressed relative to predicted reference conditions to provide an ecological quality ratio, which indicates whether the local community has been affected by any stressors by comparison to unaffected reference conditions. Very high metal exposures, expressed as the ∑RCR value, were found to be associated with reduced ecosystem diversity. However, a 10% reduction in community diversity relative to the predicted unaffected reference conditions is expected to occur only at ∑RCR values of greater than 8 ∑RCR units. This indicates that in "real world" situations, where a suite of inorganic and organic pollutants may be present, if the EQS for each of the individual metals is complied with (in this case, a ∑RCR value no higher than 4), there will likely not be any observable impact on benthic invertebrate community diversity despite the presence of these metals and other contaminants.