Environmental Toxicology and Chemistry最新文献

Applying euthanasia before death in acute fish toxicity tests contributes significantly to animal welfare by serving as a "refinement" of the test method. A previous study defined three severe signs as moribund states in Japanese medaka (Oryzias latipes) based on the severity classification of clinical signs for the purpose of euthanizing fish during acute fish toxicity testing before death. However, this approach limits the range of signs that can be used to justify euthanasia. It has also been suggested that predicting the time of death can help determine the appropriate timing for euthanasia in such tests, if the survival time for each clinical sign is known (i.e., the time from onset of a clinical sign to death). In this study, we used video recording equipment to assess the survival times for 12 clinical signs observed in response to eight chemical substances, with the aim of ensuring timely euthanasia for fish during acute toxicity tests using Japanese medaka. We found that euthanasia could be applied to a broader range of signs and was appropriate for many fish exhibiting clinical signs by predicting the latest time of death from the maximum survival time for each clinical sign. Case studies with five chemicals showed that this method allowed euthanasia to be applied in a timely manner to many individuals exhibiting clinical signs, without any deviation from the lethal concentration 50 values obtained using the original test method.

During crop growth cycle, several different plant protection products (PPPs) are often applied in combination or sequentially. Such sequential applications result in unintentional mixtures of residues that may affect ecosystem services supported by non-target organisms such as soil microbes and nematodes. This scenario of sequential PPP application is frequent in agricultural practice but rarely addressed experimentally at field scale with regard to environmental impacts. The objective of this study was to evaluate the effect of individual and sequential application of three PPPs (the herbicide clopyralid, the insecticide zeta-cypermethrin, and the fungicide pyraclostrobin) on soil microbial communities, and on the abundance of free-living nematode. Single applications (at 1× or 10× the agronomical dose) were made to triplicated field plots with each one of the PPPs or all three PPPs in sequence, with untreated plots serving as controls. Plots were sampled before each application and 7 and 28 days thereafter. The composition and abundance of the fungal community were found to be more affected compared to the bacterial community by PPP applications, while the bacterial community structure was influenced mainly by soil properties. Only transient effects of PPP applications were detected on nematode abundance. Higher-tier ecotoxicological tests such as the present field study offer greater ecological relevance compared to laboratory tests but are challenged by environmental variations that should be accounted for when evaluating the ecotoxicity of pesticides on soil microorganisms.

The trophic magnification factor (TMF) is an important metric for evaluating chemical biomagnification in food webs. However, reported TMF values of cyclic volatile methylsiloxanes (VMS) vary widely, presumably due to the spatial gradient of chemical concentrations and sampling biases. This study surveyed biota and sediment concentrations of cyclic VMS and two reference polychlorinated biphenyls (PCBs; PCB-153 and PCB-180) in the rocky and sandy areas of the Yugawara coast, Japan. Biota concentrations and TMFs were also predicted by the Multibox-AQUAWEB model for the food webs in the same areas. The predicted biota concentrations and TMFs of the cyclic VMS and PCBs were in good agreement with the measured values. In the rocky and sandy areas, the mean TMFs of cyclic VMS were <1 with strong or moderate statistical significance, suggesting trophic dilution, while the mean TMFs of the PCBs exceeded 1 with strong statistical significance, indicating trophic magnification. The Multibox-AQUAWEB model was applied to predict TMFs for three cyclic VMS and five linear VMS in six global aquatic food webs: Lake Erie, False Creek, Lake Pepin, Lake Ontario, Inner Oslofjord, and Tokyo Bay. Predicted TMFs ranged from 0.13 to 1.00 for all VMS-food web pairs, except for L5 in Lake Pepin (TMF = 1.10; 95th percentile confidence interval [0.75, 1.61]), lacking statistical significance (p > 0.05). It is noted that none showed TMFs of VMS >1 with statistical significance. Thus, it is unlikely that VMS would be trophically magnified in aquatic food webs. To improve model predictions, more precise measurements of dietary uptake efficiencies and somatic biotransformation rate constants of VMS are needed, as trends against molecular weight or logKOW were not clearly demonstrated.

Environmental chemicals affectimpact health through diverse pathways, underscoring the need for approaches beyond traditional animal-based testing to capture their transport, transformation, and mechanisms for risk assessment. Network toxicology offers an in silico framework to elucidate such exposure pathways and toxicity mechanisms, thereby supporting new approach methodologies for toxicity assessment. This study utilized network-based approaches to comprehensively characterize the impacts of inorganic arsenic and cadmium contamination in India from a One Health perspective. First, aggregate exposure pathways (AEPs) were constructed by systematically curating India-specific data on the presence of inorganic arsenic and cadmium across environmental and biological states to understand their transport and transformation. Next, inorganic arsenic- and cadmium-induced toxicities were explored by mapping their toxicity endpoints from six exposome-relevant databases to key events across adverse outcome pathways (AOPs) cataloged in AOP-Wiki, revealing 51 and 78 associated AOPs, respectively. Construction of AOP networks further aided in inferring novel taxonomic applicability information. Moreover, the combined AEP-AOP constructs facilitated mechanistic case studies of human and ecological health-relevant pathways and highlighted critical knowledge gaps in terms of human exposures and bioaccumulation within tissues. Further, stressor-species networks constructed using ECOTOX data identified vulnerable species and those with bioaccumulative potential. Additionally, species sensitivity distributions (SSDs) and toxicity-normalized SSDs provided a comparative framework for prioritizing these compounds, and their integration into stressor-species networks highlighted sensitive species, enhancing their relevance for ecological risk assessment. Finally, the risk quotient analysis for Indian rivers revealed that many regions exhibited elevated ecological risks. Overall, this study underscores the value of network toxicology in supporting a One Health-based framework to inform regulatory decision-making and enhance mitigation strategies for inorganic arsenic and cadmium in India.

Commercial beekeepers transport colonies across the United States to provide pollination services for >100 crops, especially for almond production in California. In these agricultural settings, honey bees are exposed to adjuvant compounds that are either included as "inert ingredients" in pesticide formulations or added as a separate adjuvant product to pesticides to improve application characteristics. However, evidence suggests that some of these inert ingredients pose risks to bees. This study used a Potter spray tower to determine the 48-hr acute toxicities (lethal concentration 50) of 37 pesticide inert ingredients or adjuvant principal functioning agents. Additionally, the toxicity trends of 15 alcohol ethoxylates were determined for structural and physical metrics, including moles of ethoxylation, number of carbons in the alcohol group, and hydrophilic-lipophilic balance. Last, median lethal dose values for an organosilicone (Silwet Eco) and a nonionic surfactant (Makon 10) were determined when applied to different parts of the adult honey bee. The results show that 25 of the 37 tested inert ingredients demonstrated a significant 48-hr dose-response and that 15 of these 25 inert ingredients had a median lethal concentration value below the maximum concentration tested. For alcohol ethoxylates, moles of ethoxylation and number of carbons in the alcohol group were not significant predictors for toxicity, but hydrophilic-lipophilic balance did show a significant trend with toxicity. The body placement assay indicated that applications to the dorsal part of the head and ventral thorax were generally the most toxic but that the two adjuvants produced differing results. The findings from this study can guide the selections of adjuvants and pesticide inerts to reduce risks to honey bees.

In acute fish toxicity tests, mortality has traditionally served as the primary endpoint. However, in accordance with the "3Rs" principle-replacement, reduction, and refinement-there is a growing need to minimize the suffering and pain experienced by test fish. In this study we aimed to establish a behavioral framework for identifying the moribund state in zebrafish (Danio rerio), providing a humane and ethically refined alternative endpoint. Continual observation of zebrafish exposed to 10 representative chemicals allowed the documentation of 12 clinical signs, with the severity of the signs evaluated by the death/clinical-sign ratio, which represents the proportion of fish exhibiting a given sign that subsequently died. The signs "immobility," "immobility at surface," and "lethargy" emerged as strong predictors of imminent death, each exhibiting a death/clinical-sign ratio of 1.0 across all tested chemicals and concentrations, indicating that all fish exhibiting these signs died within the 96-hr test period. Furthermore, the survival times from the onset of these signs to death were sufficiently short to justify their definition as moribund states. Accordingly, we defined these signs as moribund endpoints and propose that fish exhibiting any of them should be euthanized during the test period. Notably, these findings align with previously reported results in Japanese medaka, indicating the potential cross-species applicability of these moribund endpoints.

Per- and polyfluoroalkyl substances (PFAS) are synthetic chemicals widely used as surfactants and repellents across industries such as textiles, personal care products, and nonstick cookware. In India, rapid industrialization and urbanization have increased PFAS usage, raising concerns about environmental contamination. Per- and polyfluoroalkyl substances are persistent, bioaccumulative, and have been detected in multi-environmental matrices including humans. This widespread contamination poses health risks to millions through water and food chains. Because PFAS usually occur as complex mixtures, comprehensive toxicity assessments addressing mixtures rather than individual compounds are urgently needed. The zebrafish (Danio rerio) is an established model for rapid toxicity screening and provides predictive insights into human health risks. This study evaluates developmental effects of two PFAS mixtures on zebrafish embryos and larvae: a 2-compound mixture (2-mix) consisting of perfluorooctanoic acid and perfluorobutanesulfonic acid, and a 24-compound mixture (24-mix) including long- and short-chain PFAS and their precursors. Developmental endpoints monitored were survival, hatching success, heart rate, and deformities. Morphometric analyses of head, eye, yolk sac, and pericardial areas were conducted with ImageJ. Oxidative stress was assessed via reactive oxygen species (ROS) quantification, and histopathology evaluated tissue alterations. Results revealed significant developmental toxicity, with the 24-mix causing delayed hatching, growth inhibition, blood accumulation, and reduced heart rate, whereas the 2-mix showed milder effects. Elevated ROS levels indicated oxidative stress in both groups, and histopathology confirmed damage to the eye, brain, and muscles. These findings demonstrate that prolonged exposure to environmentally relevant PFAS concentrations can induce significant biological effects. This study provides critical insights into PFAS mixture toxicity, informing risk assessments and guiding regulatory policy development to protect public health.

Aqueous film-forming foams (AFFFs) are widely used fire suppression products that have been identified as a direct source of environmental per- and polyfluoroalkyl substances (PFAS). Per- and polyfluoroalkyl substance exposure has demonstrated chronic and sublethal effects on biota. Ongoing efforts aim to reduce and, ideally, eliminate PFAS use in AFFF products. However, there is little known about the potential toxic effects of the new PFAS-free AFFFs, specifically on benthic organisms. The objective of this study is to quantify the effects of seven AFFFs on growth in the hard clam, Mercenaria mercenaria, over a 21-day exposure period with juvenile animals. Additionally, AFFF effects are reported from algal toxicity assays and a feeding study. Five of the PFAS-free AFFFs negatively impacted growth over the exposure period, while one PFAS-free AFFF and the reference PFAS-containing AFFF had no observable effect. Median effect concentrations (EC50) for shell growth ranged from 5.81 mg/L to >100 mg/L. Clam dry and wet weights also decreased with increasing exposure concentration (p  < 0.05). Algal growth was impacted over a 96-hr exposure. Impacts were observed to final standing biomass and overall growth rates at the highest exposure concentrations. However, complete lethality was only observed for one PFAS-free product, suggesting lack of food availability was likely not the primary driver of growth inhibition for all products. Net particle clearance rates in AFFF-exposed clams were not found to be impacted, suggesting there was no obvious AFFF influence on organismal feeding ability. The presented results identify chronic effects of exposure to these AFFFs in this economically and ecologically important bivalve species and are expected to inform decisions regarding PFAS replacement AFFF products.

Obtaining fine particulate matter (PM2.5) samples that are consistent with the natural composition of PM2.5 is crucial for toxicological research. However, current extraction methods inevitably alter the physicochemical properties of PM2.5. Based on variations in processing procedures: extraction solvent (water, ethanol, or dimethyl sulfoxide [DMSO]), sonication, and filtration steps (coarse filtration with 40 μm filters and fine filtration with10 μm filters), five PM2.5 extraction methods were developed, designated as WSF10, ESF10, DSF10, DCF10, and DCSF10, respectively. A mathematical model was developed to evaluate the similarity of PM2.5 samples, and the result showed that PM2.5 extracted by the DCF10 method (DMSO extraction, Coarse filtration, Fine filtration) were closest to that of natural PM2.5, with the highest overall similarity value of 0.70 (0.70 ± 0.01). The cytotoxicity of DCF10-extracted PM2.5 was significantly higher than other groups, inhibiting BEAS-2B cell viability by up to 60% after 9 days of exposure, which aligned best with the similarity results. The outcomes highlight that improper extraction methods may underestimate the actual toxicity of PM2.5. Therefore, optimizing and refining PM2.5 extraction protocols is critical for accurately evaluating its toxicity and providing valid evidence for health risk assessment.

Isoxazoline antiparasitic drugs are a new class of ectoparasiticides used in veterinary medicine for companion animals. Four active substances-fluralaner, (es)afoxolaner, lotilaner, and sarolaner-are marketed globally for flea and tick control. Isoxazolines exhibit long plasma half-lives in dogs and cats, with lotilaner reaching 30 days and sarolaner up to 41.5 days in cats. Their bioavailability varies with feeding; fasting significantly reduces lotilaner absorption. These drugs are primarily eliminated via the biliary/fecal route, with fluralaner showing a fecal elimination half-life of 3 to 12 days in felids and 6 to 38 days in canids. The European Medicines Agency has highlighted the risk of these substances contaminating ecosystems, though data on their environmental release are limited. Recent studies suggest that fluralaner and other parasiticides can be transferred to the environment via feces, urine, or pet hair. This study examined isoxazoline fecal elimination in dogs and cats. Elimination half-lives were determined in groups of five dogs or five cats per active substance. All animals received the drug according to label instructions. The estimated median half-lives were 15.5 and 22.0 days for fluralaner and lotilaner in cats, and 22.9, 24.6, 19.7, and 17.4 days for fluralaner, lotilaner, afoxolaner, and sarolaner in dogs, respectively. Fluralaner and lotilaner were still detected in feces after the end of the recommended treatment period. We used Monte Carlo simulations to assess the risk to nontarget arthropods. Environmental risk assessment indicated that dung-feeding insects could be highly exposed to isoxazoline parasiticides, with fluralaner and lotilaner having the greatest potential impact. These findings emphasize the need for further research on environmental contamination (pathways, quantitative estimate) and impact of veterinary parasiticides on nontarget species.