Environmental Toxicology and Chemistry最新文献

The risks posed by chemicals released with domestic wastewater can be reduced by treating wastewater prior to its release; but in developing countries such as China, many of its settlements lack the infrastructure to treat its domestic wastewater. Improving our understanding of the risk posed by these chemicals in catchments that are partially served by sewage treatment works would enable this risk to be better managed. The spatially explicit chemical risk assessment model, Geo-referenced Regional Exposure Assessment Tool for European Rivers (GREAT-ER), was used to determine how chemical risk varies across the East River catchment, South-East China, in response to the construction of new sewage treatment works and to population change between 2010 through 2020. We evaluated the risks from two naturally occurring estrogens, estrone and 17β-estradiol, as well as two personal care product ingredients, triclosan and triclocarban. Model predictions suggest that initially, chemical concentrations decrease substantially because of the rapid construction of new sewage treatment works throughout the catchment, but as the rate of construction slowed and population continued to increase, chemical risk increased, with concentrations for most chemicals increasing to levels greater than in 2010. We then explored the potential impact of treating 100% of domestic wastewater within the catchment, which we estimated would sufficiently reduce chemical risk for triclocarban and estrone. Subsequently, to try and reduce the risk posed by triclosan, we theoretically reduced the usage of triclosan until concentrations were reduced to levels below the predicted no effect concentration. The results from this analysis suggested that triclosan usage would need to be reduced by approximately 90% to reach safe concentrations in the East River catchment.

Purple Martins (Progne subis) are migratory aerial insectivores that have experienced a 37% population decline over the past five decades. One hypothesized cause for this decline is exposure to contaminants at their non-breeding grounds. However, non-breeding grounds of Purple Martins extend over 35 degrees latitude in South America, likely resulting in different contaminant exposure scenarios. In this study, we compare total mercury (THg) content in feathers from 247 Purple Martins from two roosts in Brazil: one in the Amazon Basin and another in the Southeast region. We hypothesized that birds in the Amazon region would exhibit the highest feather THg content due to the combined influence of anthropogenic activities and the region's geological features. However, mean THg feather contents were significantly higher in the Southeast (3.2 ± 1.6 μg g-1) than in the Amazon Basin (1.77 ± 0.81 μg g-1), likely driven by local and regional environmental factors, including industrialization and historical land-use change. Our findings highlight the importance of understanding how the non-breeding range of migratory species may influence their contaminant exposure. This information will assist in the development of conservation strategies tailored to the unique environmental conditions migratory species are exposed to throughout their annual cycles.

Microplastics (MPs) have become a major concern for the general public. Although their sources and sinks have been studied, the fate of MPs in the environment remains unclear. Understanding their fate is essential for governments to develop effective countermeasures against MP pollution. In this study, MP pollution was investigated at 22 rivers and 11 beaches in Shizuoka Prefecture, Japan. Polyethylene (PE)-, polypropylene (PP)-, and polystyrene (PS)-MP concentrations in sediments ranged from 0.411 to 423 particles kg-1, 0 to 206 particles kg-1, and 0 to 45.1 particles kg-1, respectively. In river water and seawater, concentrations ranged from 0 to 14.7 particles m-3, 0 to 21.1 particles m-3, and 0 to 6.00 particles m-3, respectively. MP concentrations were rescaled to align with the 1 to 5,000-μm size range used to define the hazardous concentration for 5% of species (HC5). All aligned concentrations in this study were below the HC5 threshold. Population density was found to be significantly correlated with the PE-, PP-, and PS-MP concentrations in river water, and with PE- and PP-MP concentrations in sediments, suggesting that local pollution sources drive MP pollution. The estimated ages of PE-MPs in river water, seawater, and sediments ranged from 0.061 to 5.5 years, 0.25 to 0.63 years, and 0.0 to 4.3 years, respectively. No significant differences in age were observed among sample types or sampling sites. These findings suggest that effective measures to reduce MP emissions could significantly decrease MP pollution within one year in Shizuoka Prefecture.

Microbial decomposers play a crucial role in detritus-based freshwater food webs, yet their disruption by antimicrobial contaminants and the subsequent bottom-up effects on aquatic food webs remain poorly understood. This study investigates how the fungicide Azoxystrobin and the antibiotic Ciprofloxacin affect microbial leaf conditioning, indirectly impact macroinvertebrate community structure, and thus cause shifts of functional feeding groups in stream mesocosms. To this end, black alder leaves were conditioned in the presence of increasing concentrations of either Azoxystrobin or Ciprofloxacin. Subsequently, the conditioned leaves were transferred to stream mesocosms, colonized by macroinvertebrate communities from a least-impacted stream, where such leaves served as the primary food source. Azoxystrobin significantly reduced fungal biomass on leaves by up to 80%, likely leading to lower detritus quality, impaired conditioning, and cascading shifts in macroinvertebrate communities (p = 0.04). Gammarus fossarum as a dominant species in the studied mesocosm, increased in abundance contributing 18% to community dissimilarity with increasing Azoxystrobin-treated leaves most likely through dietary flexibility and compensatory feeding of leaves or other sources. Chironomidae (Orthocladiinae, Chironomini, Tanytarsini), in contrast, declined (24% dissimilarity contribution), likely due to their reliance on well-conditioned detritus. Shredders (29%), predators (18%), and scrapers (14%) contributed most to macroinvertebrate community differentiation, indicating trophic propagation beyond primary consumers, that is, shredders. In contrast to the fungicide, the antibiotic Ciprofloxacin did not induce significant changes, suggesting fungal decomposers are the primary driver of detritivore-mediated energy flow. These findings emphasize the critical role of microbial-mediated leaf decomposition in structuring freshwater food webs and highlight potential ecological risks associated with fungicide contamination at microbial level, but with impacts well exceeding the microbial communities.

For over two decades, the Target Lipid Model (TLM) has been used to characterize the aquatic toxicity of hydrocarbons, petroleum products, ionic and other non-ionic organic chemicals across a wide range of organisms. The TLM has also been applied to derive hazard concentrations intended to protect 95% of aquatic species (i.e., HC5). The TLM database has expanded to include multiple acute and chronic data (over 100 species from 8 major taxonomic groups) across over 400 individual chemicals for both standard apical (e.g., mortality, reproduction, growth) and relevant non-apical endpoints (e.g., cardiotoxicity). Given these improvements, there is an opportunity to re-evaluate the lipid-water partitioning models so they are common across the TLM and PETROTOX models. The ability of each partitioning model to predict acute and chronic effects was evaluated using statistical goodness-of-fit descriptors in addition to considerations for model accessibility and ease of application. While all lipid-water partitioning models performed similarly, the Abraham-type formulation of the Polyparameter Target Site Model (pp-TSM) has been selected as the preferred lipid-water partitioning model. Previous estimations of chronic effects HC5s used a statistical extrapolation procedure with distributional constraints or applied boot-strapped error estimation to species sensitivity only. To eliminate distributional constraints and account for additional model prediction errors, an alternative approach is proposed to calculate HC5s using boot-strapped error estimation of the TLM calibration to derive prediction errors which include the uncertainty in model parameters and the empirical toxicity distribution. Predicted HC5s using this method are protective of 95% of species based on comparison to measured acute, chronic, and sublethal data. Advantages of this calculation method are discussed along with implications for future TLM applications.

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.