Environmental Toxicology and Chemistry最新文献

Amphibians serve a central role in food webs and provide a link between aquatic and terrestrial habitats. Because of their dependence on water, amphibians are susceptible to legacy and emerging contaminants. We investigated mercury (Hg) and per- and polyfluoroalkyl substances (PFAS) concentrations in wild populations of two amphibian species-the green frog (Lithobates clamitans) and the American toad (Anaxyrus americanus)-which exhibit different life histories. We evaluated whether proximity to PFAS point source (State Superfund site) affected PFAS exposures in amphibians and assessed length, mass, sex, diet, and trophic position as predictors of contaminant concentrations. We found higher Hg concentrations in the more aquatic species (i.e., green frog) but higher PFAS concentrations (summed PFAS, perfluorodecanoic acid [PFDA], perfluoroundecanoic acid [PFUnA], perfluorododecanoic acid [PFDoA], perfluorotridecanoic acid [PFTrDA], and perfluorotetradecanoic acid [PFTeDA]) in the more terrestrial species (i.e., American toad). Proximity to the PFAS State Superfund site did not strongly affect PFAS exposures in amphibians. Of the biological predictors tested, diet best explained PFAS concentrations, but other factors (e.g., physiological differences) are likely contributing to the difference in PFAS bioaccumulation between aquatic and terrestrial species. Only three reports on PFAS concentrations in wild amphibians exist, all from contaminated sites in China, reporting much higher concentrations than found here. Additionally, experimental exposure studies have only investigated the effects of exposure to a few PFAS compounds, of which long-chain perfluoroalkyl carboxylic acids detected here (PFDA, PDUnA, PFDoA, PFTrDA, and PFTeDA) are not represented in the literature. To truly understand the effects that detectable PFAS impose on wild amphibians, research is needed on the effects of more PFAS compounds, bioaccumulation in larval and terrestrial amphibians, and the elimination of PFAS via their skin to different media.

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.

Natural complex substances (NCSs) are botanical extracts of unknown or variable composition. Such NCS contain long chain substances that are very difficult or impossible to identify, representing a challenge to characterization and toxicity assessment. This study aims to provide an innovative and relevant method to identify the constituents of galbanum resinoid, experimentally assess, and accurately predict its ecotoxicity. A fractionation technique was used to separate the NCS into three phases: "volatile," "nonvolatile but potentially bioavailable," and potentially "inert." The whole substance (WS) and each fraction were tested as water accommodated fractions (WAFs) for acute and chronic ecotoxicity to algae and daphnids. The toxicity of fractions and the WS was predicted using (a) an in silico method adapted for mixture toxicity testing and (b) the additivity Classification Labelling and Packaging/Global Harmonised System (CLP/GHS) method, based on analytically determined composition. The volatile fraction was more toxic than the nonvolatile fraction, and the inert fraction was not chronically toxic to algae or daphnids. The experimental daphnid chronic toxicity was higher than the acute for the WS because of larger molecules not toxic to their solubility limit in acute studies. The results from the experiments validated the in silico predictions, which accurately predicted toxicity of the fractions and the WS even if rather conservative for chronic daphnids. Also, the in silico method mechanistically explained the WAF test results and attributed the observed toxicity to specific constituents. However, CLP/GHS overpredicted toxicity in all cases and failed to account for observed toxicity. Experimental and in silico approaches appear to be highly complementary to deal with NCSs. Moreover, the in silico method provides a rapid and cost-effective option to obtaining data for difficult-to-test substances.

Polybrominated diphenyl ethers have emerged as a major environmental pollutant, being used as an additive flame retardant in various kinds of products including electronic devices (computers and television sets), upholstery, carpets, plastics, textiles, and building materials. They can undergo the degradation process to form less brominated or low brominated diphenyl ethers in the environment. In the current study, genotoxic, biochemical, histopathological, and ultrastructural scanning electron microscopy (SEM) changes in liver tissue of zebrafish were studied after acute and subchronic exposure of diphenyl ether (DE). The zebrafish were exposed to 2.13 mg/L DE (¼ median lethal concentration [LC50]) and 4.25 mg/L DE (½ LC50) for the acute toxicity assessment and to 425 μg/L DE (1/20th LC50) and 850 μg/L DE (1/10th LC50) for the subchronic toxicity study. After acute and subchronic exposure of DE, % tail intensity in liver tissue was found to be significantly increased in a concentration and duration-dependent manner. The malondialdehyde content, glutathione-S-transferase, and acetylcholinesterase activity in liver tissue were found to be significantly elevated after acute and subchronic exposure of DE, whereas the activity of superoxide dismutase enzyme was found to be depleted in the liver tissue of zebrafish. The histological observations revealed various types of alterations including aggregation of hepatocytic nuclei, necrosis, vacuolization, sinusoidal dilation, disintegrated hepatocytes, and erythrocytic infiltration in liver tissue of zebrafish after DE exposure. The SEM analysis showed changes in the surface of liver tissue such as multiple pore formation, swelling in hepatocytes, necrosis, and degeneration of hepatocytes after acute and subchronic exposure of DE.

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.

The diversity and complexity of Arctic fish communities increases as boreal species expand their range poleward in response to changing environmental conditions. In turn, borealization of fish communities modifies the species composition of Arctic food webs, trophic interactions, and distribution of contaminants. Contaminants in marine fish and how they vary as a function of feeding ecology and location in Arctic and boreal regions is lacking. Here we assessed the drivers of total mercury (THg) and organochlorine pesticides (OCPs) concentrations in boreal capelin (Mallotus villosus), glacier lanternfish (Benthosema glaciale), Greenland halibut (Reinhardtius hippoglossoides), blue hake (Antimora rostrata), and abyssal grenadier (Coryphaenoides armatus) from the northwest Atlantic and eastern Canadian Arctic. We also examined regional differences in THg concentrations in Arctic cod (Boreogadus saida) across the Canadian Arctic. Length/δ15N and species were the most important determinants of THg concentrations in all fishes, with habitat (δ13C and δ34S) also playing a small role. While most OCPs varied by species, only three varied positively by trophic position (i.e., ΣParlar, ΣDDT, and Dieldrin), and one varied by location (i.e., Dieldrin). Generally, demersal fishes had higher Hg and OCP concentrations than pelagic fishes. Mercury concentrations in Arctic cod were higher in the western than the eastern Canadian Arctic, likely due to increased atmospheric inputs in the Beaufort Sea. Given the likely shift to pelagic systems and the replacement of Arctic residents with less contaminated boreal species (e.g., Arctic cod to capelin), we expect Hg to decrease in Arctic food webs with borealization. In contrast, since OCPs did not vary between Arctic and boreal species, we expect little influence of borealization on OCP concentrations in Arctic fishes.

Short-chain per- and polyfluorinated substances (PFAS) are widely distributed in the environment, but their chronic effects on soil organisms exposed over multiple generations remain largely unknown. The present study therefore aimed to investigate the toxicity of perfluorobutane sulfonic acid (PFBS) and its precursor perfluorobutane sulfonamide (FBSA) to the springtail Folsomia candida during five successive generations with the following endpoints: the median lethal concentration (LC50) for adult survival and the median effect concentration (EC50) for reproduction (EC50_repro) and population growth rate (EC50_r). The LC50 and EC50_r of PFBS were above the highest test concentration (1,300 mg/kg dry soil) for all generations, while the EC50_repro was 1,260 and 762 mg/kg dry soil in F2 and F4 (i.e., third and fifth generations), respectively, although the difference was not significant owing to wide 95% confidence intervals. In contrast, FBSA exhibited significant reproductive toxicity and thereby affected the population growth rate, with LC50, EC50_repro, and EC50_r values of 10.3, 1.14, and 1.67 mg/kg dry soil in F0. The extinction of the populations exposed to the two highest FBSA concentrations (8.85 and 88.3 mg/kg dry soil) in F0 hindered toxicity assessment in subsequent generations, with only an EC50_repro of 0.965 mg/kg dry soil determined in F1. Although the effect concentrations were above environmental levels, the more pronounced reproductive toxicity made FBSA >1,140 and >1,350 times more toxic to F. candida reproduction than PFBS in F0 and F1. These findings reveal that understudied PFAS may pose hidden risks, thus emphasizing the need to expand the currently limited spectrum of PFAS considered in environmental risk assessment. This study also highlights the value of long-term hazard assessment of PFAS in multigeneration scenarios, which could better capture the potential risks posed by these very persistent chemicals.

With global lithium (Li) production rising from 6,000 to 100,000 metric tons annually over the past three decades, environmental concerns about elevated anthropogenic Li releases have grown. Whereas marine waters show relatively stable Li concentrations (∼ 180 µg/L Li), freshwater levels vary substantially due to local geological and climatic factors. Using the sensitive freshwater crustacean Daphnia magna, we conducted three independent Daphnia magna reproduction tests according to Organisation for Economic Co-operation and Development 211 guidelines and Good Laboratory Practices on Li compounds, minimizing experimental variability. Reproduction consistently exhibited a steep concentration-response curve, with no observed effect concentration values ranging from 661 to 1,700 µg/L Li. In contrast, recent chronic studies on D. magna reported lower toxicity values by one or two orders of magnitude under apparently similar protocols. We identified four potential confounders, the exact influence of which needs to be disentangled in future studies: Li acclimation prior to exposure, water hardness and alkalinity, body size in controls, and light intensity. We argue that the current dataset on chronic Li toxicity in freshwaters is not robust enough to support the derivation of environmental exposure limits that are both protective and representative of the wide local variability in natural background levels and bioavailability conditions.

Gamma alumina-based nanoparticles (γ-Al2O3 NPs) are widely produced nanomaterials (NMs) with multiple applications. Their release into the environment raises concerns about fate, ecotoxicity, and persistence. Assessing their effects on native species is therefore essential. This study evaluated the sublethal effects of the Ni/γ-Al2O3 nanoceramic catalyst (NC) and its synthesis precursors, γ-Al2O3 support (SPC) and NiO/γ-Al2O3 precursor (PC), on Cnesterodon decemmaculatus, a fish broadly distributed in South American streams. Biomarkers of oxidative stress, neurotoxicity, and Al and nickel (Ni) accumulation were measured in fish exposed to acute sublethal concentrations. The integrated biomarker response index was used to integrate responses and assess overall stress. Results showed inhibition of glutathione S-transferase in all NM exposures and of superoxide dismutase in PC at 50 mg/L and NC at 100 mg/L. Catalase activity increased in 100 mg/L SPC and 50 mg/L NC and lipid peroxidation in 100 mg/L SPC. Acetylcholinesterase activity was significantly inhibited by all treatments. Accumulation of Al significantly increased in fish exposed to all NMs, whereas Ni levels increased under both concentrations of PC and NC. In conclusion, this study demonstrates the metal accumulation of these NMs in specimens of C. decemmaculatus and the ability to cause alterations in the antioxidant response, oxidative stress damage, and neurotoxic effects. This study provides a framework for ecotoxicological assessment of NMs exposure, which is essential to ensure environmental safety.

Inadequate management of e-waste at informal recycling sites contaminates soil. Biochar offers agricultural and environmental benefits, but its effects on soil fauna remain poorly understood. We evaluated biochar's effects on the growth and reproduction of the earthworm, Alma nilotica (Grube, 1855), to determine an application level that mitigates harmful effects of e-waste contaminants without harming soil organisms. Biochar was prepared from dried maize cobs using a closed drum technique at 500 to 530°C. Effects on earthworm growth and reproduction were assessed using Organisation for Economic Co-operation and Development (OECD) test guidelines and test methods. Results indicated that growth and reproduction were inhibited in a dose-dependent manner, by up to 50 ± 6.4% and 68.2 ± 6.6%, respectively, at a 5% application rate without e-waste contaminants. Earthworm length was more sensitive to the e-waste contaminants than weight, showing disproportionate growth. A dose-dependent growth and reproduction inhibition was also observed in biochar-amended e-waste contaminated soil, giving growth and median reproduction inhibitory concentration (95% confidence interval) of 3.75% (3.25-4.30%) and 2.1% (1.9-2.3%) biochar, respectively. Biochar amendment of e-waste soil at 1% significantly improved earthworm growth (2.2 times longer) and reproduction (5 times more offspring) compared to the unamended soil, unlike at 5% biochar amendment, where growth and reproduction were not different from the unamended soil. These findings underscore the importance of considering optimal biochar dosage in soil amendments to enhance earthworm growth and reproduction.