Environmental Toxicology and Chemistry最新文献

Assessment of potential impacts of chemicals on the environment traditionally involves regulatory standard data requirements for acute aquatic toxicity testing using algae, daphnids and fish (e.g., OECD test guidelines (TG) 201, 202, and 203, respectively), representing different trophic levels. In line with the societal goal to replace or reduce vertebrate animal testing, alternative bioassays were developed to replace testing with fish: the fish cell line RTgill-W1 acute toxicity assay (OECD TG249) and the zebrafish embryo acute toxicity test (zFET, OECD TG236). However, previous studies revealed the lower sensitivity of the RTgill-W1 cell line assay and zFET for some neurotoxic chemicals and allyl alcohol, which is presumably biotransformed in fish to the more toxic acrolein (which is predicted well through the cell line assay). To provide an additional alternative to acute fish toxicity, in this study, we analyzed historic ecotoxicity data for fish and daphnids from the EnviroTox Database. We found a considerable variability in acute fish LC50 and acute daphnids EC50 values, particularly for neurotoxic chemicals. Comparing sensitivity of these taxonomic groups according to different neurotoxicity classification schemes indicates that fish rarely represent the most sensitive trophic level of the two. Exceptions here most prominently include a few cyclodiene compounds, which are no longer marketed, and a chemical group that could be identified through structural alerts. Moreover, daphnids are more sensitive than fish to acrolein. This analysis highlights the potential of the Daphnia acute toxicity test, which is usually a standard regulatory data requirement, in safeguarding the environmental protection level provided by the RTgill-W1 cell line assay and the zFET. This research, rooted in decades of efforts to replace the fish acute toxicity test, shifts the focus from predicting fish toxicity 1-to-1 to emphasizing the protectiveness of alternative methods, paving the way for further eliminating vertebrate tests in environmental toxicology.

Legacy contaminants tied to energy production are a worldwide concern. Coal combustion residues (CCRs) contain high concentrations of potentially toxic trace elements such as arsenic (As), mercury (Hg), and selenium (Se), which can persist for decades after initial contamination. CCR disposal methods, including aquatic settling basins and landfills, can facilitate environmental exposure through intentional and accidental releases. Wildlife exposed to CCRs can experience numerous deleterious effects, such as on development, reproduction, and survival. In the current study, we quantified and compared concentrations of As, Hg, Se, and strontium (Sr) within soils and target fauna (three vertebrate and three invertebrate taxa) from a CCR-contaminated site and a reference site within the U.S. Department of Energy's Savannah River Site, South Carolina, USA. Our objectives were to 1) compare current concentrations of tested elements in soil and resident fauna to levels from our reference site, 2) assess natural attenuation of elements in soils by comparing current concentrations to historic levels, and 3) evaluate the biomagnification potential of the elements measured via body burden and trophic position correlations among fauna. Element concentrations were higher in contaminated soils than reference soils; however, concentrations in 2022 were unchanged from concentrations measured in 2003, suggesting no natural attenuation of tested elements. Additionally, target fauna had elevated As, Se, and Sr levels in comparison to reference samples. A positive correlation was observed in southern toads between Sr concentrations and trophic position, as assessed by nitrogen stable isotope ratios, suggesting potential for biomagnification of Sr within our study system. Collectively, our results demonstrate that legacy contaminants are still present and bioaccumulate in a diversity of taxa in a CCR-contaminated site that has not received effluents in over 50 years, suggesting monitoring programs in CCR-contaminated sites should be maintained long term in the absence of remediation.

Polymer-coated fertilizers, widely used in rice cultivation in Japan, contribute to reactive nitrogen management and agricultural productivity but are a source of microplastics in the environment. Here, we investigated microplastics derived from polymer-coated fertilizer (microcapsule) runoff in Japanese paddy fields at 38 sites to quantitatively assess the behavior of microcapsules in paddy fields, and to estimate the total amount of runoff and accumulation in Japan. We also examined the factors causing variations in the amount of runoff among paddy fields. Between 61 and 100% of microcapsule runoff during the irrigation period occurred between puddling and rice transplanting, with concentrations ranging from 2 to 482 mg/m2 in paddy fields. Water management practices and wind direction and speed explained the difference in runoff between plots. The total amount of microcapsules discharged from Japanese paddy fields during the irrigation season was estimated to be between 17 and 6,291 t (median 1,157 t) from the loads obtained in this study. According to fertilizer statistics and our results, total microcapsule accumulation on agricultural land in Japan was estimated to be 75,623 t. These results suggest that paddy fields in Japan will remain a long-term source of marine microplastics.

Per- and polyfluoroalkyl substances (PFAS) are a large class of chemicals of concern for both human and environmental health because of their ubiquitous presence in the environment, persistence, and potential toxicological effects. Despite this, ecological hazard data are limited to a small number of PFAS even though there are over 4000 identified PFAS. Traditional toxicity testing will likely be inadequate to generate necessary hazard information for risk assessment. Therefore, the present study investigated the utility of using transcriptomic points of departure (tPODs) for informing PFAS algal toxicity. Raphidocelis subcapitata, a freshwater green algal species, were exposed for 24 hours in 96 well microplates to multiple concentrations of 22 different PFAS. Following exposure, RNA was extracted, and the transcriptome was evaluated by RNA sequencing followed by concentration response modeling to determine a tPOD for each PFAS. PFAS tPODs, based upon measured concentrations, ranged from 0.9 µg/L for perfluorotridecanoic acid to 1 mg/L for perfluorononanoic acid. These values derived from R. subcapitata exposures were compared to published hazard benchmarks from other taxa (larval fathead minnow and Daphnia magna) and in vitro data. While R. subcapitata was generally more sensitive to the tested PFAS than previously tested taxa and in vitro assays, the algal tPODs were, on average, three orders magnitude greater than the maximum concentrations of PFAS detected in Great Lakes tributaries. This high throughput transcriptomics assay with algae is a promising new approach method for an ecologically relevant, tiered hazard evaluation strategy.

Epilepsy, the most common neurological disorder worldwide, is characterized by sudden paroxysmal brain activity, which can be generalized or focal. Extensive research has explored various treatment strategies for this condition. Our study employed a pilocarpine (PL)-induced seizure model in zebrafish (Danio rerio) embryos and larvae to assess the effects of carbamazepine (CBZ)-loaded chitosan-coated PLGA-Zein nanoparticles (NPs) over 96 hours. We evaluated the developmental toxicity (mortality, malformation, and larval hatching), behavioral changes (sensorimotor reflexes), and histopathological and immunohistochemical alterations in brain tissue, focusing on 5-hydroxytryptamine receptor 4 (5HT4), and brain and muscle ARNT-Like 1 (BMAL1) expressions. Our findings revealed high mortality and malformation rates in groups treated with pure CBZ (PL+CBZ 50 and PL+CBZ 100). These groups also exhibited delayed hatching and impaired sensorimotor reflexes. In contrast, the CBZ-NP-treated groups (PL+CBZ NP 50 and PL+CBZ NP 100) showed hatching rates comparable to the control group, with significantly lower mortality and malformation rates compared to pure CBZ-treated groups. Moreover, intense cytoplasmic expression of 5HT4 and BMAL1 was observed in neuropils of the PL+CBZ 100 group. This study highlights the potential of CBZ-loaded NPs in reducing developmental toxicity and adverse neurological effects associated with pure CBZ treatment in seizure models.

The combination of silver nanoparticles (AgNPs) and ciprofloxacin (CIP) can be considered an alternative to combat multidrug-resistant microbial infections. However, knowledge about their combined toxicity is scarce after being released in an aquatic environment. The present study evaluated the individual toxicity of AgNPs and CIP and their combined toxicity on the unicellular green microalga Chlorella vulgaris, evaluating cellular responses and conducting metabolomic analysis. The median effective concentrations at 96 h (EC50-96h) for AgNPs, CIP, and the mixture were 132 µg L-1, 7000 µg L-1, and 452 µg L-1, respectively. CIP exhibited a synergistic effect with AgNPs. The toxic ranking for C. vulgaris was AgNPs > AgNPs + CIP > CIP. The growth rate was the most evident parameter of toxicity. Cell diameter significantly increased (p < 0.001) at 96 hours for the highest concentrations tested of AgNPs, CIP, and the mixture, with increases of 24%, 41%, and 19%, respectively, compared to the control. Photosynthetic pigment analyses revealed that C. vulgaris upregulated chlorophyll, carotenoids, and pheophytin. Cell exposure to CIP caused an SOS response involving increased protein and carbohydrate concentrations to tolerate antibiotic stress. Exposure to AgNPs and CIP increased catalase and glutathione S-transferase activity, but the mixture decreased the activity. AgNPs increased malondialdehyde content in exposed cells due to fatty acid peroxidation. These pollutants revealed their potential risks in interfering with survival and metabolism. Our findings highlight the possible hazards of co-pollutants at environmentally relevant quantities, providing insights into the individual and combined ecotoxicity of AgNPs and CIP.

Since chemical pollution poses a persistent threat to freshwater ecosystems and biodiversity, innovative methodologies are required to address the ecological risks associated with such pollutants. This study predicts the long-term impacts of chemicals based on an equation that describes the time-dependency of the median lethal and effect concentration (L(E)C50) with the Critical Body Residue concept. This way, the methodology can predict Species Sensitivity Distributions (SSDs) for any given time point. The methodology was extended to predict the Mean Species Abundance Relationships (MSAR) as an indicator of biodiversity. To test and validate the methodology, data from a case study with six freshwater arthropods exposed short- and long-term to imidacloprid was used. The potentially affected fraction of species (PAF) and its opposite (1-PAF) was used to validate the MSAR framework itself. The accuracy of the predicted chronic median lethal concentration (LC50) values was species-dependent. However, except for one species, all predicted chronic LC50 values were within the 95% Confidence Intervals (CIs) of the fits based on only acute data. The mean differences between the predicted and calculated MSARs were between 2% and 6%. The predicted MSARs generally underestimated the impact of imidacloprid. However, all predicted MSARs were either similar or lower than the calculated 1-PAF, and their CIs covered the calculated MSARs. Thus, the study found that the presented methodology is useful for predicting the long-term effects of chemical pollutants.

There is growing interest in transcriptomic points of departure (tPOD) values from in vitro experiments as an alternative to animal test method. The study objective was to calculate tPODs in rainbow trout gill cells (RTgill-W1 following OECD 249) exposed to pesticides, and to evaluate how these values compare to fish acute and chronic toxicity data. Cells were exposed to one fungicide (chlorothalonil), ten herbicides (atrazine, glyphosate, imazethapyr, metolachlor, diquat, s-metolachlor, AMPA, dicamba, dimethenamid-P, metribuzin), eight insecticides (chlorpyrifos, diazinon, permethrin, carbaryl, clothianidin, imidacloprid, thiamethoxam, chlorantraniliprole), and OECD 249 positive control 3,4-dichloroaniline. Pesticide concentrations in wells were modeled with IV-MBM EQP v2.1. Sequencing libraries were prepared with UPXome, and tPODs calculated with ExpressAnalyst. The method identified 14,449 unique genes, with 1,115 genes having >5 counts in the 576 samples sequenced. For all chemicals, tPODs were derived and tPOD mode values ranged from 0.0004 to 125µM with an average of 36µM. There were significant correlations between tPOD mode values (x-value) and EC50s from RTgill-W1 cells (y = 0.92x+1.2, R2=0.9, p < 0.00001; n = 11), rainbow trout acute toxicity LC50s (y = 0.81x+0.8, R2=0.63, p < 0.0001; n = 20), fish chronic sub-lethal effect concentrations (y = 0.53x-0.2, R2=0.4, p = 0.009; n = 16) and fish chronic lethal effect concentrations (y = 0.64x-0.023, R2=0.59, p = 0.0013; n = 14). Bland-Altman plot analyses of these comparisons also showed good agreement. Pathway-level benchmark doses were calculated when statistical requirements were met, and only possible for four pesticides. These findings support the notion that tPODs from short-term in vitro studies may be comparable to effect concentration data from in vivo studies of fish exposed for chronic durations.