Environmental Toxicology and Chemistry最新文献

Florpyrauxifen-benzyl (aquatic tradename ProcellaCOR) is an aquatic herbicide commonly used to control Eurasian watermilfoil (Myriophyllum spicatum) and other invasive aquatic plants. Previous studies have demonstrated effective Eurasian watermilfoil control under low aqueous concentrations (<10 µg L-1) and short exposure times (< 24 hr). Although florpyrauxifen-benzyl possesses an excellent environmental profile and its acute toxicity has been assessed in freshwater model organisms, there has been no work to examine toxicity of this herbicide in salmonids. Therefore, the objective of this study was to evaluate the acute toxicity to Endangered Species Act-listed Chinook salmon (Oncorhynchis tshawytscha). Chinook fry and smolts were exposed to florpyrauxifen-benzyl at 50 and 100 µg L-1 for 96 hr under a 24-hr static renewal protocol at 12 °C. Daily observations included fish startle response, position in the water column, and signs of overt toxicity. No adverse effects of the herbicide were observed at either concentration in both Chinook fry and smolts. Our results indicate that the maximum United States-labeled application rate of florpyrauxifen-benzyl (48 µg L-1 ai) did not result in overt toxicity to juvenile salmonids under the exposure scenarios used in this study.

Environmental risk assessments of chemicals typically rely on standardized ecotoxicological tests that overlook interindividual variability, despite its importance in ecological resilience and evolutionary success. Contaminants can disrupt individual differences by altering life history traits, amplifying fitness disparities, favoring certain phenotypes, and reducing genetic diversity, ultimately affecting population dynamics and adaptability. However, the extent to which pollutants influence interindividual variability and its population-level consequences remains poorly understood. To address this, our study examines the interindividual variability of growth trajectories in the earthworm Aporrectodea caliginosa in response to sublethal exposure to the two active substances of Swing Gold fungicide. Using a longitudinal design with 30 exposed and 30 unexposed individuals, we compared mean and interindividual growth rate variability. While the fungicide had a weak effect on the cohort's mean growth rate, we observed a 3-fold increase in interindividual variability in the exposed group. This increase highlighted a subset of highly sensitive individuals, whose growth was reduced by up to 10% as compared with the average response. Our results suggest that focusing solely on population mean effects could overlook impacts on sensitive individuals, who could serve as early indicators of environmental stress. Incorporating individual variability into ecotoxicological studies is challenging due to the labor-intensive nature of individual monitoring and the need for larger datasets. Nonetheless, these efforts are essential for refining higher-tier environmental risk assessment frameworks, improving safety factors for intraspecies variability, and defining regulatory thresholds. A better understanding of how contaminants affect interindividual variation will enhance the accuracy and ecological relevance of risk assessments, ultimately capturing the long-term implications for population and ecosystem dynamics.

Fludioxonil is an active principle used as a fungicide to prevent fruit rotting during cold storage. In the present study, we assessed the acute (96 hr) toxicity of the commercial formulation Scholar 23SC to embryos and larvae of the common South American toad (Rhinella arenarum), which inhabits the Alto Valle region in Neuquén and Río Negro, Argentina, an area of intensive fruit production. Scholar 23SC caused lethality in embryos and larvae, with median lethal concentration values of 0.355 mg/L and 1.382 mg/L, respectively. Scholar 23SC caused edema, tail flexure, and growth stunt in the developing embryos, with a median effect concentration value of 0.152 mg/L. In turn, larvae displayed swimming alterations and weakness but no malformations. We reviewed bibliographic data on fludioxonil toxicity to other species to perform a Species Sensitivity Distribution analysis, finding a hazardous concentration-5% (HC5) of 14 µg/L. In turn, from environmental concentration reports, we estimated exceedance probabilities of 5.8% for this HC5 and 13.4% when the lower confidence limit (1.75 µg/L) was used as a conservative criterion. Nevertheless, environmental determinations of fludioxonil concentration in irrigation channels of the Alto Valle region were at approximately the HC5 value. We conclude that Scholar 23SC was more toxic to R. arenarum embryos than larvae, and that the embryonic malformations and the larval behavioral alterations pose a threat to the individuals in a realistic environmental scenario as their performance would be hindered.

Mixture toxicity and bioavailability are important topics in ecotoxicological research. Here, we assess the role of bioavailability in determining the combined effects of two metals (Cd, Zn) on Eisenia andrei reproduction. When assessed based on total soil metal concentrations, a significant concentration ratio effect was seen. Mixture modeling using the "MixTox" model approach indicated this pattern was characterized by synergism when Zn was the metal at the highest concentration, changing to antagonism when Cd concentration was highest. Using 0.01 M CaCl2 extractable metal concentrations as the exposure metric, effects were also significantly different from additivity, predominantly being synergistic. This indicates that accounting for putative environmental availability did not explain the interaction. Metal analysis for this fraction indicated no effect of Cd on extractable Zn concentrations, but that Zn increased Cd extractability, potentially explaining the synergy. This bioavailability effect could be explained by replacement of Cd on soil binding sites by Zn, possibly enhanced by the formation of soluble Cd-Cl complexes resulting from increased Cl-counter ion presence with greater ZnCl2 addition. Modeling mixture effects based on earthworm tissue metal concentrations indicated no significant deviations from additivity. The tissue measurements indicated that internal Zn was not affected by soil total or extractable Cd levels. However, tissue Cd was strongly reduced by Zn. Such inhibition of Cd uptake could result from Zn competition with Cd at uptake sites and/or the formation of poorly bioavailable Cd-Cl species. Taken together, these mechanisms explain the concentration ratio dependent toxicity of Cd and Zn, why this is greatest when Cd dominates the mixture, and how, when effects are modeled based on tissue concentrations, effects accord with additivity.

In many crops, pesticides are applied simultaneously or sequentially, exposing soil microarthropods to dynamic residue mixtures. Yet, little is known about the possible ecological effects of such mixtures. This study investigated the effects of three commercial pesticides-clopyralid (herbicide), cypermethrin (insecticide), and pyraclostrobin (fungicide)-applied individually and in sequence on soil microarthropods (Collembola and Acari) in a field setting. Concurrently, standard laboratory tests were conducted to assess the toxicity of the individual pesticide formulations to the reproduction and survival of the Collembola Folsomia candida exposed in the same field soil. In the field, the formulations were applied individually and sequentially at 1× and 10× the recommended dose. Short-term (i.e., 1 week after application) and long-term effects (i.e., 4 weeks after application) on soil microarthropods were evaluated. In the laboratory, concentration-dependent reduction of F. candida survival and reproduction was observed only for pyraclostrobin and cypermethrin, with no-observed effect concentrations of 9.56 and 94.1 mg of active substance per kg dry soil, respectively. In the field, no aggravated effects of the sequential mixture were detected compared to the single pesticide applications. No negative short- or long-term effects were detected on Collembola abundance or diversity from any of the pesticides or their sequential mixture. In contrast, short-term exposure to the insecticide alone or in sequential mixtures significantly reduced Acari abundance in the field, though this effect weakened over time, leaving only a non-significant trend in the long term.

Aquatic hyphomycetes (AHs) are a group of fungi central for the decomposition of organic material in aquatic systems. Despite their ecological relevance, ecotoxicological studies involving AHs are fairly scarce. With the aim to better understand AH responses to changes in abiotic factors and increasing levels of contaminants, we explored their sensitivity in a multifactorial approach. Therefore, we assessed the radial growth response of three AH species (Alatospora acuminata, Articulospora tetracladia, and Tetracladium marchalianum) to three temperatures (12, 16, and 20 °C) and nutrient levels (0.0, 0.5, and 1.5% malt extract, w/v) in combination with increasing concentrations of the model fungicide trifloxystrobin (0 to 625 µg/L) over 21 days. The results showed a significant interaction between factors, with temperature being the most significant by potentiating trifloxystrobin toxicity for AH growth. The fungicide affected AH species in the low µg/L range with the lowest effect concentration of 0.1 µg/L for A. tetracladia. Previous study points to a regulatory acceptable concentration of 0.1 µg/L based on the ecotoxicological data of the most sensitive groups reported, which did not include AHs. Particularly in light of the ecological importance of them, their sensitivity to trifloxystrobin shown in our study highlights a fundamental concern when projecting the environmental risk of pesticides that directly affect aquatic fungi.

Neotropical stingless bees have frequently been reported to possess high biodiversity, ecological significance, and sensitivity to insecticides. Surprisingly, few studies have been conducted so far to assess their sensitivity to neonicotinoid insecticides, although there are indications that this insecticide class is especially toxic to stingless bees. The aim of this study was therefore to evaluate the acute oral and topical toxicity of two neonicotinoids, imidacloprid and thiamethoxam, to the neotropical stingless bee Melipona scutellaris. Besides these active ingredients, commercial products containing them were also evaluated. The commercial products were more toxic to the bees than the active ingredients, which may be due to direct toxicity of coformulants and indirectly through their higher biological activity and facilitation of uptake by organisms. The neonicotinoids were more toxic through topical contact than oral exposure. This is the opposite trend to that previously reported for honeybees, which is explained through differences in life-history traits with stingless bees. M. scutellaris was more sensitive to the test substances than standard bee test species commonly used in (temperate) toxicity assessments. This thus stresses the need to include stingless bees in neotropical risk assessments. The relatively high mortality occasionally observed in control groups highlights the biological sensitivity of stingless bees to laboratory conditions rather than a methodological flaw. This finding reinforces the importance of refining experimental setups by minimizing handling stress and improving cage microclimate to enhance control survival and ensure even greater robustness in future toxicity assessments involving native species.

Saponins are natural plant metabolites with surface-active and bioactive properties against plant pests, making them promising biopesticides. However, their environmental fate in soil remains unclear. This study investigated the sorption properties of three triterpenoid saponins, two monodesmosidic α-hederin and hederacolchiside A1 saponins, and the bidesmosidic hederacoside C saponin, on common soil constituents including clay minerals (kaolinite, montmorillonite), metal oxides (gibbsite, goethite), black carbon, and topsoil. Batch sorption experiments assessed influences of structures, sorbent properties, and environmental factors. All saponins exhibited unexpectedly strong sorption (distribution coefficient [Kd] > 10³ L/kg on topsoil), with α-hederin showing the highest affinity (Kd = 229 × 10³ L/kg on goethite), attributed to its moderate hydrophobicity (octanol-water partition coefficient, [log Kow] ∼ 4.4), short sugar chain, and interactions involving carboxyl (-COOH) and hydroxyl (-OH) functional groups. In contrast, more polar hederacoside C (log Kow ∼ -1.2) showed weaker sorption with Kd of 1.56 × 10³ to 22.7 × 10³ L/kg. Sorption isotherms followed Freundlich behavior and increased by approximately 50% at acidic pH for α-hederin and hederacolchiside A1 due to protonation of carboxylic acid groups (acid dissociation constant, pKa ≈ 4.7-4.9), whereas hederacoside C lacking carboxylic acid groups remained unaffected. Salts and fulvic acid reduced α-hederin sorption (up to 80%), likely due to ion exchange and competitive complexation. Desorption studies showed α-hederin was strongly retained (<20% desorption), particularly on metal oxides. Scenario-based modeling indicates that at realistic saponin biopesticide doses (50 µM), α-hederin and hederacolchiside A1 remain largely immobile, whereas hederacoside C may slightly leach in low-sorption soils. These findings highlight the combined role of saponin structure and soil mineralogy in regulating environmental mobility with implications for biopesticide design and risk assessment.

Earthworm risk assessment for chemicals is normally based on toxicity tests performed in artificial test soils with either 5% or 10% organic matter. Soil characteristics, in particular organic matter content and pH, influence the bioavailability of chemicals, and one would therefore expect different levels of toxicity in natural soils. Predicting toxicity in different soils is a major challenge. Here we demonstrate a novel approach for predicting effect concentrations in untested soils by using the results of a toxicity test in a standard test soil together with a previously published empirical model for uptake of chemicals into earthworms. The model predicts the uptake and elimination rate constants of a one-compartment toxicokinetic model based on earthworm species properties (lipid content and specific surface area), topological polar surface area of the molecule, and the organic matter content and pH of the soil. The accuracy of the currently proposed model for predicting toxic effect concentrations (EC50 and LC50) was evaluated against an independent dataset, including 145 measured effect concentrations in non-standard soils, covering 30 synthetic organic compounds and 5 earthworm species. The model showed a high accuracy with 90% of predictions within a factor of 3 of observations. We show the current bias in European risk assessment related to differences in organic matter content between standardized test soils and common agricultural soils and demonstrate how application of the new approach removes that bias. An example with two fungicides illustrates how the model could be applied to increase the environmental realism of the risk assessment.

Per- and polyfluoroalkyl substances (PFAS) are man-made chemicals found in all environmental compartments. In surface waters, PFAS can bind to suspended solids (SS), which can affect their fate. In the present study, sorption of 22 PFAS to SS from 16 locations in the Netherlands was quantified, using monitoring data from the Dutch Ministry of Infrastructure and Water Management. A total of 2280 to 3105 (number depending on the data inclusion criterion) SS-water distribution coefficients (K  ss-w) were calculated, assuming equilibrium conditions, though these may not have applied to all locations, e.g.,, due to local discharges. Significant differences were observed between location-specific K  ss-w values. These could not be explained from SS or water characteristics, including the SS organic carbon content, which has previously been assumed to control PFAS sorption to SS. However, for about half the PFAS studied, an inverse relationship between logK  ss-w and the PFAS concentration in water was observed. This may suggest that sorption of (these) PFAS to SS is a nonlinear process, whereas in previous reports it has been considered concentration-independent. Location-averaged K  ss-w values varied between approximately 100 and 10,000 and increased with the number of PFAS carbon atoms, although the values for perfluorocarboxylic acids with <8 carbon atoms were statistically indistinguishable. These values and patterns are consistent with several previous reports from Asia and France. Using the K  ss-w values derived here, PFAS concentrations in SS could be estimated from measured PFAS concentrations in water within an average factor of 2. Therefore, the added value of analytical PFAS concentration determinations in SS in the Netherlands seems limited, also because PFAS masses associated with SS carried by the major rivers generally appeared to be negligible compared to the masses dissolved in water. Consequently, including SS as partitioning phase in PFAS fate models does not seem essential for north-European rivers.