Environmental Toxicology and Chemistry最新文献

Per- and polyfluoroalkyl substances (PFAS) are environmentally persistent synthetic chemicals with known toxicological effects, including endocrine and developmental disruption. Perfluorooctanesulfonic acid (PFOS), one of the most prevalent PFASs, can enter freshwater ecosystems via runoff and effluents, potentially transferring through food webs to humans. Freshwater pulmonate snails (family: Lymnaeidae) occupy a basal trophic position and may act as both PFOS bioindicators and contaminant vectors. We tested whether Stagnicola elodes snails could detect and behaviorally avoid PFOS at environmentally relevant concentrations using a Y-tube choice assay. Snails were given a choice between control water and PFOS solutions ranging from 4 to 2500 ng/L. Behavioral outcomes were classified as movement toward PFOS, toward control water, or no decision. Avoidance behavior was significant at 300 ng/L when excluding non-decision snails, and at 100, 300, and 400 ng/L when including them. These results suggest that S. elodes can detect PFOS within a narrow concentration range, but behavioral responses are modest and at levels above safe drinking water standards (∼4 ng/L), minimizing both their potential as a strong bioindicator species for PFOS contamination and their ability to limit trophic transport.

Environmental exposure to industrial phenolic compounds poses growing concerns for insect biodiversity and ecosystem health. This study investigates the toxicological and physiological effects of 2,6-dimethylphenol (2,6-DMP), a widely used phenolic pollutant, in Galleria mellonella (the greater wax moth), a species of ecological importance and a major pest associated with honeybee colonies. Topical application of 2,6-DMP resulted in significant larval mortality (median lethal dose = 3.77 µg/mg body wt), while adults displayed reduced sensitivity, suggesting stage-dependent toxicodynamics. In vivo assays revealed immunotoxic effects, including hemocyte deformation, decreased viability, and marked depletion of cuticular free fatty acids critical for maintaining the insect's barrier function. Supporting in vitro experiments confirmed dose-dependent cytotoxicity in insect hemocytes and Sf9 cell lines, likely due to membrane disruption. Given the ecological association of G. mellonella with honeybee colonies, our results provide context for evaluating potential risks of phenolic contaminants within agricultural systems. Moreover, phenolic compounds such as 2,6-dimethylphenol are known to affect aquatic invertebrates, and the mechanisms identified here may contribute to understanding their broader ecological impact.

Polystyrene microplastics and nanoplastics, which are commonly detected in agricultural runoff, often occur in the presence of agricultural pesticides. However, there is limited mechanistic understanding of the fate of these pesticides in relation to the presence of these plastic surfaces. Here, we used molecular dynamics simulations to investigate the adsorption mechanisms of four common triazole fungicides-flusilazole, hexaconazole, myclobutanil, and triadimenol-on polystyrene nanoplastics, with and without dissolved natural organic matter. In the absence of organic matter coating, simulated adsorption of the fungicide compounds on the polystyrene surface was driven primarily by van der Waals interactions, which were correlated with the hydrophobicity of the compounds and the polarity of their associated functional groups. Accordingly, flusilazole and hexaconazole exhibited both the highest hydrophobicity, as characterized by octanol-water coefficients and the most favorable interaction energies on the polystyrene nanoplastics in the molecular simulations. Consistent with these theoretical results, subsequent adsorption experiments revealed two-fold higher adsorbed amount of flusilazole on polystyrene plastics, compared to myclobutanil and triadimenol. When the model polystyrene nanoplastics were coated with representative plant-derived organic matter compounds in the molecular simulations, the interaction energy of the fungicides was decreased by 150% due to the hydrophilic nature of the organic matter-plastic interface that was unfavorable to the binding of the fungicides. However, this theoretical prediction was not corroborated by adsorption experiments with a river-isolated dissolved natural organic matter, likely due to insufficient coating or relatively weak interactions of the organic matter components on the PS surface. We highlight the importance of considering the role of natural organic matter of different chemistries in relation to the environmental fate of fungicides with nanoplastics.

In the environment, organisms are exposed to a combination of fluctuating environmental conditions as well as anthropogenic toxicants such as pesticides. Fluctuations in temperature can affect the tolerance of terrestrial arthropods to toxicants, but far less is known of drought-influenced changes in the responses to toxicant exposure. Here, we compare mortality responses to drought under two optimal temperatures following prior pesticide exposure in two species of springtails (Collembola); the drought-susceptible Folsomia quadrioculata and the drought-tolerant Hypogastrura viatica. Two Arctic and two temperate populations from each species were exposed to three sub-lethal concentrations of the neonicotinoid imidacloprid (0.01-0.5-0.1 mg/kg dry soil) at 15 °C for 14 days, followed by different levels of drought stress (100-85% relative humidity [RH]) at 15 or 20 °C, and survival was assessed. Drought tolerance of all populations from both species at both temperatures was reduced by imidacloprid in a concentration-related manner. Temperate populations of H. viatica subjected to a drought stress of 98%RH showed an increase in mortality with increasing imidacloprid concentration of approximately 40% compared to a mortality increase of approximately 20% in the Arctic populations. This difference was less pronounced in F. quadrioculata, with an increase in mortality of approximately 50% in both temperate and Arctic populations at a drought stress of 98% RH. Drought stress at 20 °C further increased mortality with approximately 20% in the drought-tolerant H. viatica from both climatic regions. Thus, local adaptations and species identity should be considered when assessing the effects of combined stressors.

A critical element for understanding measured concentrations and predicting exposure levels of UV filters (UVFs) in recreational waters relates to mass released from sunscreen products applied to skin during swimming and bathing. A probabilistic mass transfer kinetic model was developed to estimate distributions of the mass of five organic UVFs released during individual swim events with sunscreen. The model incorporates the ratios of different demographics and distributions of their total skin areas, adjusted to account for body areas to which sunscreens are not typically applied or do not contact water. The resulting distribution of skin areas is combined with distributions of sunscreen application rates and UVF levels in sunscreen products to generate a distribution of UVF masses on skin that are exposed to water with the fraction released to water calculated using a first-order equation describing the kinetics of release. The predicted median mass released during a swim event was 112 mg for oxybenzone, 32.6 mg for avobenzone, 23.5 mg for octocrylene, 47.7 mg for homosalate and 7.59 mg for octisalate. As proof of principle, the model was used to repeat previous modelling at Prophète Beach, which resulted in predicted median values for oxybenzone and avobenzone within a factor of three of the reported measured environmental concentrations.

Alternative approaches to traditional animal testing are being promoted to support regulatory chemical risk assessments for environment and human health. The Organisation for Economic Development (OECD) has validated some in vitro test methods, but these methods are often suitable only for mono-constituent chemicals with a limited range of physicochemical properties. Most in vitro test methods are not suitable for poorly soluble, (semi)volatile, or multi-constituent chemical substances without significant methodological adaptations. In particular, substance of Unknown or Variable composition, Complex reaction products or Biological materials (UVCBs), including hydrocarbon UVCBs and petroleum substances (PS), can pose serious challenges for in vitro (eco)toxicity testing due to their complexity and variable chemical compositions. The choice of dosing method will depend on the purpose of the test as well as the physicochemical properties of the test substance. It remains difficult to establish and maintain stable exposures of PS in in vitro test systems due to different factors, including (1) the high surface area to volume ratios of multi-well plates that promotes sorption, (2) the open test wells that allow (semi)volatile constituents to escape or contaminate neighbouring plate wells, (3) the difficulty to analytically confirm exposure in small testing volumes and (4) the presence of lipids and proteins in biological media which bind PS constituents. This review maps the currently used dosing methods for hydrophobic and/or (semi)volatile chemicals and UVCBs in in vitro tests for environment and human health hazard assessments and outlines approaches and modifications to overcome various testing challenges associated with these test substances. Finally, research gaps are identified and recommendations made for future development of in vitro assays for UVCBs.

Exposure of fish early life stages to polycyclic aromatic hydrocarbons (PAHs) causes negative impacts on development of teleost fish, which can be exacerbated by rising global temperatures. This study investigated the combined effects of exposure to oil water accommodated fractions from the spill that affected the Brazilian northeast and rising temperatures on early development of the zebrafish Danio rerio. Exposure to PAHs caused developmental delay and increased frequency of malformations at 16.47 and 32.95 μg-∑PAHt L-1 at 28 °C, 30 °C, and 32 °C. Incomplete mandible development was not verified after PAH exposure at 28 °C but increased with increasing temperatures. Increased frequency of malformations included thrombosis, deformed heart, pericardial and yolk-sac edemas and spinal kyphosis. Heart rates increased with increasing temperature in control larvae and with increasing PAH concentrations at 28 °C and 30 °C, but not at 32 °C. Total length, eye and swim bladder area of larvae at 168 hr post-fertilization (hpf) decreased with increasing PAH concentrations and increasing temperatures, indicating an additive interaction. Acetylcholinesterase (AChE) activity in control larvae increased with increasing temperatures and decreased with increasing PAH concentrations. Combined exposure to PAHs and temperature elevation intensified developmental delays and teratogenic outcomes, posing additional threats to the viability of Danio rerio early life stages. Results indicate that temperature effects should be considered in oil spill risk assessments under climate change scenarios.

Globally, there has been a push for the development of new approach methods that refine, reduce, and replace animal use in toxicity testing. A large source of this animal use is whole-effluent toxicity testing, which is widely employed in regulation to determine the toxicity of effluents. The rainbow trout acute lethality test is one of the most widely used in North America for this purpose, as it empirically and irrefutably demonstrates effluent toxicity. Despite its strengths, this test is an ideal candidate for replacement due to its frequent use. One replacement is the RTgill-W1 assay, which uses a rainbow trout gill cell line to assess the toxicity of effluent samples. Despite its promise, the RTgill-W1 assay has rarely been investigated for its potential in replacing the rainbow trout acute lethality test. This study assessed the toxicity of pulp and paper mill effluents using the RTgill-W1 assay. Sixty-two effluents were sourced from 3 separate mills with a total of 5 unique sampling locations; an additional 8 effluents were created by mixing effluents together. Of the 70 effluents, 50 were assessed with both the rainbow trout acute lethality test and the RTgill-W1 assay. Twenty of these caused >50% mortality to the rainbow trout and >50% decline in cell viability. An additional 3 effluents caused a >50% decline in cell viability. In effluents causing >50% mortality and a decline in cell viability, there was a strong correlation in toxicity (r = 0.786, p <0.001). The alamarBlue endpoint was more sensitive in filtered effluents (p <0.001). The effluent matrix did not influence the test endpoints, but NH3 was observed to cause significant vacuolation of the cells. Overall, these results are promising for the implementation of the RTgill-W1 assay as a replacement to the rainbow trout acute lethality test for pulp mill effluents.

Freshwater bodies worldwide are experiencing salinization, often with severe ecological consequences. An underexplored topic in freshwater salinization research is the potential for waterbodies to stratify their incoming salty water (due to its higher density) and the effects this stratification may have on freshwater organisms. We conducted a mesocosm experiment to test whether salt stratification can occur in small freshwater bodies and its ecological consequences. We created salt-stratified mesocosms by piping salty water down to the bottom of a 1200-L mesocosm and examined the duration of the created stratification. We discovered that salt stratification in mesocosms can last for several weeks. We then compared the habitat selection and survival of two species of freshwater snails (the native pouch snail, Physa acuta, and invasive banded mystery snail, Viviparus georgianus) when exposed to the presence or absence of salt stratification, crossed with the presence or absence of predation cues (i.e.,, crushed conspecifics). Mystery snails preferred the bottom habitats, regardless of the presence of salt or predator cues, and consequently suffered near total mortality in the salt stratified mesocosms (97% survival without salt vs. 3% survival with). In contrast, the pouch snails reduced their use of the bottom habitat in response to both stratified salt and predator cues While they still suffered mortality in the salt-stratified mesocosms, it was much less than the mystery snails. (82% survival without salt vs. 47% survival with salt). These results suggest that the stratification of salt pollution in freshwater bodies can persist for prolonged periods and differentially affect freshwater species as a result of their habitat preferences.

The phenolic compound 3-trifluoromethyl-4'-nitrophenol (TFM) is used as a lampricide, applied to rivers and streams to control populations of invasive sea lamprey (Petromyzon marinus) in the Great Lakes. 3-Trifluoromethyl-4'-nitrophenol is used to selectively target larval sea lamprey because of their limited capacity to detoxify it. The tissue TFM accumulation impairs mitochondrial adenosine triphosphate production by uncoupling oxidative phosphorylation, leading to energy depletion and death. Sea lamprey tolerance to TFM is greater in the summer, but the underlying mechanism(s) are unresolved. The present study tested the hypothesis that an increased capacity of sea lamprey to eliminate TFM at warmer temperatures increases their tolerance to TFM. Acute toxicity tests demonstrated that the 12-hr median lethal concentration (LC50) of TFM steadily increased by approximately 1.5-fold as water temperature rose from 7 to 28 °C. When lamprey were acclimated to one of three temperatures (6, 12, 24 °C) and exposed to an identical TFM concentration (i.e., 12-hr LC25 at 12 °C), muscle and liver TFM concentrations were approximately 30% and 36% lower in lamprey acclimated to 24 °C, suggesting more effective elimination of TFM at warmer temperatures. Calculations of the TFM steady state concentration and elimination half-life (t1/2) in the liver and muscle following TFM exposure suggested that they have a greater capacity to eliminate TFM in warmer water. We propose that the sea lamprey's capacity to detoxify TFM is greater at higher temperatures, preventing internal concentrations from reaching lethal levels during acute (9-12 hr) TFM exposure of similar duration to field applications. We also propose that water temperature, in addition to water pH and alkalinity, be considered when determining TFM application concentration used to optimize sea lamprey treatment effectiveness.