Environmental Toxicology and Chemistry最新文献

Stormwater runoff is a significant source of microplastics (MP) contamination in tributaries. However, the role of drainage infrastructure (e.g. surface drains and pipes) and land use in the transport of MPs into freshwater systems is largely unknown. Here we quantify and compare microplastic concentrations deposited below surface drains and pipe stormwater outfalls in two distinct urban watersheds: one characterized by agricultural and forested land cover, and the other dominated by residential and commercial development. We compared MP morphologies and abundances upstream and downstream of 20 stormwater outfalls to determine the influence of outfall type on MP accumulation. Three surface water and sediment samples were collected at each sampling location, along with measurements of chemical and physical water quality parameters. Microplastics were identified using Nile Red staining, a rapid and effective screening technique suitable for large-scale environmental assessments while minimizing resource-intensive analyses. Fragments were the most abundant MP morphology and were the primary form driving differences in total MP concentrations among the sites. Flow velocity had the greatest impact on plastic concentrations in the sediment, and the accumulation of microplastics in surface water increased as water depth decreased. The highest MP concentrations were found at pipe outfalls in both surface water and sediment compared to surface drains. The watershed with more agricultural and forested landcover had higher MP concentrations downstream of both types of drainage infrastructure compared to the more developed urban watersheds. These findings highlight the importance of considering both land use characteristics and drainage infrastructure when assessing MP input into freshwater systems, providing valuable insights for decision-making on monitoring, retention, and remediation strategies.

Neonicotinoid insecticides pose a risk to aquatic invertebrates through their unique selective mode of action and time-cumulative toxicity. Ecotoxicity threshold values (ETVs) are guideline water concentrations for chemical toxicants, concentrations above which represent an unacceptable risk to aquatic environments. Currently, there are no ETVs for neonicotinoids endorsed for use in Australia, mainly due to a lack of suitable chronic ecotoxicity data. Furthermore, the current method for the conversion of acute to chronic equivalent ecotoxicity data using an acute to chronic ratio (ACR) is inappropriate for use on neonicotinoids due to their time-cumulative toxicity. The aim of this study is to derive chronic ETVs for the protection of 80, 90, 95 and 99% of aquatic species for six neonicotinoids approved for agricultural use in Australia. This is achieved using a novel time-weighted log-log linear regression scaling method for the conversion of acute ecotoxicity data to their 28-day chronic equivalent, coupled with the most recent developments in species sensitivity distributions (SSD) modelling, including model averaging. Ecotoxicity threshold values for six neonicotinoids were derived from compound specific data sets, comprised of 22-44 individual species' ecotoxicity endpoint data. Chronic data made up approx. 29% of the data, the remaining 71% was comprised of 28-day chronic equivalent (ie, acute converted) ecotoxicity data. Aquatic species were most sensitive to thiacloprid (95% ETV = 0.031 μg L-1), acetamiprid (95% ETV = 0.055 μg L-1) and imidacloprid (95% ETV = 0.109 μg L-1), followed by clothianidin (95% ETV = 0.303 μg L-1) and least sensitive to thiamethoxam (95% ETV = 0.566 μg L-1) and dinotefuran (95% ETV = 0.655 μg L-1). Compared to the ACR method of converting the same acute to chronic equivalent ecotoxicity endpoints, the ETVs derived here using the time-weighted 28-day chronic equivalent method were within 40-200% of the ETVs derived using the more traditional ACR approach.

Sunscreen products, essential for photoprotection, introduce organic UV filters into aquatic environments, raising concerns about their ecotoxicological impacts. This study evaluates the sensitivity of seven marine microalgae species spanning diverse taxonomic groups to six organic UV filters (benzophenone-3, butyl methoxydibenzoylmethane, ethylhexyl triazone, homosalate, 2-ethylhexyl salicylate, and octocrylene). Growth rate and chlorophyll a fluorescence were analyzed after 72 h exposures at concentrations of 10, 100, and 1,000 µg/L. Growth rate revealed to be the most sensitive indicator, with significant interspecies variability in response to UV filters. Results revealed that Tisochrysis lutea exhibited better sensitivity compared to the commonly used Phaeodactylum tricornutum, which demonstrated low sensitivity across endpoints. Among UV filters, 2-ethylhexyl salicylate and homosalate were the most toxic, significantly affecting growth and fluorescence in multiple species. Interestingly, growth inhibition often coincided with increased fluorescence, suggesting species-specific compensatory mechanisms. These findings underscore the limitations of relying solely on P. tricornutum in standardized toxicity tests and advocate for the inclusion of sensitive species to improve ecological relevance. Integrating growth and fluorescence metrics in high-throughput assays could advance risk assessment methodologies for emerging contaminants like UV filters.

Our analysis of water samples collected during a rain event from two urban rivers in the Greater Toronto Area, Ontario, Canada indicated that selected transformation products (TPs) of the tire antioxidant, 6PPD, including 6PPD-quinone (6PPDQ) and 4-hydroxydiphenylamine (4-HDPA) were present at concentrations >1 µg/L. In acute (96-h) toxicity tests with aquatic larvae of the mayfly, Neocloeon triangulifer, 6PPDQ did not cause mortalities at the highest test concentration, which was just below the limit of solubility. In toxicity tests with 4-HDPA, a calculated 96-h LC50 of 339 µg/L is above environmentally relevant concentrations. However, in toxicity tests with 6PPD, there was evidence that the degradation of this tire wear compound produced unknown TPs that caused mortalities in exposed mayfly larvae. Additional work could identify other TPs of 6PPD that could be a hazard to aquatic invertebrates exposed to tire wear compounds transported into surface waters from transportation corridors.

Chlorantraniliprole (CHL) is the most widely used diamide worldwide, with South America being its primary market. Despite its growing application, the environmental effects of CHL on non-target organisms, mainly native fish species, remain understudied. In the present study, the sublethal effects of CHL were assessed in Cnesterodon decemmaculatus by acute exposure (96 h) to 1/10 (1.5 mg/L) and 1/100 (0.15 mg/L) of the LC50, using a multi-biomarker approach across different levels of biological organization. Locomotor activity (distance traveled, time immobile, average and maximum speeds), somatic index, enzymatic activities of acetyl-cholinesterase (AChE) in muscle and brain, catalase (CAT) in muscle, brain, gills and liver, glutathione-S-transferase (GST) in gills and liver, aspartate amino-transferase (AST), alanine amino-transferase (ALT), AST/ALT ratio and alkaline phosphatase (ALP) in the liver were measured. The primary effect of exposure was the reduction in locomotor activity, which appears to be more closely related to CHL's mode of action than cholinergic effects. The muscles and brain were the organs most affected by oxidative stress, and adaptive responses involving AChE, CAT, and GST were observed, highlighting the organism's ability to manage oxidative stress. The IBR index indicates a dose-dependent relationship, with individuals exposed to T2 exhibiting more than twice the IBR value of those exposed to T1 and nearly four times that of the control group. Our results indicate that insect-specific compounds like diamides can severely affect non-target species, potentially affecting survival and growth rates in aquatic species, even at sublethal concentrations. For muscle-targeted insecticides, locomotor activity is one of the most effective biomarkers for assessing the impact of exposure. This study represents the first report on the toxicity of a diamide in a native South American model fish, a key bioindicator in assessing ecological health.

Microplastics (MPs) pollution has recently garnered substantial attention worldwide due to their tendency to contaminate ecosystems and transmit toxic substances in the food chain, compromising human health. The primary goal of this study is to provide a level of understanding about the source, occurrence, detection, and potential ecological risk of MPs in Eastern Indian dumping sites in the years 2022 and 2023 as well as representing a scenario encompassing urban, suburban, and rural areas. The MPs concentrations in dumping sites ranged between 10 and 3457 MPs mg/kg. Fragments were the predominant shape in samples from both years, 32% and 36% in 2022 and 2023, respectively. White was the leading color of MPs in both years (34% in 2022, 45% in 2023), followed by grey, blue, green, and others. Based on the chemical analysis, the most common polymers discovered were polyethylene (20%), nylon (15.5%), polyethylene terephthalate (11.62%), and polypropylene (10.28%). Most of the study area has high polymer hazard index (PHI) values (>1000) due to the presence of high-hazard polymers like PVC and PU. According to polymer load index (PLI) values, the samples from English Bazar and river-side dumps are highly contaminated with MPs (PLI: 26 to 49), whereas samples from Manikchak and Old Malda are less contaminated (PLI: 1 for both). The ecological risk index (ERI) values of river-side samples were the highest (ERI: 318950).

Ecotoxicity assessments often struggle with contaminant mixtures. This study explored combining chemical activity of hydrophobic organic contaminants (HOCs) and metals, using zinc as a model. An acute Daphnia magna immobilisation test, with protein content as an additional endpoint, revealed an additive sublethal effect. The findings suggest chemical activity could serve as a unified approach for assessing HOCs and metals together, offering a promising method for more accurate environmental toxicity evaluations.

In indirect exposure tests for non-target arthropods, organisms are exposed to a compound on pre-treated glass plates or leaves to mimic exposure in the field. These tests are difficult to generalise because the effective dose that the organism received is unknown. This is unfortunate as this hampers further interpretation and integration of ecotoxicological tests in general. As proof of principle to show that indirect tests can be integrated with dose driven tests, an indirect test was carried out with honeybees, exposed to Imidacloprid and the results were compared with available more standard chronic oral, acute oral and acute contact test results. The three standard tests were used to calibrate and validate a ToxicoKinetic ToxicoDynamic model to obtain the toxicity parameters that link the dose to effects. Subsequently, the validated parameter set was used to calculate the dose of imidacloprid needed to obtain the effects observed in the indirect exposure test. This exercise showed that the model can be used to calculate the dose in a glass plate test, which implies that any of the tests can be used to predict the outcome of any other test. This is a first step of the development of a 'criss-cross risk assessment model, where both effect endpoints and exposure endpoints, can be combined.' This first step has great potential to use this predictive power to reduce bee testing and non-target arthropod testing in general.

There is a lack of knowledge regarding the mechanisms that induce microplastic fragmentation and degradation within the environment. This research aimed to quantify the combined degradative effects that mechanical abrasion in conjunction with photo-oxidation and hydrolysis, have on polyethylene terephthalate (PET) microplastics. To accomplish this, common routes of degradation were evaluated. Degradation was assessed using three indices indicative of polymer degradation: Carbonyl Index (CI), Carbon-to-Oxygen Index (COI), and Hydroxyl Index (HI). This study assessed the effects that mechanical abrasion (MA), photo-oxidation, and various simulated environmental conditions: aqueous (Aq), aqueous + ultraviolet (UV), and UV only within two distinct settings (lab vs outdoor) have on PET microplastic degradation. Photo-oxidation exposure across a 60-d period induced significant degradation on PET microplastics resulting in a 1-22% increase in carbonyl groups across all treatments except UV and Aq. + UV Chamber (MA). A 6-214% increase in hydroxyl groups across all treatments. A 1-10% decrease in carbon-to-oxygen groups in all treatments except the Chamber Aqueous and Outdoor UV (MA). Mechanical abrasion seemed to accelerate this degradation in combination with both UV and aqueous treatments. Using simulated environmental conditions to induce degradation upon PET microplastics, in both lab and simulated environmentally relevant settings, revealed that the combined effects of hydrolysis and photo-oxidation can accelerate the process, especially in conjunction with mechanical abrasion. The novel findings presented here provide insight into the complex relationship between various polymer degradation pathways and the effects that mechanical abrasion can have on them, while also providing additional data for an understudied yet prevalent plastic polymer.

There has been a history of debate within the ecotoxicological community on the use of point estimates (e.g., effect concentration for 20% of test organisms; EC20) versus effect levels determined through hypothesis-based testing, such as the no observed effect concentration (NOEC) and lowest observed effect concentration (LOEC). This study provides analyses of the percent effect that is expected to occur at the NOEC, LOEC, and maximum acceptable toxicant concentration (MATC) based on available chronic data but does not debate the merits of point estimates versus hypothesis-based test results. We also developed adjustment factors that can be applied to NOECs, LOECs, MATCs, EC20, and EC10 values to equate them to EC5 values, which generally represent an effect level that is within the variability of control responses (e.g., NOEC/Adjustment Factor = Approximate EC5). Our analyses showed median percent effect occurring at the NOEC (8.5%), LOEC (46.5%), and MATC (23.5%) was not strongly influenced by chemical or taxon type (invertebrate vs. vertebrate). The median NOEC, LOEC, and MATC to EC5 adjustment factors were 1.2, 2.5, and 1.8, respectively. The median EC20 to EC5 adjustment factor was 1.7, and the median EC10 to EC5 adjustment factor was 1.3. Adjustment factors were not strongly influenced by chemical or taxon type, suggesting they can be applied across chemicals and taxa. Our results provide context to the use of hypothesis-based testing results. The adjustment factors developed could be considered in efforts to streamline screening-level ecological risk assessments and individual-level endangered species evaluations by providing an approach that could be used to adjust commonly reported toxicity test results (i.e., NOEC, LOEC, MATC, EC20, EC10) into approximate EC5 values.