Microplastics (MPs) are recognized as a ubiquitous contaminant in terrestrial ecosystems. Earthworms, which play key roles in soil structure, nutrient cycling, and ecosystem function, are important bioindicators for assessing MP exposure and fate. However, uncertainties remain regarding MP toxicokinetics in earthworms, including ingestion dynamics, retention, and the potential for translocation across the gut epithelium. This study investigated the movement and fate of MPs in Eisenia fetida by quantifying uptake and elimination across five common MP morphologies (films, fibers, foams, fragments, and spheres) and by using synchrotron-based microcomputed tomography (SR-µCT) to visualize internal distributions of 5 to 22 µm glass microspheres and 45 to 53 µm polyethylene microspheres. Across 21-day exposure and depuration phases, earthworms rapidly ingested all MP morphologies, reaching steady state before Day 10 for most types, and efficiently eliminated MPs once removed from spiked soils. Elimination rate constants (1.27-2.34 day-1) corresponded to short half-lives (<1 day), and bioaccumulation factors were consistently low (0.023-0.058), indicating limited retention relative to soil concentrations. The SR-µCT imaging provided high-resolution 3D confirmation that MPs remained entirely confined to the gastrointestinal tract, with none of the 2,779 detected particles ranging from 5 to 53 µm crossing the gut epithelium. Despite higher MP densities in earthworms exposed to smaller glass microspheres, this pattern reflected differences in ingestion rather than tissue penetration. Reduced gut-to-worm volume ratios in polyethylene-exposed worms suggested decreased feeding or avoidance behavior toward the polyethylene microspheres. Overall, these results demonstrate that E. fetida rapidly ingest and eliminate MPs without tissue translocation, and that their gut contents provide a reliable short-term snapshot of MP availability in soil.

Soil-nesting insects are exposed to soil drench pesticides via several routes of exposure, including through contact with the soil matrix. To date, only ∼20% of insecticide toxicity studies have investigated the impacts of insecticide exposure on nontarget insects. Our study aims to address these gaps by creating a novel method for laboratory rearing and ecotoxicological testing using a native, agriculturally common North American soil-nesting ant, Lasius neoniger. We developed a novel soil bioassay method that tests both the acute and chronic effects of exposure to the neonicotinoid insecticide imidacloprid resulting from a soil drench applied to a sandy-loam soil commonly found in southern Ontario farms, to whole colonies of a soil-dwelling eusocial insect, L. neoniger. This method could be applicable to a wide range of different pesticides, as a reliable, replicable, cost-effective tool for assessing contact toxicity in soil-dwelling insect ecotoxicology research. Our laboratory results show that soil drench applications of imidacloprid at levels below 0.06% (0.02202 μg/ml) of recommended application concentrations have deleterious sublethal or lethal impacts on L. neoniger. These impacts, following the soil drench application of imidacloprid, included significant reductions in motor function and soil excavation, and increased levels of queen and worker mortality.

Biosolids have been identified as a major source of microplastics (MP) to the environment. While they have been heavily studied, the impacts biosolids have following their amendment to agricultural soils on the MP content of these soils is poorly understood. Eleven biosolid-amended and nine non-amended agricultural fields in Southern Ontario were sampled to compare the MP content between them. Biosolid-amended fields averaged 2441.82 ± 268.03 MP kg-1, while non-amended fields averaged 775 ± 50.97 MP kg-1. Additionally, MP abundance was correlated with the type of biosolid applied, with fields that received a single application of dewatered biosolids averaging 2412.14 ± 174.81 MP kg-1, whereas fields that received a single application of liquid biosolids averaged 1689.83 ± 225.81 MP kg-1. However, differences in MP abundance were primarily dictated by differences in application rate between dewatered and liquid biosolids. In addition to increasing overall MP content, biosolid amendments influenced MP composition. Biosolid amendment increased soil fibre content, as biosolids are rich in textile fibres derived from the laundering process. As a result, biosolid-amended soils primarily contained polyester, while unamended soils primarily contained polypropylene. Quantifying and characterizing MP content in biosolid-amended fields, and understanding how it differs from unamended fields, is crucial for accurately assessing the risks microplastics pose to terrestrial ecosystems.

Abstract Fungal infections are a major global health challenge, with current antifungal therapies limited by toxicity, cost, and resistance. For Cryptococcus neoformans , key virulence factors that initiate and sustain infection are regulated by fungal peptidases to produce a polysaccharide capsule, promote immune evasion, and support antifungal resistance. These peptidases represent promising targets for antivirulent therapeutic strategies. Here, we developed a computational pipeline to predict and design peptide- and protein-based inhibitors against cryptococcal peptidases. Specifically, we targeted three virulence-associated peptidases: Rim13 (cysteine), May1 (aspartic), and CnMpr1 (metallo). Cysteine peptidase inhibition decreased capsule/cell size ratios without impeding fungal growth and reduced fungal survival within macrophages. Similarly, aspartic peptidase inhibition enhanced fungal clearance within alveolar macrophages and disrupted biofilm formation with additive effects towards fluconazole susceptibility in resistant strains. Additionally, metallopeptidase inhibition through catalytic zinc chelation and blocked substrate binding led to enhanced enzymatic inhibition and reduced in vitro blood-brain barrier crossing. Moreover, an in vivo larval model assessing inhibitor efficacy produced additive effects with fluconazole and lacked host cell cytotoxicity and fungicidal properties, reinforcing anti-virulence mechanisms and therapeutic potential while limiting the evolution of resistance. Further, global proteome profiling of inhibitor treated cells defined a mechanism of cell wall disruption, impeding fungal virulence. Taken together, the designed peptidase inhibitors exhibited potent antifungal activity without harming mammalian cells, establishing a predictive framework for rational scaffold design of next-generation antifungals that disarm the pathogen enabling immune-mediated clearance.

Microplastics (MPs) are recognized as ubiquitous contaminants in terrestrial ecosystems, yet their ecological risks to soil invertebrates remain poorly categorized, particularly at environmentally relevant exposure levels. This study investigated avoidance behavior, ingestion, and toxicity of four common MP polymers (polyethylene, polypropylene, polyester/poly(ethylene terephthalate), and polyacrylamide) in the earthworm Eisenia fetida using particle-based exposure concentrations. Standardized avoidance, reproduction, and ingestion assays were conducted across a wide concentration range (1,000-1,000,000 MP/kg dry soil) under controlled laboratory conditions. Avoidance responses were weak and highly variable across all polymers, with no consistent concentration-dependent patterns observed. Survival exceeded 90% in all treatments, and reproductive output showed no clear concentration-response relationship, with juvenile production at the highest exposure levels not differing from controls. Microplastic ingestion was minimal at lower exposure concentrations, with sporadic detections occurring across polymers, but MPs across the polymers were detectable above similar threshold concentrations (∼80,800-92,800 MP/kg). Above these thresholds, ingestion increased predictably with log-transformed exposure concentration, showing comparable post-threshold ingestion patterns across polymers. Estimated bioaccumulation factors, calculated at a standardized exposure concentration of 1,000,000 MP/kg, were low (0.0042-0.0124), indicating limited internal accumulation of MPs over the 28-day exposure period. Collectively, these results suggest that Eisenia fetida does not actively avoid MP-contaminated soils and does not retain MPs to a significant extent under the conditions tested. By integrating behavioral, ingestion, and toxicity endpoints and reporting exposure in particle-based units, this study provides ecologically relevant insights into MP-earthworm interactions and contributes to improving terrestrial MP risk assessment frameworks.

Abstract Background The tire additive N-(1,3-dimethylbutyl)-Nʹ-phenyl-p-phenylenediamine (6PPD) is widely produced in large volumes as a rubber antidegradant. This chemical can be released into the environment throughout the lifecycle of rubber products. Recently, 6PPD has become the subject of regulatory interest in some jurisdictions due to its widespread environmental occurrence and the acute toxicity of its transformation product N-(1,3-dimethylbutyl)-Nʹ-phenyl-p-phenylenediamine-quinone (6PPDQ) to some salmonids. As research advances for these emerging contaminants, it is critical to understand whether 6PPD and 6PPDQ concentrations in the environment are high enough to pose a risk to living organisms. Here, we present a protocol to conduct two linked systematic evidence maps related to (1) the occurrence of 6PPD and 6PPDQ in the environment and (2) the effects of 6PPD and 6PPDQ on living organisms. Our objective is to collate information on quantification methods, occurrence data, studied species, and toxicity endpoints. This work will contribute to synthesizing a rapidly expanding body of literature and providing insight into knowledge gaps to direct future work. Methods The systematic maps will be developed in accordance with the Collaboration for Environmental Evidence Guidelines and Standards for Evidence Synthesis in Environmental Management. A unified search strategy using chemical names, acronyms, identifiers, and trade names for 6PPD and 6PPDQ will be used for both maps. Searches will be conducted in seven databases, and grey literature will be sourced from key websites and Advisory Board input. Search results will be managed in a reference management software and screened at the title/abstract and full-text levels against predefined eligibility criteria based on the Population-Outcome and Population-Exposure-Comparison-Outcome framework for Map 1 and Map 2, respectively. A decision tree designed a priori will guide concurrent screening to determine article eligibility for either or both maps. For all eligible articles, bibliographic and study-specific data will be coded and entered into a searchable database. Both article screening and data coding will be completed by two independent reviewers. Two systematic evidence maps will summarize the evidence base using narrative synthesis, figures, and tables.

Microplastic (MP) ubiquity has led to their detection in many filter feeding organisms in aquatic environments. Interaction of MPs with filter feeding marine bivalves is known to vary with particle morphology, yet temporal dynamics, organ-specific retention and egestion patterns remain poorly characterized in freshwater bivalve species. We exposed the adult freshwater unionid mussel Megalonaias nervosa (washboard) to 150,000 MP/mL of 6 μm polystyrene (PS) spheres and 61 μm polyester (PES) fibers to determine ingestion and egestion patterns, and how these may differ between MPs. Accumulation dynamics differed markedly between particle types; PS sphere concentrations in mussel organs remained stable throughout the MP exposure period, while PES fibers increased logarithmically as time progressed. Presence of PS spheres was associated with each organ examined after only one day of exposure, while PES fibers were not detected in the gills and gonad until the third day of exposure. Counts of PS spheres in organs followed a ranking of digestive gland > gonad > gills > hemolymph > foot, while PES fiber counts ranked as digestive gland > gills > foot > gonad > hemolymph. The digestive gland was the primary site of MP accumulation, with counts being at least 60 times greater than any other organ examined. After 48 hr, M. nervosa depurated PES fibers more efficiently than PS spheres as indicated by the continuous egestion of PES, but not PS, throughout the 7-day MP exposure. Further, the feces and pseudofeces produced by M. nervosa when exposed to PES fibers was significantly higher in organic matter content. Adult M. nervosa in this study exhibited significantly different ingestion and egestion patterns according to different MP types. This suggests that MP characteristics influence availability and translocation into non-digestive organs, highlighting the importance of studying multiple particle types when considering the accumulation and depuration of MPs in filter feeding organisms.

Freshwater mussels, one of the most imperiled groups globally, are very sensitive to sodium chloride. Long-term water quality monitoring indicates wild freshwater mussels, including Species at Risk, may be at risk of salt toxicity. Elevated water hardness reduces the toxicity of salt to biota including early life stage mussels. However, the response of mussels to salt and road salt alternatives in ion-dilute waters remained unknown. Standard methods were used to assess the acute salt sensitivity of freshwater mussel larvae (glochidia) in reconstituted waters of varying hardness (8.5-290 mg CaCO3/L). Lampsilis fasciola (Wavyrayed lampmussel) and Lampsilis siliquoidea (Fatmucket) glochidia were exposed to sodium chloride, with nominal chloride concentrations between 5 and 5000 mg Cl-/L depending on water hardness. Viability (ability to close valves), a survival surrogate, was assessed after 24 and 48 hr of exposure. Increasing water hardness resulted in reduced salt toxicity, up to a point (170-190 mg CaCO3/L) after which no further amelioration was observed. Lampsilis fasciola 48-hr EC50s ranged from 17.9 mg Cl-/L in very soft water (8.5 mg CaCO3/L) to 389.4 mg Cl-/L in hard water (172.5 mg CaCO3/L). L. siliquoidea 48-hr EC50s ranged from 13.7 mg Cl-/L in very soft water (16.5 mg CaCO3/L) to 221.8 mg Cl-/L in hard water (193.0 mg CaCO3/L). In exposures with a brine and beet-juice containing road salt alternative (Fusion 2300), L. siliquoidea was more sensitive in very soft water (13.1 mg CaCO3/L) than in harder waters (≥50 mg CaCO3/L), with 48-hr EC50s of 0.002% and 0.0055-0.0073% v/v, respectively. Acute chloride EC50s of both species, including one Species at Risk, were less than the long-term chloride Water Quality Guideline in very soft water (<30 mg CaCO3/L).

Effective control of invasive sea lamprey (Petromyzon marinus) populations relies heavily on lampricides, but few studies have investigated the impacts of granular Bayluscide® (gB) on benthic-dwelling organisms. Native freshwater mussels are present in many similar habitats that larval sea lamprey prefer, making them susceptible to nontarget effects. The active ingredient of gB, niclosamide, was derived specifically as a molluscicide; therefore, it is crucial to understand its impacts on a group of mollusks that have been imperiled due to many factors including the input of contaminants in the aquatic environment. Two early life stages of Lampsilis siliquoidea were tested in 7-day exposures to gB. Mortality was significant in both sub-adult and newly metamorphosed mussels, with the latter being significantly sensitive to gB applications that were less than 1% of the suggested application rate. A significant decrease in mussel growth was seen at 0.78% of the suggested application rate. A 24-hr test was supplemented due to gB potency, revealing a similar median lethal concentration of 0.67% (0.55-0.79) of the suggested gB application rate. Additionally, an 8-hr exposure of 0.78% of the application revealed significant effects after only 2 hr of exposure. Both early life stages of L. siliquoidea showed a marked sensitivity to gB. Although environmental conditions may have an influence on gB fate, the marked sensitivity of early life stages demonstrated in this study is crucial to understanding the effects of sustained gB application on the population dynamics of freshwater mussels.

Accurate characterization of pesticide exposure is critical for assessing risks to aquatic ecosystems. However, pesticide concentrations in surface waters are highly variable and often missed by traditional grab sampling methods, which typically fail to capture transient peaks and hydrophobic compounds that partition into non-water matrices. Time-integrated monitoring approaches, such as biofilm sampling using periphytometers, offer a promising alternative. Despite this, uncertainties remain about how biofilm processing methods affect pesticide quantification, and whether replicate periphytometers are necessary to improve monitoring accuracy. To address these questions, water and biofilm samples were collected from six stream sites in southern Ontario. Biofilm samples were split and processed using either freeze-drying or centrifugation to evaluate the effect of sample preparation on pesticide detection. All samples were analyzed for approximately 500 pesticides. Freeze-dried biofilm consistently yielded higher pesticide detection frequencies and concentrations compared to centrifuged samples, indicating that freeze-drying is a more effective processing method for capturing pesticide residues in biofilm. These findings highlight the importance of standardizing biofilm processing methods to improve monitoring reliability. To evaluate the need for replication, six periphytometers were deployed in parallel at a single stream site. Biofilm samples from each replicate were analyzed for pesticide presence. Pesticide detection profiles were highly consistent across replicates (p > 0.05) in two separate sampling events, suggesting that a single periphytometer is sufficient to characterize site-level pesticide exposure at our stream site. Together, these results provide guidance for improving pesticide monitoring programs by recommending freeze-drying for biofilm processing and supporting the continued use of single periphytometer deployments, which are more feasible for routine monitoring without compromising data quality.

Although not assessed in standard ecotoxicological tests, exposure to a toxicant that does not result in an observable adverse effect in the parents may lead to transgenerational effects. These are adverse effects observed in unexposed offspring as a result of their parents' exposure to a toxicant. The goal of this study was to investigate whether transgenerational effects are observed in freshwater snails exposed to a toxicant. Using copper (Cu) as a reference toxicant, this study investigated whether the magnitude of exposure to the parents of the freshwater snail Planorbella pilsbryi resulted in a change in sensitivity of juvenile snails to a subsequent aqueous exposure of Cu. This study also investigated whether transgenerational effects observed in juvenile snails born to exposed parents would change if the parents laid eggs after being given time to recover from their exposure to Cu. Juvenile snails born to parents that were exposed to Cu without being given time to recover had no change in their sensitivity to Cu exposure or in some cases they became less sensitive. This study also observed that when parents were given time to recover from the Cu exposure, juvenile snails tended to be more sensitive to a subsequent Cu exposure, that is, decrease in median lethal concentrations for juveniles with an increase adult exposure. This study demonstrates that exposure of parent snails to a toxicant does not necessarily result in a consistent and significant change in sensitivity of the offspring to the same toxicant.

Exposure to a toxicant has an energetic cost to an organism due to the need for metabolism and excretion of the contaminant, along with repair of any damage at the cellular or tissue level due to the toxicant. The energetic cost of survival upon exposure to a toxicant may result in complete inhibition of reproduction or a reduction in energetic resources available for developing embryos. This study investigated whether exposure of mature adult freshwater snails to copper resulted in a measurable energetic cost to the individuals. Survival, egg mass production, total antioxidant capacity, metallothionein, glycogen, protein, lipid, total energy available, electron transport system, and cellular energy allocation were measured to evaluate the energetic cost of exposure to copper. Survival was not affected by exposure to 28.8 µg/L of copper but egg mass production, glycogen, protein, lipid, total energy available, and electron transport system were reduced. A negative relationship between cellular energy allocation and concentration of exposure to copper was observed for the snails, but the relationship was not significant.

Understanding the chronic effects of environmental disasters, such as oil spills, is critical to assessing long-term impacts on marine ecosystems and guiding recovery efforts. We assessed the reproductive potential of adult Manila clams (Venerupis philippinarum) from sites impacted by the Nathan E. Stewart oil spill (Central Coast, British Columbia, Haíɫzaqv Territory, October 2016) to determine if reduced reproductive capacity may be driving a delayed population recovery among the impacted clam populations. Clams from both reference and impacted sites were conditioned under controlled laboratory settings, with reproductive metrics (gonadosomatic index, progression of gamete development, fertilization success, spawning success) showing no significant differences between sites, suggesting that reproductive output in adults is not currently limiting recovery. Adult clams from all sites successfully spawned under controlled laboratory conditions. However, despite successful spawning and fertilization, larval survival was uniformly low across sites; this low survival may be attributable to methodological factors, such as temperature or handling stress rather than direct impacts of the oil spill. Findings suggest factors other than adult reproductive capacity are causing continued delay of population recovery, warranting further investigation.

Urban areas are expanding rapidly and experience diverse and complex contamination of their surface waters. Addressing these issues requires different tools to describe exposures and predict toxicological risk to exposed biota. We surveyed 21 stormwater management ponds in Brampton, Ontario using three types of sampling methods deployed concurrently: time-integrated water sampling, biofilms cultured on artificial substrates, and organic-diffusive gradients in thin films (o-DGT) passive samplers. Our objective was to compare pesticide occurrences and concentrations to inform monitoring in stormwater ponds, which reflect pesticide pollution in urban areas. We detected 82 pesticides across the three sampling matrices, with most detections occurring in o-DGT samplers. The in situ accumulation of pesticides in o-DGTs during deployment and the high analytical sensitivity achieved establishes o-DGTs as excellent tools for capturing the mixtures of pesticides present. Water and biofilm sampling demonstrated that pesticide concentrations available for uptake are relatively low, with most below toxicological thresholds. Yet our results demonstrate that urban areas are subject to a wide range of pesticides, including herbicides, insecticides, and fungicides, and underscores the urgency of research to quantify the risks of chronic exposure to this chemical mixture.

The toxicity of Bisphenol A (BPA) and replacement products Bisphenol F (BPF), Bisphenol S (BPS), and Bisphenol AF (BPAF) was assessed in freshwater snail Planorbella pilsbryi embryos and adults. The chronic toxicity of BPA and BPAF was further characterized in 28-d tests with adult snails, followed by 21-d assessments of hatching and survival of embryos produced at the end of the test (F1 generation). BPAF was the most toxic of the compounds tested, followed by BPA, BPF, and BPS. In the chronic test with BPA, although we observed no significant effects on adult snails, the hatching and survival of juveniles from the F1 generation was affected at the highest concentration (Maximum Acceptable Toxicant Concentration [MATC]: 0.032 mg/L). We did not observe the same differences during exposure to BPAF. Though some overlap existed, effects were observed at concentrations above most reported environmental exposure values. Given that concentrations of alternative products are expected to increase, and in the absence of data on potential effects of mixtures, further research is needed.

Microplastics are discharged by municipal wastewater treatment plants (WWTPs); however, their uptake by filter-feeding freshwater bivalves is poorly understood. This study examined the abundance and characteristics of microplastics in wild bivalves from five locations along a 155km stretch of the Grand River (Ontario, Canada) in 2021-2022, including upstream and downstream of three municipal WWTPs. At each site, fingernail clams (Sphaeriidae spp., n=5 composites), freshwater mussels (Lasmigona costata, n=10; gill, digestive gland, and hemolymph), and surface water (n=3) were sampled at a single timepoint. Microplastics (particles >38 mu m to 5mm) were isolated and visualized via stereomicroscopy, and a subset chemically analyzed using Fourier transform infrared spectroscopy. Fingernail clams contained the highest total blank corrected microparticle counts (35.5 +/- 29.4g(-1) [mean +/- SD]), mussel tissues ranged from 4.3 +/- 4.2mL(-1) in hemolymph to 6.5 +/- 8.1g(-1) in digestive gland, and water contained 5.5 +/- 2.8L(-1). Fibers were the dominant morphology across all samples, most particles were between 80 mu m and 2mm in length and, of those analyzed chemically, 30.0% were a plastic polymer. At sites downstream of WWTP outfalls, elevated counts were only seen in mussel gills and not in other bivalve tissues or water compared with upstream samples. Although microplastics were found across all sites in both biotic and abiotic compartments, results suggest little impact of WWTP discharges on their uptake in downstream bivalves.

The development of standardized toxicity tests is critical for assessing pollutants in aquatic ecosystems. The mayfly Neocloeon triangulifer offers advantages as a test species due to its asexual reproduction, short life cycle, and high sensitivity to pollutants. However, we identified variability in response sensitivity to pollutants, which may stem from the nutritional composition and growth stage of its primary food source, Navicula spp. diatoms. This study aimed to evaluate the repeatability and reproducibility of 96 h toxicity tests to sodium chloride with N. triangulifer fed diatoms of varying ages (target concentrations: 329, 494, 741, 1111, 1666, and 2500 mg/L). We tracked Navicula spp. growth stages under controlled conditions and characterized fatty acid and lipid contents at each stage to assess how these factors influence N. triangulifer sensitivity to sodium chloride, a common reference toxicant. Sensitivity increased significantly as the diatom feed aged, highlighting the need for standardized culturing methods to improve test reliability. This study is the first to simultaneously characterize the growth stages and fatty acid profiles of Navicula spp. diatoms as feed species for N. triangulifer. This work contributes valuable insights to the optimization of standardized toxicity testing with this sensitive aquatic insect.

Fresh produce is an important component of maintaining cognitive and physical health, particularly for children. A mechanism to increase access to fresh produce is the construction of community gardens in urban centres. While reducing barriers to nutritious food, the soil of the community garden can contain contaminants (e.g. metals) depending on the location and how the garden was constructed. This study quantified, for the first time, seven metals (As, Cd, Cr, Cu, Pb, Mn, and Ni) in soil from 83 community gardens across the City of Winnipeg in Manitoba, Canada. Concentrations of metals in soil were used to create distributions for environmental exposure and estimated daily intake, which were then used to determine exceedances of soil quality guidelines and acceptable daily intakes, respectively. Raised garden beds and gardens further from roads had typically lower concentrations of metals in surface gardens and those nearer to roads. While some concentrations of metals exceeded CCME guidelines levels for the protection of environmental health, the vast majority represent a low risk. For human health, only As posed a quantifiable risk of exceeding the USEPA acceptable daily intake via the consumption of produce from gardens, though this was < 1.2% for the whole population and < 10.2% for children aged 1 to 2 years. Overall, this study is the first to show that the concentration of the metals in soil from gardens typically poses a low risk to environmental and human health. We recommend the use of raised gardens to further mitigate risk.

Hyalella azteca is an epibenthic crustacean used in ecotoxicology, but there are challenges associated with standard methods using reproduction as an endpoint. A novel, 28-day reproduction toxicity test method for H. azteca was created to address these issues by initiating tests with sexually mature amphipods to eliminate the confounding effects of growth, using a sex ratio of seven females to three males to reduce reproductive variability, and conducting tests in water-only conditions to make recovery of juveniles easier and expand testing capabilities to water-soluble compounds. In the present study, we evaluated the 28-day novel method by comparing it with the 42-day standard test method in duplicate and parallel water-only, static-renewal exposures to sublethal concentrations of imidacloprid (0.5-8 µg/L). Both methods showed similar effects on survival, with survival approaching 50% in the highest test concentration (8 µg/L). However, the 42-day median effect concentrations (EC50s) for growth were more sensitive in the standard method (1.5-3.2 µg/L) compared with the 28-day EC50s generated by the novel method (>8 µg/L). Reproduction endpoints (juveniles/female) produced similar EC50s between methods, but the data were less variable in novel tests (smaller coefficients of variation); therefore, fewer replicates would be required to detect effects on reproduction compared with the standard method. In addition, novel tests generated 28 days of reproduction data compared with 14 days using standard tests and allowed survival and growth of sexes to be assessed independently. Thus, the novel method shows promise to improve the use of reproduction as an endpoint in water-only toxicity tests with H. azteca. Environ Toxicol Chem 2024;43:723-735. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

With concern growing regarding the impact of microplastics (MPs) on terrestrial ecosystems, it is important to assess the role invertebrates may play in the fate of MPs within these ecosystems. Commonly, MPs enter these environments through improperly discarded waste or the application of treated biosolids and/or wastewater on agricultural soils. The present study investigated whether three species of terrestrial isopod (Porcellio scaber, Porcellio laevis, and Porcellionides pruinosus) ingest plastic debris and generate MPs during exposures varying from 24 h to 14 days and whether this may have an adverse effect on their health. Test vessels were designed to expose isopods to plastic fragments in the form of polyethylene plastic foam. Isopods were exposed to plastic that was either (1) pristine, or (2) weathered in a soil and water solution prior to incorporation in test vessels. When exposed to weathered polyethylene, all three species generated MPs (minimum-maximum size values for all durations inclusive: P. laevis = 114-1673 µm, P. scaber = 99-1635 µm, P. pruinosus = 85-1113 µm) through the consumption of macroplastic fragments with no observed impact on their health. In the shorter-duration exposures, the number of MPs generated by the isopod species in the present study was highly variable between experimental vessels (minimum-maximum generated MPs for 14-day exposure: P. laevis = 25-420, P. scaber = 50-583, P. pruinosus = 48-311). However, as the exposure durations increased, there was a clear trend of increasing MP generation, indicating that the isopods continued to consume the plastic fragments as long as the surface was weathered. A significant difference in the size of generated MPs was observed as well, with smaller isopod species generating smaller MP fragments on average. The results of the present study confirm that certain species of isopod can contribute to the generation of MPs, which constitutes an additional pathway of MP exposure to soil ecosystems. Environ Toxicol Chem 2024;43:784-792. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.