Quality Criteria for Microplastic Effect Studies in the Context of Risk Assessment: A Critical Review

Dynamic process of UV-aging polystyrene microplastics, simultaneous adsorption of drugs, and subsequently coagulative removal together

The aging of plastics and their adsorptive interactions with the residual contaminants in water has attracted increasing attentions. In this study, the dynamic process of UV-aging polystyrene (PS) microplastics (MPs) were semi-quantitatively analyzed using a coulter counter, and the adsorptive interactions between the aged PS MPs and two popular drugs[norfloxacin (NOR) and chloroquine phosphate (CQ)] were investigated simultaneously. The MPs presented a rapid size downtrend, reduced from micrometer to nanometer, and the particle number concentration increased about 2 -3 times after a 36.0 h aging effect. The apparent UV-aging process of PS MPs mainly obeyed the pseudo-first order kinetic model in currently measured MPs' size range. The drug uptakes of the aged MPs were fully consistent with the contents of oxygen-containing groups on MPs surface rather than MPs' size. The involved adsorption mechanisms were investigated in detail mainly including electrostatic attraction, hydrogen bonding, and π-π electron donor-acceptor interaction. The drug adsorbed MPs were subsequently efficiently removed by an enhanced coagulation together owing to the synergistic effects of the two pollutants. This study provides a novel and comprehensive perspective on the fundamental understanding the UV-aging process of MPs and the simultaneous adsorption behaviors, furthermore, a strategy was proposed for their collaborative removal.

Cellular and tissue-level responses of mussels (Mytilus edulis) to aged polyethylene terephthalate (PET) micro- and nanoplastic particles

Micro- and nanoplastic particles (MNPs) are pollutants of global concern due to their persistence, ubiquity, and associated risks. Laboratory studies, however, have predominantly focused on pristine MNPs, which do not adequately reflect the characteristics of environmental plastic debris. To address this gap, this study investigated the cellular and tissue-level responses of mussels (Mytilus edulis) to aged polyethylene terephthalate (PET) MNPs (diameter 600 nm to 3.1 µm) at three environmentally relevant concentrations: 10, 103, and 105 particles/L. The particles' physicochemical characteristics and stability in exposure media were analyzed using a combination of advanced analytical techniques. The biological responses were analyzed across multiple effect endpoints during both the exposure (days 1, 3, 7, and 14) and the subsequent recovery periods (3 and 10 days post-exposure), via flow cytometry and histopathology. The results revealed the sensitivity of hemocyte subpopulations, including granulocytes and hyalinocytes, to aged PET MNPs. Concentration- and time-dependent changes in lysosomal stability, oxidative activity, and hemocyte mortality were observed, demonstrating both immediate cellular perturbations and recovery potential to alleviate particle-induced effects. Histopathological analysis of key tissues exhibited significant alterations, particularly in the gill, suggesting potential impairment of essential physiological functions. No mussel mortality or significant changes in growth metrics were observed under the tested experimental conditions. These findings underscore the systemic impacts across multiple tissues of aged MNP exposure and highlight the importance of adopting integrative, environmentally realistic approaches to assess the biological consequences in future research.

Water environmental capacity of estuarine microplastics capped by species sensitivity threshold

Estuaries are biologically rich ecosystems and act as aggregation zones for microplastic (MP) during their transport from rivers to the sea, posing heightened ecological risks compared to other aquatic environments. However, limit criteria for MP discharge to guide risk management remain lacking. This study quantified the water environmental capacity (WEC) of estuarine MPs using species health-based microplastic concentration (MPC) thresholds. Classified MPs simulation employed probability density functions and shape factors to convert mass concentrations into particle counts during the flood season in the Yangtze River estuary. The 5 % species hazard concentration (HC5) with two ecologically relevant metrics was selected as the MPC threshold by correcting the species sensitivity distribution (SSD) curves for polydispersity and biological accessibility of environmental MPs. Lastly, the dynamic WEC framework was established by linking MP simulations to MPC thresholds. MP aggregation hotspots were found in the intertidal zone and maximum turbidity zone in southern branch, which is akin to locating the 'shortest plank' in bucket effect. The average rescaled MPC in hotspots reached 4.77 × 105particles/(d·m3), accounting for 14.38 % of the WEC safety threshold. This framework explored scientific basis for quantifying the MPs carrying capacity of estuarine ecosystems and allocation of plastic discharge rights.

Acute and partial life-cycle toxicity of a tri-polymer blend of microplastics in the copepod Acartia tonsa

Microplastics are a prolific environmental contaminant that pose a risk to marine organisms. Ecotoxicological studies have identified microplastics can cause sub-lethal harm to aquatic biota. However, prior studies often lack comparability and environmental relevance, for example focussing upon monodisperse beads at extremely high concentrations. Copepods are keystone marine taxa that play vital roles in the marine food web and biogeochemical cycling. In this study, we adapted ISO methods to conduct acute and partial life-cycle toxicity tests exposing adult and juvenile life stages of the copepod Acartia tonsa to a fully characterised tri-polymer microplastic blend comprising cryoground polyethylene, polypropylene, and nylon particles (5-100 μm) at concentrations ranging 0-1000 μg L-1. The tests considered the toxicity of microplastics on a wide number of endpoints including adult survival, algal ingestion rates, egg production and size, larval development ratio and juvenile survival. Mortality, egg size and larval development ratio proved to be the most sensitive endpoints. The tri-polymer blend had an LC5072h value of 182 μg L-1 providing a baseline for future toxicity testing using this method.

Characterization of tire and road wear particles in experimental biota samples

There is a growing interest in the development of reliable analytical methods for characterizing tire and road wear particles (TRWP). The current research extends the use of single particle analysis techniques to various experimental biota samples. TRWP and cryogenically milled tire tread (CMTT) were identified using a weight of evidence framework including density separation, optical microscopy, and chemical mapping (scanning electron microscopy coupled with energy dispersive X-ray spectroscopy). Our techniques successfully identified CMTT particles in laboratory earthworms exposed to soil spiked with CMTT. A river biota sample (bivalves) collected from the Seine with no detectable TRWP was spiked with road dust containing TRWP. Particle identification was performed after a biota digestion protocol and density separation of particles > 1.5 g/cm3 and < 2.2 g/cm3 which resulted in sufficient TRWP for identification and characterization. The average TRWP particle size from the road dust spiked biota sample was 126 μm by number and 220 μm by volume (range: 9 -572 μm). The size distribution overlay of TRWP identified from spiked biota were consistent with TRWP identified from the original road dust sample suggesting that the current method for biota digestion, dual density separation, and TRWP characterization is feasible for similar samples.

Investigating the co-transport and combined toxicity effect of micro-/nano-plastics and PAHs in ryegrass

The potential for micro-/nano-plastics (MNPs) to translocate from environmental matrices into organisms has been increasingly substantiated. However, the mechanisms underlying the co-transport and combined toxicity of MNPs in conjunction with organic pollutants in organisms remain inadequately understood. This study investigated the transport mechanisms and toxicity responses of ryegrass (Lolium perenne L.) to the co-existence of MNPs and polycyclic aromatic hydrocarbons (PAHs) through hydroponic experiments. Laser confocal characterization and flow cytometry quantification revealed that, under combined exposure, MNPs larger than 30 μm were rarely able to enter ryegrass roots, whereas those ranging from 0.1 to 10 μm were not only absorbed by the roots but also translocated to the shoots. Quantitative analysis of the contaminants in ryegrass revealed that the presence of MNPs significantly reduced the effective concentration of PAHs in the hydroponic solution, thereby decreasing the content of PAHs within the plant tissues. A significant negative Spearman correlation (rs = -0.56, p < 0.05) between the translocation factors (TFs) of MNPs and phenanthrene (Phe), suggesting a potential competitive inhibition mechanism during the translocation of MNPs and PAHs within plants. This competitive inhibition in translocation of PAHs within ryegrass was found to be more pronounced with decreasing particle size of MNP (rs = 0.76, p < 0.05). An integrated biomarker response (IBR) analysis, encompassing plant biomass, photosynthetic pigments, and antioxidant enzymes, revealed that the inhibition of co-existing MNPs on the uptake and translocation of PAHs by plants alleviated the phytotoxicity of PAHs, with the extent of alleviation depending on the exposure duration and particle size of the MNPs.

Evaluation of phenotypic and behavioral toxicity of micro- and nano-plastic polystyrene particles in larval zebrafish (Danio rerio)

Plastic particles have been found in all environments and it is necessary to understand the risks these particles pose in, and to, the environment. The objectives of this work were to understand the toxic effects of varying size and concentration of polystyrene (PS) micro- and nano-plastics in zebrafish embryos and their fate within the larvae. In this work, larval zebrafish (Danio rerio) were exposed to six sizes (0.05, 0.25, 0.53, 2.1, 6.02, and 10.2 µm diameter) and concentrations (0.0005 to 0.2 µg/µL) of PS micro/nanoplastics particles. The zebrafish embryo toxicity (ZET) and the general and behavioral toxicity (GBT) assays were used to determine particle toxicity in embryos. Behavioral analysis was performed and micro/nanoplastics uptake and organ distribution were assessed. Phenotypic and behavioral toxicity was observed in all exposures with the exception of 0.25 µm particle-exposed larvae. Significant phenotypic toxicity was seen at the highest tested exposure concentration, with some sizes showing potential recovery as time increased in the assay. Behavioral analysis demonstrated a decrease in baseline activity across all micro- and nano-plastic sizes. Significant increases in light-dark responses were recorded in ZET assays of smaller-sized particles and no significant effects were observed at larger sizes. Significant decreases in this response were reported in the GBT assays of all tested sizes with the exception of the 0.05-µm particles. These assays demonstrate the general, developmental, and neurotoxicity of micro/nanoplastics to a model organism, which can be used to infer individual and population-level effects of exposure.

The shifting baseline of microplastic measurement: A comparison of methodologies used in estuarine-based studies and guideline recommendations

Microplastics are a ubiquitous contaminant of estuarine environments, threatening ecological health. However, the comparison and interpretation of data from microplastic studies is challenged by inconsistency in methods of detection and analysis. This study reviews the methods reported in historical estuarine-based microplastic studies and compares them with current guideline recommendations to identify aspects that need improvement. Our analysis was undertaken on a database of 175 studies conducted across 36 countries between 2013 and 2023. We show that the majority of database studies (71 %) use suitable identification methods; however, fewer studies report recommended analytical representation (47 %) and analytical proportions (40 %). Only 30 % of the studies in our database utilised methods that align with all current recommendations. We further examined the use of density separation methods, used to separate microplastics from sediment samples and found only a low proportion of these studies (8 %) adhered to current guideline recommendations. Our findings indicate that there has been little improvement in the methods used in historical estuarine-based studies over the last 10 years. This demonstrates the need for greater focus on considering and reporting analytical representation and proportions in future work to ensure microplastic prevalence is accurately measured.

Addressing data gaps in deriving aquatic life ambient water quality criteria for contaminants of emerging concern: Challenges and the potential of in silico methods

The international community is becoming increasingly aware of the threats posed by contaminants of emerging concern (CECs) for ecological security. Aquatic life ambient water quality criteria (WQC) are essential for the formulation of risk prevention and control strategies for pollutants by regulatory agencies. Accordingly, we systematically evaluated the current status of WQC development for typical CECs through literature review. The results revealed substantial disparities in the WQC for the same chemical, with the coefficients of variation for all CECs exceeding 0.3. The reliance on low-quality data, high-uncertainty derivation methods, and limited species diversity highlights a substantial data gap. Newly developed in silico methods, with potential to predict the toxicity of untested chemicals, species, and conditions, were classified and integrated into a traditional WQC derivation framework to address the data gap for CECs. However, several challenges remain before such methods can achieve widespread acceptance. These include unstable model performance, the inability to predict chronic toxicity, undefined model applicability, difficulties in specifying toxicity effects and predicting toxicity for certain key species. Future research should prioritize: 1) improving model accuracy by developing specialized models trained with relevant, chemical-specific data or integrating chemical-related features into interspecies models; 2) enhancing species generalizability by developing multispecies models; 3) facilitating the derivation of environmentally relevant WQC by incorporating condition-related features into models; and 4) improving the regulatory acceptability of in silico methods by evaluating the reliability of "black-box" models.

Revealing Microplastic risks in stratified water columns of the East China Sea offshore

Microplastics have been proven to impact a broad range of marine species significantly. This study investigated the vertical distribution characteristics of microplastics (MPs) to verify their potential toxicity, distribution patterns, and affecting probability on organisms offshore of the East China Sea (ECS), China. Significant variations in MP characteristics across stratified water layers were identified and corroborated through artificial neural network (ANN) analysis. By a combination of species sensitivity distribution (SSD), risk quotient (RQ) and joint probability curves (JPC) method, this study gave the regional risk thresholds and current risk distributions. Based on SSD, the derived predicted no-effect concentration for the ecosystem was 52.0 items/L (95 % confidence interval: 13.7-262.8 items/L), with the 5 % species hazardous concentration at 103.6 items/L. The RQ assessment results indicated varying ecological risk levels across different water layers, with the highest risks transitioning from north to south and from surface to bottom layers. Most sites exhibited a moderate risk level, with the highest risks identified in surface water near the Yangtze River Estuary, China. Conversely, the JPC analysis suggested a minimal ecological risk across the study area, emphasizing variable ecological risk contingent on species presence. This study underscores the importance of examining surface and intermediate water layers for marine habitats and organisms, highlighting the necessity of prioritizing investigations into the distribution of MPs across different water layers in the ECS, particularly focusing on buoyant polyester fibers present in the upper water column and the layers beneath the offshore surface.

Using artificial intelligence tools for data quality evaluation in the context of microplastic human health risk assessments

Concerns about the negative impacts of microplastics on human health are increasing in society, while exposure and risk assessments require high-quality, reliable data. Although quality assurance and -control (QA/QC) frameworks exist to evaluate the reliability of data for these purposes, manually assessing studies is too time-consuming and prone to inconsistencies due to semantic ambiguities and evaluator bias. The rapid growth of microplastic studies makes manually screening relevant data practically unfeasible. This study explores the potential of artificial intelligence (AI), specifically large language models (LLMs) such as OpenAI's ChatGPT and Google's Gemini, to streamline and standardize the QA/QC screening of data in microplastics research. We developed specific prompts based on previously published QA/QC criteria for the analysis of microplastics in drinking water and its sources, and used these to instruct AI tools to evaluate 73 studies published between 2011 and 2024. Our approach demonstrated the effectiveness of AI in extracting relevant information, interpreting the reliability of studies, and replicating human assessments. The findings indicate that AI-assisted assessments show promise in improving speed, consistency and applicability in QA/QC tasks, as well as in ranking studies or datasets based on their suitability for exposure and risk assessments. This groundbreaking application of LLMs in the environmental sciences suggests that AI can play a vital role in harmonizing microplastics risk assessments within regulatory frameworks and demonstrates how to meet the demands of an increasingly data-intensive application domain.

A brief history of microplastics effect testing: Guidance and prospect

Numerous reviews have consistently highlighted the shortcomings of studies evaluating the effects of microplastics (MP), with many of the issues identified in 2016 still relevant in 2024. Here, we summarize the current knowledge on MP effect testing, compare guidelines, and provide an overview of risk assessments conducted at both single species and community levels. We discuss standard test materials, MP characteristics, and mechanisms explaining effects. We have observed that the quality of MP effect studies is gradually improving, and knowledge on enhancing these studies is available. Recommendations include data rescaling and alignment for ecological risk assessment, with preference for using environmentally relevant MPs. A step-by-step protocol for creating polydisperse test materials is provided. Most risk assessments indicate that concentrations observed in ecosystems globally exceed the effect thresholds measured in the laboratory. However, using a higher-tier approach, no risks are expected for freshwater benthic communities at current MP exposure concentrations. Evidence on the mechanisms behind adverse effects is growing; however, more well-designed experiments are needed. A potential solution might involve comparing natural particles with MPs that are as similar in dimensions as possible, providing insight into the mechanisms of food dilution where volume is a critical determinant of toxicity.

Acute toxicity of natural and synthetic clothing fibers towards Daphnia magna: Influence of fiber type and morphology

Environmental consequences of plastic pollution have come under scrutiny over the past 20 years as stewardship of the biosphere has risen in popularity. Microplastic research has focused on fragmented particles from hard plastics with limited research focused on microfibers released from textiles, which constitute a significant portion of microplastics in aquatic environments. The present study investigated hazards associated with two natural microfibers (cotton and silk) and four synthetic microfibers (acrylonitrile, Kevlar, nylon, and polyester) towards Daphnia magna. Results demonstrated that toxicity is dependent on the polymer type and morphology. Natural microfibers had no significant effects on D. magna whereas nylon microfibers were acutely toxic. While the total number of microfibers in exposure chambers contributed to microfiber ingestion and toxicity, suspended microfibers were weakly correlated to microfiber ingestion and toxicity. Microfibers with smoother surfaces were more toxic than microfibers that were frayed. Toxicity was more strongly related to microfiber ingestion than exposure concentration, suggesting that microfiber uptake is an important measurement endpoint for characterizing effects. Research with longer exposure times and emphasis on endpoints other than survival, such as uptake and retention of microfibers, feeding rates, growth and development, and reproduction are needed to understand the ecotoxicity of microfibers.

Towards harmonized ecotoxicological effect assessment of micro- and nanoplastics in aquatic systems

Micro- and nanoplastics are globally important environmental pollutants. Although research in this field is continuously improving, there are a number of uncertainties, inconsistencies and methodological challenges in the effect assessment of micro- and nanoparticles in freshwater systems. The current understanding of adverse effects is partly biased by the use of non-relevant particle types, unsuitable test setups and environmentally unrealistic dose metrics, which does not take into account realistic processes in particle uptake and consequent effects. Here we summarize the current state of the art by compiling the most recent research with the aim to highlight research gaps and further necessary steps towards more harmonized testing systems. In particular, ecotoxicological scenarios need to mirror environmentally realistic particle diversity and bioavailability. Harmonized test setups should include different uptake pathways, exposures and comparisons with natural reference particles. Effect assessments need to differentiate direct physical particle effects, such as lesions and toxicity caused by the polymer, from indirect effects, such as alterations of ambient environmental conditions by leaching, change of turbidity, food dilution and organisms' behavior. Implementation of these suggestions can contribute to harmonization and more effective, evidence-based assessments of the ecotoxicological effects of micro- and nanoplastics.

Species sensitivity distributions of microplastics based on toxicity endpoints and particle characteristics: Implications of assessing ecological risk in Tai Lake

The prevalence of microplastics (MPs) in Tai Lake poses significant environmental concerns; however, research on MPs' ecological risk assessment is limited. To advance our understanding of MPs' toxicity in Tai Lake, species sensitivity distributions (SSDs) were used to evaluate how organisms respond to different MPs properties and endpoints in Tai Lake. A total of 102 data points were categorized and utilized in SSD estimation. It was found that the hazardous concentration for 5% of species (HC5) for MPs is 237.98 (26.89-2.59 × 103) particles/L in Tai Lake. In terms of endpoints, the HC5 follows the descending order: reproduction 1.03 × 103 (16.30-6.05 × 103) > growth 153.36 (11.37-2.53 × 103) > mortality 67.60 (4.55-4.29 × 103) particles/L. It was found that fibers and polyvinyl chloride (PVC) exhibit the most adverse effects among the MPs' shapes and types assessed. Among size fractions, 100-1000 μm exhibited higher toxicity to Tai Lake biota compared to 1-10 and 10-100 μm. The ecological risk assessment suggested that the likelihood of ecological risk from MPs in Tai Lake is higher for fibers and PVC. Notably, fish species were identified as the most sensitive species in Tai Lake compared to crustaceans and mollusks. This research leads to a better insight into the physical characteristics and toxicity endpoints of MPs in determining their toxicity for estimating SSDs in aquatic environments. Moreover, it highlights the importance of implementing effective management strategies to address the negative impacts of MPs in Tai Lake.

Microplastics versus natural mineral particles. How to create and test them while maintaining environmental relevance

Whether microplastics cause different effects than inert natural particles, and how to create relevant testing materials, are key questions in microplastics research. We prepared Environmentally Relevant Microplastic (ERMP) and Mineral Microparticle (ERMS) mixtures with similar levels of polydispersity and tested their 28-day chronic effects on the reproduction and growth of L. variegatus at two different organic matter (OM) contents (average and enriched). Additionally L. variegatus was exposed to ERMP and ERMS to study the particle egestion for 14 days. We observed no differences in growth or reproduction between ERMP and ERMS at particle concentrations of up to 10 % (v/v). In contrast, organisms exposed to enriched OM content increased their growth with 30 % and increased reproduction with 20 %. For ERMP with an enriched OM content, reproduction was reduced with an effect threshold EC50 of 13.68 ± 5.54 % (v/v). After 14 days of exposure to 5 % ERMP, the egestion of faecal pellets was higher compared to exposure to 5 % ERMS, suggesting that in order to acquire the same amount of nutrition, L. variegatus is spending more energy. With this study, we demonstrate that refinements in the manufacturing of environmentally diverse particle mixtures can contribute to a more realistic testing of particle effects.

Paint: a ubiquitous yet disregarded piece of the microplastics puzzle

Microplastics are widespread pollutants. Microplastics generated from the wear and tear of paints and coatings have recently been modeled to be a large source of microplastics to the environment. Yet, studies focused on microplastics broadly frequently overlook paint microplastics. In this article, we systematically reviewed the primary literature (turning up 53 relevant articles) on paint microplastic sources, identification methods, environmental concentrations, and toxicity to model organisms. Examples of sources of paint microplastics include paints from buildings and murals, crafts and hobbies, cars and roads, marine boats and structures, and industrial systems like pipes, sewers, and other infrastructure. Paint microplastics have been quantified in several marine samples from Europe and, to a lesser extent, East Asia. Reported concentrations of paint microplastics are up to 290,000 particles per kilogram of sediments, with the greatest concentration reported near a graffiti wall. Out of the toxicity studies testing paint microplastics, there have been 68 tested effects in total across all endpoints and organisms and 17 quantified lethal concentration 50% doses (ranging from 0.001 to 20 g/L). Of the tested effects, 45 observed endpoint values in the paint treatment were significantly different from the control (66%)-most of which were tests using antifouling paints. Overall, the number of studies on paint microplastics is small, limiting a holistic understanding of microplastics. Based on our synthesis of the state of the science on paint microplastics, we suggest a research agenda moving forward informed by research gaps.

Contribution of chemical toxicity to the overall toxicity of microplastic particles: A review

Nanoplastics and microplastics are of growing research interest due to their persistence in the environment and potential harm to organisms through physical damage, such as abrasions or blockages, and chemical harm from leached additives and contaminants. Despite extensive research, a clear distinction between the physical and chemical toxicity of plastic particles has been lacking. This study addresses this gap by reviewing studies examining both toxicity types, focusing on environmentally relevant leachates. The chemicals used in plastics manufacturing, which number over 16,000, include additives, processing aids, and monomers, many of which pose potential hazards due to their toxicity, persistence, and bioaccumulation. Studies typically use extraction or leaching methods to assess chemical toxicity, with leaching more closely mimicking environmental conditions. Factors influencing leaching include plastic type, particle size, and environmental conditions. A systematic literature search identified 35 relevant studies that assessed the toxicity of plastic particle suspensions and their leachates. Analysis revealed that, in 52 % of the cases, both the suspension and leachate had toxic effects, while in 35 % of the cases, toxicity was attributed to the suspension alone. At 13 %, only the leachate was toxic. This suggests that leachates contribute significantly to overall toxicity. However, the results vary widely depending on the experimental conditions and plastic type, highlighting the complexity of microplastic toxicity. The preparation methods used for leachates significantly influence toxicity results. Factors such as leaching time, particle size, and separation techniques affect the concentration and presence of toxic chemicals. Additionally, washed particles-those subjected to procedures for removing leachable chemicals-often showed reduced toxicity, although the results varied. This underscores the need for standardized methods to compare studies better and understand the relative contributions of physical and chemical toxicity to microplastic pollution.

A new holistic perspective to assess the ecological risk of microplastics: A case study in Baiyangdian Basin, China

By integrating probabilistic ecological risk assessment with the overall risk index method, which considers the multidimensional characteristics of the microplastome, the ecological risks of microplastic pollution were assessed more comprehensively. This study took the Baiyangdian Basin as an example to address the limitations of current risk assessment methods that rely on concentration data or the individual risk of microplastics. Using an exponential regression model, the acute and chronic ecological risk thresholds for the overall risk index method were determined to be 0.43 and 0.30, respectively. The acute and chronic ecological risks of the microplastome occupied 61 % and 79 % of the Baiyangdian Wetland and 0 % and 14 % of the Fu River, while the Xiaoyi River did not exhibit risk during the rainy season. Results indicated that intense human activities, poor hydrodynamics, low settling velocity and high levels of environmental chemical pollutants jointly contributed to the high risk of the microplastome in water bodies. Compared with the probabilistic ecological risk assessment method (risk characterization ratio), there was a significant difference in the area of acute and chronic ecological risks caused by the microplastome in the Baiyangdian Basin when using the overall risk index method. This proved that considering only concentration cannot truly reflect the toxicity of microplastics to aquatic organisms.

Microplastic pollution in marine sediments of the Antarctic coastal environment of Potter Cove and nearby areas (25 de Mayo/King George Island, South Shetlands)

Plastic contamination in the Southern Ocean is a growing issue. This study provides the first comprehensive analysis of marine microplastics (MPs) (0.1-5 mm) in surface sediments in Potter Cove and nearby areas around Argentina's Carlini station (25 de Mayo/King George Island, South Shetlands). Sediment samples from 31 sites (2020-2022) were collected to examine whether MP pollution originates from station activities or ocean currents. All samples contained MPs, averaging 0.18 ± 0.12 MPs/g of sediment, mainly microfibers (MFs) and irregular microfragments (MFRs) (0.11-6.23 mm) and irregular microfragments (MFRs) (0.09-4.57 mm). Infrared spectroscopy identified 13 polymer types, including cellulosic materials, polyester, and polyamide, with most MPs < 1 mm, showing aging signs, similar to laundry wear. This widespread distribution suggests contamination may stem from both local activities and external sources. Findings underscore the urgent need for MP pollution management and further research to identify sources and develop effective mitigation strategies.

Quantifying Effects and Ingestion of Several Pristine Microplastics in Two Early Life Stages of Freshwater Mussels

Microplastics have been found in freshwater systems, and in turn have been detected in freshwater bivalves. However, there is limited research that defines the toxicity of bicroplastics to native freshwater bivalves that have long been imperiled in North America. Our objective was to determine whether a suite of pristine microplastics has an adverse effect on two early life stages of unionid freshwater mussels. Glochidia of Lampsilis fasciola (a Canadian species at risk) and Lampsilis siliquoidea (widespread across Canada) were individually exposed to spheres of polystyrene (6 and 90 μm), polyethylene (28, 90, and 1000 μm), and cellulose acetate (1000 μm), as well as fibers of polyethylene terephthalate (60 μm). After 24 h, there was no significant decrease in glochidia viability in either species. Juvenile L. siliquoidea mussels were also exposed to spheres of polystyrene (6 and 90 μm) and polyethylene (28 μm), and fibers of polyethylene terephthalate (60 μm) in individual 28-day subchronic tests followed by a 7-day depuration period. Burial was assessed weekly, and ingestion of each microplastic was compared in nondepurated and depurated mussels. There was no sustained effect on juvenile burial with any microplastic tested. Ingestion of microplastics was concentration dependent, and depuration occurred for all particles and size ranges tested. The results suggest that pristine microplastics were not acutely toxic to the early life stages of these freshwater mussels, but that the energetic costs associated with particle uptake and depuration, which were not measured in our study, may have an impact on fitness that warrants further investigation. In addition, testing with other shapes and polymers of microplastics typically detected in the environment is recommended. Environ Toxicol Chem 2024;43:2557-2568. © 2024 The Author(s). Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Museum-archived myctophids reveal decadal trends in microplastic and microfiber ingestion

Global plastic production has surged since the 1960s, resulting in the pervasive presence of microplastics in the environment, yet there is a substantial gap in understanding historical trends of plastic pollution in wildlife. Recent discoveries of significant microplastic contamination in fishes have sparked considerable contemporary advancements in analytical methods and hold the potential to fill gaps in historical trends. We measured the presence of microplastics in museum-archived myctophids (Stenobrachius leucopsarus, Diaphus theta, and Tarletonbeania crenularis) collected from 1962 to 2016, to determine if trends in contamination levels over time correspond with the rise in plastics production. Seventy particles were extracted from 57 of the 240 individuals (23.8 % average occurrence across the time series) consisting of primarily blue and black microfibers. Anthropogenically modified cellulose was the dominant material (87 %) identified through μFTIR analysis, with polypropylene and polyethylene particles occurring secondarily. Although the complete time series across a broad geographical range of the North Pacific did not reveal a significant temporal trend, myctophids collected in proximity to the U.S. west coast showed a trend towards increasing incidence of microplastic and microfiber ingestion over time (p ≤ 0.05). Using historical samples of species with higher ingestion levels and consistent collection locations would improve the reliability of future investigations.

Towards a risk assessment framework for micro- and nanoplastic particles for human health

BACKGROUND

Human exposure to micro- and nanoplastic particles (MNPs) is inevitable but human health risk assessment remains challenging for several reasons. MNPs are complex mixtures of particles derived from different polymer types, which may contain plenty of additives and/or contaminants. MNPs cover broad size distributions and often have irregular shapes and morphologies. Moreover, several of their properties change over time due to aging/ weathering. Case-by-case assessment of each MNP type does not seem feasible, more straightforward methodologies are needed. However, conceptual approaches for human health risk assessment are rare, reliable methods for exposure and hazard assessment are largely missing, and meaningful data is scarce.

METHODS

Here we reviewed the state-of-the-art concerning risk assessment of chemicals with a specific focus on polymers as well as on (nano-)particles and fibres. For this purpose, we broadly screened relevant knowledge including guidance documents, standards, scientific publications, publicly available reports. We identified several suitable concepts such as: (i) polymers of low concern (PLC), (ii) poorly soluble low toxicity particles (PSLT) and (iii) fibre pathogenicity paradigm (FPP). We also aimed to identify promising methods, which may serve as a reasonable starting point for a test strategy.

RESULTS AND CONCLUSION

Here, we propose a state-of-the-art modular risk assessment framework for MNPs, focusing primarily on inhalation as a key exposure route for humans that combines several integrated approaches to testing and assessment (IATAs). The framework starts with basic physicochemical characterisation (step 1), followed by assessing the potential for inhalative exposure (step 2) and includes several modules for toxicological assessment (step 3). We provide guidance on how to apply the framework and suggest suitable methods for characterization of physicochemical properties, exposure and hazard assessment. We put special emphasis on new approach methodologies (NAMs) and included grouping, where adequate. The framework has been improved in several iterative cycles by taking into account expert feedback and is currently being tested in several case studies. Overall, it can be regarded as an important step forward to tackle human health risk assessment.

The Global Spread of Microplastics: Contamination in Mussels, Clams, and Crustaceans from World Markets

Analysis of microplastic (MP) occurrence in commercially relevant species is a prerequisite for food risk assessment. Using a standardized methodology, we aimed to investigate MP contamination in point-of-sale clams, mussels, and Crustacea shellfish collected from various markets (Belgium, Croatia, Serbia, and South Korea). An improved digestion protocol yielded ≥ 99.8% digestion efficiency for all species analyzed. In a total of 190 samples analyzed individually by microFTIR, MPs were identified in 43.68% of the samples with less than 1 MP/individual average (0-4 MP/individual, 0-1.35 MPs/g tissue). Significant differences between species were observed when considering samples contaminated with MPs, with Crustacea shellfish having the lowest MPs/g of edible tissue. Polystyrene, polypropylene, and polyethylene were dominant MPs found in clams and mussels, while polyamide, polyethylene terephthalate, and polyvinyl chloride were the most abundant in Crustacea shellfish. Our data do not support the bioaccumulation or biomagnification of MPs with the size of the animal in the shellfish group. MP contamination is more strongly associated with the type of shellfish than with the geographical origin of the market.

Impact of weathered and virgin polyethylene terephthalate (PET) micro- and nanoplastics on growth dynamics and the production of extracellular polymeric substances (EPS) of microalgae

The ever-increasing plastic waste accumulation in the marine environment necessitates a deeper understanding of microalgae interactions with micro- and nanoplastics (MNP), and the role of extracellular polymeric substances (EPS). EPS, known for its adhesive properties and produced as an algal stress response, may facilitate aggregation of both algae and MNPs, thereby impacting ecological and hydrodynamic processes such as the trophic transfer or vertical transport of MNPs. Moreover, gaining a deeper understanding of the impact of weathering processes on the potential toxicological effects of plastic particles, and the comparative significance of plastic-specific effects relative to those of naturally occurring particles such as kaolin clay, is imperative. Therefore, this study investigated the impact of fragmented, polydisperse virgin polyethylene terephthalate (PET, Daverage = 910 nm) and weathered PET (Daverage = 1700 nm) on the growth and the production of EPS of Rhodomonas salina. Algae were exposed to a range of low MNP concentrations (10, 100 and 1000 and 10,000 MNPs ml-1) for 11 days. A natural particle control (kaolin, Daverage = 1600 nm) was deployed to differentiate particle effects from plastic effects. It was observed that exposure to both weathered PET and virgin PET resulted in initially increased growth rates (7.80 % and 7.28 % respectively), followed by significant decreases in algae cell density (-30.1 % and -11.2 % respectively). Furthermore, exposure to weathered PET caused a simultaneous elevation in cellular EPS production (76.51 %). The effects of plastics were significantly larger than the effect of kaolin. Also, the observed effects were amplified by the weathering of the plastics. These observations underscore the interactions between particle type, age and concentration, and their distinct impacts on algae density and growth inhibition. The observations indicate a role for EPS as an algal protection mechanism, potentially affecting the environmental fate of MNP - microalgae aggregates.

Accumulation, depuration, and potential effects of environmentally representative microplastics towards Daphnia magna

Microplastic risk assessment often characterizes primary plastics, plastics intentionally manufactured at the micro- and nanoscale, or plastics collected within the natural environment, which often lack repeatability and the volume necessary for reliable hazard characterization. There is limited understanding of how environmentally representative plastics prepared at the microscale impact aquatic organisms. The aim of the present study was to create environmentally representative microplastics and characterize their toxicokinetics and hazards. Plastic cups and forks were micronized to <120 μm particles and Daphnia magna were exposed for 48 h at concentrations ranging from 0.01 mg/L to 100 mg/L. Uptake and depuration experiments were conducted at the highest concentration where accumulation was confirmed. Raman spectroscopy identified that both plastics were polystyrene and had similar size distributions. Microplastics were not acutely toxic but accumulated and rapidly depurated. Toxicokinetics demonstrated that cup MPs were consumed at higher rates than fork MPs despite similar physical characteristics. Daphnia magna preferentially selected smaller particles from the heterogenous suspensions. Future research will need to further explore the relationship between physicochemical properties, particularly size, and ecotoxicity. The study focused on mortality as the primary hazard endpoint. However alternative, sublethal biomarkers may be more appropriate in describing the effects of microplastic exposure.

Interactive effects of nanoplastics, multi-contaminants, and environmental conditions on prairie aquatic ecosystems: A factorial composite toxicity analysis within a Canadian context

Limited data exist on the interactions between nanoplastics (NPs) and co-contaminants under diverse environmental conditions. Herein, a factorial composite toxicity analysis approach (FCTA) was developed to analyze the time-dependent composite effects of NPs (0 ∼ 60 mg/L), copper (Cu, 0.2 ∼ 6 mg/L) and phenanthrene (PHE, 0.001 ∼ 1 mg/L) on microalgae under diverse pH (6.7 ∼ 9.1), dissolved organic matter (DOM, 1.5 ∼ 25.1 mg/L), salinity (1 ∼ 417 mg/L) and temperature (23 ∼ 33 °C) within the Canadian prairie context. The toxic mechanism was revealed by multiple toxic endpoints. The combined toxicity of NPs, Cu and PHE within prairie aquatic ecosystems was assessed by the developed FCTA-multivariate regression model. Contrary to individual effects, NPs exhibited a promotional effect on microalgae growth under complex environmental conditions. Although Cu and PHE were more hazardous, NPs mitigated their single toxicity. Environmental conditions and exposure times significantly influenced the main effects and interactions of NPs, Cu and PHE. The synergistic effect of NPs*Cu and NPs*PHE on microalgae growth became antagonistic with increased pH or DOM. Microalgae in the Souris River, Saskatchewan, were projected to suffer the most toxic effects. Our findings have significant implications for the risk management of NPs.

Cytotoxicity assessment of HDPE microplastic on Tetrahymena thermophila (Protozoa, Ciliate): Assuring quality and FAIR data

Microplastics is recognized as an emerging pollutant and adapting and harmonizing existing test methods is essential to advancing research. The aim of our work was to provide a case study on how to ensure quality and FAIR data in the assessment of microplastic hazards with the unicellular organism Tetrahymena thermophila (Protozoa, Ciliata). We selected high density polyethylene (HDPE) microplastics as a model material. In the study design we followed the quality criteria recommended for studies on particle effects, specifically emphasizing the reporting of experimental design and data. Our experimental work was based on ISO 4988 (2022) multigeneration tests with T. thermophila that was upgraded with additional cytotoxicity tests (protocols have been made available on Zenodo). In addition, we used microscopy to inspect material-organism interaction. The results show that 24 h exposure of T. thermophila to HDPE microparticles did not induce changes in metabolic activity, viability, or proliferation up to exposure concentration 100 mg/L. Microscopy analyses confirmed ingestion of the test material but no adsorption of HDPE particles to the cell surfaces confirming that HDPE microplastics present a low hazard to T. thermophila. To maximize the impact of the generated data, we made all the produced data FAIR via the eNanoMapper repository.

Plastic ingestion by odontocetes from the Western South Atlantic: A particular concern to a threatened species

The ingestion of debris by marine fauna is a growing threat to biodiversity. This study aimed to evaluate and characterize litter ingestion by odontocetes from the Western South Atlantic. Between 2018 and 2022, 154 stomachs from six species were collected from stranded individuals and incidental captures. Stomach contents were analyzed with the naked eye and items of anthropic origin found were counted and physically/chemically characterized. Generalized Linear Models were used to evaluate the influence of biological factors on the presence/absence of litter in stomachs, and for Pontoporia blainvillei only, the influence of these factors on the number of ingested items was also tested; additionally, a temporal analysis of ingestion was done for this species (1994-2022). A total of 156 items, mainly macro-sized plastics made of polypropylene, were found in 52 stomachs of four species: Tursiops spp. (FO% = 3.3%), Steno bredanensis (10.0%), Delphinus delphis (28.6%) and P. blainvillei (47.5%). The presence/absence of litter was explained only by species (χ2 = 28.29 and p < 0.001). For P. blainvillei, a threatened species in the region, the number of items was positively influenced by individual size (χ2 = 6.01 and p = 0.01) and sex (χ2 = 7.93 and p = 0.005). There was an increase in plastic ingestion by this species over the years (χ2 = 121.6 and p < 0.001) and it was estimated that 75% of P. blainvillei stomachs will contain plastic by 2040. The ingestion of litter by odontocetes from the Western South Atlantic was confirmed and the potential risks posed by this type of pollution were evidenced, especially since these species also face other anthropic pressures. These results further demonstrate the increasing threat of litter in the ocean and highlight the importance of circularity of plastics and proper waste management.

Twenty years of microplastic pollution research-what have we learned?

Twenty years after the first publication that used the term microplastic, we review current understanding, refine definitions, and consider future prospects. Microplastics arise from multiple sources, including tires, textiles, cosmetics, paint, and the fragmentation of larger items. They are widely distributed throughout the natural environment, with evidence of harm at multiple levels of biological organization. They are pervasive in food and drink and have been detected throughout the human body, with emerging evidence of negative effects. Environmental contamination could double by 2040, and wide-scale harm has been predicted. Public concern is increasing, and diverse measures to address microplastic pollution are being considered in international negotiations. Clear evidence on the efficacy of potential solutions is now needed to address the issue and to minimize the risks of unintended consequences.

Microplastic ingestion in five demersal, bathydemersal and bathypelagic fish species from the eastern Weddell Sea, Antarctica

Antarctica has traditionally been viewed as a relatively isolated ecosystem. Although still considered pristine, it is increasingly also being affected by microplastic pollution. Reported high sea floor concentrations raise concern that these ecosystems might act as major sink for microplastic pollution. This is significant as species in those remote ecosystems are likely more sensitive to rapid environmental change due to a high level of specialization, and lower tolerance levels. Microplastic ingestion in fish has barely been assessed in high latitude environments. Here we aimed to provide baseline data for the eastern Weddell Sea, which is particularly remote, and suggested for an area of conservation. By analyzing gastrointestinal tracts of 40 specimens from five species, we report an overall microplastic incidence rate of 0.23. This is lower than recent studies have found for other species in the Southern Ocean, and below global means. The highest incidence rate was detected in L. squamifrons (0.67), followed by P. evansii (0.29). The most common polymer was polyethylene recovered as 8 particles (42.1 %) from one specimen, while from the remaining 11 microplastics polyester was most common (36.8 %). This study shows that even in a remote region of the Antarctic Ocean with almost no vessel traffic, fisheries or touristic activity, bathydemersal and bathypelagic fish exhibit microplastic particles in their gastrointestinal tract.

Predator traits influence uptake and trophic transfer of nanoplastics in aquatic systems-a mechanistic study

Predicting the response of aquatic species to environmental contaminants is challenging, in part because of the diverse biological traits within communities that influence their uptake and transfer of contaminants. Nanoplastics are a contaminant of growing concern, and previous research has documented their uptake and transfer in aquatic food webs. Employing an established method of nanoplastic tracking using metal-doped plastics, we studied the influence of biological traits on the uptake of nanoplastic from water and diet in freshwater predators through two exposure assays. We focused on backswimmers (Anisops wakefieldi) and damselfly larvae (Xanthocnemis zealandica) - two freshwater macroinvertebrates with contrasting physiological and morphological traits related to feeding and respiration strategies. Our findings reveal striking differences in nanoplastic transfer dynamics: damselfly larvae accumulated nanoplastics from water and diet and then efficiently eliminated 92% of nanoplastic after five days of depuration. In contrast, backswimmers did not accumulate nanoplastic from either source. Differences in nanoplastic transfer dynamics may be explained by the contrasting physiological and morphological traits of these organisms. Overall, our results highlight the importance and potential of considering biological traits in predicting transfer of nanoplastics through aquatic food webs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s43591-024-00096-4.

Investigating Exposure and Hazards of Micro- and Nanoplastics During Pregnancy and Early Life (AURORA Project): Protocol for an Interdisciplinary Study

BACKGROUND

Micro- and nanoplastics (MNPs) are emerging pollutants of concern with ubiquitous presence in global ecosystems. MNPs pose potential implications for human health; however, the health impacts of MNP exposures are not yet understood. Recent evidence suggests that MNPs can cross the placental barrier, underlying the urgent need to understand their impact on reproductive health and development.

OBJECTIVE

The Actionable eUropean ROadmap for early-life health Risk Assessment of micro- and nanoplastics (AURORA) project will investigate MNP exposures and their biological and health effects during pregnancy and early life, which are critical periods due to heightened vulnerability to environmental stressors. The AURORA project will enhance exposure assessment capabilities for measuring MNPs, MNP-associated chemicals, and plastic additives in human tissues, including placenta and blood.

METHODS

In this interdisciplinary project, we will advance methods for in-depth characterization and scalable chemical analytical strategies, enabling high-resolution and large-scale toxicological, exposure assessment, and epidemiological studies. The AURORA project performs observational studies to investigate determinants and health impacts of MNPs by including 800 mother-child pairs from 2 existing birth cohorts and 110 women of reproductive age from a newly established cohort. This will be complemented by toxicological studies using a tiered-testing approach and epidemiological investigations to evaluate associations between maternal and prenatal MNP exposures and health perturbations, such as placental function, immune-inflammatory responses, oxidative stress, accelerated aging, endocrine disruption, and child growth and development. The ultimate goal of the AURORA project is to create an MNP risk assessment framework and identify the remaining knowledge gaps and priorities needed to comprehensively assess the impact of MNPs on early-life health.

RESULTS

In the first 3 years of this 5-year project (2021-2026), progress was made toward all objectives. This includes completion of recruitment and data collection for new and existing cohorts, development of analytical methodological protocols, and initiation of the toxicological tiered assessments. As of September 2024, data analysis is ongoing and results are expected to be published starting in 2025.

CONCLUSIONS

As plastic pollution increases globally, it is imperative to understand the impact of MNPs on human health, particularly during vulnerable developmental stages such as early life. The contributions of the AURORA project will inform future risk assessment.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/63176.

Towards reliable data: Validation of a machine learning-based approach for microplastics analysis in marine organisms using Nile red staining

Microplastic (MP) research faces challenges due to costly, time-consuming, and error-prone analysis techniques. Additionally, the variability in data quality across studies limits their comparability. This study addresses the critical need for reliable and cost-effective MP analysis methods through validation of a semi-automated workflow, where environmentally relevant MP were spiked into and recovered from marine fish gastrointestinal tracts (GITs) and blue mussel tissue, using Nile red staining and machine learning automated analysis of different polymers. Parameters validated include trueness, precision, uncertainty, limit of quantification, specificity, sensitivity, selectivity, and method robustness. For fish GITs a 95 ± 9 % recovery rate was achieved, and 87 ± 11 % for mussels. Polymer identification accuracies were 76 ± 8 % for fish GITs and 80 ± 13 % for mussels. Polyethylene terephthalate fragments showed more variability with lower accuracies. The proposed validation parameters offer a step towards quality management guidelines, as such aiding future researchers and fostering cross-study comparability.

Addressing the relevance of polystyrene nano- and microplastic particles used to support exposure, toxicity and risk assessment: implications and recommendations

BACKGROUND

There has been an exponential increase in the number of studies reporting on the toxicological effects associated with exposure to nano and microplastic particles (NMPs). The majority of these studies, however, have used monodispersed polystyrene microspheres (PSMs) as 'model' particles. Here we review the differences between the manufacture and resulting physicochemical properties of polystyrene used in commerce and the PSMs most commonly used in toxicity studies.

MAIN BODY

In general, we demonstrate that significant complexity exists as to the properties of polystyrene particles. Differences in chemical composition, size, shape, surface functionalities and other aspects raise doubt as to whether PSMs are fit-for-purpose for the study of potential adverse effects of naturally occurring NMPs. A realistic assessment of potential health implications of the exposure to environmental NMPs requires better characterisation of the particles, a robust mechanistic understanding of their interactions and effects in biological systems as well as standardised protocols to generate relevant model particles. It is proposed that multidisciplinary engagement is necessary for the development of a timely and effective strategy towards this end. We suggest a holistic framework, which must be supported by a multidisciplinary group of experts to work towards either providing access to a suite of environmentally relevant NMPs and/or developing guidance with respect to best practices that can be adopted by research groups to generate and reliably use NMPs. It is emphasized that there is a need for this group to agree to a consensus regarding what might best represent a model NMP that is consistent with environmental exposure for human health, and which can be used to support a variety of ongoing research needs, including those associated with exposure and hazard assessment, mechanistic toxicity studies, toxicokinetics and guidance regarding the prioritization of plastic and NMPs that likely represent the greatest risk to human health. It is important to acknowledge, however, that establishing a multidisciplinary group, or an expert community of practice, represents a non-trivial recommendation, and will require significant resources in terms of expertise and funding.

CONCLUSION

There is currently an opportunity to bring together a multidisciplinary group of experts, including polymer chemists, material scientists, mechanical engineers, exposure and life-cycle assessment scientists, toxicologists, microbiologists and analytical chemists, to provide leadership and guidance regarding a consensus on defining what best represents environmentally relevant NMPs. We suggest that given the various complex issues surrounding the environmental and human health implications that exposure to NMPs represents, that a multidisciplinary group of experts are thus critical towards helping to progress the harmonization and standardization of methods.

Effect of an antidepressant on aquatic ecosystems in the presence of microplastics: A mesocosm study

Emerging pollutants, such as pharmaceuticals and microplastics have become a pressing concern due to their widespread presence and potential impacts on ecological systems. To assess the ecosystem-level effects of these pollutants within a multi-stressor context, we simulated real-world conditions by exposing a near-natural multi-trophic aquatic food web to a gradient of environmentally relevant concentrations of fluoxetine and microplastics in large mesocosms over a period of more than three months. We measured the biomass and abundance of different trophic groups, as well as ecological functions such as nutrient availability and decomposition rate. To explore the mechanisms underlying potential community and ecosystem-level effects, we also performed behavioral assays focusing on locomotion parameters as a response variable in three species: Daphnia magna (zooplankton prey), Chaoborus flavicans larvae (invertebrate pelagic predator of zooplankton) and Asellus aquaticus (benthic macroinvertebrate), using water from the mesocosms. Our mesocosm results demonstrate that presence of microplastics governs the response in phytoplankton biomass, with a weak non-monotonic dose-response relationship due to the interaction between microplastics and fluoxetine. However, exposure to fluoxetine evoked a strong non-monotonic dose-response in zooplankton abundance and microbial decomposition rate of plant material. In the behavioral assays, the locomotion of zooplankton prey D. magna showed a similar non-monotonic response primarily induced by fluoxetine. Its predator C. flavicans, however, showed a significant non-monotonic response governed by both microplastics and fluoxetine. The behavior of the decomposer A. aquaticus significantly decreased at higher fluoxetine concentrations, potentially leading to reduced decomposition rates near the sediment. Our study demonstrates that effects observed upon short-term exposure result in more pronounced ecosystem-level effects following chronic exposure.

Nationwide meta-analysis of microplastic distribution and risk assessment in China's aquatic ecosystems, soils, and sediments

Microplastic (MP) accumulation has recently become a pressing global environmental challenge. As a major producer and consumer of plastic products, China's MP pollution has garnered significant attention from researchers. However, accurate and comprehensive investigations of national-level MP pollution are still lacking. In this study, we systematically collated a national MP pollution dataset consisting of 7766 water, soil, and sediment sampling sites from 544 publicly published studies, revealing the spatiotemporal distribution and potential risks of MP pollution in China. The results indicate that MP distribution is influenced by various regional factors, including economic development level, population distribution, and geographical environment, exhibiting considerable range and complexity. MP concentrations are generally higher in economically prosperous areas, but the degree of pollution varies significantly across different environmental media. Given the uncertainty and lack of standardized data in traditional microplastic risk assessment methods, this article highlights the urgency of developing a comprehensive big data and artificial intelligence (AI)-based regulatory framework. This work provides a substantial amount of accurate MP pollution data and offers a fresh perspective on leveraging AI for microplastic pollution regulation.

Geometric relationship between the projected surface area and mass of a plastic particle

The quantification of the mass of meso/microplastic (MMP) particles is crucial for assessing the global inventory of ocean plastics and assessing environmental and human health risks. Herein, linear regression models between mass and projected surface area on a log scale were established by directly measuring the masses of 4390 MMP particles collected at 35 sites in 17 Japanese rivers with an ultramicrobalance. The linear regression models estimated mass concentrations more accurately than any previous method based on geometric volume assuming several three-dimensional shapes. Additionally, linear regression models were quite reasonable for determining the geometric relationships of idealized cuboid particles. The slope of the linear regression models was dependent on the three-dimensional shapes of the particles, and their intercept was determined according to their third dimension. Moreover, the third dimension led to uncertainty in the mass estimation of particles; thus, the accuracies of the previous methods were relatively poor. Nevertheless, two limitations for mass measurement by linear regression models were identified, which determined the size range of the MMP particles on the projected surface area (ranging from 10-4 mm2 to 102 mm2) that is applicable for mass estimation of the particles collected from riverine and marine environments. Our results could be used to accurately estimate the mass concentrations in aquatic environments and provide insights into the geometric relationships between the mass and size of MMP particles.

Nanoplastics enhanced the developmental toxicity of aromatic disinfection byproducts to a marine polychaete at non-feeding early life stage

Micro/nanoplastics can act as vectors for organic pollutants and enhance their toxicity, which has been attributed to the ingestion by organisms and the "Trojan horse effect". In this study, we disclosed a non-ingestion pathway for the toxicity enhancement effect of nanoplastics. Initially, the combined toxicity of polystyrene microplastics (40 μm) or nanoplastics (50 nm) with three disinfection byproducts (DBPs) to a marine polychaete, Platynereis dumerilii, was investigated. No toxic effect was observed for the micro/nanoplastics alone. The microplastics showed no effect on the toxicity of the three DBPs, whereas the nanoplastics significantly enhanced the toxicity of two aromatic DBPs when the polychaete was in its non-feeding early life stage throughout the exposure period. The microplastics showed no interaction with the P. dumerilii embryos, whereas the nanoplastics agglomerated strongly on the embryonic chorion and fully encapsulated the embryos. This could contribute to higher actual exposure concentrations in the microenvironment around the embryos, as the concentrations of the two aromatic DBPs on the nanoplastics were 1200 and 120 times higher than those in bulk solution. Our findings highlight an important and previously overlooked mechanism by which nanoplastics and organic pollutants, such as DBPs, pose a higher risk to marine species at their vulnerable early life stages. This study may contribute to a broader understanding of the environmental impacts of plastic pollution and underscore the necessity to mitigate their risks associated with DBPs.

Design of a Weathering Chamber for UV Aging of Microplastics in the Mediterranean Region

Microplastics are an ever-growing concern in the environment. Their degradation may lead to greater absorption of toxic pollutants, which may ultimately pose a threat to human health. In the pursuit of understanding microplastics' fate, behavior, and toxicity, there is a vital need to understand their aging and weathering. For this, multiple weathering setup designs were put forward. However, standardization of a weathering setup presents a significant challenge to the field due to apparatus costs, wide range of experimental parameters, or the lack of detailed reporting. This work seeks to make much-needed data gathering more accessible by constructing a low-cost weathering chamber that simulates Mediterranean shore conditions. The weathering chamber incorporates UV irradiation, mechanical abrasion, and elevated temperatures. After extensive preliminary testing, the chamber was able to achieve the desired outcome along with UV-A irradiance values, which were similar to those in the Mediterranean.

Research priorities on microplastics in marine and coastal environments: An Australian perspective to advance global action

Plastic and microplastic contamination in the environment receive global attention, with calls for the synthesis of scientific evidence to inform actionable strategies and policy-relevant practices. We provide a systematic literature review on microplastic research across Australian coastal environments in water, sediment and biota, highlighting the main research foci and gaps in information. At the same time, we conducted surveys and workshops to gather expert opinions from multiple stakeholders (including researchers, industry, and government) to identify critical research directions to meet stakeholder needs across sectors. Through this consultation and engagement process, we created a platform for knowledge exchange and identified three major priorities to support evidence-based policy, regulation, and management. These include a need for (i) method harmonisation in microplastic assessments, (ii) information on the presence, sources, and pathways of plastic pollution, and (iii) advancing our understanding of the risk of harm to individuals and ecosystems.

When antibiotics encounter microplastics in aquatic environments: Interaction, combined toxicity, and risk assessments

Antibiotics and microplastics (MPs), known as emerging pollutants, are bound to coexist in aquatic environments due to their widespread distribution and prolonged persistence. To date, few systematic summaries are available for the interaction between MPs and antibiotics in aquatic ecosystems, and a comprehensive reanalysis of their combined toxicity is also needed. Based on the collected published data, we have analyzed the source and distribution of MPs and antibiotics in global aquatic environments, finding their coexistence occurs in a lot of study sites. Accordingly, the presence of MPs can directly alter the environmental behavior of antibiotics. The main influencing factors of interaction between antibiotics and MPs have been summarized in terms of the characteristics of MPs and antibiotics, as well as the environmental factors. Then, we have conducted a meta-analysis to evaluate the combined toxicity of antibiotics and MPs on aquatic organisms and the related toxicity indicators, suggesting a significant adverse effect on algae, and inapparent on fish and daphnia. Finally, the environmental risk assessments for antibiotics and MPs were discussed, but unfortunately the standardized methodology for the risk assessment of MPs is still challenging, let alone assessment for their combined toxicity. This review provides insights into the interactions and environment risks of antibiotics and MPs in the aquatic environment, and suggests perspectives for future research.

Microplastic in Dredged Sediments: From Databases to Strategic Responses

Microplastics (MPs) accumulate in sediments, yet guidelines for evaluating MP risks in dredged sediments are lacking. The objective of this study was to review existing literature on MPs in sediments to improve fundamental knowledge of MP exposures and develop a publicly available database of MPs in sediments. Twelve percent of the reviewed papers (nine studies) included sediment core samples with MP concentrations generally decreasing with depth, peaking in the top 15 cm. The remaining papers evaluated surficial grab samples (0 to 15 cm depth) from various water bodies with MPs detected in almost every sample. Median MP concentrations (items/kg dry sediment) increased in this order: lakes and reservoirs (184), estuarine (263), Great Lakes nearshore areas and tributaries (290), riverine (410), nearshore marine areas (487), dredge activities (817), and harbors (948). Dredging of recurrent shoaling sediments could be expected to contain MPs at various depths with concentrations influenced by the time elapsed since the last dredging event. These results offer key insights into the presence and variability of MPs in dredged sediments, informing environmental monitoring and risk assessment strategies.

Source-specific probabilistic risk assessment of microplastics in soils applying quality criteria and data alignment methods

The risk characterization of microplastics (MP) in soil is challenging due to the non-alignment of existing exposure and effect data. Therefore, we applied data alignment methods to assess the risks of MP in soils subject to different sources of MP pollution. Our findings reveal variations in MP characteristics among sources, emphasizing the need for source-specific alignments. To assess the reliability of the data, we applied Quality Assurance/Quality Control (QA/QC) screening tools. Risk assessment was carried out probabilistically, considering uncertainties in data alignments and effect thresholds. The Hazardous Concentrations for 5% (HC5) of the species were significantly higher compared to earlier studies and ranged between 4.0 × 107 and 2.3 × 108 particles (1-5000 µm)/kg of dry soil for different MP sources and ecologically relevant metrics. The highest risk was calculated for soils with MP entering via diffuse and unspecified local sources, i.e., "background pollution". However, the source with the highest proportion of high-risk values was sewage, followed by background pollution and mulching. Notably, locations exceeding the risk threshold obtained low scores in the QA/QC assessment. No risks were observed for soils with compost. To improve future risk assessments, we advise to primarily test environmentally relevant MP mixtures and adhere to strict quality criteria.

Nano- and microplastic PBK modeling in the context of human exposure and risk assessment

Insufficient data on nano- and microplastics (NMP) hinder robust evaluation of their potential health risks. Methodological disparities and the absence of established toxicity thresholds impede the comparability and practical application of research findings. The diverse attributes of NMP, such as variations in sizes, shapes, and compositions, complicate human health risk assessment. Although probability density functions (PDFs) show promise in capturing this diversity, their integration into risk assessment frameworks is limited. Physiologically based kinetic (PBK) models offer a potential solution to bridge the gap between external exposure and internal dosimetry for risk evaluation. However, the heterogeneity of NMP poses challenges for accurate biodistribution modeling. A literature review, encompassing both experimental and modeling studies, was conducted to examine biodistribution studies of monodisperse micro- and nanoparticles. The literature search in PubMed and Scopus databases yielded 39 studies that met the inclusion criteria. Evaluation criteria were adapted from previous Quality Assurance and Quality Control (QA-QC) studies, best practice guidelines from WHO (2010), OECD guidance (2021), and additional criteria specific to NMP risk assessment. Subsequently, a conceptual framework for a comprehensive NMP-PBK model was developed, addressing the multidimensionality of NMP particles. Parameters for an NMP-PBK model are presented. QA-QC evaluations revealed that most experimental studies scored relatively well (>0) in particle characterizations and environmental settings but fell short in criteria application for biodistribution modeling. The evaluation of modeling studies revealed that information regarding the model type and allometric scaling requires improvement. Three potential applications of PDFs in PBK modeling of NMP are identified: capturing the multidimensionality of the NMP continuum, quantifying the probabilistic definition of external exposure, and calculating the bio-accessibility fraction of NMP in the human body. A framework for an NMP-PBK model is proposed, integrating PDFs to enhance the assessment of NMP's impact on human health.

Everything falls apart: How solids degrade and release nanomaterials, composite fragments, and microplastics

To ensure the safe use of materials, one must assess the identity and quantity of exposure. Solid materials, such as plastics, metals, coatings and cements, degrade to some extent during their life cycle, and releases can occur during manufacturing, use and end-of-life. Releases (e.g., what is released, how does release happen, and how much material is released) depend on the composition and internal (nano)structures of the material as well as the applied stresses during the lifecycle. We consider, in some depth, releases from mechanical, weathering and thermal stresses and specifically address the use cases of fused-filament 3D printing, dermal contact, food contact and textile washing. Solid materials can release embedded nanomaterials, composite fragments, or micro- and nanoplastics, as well as volatile organics, ions and dissolved organics. The identity of the release is often a heterogenous mixture and requires adapted strategies for sampling and analysis, with suitable quality control measures. Control materials enhance robustness by enabling comparative testing, but reference materials are not always available as yet. The quantity of releases is typically described by time-dependent rates that are modulated by the nature and intensity of the applied stress, the chemical identity of the polymer or other solid matrix, and the chemical identity and compatibility of embedded engineered nanomaterials (ENMs) or other additives. Standardization of methods and the documentation of metadata, including all the above descriptors of the tested material, applied stresses, sampling and analytics, are identified as important needs to advance the field and to generate robust, comparable assessments. In this regard, there are strong methodological synergies between the study of all solid materials, including the study of micro- and nanoplastics. From an outlook perspective, we review the hazard of the released entities, and show how this informs risk assessment. We also address the transfer of methods to related issues such as tyre wear, advanced materials and advanced manufacturing, biodegradable polymers, and non-solid matrices. As the consideration of released entities will become more routine in industry via lifecycle assessment in Safe-and-Sustainable-by-Design practices, release assessments will require careful design of the study with quality controls, the use of agreed-on test materials and standardized methods where these exist and the adoption of clearly defined data reporting practices that enable data reuse, meta-analyses, and comparative studies.

Alteration of shoaling behavior and dysbiosis in the gut of medaka (Oryzias latipes) exposed to 2-μm polystyrene microplastics

There is global concern that microplastics may harm aquatic life. Here, we examined the effects of fine polystyrene microplastics (PS-MPs, 2-μm diameter, 0.1 mg/L, 2.5 × 107 particles/L) on the behavior and the microbiome (linked to brain-gut interaction) of a fish model using medaka, Oryzias latipes. We found that shoaling behavior was reduced in PS-MP-exposed medaka compared with control fish during the exposure period, but it recovered during a depuration period. There was no difference in swimming speed between the PS-MP-exposed and control groups during the exposure period. Analysis of the dominant bacterial population (those comprising ≥1% of the total bacterial population) in the gut of fish showed that exposure to PS-MPs tended to increase the relative abundance of the phylum Fusobacteria and the genus Vibrio. Furthermore, structural-equation modeling of gut bacteria on the basis of machine-learning data estimated strong relationship involved in the reduction of the functional bacterial species of minority (<1% of the total bacterial population) such as the genera Muribaculum (an undefined role), Aquaspirillum (a candidate for nitrate metabolism and magnetotactics), and Clostridium and Phascolarctobacterium (potential producers of short-chain fatty acids, influencing behavior by affecting levels of neurotransmitters) as a group of gut bacteria in association with PS-MP exposure. Our results suggest that fish exposure to fine microplastics may cause dysbiosis and ultimately cause social behavior disorders linked to brain-gut interactions. This effect could be connected to reduction of fish fitness in the ecosystem and reduced fish survival.

Microplastics in the Water Column of the Rhine River Near Basel: 22 Months of Sampling

Measured microplastic concentrations in river surface waters fluctuate greatly. This variability is affected by season and is codriven by factors, such as sampling methodologies, sampling site, or sampling position within site. Unfortunately, most studies comprise single-instance measurements, whereas extended sampling periods are better suited to assessing the relevance of such factors. Moreover, microplastic concentrations in riverine water column remain underexplored. Similar to the oceans, however, this compartment likely holds significant amounts of microplastics. By representatively sampling the entire Rhine River cross-section near Basel through five sampling points over 22 months, we found a median microplastic (50-3000 μm) concentration of 4.48 n m-3, and estimated a widely ranging load between 4.04 × 102 n s-1 and 3.57 × 105 n s-1. We also show that the microplastic concentration in the water column was not well explained by river discharge. This suggests that although high discharge events as observed here can over short time periods lead to peak microplastic concentrations (e.g., 1.23 × 102 n m-3), microplastic load variance was not dominated by discharge in the study area.

Health assessment based on exposure to microplastics in tropical agricultural soil

Microplastic (MP) pollution of agricultural soils has caused global alarm over its widespread distribution and potential risks to terrestrial ecosystems and human health. This study assessed human health based on exposure to soil MPs through a comprehensive investigation of the factors influencing their occurrence and spatial distribution on Hainan Island, South China. The results showed that the abundance of soil MPs was 1128.6 ± 391.5 items·kg-1, whereas the normalized abundance of MPs based on using a power-law function was 19,261.4 items·kg-1. Regarding the extent of population exposure to agricultural soil MPs, the average daily exposure dose (pADD) model revealed that using mass as an indicator to assess the health risks associated with MP intake is more reliable than using abundance. However, abundance-based exposure assessments are also relevant because MPs with smaller particle sizes are more harmful to human health. Moreover, for adults, the normalized pADD values based on abundance and mass were 1.68E-02 item MPs·kg BW-1·d-1 and 7.23E-02 mg MPs·kg BW-1·d-1, respectively. Although the multidimensionality of MPs should be further aligned and quantified, the preliminary findings of this study contribute to the development of human health risk assessment frameworks for soil MPs.