Bioavailability and toxicity of microplastics to fish species: A review

Adsorption of di (2-ethylhexyl) phthalate (DEHP) to microplastics in seawater: a comparison between pristine and aged particles

Microplastics (MPs) are a widely distributed pollutant and have been attracting global attention. The increasing abundance of MPs in marine environments has raised concern about their adverse effects on marine organisms and influence on the fate of contaminants in seawater. In this study, we investigated the effects of natural aging on the adsorption of di (2-ethylhexyl) phthalate (DEHP), one of the most widely used phthalic acid esters (PAEs), in two types of MPs (polyethylene and polystyrene). Biofilm was observed on the surface of MPs after 3-month exposure in seawater. Atomic force microscopy revealed there were significant physical changes in the MPs after aging. Aging in coastal seawater for 3 months significantly reduced the MPs' surface roughness and adhesion, and increased the Young's modulus at the same time. Adsorption isotherms of DEHP indicated that aged MPs had stronger binding capacity of the organic contaminant than pristine MPs. Our data shed some light on the biogeochemical role of MPs in marine environments.

Comparing the influence of humic/fulvic acid and tannic acid on Cr(VI) adsorption onto polystyrene microplastics: Evidence for the formation of Cr(OH)3 colloids

Microplastics (MPs) can act as vectors for various contaminants in the aquatic environment. Although some research has investigated the adsorption characteristics and influencing factors of metals/organic molecules on MPs, the effects of dissolved organic matter (DOM) (which are ubiquitous active species in ecosystems) on metal oxyanions such as Cr(VI) capture by MPs are largely unknown. This study explored the adsorption behaviors and mechanisms of Cr(VI) oxyanions onto polystyrene (PS) MPs using batch adsorption experiments and multiple spectroscopic methods. The effects of representative DOM components (i.e., humic acid (HA), fulvic acid (FA) and tannic acid (TA)) on Cr(VI) capture by PS were particularly studied. Results revealed a significantly enhanced adsorption of Cr(VI) on PS in the presence of TA. The Cr(VI) adsorption capacity was increased from 2876 μg g^-1 to 4259 μg g^-1 and 5135 μg g^-1 when the TA concentrations raised from 0 to 10 and 20 mg L^-1, respectively. Combined microscopic and spectroscopic investigations revealed that Cr(VI) was reduced to Cr(III) by TA and formed stable Cr(OH)₃ colloids on PS surfaces. Contrarily, HA and FA inhibited Cr(VI) adsorption onto PS, especially at pH > 2.0 and higher DOM concentrations, due to site competition and electrostatic repulsion. Increase in pH was found to reduce zeta potentials of MPs, resulting in inhibited Cr(VI) adsorption. The adsorbed Cr(VI) declined with increasing ionic strength, implying that outer-sphere surface complexation affected the adsorption process in the presence of DOM. These new findings improved our fundamental understanding of the fate of Cr(VI) and MPs in DOM-rich environmental matrices.

Plants oxidative response to nanoplastic

Pollution of the environment with plastic is an important concern of the modern world. It is estimated that annually over 350 million tonnes of this material are produced, wherein, despite the recycling methods, a significant part is deposited in the environment. The plastic has been detected in the industrial areas, as well as farmlands and gardens in many world regions. Larger plastic pieces degraded in time into smaller pieces including microplastic (MP) and nanoplastic particles (NP). Nanoplastic is suggested to pose the most serious danger as due to the small size, it is effectively taken up from the environment by the biota and transported within the organisms. An increasing number of reports show that NP exert toxic effects also on plants. One of the most common plant response to abiotic stress factors is the accumulation of reactive oxygen species (ROS). On the one hand, these molecules are engaged in cellular signalling and regulation of genes expression. On the other hand, ROS in excess lead to oxidation and damage of various cellular compounds. This article reviews the impact of NP on plants, with special emphasis on the oxidative response.

Exposure to Environmentally Relevant Concentrations of Polystyrene Microplastics Increases Hexavalent Chromium Toxicity in Aquatic Animals

The prevalence of hexavalent chromium [Cr(VI)] and microplastics (MPs) is ubiquitous and is considered a threat to aquatic biota. MPs can act as a vector for waterborne metals; however, the combined effects of Cr(VI) and MPs on aquatic organisms are largely unknown. In this study, aquatic model animals, such as rotifers (Brachionus calyciflorus and B. plicatilis), water fleas (Daphnia magna), amphipods (Hyalella azteca), polychaetes (Perinereis aibuhitensis), and zebrafish (Danio rerio) were exposed to environmental concentrations (1, 10, and 100 particles L^-1) of 1 μm polystyrene MPs alone, Cr(VI) alone, or Cr(VI) combined with MPs. Following exposure, the potential effects were measured by analyzing basic life endpoints (e.g., survival rate and growth). A significant response to MPs alone was not observed in all animals. However, MPs combined with Cr(VI) concentration-dependently increased Cr(VI) toxicity in two rotifer species. The survival rate of water fleas was significantly reduced upon exposure to Cr(VI) + MPs (100 particles L^-1) compared with exposure to Cr(VI) alone, and significantly decreased the number of offspring. Although there was no significant effect on the body length of the amphipod, concentration-dependent decreases in their survival rates were observed. In contrast, no significant change was found in the survival rate of polychaetes; however, their burrowing ability was inhibited by Cr(VI) + MPs (100 particles L^-1). Further, larval mortality was increased in response to Cr(VI) + MPs (100 particles L^-1) in zebrafish. Taken together, the findings suggest that MPs can exacerbate Cr(VI) toxicity, even at environmental levels.

Integrated biomarker responses in European seabass Dicentrarchus labrax (Linnaeus, 1758) chronically exposed to PVC microplastics

Few studies evaluated long-term effects of polyvinyl chloride (PVC) microplastics (MPs) ingestion in fish. The present study aimed to investigate the integrated biomarker responses in the liver and blood of 162 European seabass, Dicentrarchus labrax, exposed for 90 days to control, virgin and marine incubated PVC enriched diets (0.1 % w/w) under controlled laboratory condition. Enzymatic and tissue alterations, oxidative stress, gene expression alterations and genotoxicity were examined. Additives and environmental contaminants levels in PVC-MPs, control feed matrices and in seabass muscles were also detected. The results showed that the chronic exposure at environmentally realistic PVC-MPs concentrations in seabass, cause early warning signs of toxicological harm in liver by induction of oxidative stress, the histopathological alterations and also by the modulation of the Peroxisome proliferator-activated receptors (PPARs) and Estrogen receptor alpha (ER-α) genes expression. A trend of increase of DNA alterations and the observation of some neoformations attributable to lipomas suggest also genotoxic and cancerogenic effects of PVC. This investigation provides important data to understand the regulatory biological processes affected by PVC-MPs ingestion in marine organisms and may also support the interpretation of results provided by studies on wild species.

Are there plastic particles in my sugar? A pioneering study on the characterization of microplastics in commercial sugars and risk assessment

Although several studies are confirming the ubiquity of microplastics (MPs) in environments, our knowledge about their effects on human health is still very limited. Therefore, while we have not gathered definitive information on their consequences, studies that aim to identify the MPs sources constitute subsidies to better understand the various exposure pathways to these pollutants. Thus, we investigated the possible presence of MP-like particles in five brands of commercial sugars and two unpacked, unbranded, and unlabeled sugars (hereinafter referred to as "non-branded"), obtained from different supermarkets in Dhaka (Bangladesh). Surprisingly, MPs-like particles were identified in all analyzed samples and taken together, our data demonstrated similar variations (between branded and non-branded samples) in terms of number, size, shape, color, and polymer composition. The number of plastic particles/kg sugar was, on average, 343.7 ± 32.08 (mean ± SEM), having been observed a tendency for a higher frequency of MPs < 300 μm. Overall, microfibers and spherules were the most and the predominant colors of MPs (in general) were black, pink, blue, and brown. The FT-IR analysis confirmed the chemical nature of MPs (in branded and non-branded), having identified nine polymeric types (ABS, PCV, PET, EVA, CA, PTFE, HDPE, PC, and nylon), being ABS and PVC the most frequent. Furthermore, we estimate that sugar consumption in Dhaka City can cause the ingestion of millions of tons of MPs annually (2.4 to 25.6 tons) (with an average of 10.2 tons). Our study is the most comprehensive report on the MP's occurrence in sugar, confirming that the ingestion of this food constitutes an important route of human exposure to these micropollutants and, therefore, serves as a baseline for future assessments and useful for generating efficient strategies to control MPs.

Dietary consumption of polypropylene microplastics alter the biochemical parameters and histological response in freshwater benthic mollusc Pomacea paludosa

One of the most common environmental pollutant in aquatic ecosystems are polypropylene microplastics and their impacts on aquatic organisms are still scarce. The study aimed to prepare polypropylene microplastics using organic solvent (spherical and 11.86-44.62 μm) and then test their toxicity on the freshwater benthic mollusc grazer Pomaceae paludosa. The present study investigated chronic (28 days) exposure of polypropylene microplastics via dietary supplements (250 mg kg^-1, 500 mg kg^-1 & 750 mg kg^-1) in P. paludosa, and the toxic effect was evaluated in digestive gland tissue. The FTIR results revealed no change in polypropylene microplastics during ingestion or after egestion. On the other hand, Ingestion causes accumulation in their bodies and disrupts redox homeostasis. Meanwhile, alteration occurs in oxidative stress-related biomarkers such as increased reactive oxygen species level (ROS), impaired the biochemical parameters of antioxidant system catalase (CAT), glutathione peroxidase (GPx), reduced glutathione (GSH), and glutathione - S- transferase (GST), deterioration of oxidative stress effects in lipid peroxidation (LPO) and carbonyl protein (CP) and changed the digestive enzymes such as amylase, pepsin, esterase and alkaline phosphatase that are measured in hepatopancreas tissue. The histology results revealed that ingesting these microplastics caused severe damage to the digestive gland cells. According to the findings, ingestion of polypropylene microplastics in benthic freshwater mollusc causes more serious harm and impacts energy acquisition. This finding represents the ecological risk of polypropylene microplastic pollution in the freshwater ecosystem.

First biomonitoring of microplastic pollution in the Vaal river using Carp fish (Cyprinus carpio) "as a bio-indicator"

Fish inhabiting freshwater environments are susceptible to the ingestion of microplastics (MPs). Knowledge regarding MPs in freshwater fish in South Africa is very limited. In this study, the uptake of MPs by common carp (Cyprinus carpio) in the Vaal River in South Africa was assessed. MPs were detected in all of the twenty-six fish examined, 682 particles of MPs were recovered from the gastrointestinal tracts of the fish with an average of 26.23 ± 12.57 particles/fish, and an average abundance of 41.18 ± 52.81 particles/kg. The examination of the physical properties of MPs revealed a predominance on fibers (69%), small-sized particles of less than 0.5 mm (48%), as well as prevelance of coloured MPs (94%), mostly green, blue, and black. Using Raman Spectroscopy, the following plastic polymers were identified: high density polyethylene (HDPE), low density polyethylene (LDPE), polypropylene (PP), polyethylene terephthalate (PET), and polytetrafluoroethylene (PTFE). To the best of our knowledge, this study, is the first to report MPs uptake by freshwater biota in the Vaal River using common carp as a target organism. It provided evidence of MP contamination in the Vaal.

Ecotoxicological effects of micro- and nanoplastics on terrestrial food web from plants to human beings

Micro- and nanoplastics (MNPs) are present in almost all environmental compartments. Terrestrial soils are major environmental reservoirs for MNPs, but the ecotoxicological effects of MNPs on terrestrial biota remain relatively understudied. In this review, we collated findings of previous research on the uptake and impact of MNPs in terrestrial organisms, including flora, fauna, and human beings. Terrestrial plants can take up MNPs via the roots or leaves and translocate them to other parts. MNPs have been detected in the gastrointestinal tracts or feces of many terrestrial animals, including some high trophic-level predators, indicating the incidence of direct ingestion or trophic transfer of MNPs. The presence of MNPs in food items and human feces combines to verify human intake of MNPs via the dietary pathway. Exposure to MNPs can cause diverse effects on terrestrial organisms, including alterations in growth performance, oxidative stress, metabolic disturbance, cytotoxicity, genotoxicity, and mortality. The biological internalization and impact of MNPs are influenced by the physicochemical properties of MNPs (e.g., particle size, polymer type, surface chemistry, and exposure concentrations) and the physiology of the species. MNPs can also affect the bioavailability of co-occurring intrinsic or extrinsic contaminants to terrestrial biota, but their specific role is under dispute. Finally, we underlined the current research gaps and proposed several priorities for future studies.

Seasonal variation in microplastics and zooplankton abundances and characteristics: The ecological vulnerability of an oceanic island system

The ingestion of microplastics (MPs - plastic particles <5 mm) by planktivorous organisms represents a significant threat to marine food webs. To investigate how seasonality might affect plastic intake in oceanic islands' ecosystems, relative abundances and composition of MPs and mesozooplankton samples collected off Madeira Island (NE Atlantic) between February 2019 and January 2020 were analysed. MPs were found in all samples, with fibres accounting for 89 % of the particles. MPs and zooplankton mean abundance was 0.262 items/m³ and 18.137 individuals/m³, respectively. Their monthly variations follow the seasonal fluctuation of environmental parameters, such as currents, chlorophyll-a concentration, sea surface temperature and precipitation intensity. A higher MPs/zooplankton ratio was recorded in the warm season (May-Oct), reaching 0.068 items/individual when considering large-sized particles (1000-5000 μm). This is the first study to assess the seasonal variability of MPs in an oceanic island system providing essential information respecting its ecological impact in pelagic environments.

Spatio-temporal contamination of microplastics in shellfish farming regions: A case study

The seasonal pattern of microplastics (MPs) contamination of the French littoral area of the Pertuis Charentais, one of the main French shellfish production regions, was assessed for the first time, between May 2019 and May 2020 at four different sites. The reference site was located at "Ile de Ré" and the other sites were located in the estuaries of the Sèvre Niortaise, Charente and Seudre rivers. Both blue mussels (Mytilus edulis) and Pacific oysters (Magallana gigas), that are considered sentinel species for the quality of the marine environment were analysed, along with sediment and seawater samples. MPs were extracted from each sample, counted, measured and sorted by colour and type. Micro-Raman spectroscopy was used to determine the proportion of confirmed MPs and the polymer types. The results showed that the contamination of mussels by fibres and fragments (1.9 ± 2.1 MPs/g ww) was significantly higher than for oysters (0.4 ± 0.4 MPs/g ww). Specifically, the contamination by fibres in both species was significantly greater than the contamination by fragments. Significant variations of MPs contamination were observed across the seasons and sites in bivalves, and depended on the species and the type of MPs (fibres or fragments). Mean concentrations of MPs measured in water and sediment were 0.007 MPs/L and 210 MPs/kg dw, respectively. Finally, blue was the dominant colour for fibres (79 %) and fragments (81 %). Blue fragments were mainly made of PS (70 %) followed by PC (18 %) and PP, PA or PLA (3 %) whereas blue fibres were mainly made of PA (80 %) followed by PET (13 %) or PP (7 %). This rare environmental case study of long-term chronic exposure of farming areas to MPs provides new knowledge on in situ variations of plastic fibres and fragments contamination throughout the seasons.

Microplastics across biomes in diadromous species. Insights from the critically endangered Anguilla anguilla

Microplastic pollution affects freshwater and marine biota worldwide, microplastics occurring even inside the organisms. With highly variable effects, from physical damage to toxicity of plastic compounds, microplastics are a potential threat to the biodiversity, community composition and organisms' health. This emerging pollutant could overstress diadromous species, which are exposed to both sea and river water in their life cycle. Here we have quantified microplastics in young European eel Anguilla anguilla, a critically endangered catadromous fish, entering three rivers in southwestern Bay of Biscay. River water, sediments and seawater were also analysed for microplastics. The microplastic type was identified using Fournier-Transform Infrared spectroscopy and then searched for their hazard potential at the European Chemical Agency site. Both riverine and sea microplastic pollution were predictors of eels' microplastic profile (types of microplastics by shape and colour): A. anguilla juveniles entering European rivers already carry some marine microplastics and acquire more from river water. Potentially hazardous plastic materials were found from eels, some of them dangerous for aquatic life following the European Chemical Agency. This confirms microplastics as a potential threat for the species. Between-rivers differences for microplastics profiles persistent over years highlight the convenience of analysing and preventing microplastics at a local spatial scale, to save diadromous species from this stressor. Since the origin of microplastics present in glass eels seems to be dual (continental + seawater), new policies should be promoted to limit the entry of microplastics in sea and river waters.

Differentiation in the expression of toxic effects of polyethylene-microplastics on two freshwater fish species: Size matters

The built up of microplastic (MPs) remains is shaping a new aquatic habitat and imposes the necessity for research of the effects that these relatively new pollutants exert on organisms, environment, and human health. The purpose of the present study was to verify if there is a particle-size dependence of fish response to MPs. Thus, we exposed two freshwater fish species, the zebrafish (Danio rerio) and perch (Perca fluviatilis) for 21 days to polyethylene microplastics (PE-MPs) sized 10-45 μm and 106-125 μm. Thereafter, in the liver and gills tissues, biochemical and molecular parameters and the metabolic profile were examined. Ex-vivo characterization by ATR-FTIR spectroscopy exhibited increased concentration of 10-45 μm PE-MPs in the liver of the two fish species while 106-125 μm PE-MPs mostly concentrated in fish gills. The penetration of PE-MPs to fish and the induced oxidative stress triggered changes in lipid peroxidation, DNA damage and ubiquitination and furthermore stimulated signal transduction pathways leading to autophagy and apoptosis. The smaller PE-MPs were more potent in inducing alterations to all the latter parameters measured than the larger ones. Tissue response in both fish seems to depend on the parameter measured and does not seem to follow a specific pattern. Our results showed that there is no clear sensitivity of one fish species versus the other, against both sizes of PE-MPs they were exposed. In perch the metabolic changes in gills were distinct to the ones observed in liver, following a size dependent pattern, indicating that stress conditions are generated through different mechanisms. All the parameters employed can be suggested further as biomarkers in biomonitoring studies against PE-MPs.

Environmental health impacts of microplastics exposure on structural organization levels in the human body

The ubiquitous prevalence of microplastics pollution has raised concerns about microplastics' potential risks and impacts on the global environment. However, the potential human health risks and impacts of microplastics remain largely unexplored. By providing an overview regarding the interaction of microplastics and human health, this review extends current knowledge on the potential impacts of microplastics pollution on humans from an environmental health perspective. The paper firstly presents the characteristics of microplastics as well as the status of global microplastics pollution. As for human health, the potential hazards of microplastics are reflected by toxic chemical components, vectors of contaminants, and physical damage. Extensive microplastic pollution on ecosystems due to human activities leads to inevitable human exposure, which may occur by dietary, inhalation and/or skin contact. Accordingly, microplastics exposure is closely associated with human health. This study explores the potential interactions of microplastics with the biological organization at various levels, including chemical, cellular, tissue, organ, and system levels. The review concludes by highlighting five urgent perspectives and implications for future research on microplastics: 1) Developing a standard terminology and research methods; 2) Reinforcing microplastics pollution governance; 3) Exploring innovative strategies and technologies; 4) Engaging the public and change behaviour; and 5) Adopting a transdisciplinary approach.

Automatic quantification and classification of microplastics in scanning electron micrographs via deep learning

Microplastics quantification and classification are demanding jobs to monitor microplastic pollution and evaluate the potential health risks. In this paper, microplastics from daily supplies in diverse chemical compositions and shapes are imaged by scanning electron microscopy. It offers a greater depth and finer details of microplastics at a wider range of magnification than visible light microscopy or a digital camera, and permits further chemical composition analysis. However, it is labour-intensive to manually extract microplastics from micrographs, especially for small particles and thin fibres. A deep learning approach facilitates microplastics quantification and classification with a manually annotated dataset including 237 micrographs of microplastic particles (fragments or beads) in the range of 50 μm-1 mm and fibres with diameters around 10 μm. For microplastics quantification, two deep learning models (U-Net and MultiResUNet) were implemented for semantic segmentation. Both significantly outmatched conventional computer vision techniques and achieved a high average Jaccard index over 0.75. Especially, U-Net was combined with object-aware pixel embedding to perform instance segmentation on densely packed and tangled fibres for further quantification. For shape classification, a fine-tuned VGG16 neural network classifies microplastics based on their shapes with high accuracy of 98.33%. With trained models, it takes only seconds to segment and classify a new micrograph in high accuracy, which is remarkably cheaper and faster than manual labour. The growing datasets may benefit the identification and quantification of microplastics in environmental samples in future work.

Toxicity evaluation of the combination of emerging pollutants with polyethylene microplastics in zebrafish: Perspective study of genotoxicity, mutagenicity, and redox unbalance

Despite the toxicity of microplastics (MPs) in freshwater fish has been demonstrated in previous studies, their effects when mixed with other pollutants (organic and inorganic) are poorly understood. Thus, we aimed to test the hypothesis that the association of polyethylene MPs (PE-MPs) to a mix of emerging pollutants induces more adverse genotoxic, mutagenic, and redox unbalance effects in adult zebrafish (Danio rerio), after 15 days of exposure. Although the accumulation of MPs in animals was greater in animals exposed to PE-MPs alone, erythrocyte DNA damage (comet assay) and the frequency of erythrocytic nuclear abnormalities (ENAs) evidenced in zebrafish exposed to PE-MPs alone were as pronounced as those observed in animals exposed to the mix of pollutant (alone or in combination with MPs), which constitutes the big picture of the current study. Moreover, we noticed that such effects were associated with an imbalance between pro-and antioxidant metabolism in animals, whose activity of superoxide dismutase (SOD) and catalase (CAT) was assessed in different organs which were not sufficient to counterbalance the production of reactive oxygen species [hydrogen peroxide (H₂O₂)] and nitrogen [nitric oxide (NO)] evaluated. The principal component analysis (PCA) also revealed that while the antioxidant activity was more pronounced in the brain and liver of animals, the highest production of H₂O₂ was perceived in the gills and muscles, suggesting that the biochemical response of the animals was organ-dependent. Thus, the present study did not demonstrate antagonistic, synergistic, or additive effects on animals exposed to the combination between PE-MPs and a mix of pollutants in the zebrafish, which reinforces the theory that interactions between pollutants in aquatic ecosystems may be as complex as their effects on freshwater ichthyofauna.

Optimization of polypropylene microplastics removal using conventional coagulants in drinking water treatment plants via response surface methodology

Background and purpose

The ubiquitous presence of microplastics (MPs) in aquatic environments has been studied widely. Due to toxicological impacts of MPs and associated contaminants, it is crucial to understand the performance of MPs removal in drinking water treatment plants (DWTPs). Few studies have investigated removal characteristics of MPs via coagulation/flocculation processes, yet removal characterization of polypropylene microplastics (PPMPs) in this process is poorly understood. This study aims to optimize coagulation of virgin PPMPs in conventional DWTPs.

Methods

In this study, samples were synthesized through response surface methodology (RSM), polyaluminium chloride (PACl) was applied as a conventional coagulant to remove PPMPs in the coagulation/flocculation process, which has the least density among common polymers and is one of the most abundant manufactured polymers worldwide. A particle size analyzer (PSA) was used to measure floc size at different pH levels. Additionally, a zeta potential analyzer was used to measure stability of the flocs at different pH.

Results

Base on the experimental range in Design-Expert, results revealed that the optimum removal rate was predicted to be at pH 9, PACl concentration of 200 ppm, polyacrylamide (PAM) concentration of 21 ppm, and PPMPs size of d < 0.25 mm. According to the predicted optimum condition, actual and predicted removal rates were 18.00 ± 1.43% and 19.69%, respectively.

Conclusion

According to this study, PACl is not capable of efficiently removing virgin PPMPs in DWTPs, thereby exposing humans to eco-toxicological impacts of PPMPs through tap water.

Microplastics in decapod crustaceans sourced from Australian seafood markets

Microplastic abundance and characteristics were assessed in five decapod crustaceans purchased from seafood markets and collected in coastal waters around Australia (South Australia, New South Wales, Queensland, Northern Territory, and Western Australia). Three species of prawns (king, banana and tiger prawns) and two species of crabs (blue-swimmer and mud crabs) were analysed. Muscle tissues and gastro-intestinal tracts in prawns, and gastro-intestinal tracts in crabs, were chemically digested, with microplastic identification verified using Fourier Transform Infrared spectroscopy. Forty-eight percent of crustaceans contained microplastics. Prawns and crabs had 0.8 ± 0.1 and 1.6 ± 0.1 pieces per individual, respectively, with spatial patterns evident. Microplastics were predominantly fibres (98%) of blue (58%) and black (24%) colours with polyolefin including polyester the most prevalent polymers. Overall, compared to a systematic review we performed of microplastics in decapod crustaceans worldwide, microplastic loads in crustaceans from Australia were in the lower range of plastic contamination.

Microplastic detection and identification by Nile red staining: Towards a semi-automated, cost- and time-effective technique

Microplastic pollution is an issue of concern due to the accumulation rates in the marine environment combined with the limited knowledge about their abundance, distribution and associated environmental impacts. However, surveying and monitoring microplastics in the environment can be time consuming and costly. The development of cost- and time-effective methods is imperative to overcome some of the current critical bottlenecks in microplastic detection and identification, and to advance microplastics research. Here, an innovative approach for microplastic analysis is presented that combines the advantages of high-throughput screening with those of automation. The proposed approach used Red Green Blue (RGB) data extracted from photos of Nile red-fluorescently stained microplastics (50-1200 μm) to train and validate a 'Plastic Detection Model' (PDM) and a 'Polymer Identification Model' (PIM). These two supervised machine learning models predicted with high accuracy the plastic or natural origin of particles (95.8%), and the polymer types of the microplastics (88.1%). The applicability of the PDM and the PIM was demonstrated by successfully using the models to detect (92.7%) and identify (80%) plastic particles in spiked environmental samples that underwent laboratorial processing. The classification models represent a semi-automated, high-throughput and reproducible method to characterize microplastics in a straightforward, cost- and time-effective yet reliable way.

Potential Risks of Microplastic Fomites to Aquatic Organisms with Special Emphasis on Polyethylene-Microplastic-Glyphosate Exposure Case in Aquacultured Shrimp

Plastic litter is increasingly becoming pervasive in aquatic environments, characterized by circulatory patterns between different compartments and continual loading with new debris. Microplastic pollution can cause a variety of effects on aquatic organisms. This review presents the current knowledge of microplastics distribution and sorption capacity, reflecting on possible bioaccumulation and health effects in aquatic organisms. A model case study reveals the fate and toxic effects of glyphosate, focusing on the simultaneous exposure of aquacultured shrimp to polyethylene and glyphosate and their contact route and on the potential effects on their health and the risk for transmission of the contaminants. The toxicity and bioaccumulation of glyphosate-sorbed polyethylene microplastics in shrimp are not well understood, although individual effects have been studied extensively in various organisms. We aim to delineate this knowledge gap by compiling current information regarding the co-exposure to polyethylene microplastic adsorbed with glyphosate to assist in the assessment of the possible health risks to aquacultured shrimp and their consumers.

Surgical face masks as a source of emergent pollutants in aquatic systems: Analysis of their degradation product effects in Danio rerio through RNA-Seq

Surgical face masks are the most popularised and effective personal equipment for protecting public health during the COVID-19 pandemic. They are composed of plastic polymer fibres with a large amount of inorganic and organic compounds that can be released into aquatic environments through degradation processes. This source of microplastics and inorganic and organic substances could potentially impact aquatic organisms. In this study, the toxicogenomic effects of face masks at different stages of degradation in water were analysed in zebrafish larvae (Danio rerio) through RNA-Seq. Larvae were exposed for 10 days to three treatments: 1) face mask fragments in an initial stage of degradation (poorly degraded masks -PDM- products) with the corresponding water; 2) face mask fragments in an advanced stage of degradation (highly degraded masks -HDM- products) with the corresponding water; and 3) water derived from HDM (W-HDM). Transcriptome analyses revealed that the three treatments provoked the down-regulation of genes related to reproduction, especially the HDM products, suggesting that degradation products derived from face masks could act as endocrine disruptors. The affected genes are involved in different steps of reproduction, including gametogenesis, sperm-egg recognition and binding or fertilisation. Immune-related genes and metabolic processes were also differentially affected by the treatments.

Ecotoxicity of microplastics to freshwater biota: Considering exposure and hazard across trophic levels

In contrast to marine ecosystems, the toxicity impact of microplastics in freshwater environments is poorly understood. This contribution reviews the literature on the range of effects of microplastics across and between trophic levels within the freshwater environment, including biofilms, macrophytes, phytoplankton, invertebrates, fish and amphibians. While there is supporting evidence for toxicity in some species e.g. growth reduction for photoautotrophs, increased mortality for some invertebrates, genetic changes in amphibians, and cell internalization of microplastics and nanoplastics in fish; other studies show that it is uncertain whether microplastics can have detrimental long-term impacts on ecosystems. Some taxa have yet to be studied e.g. benthic diatoms, while only 12% of publications on microplastics in freshwater, demonstrate trophic transfer in foodwebs. The fact that just 2% of publications focus on microplastics colonized by biofilms is hugely concerning given the cascading detrimental effects this could have on freshwater ecosystem function. Multiple additional stressors including environmental change (temperature rises and invasive species) and contaminants of anthropogenic origin (antibiotics, metals, pesticides and endocrine disruptors) will likely exacerbate negative interactions between microplastics and freshwater organisms, with potentially significant damaging consequences to freshwater ecosystems and foodwebs.

Mugilidae fish as bioindicator for monitoring plastic pollution: Comparison between a commercial port and a fishpond (north-western Mediterranean Sea)

In the last decade, interest in monitoring and managing plastic pollution has greatly increased. This study compared levels of microplastic contamination in stomachs of Mugilidae fish, suggesting this family as a target for plastic pollution monitoring in areas with different degrees of anthropisation. Two sites characterised by low and high anthropic impact, a fishpond (S'Ena Arrubia, Italy) and a port (Genoa, Italy), respectively, were compared. This study highlighted a stronger microplastic contamination in the port, with a higher percentage of fish showing the presence of microplastics and a larger polymeric variability compared to the fishpond. The microplastic number in fish from the port was higher than in the literature, but it was not significantly different from S'Ena Arrubia in terms of the microplastic percentage found in single individuals. Biomonitoring of microplastic contamination in Mugilidae fish resulted in a valid tool for the investigation of areas differently affected by human activity.

Recent advances in impacts of microplastics on nitrogen cycling in the environment: A review

Nitrogen cycling plays a decisive role in biogeochemistry, and largely depends on microbial driven nitrogen transformation. The environmental problems caused by microplastics are becoming more serious, and the analysis and control of its pollution in the environment have become a research hotspot in the field. The nitrogen transformation and nitrogen cycling in the environment are mainly driven by microorganisms in the environment, and the existence of microplastics can affect the microbial population, abundance and type, thus affecting the transformation of nitrogen. The effect of microplastics on microorganisms involved in nitrogen transformation is briefly described. This paper mainly reviews the research progress on the impacts of microplastics on nitrogen transformation and nitrogen cycling in water, soil, sediment and sewage sludge. Microplastic type, size and concentration can cause obvious difference in the impacts of microplastics on nitrogen transformation. Then, response and mechanism of microplastics to microorganism mediated nitrogen transformation and nitrogen cycling are introduced. Processes of nitrogen transformation are affected by interfering with microorganism diversity and structure, enzyme activities and related coding genes and oxygen flux. Additionally, additives released from microplastics can also affect the microbial activity. However, mechanisms of microplastics on environmental nitrogen transformation and nitrogen cycling are not fully understood due to the lack of relevant research. There are effective strategies to evaluate complex environmental systems, prolong action time, strengthen multi factor and multi-level research, and assist molecular biology and stable isotope technology. This review article can provide valuable insights into the impact of microplastics on microorganisms mediated nitrogen transformation processes and evaluate the impact on ecological and environmental health.

Combined effects of polystyrene microplastics and cadmium on oxidative stress, apoptosis, and GH/IGF axis in zebrafish early life stages

The toxicological interactions of microplastics (MPs) and heavy metals have been paid much attention in aquatic organism. The mechanisms are not fully clear, particularly in fish early life stages. To the end, zebrafish embryos were exposed to 500 μg/L MPs, 5 μg/L cadmium (Cd), and their combination for 30 days. Body weight, adsorption characteristics of Cd onto MPs, Cd accumulation, oxidative stress, apoptosis, and growth hormone/insulin-like growth factor-I (GH/IGF) axis were examined. Exposure to MPs and Cd alone reduced body weight, which was aggravated by co-exposure. An increase in reactive oxygen species (ROS) levels was observed in larvae exposed to Cd or MPs + Cd, suggesting an induction of oxidative stress. Lipid peroxidation levels were not affected by exposure to MPs and Cd alone but dramatically enhanced by co-exposure, which may be explained by the reduction of total antioxidant capacity (TAOC) and activity levels of Mn-superoxide dismutase (Mn-SOD) and catalase (CAT) after co-exposure. Increased apoptotic cells were observed in the vertebral body of larvae exposed to Cd, the esophagus of larvae exposed to MPs, and both organs of larvae exposed to MPs + Cd, which was further confirmed by changes in the activities of Caspase-3, Caspase-8 and Caspase-9. PCR array on the transcription of genes related to growth, oxidative stress and apoptosis was examined, showing that the combined exposure resulted in greater magnitude of changes than MPs and Cd alone. The results indicate that MPs can enhance the negative effects of Cd on growth, oxidative damage and apoptosis in early life stages of zebrafish. However, the adsorption of Cd onto MPs was not observed and the combined exposure did not increase the Cd content in larvae compared to the single Cd exposure, implying that vector role of MPs in Cd uptake is negligible.

Current status of microplastics pollution in the aquatic environment, interaction with other pollutants, and effects on aquatic organisms

Microplastics, as emerging pollutants, have received great attention in the past few decades due to its adverse effects on the environment. Microplastics are ubiquitous in the atmosphere, soil, and water bodies, and mostly reported in aqueous environment. This paper summarizes the abundance and types of microplastics in different aqueous environments and discusses the interactions of microplastics with other contaminants such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), antibiotics, and heavy metals. The toxicity of microplastics to aquatic organisms and microorganisms is addressed. Particularly, the combined toxic effects of microplastics and other pollutants are discussed, demonstrating either synergetic or antagonistic effects. Future prospectives should be focused on the characterization of different types and shapes of microplastics, the standardization of microplastic units, exploring the interaction and toxicity of microplastics with other pollutants, and the degradation of microplastics, for a better understanding of the ecological risks of microplastics.

Long-Term Occurrence and Fate of Microplastics in WWTPs: A Case Study in Southwest Europe

Microplastic (MP) water pollution is a major problem that the world is currently facing, and wastewater treatment plants (WWTPs) represent one of the main alternatives to reduce the MP release to the environment. Several studies have analysed punctual samples taken throughout the wastewater treatment line. However, there are few long-term studies on the evolution of MPs over time in WWTPs. This work analyses the performance of a WWTP sited in Southwest Europe in relation with annual occurrence and fate of MPs. Samples were monthly taken at different points of the facility (influent, secondary effluent, final effluent, and sludge) and MPs were quantified and characterised by means of stereomicroscopy and FTIR spectrophotometry. The majority of MPs found in wastewater and sludge samples were fragments and fibres. Regarding to the chemical composition, in the water samples, polyethylene (PE), polyethylene terephthalate (PET) and polypropylene (PP) stood out, whereas, in the sludge samples, the main polymers were PET, polyamide (PA) and polystyrene (PS). The MPs more easily removed during the wastewater treatment processes were those with sizes greater than 500 µm. Results showed that the MPs removal was very high during all the period analysed with removal efficiencies between 89% and 95%, so no great variations were found between months. MP concentrations in dry sludge samples ranged between 12 and 39 MPs/g, which represented around 79% of the total MPs removed during the wastewater treatment processes. It is noticeable that a trend between temperature and MPs entrapped in sewage sludge was observed, i.e., higher temperatures entailed higher percentage of retention.

Microplastics aggravate the bioaccumulation and toxicity of coexisting contaminants in aquatic organisms: A synergistic health hazard

There are ongoing controversies regarding the effects of microplastics (MPs) on the bioaccumulation and toxicity of coexisting contaminants in aquatic organisms. This study aims to quantitatively evaluate this issue based on 870 endpoints from 40 publications. It was shown that the presence of MPs significantly increased the bioaccumulation of co-contaminants by 31%, with high statistical power and without obvious publication bias. The aggravated bioaccumulation was also revealed by the strongly positive correlation between bioconcentration factors in the presence and the absence of MPs. Furthermore, the subgroup/regression analyses indicated that the vector effect of MPs on other chemicals was affected by multiple factors and their interactions, such as particle size and exposure time. In addition, a relatively comprehensive biomarker profile was recompiled from included studies to assess the changes in toxicity caused by combined exposure. Results confirmed that the presence of MPs obviously exacerbated the toxicity of co-contaminants by 18%, manifested by the potentiated cytotoxicity, endocrine disruption, immunotoxicity and oxidative stress, implying a synergistic health hazard. Ultimately, the mismatches between laboratory and field conditions were discussed, and the recommendations for future research were offered.

Size Effects of Microplastics on Embryos and Observation of Toxicity Kinetics in Larvae of Grass Carp (Ctenopharyngodon idella)

Microplastics have caused great concern in recent years. However, few studies have compared the toxicity of different sizes of microplastics in fishes, especially commercial fishes, which are more related to human health. In the present study, we revealed the effects of varying sizes of microplastics on grass carp embryos and larvae using scanning electron microscopy (SEM) and fluorescence imaging. Embryos were exposed to 80 nm and 8 μm microplastics at concentrations of 5, 15, and 45 mg/L. Toxicity kinetics of various sizes of fluorescent microplastics were analyzed through microscopic observation in the larvae. Results found that nanoplastics could not penetrate the embryo’s chorionic membrane, instead they conglutinated or aggregated on the chorion. Our results are the first to explore the defense mechanisms of commercial fish embryos against microplastics. Larvae were prone to ingesting their own excrement, resulting in microplastic flocculants winding around their mouth. For the first time, it was found that excreted microplastics could be reconsumed by fish and reaccumulated in the oral cavity. Microplastics of a certain size (1 μm) could be accumulated in the nasal cavity. We speculate that the presence of a special groove structure in the nasal cavity of grass carp larvae may manage to seize the microplastics with a particular size. As far as we know, this is the first report of microplastics being found in the nasal passages of fish. Fluorescence images clearly recorded the toxicity kinetics of microplastics in herbivorous fish.

Ingested microplastics impair the metabolic relationship between the giant clam Tridacna crocea and its symbionts

Microplastics are emerging as widespread pollutants in coral reef ecosystems worldwide; however, there is limited knowledge regarding their impact on giant clams, which are important reef builders. In the present study, the cytological, physiological, and molecular response of the giant clam Tridacna crocea to a 5 d exposure of microplastics was investigated. The concentration of microplastics in the intestine and outer mantle increased significantly and gradually after the exposure to microplastics. There were no significant changes in the density of symbiotic Symbiodiniaceae throughout the exposure period, but symbiont chlorophyll content increased significantly after 1 d of exposure. There was a significant increase in symbiont superoxide dismutase (SOD) activity, but a decrease in giant clam SOD activity and symbiont glutathione S-transferase (GST) activity. No significant changes in catalase (CAT) activity and caspase3 activation level were observed in the two symbiotic partners. Transcriptomic analysis of the giant clam revealed 138 significantly upregulated and 1390 significantly downregulated genes after 5 d of microplastic exposure. The top 20 GO terms overrepresented by these significantly downregulated genes were related to primary metabolic processes and cellular metabolic processes. No significantly upregulated genes were observed in symbionts, but 28 genes were significantly downregulated, including chloroplast oxygen-evolving enhancer, photosystem I reaction center subunit II, peptide/nitrate transporter, sodium-coupled neutral amino acid transporter, beta-glucosidase, and TPA: lipase. These results suggest that T. crocea ingests microplastics through the outer mantle and intestine, and these microplastics can suppress the photosynthesis, organic nutrient transportation, and detoxification ability of the symbionts, as well as the primary metabolism of the giant clam. This eventually could threaten their metabolic relationship and long-term survival.

Dynamics of airborne microplastics, appraisal and distributional behaviour in atmosphere; a review

The use of plastics is common across all aspects of human life owing to its durable and versatile nature. The generation and utilization of plastics are directly related to the anthropogenic activities. The extensive use of plastics and adoption of inappropriate waste-management frameworks has resulted in their release into the environment, where they may persist. Different environmental factors, such as, photochemical, thermo-oxidation, and biological degradation, can lead to the degradation of plastics into micro- (MPs) and nano-plastics (NPs). The behaviour and concentration of MPs in the terrestrial environment can depend on their size, density, and local atmospheric conditions. Microplastics and nanoplastics may enter the food web, carrying various organic pollutants, which bio-accumulate at different trophic levels, prompting organism health concerns. Microplastics being airborne identifies as new exposure route. Dietary and airborne exposure to MPs has led researchers to stress the importance of evaluating their toxicological potential. The primary goal of this paper is to explore the environmental fate of MPs from sources to sink in the terrestrial environment, as well as detail their potential impacts on human health. Additionally, this review article focuses on the presence of airborne microplastics, detailed sample pre-processing methods, and outlines analytical methods for their characterization.

Microplastic contamination in Great Lakes fish

Freshwater ecosystems, generally adjacent to human population and more contaminated relative to adjacent marine ecosystems, are vulnerable to microplastic contamination. We sampled 7 species of fish from Lake Ontario and Lake Superior and assessed their gastrointestinal (GI) tracts to quantify ingested microplastics and other anthropogenic particles. A subset of the microparticles were chemically analyzed to confirm polymer types and anthropogenic origins. We documented the highest concentration of microplastics and other anthropogenic microparticles ever reported in bony fish. We found 12,442 anthropogenic microparticles across 212 fish (8 species) from nearshore Lake Ontario, 943 across 50 fish (1 species) from Humber River, and 3094 across 119 fish (7 species) from Lake Superior. Fish from Lake Ontario had the greatest mean abundance of anthropogenic microparticles in their GI tracts (59 particles/fish [SD 104]), with up to 915 microparticles in a single fish. Fish from Lake Superior contained a mean [SD] of 26 [74] particles/fish, and fish from Humber River contained 19 [14] particles/fish. Most particles were microfibers. Overall, ≥90% of particles were anthropogenic, of which 35-59% were microplastics. Polyethylene (24%), polyethylene terephthalate (20%), and polypropylene (18%) were the most common microplastics. Ingestion of anthropogenic particles was significantly different among species within Lake Ontario (p < 0.05), and the abundance of anthropogenic particles increased as fish length increased in Lake Ontario (ρ = 0.62). Although we cannot extrapolate the concentration of microplastics in the water and sediments of these fish, the relatively high abundance of microplastics in the GI tracts of fish suggests environmental exposure may be above threshold concentrations for risk.

Potential microplastics impacts on African fishing resources

Microplastic (MP) pollution is increasing worldwide and affecting aquatic fauna in different ways, which endangers current aquatic resources in a still unknown extent. MP-induced threats to marine fauna are critical for developing countries, where waste treatment may be not optimal and coastal communities rely heavily on marine resources for dietary protein. In this study, we assess the importance of MP pollution for African fishing resources. A new meta-database was created from published studies, containing 156 samples with more than 6200 individuals analysed for microplastic content from African and adjacent waters. A combination of research landscape analysis and rank analysis served to identify main research targets and to determine regional fishing resources especially affected by MP. A network of relevant terms showed fish health as a concern in Mediterranean waters, environmental pollution in freshwater and an emphasis on plastic items in South Africa. MP contents in fishing resources from Nile countries and the Gulf of Guinea, followed by Tunisia, are significantly higher than in other regions. Some of the most exploited species are among the most polluted ones, highlighting the threat of MP pollution in valuable but already compromised African fishing resources. Large geographic gaps with almost absent data about MP in aquatic fauna were revealed, especially in freshwater and in East African coasts. These results emphasize the importance of increasing the coverage of MP pollution in African fishing resources, and improving plastic waste management in the continent.

Effect of microplastics on Yersinia ruckeri infection in rainbow trout (Oncorhynchus mykiss)

Exposure to microorganisms such as Yersinia ruckeri can significantly affect bacterial infections in fish. Microplastics (MPs) may predispose fish to infection and act as carriers in pathogen transmission. Therefore, this study is designed to evaluate MPs' effect on damage caused by exposure to Y. ruckeri in rainbow trout. In this study, blood biochemical parameters and hepatic oxidative biomarkers as clinical signs were measured in the fish co-exposed to Y. ruckeri (5 and 10% the median lethal dose (LD₅₀)) and MPs (500 and 1000 mg Kg^-1) for 30 days. There were no significant changes in the creatinine, triglyceride, cholesterol levels, and glutamic-pyruvic transaminase activity in the blood of fish infected with Y. ruckeri. In contrast, exposure to MPs had a significant effect on most clinical parameters. The total protein, albumin, globulin, total immunoglobulins, high-density lipoprotein, low-density lipoprotein, cholesterol levels, and γ-glutamyltransferase activity decreased, whereas glucose, triglyceride, and creatinine levels, and glutamic-oxaloacetic transaminase, glutamic-pyruvic transaminase, alkaline phosphatase, and lactate dehydrogenase activities increased in the plasma of fish after co-exposure to MPs and Y. ruckeri. Dietary MPs combined with a Y. ruckeri challenge decreased catalase and glutathione peroxidase activities, and total antioxidant levels. However, superoxide dismutase activity and malondialdehyde contents increased in the hepatocyte of fish co-exposed to MPs and Y. ruckeri. This study suggests that fish exposure to MPs and simultaneous challenge with Y. ruckeri could synergistically affect clinical parameters.

Micro/nano-plastics occurrence, identification, risk analysis and mitigation: challenges and perspectives

Micro/nanoplastics (MP/NPs) are emerging global pollutants that garnered enormous attention due to their potential threat to the ecosystem in virtue of their persistence and accumulation. Notably, United Nations Environment Programme (UNEP) yearbook in 2014 proposed MPs as one among ten emergent issues that the Earth is facing today. MP/NPs can be found in most regularly used products (primary microplastics) or formed by the fragmentation of bigger plastics (secondary microplastics) and are inextricably discharged into the environment by terrestrial and land-based sources, particularly runoff. They are non-degradable, biologically incompatible, and their presence in the air, soil, water, and food can induce ecotoxicological issues and also a menace to the environment. Due to micro size and diverse chemical nature, MP/NPs easily infiltrate wastewater treatment processes. This communication reviews the current understanding of MP/NPs occurrence, mobility, aggregation behavior, and degradation/assimilation in terrestrial, aquatic (fresh & marine), atmospheric depositions, wetlands and trophic food chain. This communication provide current perspectives and understanding on MP/NPs concerning (1) Source, occurrence, distribution, and properties (2) Impact on the ecosystem and its services, (3) Techniques in detection and identification and (4) Strategies to manage and mitigation.

Impact of polypropylene microplastics and chemical pollutants on European sea bass (Dicentrarchus labrax) gut microbiota and health

Plastic pollution has become a global problem for marine ecosystems. Microplastics (MPs) are consumed by several marine organisms, including benthic and pelagic fish species that confuse them with food sources, thus contributing to bioaccumulation along the food chain. In addition to structural intestinal damage, ingestion of MPs represents a pathway for fish exposure to potentially hazardous chemicals, too. Most of them are endocrine disrupters, genotoxic or induce immune depression in fish. Accordingly, we assessed the combined toxicological effects of microplastics (MPs) and adsorbed pollutants by adding them to marine fish diet. European sea bass (Dicentrarchus labrax) juveniles were fed for 60 days with feeds containing polypropylene MPs, either virgin or contaminated with chemical pollutants (a blend of dichlorodiphenyldichloroethylene, chlorpyrifos, and benzophenone-3). The data demonstrated a synergic action of MPs and chemical pollutants to induce an inflammatory-like response in distal intestine of sea bass as shown by the up regulation of cytokine il-6 and tnf-α expression. Morphological analysis detected the presence of a focus of lymphocytes in anterior and posterior intestinal segments of fish fed with contaminants in the diet. With regard to microbiota, significant changes in bacterial species richness, beta diversity, and composition of gut microbiota were observed as a consequence of both pollutants and polluted MPs ingestion. These perturbations in gut microbial communities, including the reduction of beneficial lactic acid bacteria and the increase in potential pathogenic microorganism (Proteobacteria and Vibrionales), were undeniable signs of intestinal dysbiosis, which in turn confirmed the signs of inflammation caused by pollutants, especially when combined with MPs. The results obtained in this study provide, therefore, new insights into the potential risks of ingesting MPs as pollutant carriers in marine fish.

Microplastics (Polystyrene) Exposure Induces Metabolic Changes in the Liver of Rare Minnow (Gobiocypris rarus)

Microplastics are environmental contaminants and an emergent concern. Microplastics are abundant in freshwater and can cause biochemical stress in freshwater organisms. In the current study, rare minnows (Gobiocypris rarus) were exposed to 1μm polystyrene microplastics at 200 μg/L concentration. We observed various sublethal effects after four weeks of exposure but no mortality. Numerous cellular and tissue alterations were observed in the liver. Differential metabolites and differentially expressed genes between control and exposure groups were identified and mapped to pathways in the Kyoto Encyclopedia of Genes and Genomes. The combination of transcriptomic and metabolomic analyses revealed significantly varied metabolic pathways between the two groups. These pathways were involved in glucolipid, amino acid, and nucleotide metabolism. Results demonstrated that MP exposure induced immune reaction, oxidative stress, and disturbed glycolipid and energy metabolism. The current study provided novel insights into the molecular and metabolic mechanisms of microplastic ecotoxicology in rare minnow.

Spatial distribution of microplastics in Chinese freshwater ecosystem and impacts on food webs

Over the past two decades, there has been a lot of discussion about the rapid increase of microplastics (MPs) due to their persistence, ubiquity, and toxicity. The widespread distribution of MPs in various freshwater ecosystems makes them available for different trophic levels biota. The ingestion and trophic transfer of MPs may induce potential impacts on freshwater food webs. Therefore, this systematic review is an in-depth review of 51 recent studies to confirm the spatial distribution of MPs in the Chinese freshwater ecosystem including water, sediment and biota, exposure pathways, and impacts on freshwater food webs. The result suggested the white, transparent and colored, Polypropylene (PP) and Polyethylene (PE) of <1 mm fibers were dominant in Chinese freshwaters. The uptake of MPs by various freshwater organisms as well as physiological, biological and chemical impacts on food webs were also elucidated. At last, some limitations were discussed for future studies to better understand the effects of MPs on food webs.

Suspected microplastics in Atlantic horse mackerel fish (Trachurus trachurus) captured in Portugal

Microplastics have been found in fish, but most studies have focused on the digestive system without considering additional organs. Herein, the objective was to assess the presence of microplastics in internal organs (gills, guts, kidney, heart) of the Atlantic horse mackerel (Trachurus trachurus) captured of the coast of Portugal (Northeast Atlantic Ocean). Suspected microplastics were present in all organs, with particles of larger size (i.e., equivalent diameter) found in the gut and those of lower size in the heart and its luminal blood. Suspected microplastics of 1-10 μm were the most abundant (65.4%), more likely to translocate, owing to their minute size, but more difficult to properly characterize. These results highlight the need to expand the analytical work on organs and tissues for assessing microplastics in organisms, but also emphasize the actual need for developing analytical methods that allow for an accurate isolation, identification, and characterization of microplastics in biota.

The first observation of the presence of microplastics in wild common bleak (Alburnus alburnus L.) and standardization of extraction protocols

The presence of microplastics (MPs) in the gastrointestinal tract, muscle, and whole-body samples of common bleak Alburnus alburnus L. from Gruža Reservoir (Central Serbia) was studied for the first time. Different protocols for MPs extraction were applied to determine the most efficient one. The study aimed to modify existing protocols to be cost-effective, efficient in digestion, and with no detrimental effect on potentially present MPs polymers. In this study, the digestion with 10% KOH during 48 h at 40°C was efficient for the gastrointestinal tract and muscle. Digestion with 10% KOH during 72 h at 40°C was the most efficient for whole-body samples. The usage of NaClO proved successful in digestion of the gastrointestinal tract overnight at room temperature. Fibers detected in the samples are assumed to be of plastic origin. The general goal was to establish a protocol for extracting MPs from fish tissue in wild populations to obtain results and determine the degree of pollution.

Occurrence of microplastics in the gastrointestinal tract of benthic by-catches from an eastern Mediterranean deep-sea environment

Concern about microplastic pollution little is known about levels in deep-sea species; to fill this knowledge gap, levels of microplastics in the gastrointestinal (GI) tracts of 34 fish from eight different deep-sea by-catches: blackmouth catshark, lesser spotted dogfish, and velvet belly, armless snake eel, hollowsnout grenadier, phaeton dragonet, royal flagfin, and slender snipe eel were measured. All were collected at the same site (east Sardinia, Mediterranean Sea; 40°10'12.49″N, 9°44'12.31″E) using a bottom gillnet at depths between -820/250 and -1148 ft./350 m. Microplastics (MPs) were retrieved in 16 out of 34 fish. At least one microplastic item was found in 48% (33%, E. spinax - 75%, G. melastomus) of the samples. The most frequent was polyethylene (PE), with nine items (filaments, films, fragments) found in five specimens. This preliminary study of by-catches adds new data on MPs ingestion by species inhabiting a deep-sea environment of the Mediterranean.

The prevalence and potential implications of microplastic contamination in marine fishes from Xiamen Bay, China

The wide presence of microplastics (MPs) in the ocean leads their exposure on marine fish. MP contamination was reported for the gastrointestinal tracts and gills of 117 marine fishes attributed to nine species from Xiamen Bay, a special economic zone in China. Among species, MP abundance ranged from 1.07 items individual^-1 to 8.00 items individual ^-1. Fibers dominated MP shapes, accounting for 59.03% of all MPs. Polymer composition was dominated by polyamide (26.97%) and rayon (17.56%). MPs were most commonly (55.22%) transparent, and most (77.61%) were < 1 mm in size. Our report represents the first of MP contamination in wild marine fish from Xiamen Bay, which we determine to be at an intermediate to slightly higher level compared with levels reported elsewhere, and provides further insights into potential risks of MPs pose to fish and human health.

Microplastics and trace metals in fish species of the Gulf of Mannar (Indian Ocean) and evaluation of human health

The importance of microplastic (MPs) contamination in marine environments is reflected by increasing number of studies in fish species. Some even dedicated to the toxicological effects from the ingestion. Microplastics (MPs) and their trace metal composition were examined in the muscle and intestine of five commercially important fish species (i.e., Sufflamen fraenatus, Heniochus acuminatus, Atropus atropos, Pseudotriacanthus and Leiognathus brevirostris) from Thoothukudi at the Gulf of Mannar coast in south India. The abundance and morphology of MPs (size, shape, and texture) in muscle and intestinal were investigated by micro-Fourier Transform Infrared Spectroscopy (μ-FT-IR) and atomic force microscope (AFM). ICP-OES was used to investigate the adsorption/leaching of trace metals in microplastics in order to assess health risk for adults and children. Particles of 100-250 μm and white color dominated, and the mean abundances (items/100 g) of total MPs were more in Pseudotriacanthus (muscle: 51.2; intestine: 50.1) compared to Heniochus acuminatus (muscle: 9.6; intestine: 15), Leiognathus brevirostris (muscle: 12; intestine: 13.2) and Atropus atropus (muscle: 15.2; intestine: 44.1). Polyethylene (35.3%), polypropylene (27.2%), polyamide (nylon) (22.2%) and fiber (15.3%) represented the MPs present in muscles, and polyamide (nylon) (30.2%), polyethylene (28.1%), polypropylene (25.9%), and fiber (15.8%) composed the intestine MPs. We estimated possible consumption of 121-456 items of MPs/week by adults and about 19-68 items of MPs/week by children by considering the sizes of safe meals. Zn, Cu, Mn and Cr in these fish species reflected influence of the sewage waste. However, the non-carcinogenic risk evaluated through EDI, THQ, HI, and CR did not suggest any immediate health problem for the consumers.

Using Infrared Photothermal Heterodyne Imaging to Characterize Micro- and Nanoplastics in Complex Environmental Matrices

A key challenge for addressing micro- and nanoplastics (MNPs) in the environment is being able to characterize their chemical properties, morphologies, and quantities in complex matrices. Current techniques, such as Fourier transform infrared spectroscopy, provide these broad characterizations but are unsuitable for studying MNPs in spectrally congested or complex chemical environments. Here, we introduce a new, super-resolution infrared absorption technique to characterize MNPs, called infrared photothermal heterodyne imaging (IR-PHI). IR-PHI has a spatial resolution of ∼300 nm and can determine the chemical identity, morphology, and quantity of MNPs in a single analysis with high sensitivity. Specimens are supported on CaF₂ coverslips under ambient conditions from where we (1) quantify MNPs from nylon tea bags after steeping in ultrapure water at 25 and 95 °C, (2) identify MNP chemical or morphological changes after steeping at 95 °C, and (3) chemically identify MNPs in sieved road dust. In all cases, no special sample preparation was required. MNPs released from nylon tea bags at 25 °C were fiber-like and had characteristic IR frequencies corresponding to thermally extruded nylon. At 95 °C, degradation of the nylon chemical structure was observed via the disappearance of amide group IR frequencies, indicating chain scission of the nylon backbone. This degradation was also observed through morphological changes, where MNPs altered shape from fiber-like to quasi-spherical. In road dust, IR-PHI analysis reveals the presence of numerous aggregate and single-particle (<3 μm) MNPs composed of rubber and nylon.

Microplastics as contaminants in Indian environment: a review

The increased production and consumption scale of plastic items has led to the generation of microplastics (MPs), an emerging class of contaminants, in our environment. MPs are plastic particles less than 5 mm in size and could originate due to primary and secondary sources. The primary ones are generated as such in the MP size range while the secondary MPs are a result of fragmentation of larger plastic particles which eventually enters the aquatic, terrestrial and atmospheric environments. The increasing concern of MP pollution in every compartment of our environment is being globally explored, with relatively fewer studies in India. Among the total studies published on MP prevalence in the Indian environments, marine systems have received significantly higher attention compared to the other compartments like freshwater, atmosphere, terrestrial and human consumables. This review article is an effort to present current understanding of MP pollution in aquatic systems, terrestrial systems, atmosphere and human consumables of India by reviewing available scientific literature. Along with this, the review also focuses on identification of the gap areas in current knowledge and highlights way forward for future research. This would further help in meeting the goals of this emergent pollutant management.

Effect of light irradiation on heavy metal adsorption onto microplastics

Microplastics are frequently found in many environmental media. Polypropylene (PP) is one of the plastics commonly used, resulting in more and more PP fragments in natural waters. Contaminants, such as lead (Pb), could get adsorbed onto microplastics after the exposure to sunlight, and pose a larger threat to aquatic species. In this study, the oxidative indices of PP pellets after different exposure times to a Xenon lamp were evaluated by Fourier transform infrared (FTIR) and energy-dispersive X-ray spectrometry. The results show that the percentage of oxygen content increased from 2.80 to 20.95 wt% and changes of characteristic peaks of the FTIR pattern, implying that the exposure to the Xenon lamp could initiate oxidation. Due to the changes of functional groups after the exposure to the Xenon lamp for 28 days, the adsorption capacities of the PP pellets were up to 274.4 mg⋅kg^-1, 1.7 to 2.5 times higher than that of the raw PP pellets depending on the solution pHs. The adsorption behavior can be described by a pseudo-second-order model with rate constants of adsorption of 0.00212-0.01404 kg⋅mg^-1⋅h^-1. The increase of adsorption capacity due to changes of the PP pellets after the Xenon lamp exposure increased the potential risk to the aquatic species.

Microplastic distribution, abundance, and composition in the sediments, water, and fishes of the Red and Mediterranean seas, Egypt

This study records the extent of microplastics (MPs) in the surface water, sediments, and fishes of the Mediterranean and Red seas in Egypt. In sediment and water samples, the Ras Gharib station in the Red sea and Damietta and Port Said stations in the Mediterranean sea exhibited the highest microplastic abundance, while the lowest concentration was found in the Ain Sukhna station in the Red Sea and Marsa Matruh station in the Mediterranean sea. Rayon and polyethylene terephthalate were the most frequently found polymers in fishes. The results highlighted the abundant existence of microplastics in sediments, water, and fishes of the Mediterranean and Red seas, thereby improving our understanding of the environmental risks posed by microplastics to fisheries and marine ecosystems and the need for measures to diminish the flux of plastics to the marine settings.