Does the presence of microplastics influence the acute toxicity of chromium(VI) to early juveniles of the common goby (Pomatoschistus microps)? A study with juveniles from two wild estuarine populations

The effect of different types of microplastic and acute cadmium exposure on the Mytilus galloprovincialis (Lamarck, 1819)

Microplastic (MP) pollution is a pressing issue for both environmental health and the safety of human food sources. This study provides a comprehensive analysis of the effects of MPs on Mediterranean mussels (Mytilus galloprovincialis, Lamarck 1819), focusing on the food safety risks associated with MP and cadmium (Cd) exposure in these organisms intended for consumption. The retention of different polymer types of MPs in mussels was specifically evaluated, and the influence of Cd on MP retention across these polymers was investigated. Mussels were exposed to polystyrene (PS), polypropylene (PP), and polyethylene terephthalate (PET) MPs individually and in combination with the toxic metal Cd for a duration of 7 days. Antioxidant enzymes, oxidative stress parameters, and digestive system enzyme activities, selected as biomarkers for Cd and MPs pollution, were assessed. Furthermore, human consumption risk evaluations and limits regarding mussel intake were analysed in terms of food safety. The results suggest that exposure to Cd, MPs, or their combination induces oxidative stress, tissue damage, and neurotoxicity. Alterations in digestive enzyme activities could impact the mussels' energy acquisition from food and their capacity to conserve energy reserves. The estimated daily intake (EDI), provisional tolerable weekly intake (PTWI), target hazard quotient (THQ), and target cancer risk (TCR) levels for all groups surpassed established limits, implying a significant health risk for humans consuming these products. These results underscore the potential health risks for humans associated with consuming mussels exposed to Cd and/or MPs and provide valuable data for monitoring pollution levels and ecological risks in aquatic organisms. Additionally, our findings reveal that the retention of Cd in mussel tissues varies significantly after exposure, with combinations of PET and Cd showing lower levels of Cd accumulation compared to other groups, suggesting a differential interaction that influences Cd retention.

Response and adaptation mechanisms of Apostichopus japonicus to single and combined anthropogenic stresses of polystyrene microplastics or cadmium

Microplastics (MPs) have become pervasive in marine ecosystems, exerting detrimental effects on marine life. The concurrent presence and interaction of MPs and heavy metals in aquatic environments could engender more insidious toxicological impacts. This study aimed to elucidate the potential impacts and underlying mechanisms of polystyrene microplastics (PS-MPs), cadmium (Cd), and their combined stress (MPs-Cd) on sea cucumbers (Apostichopus japonicus). It focused on the growth, Cd bioaccumulation, oxidative stress responses, immunoenzymatic activities, and metabolic profiles, specifically considering PS-MPs sizes preferentially ingested by these organisms. The high-dose MPs (MH) treatment group exhibited an increase in cadmium bioavailability within the sea cucumbers. Exposure to PS-MPs or Cd triggered the activation of antioxidant defenses and immune responses. PS-MPs and Cd exhibited a synergistic effect on lysozyme (LZM) activity. A total of 149, 316, 211, 197, 215, 619, 434, and 602 differentially expressed metabolites were identified, distinguishing the low-dose MPs (ML), high-dose MPs (MH), low-dose Cd (LCd), low-dose MPs and low-dose Cd (MLLCd), high-dose MPs and low-dose Cd (MHLCd), high-dose Cd (HCd), low-dose MPs and high-dose Cd (MLHCd), high-dose MPs and high-dose Cd (MHHCd) groups, respectively. Metabolomic analyses revealed disruptions in lipid metabolism, nervous system function, signal transduction, and transport and catabolism pathways following exposure to PS-MPs, Cd, and MPs-Cd. Correlation analyses among key differentially expressed metabolites (DEMs) underscored the interregulation among these metabolic pathways. These results offer new perspectives on the distinct and synergistic toxicological impacts of microplastics and cadmium on aquatic species, highlighting the complex interplay between environmental contaminants and their effects on marine life.

Phthalocyanine blue leaching and exposure effects on Microcystis aeruginosa (cyanobacteria) of photoaged microplastics

Light-stabilizing additives may contribute to the overall pollution load of microplastics (MPs) and potentially enter the food chain, severely threatening aquatic life and human health. This study investigated the variation between polystyrene (PS) MPs and phthalocyanine blue (CuPC)-containing MPs before and after photoaging, as well as their effects on Microcystis aeruginosa. The presence of PS-MPs increased cell mortality, antioxidant enzyme activity, and the variation in extracellular components, while the presence of CuPC exacerbated these variations. CuPC-containing MPs caused different increasing trends in superoxide dismutase and malondialdehyde activities due to electron transfer across the membrane. Transcriptomic analysis revealed that the MPs and CuPC affected various cellular processes, with the greatest impact being on cell membranes. Compared with MPs, CuPC negatively affected ribosome and polysaccharide formation. These findings provide insights into the molecular mechanisms underlying the cellular response to MPs and their associated light-stabilizer pollution and imply the necessity for mitigating the pollution of both MPs and light-stabilizers.

A realistic combined exposure scenario: effect of microplastics and atrazine on Piaractus mesopotamicus

Microplastics, considered emerging environmental contaminants resulting from plastic degradation, are discovered in diverse aquatic ecosystems and can be unintentionally ingested by fish. Therefore, it is essential to characterize their interaction with other contaminants, such as agrochemicals, in aquatic environments. This study aimed to assess histological, enzymatic, and genotoxic biomarkers in juvenile pacú (Piaractus mesopotamicus) exposed to polyethylene (PE) microplastic particles and the herbicide atrazine, individually or combined, for 15 days. Four treatments were used: a negative control (CON), PE in the fish diet (0.1% w/w, FPE), atrazine through water (100 μg L-1, ATZ), and the mixture (ATZ+FPE). Results confirmed histological alterations in gills (edema and lamellar fusion) and liver (necrotic areas and congestion) of fish exposed to ATZ and ATZ+FPE. The number of goblet cells increased in the posterior intestine of fish under ATZ+FPE compared to CON and FPE. Enzyme activities (CAT, GST, AChE, and BChE) significantly increased in ATZ+FPE compared to CON. However, no genotoxic effect was demonstrated. These findings provide insights into the complex impacts of simultaneous exposure to atrazine and microplastics, emphasizing the need for continued research to guide effective environmental management strategies against these contaminants that represent a risk to aquatic organisms.

Accumulation of polyethylene microplastics in river biofilms and effect on the uptake, biotransformation and toxicity of the antimicrobial triclosan

The interaction of multiple stressors in freshwater ecosystems may lead to adverse effects on aquatic communities and their ecological functions. Microplastics (MPs) are a class of contaminants of emerging concern that can exert both direct and indirect ecotoxicological effects. A growing number of studies have investigated MPs-attached microbial communities, but the interaction between MPs and substrate-associated biofilm (i.e., on natural river substrates, such as stones and sediments) remains poorly studied. In this work, the combined effects of polyethylene MPs (PE-MPs) with a particle size of 10-45 μm (2 mg/L) and the antimicrobial triclosan (TCS) (20 μg/L) were investigated on river biofilms through a short-term exposure experiment (72 h). To the best of authors' knowledge, this is the first time that the combined effects of MPs and chemical contaminants in substrate-associated river biofilms were assessed. Different response parameters were evaluated, including (i) exposure assessment and ii) contaminants effects at different levels: bacterial community composition, antibiotic resistance, extracellular polymeric substances (EPS), photosynthetic efficiency (Yeff), and leucine aminopeptidase activity (LAPA). Triclosan was accumulated in river biofilms (1189-1513 ng/g dw) alongside its biotransformation product methyl-triclosan (20-29 ng/g dw). Also, PE-MPs were detected on biofilms (168-292 MP/cm2), but they had no significant influence on the bioaccumulation and biotransformation of TCS. A moderate shift in bacterial community composition was driven by TCS, regardless of PE-MPs co-exposure (e.g., increased relative abundance of Sphingomonadaceae family). Additionally, Yeff and EPS content were significantly disrupted in TCS-exposed biofilms. Therefore, the most remarkable effects on river biofilms were related to the antimicrobial TCS, whereas single PE-MPs exposure did not alter any of the evaluated parameters. These results demonstrate that biofilms might act as environmental sink of MPs. Although no interaction between PE-MPs and TCS was observed, the possible indirect impact of other MPs-adsorbed contaminants on biofilms should be further assessed.

Distribution characteristics and ecological risk assessment of microplastics in intertidal sediments near coastal water

Plastic products are widely distributed worldwide and continue to have a negative impact on the environment and organisms. Intertidal regions, which interface between upland and marine ecosystems, are regions of high ecological importance and serve as repositories for a variety of plastic wastes. However, ecological risk assessments of microplastics (MPs) in these transitional environments are still scarce. In this study, the morphological characteristics and spatial distribution of MPs in the intertidal surface sediments of Haizhou Bay were analyzed, and an ecological risk assessment framework for MPs was developed. Overall, the average abundance of MPs in the sediments was 2.31 ± 1.35 pieces/g dw. The size of the MPs was mainly less than 1 mm, and the main shape, color and polymer type of the MPs were mainly fibrous (58%), blue (30%), and PVC (22%), respectively. Cluster analyses showed that the sites could be well distinguished by size and polymer type but not by MP shape and color. According to the hazard scores, most of the sites in this area belonged to a risk level of IV, while the pollution loading index (PLI) showed that most of the sites belonged to a risk level of II. The ecological toxicity risk from the species-sensitive distribution (SSD) model showed that one-third of the sites had ecological MPs toxicity risks to marine organisms. We believe that normalized and standardized assessment methods should be implemented to monitor and manage the risk of MPs in the intertidal sediments. Particularly, the multiple dimensions, standard abundance of MPs, as well as MPs ingestion in the intertidal organisms, should be fully considered in the next step.

Insight into microplastics in the aquatic ecosystem: Properties, sources, threats and mitigation strategies

Globally recognized as emergent contaminants, microplastics (MPs) are prevalent in aquaculture habitats and subject to intense management. Aquaculture systems are at risk of microplastic contamination due to various channels, which worsens the worldwide microplastic pollution problem. Organic contaminants in the environment can be absorbed by and interact with microplastic, increasing their toxicity and making treatment more challenging. There are two primary sources of microplastics: (1) the direct release of primary microplastics and (2) the fragmentation of plastic materials resulting in secondary microplastics. Freshwater, atmospheric and marine environments are also responsible for the successful migration of microplastics. Until now, microplastic pollution and its effects on aquaculture habitats remain insufficient. This article aims to provide a comprehensive review of the impact of microplastics on aquatic ecosystems. It highlights the sources and distribution of microplastics, their physical and chemical properties, and the potential ecological consequences they pose to marine and freshwater environments. The paper also examines the current scientific knowledge on the mechanisms by which microplastics affect aquatic organisms and ecosystems. By synthesizing existing research, this review underscores the urgent need for effective mitigation strategies and further investigation to safeguard the health and sustainability of aquatic ecosystems.

Environmental relevant concentrations of polystyrene nanoplastics and lead co-exposure triggered cellular cytotoxicity responses and underlying mechanisms in Eisenia fetida

Heavy metal pollution of soils and the widespread use of plastics have caused environmental problems worldwide. Nanoplastics (NPs) contaminants in water and soil environments can adsorb heavy metals, thereby affecting the bioavailability and toxicity of heavy metals. In this paper, the effect of co-exposure of polystyrene microspheres with 100 nm particle size and lead acetate (Pb) on the Eisenia fetida coelomocytes was investigated. The environmental concentration of NPs used was 0.01 mg/L and the concentration of Pb ranged from 0.01 to 1 mg/L, and the exposed cells were incubated at 298 k for 24 h. Our study demonstrated that exposure of cells to environmental relevant concentrations of NPs did not significantly affect the cytotoxicity of Pb exposure. It was shown that co-exposure induced cellular production of reactive oxygen species (ROS, increased to 134.4 %) disrupted the antioxidant system of earthworm body cavity cells, activated superoxide dismutase and catalase (CAT), produced reduced glutathione, and inhibited glutathione-dependent enzyme (GST) activity (Reduced to 64 %). Total antioxidant capacity (T-AOC) is first enhanced against ROS due to the stress of NPs and Pb. When the antioxidant reserves of cells are exhausted, the antioxidant capacity will decrease. The level of malondialdehyde, a biomarker of eventual lipid peroxidation, increased to 231.7 %. At the molecular level, due to co-exposure to NPs and Pb, CAT was loosely structured and the secondary structure is misfolded, which was responsible for exacerbating oxidative damage in E. fetida coelomocytes. The findings of this study have significant implications for the toxicological interaction and future risk assessment of co-contamination of NPs and Pb in the environment.

Single and combined effects of CuSO4 and polyethylene microplastics on biochemical endpoints and physiological impacts on the narrow-clawed crayfish Pontastacusleptodactylus

This study investigated the toxicity of polyethylene microplastics (MPs; <0.02 mm) and CuSO4, alone and in combination, on the freshwater crayfish Pontastacus leptodactylus. In this study, the crayfish were exposed to PE-MPs (0.0, 0.5, and 1 mg L-1) and CuSO4·5H2O (0.0, 0.5, and 1 mg L-1) for a period of 28 days. Next, multi-biomarkers, including biochemical, immunological, and oxidative stress indicators were analyzed. Results showed that co-exposure to PE-MPs and CuSO4 resulted in increased aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), and decreased alkaline phosphatase (ALP), butyrylcholinesterase (BChE), and gamma-glutamyl-transferase (GGT). Triglycerides, cholesterol, glucose, and albumin content also increased. Although no significant change was observed in lysozyme and phenoloxidase activities in crayfish co-exposed to 0.5 mg L-1 MPs and 0.5 mg L-1 CuSO4, their activities were significantly decreased in other experimental groups. Oxidative stress parameters in hepatopancreas indicated increased superoxide dismutase (SOD), glutathione peroxidase (GPx), and in malondialdehyde (MDA) levels, but decreased catalase (CAT), glucose 6-phosphate dehydrogenase (G6PDH), and cellular total antioxidant (TAC). Results showed that the sub-chronic toxicity of CuSO4 was confirmed. The study confirmed the toxicity of CuSO4 and found that higher concentrations led to more severe effects. Co-exposure to PE-MPs and CuSO4 primarily compromised the endpoints, showing increased toxicity when both pollutants were present in higher concentrations. The activities of POX, LYZ, ALP, GGT, LDH, and CAT were suppressed by both CuSO4 and MPs. However, a synergistic increase was observed in other measured biomarkers in crayfish co-exposed to CuSO4 and MPs.

Toxicity of co-exposure of microplastics and lead in African catfish (Clarias gariepinus)

Microplastics (MPs) are an emerging threat to freshwater ecosystems with several ecotoxicological ramifications for fish. Microplastics (MPs) can adsorb heavy metals on their surfaces and increase their availability to aquatic organisms. The combined impact of lead and microplastics on fish has only been studied seldom utilizing a variety of markers. The present study aimed to evaluate the hematological, biochemical, and inflammatory signals (cytokines), as well as antioxidant enzymes in African catfish (Clarias gariepinus) exposed to lead (Pb) and MPs individually and combined for 15 days (acute toxicity experiment). The fish were split into four groups, the first of which was the control group. The second group received exposure to 1 mg/L of lead nitrate [Pb(NO3)2]. The third group was given 100 mg/L of MPs. A solution containing 100 mg/L of MPs and 1 mg/L of lead nitrate [Pb(NO3)2] was administered to the fourth group (the combination group). According to the findings, when MPs and Pb were combined for 15 days, the red blood cells (RBCs), thrombocytes, and lymphocytes were significantly reduced in comparison to the control fish. When compared to the control fish, the fish exposed to MPs and Pb alone or together showed a significant rise in blood interleukin-1β (IL-1β) and interleukin-6 (IL-6) cytokines. Both MPs and Pb exposure in catfish resulted in significant changes in the plasma electrolytes. The fish treated with MPs and Pb individually or in combination showed significant reduction in superoxide dismutase (SOD) and total antioxidant capacity (TAC) levels compared to the control group. The fish exposed to the combined action of MPs and Pb showed a considerable modification in all biochemical markers. The difference in the mean concentration of Pb (mg/L) between the fish exposed to Pb alone and the fish subjected to Pb and MPs combination was not statistically significant. In conclusion, according to this investigation, exposure to Pb caused an insignificant increase in Pb accumulation when MPs were present. However, co-exposure may result in anemia, cellular harm, extremely high levels of oxidative stress, and an inflammatory reaction.

Chromium (IV) transfer to Amusium pleuronectes by LDPE microplastics: An experimental study

An experiment was carried out to investigate the potential of virgin LDPE microplastics to transfer heavy metals. Desired shapes (fibres, fragments, and films) and sizes (< 5 mm) of virgin LDPE microplastics were immersed in a known concentration (30 µg/l) of chromium (IV). These Cr-coated microplastics were introduced into a culture tank containing edible scallops (Amusium pleuronectes). After the completion of the experiment (5 days), the sediments in the culture tank and edible tissues of A. pleuronectes were tested for the presence of Cr. In the sediments, a maximum concentration of 1.934 µg/g of Cr was accumulated at a rate of R2 = 0.979, while in the tissues, the maximum accumulation concentration was 0.733 µg/g of Cr at a rate of R2 = 0.807. Energy Dispersive X-ray Spectroscopy analysis also confirmed the presence of Cr (2.61 ± 0.44 mass % and 1.80 ± 0.30 atom%) in the tissues of A. pleuronectes, which was absent in the control tissues. The study showed that when exposed to contaminants such as heavy metals, LDPE microplastics can adhere and transfer them to biotic tissues. LDPE showed the potential to transfer adhered contaminants; however, the effects caused by these transferred contaminants on biota must be studied further. Risk assessment study showed that potential ecological risk of Cr is < 40 indicating low risk however, the combined effect of Cr and LDPE can compound its toxicity which needs to be studied further.

Size matters either way: Differently-sized microplastics affect amphibian host and symbiotic microbiota discriminately

Concerns about the implications of microplastics (MPs) on aqueous animals have gained widespread attention. It has been postulated that the magnitude of MPs can influence its toxicity. However, little is known about how MPs toxicity changes with particle size. Amphibians are reliable bioindicators of ecosystem health due to their complex life cycles. In this study, we compared the influences of two sizes nonfunctionalized polystyrene microspheres (1 and 10 μm) on the metamorphosis of Asiatic toad (Bufo gargarizans). Acute exposure to MPs at high concentrations led to bioaccumulation in the digestive track and internal organs (i.e., liver and heart) of tadpoles. Long-term exposure to either size, at environmentally-related concentrations (1 and 4550 p/mL), led to growth and development delay in pro-metamorphic tadpoles. Remarkably, developmental plasticity mitigated these deleterious effects prior to the onset of metamorphic climax without compromising survival rate in later stages. MPs with a diameter of 10 μm dramatically altered the gut microbiota (e.g., abundance of Catabacter and Desulfovibrio) of pro-metamorphic tadpoles, whereas MPs with a diameter of 1 μm induced much more intensive transcriptional responses in the host tissues (e.g., upregulation of protein synthesis and mitochondrial energy metabolism, and downregulation of neural functions and cellular responses). Given that the two MPs sizes induced similar toxic outcomes, this suggests that their principal toxicity mechanisms are distinct. Small-sized MPs can travel easily across the intestinal mucosa and cause direct toxicity, while large-sized MPs accumulate in gut and affect the host by changing the homeostasis of digestive track. In conclusion, our findings indicate that MPs can affect the growth and development of amphibian larvae, but their developmental plasticity determines the ultimate detrimental effects. Multiple pathways of toxicity may contribute to the size-dependent toxicity of MPs. We anticipate that these findings will increase our understanding of the ecological effects of MPs.

Effects of microplastics and lead exposure on gut oxidative stress and intestinal inflammation in common carp (Cyprinus carpio L.)

Microplastics (MPs) are increasingly being detected in freshwater environments, which have the potential to cause combined toxicity with other contaminants on aquatic organisms. To reveal the ecological risks, the combined effects of lead (Pb) and polyvinyl chloride microplastics (MPs) were explored in the gut of common carp (Cyprinus carpio L.). The results confirmed that exposure of Pb alone accelerated Pb accumulation, increased oxidative stress, and activated the inflammation response of the gut. However, the aforementioned effects all decreased under the co-exposure of Pb and MPs. In addition, MPs altered intestinal microbial community of common carp, especially the abundance of immune system-related species. All measured variables were organized for partial least square path modeling, which revealed the combined effects of Pb and MPs on inflammation response. The results implied that MPs reduced inflammation response in two ways, including the reduction of intestinal Pb accumulation and the alteration of the intestinal microbial community. Overall, this study provides a novel aspect of ecological effects on aquatic animals from Pb and MPs exposure. The interesting results remind us that when exploring the ecological risks of MPs, combined effects from other toxic substances must be considered simultaneously.

Microplastics in aquatic environments: A comprehensive review of toxicity, removal, and remediation strategies

The occurrence of microplastics (MPs) in aquatic environments has been a global concern because they are toxic and persistent and may serve as a vector for many legacies and emerging pollutants. MPs are discharged to aquatic environments from different sources, especially from wastewater plants (WWPs), causing severe impacts on aquatic organisms. This study mainly aims to review the Toxicity of MPs along with plastic additives in aquatic organisms at various trophic compartments and available remediation methods/strategies for MPs in aquatic environments. Occurrences of oxidative stress, neurotoxicity, and alterations in enzyme activity, growth, and feeding performance were identical in fish due to MPs toxicity. On the other hand, growth inhibition and ROS formation were observed in most of the microalgae species. In zooplankton, potential impacts were acceleration of premature molting, growth retardation, mortality increase, feeding behaviour, lipid accumulation, and decreased reproduction activity. MPs togather with additive contaminants could also exert some toxicological impacts on polychaete, including neurotoxicity, destabilization of the cytoskeleton, reduced feeding rate, growth, survivability and burrowing ability, weight loss, and high rate of mRNA transcription. Among different chemical and biological treatments for MPs, high removal rates have been reported for coagulation and filtration (>86.5 %), electrocoagulation (>90 %), advanced oxidation process (AOPs) (30 % to 95 %), primary sedimentation/Grit chamber (16.5 % to 58.84 %), adsorption removal technique (>95 %), magnetic filtration (78 % to 93 %), oil film extraction (>95 %), and density separation (95 % to 100 %). However, desirable extraction methods are required for large-scale research in MPs removal from aquatic environments.

Functional Trait-Based Evidence of Microplastic Effects on Aquatic Species

Microplastics represent an ever-increasing threat to aquatic organisms. We merged data from two global scale meta-analyses investigating the effect of microplastics on benthic organisms' and fishes' functional traits. Results were compared, allowing differences related to vertebrate and invertebrate habitat, life stage, trophic level, and experimental design to be explored. Functional traits of aquatic organisms were negatively affected. Metabolism, growth, and reproduction of benthic organisms were impacted, and fish behaviour was significantly affected. Responses differed by trophic level, suggesting negative effects on trophic interactions and energy transfer through the trophic web. The experimental design was found to have the most significant impact on results. As microplastics impact an organism's performance, this causes indirect repercussions further up the ecological hierarchy on the ecosystem's stability and functioning, and its associated goods and services are at risk. Standardized methods to generate salient targets and indicators are urgently needed to better inform policy makers and guide mitigation plans.

Factors Affecting the Adsorption of Heavy Metals by Microplastics and Their Toxic Effects on Fish

Fish not only constitute an important trophic level in aquatic ecosystems but also serve as an important source of protein for human beings. The health of fish is related to the sustained and healthy development of their entire aquatic ecosystem. Due to the widespread use, mass production, high disposal frequency, and degradation resistance of plastics, these pollutants are released into aquatic environments on a large scale. They have become one of the fastest growing pollutants and have a substantial toxic effect on fish. Microplastics have intrinsic toxicity and can absorb heavy metals discharged into water. The adsorption of heavy metals onto microplastics in aquatic environments is affected by many factors and serves as a convenient way for heavy metals to migrate from the environment to organisms. Fish are exposed to both microplastics and heavy metals. In this paper, the toxic effects of heavy metal adsorption by microplastics on fish are reviewed, and the focus is on the toxic effects at the individual (survival, feeding activity and swimming, energy reserves and respiration, intestinal microorganisms, development and growth, and reproduction), cellular (cytotoxicity, oxidative damage, inflammatory response, neurotoxicity, and metabolism) and molecular (gene expression) levels. This facilitates an assessment of the pollutants' impact on ecotoxicity and contributes to the regulation of these pollutants in the environment.

Polyvinyl chloride microplastics induce changes in gene expression and organ histology along the HPG axis in Cyprinus carpio var. larvae

The negative consequences of microplastics pollution on the health of aquatic species have garnered extensive attention. However, the mechanisms through which microplastics may cause harm in the reproductive processes of fish remain unknown. For this study, Cyprinus carpio var. was subjected to four treatments with various concentrations of PVC microplastics for 60 days, through food rationed diets (no plastic control, 10%, 20% and 30%). The gonadosomatic indices, gonad and brain histologies, sex hormone levels, and transcriptional and translational genes in the hypothalamic-pituitary-gonadal (HPG) axes of both sexes were observed. According to the results, the gonadosomatic indices were significantly decreased, gonadal development was delayed, and the level of estradiol (E2) in the females was significantly elevated. In addition, the expression levels of genes associated with the HPG axis in the brains and gonads (gnrh, gtha1, fshβ, cyp19b, erα, vtg1, dmrt1, sox9b, and cyp19a) and the transcription levels of apoptosis-related genes in the brains and gonads (caspase3, bax, and bcl-2) exhibited significant changes. Further investigation revealed that the translation levels of genes linked to sex differentiation and sex steroid hormone (cyp19b and dmrt1) were significantly altered. These findings indicated that PVC likely microplastics may have a negative impact on the reproductive system of Cyprinus carpio var. by inhibiting gonadal development, affecting the gonad and brain structures, and altering the levels of steroid hormones and the expression of HPG axis-related genes. This work provides new insights into the toxicity of microplastics in aquatic organisms by revealing that PVC microplastics are a potential threat against the reproduction of fish populations.

An overview of microplastics in oysters: Analysis, hazards, and depuration

Microplastic pollution has become an emergent global environmental issue because of its ubiquitous nature and everlasting ecological impacts. In marine ecosystems, microplastics can serve as carriers to absorb various contaminants and the ingestion of microplastics in oysters is of concern because they can induce several adverse effects. The analytical process of microplastics in oysters commonly consists of separation, quantification, and identification. Quantification of microplastics is difficult since information regarding the analytical methods is incoherent, therefore, standard microplastic analytical methods for shellfish should be established in the future. The depuration process can be used to reduce the level of microplastics in oysters to ensure safe consumption of oysters and longer depuration time facilitates improved depuration efficacy. In summary, this review aims to help better understand microplastic pollution in oysters and provide useful suggestions and guidance for future research.

Do microplastics influence the long-term effects of ciprofloxacin on the polychaete Hediste diversicolor? An integrated behavioral and biochemical approach

Ciprofloxacin (CPX), the most commonly used fluoroquinolone antibiotic, and microplastics (MPs) are two classes of emerging contaminants with severe adverse impacts on aquatic organisms. Previous studies suggest that both CPX and MPs induce deleterious changes in exposed aquatic biota, but the characterization of a chronic and combined ecotoxicological response is not well known, especially in organisms from estuarine ecosystems. Thus, in this study, we investigated the behavioral and biochemical effects of environmentally relevant levels of CPX alone and in combination with polyethylene terephthalate (PET) microplastics over 28 days of exposure, using the polychaete Hediste diversicolor as a model. In addition to behavioral parameters, different biochemical endpoints were also evaluated, namely the levels of metabolic enzymes of phase I (7-ethoxy-resorufin-O-deethylase, EROD), and phase II (glutathione-S-transferase, GSTs), antioxidant defense (catalase, CAT; glutathione peroxidase, GPx; superoxide dismutase, SOD), oxidative damage (lipid peroxidation, by means of levels of thiobarbituric acid reactive substances [TBARS]) and acetylcholinesterase (AChE). Chronic exposure to ciprofloxacin caused a decrease in burrowing time and a significant increase in SOD activity. In animals exposed to the combination of CPX and PET MPs, effects on behavioral traits were also observed, with higher concentrations of MPs leading to a marked delay in the animals' burrowing time. In addition, these animals showed changes in their antioxidant defenses, namely, a significant increase in SOD activity, while GPx activity was severely compromised. For none of the experimental groups, significant alterations were observed in the metabolic enzymes, TBARS or AChE. These findings provide the first insights into the responses of H. diversicolor when exposed to the combination of CPX and PET MPs, highlighting that, although the here studied conditions, there was no evidence of oxidative damage or neurotoxicity, these organisms are not risk-free in co-exposure scenarios, even at low environmental relevant concentrations.

Effects of common plastic products heat exposure on cognition: Mediated by gut microbiota

Considering plastic exposure patterns in modern society, the effects of exposure to leachate from boiled-water treated plastic products on cognitive function was probed in mice through changes in gut microbiota diversity. In this study, Institute for Cancer Research (ICR) mice were used to establish drinking water exposure models of three popular kinds of plastic products, including non-woven tea bags, food-grade plastic bags and disposable paper cups. 16S rRNA was used to detect changes in the gut microbiota of mice. Behavioral, histopathology, biochemistry, and molecular biology experiments were used to evaluate cognitive function in mice. Our results showed that the diversity and composition of gut microbiota changed at genus level compared to control group. Nonwoven tea bags-treated mice were proved an increase in Lachnospiraceae and a decreased in Muribaculaceae in gut. Alistipes was increased under the intervention of food grade plastic bags. Muribaculaceae decreased and Clostridium increased in disposable paper cups group. The new object recognition index of mice in the non-woven tea bag and disposable paper cup groups decreased, and amyloid β-protein (Aβ) and tau phosphorylation (P-tau) protein deposition. Cell damage and neuroinflammation were observed in the three intervention groups. Totally speaking, oral exposure to leachate from boiled-water treated plastic results in cognitive decline and neuroinflammation in mammals, which is likely related to MGBA and changes in gut microbiota.

The risks of marine micro/nano-plastics on seafood safety and human health

A considerable mass of plastics has been released into the marine environment annually through different human activities, including industrial, agriculture, medical, pharmaceutical and daily care products. These materials are decomposed into smaller particles such as microplastic (MP) and nanoplastic (NP). Hence, these particles can be transported and distributed in coastal and aquatic areas and are ingested by the majority of marine biotas, including seafood products, thus causing the contamination of the different parts of aquatic ecosystems. In fact, seafood involves a wide diversity of edible marine organisms, such as fish, crustaceans, molluscs, and echinoderms, which can ingest the micro/nanoplastics particles, and then transmit them to humans through dietary consumption. Consequently, these pollutants can cause several toxic and adverse impacts on human health and the marine ecosystem. Therefore, this chapter provides information on the potential risks of marine micro/nanoplastics on seafood safety and human health.

Microplastics in terrestrial ecosystem: Sources and migration in soil environment

Plastics, especially microplastics in soils, are considered a severe environmental issue worldwide. However, globally, the main research focus is on microplastic pollution in the marine environment, the microplastic pollution on soils and sediments remains on the sideline so far. But the fact is that microplastics are omnipresent in terrestrial systems in the form of microbeads in industrial systems and in sewage sludge. Their presence in agricultural soils and sediments is enormously increased due to plastic mulching, plastic greenhouses and compost and extensive use of controlled release fertilizers. Therefore, this review outlines the global scenario regarding plastics and microplastics production, consumption, and possible pathways of penetration into the soil environment. Various mechanisms to restrict and manage the pathways of plastics and microplastics into the soil environment are also discussed. This review also focuses on the challenges and limitations on the use of plastic alternates such as bioplastics and oxo plastics. Also, the knowledge gaps on the source of microplastics in the environment and their deleterious effects on properties of soil, soil health and focused light on their soil trophic transfer in food chains via plants. This review provides a detailed insight on the management and possible control measures to alleviate the potential risk caused by microplastics pollution in the soil environment and the overall ecosystem's health. In spite of the occurrence and fate of microplastics on terrestrial environment, knowledge gaps and challenges for tackling this contamination are also explored which facilitates the policy makers to develop regulatory measures towards the containment of microplastics in living ecosystem.

From marine to freshwater environment: A review of the ecotoxicological effects of microplastics

Microplastics (MPs) have been widely detected in the world's water, which may pose a significant threat to the ecosystem as a whole and have been a subject of much attention because their presence impacts seas, lakes, rivers, and even the Polar Regions. There have been numerous studies that report direct adverse effects on marine organisms, but only a few have explored their ecological effects on freshwater organisms. In this field, there is still a lack of a systematic overview of the toxic effects and mechanisms of MPs on aquatic organisms, as well as a consistent understanding of the potential ecological consequences. This review describes the fate and impact on marine and freshwater aquatic organisms. Further, we examine the toxicology of MPs in order to uncover the relationship between aquatic organism responses to MPs and ecological disorders. In addition, an overview of the factors that may affect the toxicity effects of MPs on aquatic organisms was presented along with a brief examination of their identification and characterization. MPs were discussed in terms of their physicochemical properties in relation to their toxicological concerns regarding their bioavailability and environmental impact. This paper focuses on the progress of the toxicological studies of MPs on aquatic organisms (bacteria, algae, Daphnia, and fish, etc.) of different trophic levels, and explores its toxic mechanism, such as behavioral alternations, metabolism disorders, immune response, and poses a threat to the composition and stability of the ecosystem. We also review the main factors affecting the toxicity of MPs to aquatic organisms, including direct factors (polymer types, sizes, shapes, surface chemistry, etc.) and indirect factors (persistent organic pollutants, heavy metal ions, additives, and monomer, etc.), and the future research trends of MPs ecotoxicology are also pointed out. The findings of this study will be helpful in guiding future marine and freshwater rubbish studies and management strategies.

Microplastics induce neurotoxicity in aquatic animals at environmentally realistic concentrations: A meta-analysis

Microplastics (MPs) draw international attention owing to their widespread distribution in water ecosystems, but whether MPs cause neurotoxic effects in aquatic animals at environmentally realistic concentrations is still controversial. This meta-analysis recompiled 35 studies to determine whether MPs could change the levels of brain (in vivo) neurotransmitters in aquatic animals at environmentally realistic concentrations (≤1 mg/L, median = 0.100 mg/L). Then, a group comparison was conducted to compare the effects of different factors on the effect size and to explore the significant factors affecting the neurotoxicity of MPs. The results demonstrated that MP exposure could considerably decrease the levels of acetylcholinesterase (AchE) in the brain of aquatic animals by 16.2%. However, the effects of MPs on cholinesterase (CHE), acetylcholine (ACh), dopamine (DA) and γ-aminobutyric acid (GABA) were not statistically significant due to the small number of studies and samples. The neurotoxicity of MPs was closely linked with particle size and exposure time but independent of animal species, MP compositions, MP morphology and MP concentrations. Further literatures review indicated that MP-induced neurotoxicity and behavioral changes are related with multiple biological processes, including nerve damage, oxidative stress, intestinal flora disturbance and metabolic disorder. Furthermore, some factors influencing MP neurotoxicity in the real environment (e.g. the aging of MPs, the release of MP additives, and the co-exposure of MPs and pollutants) were discussed. Overall, this study preliminarily explored whether MPs induced changes in neurotoxicity-related indicators in aquatic animals through meta-analysis and provided scientific evidence for evaluating the health risks and neurotoxicity of MPs at the environmental level.

Evaluation of toxicity of polystyrene microplastics under realistic exposure levels in human vascular endothelial EA.hy926 cells

Microplastics (MPs) have emerged as a global concern, with a recent study being the first to detect them in the bloodstream of healthy people. However, precise information regarding the toxic effects of MPs on the human vascular system is currently lacking. In this study, we used human vascular endothelial EA. hy926 cells to examine the toxic potential of polystyrene MPs (PSMPs) under realistic blood concentrations. Our findings indicated that PSMPs can cause oxidative stress by reducing the expression of antioxidants, thereby leading to apoptotic cytotoxicity in EA. hy926 cells. Furthermore, the protective potential of heat shock proteins can be reduced by PSMPs. PSMP-induced apoptosis might also lower the expression of rho-associated protein kinase-1 and nuclear factor-κB expression, thus dampening LRR- and pyrin domain-containing protein 3 in EA. hy926 cells. Moreover, we observed that PSMPs induce vascular barrier dysfunction via the depletion of zonula occludens-1 protein. However, although protein expression of the nuclear hormone receptor 77 was inhibited, no significant increase in ectin-like oxidized low-density lipoprotein receptor-1 was noted in PSMP-treated EA. hy926 cells. These results demonstrate that exposure to PSMPs may not sufficiently increase the risk of developing atherosclerosis. Overall, our research signifies that exposure to realistic blood concentrations of PSMPs is associated with low atherosclerotic cardiovascular risk in humans.

Are microplastics contributing to pollution-induced neurotoxicity? A pilot study with wild fish in a real scenario

Pollution-induced neurotoxicity is of high concern. This pilot study investigated the potential relationship between the presence of microplastics (MPs) in the brain of 180 wild fish (Dicentrarchus labrax, Platichthys flesus, Mugil cephalus) from a contaminated estuary and the activity of the acetylcholinesterase (AChE) enzyme. MPs were found in 9 samples (5% of the total), all of them from D. labrax collected in the summer, which represents 45% of the samples of this species collected in that season (20). Seventeen MPs were recovered from brain samples, with sizes ranging from 8 to 96 μm. Polyacrylamide, polyacrylic acid and one biopolymer (zein) were identified by Micro-Raman spectroscopy. Fish with MPs showed lower (p ≤ 0.05) AChE activity than those where MPs were not found. These findings point to the contribution of MPs to the neurotoxicity induced by long-term exposure to pollution, stressing the need of further studies on the topic to increase 'One Health' protection.

Impact of face mask microplastics pollution on the aquatic environment and aquaculture organisms

Microplastic pollution in our environment, especially water bodies is an emerging threat to food security and human health. Inevitably, the outbreak of Covid-19 has necessitated the constant use of face masks made from polymers such as polypropylene, polyurethane, polyacrylonitrile, polystyrene, polycarbonate, polyethylene, or polyester which eventually will disintegrate into microplastic particles. They can be broken down into microplastics by the weathering action of UV radiation from the sun, heat, or ocean wave-current and precipitate in natural environments. The global adoption of face masks as a preventive measure to curb the spread of Covid-19 has made the safe management of wastes from it cumbersome. Microplastics gain access into aquaculture facilities through water sources and food including planktons. The negative impacts of microplastics on aquaculture cannot be overemphasized. The impacts includes low growth rates of animals, hindered reproductive functions, neurotoxicity, low feeding habit, oxidative stress, reduced metabolic rate, and increased mortality rate among aquatic organisms. With these, there is every tendency of microplastic pollution to negatively impact fish production through aquaculture if the menace is not curbed. It is therefore recommended that biodegradable materials rather than plastics to be considered in the production of face mask while recycle of already produced ones should be encouraged to reduce waste.

A review on enhanced microplastics derived from biomedical waste during the COVID-19 pandemic with its toxicity, health risks, and biomarkers

The COVID-19 pandemic led to the explosion of biomedical waste, a global challenge to public health and the environment. Biomedical waste comprising plastic can convert into microplastics (MPs, < 5 mm) by sunlight, wave, oxidative and thermal processes, and biodegradation. MPs with additives and contaminants such as metals are also hazardous to many aquatic and terrestrial organisms, including humans. Bioaccumulation of MPs in organisms often transfers across the trophic level in the global food web. Thus, this article aims to provide a literature review on the source, quantity, and fate of biomedical waste, along with the recent surge of MPs and their adverse impact on aquatic and terrestrial organisms. MPs intake (ingestion, inhalation, and dermal contact) in humans causing various chronic diseases involving multiple organs in digestive, respiratory, and reproductive systems are surveyed, which have been reviewed barely. There is an urgent need to control and manage biomedical waste to shrink MPs pollution for reducing environmental and human health risks.

Polystyrene microplastics enhanced copper-induced acute immunotoxicity in red swamp crayfish (Procambarus clarkii)

Microplastic pollution has attracted a lot of attention in recent years. Not only can it be ingested by animals, but it can easily become a carrier of other pollutants, forming a composite pollutant with potentially toxic effects on organisms. We investigated the effect of Cu on the accumulation of polystyrene microplastics (PS) in the gills of Procambarus clarkii and whether PS exacerbated the immune toxicity of Cu to P. clarkii were exposed to Cu, PS and PS+Cu for 48 h, the accumulation of PS in gill and hepatopancreas immune and antioxidant indices were analyzed. The objective was to investigate the toxic effects of Ps and Cu compound pollutants on P. clarkii and whether the accumulated pollutants would cause food safety problems. The results showed that microplastic particles adhered to each other and aggregated in the PS+Cu group, and the number of microplastic particles in gill in the PS+Cu group was significantly lower than that in the PS group. Compared with the other two treatment groups, SOD, CAT, GPx activities and MDA content increased significantly in the PS+Cu group and were relatively delayed. At 12 h, 24 h, 36 h and 48 h, the SOD mRNA expression levels in the PS+Cu group were all significantly lower than those in the Cu group (P < 0.05). At 24 h and 48 h, CAT mRNA expression in the PS+Cu group was significantly higher than that in the Cu group (P < 0.05). Crustin 4 mRNA expressions in the PS+Cu group was significantly higher than that in the Cu group at 12 h and 36 h (P < 0.05). The results demonstrate that the PS and Cu compound reduced the accumulation of microplastic particles in the gill. PS particles delayed Cu entry into P. clarkii for a short time (12 h) and reduced the toxic effect, but with the increase of exposure time (24 h and 48 h), the toxic effect of PS and Cu complexes on P. clarkii increases, and the large accumulation of PS and Cu complexes may cause food safety problems.

How do microplastics adsorb metals? A preliminary study under simulated wetland conditions

Microplastics (MPs) are widely detected in wetlands as emerging pollutants of global concern. Co-occurrence of MPs and trace metals in wetlands is common and the vector effects of MPs on other environmental pollutants have been increasingly reported. However, the interaction of different MPs and trace metals under environmentally realistic conditions is not well understood. Here, we investigated the adsorption capacity of MPs for metals under simulated conditions of Poyang Lake wetlands in Jiang Xi, China, a Ramsar site of international importance for conservation and sustainable use. ICP-MS was used to quantify the amount of adsorbed metals onto different types of MPs. SEM-EDS and micro-FTIR were used to examine the morphological and chemical characteristics of MPs before and after metal adsorption. The influence of internal (polymer types and particle sizes of MPs) and external factors (water pH values, organic matters, ion strength, and sediment) on metal adsorption was systematically investigated. Metal adsorption equilibrium was most achieved at 72 h. The adsorption capacity of MP types to metal ions tended to decrease as PP > PE > PS, and the amount of adsorbed metals decreased as Cu > Pb > Cd. The amount of adsorbed metals generally decreased with the increase of particle size of MPs. With the increase of water pH and K⁺ strength, the adsorption of metals by MPs showed an increasing and then decreasing trend; the adsorption capacity of MPs increased with the increase of fulvic acid. Under the simulated sedimentary conditions, the adsorption of different metals by MPs also tended to be Cu > Pb > Cd, which was mainly determined by metal concentrations in the sediments collected in situ. The results of this study improve our understanding of metal-MP interaction under simulated environmental conditions, shedding new light on the environmental behavior of MPs and metals in wetlands.

Impact of the COVID-19 pandemic on research on marine plastic pollution - A bibliometric-based assessment

Fighting the COVID-19 pandemic has led to a dramatic increase in plastic waste, which has had a huge impact on the environment, including the marine environment. This work aims to evaluate the pattern of national research cooperation, research hotspots, and research evolution before and during the epidemic by systematically reviewing the publications on marine plastic pollution during 2015-2019 (before the pandemic) 2020-2022 (during the pandemic) using the systematic literature review and latent semantic analysis. The results show (i) Compared to pre-pandemic, publications on marine pollution during the COVID-19 pandemic declined briefly and then increased sharply. (ii) Compared with before the pandemic, the national cooperation model has changed during the pandemic, and four major research centers have been formed: Central European countries centered on Italy; Nordic countries centered on United Kingdom; South Korea, India and other developing countries in Asia and Africa and a Pacific Rim country centered on United States and China. (iii) The knowledge map of keyword clustering does not change significantly before and during the COVID-19: ecosystem, spatial distribution, environmental governance and biodegradation. However, there are differences in the sub-category research of the four types of keywords. (iv) The impact of marine plastic on organisms and the governance of marine plastic pollution have become a branch of knowledge that have evolved rapidly during the pandemic. The governance of marine plastic pollution and microplastics are expected to become an important research direction.

Effects of polystyrene microplastics acute exposure in the liver of swordtail fish (Xiphophorus helleri) revealed by LC-MS metabolomics

As global pollution, microplastics pollution has aroused growing concerns. In our experiment, the effect of microplastics acute exposure on the liver of swordtail fish was investigated by using LC-MS metabolomics. Fishes treated with high concentration polystyrene microspheres (1 μm) for 72 h were divided into three concentration groups: (A) no microplastics, (B): 1 × 10⁶ microspheres L^-1, (C): 1 × 10⁷ microspheres L^-1. Metabolomic analysis indicated that exposure to microplastics caused alterations of metabolic profiles in swordtail fish, including 37 differential metabolites were identified in B vs. A, screened out ten significant metabolites, which involved 14 metabolic pathways. One hundred three differential metabolites were identified in C vs. A, screened out 16 significant metabolites, which involved 30 metabolic pathways. Six significant metabolites were overlapping in group B vs. A and C vs. A; they are 3-hydroxyanthranilic acid, l-histidine, citrulline, linoleic acid, pantothenate, and xanthine. In addition, four metabolic pathways are overlapping in group B vs. A and C vs. A; they are beta-alanine metabolism, biosynthesis of amino acids, linoleic acid metabolism, and aminoacyl-tRNA biosynthesis. These differential metabolites were involved in oxidative stress, immune function, energy metabolism, sugar metabolism, lipid metabolism, molecule transport, and weakened feed utilization, growth performance, nutrient metabolism, and animal growth. Furthermore, we found that the number of interfered amino acids and microplastics showed a dose-effect. In summary, great attention should be paid to the potential impact of microplastics on aquatic organisms.

Short- and long-term single and combined effects of microplastics and chromium on the freshwater water flea Daphnia magna

In this study, we investigated the individual and combined effects of microplastics (MPs) and chromium (Cr) on the freshwater water flea Daphnia magna by measuring mortality, bioaccumulation, antioxidative response, multixenobiotic resistance activity, and sestrin-related mitochondrial biogenesis in short-term assays and in vivo endpoints including reproduction and adult survival rate in long-term assays. Exposure to MPs, Cr, and their combination caused significant deleterious effects and acute toxicity in D. magna. Alterations in oxidative stress occurred in the groups treated with MPs and Cr alone and together. However, upon co-exposure to MPs, the Cr concentration, measured by inductively coupled plasma optical emission spectroscopy, decreased, suggesting that MPs and Cr interact with each other. Based on enzymatic activities, we noted a decrease in MP egestion via inhibition of P-glycoprotein activity in the MP-exposed groups, and multidrug resistance-associated protein activity increased in some of the MP-exposed animals depending on Cr concentration. On the other hand, MP exposure seemed to lead to mitochondrial transcription dysfunction induced by Cr via sestrin-related mitochondrial biogenesis. Overall, these results indicate that co-exposure to MPs and Cr causes acute toxicity in D. magna but lacks the chronic toxicity (21 days) and mitochondrial dysfunction caused by Cr exposure alone.

Polystyrene microplastics inhibit the neurodevelopmental toxicity of mercury in zebrafish (Danio rerio) larvae with size-dependent effects

Insufficient evidence exists regarding the effects of microplastics (MPs) on the neuronal toxicity of heavy metals in the early stages of organisms. Herein, the effects of micro-polystyrene (μ-PS; 157 μm) and nano-polystyrene (n-PS; 100 nm) particles on the neurodevelopmental toxicity of mercury (Hg) in zebrafish embryos were compared. Zebrafish embryos exposed to Hg at the concentration of 0.1 mg L^-1 revealed blood disorders, delayed hatching, and malformations such as pericardial oedema and tail deformity. The length of the larval head was significantly reduced (P < 0.01) and in vivo expression of atoh1a in the cerebellum of neuron-specific transgenic zebrafish Tg(atoh1a:dTomato) larvae was inhibited by 29.46% under the Hg treatment. Most of the toxic effects were inhibited by the combined exposure to μ-PS or n-PS with Hg, and n-PS decreased the neurodevelopmental toxicity of Hg more significantly than μ-PS. Metabolomic analysis revealed that in addition to inhibiting the amino acid metabolism pathway as in the μ-PS+Hg treatment, the n-PS+Hg treatment inhibited unsaturated fatty acid metabolism in zebrafish larvae, likely because of a greater reduction in Hg bioavailability, thus reducing the oxidative damage caused by Hg in the larvae. The combined effects of MPs and heavy metals differ greatly among different species and their targeted effects. We conclude that the combined toxicity mechanisms of MPs and heavy metals require further clarification.

Microplastic Contamination and Ecological Status of Freshwater Ecosystems: A Case Study in Two Northern Portuguese Rivers

BACKGROUND

Most European rivers have not yet achieved "good" ecological status. In addition, the presence and abundance of microplastics (MPs) in freshwater is a matter of great concern to the scientific community.

METHODOLOGY

This study assesses the ecological status of four sampling sites of Selho (S1-S4) and Costa-Couros (C1-C4) rivers (Guimarães, Portugal), and the abundance of MPs in sediments and benthic macroinvertebrates (Oligochaeta) from those sites.

RESULTS

All sites of both rivers under higher pressure did not reach a "good" ecological status (S2-S3, C2-C4) based on the macroinvertebrate community. High levels of nutrients were observed at all sites in both rivers (except C2), especially phosphorus. In the Oligochaeta's gut of Costa-Couros river, the high number of MPs seems to be associated with their weight (95.25 ± 25.61 to 1069.00 ± 385.30 MPs g/fresh weight), suggesting the existence of malnutrition and digestive disorders, whereas the highest number of MPs in gut (134.00 ± 30.36 to 558.6 ± 100.70 MPs g/fresh weight) were found for the heaviest organisms of Selho.

CONCLUSIONS

Thus, sites with higher ecological status do not necessarily have lower abundance of MPs. In the sediments, urbanization seems to be the main driver for MP contamination. MP contamination is pervasive across the sediments and Oligochaeta's gut in both rivers. Since MPs have the potential to cause harm to environmental and human health, it is essential to monitor not only the ecological status of freshwaters, but also emerging pollutants such as MPs.

Indication of the impact of environmental stress on the responses of the bivalve mollusk Unio tumidus to ibuprofen and microplastics based on biomarkers of reductive stress and apoptosis

The vulnerability of bivalve mollusks to micropollutants is estimated mainly in single model exposures. However, chronic environmental stress and complex exposures can modulate their responses. To evaluate the impact of population-dependent adaptations on the ability to react to common micropollutants, we compared freshwater bivalves Unio tumidus from two distinct populations, pure (Pr) and contaminated (Ct), in their exposures to microplastics (MP, 1 mg L^-1, size 0.1-0.5 mm), pharmaceutical ibuprofen (IBU, 0.8 μg L^-1), or their combination (Mix) for 14 days. Control groups from both sites showed remarkable differences, with lower levels of total antioxidant capacity (TAC), metallothionein protein (MTSH), NADH and NAD⁺, cytochrome P450-related EROD, glutathione-S transferase (GST), and citrate synthase (CS) but higher levels of GSH, GSSG, caspase-3 and cathepsin D (CTD) in the Ct-control group. These data indicate a chronic stress impact in the Ct population. Under exposures, we found an almost common strategy in both populations for NAD⁺/NADH and MTSH suppression and CTD induction. Additionally, Mix exposure caused an increase in CS, and IBU did not change GSH in both populations. However, the expected response to IBU - the suppression of caspase-3 - was indicated only in PrIBU- and PrMix-mollusks. CTD efflux increased dramatically only in PrMP- and PrMix- groups, and suppression of EROD and GST was detected in the PrMix-group. According to discriminant analysis, exposed Pr-groups were highly differentiated from control, whereas Ct-control and exposed groups had common localization demonstrating high resistance to environmental stress. Thus, the same exposures resulted in different adverse outcome pathways depending on the population.

Microplastic Contamination of Chicken Meat and Fish through Plastic Cutting Boards

Microplastic contamination was found in fish and chicken bought on the market, in food stores and in chain supermarkets in the Middle East with the contamination ranging from 0.03 ± 0.04 to 1.19 ± 0.72 particles per gram of meat in chicken and from 0.014 ± 0.024 to 2.6 ± 2.8 particles per gram in fish. Only one fish was found to be free of microplastic. The source of the microplastic was established to be the polythene-based plastic cutting board the food was cut on. More microplastic contamination was found in food cut from the bone than in cut fillets when the fillets themselves were prepared on surfaces other than plastic. Washing the fish and chicken before food preparation decreased but did not completely remove the microplastic contamination. The fate of the microplastic in grilled fish was studied. The mechanical properties of typical plastic cutting boards commercially used in the markets were investigated in the form of tensile, hardness, and wear tests. Overall, the plastic cutting boards showed similar wear rates.

Effects of oral exposure to leachate from boiled-water treated plastic products on gut microbiome and metabolomics

By simulating plastic exposure patterns in modern society, the impact of daily exposure to plastic products on mammals was explored. In this study, Institute for Cancer Research (ICR) mice were used to establish drinking water exposure models of three popular kinds of plastic products, including non-woven tea bags, food-grade plastic bags and disposable paper cups. Feces and urine of mice were collected for gut microbiome and metabolomics analysis. Our results showed that the diversity and composition of gut microbiota changed at genus level compared to control group. Lactobacillus, Parabacteroides, Escherichia-shigella and Staphylococcus decreased while Lachnospiraceae increased treated with non-woven tea bags. Escherichia-shigella and Alistipes increased while Parabacteroides decreased treated with food grade plastic bags. Muribaculaceae decreased in the gut microbiota of mice treated with disposable paper cups. Metabolomics has seen changes in the number of metabolites and enrichment of metabolic pathways related to inflammatory responses and immune function. Inflammatory responses were found in histological and biochemical examination. In summary, this study demonstrated that long-term oral exposure to leachate form boiled-water treated plastic products might have effects on gut microbiome and metabolome, which further provided new insights about potential adverse effects for human beings.

Ecotoxic effects of microplastics and contaminated microplastics - Emerging evidence and perspective

The high prevalence and persistence of microplastics (MPs) in pristine habitats along with their accumulation across environmental compartments globally, has become a matter of grave concern. The resilience conferred to MPs using the material engineering approaches for outperforming other materials has become key to the challenge that they now represent. The characteristics that make MPs hazardous are their micro to nano scale dimensions, surface varied wettability and often hydrophobicity, leading to non-biodegradability. In addition, MPs exhibit a strong tendency to bind to other contaminants along with the ability to sustain extreme chemical conditions thus increasing their residence time in the environment. Adsorption of these co-contaminants leads to modification in toxicity varying from additive, synergistic, and sometimes antagonistic, having consequences on flora, fauna, and ultimately the end of the food chain, human health. The resulting environmental fate and associated risks of MPs, therefore greatly depend upon their complex interactions with the co-contaminants and the nature of the environment in which they reside. Net outcomes of such complex interactions vary with core characteristics of MPs, the properties of co-contaminants and the abiotic factors, and are required to be better understood to minimize the inherent risks. Toxicity assays addressing these concerns should be ecologically relevant, assessing the impacts at different levels of biological organization to develop an environmental perspective. This review analyzed and evaluated 171 studies to present research status on MP toxicity. This analysis supported the identification and development of research gaps and recommended priority areas of research, accounting for disproportionate risks faced by different countries. An ecological perspective is also developed on the environmental toxicity of contaminated MPs in the light of multi-variant stressors and directions are provided to conduct an ecologically relevant risk assessment. The presented analyses will also serve as a foundation for developing environmentally appropriate remediation methods and evaluation frameworks.

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.

Microplastic loads within riverine fishes and macroinvertebrates are not predictable from ecological or morphological characteristics

Microplastics are a relatively new but important form of freshwater contamination that can be ingested by a range of different species, with particle counts thought to be predictable from species ecology and morphology. Here, we report levels of microplastics in a 26 μm-5 mm size range within the macroinvertebrate and fish community of a lowland river (Dorset Stour, SW England), and test the hypothesis that counts are predictable from characteristics such as feeding guild, body length and trophic position. Macroinvertebrates (n = 257, 12 taxa) and fish (n = 418, 9 species) were collected from distinct river reaches by kick sampling and rod and line angling, respectively. Batches of whole macroinvertebrates and individual fish gastrointestinal tracts were digested with 30% hydrogen peroxide before microplastic screening and FTIR polymer confirmation on a particle subset. Particles were found in 40% of pooled macroinvertebrate batches (taxa incidences: 14-75%) and 39% of fishes (species incidences: 29-47%). Dominant particle feature categories were ≤100 μm, blue/green, fragments and fibres identified as various polyolefins. Although particle counts in macroinvertebrates were highest in Ephemeroptera (mean of 0.74 particles per individual), the relationships between particle loads, batch number and guild were all non-significant. In fishes, particle counts were not significantly related to species, stomach structure, feeding guild or body length, with spatial differences also not apparent across the catchment. Individual fish particle counts were similarly not significantly associated with their trophic positions (calculated from bulk δ¹⁵N values for a subset of fishes) and parasite load of Pomphorhynchus tereticollis. Correlations between fish and macroinvertebrate particle counts within specific river reaches were also not significant. In entirety, these results indicated although loadings of microplastic particles were relatively consistent within the two communities, they were not predictable from any of their ecological or morphological characteristics.

Long-term effects of lithium and lithium-microplastic mixtures on the model species Daphnia magna: Toxicological interactions and implications to 'One Health'

Environmental contamination with lithium (Li) and microplastics (MP) has been steadily increasing and this trend is expected to continue in the future. Many freshwater ecosystems, which are crucial to reach the United Nations Sustainable Development Goals, are particularly vulnerable to Li and MP contamination, and other pressures. The long-term effects of Li, either alone or combined with MP (Li-MP mixtures), were investigated using the freshwater zooplankton micro-crustacean Daphnia magna as model species. In the laboratory, D. magna females were exposed for 21 days to water concentrations of Li (0.02, 0.04, 0.08 mg/L) or Li-MP mixtures (0.02 Li + 0.04 MP, 0.04 Li + 0.09 MP mg/L, 0.08 Li + 0.19 MP mg/L). In the range of concentrations tested, Li and Li-MP mixtures caused parental mortality, and decreased the somatic growth (up to 20% and 40% reduction, respectively) and the reproductive success (up to 93% and 90% reduction, respectively). The 21-day EC₅₀s of Li and Li-MP mixtures on D. magna reproduction were 0.039 mg/L and 0.039 Li + 0.086 MP mg/L, respectively. Under exposure to the highest concentration of Li (0.08 mg/L) and Li-MP mixtures (0.08 Li + 0.19 MP mg/L), the mean of D. magna population growth rate was reduced by 67% and 58%, respectively. Based on the population growth rate and using data from a bioassay testing the same concentrations of MP alone and carried simultaneously, the toxicological interaction between Li and MP was antagonism under exposure to the lowest and the highest concentrations of Li-MP mixtures, and synergism under exposure to the medium concentration of Li-MP mixtures. These findings highlight the need of further investigating the combined effects of contaminants, and the threat of long-term environmental contamination with Li and MP to freshwater zooplankton, biodiversity, ecosystem services and 'One Health'.

Synthetical effect of microplastics and chiral drug amphetamine on a primary food source algae Chlorella pyrenoids

The biological effects and fate of the chiral illicit drug amphetamine in the presence and absence of microplastics on freshwater algae (Chlorella pyrenoids), including acute toxicity, growth inhibition, photosynthetic pigment content, oxidative stress, lipid peroxidation, and enantioselective fate were assessed. An agglomeration and the shading effects of microplastics in algae suspension were also determined. Microplastics were observed to increase the toxicity of amphetamine to algae and reduce algae cell growth. Exposed Chlorella pyrenoids exhibited a reduced algae cell counts in an agglomeration test, wherein algae cells decreased between 18% and 56% among treatment groups exposed to 5-50 mg L^-1 of microplastics. The agglomeration test suggested that microplastics might significantly increase the adverse effect on algae. Furthermore, our experiments demonstrated enantioselective degradation of amphetamine in algae, and demonstrated that the S-enantiomer was preferably degraded by algae cells. Adding microplastics to the algae suspension significantly reduced the enantioselectivity, with an EF value of 0.41 compared with amphetamine-alone group (0.34) after 21 d exposure. These results demonstrated the first evidence of microplastics acting as a vehicle to enhance amphetamine toxicity to Chlorella pyrenoids, as well as provided new insights into the co-effect of microplastics and organic contaminants on food source.

Interactions of microplastics with organic, inorganic and bio-pollutants and the ecotoxicological effects on terrestrial and aquatic organisms

As emerging contaminants, microplastics (MPs) have attracted global attention. They are a potential risk to organisms, ecosystems and human health. MPs are characterized by small particle sizes, weak photodegradability, and are good environmental carriers. They can physically adsorb or chemically react with organic, inorganic and bio-pollutants to generate complex binary pollutants or change the environmental behaviors of these pollutants. We systematically reviewed the following aspects of MPs: (i) Adsorption of heavy metals and organic pollutants by MPs and the key environmental factors affecting adsorption behaviors; (ii) Enrichment and release of antibiotic resistance genes (ARGs) on MPs and the effects of MPs on ARG migration in the environment; (iii) Formation of "plastisphere" and interactions between MPs and microorganisms; (iv) Ecotoxicological effects of MPs and their co-exposures with other pollutants. Finally, scientific knowledge gaps and future research areas on MPs are summarized, including standardization of study methodologies, ecological effects and human health risks of MPs and their combination with other pollutants.

Microplastic presence in the pelagic fish, Seriola dumerili, from Balearic Islands (Western Mediterranean), and assessment of oxidative stress and detoxification biomarkers in liver

Microplastics (MPs) are characterized by their high persistence in marine ecosystems, and due to their small size, they can be easily ingested by very diverse organisms. Although the presence of MPs in wild fish is well documented, there is still limited information on their potential to induce adverse effects. Pelagic fish species, because of their wide distribution, are considered good bioindicators for monitoring environmental pollution of marine ecosystems. This study investigated the presence of MPs in the gastrointestinal tract of the predatory pelagic fish (Seriola dumerili) in the Balearic Islands (Mediterranean Sea), and the possible relationship with oxidative stress through the analysis of biomarkers in liver tissue. The results showed the presence of MPs in 98% of total samples examined (n = 52) with an average of 12.2 ± 1.3 MPs/individual. A greater amount of fibre-like particles was isolated compared to fragments. No correlation between the presence of MPs in the gastrointestinal contents and the size of the fishes was noted. Antioxidant enzymes (superoxide dismutase and catalase) and the phase II detoxification enzyme glutathione-S-transferase showed increased activities in fish with higher MPs load. The activity ethoxyresorufin-O-deethylase and the levels of malondialdehyde were similar in both groups. In conclusion, the present results provide an important database on the assessment of the presence of MP debris in S. dumerili gastrointestinal tract and, the potential capability to cause oxidative stress.

Toxic effects of pristine and aged polystyrene microplastics on selective and continuous larval culture of acorn barnacle Amphibalanus amphitrite

This study evaluates the toxicity of pristine (Unwashed) and aged, clean (Biofilm-) or fouled (Biofilm+), PS microspheres (3 µm,10 µm), using Washed particles as a reference material, on selective and continuous larval culture of Amphibalanus amphitrite. Exposure to 3 µm Unwashed and Biofilm+ particles for 24 h induced significant mortality (60 % and 57 % respectively) in stage II larvae. Stage II and VI nauplii showed greater uptake of 3 µm Biofilm- particles. Accumulative exposure to microplastics in continuous larval culture significantly affected the naupliar survival, particularly of stage III and IV. Cumulative mortality was > 70% after exposure to 3 µm Unwashed and 10 µm Biofilm+ particles. Unwashed particles with increasing concentration and aged particles with increasing size, delayed the development of nauplii to cyprids. Though,> 50% cyprids showed successful settlement however the highest concentration of 3 µm Biofilm+ microspheres inhibited the settlement and induced precocious metamorphosis in 9 % of the cyprids.

Oxidative stress, apoptosis and serotonergic system changes in zebrafish (Danio rerio) gills after long-term exposure to microplastics and copper

Fish gills are in direct contact with the surrounding pollutants, and thus, potentially more vulnerable to microplastics (MPs) and heavy metals. The present study aimed to evaluate the long-term exposure effects of MPs and copper (Cu) in the gills of adult zebrafish (Danio rerio). To this end, zebrafish were exposed to MPs (2 mg/L), Cu (Cu25, 25 μg/L) and their mixture (Cu25 + MPs) for 30 days, and then oxidative stress, detoxification, antioxidant, metabolic and neurotoxicity enzymes/genes, as well serotonergic system and apoptosis genes, were evaluated in gills. In the mixture group, ROS levels were increased, while CAT and GPx activities were inhibited, indicating the induction of oxidative stress in zebrafish gills. This was followed by an increase of LPO levels and potential oxidative damage in zebrafish gills. The tryptophan hydroxylase 1a (tph1a) and caspase-3 (casp3) genes were significantly upregulated in Cu25 + MPs group, indicating a potential dysregulation of serotonin synthesis and apoptosis pathways, respectively. Overall, the present study contributes to improving the knowledge about the response of aquatic organisms to MPs and the potential ecological risk that these particles represent to the ecosystems.

Effects and mechanisms of aged polystyrene microplastics on the photodegradation of sulfamethoxazole in water under simulated sunlight

Pharmaceutical and microplastics (MPs) have been frequently detected in aquatic environment. In this study, the effects of polystyrene MPs (PS MPs) with different aging degrees on the photolysis of sulfamethoxazole (SMX) in simulated sunlit water were investigated. The results showed that the presence of PS MPs inhibited the photodegradation of SMX, and the photodegradation rate (k_obs) of SMX was negatively correlated with the aging degree of PS MPs (R² = 0.998). The aged PS MPs would cause light-screening effect, thereby reducing the photodegradation of SMX in sunlit water. Further, the free radical quenching experiment showed that the mechanism for inhibiting the photolysis of SMX was the reduction of the triplet excited state SMX (³SMX*). According to sample characterization, aging PS MPs formed more unsaturated chromophores and produced organic intermediates that enhanced photon absorption. Additionally, aged PS MPs also decreased the types and yields of degradation products of SMX via product analysis. This study provides an insight into the environmental behaviors of SMX and the photochemical roles of aged MPs in sunlit surface waters.

Distribution, biological effects and biofilms of microplastics in freshwater systems - A review

The rapidly rising output and mass use of plastics have made plastics pollution a major environmental problem. Since plastics are persistent in the environment, understanding the migration transformation characteristics of plastics is critical. Given the ever-increasing concern about the environmental risks posed by microplastics, their prevalence, fate, abundance and impact have been intensively studied. Most of these investigations focused on the marine environment, but research on freshwater microplastics is less extensive. This article aims to briefly summarize the research progress of freshwater microplastics, identify existing gaps and draw novel conclusions, so as to provide useful information for the research of freshwater microplastics. Using the statistics and analysis of freshwater microplastics studies in 2016-2021, this review systematically discusses microplastics in globally freshwater systems. The biological effects of microplastics on freshwater organisms were discussed as well. Some potential ecological effects of microplastic biofilms were shown, such as climate change and material circulation. More importantly, we present some unique conclusions. For example, the detection of freshwater microplastics is mainly concentrated in natural freshwater systems, while few are concentrated in artificial freshwater systems. In addition, polystyrene is the main mode for testing the biological effects of freshwater microplastics, and polyethene and polypropylene which are the most common in freshwater environments, have not been taken seriously. We also pointed out that studies on advanced freshwater plants in the topic of biological effects of microplastics still need strengthen.

Recent advances in toxicological research and potential health impact of microplastics and nanoplastics in vivo

As emerging pollutants, direct and indirect adverse impacts of micro(nano)plastics (MPs/NPs) are raising an increasing environmental concern in recent years due to their poor biodegradability and difficulty in recycling. MPs/NPs can act as carriers of bacteria, viruses, or pollutants (such as heavy metals and toxic organic compounds), and may potentially change the toxicity and bioavailability of pollutants. Ingested or attached MPs/NPs can also be transferred from low-trophic level organisms to high-nutrient organisms or even the human body through the food chain transfer process. This article reviews the emerging field of micro- and nanoplastics on organisms, including the separate toxicity and toxicity of compound after the adsorption of organic pollutants or heavy metals, as well as possible mechanism of toxicological effects and evaluate the nano- and microplastics potential adverse effects on human health. The inherent toxic effects MPs/NPs mainly include the following: physical injury, growth performance decrease and behavioral alteration, lipid metabolic disorder, induced gut microbiota dysbiosis and disruption of the gut's epithelial permeability, neurotoxicity, damage of reproductive system and offspring, oxidative stress, immunotoxicity, etc. Additionally, MPs/NPs may release harmful plastic additives and toxic monomers such as bisphenol A, phthalates, and toluene diisocyanate. The vectors' effect also points out the potential interaction of MPs/NPs with pollutants such as heavy metals, polycyclic aromatic hydrocarbons, organochlorine pesticides, polychlorinated biphenyls, perfluorinated compounds, pharmaceuticals, and polybrominated diphenyl ethers. Nevertheless, these potential consequences of MPs/NPs being vectors for contaminants are controversial.