Microplastic pollution research methodologies, abundance, characteristics and risk assessments for aquatic biota in China

Microplastics accumulation in leaf litter: Field evidence for microplastic ingestion and transfer through prey-predatory relationships

Microplastics (MP) contamination of the terrestrial environment is a global concern. The contamination level of MPs in leaf litter and soil fauna that feed on it has not been reported. Moreover, the interspecific relationships among field soil fauna at different trophic levels and their effects on MP loads remain unclear. Thus, we selected a model food chain including a prey-isopod and predatory-spider relationship to evaluate the role of this relationship in the MPs body burden. The results showed that MP concentrations in the fallen leaf litter ranged from 5340 ± 336.15 particles/kg to 10920 ± 432.43 particles/kg dry weight during different seasons of the monitoring year. However, we found MP particles ranged from 1.17 ± 0.25 to 10.11 ± 1.02 particles/ind in isopods and 2.25 ± 0.35 to 4.25 ± 0.35 particles/ind in spiders. All extracted MPs were colored and blue was the most prevalent one. Fiber-shaped polyester (≤500 μm) and (501-1000 μm) were the most common MPs size in tested fauna and leaf litter, respectively. Our findings indicate that MP ingestion by isopods pose a significant risk for higher trophic levels in the terrestrial food chain. Magnification of MPs was observed in the predatory spider with MP concentration increasing from 46.45 ± 16.68 particles/gm wet weight in isopod to 147.51 ± 54.4 particles/gm wet weight in spider, annually. Furthermore, the results indicate that these soil invertebrates may represent a source of MPs to other organisms in the environment.

Micro- and nano-plastics pollution in the marine environment: Progresses, drawbacks and future guidelines

Marine pollution by micro/nanoplastics (M/NPs) has emerged as a critical global issue, with widespread ecological and economic consequences. Numerous studies have investigated M/NPs pollution in marine environments, but there remains a need to assess progress, identify challenges, and propose future strategies. This review provides updated insights into marine M/NPs, including their sources, detection methods, global data from diverse marine ecosystems, and the challenges in mitigating pollution. The review reveals that the ocean harbors approximately 5.25 trillion plastic debris pieces, with a total of 50-75 trillion plastic and microplastic particles, with deep-sea regions containing up to 4 billion plastic microfibers per square kilometer. Human activities, including industrial practices and aquaculture, are major contributors to M/NPs pollution, which threatens 17% of marine species and incurs an economic loss of 6-9 billion USD. M/NPs are found across various marine habitats, including shorelines, sea floors, water columns, biota, and floating debris. Analyzing nanoplastics is particularly challenging due to their heterogeneous aggregation with other contaminants and their much lower concentrations than natural particles. Key drawbacks in addressing M/NPs pollution include inadequate funding, insufficient regulations, and a lack of policy frameworks on the prevalence, distribution, and sources of M/NPs. There is an increasing focus on utilizing innovative technologies such as artificial intelligence (AI) to monitor, assess risks, and predict the spread of M/NPs. Therefore, urgent global cooperation, involving all stakeholders and the general public, is essential. Additionally, integrating scientific and engineering methods, along with AI technologies, is crucial for monitoring and controlling M/NPs pollution and developing sustainable solutions.

Unveiling microplastic pollution: Evaluating the role of Sinotaia quadrata (Caenogastropoda, Viviparidae) as a monitoring tool in freshwater ecosystems

Freshwater species play a key role in monitoring microplastics (MPs) pollution, providing insights into its distribution, accumulation, and potential ecological and human health risks in aquatic ecosystems. This study evaluates the invasive snail Sinotaia quadrata as a potential tool for monitoring MPs pollution in freshwater ecosystems heavily impacted by human activities. Specifically, we examined whether the characteristics of MPs (i.e., shape, color, and chemical composition) found in water and sediment were reflected in those accumulated by S. quadrata, and whether MPs accumulation varied across different snail size classes. MPs were detected in all environmental matrices and snail samples, with fragments and filaments as the dominant shapes, blue, white, and black as the most common colors, and polypropylene, polyethylene, and polyethylene terephthalate as the primary polymers. A significant difference in MPs concentration per gram was found across snail size classes, with smaller snails accumulating more MPs than larger individuals, likely due to higher feeding rates during growth. A positive correlation was observed between snail shell length and weight, while MPs concentration per gram showed significant negative correlations with both parameters. These findings suggest that S. quadrata accumulates MPs from the environment, reflecting local contamination levels. While S. quadrata is an invasive species, this study demonstrates its potential utility in MPs monitoring, particularly in the context of eradication efforts. This approach integrates pollution assessment with invasive species management, offering a broader perspective on the role of biological invasions in environmental monitoring.

Microplastic footprints in sharks and rays: First assessment of microplastic pollution in two cartilaginous fishes, hardnose shark and whitespotted whipray

Microplastic (MP) pollution is an emerging environmental problem worldwide and has caused widespread concern both in terrestrial and aquatic ecosystems due to their potential impacts on the human health, and health of aquatic organisms and the environment. Little is known about the exposure of top marine predators to MP contamination (debris 0.1μm - <5mm, also called MPs). For the first time, MPs have been characterized in carnivore demersal elasmobranch specimens of hardnose shark Carcharhinus macloti, and the whitespotted whipray Maculabatis gerrardi. The specimens were from the Persian Gulf and Sea of Oman, and MPs were extracted from their intestines, gills, and skin. MPs were found in every sampled tissue examined: this is higher pollution than previously reported for elasmobranch. The total MPs for these organs were 12.6 MPs/g body mass of sharks, and 17.8 MPs/g in the whiprays on average. The most common MPs found were fibres (59%), and filaments (35%); pointing towards fishing gears and limited wastewater treatment. Fragments, films, and foams were <2.1 %; a less abundant problem. The most abundant MPs sampled were ∼0.5 mm ≤ L< 1 mm (when the limit of detection was 0.1 mm), and blue was the most common MP color hinting intake due to visual confusion. Polycarbonate and nylon were the most abundant polymers in the MPs recovered. The overall findings show that C. macloti and M. gerrardi are vulnerable to plastic and it reflects the critical state of their habitat.

Seasonal variations and risk assessment of microplastic contamination in agricultural soil and associated macroinvertebrates in Egypt

Contamination by microplastics (MPs) has the potential to rank among the world's most significant environmental issues. Despite the fact that MP contamination is a global problem, little is known about the time variation of MPs in agricultural soil and its faunal communities which represent a key role to risk assessment. This study represents a first field investigation regarding the MP concentrations in agricultural ecosystem in Egypt. Our study investigates the seasonal fluctuations of MPs in soil and its common fauna in a citrus orchard (Citrus sinensis) in Egypt's Sohag Governorate. Moreover, this work aimed to identify how feeding strategies and body size of the selected fauna affect the no. of MPs ingested. The greatest mean concentration of MPs in soil was observed in summer (664 ± 90.20 items/kg) dry weight. However the lowest was recorded in autumn (354 ± 70.92 items/kg). Aporrectodea caliginosa (earthworms) was more contaminated with MPs (6.84 ± 2.5 item/individual annually) than Anisolabis maritima (earwigs) (2.06 ± 0.86 item/individual annually). When comparing between taxa without considering the size of the organisms, earwigs showed higher MPs concentrations (ranged from 117.93 ± 5.23 to 244.38 ± 4.57 items/gm wet weight) than the earthworms (ranged from 25.62 ± 2.43 to 51.66 ± 4.05 items/gm wet weight). Our results found that blue and red colors were the predominant colors in the soil and the selected fauna. Also, polyester fibers (PES) were the most popular type of microplastics, followed by fractions of polyethylene (PE) and polypropylene (PP). Interestingly, the reduction in the MP particles in the present taxa was observed compared to those in the soil. Pollution load index (PLI) value varied across seasons, with the lowest recorded in autumn due to reduced MPs abundance. The Hazard (H) index indicates a moderate risk (level III) due to high polyester abundance and a low hazard score (4) across all seasons. Our results represent a starting point for further studies on the impact of MPs on soil organisms in various agricultural soils.

Microplastics in aquatic ecosystems: Detection, source tracing, and sustainable management strategies

Microplastics (MPs) are emerging contaminants characterized by persistence, cross-media transport, and complex pollutant interactions, posing serious ecotoxicological risks to ecosystems and human health. Effective MPs management requires multi-faced, long-term, strategies involving targeted sampling, quantitative detection, and comprehensive risk assessments, all of which entail significant resource investment. Despite advancements in remediation technologies, a holistic governance framework integrating these innovations remains underdeveloped. This review synthesizes current knowledge on MPs, elaborating on their diverse morphologies, degradation pathways, and their role as vectors for toxic substances. State-of-the-art extraction techniques are evaluated in this article, including micropore adsorption using nanocomposites, alongside the incorporation of advanced analytical tools such as spectroscopic methods, electron microscopy, and bioinformatics to augment environmental forensics. This review also underscores the necessity of formulating robust global policies to regulate MPs pollution and discusses the potential of biodegradation and thermal degradation as sustainable solutions for MPs removal. By promoting an interdisciplinary approach, this review advocates for a coordinated global response, integrating environmental science, policy frameworks, and waste management strategies to mitigate the escalating impact of MPs on ecosystems and human well-being.

Microplastics pollution in the marine environment: A review of sources, impacts and mitigation

Over the past few years, microplastics (MPs) pollution in the marine environment has emerged as a significant environmental concern. Poor management practices lead to millions of tons of plastic waste entering oceans annually, primarily from land-based sources like mismanaged waste, urban runoff, and industrial activities. MPs pollution in marine environments poses a significant threat to ecosystems and human health, as it adsorbs pollutants, heavy metals, and leaches additives such as plasticizers and flame retardants, thus contributing to chemical pollution. The review article provides a comprehensive overview of MPs pollution, its sources, and impacts on marine environments, including human health, detection techniques, and strategies for mitigating microplastic contamination in marine environments. The paper provides current information on microplastic pollution in marine environments, offering insights for researchers, policymakers, and the public, as well as promoting sustainable practices to protect the environment.

Microplastic pollution in commercially important edible marine bivalves: A comprehensive review

Microplastics have become major pollutants in the marine environment and can accumulate in high concentrations, especially in the gut of marine organisms. Unlike other seafood, bivalves are consumed whole, along with their digestive systems, resulting in the transfer of microplastics to humans. Therefore, there is an urgent need to review the status of microplastic pollution in marine bivalves. In this context, this article provides a comprehensive review of the status of microplastic pollution in marine bivalves and the impact of microplastics on the physiology and immunology of marine bivalves. In general, marine bivalves can accumulate high levels of microplastics in a tissue-specific manner. Although microplastic pollution does not cause mortality in bivalves, it can adversely affects bivalves' immunity, byssus production, and reproduction, potentially affecting bivalve populations. This article provides important information that will aid establishing management measures and determining the direction of future research.

Optimizing microplastic treatment in the effluent of biological nutrient removal processes using electrocoagulation: Taguchi experimental design

Microplastics (MPs) have become one of the most critical environmental pollution problems in recent years. Due to the growing abundance of MPs in aquatic environments, extensive research has been conducted and continues to be ongoing to develop effective treatment methods. In this study, the removal of MPs in the effluent of biological wastewater treatment plant (WWTP) was investigated by electrocoagulation (EC) process with aluminum electrodes. Using Taguchi design, the importance of process variables such as pH, current density, and reaction time were evaluated by Analysis of Variance (ANOVA). Statistically, according to F and p values, the most effective parameter for microplastic (MP) removal was current density, followed by pH and reaction time. The R2 value of the created model was found to be above 98%. According to Taguchi results, the optimum process conditions were determined as pH 9, current density 1.905 mA/cm2, and reaction time 15 min and 99% MP removal efficiency was obtained. Under these optimum conditions, the process cost was calculated as 0.049 $/m3 wastewater, considering energy and electrode consumption. As a result of visual analyses, fiber, film, pellet, amorphous, and undefined forms were dominant in WWTP effluent, while only fiber structures were observed after treatment with EC. In this study, it was concluded that the EC process is an alternative treatment method that can be integrated into wastewater treatment plant effluent to achieve MP removal at very low cost and high efficiency. In addition, as a result of this study, it was observed that the EC process can also be used in MP removal by applying it to real wastewater.

Microplastics and phthalate esters contamination in top oceanic predators: A study on multiple shark species in the Pacific Ocean

Marine organisms, especially top predators such as sharks, are susceptible to environmental pollutants like microplastics (MPs) and phthalate esters (PAEs), leading to ecosystem risks. Research on contamination in these apex species is, however, still limited. This study investigated MPs and PAEs in multiple shark species (Isurus oxyrinchus, Alopias superciliosus, Alopias pelagicus, Carcharhinus brevipinna, and Sphyrna zygaena) off Taiwan's eastern coast. Gastric tissue analyses revealed ubiquitous microplastics (2-31 particles), which positively correlated with body lengths and weights for Isurus oxyrinchus. Blue, fiber-shaped (1-2 mm), and rayon-based MPs are likely associated with textile fiber pollution. The PAEs concentration mean was 7035 ± 6829 ng/g, ww, having DEHP and DiNP as primary compounds. This study highlights pervasive contamination in Pacific Ocean sharks, emphasizing anthropogenic impact on top oceanic predators and providing essential insights for food safety and MP accumulation.

Detection of microplastics in zebrafish housing systems: Can microplastic background contamination affect the final results of microplastic-related toxicological tests?

Concentrations of microplastics (MPs) were determined in three commonly used zebrafish housing systems to see if their levels could affect the final results of laboratory microplastic-related toxicology tests. MPs have received notable attention in the last few years, and their toxicology tests have also come to the fore. Zebrafish (Danio rerio), kept in fish housing systems, are widely used as models for MPs studies. Most of these systems contain a significant number of parts made of different polymers. As usage and amortization can erode these parts, MPs might appear in the keeping water or the fish body, which may represent a background load and possibly influence the results of microplastic-related toxicological tests. To take representative water samples from systems, two in-situ filtration techniques, a newly developed peristaltic pump-, and a jet pump-driven method were applied. The collected MP particles were analyzed with a Fourier-transform infrared microscope (detection limit 50 μm), and their possible origin was also investigated. The newly developed technique was more sufficient for sampling as it had a higher MPs recovery, especially in the smaller size range. Polyester, polyethylene and polypropylene were the most frequently detected polymers in the examined fish housing systems, the highest detected concentration was 0.31±0.12 particles/liter (0.22±0.16 μg/liter). These values are negligible compared to the literature data reporting enormously high applied MPs concentrations (104 - 2.21 × 108 particles/liter) during toxicology tests. The results also show that some detected MPs did not originate from the systems, their origin was presumed to be external.

A review of microplastics on anammox: Influences and mechanisms

Microplastics (MPs) are prevalent in diverse environmental settings, posing a threat to plants and animals in the water and soil and even human health, and eventually converged in wastewater treatment plants (WWTPs), threatening the stable operation of anaerobic ammonium oxidation (anammox). Consequently, a comprehensive summary of their impacts on anammox and the underlying mechanisms must be provided. This article reviews the sources and removal efficiency of MPs in WWTPs, as well as the influencing factors and mechanisms on anammox systems. Numerous studies have demonstrated that MPs in the environment can enter WWTPs via domestic wastewater, rainwater, and industrial wastewater discharges. More than 90% of these MPs are found to accumulate in the sludge following their passage through the treatment units of the WWTPs, affecting the characteristics of the sludge and the efficiency of the microorganisms treating the wastewater. The key parameters of MPs, encompassing concentration, particle size, and type, exert a notable influence on the nitrogen removal efficiency, physicochemical characteristics of sludge, and microbial community structure in anammox systems. It is noteworthy that extracellular polymer secretion (EPS) and reactive oxygen stress (ROS) are important impact mechanisms by which MPs exposure affects anammox systems. In addition, the influence of MPs exposure on the microbial community structure of anammox cells represents a crucial mechanism that demands attention. Future research endeavors will delve into additional crucial parameters of MPs, such as shape and aging, to investigate their effects and mechanisms on anammox. Furthermore, the effective mitigation strategies will also be developed. The paper provides a fresh insight to reveal the influences of MPs exposure on the anammox process and its influence mechanisms, and lays the groundwork for further exploration into the influence of MPs on anammox and potential mitigation strategies.

Asian clam Corbicula fluminea as potential biomonitor of microplastics and metal(oid)s in a Patagonian River

This study summarizes the concentration in dry weight (dw) of several metal(oid)s (As, Cd, Cr, Cu, Mn, Ni, Pb, and Zn), as well as the abundance and characteristics of microplastics (MP) in wet weight (ww) of the soft tissues of clam Corbicula fluminea from Chubut River (Patagonia, Argentina). The contents of essential elements were in the following decreasing order: Zn > Mn > Cu > Ni; meanwhile, non-essential elements Cd, Cr and Pb were below the detection limit (<0.5 μg/g dw). A high mean concentration of As (6.1 ± 0.3 μg/g dw) was found, surpassing the maximum allowable limit established by the Argentine Food Code for bivalve molluscs. The number of MP ranged from 0.07 to 1.27 items/ind. and from 0.2 to 2.9 items/g ww. Fibers were the most common shape, mainly transparent. The size of MP ranged from 42 to 1917 μm, accounting for 62 % of MP between 50 and 450 μm. The dominant polymer was PET based on the results of Raman spectroscopy. Based on the widespread distribution of MP in the environment and the wide range of effects on organisms, it is necessary to develop long-term monitoring programs for MP contamination in different environmental matrices. Understanding the bioaccumulation of MP in bivalves is crucial to assess the potential risk to human health through consumption and to the ecosystem. We propose that the widespread Asian clam could serve as a useful biomonitor for MP and As pollution in freshwater and estuarine environments such as the Chubut River.

Microplastics weaken the exoskeletal mechanical properties of Pacific whiteleg shrimp Litopenaeus vannamei

The ubiquitous presence of microplastics (MPs) in aquatic environments poses a significant threat to crustaceans. Although exoskeleton quality is critical for crustacean survival, the impact of MPs on crustacean exoskeletons remains elusive. Our study represents a pioneering effort to characterize the effects of MPs exposure on crustacean exoskeletons. In this study, the mechanical properties of whiteleg shrimp Litopenaeus vannamei exoskeletons were analyzed after exposure to environmentally realistic levels of MPs. Nanoindentation data demonstrated that MPs exposure significantly increased the hardness and modulus of both the carapace and abdominal segments of L. vannamei. Moreover, fractures and embedded MPs were detected on the exoskeleton surface using SEM-EDS analysis. Further analysis demonstrated that the degree of chitin acetylation (DA) in the shrimp exoskeleton, as indicated by FTIR peaks, was reduced by MPs exposure. In addition, exposure to MPs significantly inhibited the muscle Ca2+-ATPase activity and hemolymph calcium levels. Transcriptome and metabolome analyses revealed that the expression levels of genes encoding key enzymes and metabolites in the chitin biosynthetic pathway were significantly affected by MPs exposure. In conclusion, MPs at environmentally relevant concentrations may affect the exoskeletal mechanical properties of L. vannamei through a comprehensive mechanism involving the disruption of the crystalline structure of chitin, assimilation into the exoskeleton, and dysregulation of exoskeleton biosynthesis-related pathways.

Abundance and risk assessment of microplastics in water, sediment, and aquatic insects of the Nile River

Microplastics (MPs) are a serious threat in freshwater environments. The ecological risk and abundance level of MPs in abiotic and biotic compartments of the Nile River haven't been systematically reported. Thus, these issues were highlighted in the present study during different seasons of the sampling year. The results showed that MP concentrations in the river ranged from 2.24 ± 0.6 to 3.76 ± 1.1 particles/L, 298 ± 63 to 520 ± 80 particles/kg dry weight, and 0.081 ± 0.051 to 4.95 ± 2.6 particles/individual in surface water, sediment, and different species of aquatic insects, respectively. All the extracted MPs are colored blue, red, and black. Fiber-shaped polyesters (<500-1500 μm) were the most common MPs in all the river compartments. MPs' dominance was observed during the summer in comparison with that in the other seasons. Environmental risk indicators indicate the high ecological risk of MPs, which are widely distributed in the Nile River. In conclusion, MP consumption by aquatic insects may not only be related to levels of environmental contamination, since other variables, such as taxon size, weight, and particular feeding behavior, may also be significant. Additionally, the presence of MPs in insects (at lower trophic levels) creates the potential for predation-based inter-trophic level transmission. Thus, higher trophic-level investigations of various feeding groups should be carried out to identify any possible harm that MPs cause to various aquatic organisms.

An investigation into the stability and degradation of plastics in aquatic environments using a large-scale field-deployment study

The fragmentation of plastic debris is a key pathway to the formation of microplastic pollution. These disintegration processes depend on the materials' physical and chemical characteristics, but insight into these interrelationships is still limited, especially under natural conditions. Five plastics of known polymer/additive compositions and processing histories were deployed in aquatic environments and recovered after six and twelve months. The polymer types used were linear low density polyethylene (LLDPE), oxo-degradable LLDPE (oxoLLDPE), poly(ethylene terephthalate) (PET), polyamide-6 (PA6), and poly(lactic acid) (PLA). Four geographically distinct locations across Aotearoa/New Zealand were chosen: three marine sites and a wastewater treatment plant (WWTP). Accelerated UV-weathering under controlled laboratory conditions was also carried out to evaluate artificial ageing as a model for plastic degradation in the natural environment. The samples' physical characteristics and surface microstructures were studied for each deployment location and exposure time. The strongest effects were found for oxoLLDPE upon artificial ageing, with increased crystallinity, intense surface cracking, and substantial deterioration of its mechanical properties. However, no changes to the same extent were found after recovery of the deployed material. In the deployment environments, the chemical nature of the plastics was the most relevant factor determining their behaviours. Few significant differences between the four aquatic locations were identified, except for PA6, where indications for biological surface degradation were found only in seawater, not the WWTP. In some cases, artificial ageing reasonably mimicked the changes which some plastic properties underwent in aquatic environments, but generally, it was no reliable model for natural degradation processes. The findings from this study have implications for the understanding of the initial phases of plastic degradation in aquatic environments, eventually leading to microplastics formation. They can also guide the interpretation of accelerated laboratory ageing for the fate of aquatic plastic pollution, and for the testing of aged plastic samples.

Assessment of meso- and microplastics distribution in coastal sediments and waters at the middle estuary of the Rio De La Plata, Argentina (SW Atlantic Ocean)

Estuarine coastal water and sediments collected from multiple locations within the middle Río de la Plata (RDLP) estuary were analyzed in order to identify the presence of microplastics (MPs, <5 mm) and mesoplastics (MePs, 5-25 mm) in one of the most significant estuaries in the Southwestern Atlantic. The present study represents one of the first researches to survey MPs and MePs contamination in key stations at RDLP estuary. Average concentrations of 14.17 ± 5.50 MPs/L and 10.00 MePs/L were detected in water samples, while 547.83 ± 620.06 MPs/kg (dry weight) and 74.23 ± 47.29 MePs/kg d.w. were recorded in sediments. The greatest abundances were observed in the more anthropized areas, near urban settlements. Fibers were the most conspicuous plastic items in water and sediments, followed by fragments. On the other hand, surface sediments, and 50 cm and 100 cm-depth sediments also presented MPs and MePs indicating they could serve as a stratigraphic indicator for recently formed sediments. The main polymer type identified were acrylic fibers, followed by polypropylene (PP) and polyethylene terephthalate (PET). Besides, SEM-EDX detected the presence of Si, Fe, Ti, Al and Cl onto the plastics' surface. These elements may serve as additives to enhance the plastics' properties, such as in the case of Ti, or they could originate from the environment, like biogenic Si or Fe, and Al possibly as a component of the suspended particles or sediments adhered to the micro or meso plastics. Finally, the results of the present study showed that MPs and MePs are commonly found in waters and also tend to be trapped in sediments of the RDLP estuary supporting the assertion that these areas play a substantial role in influencing the transport, dispersion, and buildup of MPs in estuarine regions.

Research progress on occurrence characteristics and source analysis of microfibers in the marine environment

Synthetic microfiber pollution is a growing concern in the marine environment. However, critical issues associated with microfiber origins in marine environments have not been resolved. Herein, the potential sources of marine microfibers are systematically reviewed. The obtained results indicate that surface runoffs are primary contributors that transport land-based microfibers to oceans, and the breakdown of larger fiber plastic waste due to weathering processes is also a notable secondary source of marine microfibers. Additionally, there are three main approaches for marine microplastic source apportionment, namely, anthropogenic source classification, statistical analysis, and numerical simulations based on the Lagrangian particle tracking method. These methods establish the connections between characteristics, transport pathways and sources of microplastics, which provides new insights to further conduct microfiber source apportionment. This study helps to better understand sources analysis and transport pathways of microfibers into oceans and presents a scientific basis to further control microfiber pollution in marine environments.

Occurrence of microplastic pollution in rivers globally: Driving factors of distribution and ecological risk assessment

Microplastics, as global emerging pollutants, have received significant attention worldwide due to their ubiquitous presence in the rivers. However, there is still a lack of clarity on the occurrence, driving factors, and ecological risks of microplastics in rivers worldwide. In this study, a global microplastic dataset based on 862 water samples and 445 sediment samples obtained from 63 articles was constructed, which revealed the temporal and spatial distribution of abundance and morphological characteristics of microplastics in rivers across the globe. In global rivers, the abundance of MPs in both water and sediment spans across 10 and 4 orders of magnitude, respectively. The MP comprehensive diversity index based on the physical morphological characteristics of MPs indicated a significant positive correlation between the pollution sources of MPs in different environmental media. Based on the data was aligned to the full-scale MPs, a novel framework was provided to evaluate the ecological risk of MPs and the interaction effects between the influencing factors driving the distribution characteristics of MPs in rivers around the world. The results obtained demonstrated a wide variation in the key driving factors affecting the distribution of microplastics in different environmental media (water and sediment) in rivers globally. The diversity indices of the morphological characteristics of MPs in densely populated areas of lower-middle income countries in Asia were significantly higher, implying that the sources of microplastics in these regions are more complex and extensive. More than half of the rivers are exposed to potential ecological risks of MPs; however, microplastics may pose only immediate risks to aquatic species in Burigang River, Bangladesh. This can provide valuable insights for formulating more effective scientific strategies for the management of MP pollution in rivers.

Combined effects of a high-fat diet and polyethylene microplastic exposure induce impaired lipid metabolism and locomotor behavior in larvae and adult zebrafish

Microplastics (MP), tiny plastic particles, can be ingested by fish through their habitat or contaminated food sources. When combined with a high-fat diet (HFD), MP exposure may lead to increased MP accumulation in fish and negative impacts on their health. However, the underlying mechanisms of how MP and HFD interact to promote fat accumulation in fish remain poorly understood. In this study, we aimed to evaluate the combined effect of HFD and polyethylene MP (PE-MP) in the zebrafish model (Danio rerio) and decipher its molecular mechanisms. Adult zebrafish exposed to the combined HFD and PE-MP showed elevated lipid accumulation, total cholesterol, triglycerides, and abnormal swimming behavior compared to HFD-fed fish. Histological and gene expression analysis revealed severe hepatic inflammation and injury, resembling nonalcoholic fatty liver disease (NAFLD) in the HFD + PE-MP exposed zebrafish. Moreover, HFD and PE-MP exposure upregulated genes related to lipogenesis (SREBP1, FAS, and C/EBPα) and inflammation (tnfα, il1β, and il-6) in the liver. These findings underscore the interactive effect of environmental pollutants and fish diet, emphasizing the importance of improving fish culture practices to safeguard fish health and human consumers from microplastic contamination through the food chain. This research sheds light on the complex interactions between microplastics and diet, providing valuable insights into the potential risks of microplastic pollution in aquatic ecosystems and the implications for human health. Understanding the underlying molecular mechanisms will contribute to international research efforts to mitigate the adverse effects of microplastics on both environmental and public health.

The effects of polylactic acid bioplastic exposure on midgut microbiota and metabolite profiles in silkworm (Bombyx mori): An integrated multi-omics analysis

Polylactic acid (PLA) is a highly common biodegradable plastic and a potential threat to health and the environment. However, limited data are available on the effects of PLA exposure in the silkworm (Bombyx mori), a model organism used in toxicity studies. In this study, silkworms with or without PLA exposure (P1: 1 mg/L, P5: 5 mg/L, P25: 25 mg/L, and P0: 0 mg/L) for the entire 5th instar period were used to investigate the impact of PLA exposure on midgut morphology, larvae growth, and survival. Mitochondrial damage was observed in the P5 and P25 groups. The weights of the P25 posterior silk gland (5th day in the 5th instar), mature larvae and pupae were all significantly lower than those of the controls (P < 0.05). Dead worm cocoon rates and larva-pupa to 5th instar larvae ratios showed a positive and negative dose-dependent manner with respect to PLA concentrations, respectively. Additionally, reactive oxygen species levels and superoxide dismutase activity of the P25 midgut were significantly higher and lower when compared with controls, respectively (P < 0.05). The molecular mechanisms underlying the effects of PLA and associated physiological responses were also investigated. In the midgut metabolome, 127 significantly different metabolites (variable importance projection >1 and P < 0.05) were identified between the P0 and P25 groups and were mainly enriched for amino acid metabolism and energy supply pathways. The 16 S rDNA data showed that PLA altered microbial richness and structural composition. Microbiota, classified into 34 genera and 63 species, were significantly altered after 25 mg/L PLA exposure (P < 0.05). Spearman's correlation results showed that Bifidobacterium catenulatum and Schaalia odontolytica played potentially vital roles during exposure, as they demonstrated stronger correlations with the significantly different metabolites than other bacterial species. In sum, PLA induced toxic effects on silkworms, especially on energy- and protein-relevant metabolism, but at high concentrations (25 mg/L). This prospective mechanistic investigation on the effects of PLA on larval toxicity provides novel insight regarding the ecological risks of biodegradable plastics in the environment.

Occurrence and distribution of meso- and macroplastics in the water, sediment, and fauna of the Nile River, Egypt

The present study described the most recent findings concerning the abundance and distribution of plastic in water, sediment, and fauna in the Nile River of Upper Egypt as an interesting research point. The findings revealed that plastics were abundant in the water, sediments, fish, and crayfish throughout the sites. The Nagaa Hammadi site has the highest abundance of meso- and macroplastics in its water and sediment. African catfish had the highest abundance of meso- and macroplastics compared to the other species, while Nile tilapia had no meso- or macroplastics in its alimentary canal or gills in all sites. The Edfu site has the highest abundance of mesoplastics in the alimentary canals of African catfish, while the Nagaa Hammadi site has the highest abundance of mesoplastics in the gills, and macroplastics appeared only in the alimentary canal of African catfish from the El-wasta site. Only mesoplastics were found in the crayfish's alimentary canal, with the Nagaa Hammadi site having the highest abundance. No macroplastics were detected in the crayfish's gills or alimentary canal. Additionally, this work lets us understand how plastics behave in freshwater environments, and it is a step toward decision-makers taking appropriate measures to reduce their risk.

Riverine Microplastic Pollution: Insights from Cagayan de Oro River, Philippines

Rivers are vital water sources for humans and homes for aquatic organisms. Conversely, they are well known as the route of plastics into the ocean. Despite being the world's number one emitter of riverine plastics into the ocean, microplastics (MPs), or plastic particles less than 5 mm, in the Philippines' rivers are relatively unexplored. Water samples were collected from six sampling stations along the river channel of the Cagayan de Oro River, one of the largest rivers in Northern Mindanao, Philippines. The extracted microplastics' abundance, distribution, and characteristics were analyzed using a stereomicroscope and Fourier transform infrared spectroscopy (FTIR). The results showed a mean concentration of 300 items/m³ of MPs dominated by blue-colored (59%), fiber (63%), 0.3-0.5 mm (44%), and polyacetylene (48%) particles. The highest concentration of microplastics was recorded near the mouth of the river, and the lowest was in the middle area. The findings indicated a significant difference in MP concentration at the sampling stations. This study is the first assessment of microplastic in a river in Mindanao. The results of this study will aid in formulating mitigation strategies for reducing riverine plastic emissions.

A framework for systematic microplastic ecological risk assessment at a national scale

Microplastic pollution is widespread in terrestrial and aquatic environments; however, a systematic assessment of the ecological risks of microplastics is lacking. This study collected research studies on microplastics in soil, aquatic and sediment environments, and screened 128 articles including 3459 sites to assess the ecological risks posed by microplastics in China following a literature quality assessment. We developed a systematic ecological risk assessment framework for microplastics in terms of spatial characterization, biotoxicity and anthropogenic impacts. The results of the pollution load index indicated that 74% and 47% of the soil and aquatic environments studied, respectively, faced a medium or higher level of pollution. Comparing predicted no effect concentrations (PNEC) and measured environmental concentrations (MECs), revealed that soil (97.70%) and aquatic (50.77%) environmental studies were at serious ecological risk from microplastics. The results of the pressure-state-response model showed that the microplastic pollution in Pearl River Delta was in a high-risk state. In addition, we found that ultraviolet radiation and rainfall exacerbate soil microplastic pollution, and higher river runoff may carry large amounts of microplastic from the source. The framework developed in this study will help assess the ecological risks of microplastics in the region to promote the mitigation of plastic pollution.

Is the petrochemical industry an overlooked critical source of environmental microplastics?

Microplastics (MPs) are ubiquitous in the environment and have been verified to be harmful to organisms. The petrochemical industry is a possible contributor, for it is the primary plastic producer but is not focused on. In this background, MPs in the influent, effluent, activated sludge, and expatriate sludge of a typical petrochemical wastewater treatment plant (PWWTP) were identified by the laser infrared imaging spectrometer (LDIR). It revealed that the abundances of MPs in the influent and effluent were as high as 10310 and 1280 items/L with a removal efficiency of 87.6%. The removed MPs accumulated in the sludge, and the MP abundances in activated and expatriate sludge reached 4328 and 10767 items/g, respectively. It is estimated that 1440,000 billion MPs might be released into the environment by the petrochemical industry in 2021 globally. For the specific PWWTP, 25 types of MPs were identified, among which Polypropylene (PP), Polyethylene (PE), and Silicone resin were dominant. All of the detected MPs were smaller than 350 µm, and those smaller than 100 µm prevailed. As for the shape, the fragment was dominant. The study confirmed the critical status of the petrochemical industry in releasing MPs for the first time.

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.

Source, occurrence, distribution, fate, and implications of microplastic pollutants in freshwater on environment: A critical review and way forward

The generation of microplastics (MPs) has increased recently and become an emerging issue globally. Due to their long-term durability and capability of traveling between different habitats in air, water, and soil, MPs presence in freshwater ecosystem threatens the environment with respect to its quality, biotic life, and sustainability. Although many previous works have been undertaken on the MPs pollution in the marine system recently, none of the study has covered the scope of MPs pollution in the freshwater. To consolidate scattered knowledge in the literature body into one place, this work identifies the sources, fate, occurrence, transport pathways, and distribution of MPs pollution in the aquatic system with respect to their impacts on biotic life, degradation, and detection techniques. This article also discusses the environmental implications of MPs pollution in the freshwater ecosystems. Certain techniques for identifying MPs and their limitations in applications are presented. Through a literature survey of over 276 published articles (2000-2023), this study presents an overview of solutions to the MP pollution, while identifying research gaps in the body of knowledge for further work. It is conclusive from this review that the MPs exist in the freshwater due to an improper littering of plastic waste and its degradation into smaller particles. Approximately 15-51 trillion MP particles have accumulated in the oceans with their weight ranging between 93,000 and 236,000 metric ton (Mt), while about 19-23 Mt of plastic waste was released into rivers in 2016, which was projected to increase up to 53 Mt by 2030. A subsequent degradation of MPs in the aquatic environment results in the generation of NPs with size ranging from 1 to 1000 nm. It is expected that this work facilitates stakeholders to understand the multi-aspects of MPs pollution in the freshwater and recommends policy actions to implement sustainable solutions to this environmental problem.

Abundance and Distribution of Microplastics in Invertebrate and Fish Species and Sediment Samples along the German Wadden Sea Coastline

Monitoring strategies are becoming increasingly important as microplastic contamination increases. To find potentially suitable organisms and sites for biota monitoring in the German Wadden Sea, we collected invertebrates (n = 1585), fish (n = 310), and sediment cores (n = 12) at 10 sites along the coast of Lower Saxony between 2018 and 2020. For sample processing of biota, the soft tissue was digested and the sediment samples additionally underwent a subsequent density separation step. Microplastic particles were identified using Nile red and fluorescence microscopy, followed by polymer composition analysis of a subset of particles via µRaman spectroscopy. All investigated species, sediment cores, and sites contained microplastics, predominantly in the morphology class of fragments. Microplastics were found in 92% of Arenicola marina, 94% of Littorina littorea, 85% of Mytilus edulis, and 79% of Platichthys flesus, ranging from 0 to 248.1 items/g. Sediment core samples contained MPs ranging from 0 to 8128 part/kg dry weight of sediment. In total, eight polymers were identified, predominantly consisting of polyethylene, polyvinylchloride, and polyethylene terephthalate. Considering the sampling, processing, and results, the species Mytilus edulis and Platichthys flesus are suitable species for future microplastic monitoring in biota.

Human occupational exposure to microplastics: A cross-sectional study in a plastic products manufacturing plant

Microplastics are ubiquitous in the natural environment, and their potential impact on health is a key issue of concern. Investigating exposure routes in humans and other living organisms is among the major challenges of microplastics. This study aims to examine the exposure level of plastic factory staff to microplastic particles before and after work shifts through body receptors (hand and facial skin, saliva and hair) in Sirjan, southeast of Iran. Moreover, the effect of face masks, gloves, cosmetics (e.g: face powder cream, lipstick and eye makeup products) and appearance on the exposure level is investigated. In total, 19 individuals are selected during six working days. Then, the collected samples are transferred to the laboratory for filtration, extraction, identification and counting of microplastic particles. Moreover, 4802 microplastic particles (100-5000 μm in size) in strand, polyhedral and spherical shapes and color spectra of white/transparent, black, blue/green, red and purple are observed. The nature of most of the observed samples is fiber with a size ≥1000 μm. Analyzing the selected samples using micro-Raman spectroscopy indicate polyester and nylon are the main identified fibers. Hair and saliva samples have the highest and lowest number of microplastics, respectively. Using gloves and sunscreen among all the participants, wearing a scarf and hair size among women and having a beard and mustache among men could have an effective role in the exposure level to microplastics. Results of this study could reveal the exposure route to microplastic particles in the human body and highlight the importance of providing higher protection to reduce exposure.

Occurrence and distribution of microplastics in wetlands

Presence of microplastic particles has been reported in all over the world, even in remote areas with no human activities. Wetlands are important transitional areas between terrestrial and aquatic systems. However, microplastic pollution in wetlands is less studied than other aquatic ecosystems. In this review, documented researches about microplastic occurrence and distribution in different components of wetland systems (except constructed wetlands) were investigated. In this regard, all available articles from different science databases with the keywords microplastic, wetland and lagoon in title were examined and results were proposed by text, table and diagram, after standardization of data express units. Based on results, wetland ecosystems are prone to microplastic pollution. Based on particle properties, PE/PP and fiber/fragment were the most dominant reported chemical composition and particle shapes, respectively.

Microplastics abundance in abiotic and biotic components along aquatic food chain in two freshwater ecosystems of Pakistan

Contaminants of global concern, microplastics (MPs) have been lately reported to be found almost everywhere. Yet there is limited evidence to suggest if these tiny particles can bioaccumulate and biomagnify along the food chain. The current study was conducted to quantify MPs load in two fresh water bodies i.e. River Ravi (Pakistan) and a fish rearing pond fed with ground water to trace MPs along the food chain including biotic and abiotic components. Samples were taken from air, water, sediments, planktons, fish and avian specimen from both water bodies. Higher MPs were found in all samples taken from river Ravi ranging from 3.0 ± 1.58 MPs items in water to 15.20 ± 3.35 MP items in air as compared to 2.8 ± 1.79 MPs in water to 11.20 ± 1.89 air-borne MP items in fish rearing ponds respectively. The mean value of MP items in the GIT of all species was higher (5.05 ± 2.25) as compared to the respiratory tract (1.57 ± 1.3) suggesting ingestion as main mode of exposure. However, this mode of exposure needs to be further investigated along with other exposure routes. Presence of MPs at all trophic levels under investigation indicates some degree of bioaccumulation of these pollutants in the ecosystems.

Microplastics in sewage sludge: Distribution, toxicity, identification methods, and engineered technologies

Microplastic pollution is becoming a global challenge due to its long-term accumulation in the environment, causing adverse effects on human health and the ecosystem. Sludge discharged from wastewater treatment plants (WWTPs) plays a critical role as a carrier and primary source of environmental microplastic contamination. A significantly average microplastic variation between 1000 and 301,400 particles kg^-1 has been reported in the sludge samples. In recent years, advanced technologies have been successfully applied to address this issue, including adsorption, advanced oxidation processes (AOPs), and membrane bioreactors (MBRs). Adsorption technologies are essential to utilizing novel adsorbents (e.g., biochar, graphene, zeolites) for effectively removing MPs. Especially, the removal efficiency of polymer microspheres from an aqueous solution by Mg/Zn modified magnetic biochars (Mg/Zn-MBC) was obtained at more than 95%. Also, advanced oxidation processes (AOPs) are widely applied to degrade microplastic contaminants, in which photocatalytic by semiconductors (e.g., TiO₂ and ZnO) is a highly suitable approach to promote the degradation reactions owing to strongly hydroxyl radicals (OH*). Biological degradation-aided microorganisms (e.g., bacterial and fungal strains) have been reported to be suitable for removing microplastics. Yet, it was affected by biotic and abiotic factors of the environmental conditions (e.g., pH, light, temperature, moisture, bio-surfactants, microorganisms, enzymes) as well as their polymer characteristics, i.e., molecular weight, functional groups, and crystallinity. Notably, membrane bioreactors (MBRs) showed the highest efficiency in removing up to 99% microplastic particles and minimizing their contamination in sewage sludge. Further, MBRs illustrate the suitability for treating high-strength compounds, e.g., polymer debris and microplastic fibers from complex industrial wastewater. Finally, this study provided a comprehensive understanding of potential adverse risks, transportation pathways, and removal mechanisms of microplastic, which full-filled the knowledge gaps in this field.

Changes in life-history traits, antioxidant defense, energy metabolism and molecular outcomes in the cladoceran Daphnia pulex after exposure to polystyrene microplastics

Ubiquitous plastic pollution is a threat to the organisms' survival and ecosystem functions, especially in aquatic environments. Although there is increasing concern about the toxicity of microplastics, knowledge about the effects of microplastics of diverse sizes and adverse impacts on freshwater organisms is still limited. In the present study, the alteration in life-history traits, antioxidant defense and energy metabolism of the model freshwater zooplankton Daphnia pulex were assessed after chronic exposure to gradient concentrations (0.5, 1, 2 and 4 mg/L) of 500-nm polystyrene microplastics (PS-MPs). Changes in protein abundance were analyzed using proteomics after exposure to 1 mg/L of PS-MPs for 14 days. The results showed that ingested PS-MPs accumulated in the digestive tract of D. pulex. 2 and 4 mg/L of PS-MPs inhibited the survival function and 4 mg/L of PS-MPs reduced the body length of D. pulex after 14 or 21 days of exposure. The exposure did not decrease the fecundity of D. pulex. After 14 days of exposure, PS-MPs changed the antioxidant capacity in a dose-dependent way and all concentrations of PS-MPs induced lipid oxidative damage. Exposure to 500-nm PS-MPs for 14 days decreased glucose and fructose contents and disturbed the lipid transport and utilization in D. pulex. Meanwhile, PS-MPs activated DNA repair and transcription regulation but inhibited lipid metabolism and response to unfolded or misfolded proteins. These results indicated that chronic exposure to 500-nm PS-MPs negatively affected D. pulex and showed similar toxic mechanisms to smaller nano-sized microplastics. Exposure to 500-nm PS-MPs resulted in restricted resources such as inhibited antioxidant capacity or energy metabolisms and D. pulex showed a potential trade-off among life-history traits to maintain fecundity at the cost of self-maintenance. The present study offers perspectives for understanding the differences in ecological effects caused by microplastics of different sizes.

Application of a microplastic trap to the determination of the factors controlling the lakebed deposition of microplastics

Microplastics (MPs) in aquatic environments are hard to degrade, easy to transport, and potentially hazardous to biota. Previous studies of MPs in lakes have shown that their deposition is a significant process controlling both their lateral dispersal from a source, and their concentration within the water column. However, the lakebed depositional rates of MPs have predominantly been determined using laboratory experiments and/or through model simulations that may not fully reflect field conditions. In this paper, lacustrine depositional rates in Lake Ulansuhai were documented using an MP trap that allowed for the assessment and quantification of the depositional rates of MPs of differing size, density, and shape at three sampling sites over five different time periods. The results showed that the downward flux for all types of MPs near the lakebed was correlated with wind speed. Higher wind speeds led to the resuspension of greater amounts of MPs in the lakebed sediments and the transport of greater amounts of MPs from the lake inlet to the lake interior and outlet along the hydrologic flow directions. Consequently, higher wind speeds increased the abundance of MPs at the sediment-water interface and intensified the vertical mixing of MPs in the lake water, resulting in a higher depositional flux of MPs. Particles of differing size, shape, and density exhibited different depositional rates. In general, fragmentary, larger size, and higher density MPs were more likely to be deposited. Thus, size and shape have a strong effect on the migration and deposition of HDMPs in Lake Ulansuhai.

Emerging contaminants migration from pipes used in drinking water distribution systems: a review of the scientific literature

Migration of emerging contaminants (ECs) from pipes into water is a global concern due to potential human health effects. Nevertheless, a review of migration ECs from pipes into water distribution systems is presently lacking. This paper reviews, the reported occurrence migration of ECs from pipes into water distribution systems in the world. Furthermore, the results related to ECs migration from pipes into water distribution systems, their probable sources, and their hazards are discussed. The present manuscript considered the existing reports on migration of five main categories of ECs including microplastics (MPs), bisphenol A (BPA), phthalates, nonylphenol (NP), perfluoroalkyl, and polyfluoroalkyl substances (PFAS) from distribution network into tap water. A focus on tap water in published literature suggests that pipes type used had an important role on levels of ECs migration in water during transport and storage of water. For comparison, tap drinking water in contact with polymer pipes had the highest mean concentrations of reviewed contaminants. Polyvinyl chloride (PVC), polyamide (PA), polypropylene (PP), polyethylene (PE), and polyethylene terephthalate (PET) were the most frequently detected types of microplastics (MPs) in tap water. Based on the risk assessment analysis of ECs, levels of perfluorooctanoic acid (PFOA), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluorohexane sulfonate (PFHxS), and perfluorooctane sulfonate (PFOS) were above 1, indicating a potential non-carcinogenic health risk to consumers. Finally, there are still scientific gaps on occurrence and migration of ECs from pipes used in distribution systems, and this needs more in-depth studies to evaluate their exposure hazards on human health.

A rapid method for extracting microplastics from oily food samples

The increasing evidence of microplastic (MP) contamination influence on aquatic organisms has been extensively reported globally. However, the discussions of extracting MPs from oily food samples are limited, highlighting the pressing need for effective and standardized analytical methods to extract MPs from oily food. Previous methods, such as using acid, alkali or oxidizing solutions as digestion reagents, usually take a long time to digest oily food, increasing the possibility of procedural contamination of MPs in food over time. The objective of this study was to develop a rapid, efficient, economical and simple analytical method to extract MPs from oily food samples. This innovative protocol combines the use of 4 : 1 HNO₃ : H₂O₂ as a digestion reagent to accelerate the digestion within 1 h at 50 °C and hexane as a washing solution to remove the oil adsorbed on the surface of MPs and membranes. Four common types of MPs, namely, polyethylene terephthalate, polyethylene, polystyrene and polypropylene of different sizes were added to oily flours to demonstrate this method. The mean recovery of MPs was 95% ± 2% (range: 93-98%), and no significant changes in color, particle size, surface area and spectrum features were found for all recovered polymers except for PS with minor changes in color and surface. The method was confirmed to be effective on rice, noodles, bean products and various meat samples. All in all, the present method can facilitate the observation and identification of characteristics of MPs, providing an innovative combination method for quantitative and qualitative analyses of MPs in oily food samples.

Microplastics in global bivalve mollusks: A call for protocol standardization

A growing body of evidence shows that microplastic pollution is ubiquitous in bivalve mollusks globally and is of particular concern due to its potential impact on human health. However, non-standardized sampling, processing, and analytical techniques increased the difficulty of direct comparisons among existing studies. Based on 61 peer-reviewed papers, we summarized the current knowledge of microplastics in bivalve mollusks globally and provided an in-depth analysis of factors affecting the outcome of microplastic data, with the main focus on the effects of different species and methodologies. We found no significant differences in microplastic abundance among genera from the same family but significant differences among bivalve families, indicating habitats play an important role in microplastic ingestion by bivalve mollusks. This also provided foundational knowledge for using epifaunal and infaunal bivalves to monitor microplastic pollution in water and sediment, respectively. Recommendations for microplastic monitoring protocol in bivalve mollusks were proposed according to the results of this review, covering (i) a sample size of at least 50 bivalves in the study area, (ii) the use of 10 % KOH as the digestion solution, and (iii) the pore size of a filter membrane of < 5 µm. Acknowledging the need for a standard procedure, more efforts towards protocol standardization used in long-term and large-scale microplastic monitoring programs in bivalve mollusks are needed.

Occurrence of microplastics in gastrointestinal tract of fish from the Gulf of Guinea, Ghana

Over the past decades, there has been a growing concern about microplastics pollution in global aquatic habitats and its potential impact on human health. This study was carried out to determine the presence of microplastics in fish of economic importance in Ghana. Microplastics were found to be abundant in all investigated samples, with 68 % of the fishes contaminated with microplastics and a total of 133 plastic items identified in the fish. The presence of fibers, black coloured particles, and microplastics in the size range of 0.5-1.0 mm was the most abundant in the samples examined. Three polymers specifically, polyethylene, polyvinyl acetate, and polyamide were identified in the study. The presence of microplastics in the fishes investigated may pose severe ecological and health concerns, and hence comprehensive policies targeted at preventing plastic pollution of Ghana's maritime environment is warranted.

Bisphenol A and microplastics weaken the antimicrobial ability of blood clams by disrupting humoral immune responses and suppressing hemocyte chemotactic activity

Robust antimicrobial capability is crucial for marine organisms survival in complex ocean environments. Although the detrimental impacts of emergent pollutants on cellular immune response of marine bivalve mollusks were increasingly documented, the effects of bisphenol A (BPA) and microplastics (MPs) on humoral immune response and hemocyte chemotactic activity remain unclear. Therefore, in this study, the toxicities of BPA and MPs, alone or in combination, to the antimicrobial ability, humoral immune response, and hemocyte chemotactic activity were investigated in the blood clam Tegillarca granosa. Our data demonstrated that exposure of blood clams to BPA, MPs, and BPA-MPs for 2 weeks lead to significant reductions in their survival rates upon pathogenic bacterial challenge, indicating evident impairment of antimicrobial ability. Compared to control, the plasma of pollutant-incubated blood clams exhibited significantly less antimicrobial activity against the growth of V. harveyi, suggesting significant reduction in humoral immune effectors including defensin, lysozyme (LZM), and lectin. Moreover, hemocytes migration across the polycarbonate membrane to the serum containing chamber was markedly arrested by 2-week exposure to BPA, MPs, and BPA-MPs, suggesting a hampered chemotactic activity. In addition, the intracellular contents of ROS and protein carbonyl in hemocytes were markedly induced whereas the expression levels of key genes from the MAPK and actin cytoskeleton regulation pathways were significantly suppressed upon exposure. In this study, it was also found that BPA-MP coexposure was significantly more toxic than single exposures. In summary, our findings revealed that exposure to the pollutants tested possibly impair the antimicrobial ability of blood clam through (1) reducing the inhibitory effect of plasma on bacterial growth, the contents of humoral immune effectors, and the chemotactic activity of hemocytes, (2) interrupting IL-17 activation of MAPK signal pathway, (3) inducing intracellular ROS, elevating protein carbonylation levels, and disrupting actin cytoskeleton regulation in hemocytes.

Environmental behaviors and degradation methods of microplastics in different environmental media

Microplastics, as a group of emerging contaminants, are widely present in environmental media and have the potential to endanger the ecological environment and human health. Due to the inconsistencies and difficulties inherent in the analysis of microplastic particles, global monitoring data on the distribution of microplastics in the environment are still far from sufficient. The fate and migration of microplastics in the environment are also uncertain. Therefore, there have been increasing reviews on the distribution, biological effects, migration, and health risks of microplastics. However, reports focusing on the degradation of microplastics are still rare. Understanding and commanding the environmental behavior of microplastics are of great significance to explore the treatment of microplastic pollution. Although some preliminary studies on microplastics have been carried out, there is still an urgent need to conduct a comprehensive study on environmental behaviors and degradation methods of microplastics in different environmental media. This article summarizes the recent advances on microplastics, basically includes the distribution and ecological impact of microplastics in soil and water environments, then elaborates the migration behavior and influencing factors of microplastics, and focuses on the research progress of microplastics degradation methods. On this basis, the problems existing in the current research and the future development directions have been proposed. This review could provide a more systematic reference for the development and research of microplastics in the future.

Advanced microplastic monitoring using Raman spectroscopy with a combination of nanostructure-based substrates

Micro(nano)plastic (MNP) pollutants have not only impacted human health directly, but are also associated with numerous chemical contaminants that increase toxicity in the natural environment. Most recent research about increasing plastic pollutants in natural environments have focused on the toxic effects of MNPs in water, the atmosphere, and soil. The methodologies of MNP identification have been extensively developed for actual applications, but they still require further study, including on-site detection. This review article provides a comprehensive update on the facile detection of MNPs by Raman spectroscopy, which aims at early diagnosis of potential risks and human health impacts. In particular, Raman imaging and nanostructure-enhanced Raman scattering have emerged as effective analytical technologies for identifying MNPs in an environment. Here, the authors give an update on the latest advances in plasmonic nanostructured materials-assisted SERS substrates utilized for the detection of MNP particles present in environmental samples. Moreover, this work describes different plasmonic materials-including pure noble metal nanostructured materials and hybrid nanomaterials-that have been used to fabricate and develop SERS platforms to obtain the identifying MNP particles at low concentrations. Plasmonic nanostructure-enhanced materials consisting of pure noble metals and hybrid nanomaterials can significantly enhance the surface-enhanced Raman scattering (SERS) spectra signals of pollutant analytes due to their localized hot spots. This concise topical review also provides updates on recent developments and trends in MNP detection by means of SERS using a variety of unique materials, along with three-dimensional (3D) SERS substrates, nanopipettes, and microfluidic chips. A novel material-assisted spectral Raman technique and its effective application are also introduced for selective monitoring and trace detection of MNPs in indoor and outdoor environments.

Graphical abstract

An assessment workflow to recover microplastics from complex biological matrices

A criteria-guided workflow was applied to assess the effectiveness of microplastic separation methods on complex marine biological matrices. Efficacy of four methods (nitric acid, HNO₃, and potassium hydroxide, KOH, digestions, and sodium chloride, NaCl, and potassium iodide, KI, density flotations) was evaluated on four taxa (hard coral, sponge, sea squirt, sea cucumber) using five microplastics (polyethylene, polystyrene, polyethylene terephthalate, PET, polyvinylchloride, rayon). Matrix clarification was only unacceptably low for KOH. PET discoloured regardless of reagent. Rayon threads unravelled into monofilaments after exposure to all reagents, with discolouration also occurring with HNO₃. Recovery rates were overall high, except for dense microplastics treated with NaCl and only KI yielded high rayon recovery efficiency. All polymers were accurately assigned, with subtle spectral changes observed. These results demonstrate specific limitations to separation methods applied to different biological matrices and microplastics and highlight the need to assess their suitability to provide estimates of microplastic contamination.

Sources, concentrations, distributions, fluxes and fate of microplastics in a hypersaline lake: Maharloo, south-west Iran

Hypersaline lakes support unique ecosystems and biogeochemistries but are often subject to anthropogenic pressures from pollution, water abstraction-diversion and climate change. Less understood, however, are the inputs, distributions and impacts of microplastics (MPs) in hypersaline environments. In this study, MPs are determined in water and sediment cores of Maharloo Lake, south-west Iran, and in the anthropogenically-impacted rivers that recharge the lake. MP concentrations in river water ranged from 0.05 MP L^-1 in the headwaters to about 2 MP L^-1 downstream of industrial effluents, with intermediate (but elevated) concentrations observed in the lake. The maximum surface concentration in lake sediment cores was about 860 MP kg^-1, and concentrations displayed a progressive reduction with increasing depth down to 50 cm that are qualitatively consistent with temporal changes in plastic production. The size distribution of MPs was skewed towards the finest fraction (< 100 μm) and the most abundant polymer types were polyethylene terephthalate, polyethylene and nylon. Flux calculations using river water data and published atmospheric deposition data for the region reveal that the atmosphere is, by at least an order of magnitude, the more important source. MPs added to the lake appear to be maintained in suspension by high density water but are subsequently deposited to sediments by encapsulation and nucleation as salts precipitate. In addition, it is proposed that direct atmospheric deposition to sediment takes place on areas that seasonally dry out and are subsequently inundated. The impacts of MPs on hypersaline ecosystems and biomass resources are unknown but warrant investigation.

Characteristics and source-pathway of microplastics in freshwater system of China: A review

China plays a key role in global plastic production, consumption and disposal, which arouses growing concern about microplastics (MPs) contamination in Chinese freshwater systems. However, few reviews have discussed the characteristics of MP pollution in whole freshwater systems at a national scale. In this review, we summarized the characteristics, sources and transport pathways of MPs in Chinese freshwater systems including surface water and sediment. Results showed that current research mainly focused on the middle and lower reaches of the Yangtze River and its tributaries, as well as lakes and reservoirs along the Yangtze River. Large-scale reservoirs, rivers and lakes located in densely populated areas usually showed higher abundances of MPs. The majority of MPs in Chinese surface water and sediment mainly consisted of polyethylene and polypropylene, and the most common morphologies were fibers and fragments. To identify the sources and pathways, we introduced the source-sink-pathway model, and found that sewage system, farmland and aquaculture area were the three most prevalent sinks in freshwater systems in China. The source-sink-pathway model will help to further identify the migration of MPs from sources to freshwater systems.

Microplastic pollution in the surface seawater in Zhongsha Atoll, South China Sea

The prevalence of microplastics in the marine environment has attracted extensive attention. So far, no information is known regarding the temporal and spatial variations of microplastics in Zhongsha Atoll. This study, for the first time, comprehensively investigated the occurrence and distribution of microplastics in the surface seawater in Zhongsha Atoll based on two ocean cruises. The abundances of microplastics measured in the surface seawater of Zhongsha Atoll were in the ranges of not detected (ND) to 67 items/m³, and ND to 160 items/m³ in 2019 and 2020, respectively. All microplastics detected in Zhongsha Atoll were fibers, most of which were transparent and less than 2 mm. Polyethylene terephthalate was the dominating composition of microplastics. These results suggested that sewage, surface runoff, atmospheric deposition by neighboring land, and fishing activities may be the primary pollution sources. This study provides critical information on microplastic pollution in Zhongsha Atoll for the first time, calling for more research in the management of marine plastic debris in the future.

Odor-producing response pattern by four typical freshwater algae under stress: Acute microplastic exposure as an example

Algae-induced odor problems in water have been repeatedly occurred concerns for drinking water quality. However, present researches mostly focus on the odor-producing pattern of algae in normal growth, and there is scarce discussion on those under stress. Microplastics (MPs) pollution have been global concern for their negative ecological impacts and frequently co-occurs with odor-producing algal bloom in freshwaters. Thus, this study aimed to elucidate the effects and mechanisms of MPs as an environmental stress on algal odorant production for good illustration of odor-producing response pattern under stress. Variation in MP size (polystyrene microspheres; 100 nm, 1000 nm and 10 μm) had significant effects on odorant formation (β-cycloidal, 2-methylisopropanol, 2,4-heptandienal and 2,4-decadienal) by four freshwater algae (Microcystis aeruginosa, Pseudanabaena sp., Cyclotella meneghiniana and Melosira varians). The size ratio of MPs over cells (SRMC) was proposed to categorize the size-ratio dependent effects on the algal odorant production. Interestingly, when SRMC was in the range of 0.1-1, there were always promoting effects; when SRMC < 0.1 or SRMC > 1, there exhibited inhibiting effects, and the inhibiting effects of SRMC < 0.1 were far more severe than those of SRMC > 1. The promotion on odorant production in the SRMC range of 0.1-1 was mainly attributed to the increase in cellular yield, which was related to the increased odorant precursors derived from the oxidation products of reactive oxygen species (ROS). Alternatively, the inhibition of odorant production caused by MPs with SRMC < 0.1 was the results of simultaneously inhibiting cellular density and cellular yield, which might be attributed to the cellular internalization of MPs, inducing the extensive toxic effects. This study illustrated the possibilities of MPs in impairing the esthetics of the source water and provided guidance for the future algal odor issues under stress.

Effects of long-term exposure to silver nanoparticles on the structure and function of microplastic biofilms in eutrophic water

Microplastics are frequently detected in natural aquatic systems proximate to populated areas, such as urban rivers and lakes, and can be rapidly colonized by microbial communities. Microplastics and silver nanoparticles (AgNPs) share similar pathways into natural waters and tend to form heteroaggregations. However, very little is known about the long-term impacts on the structure and function of microplastic biofilms when chronically exposed to silver nanoparticles. Thus, the present study assessed the accumulation property of AgNPs on polymethyl methacrylate (PMMA) microplastics via adsorption tests and studied the chronic effects of AgNPs on the structure and function of microplastic biofilms via 30-day microcosmic experiments in eutrophic water. The adsorption tests showed that the biofilms-colonized PMMA microplastics presented the highest adsorption of 0.98 mg/g in the 1 mg/L AgNPs microcosms. After the 30-day exposure, lactic dehydrogenase release and reactive oxygen species generation of PMMA biofilms increased by 33.23% and 23.98% compared to the MPs-control group with no-AgNPs, indicating that the number of dead cells colonizing microplastics significantly increased. Network analysis suggested that the stabilization of the bacterial community declined with the long-term exposure to AgNPs through the reduction of the modularity and average path length of the network. Compared to the MPs-control group, long-term exposure to AgNPs caused cumulatively inhibitory effects on the nitrogen removal and the N₂O emissions in eutrophic water. The isotopomer analysis revealed that the contribution rate of NO₂^- reduction to N₂O emissions was gradually increasing with the AgNPs exposure. Real-time PCR analysis showed that denitrification genes were less sensitive to AgNPs than the nitrification genes, with gene nosZ performed the most negligible response. Overall, our results revealed that long-term exposure to AgNPs could alter biogeochemical cycling involved by microplastic biofilms and cumulatively reduce the self-recovery of the eutrophic ecosystem.

Effects of microplastics on the accumulation and neurotoxicity of methylmercury in zebrafish larvae

Microplastics (MPs) and methylmercury (MeHg) have attracted increasing attention due to ubiquitous occurrence and toxicity. This study aimed to investigate whether MPs could absorb MeHg and thus modify its bioconcentration and neurotoxicity in the zebrafish larvae (Danio rerio). The pseudo-second-order model (R² = 0.989) was found to be suitable for describing the adsorption kinetics of MeHg onto MPs. Compared with Freundlich and Temkin models, the Langmuir isotherm model provided a better fit with the experimental data exhibiting a maximum monolayer adsorption capacity of 54.945 mg/g. These results suggested that adsorption occurs mainly by a chemical process dominated by monolayer adsorption. MPs adsorbed MeHg to form MPs/MeHg complex, which was ingested by zebrafish larvae, and promoted accumulation of MeHg. Thus, the presence of MPs aggravated the reduction of locomotor activity induced by MeHg, and downregulation of neurotransmitters related genes, such as ache, gfap and scl1A3b. Metabolome analysis also revealed disrupted glutathione (GSH) metabolism upon exposure of MeHg alone and in combination with MPs, as reflected by the increased in the ratio of GSH and oxidized glutathione. These effects were also confirmed by upregulation of oxidative stress-related genes, such as sod, sod mt and gpx4a. Collectively, these results indicated that MPs could act as a carrier of MeHg and enhance its accumulation in zebrafish, thereby disrupting locomotor activity by excessive oxidative stress. This study provides a scientific basis for improving health risk assessment of environmental pollutants, particularly those potentially able to adsorb to MPs by virtue of their chemical nature.

The contamination of microplastics in China's aquatic environment: Occurrence, detection and implications for ecological risk

The widespread occurrence of microplastics in aquatic ecosystems that resulted in environmental contamination has attracted worldwide attention. Microplastics pose a potential threat to the growth and health of aquatic organisms, thereby affecting the function of the ecosystems. As one of the top ten countries producing and consuming plastic products globally, China's aquatic ecosystems have been profoundly affected by microplastics. In this review, we have summarized the microplastics contamination in three typical water environments (marine environment, freshwater environment, and wastewater treatment plants) in China, elaborated on the adverse impacts of microplastics on the ecological environment, and evaluated the potential ecological risks exposed to the ecosystem. In addition, the progress of microplastics extraction methods, as the important basis of microplastics related research, in aquatic ecosystems was introduced, especially the difference between the extraction of microplastics from wastewater and sludge samples. At present, most of the research on microplastics focuses on "one point", such as a certain river or wastewater treatment plant. Research on the mitigation and transfer of microplastics among different connected water environments is still lacking. Also, the microscale ecotoxicity caused by microplastics is poorly understood. In the end, we proposed suggestions and perspectives for future research regarding microplastics in the aquatic ecosystems in China.

Assessing the relationship between the abundance of microplastics in sediments, surface waters, and fish in the Iran southern shores

The purpose of this study was to investigate the microplastic (MP) pollution in sediments, surface waters, and four fish species in the northern coast of the Persian Gulf. Sampling was conducted in seven important regions during December 2019. The abundance of MPs was respectively 190 ± 35.5 items/kg dry weight for sediments, 9.28 ± 2.1 items/km² for surface waters, and 0.33 ± 0.05 items/individual for fish. There was no correlation between MP abundance in surface water, sediment, and fish samples. Except for Cynoglossus arel, abundance of isolated MPs did not show significant relationships with body weight, body length, and gastrointestinal tract weight (P > 0.05). MPs were ranged from 0.3 to 5 mm in size and were prevailed by fiber in shape; black, red, and blue in color; and polypropylene and polyethylene in polymer. This study may help in increasing our knowledge regarding MP pollution in marine water systems and biota.