Microplastics as Vectors of Chromium and Lead during Dynamic Simulation of the Human Gastrointestinal Tract

Stressful Effects of Individual and Combined Exposure to Low-Concentration Polylactic Acid Microplastics and Chromium on Marine Medaka Larvae (Oryzias melastigma)

Microplastics and heavy metal pollution frequently co-occur in the marine environment, raising concerns about their potentially harmful impacts on marine fish. This study undertook a comprehensive evaluation of the individual and combined stress effects of polylactide microplastics (PLA-MPs) and chromium (Cr) on marine medaka larvae. Following a 14-day exposure to PLA-MPs (100 μg/L) and Cr (50 μg/L), both individually and in combination, significant increases in heart rate and body length were observed. Notably, the combined exposure to PLA-MPs and Cr caused marked histopathological alterations, including shedding, atrophy, and lysis of the intestinal tissues. Furthermore, both individual and combined exposure induced oxidative stress in fish larvae, leading to changes in various enzyme activity indices. Individual exposure to either PLA-MPs or Cr led to anxious behavior in the larvae, whereas combined exposure not only caused anxious behavior but also altered swimming patterns. These findings suggest that combined exposure to PLA-MPs and Cr can exacerbate the toxic effects on marine medaka larvae.

Beyond surface: Unveiling ecological and economic ramifications of microplastic pollution in the oceans

Every year, the global production of plastic waste reaches a staggering 400 million metric tons (Mt), precipitating adverse consequences for the environment, food safety, and biodiversity as it degrades into microplastics (MPs). The multifaceted nature of MP pollution, coupled with its intricate physiological impacts, underscores the pressing need for comprehensive policies and legislative frameworks. Such measures, alongside advancements in technology, hold promise in averting ecological catastrophe in the oceans. Mandated legislation represents a pivotal step towards restoring oceanic health and securing the well-being of the planet. This work offers an overview of the policy hurdles, legislative initiatives, and prospective strategies for addressing global pollution due to MP. Additionally, this work explores innovative approaches that yield fresh insights into combating plastic pollution across various sectors. Emphasizing the importance of a global plastics treaty, the article underscores its potential to galvanize collaborative efforts in mitigating MP pollution's deleterious effects on marine ecosystems. Successful implementation of such a treaty could revolutionize the plastics economy, steering it towards a circular, less polluting model operating within planetary boundaries. Failure to act decisively risks exacerbating the scourge of MP pollution and its attendant repercussions on both humanity and the environment. Central to this endeavor are the formulation, content, and execution of the treaty itself, which demand careful consideration. While recognizing that a global plastics treaty is not a panacea, it serves as a mechanism for enhancing plastics governance and elevating global ambitions towards achieving zero plastic pollution by 2040. Adopting a life cycle approach to plastic management allows for a nuanced understanding of possible trade-offs between environmental impact and economic growth, guiding the selection of optimal solutions with socio-economic implications in mind. By embracing a comprehensive strategy that integrates legislative measures and technological innovations, we can substantially reduce the influx of marine plastic litter at its sources, safeguarding the oceans for future generations.

Dynamic Stomach Model-Capillary Electrophoresis-ICPMS for Evaluation of Release and Transformation Behaviors of Arsenic Species from Microplastics during Digestion

Microplastics (MPs) can act as carriers of environmental arsenic species into the stomach with food and release arsenic species during digestion, which threatens human health. Herein, an integrated dynamic stomach model (DSM)-capillary electrophoresis-inductively coupled plasma mass spectrometry (CE-ICPMS) is developed for online monitoring of the release and transformation behaviors of arsenic species loaded on MPs (As-MPs) in the simulated human stomach. The 3D-printed DSM with a soft stomach chamber enables the behaviors of gastric peristalsis, gastric and salivary fluid addition, pH adjustment, and gastric emptying (GE) to be controlled by a self-written program after oral ingestion of food with As-MPs. The gastric extract during digestion is introduced into the spiral channel to remove the large particulate impurity and online filtered to obtain the clarified arsenic-containing solution for subsequent speciation analysis of arsenic by CE-ICPMS. The digestion conditions and pretreatment processes of DSM are tracked and validated, and the release rates of As-MPs digested by DSM are compared with those digested by the static stomach model and DSM without GE. The release rate of inorganic arsenic on MPs is higher than that of organic arsenic throughout the gastric digestion process, and 8% of As(V) is reduced to As(III). The detection limits for As(III), DMA, MMA, and As(V) are 0.5-0.9 μg L-1 using DSM-CE-ICPMS, along with precisions of ≤8%. This present method provides an integrated and convenient tool for evaluating the release and transformation of As-MPs during human gastric digestion and provides a reference for exploring the interactions between MPs and metals/metalloids in the human body.

Abiotic weathering of plastic: Experimental contributions towards understanding the formation of microplastics and other plastic related particulate pollutants

The increasing use of plastic (synthetic polymers) results in the release of uncontrollable amounts of synthetic materials into the environment through waste, infrastructure, and essential goods. As plastic materials undergo weathering, a complex process unfolds, leading to the formation of pollutants, notably microplastics. This study employs multiple instrumental methods to explore the intricate abiotic degradation of the five most commonly used synthetic polymers in environmentally relevant conditions. An extensive set of analytical techniques, along with chemometric analysis of the results of Raman spectroscopy, was used to characterize the materials and evaluate the nature and extent of degradation caused by artificial weathering under temperature, humidity, and solar-like irradiation cycles. Investigation focuses on the link between abiotic weathering and the generation of micro- and nanoplastics, accompanied by molecular and surface adhesion changes, and the release of additives such as metals and metal oxides. Research reveals that microplastics may exhibit varied physical properties due to the incorporation of significant quantities of high-density additives from the parent plastic, which might influence the extraction methods and the transportation models' accuracy. At the molecular and microscopic scales, non-homogeneous pathways through which plastic decomposes during weathering were observed. The formation of additive-polymer combinations might play a pivotal role in the monitoring approaches for microplastics, presenting unique challenges in assessing the environmental impact of different plastic types. These findings offer complex insight into abiotic weathering, microplastics' generation, and the influence of additives that were previously overlooked in toxicity and health assessment studies. As plastic pollution continues to escalate, understanding these complex processes is crucial for microplastic monitoring development and adopting effective preventative measures.

Micro(nano)plastics in the Human Body: Sources, Occurrences, Fates, and Health Risks

The increasing global attention on micro(nano)plastics (MNPs) is a result of their ubiquity in the water, air, soil, and biosphere, exposing humans to MNPs on a daily basis and threatening human health. However, crucial data on MNPs in the human body, including the sources, occurrences, behaviors, and health risks, are limited, which greatly impedes any systematic assessment of their impact on the human body. To further understand the effects of MNPs on the human body, we must identify existing knowledge gaps that need to be immediately addressed and provide potential solutions to these issues. Herein, we examined the current literature on the sources, occurrences, and behaviors of MNPs in the human body as well as their potential health risks. Furthermore, we identified key knowledge gaps that must be resolved to comprehensively assess the effects of MNPs on human health. Additionally, we addressed that the complexity of MNPs and the lack of efficient analytical methods are the main barriers impeding current investigations on MNPs in the human body, necessitating the development of a standard and unified analytical method. Finally, we highlighted the need for interdisciplinary studies from environmental, biological, medical, chemical, computer, and material scientists to fill these knowledge gaps and drive further research. Considering the inevitability and daily occurrence of human exposure to MNPs, more studies are urgently required to enhance our understanding of their potential negative effects on human health.

Microplastics and potentially toxic elements: A review of interactions, fate and bioavailability in the environment

In recent years, microplastics (MPs) have obtained growing public concern due to widespread distribution and harmful impacts. Their distinctive features including porous structure, small size, as well as large specific surface area render MPs to be carriers for transporting other pollutants in the environment, especially potentially toxic elements (PTEs). Considering the hot topic of MPs, it is of great significance to comb the reported literature on environmental behaviors of co-occurrence of MPs and PTEs, and systematically discuss their co-mobility, transportation and biotoxicity to different living organisms in diverse environmental media. Therefore, the aim of this work is to systematically review and summarize recent advances on interactions and co-toxicity of MPs and PTEs, in order to provide in-depth understanding on the transport behaviors as well as environmental impacts. Electrostatic attraction and surface complexation mainly govern the interactions between MPs and PTEs, which are subordinated by other physical sorption processes. Besides, the adsorption behaviors are mainly determined by physicochemical properties regarding to different MPs types and various condition factors (e.g., ageing and PTEs concentrations, presence of substances). Generally speaking, recently published papers make a great progress in elucidating the mechanisms, impact factors, as well as thermodynamic and kinetic studies. Bioavailability and bioaccumulation by plant, microbes, and other organisms in both aquatic and terrestrial environment have also been under investigation. This review will shed novel perspectives on future research to meet the sustainable development goals, and obtain critical insights on revealing comprehensive mechanisms. It is crucial to promote efficient approaches on environmental quality improvement as well as management strategies towards the challenge of MPs-PTEs.

Simulated gastrointestinal digestion of polylactic acid (PLA) biodegradable microplastics and their interaction with the gut microbiota

The accumulation of microplastics (MPs) in the environment as well as their presence in foods and humans highlight the urgent need for studies on the effects of these particles on humans. Polylactic acid (PLA) is the most widely used bioplastic in the food industry and medical field. Despite its biodegradability, biocompatibility, and "Generally Recognized As Safe" (GRAS) status, recent animal model studies have shown that PLA MPs can alter the intestinal microbiota; however, to date, no studies have been reported on the possible gut and health consequences of its intake by humans. This work simulates the ingestion of a realistic daily amount of PLA MPs and their pass through the gastrointestinal tract by combining the INFOGEST method and the gastrointestinal simgi® model to evaluate possible effects on the human colonic microbiota composition (16S rRNA gene sequencing analysis) and metabolic functionality (lactic acid and short-chain fatty acids (SCFA) production). Although PLA MPs did not clearly alter the microbial community homeostasis, increased Bifidobacterium levels tended to increase in presence of millimetric PLA particles. Furthermore, shifts detected at the functional level suggest an alteration of microbial metabolism, and a possible biotransformation of PLA by the human microbial colonic community. Raman spectroscopy and field emission scanning electron microscopy (FESEM) characterization revealed morphological changes on the PLA MPs after the gastric phase of the digestion, and the adhesion of organic matter as well as a microbial biofilm, with surface biodegradation, after the intestinal and colonic phases. With this evidence and the emerging use of bioplastics, understanding their impact on humans and potential biodegradation through gastrointestinal digestion and the human microbiota merits critical investigation.

A systematic review of the impacts of exposure to micro- and nano-plastics on human tissue accumulation and health

Micro- and nano-plastics (MNPs) pollution has become a pressing global environmental issue, with growing concerns regarding its impact on human health. However, evidence on the effects of MNPs on human health remains limited. This paper reviews the three routes of human exposure to MNPs, which include ingestion, inhalation, and dermal contact. It further discusses the potential routes of translocation of MNPs in human lungs, intestines, and skin, analyses the potential impact of MNPs on the homeostasis of human organ systems, and provides an outlook on future research priorities for MNPs in human health. There is growing evidence that MNPs are present in human tissues or fluids. Lab studies, including in vivo animal models and in vitro human-derived cell cultures, revealed that MNPs exposure could negatively affect human health. MNPs exposure could cause oxidative stress, cytotoxicity, disruption of internal barriers like the intestinal, the air-blood and the placental barrier, tissue damage, as well as immune homeostasis imbalance, endocrine disruption, and reproductive and developmental toxicity. Limitedly available epidemiological studies suggest that disorders like lung nodules, asthma, and blood thrombus might be caused or exacerbated by MNPs exposure. However, direct evidence for the effects of MNPs on human health is still scarce, and future research in this area is needed to provide quantitative support for assessing the risk of MNPs to human health.

Tackling microplastics pollution in global environment through integration of applied technology, policy instruments, and legislation

Microplastic pollution is a serious environmental problem that affects both aquatic and terrestrial ecosystems. Small particles with size of less than 5 mm, known as microplastics (MPs), persist in the environment and pose serious threats to various species from micro-organisms to humans. However, terrestrial environment has received less attention than the aquatic environment, despite being a major source of MPs that eventually reaches water body. To reflect its novelty, this work aims at providing a comprehensive overview of the current state of MPs pollution in the global environment and various solutions to address MP pollution by integrating applied technology, policy instruments, and legislation. This review critically evaluates and compares the existing technologies for MPs detection, removal, and degradation, and a variety of policy instruments and legislation that can support the prevention and management of MPs pollution scientifically. Furthermore, this review identifies the gaps and challenges in addressing the complex and diverse nature of MPs and calls for joint actions and collaboration from stakeholders to contain MPs. As water pollution by MPs is complex, managing it effectively requires their responses through the utilization of technology, policy instruments, and legislation. It is evident from a literature survey of 228 published articles (1961-2023) that existing water technologies are promising to remove MPs pollution. Membrane bioreactors and ultrafiltration achieved 90% of MPs removal, while magnetic separation was effective at extracting 88% of target MPs from wastewater. In biological process, one kg of wax worms could consume about 80 g of plastic/day. This means that 100 kg of wax worms can eat about 8 kg of plastic daily, or about 2.9 tons of plastic annually. Overall, the integration of technology, policy instrument, and legislation is crucial to deal with the MPs issues.

Insights into interactions of biodegradable and non-biodegradable microplastics with heavy metals

Biodegradable microplastics (BMPs) are considered to be environmentally friendly compared to non-biodegradable plastics (NMPs). However, BMPs are likely to become toxic during their transport because of the adsorption of pollutants (e.g., heavy metals) onto them. This study investigated the uptake of six heavy metals (Cd2+, Cu2+, Cr3+, Ni2+, Pb2+, and Zn2+) by a common BMPs (polylactic acid (PLA)) and compared their adsorption characteristics to those of three types of NMPs (polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC)) for the first time. The order of heavy metal adsorption capacity among the four MPs was PE > PLA > PVC > PP. The findings suggest that BMPs contained more toxic heavy metals than some NMPs. Among the six heavy metals, Cr3+ showed considerably stronger adsorption than other heavy metals in both BMPS and NMPs. The adsorption of heavy metals on MPs can be well explained using the Langmuir isotherm model, while the adsorption kinetic curves showed the best fit to the pseudo-second-order kinetic equation. Desorption experiments revealed that BMPs released a higher percentage of heavy metals (54.6-62.6%) in the acidic environment in a shorter time (~ 6 h) compared to NMPs. Overall, this study provides insights into interactions of BMPs and NMPs with heavy metals and their removal mechanisms in aquatic environment.

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.

How Digestive Processes Can Affect the Bioavailability of PCBs Associated with Microplastics: A Modeling Study Supported by Empirical Data

The transfer kinetics of plastic-associated chemicals during intestinal digestive processes is unknown. Here, we assessed whether digestive processes affect chemical exchange kinetics on microplastics, using an in vitro gut fluid digestive model mimicking the human upper intestinal tract. Chemical exchange kinetics of microplastics were measured for 10 polychlorinated biphenyls (PCBs) as proxies for the broad class of hydrophobic organic chemicals. Following earlier studies, olive oil was used as a proxy for digestible food, under high and low digestive enzyme activities. The micelle-water and oil-water partition coefficients of the 10 PCBs were also determined to evaluate the relative contribution of each gut component to sorb PCBs. A new biphasic and reversible chemical exchange model, which included the digestion process, fitted well to the empirical data. We demonstrate that the digestive processes that break down contaminated food can lead to a substantial increase in chemical concentration in microplastics by a factor of 10-20, thereby reducing the overall chemical bioavailability in the gastrointestinal tract when compared to a scenario without microplastics. Higher enzyme activities result in more chemicals being released by the digested food, thereby resulting in higher chemical concentrations in the microplastics. While the model-calibrated kinetic parameters are specific to the studied scenario, we argue that the mechanism of the reduced bioavailability of chemicals and the modeling tool developed have generic relevance. These digestive processes should be considered when assessing the risks of microplastics to humans and also biomagnification in aquatic food webs.

Polystyrene microplastics reduce Cr(VI) and decrease its aquatic toxicity under simulated sunlight

Microplastics (MPs) serve as vectors for chromium (Cr), influencing its fate and toxicity in aquatic environments, and have attracted much attention recently. However, it is still unknown whether MPs mediate Cr species transformation under sunlight irradiation. This study confirmed that polystyrene (PS) MPs could reduce Cr(VI) to Cr(III) under sunlight irradiation, with a photoreduction rate constant of 0.0023 h^-1. PS MPs-mediated Cr(VI) reduction was predominantly dependent on O₂^•- and simultaneously suppressed by ¹O₂, •OH and ³PS* . Aged PS MPs were exposed to simulated sunlight irradiation for 0, 200, 500, and 800 h, and Cr(VI) reduction was hindered by increased ¹O₂ and •OH formation and light-screening effects (decreased photon absorption). The size, functional groups and concentration of PS MPs and environmental factors (e.g., humic acid, pH, Mg²⁺, Fe³⁺ and O₂) strongly affected Cr(VI) reduction. Furthermore, Cr(VI) reduction induced by PS MPs could occur in reservoir water, and the reduction rate was faster than that in double distilled (DD) water. Correspondingly, PS MPs (1 mg/L) decreased the oxidative stress induced by Cr(VI) to Lemna minor in reservoir water after 96 h of sunlight irradiation. This study provided deep insight into how PS MPs affect Cr species transformations and hazardous effects in realistic aquatic environments under sunlight conditions.

The gut microbiota, a key to understanding the health implications of micro(nano)plastics and their biodegradation

The effects of plastic debris on the environment and plant, animal, and human health are a global challenge, with micro(nano)plastics (MNPs) being the main focus. MNPs are found so often in the food chain that they are provoking an increase in human intake. They have been detected in most categories of consumed foods, drinking water, and even human feces. Therefore, oral ingestion becomes the main source of exposure to MNPs, and the gastrointestinal tract, primarily the gut, constantly interacts with these small particles. The consequences of human exposure to MNPs remain unclear. However, current in vivo studies and in vitro gastrointestinal tract models have shown that MNPs of several types and sizes impact gut intestinal bacteria, affecting gut homeostasis. The typical microbiome signature of MNP ingestion is often associated with dysbiosis and loss of resilience, leads to frequent pathogen outbreaks, and local and systemic metabolic disorders. Moreover, the small micro- and nano-plastic particles found in animal tissues with accumulated evidence of microbial degradation of plastics/MNPs by bacteria and insect gut microbiota raise the issue of whether human gut bacteria make key contributions to the bio-transformation of ingested MNPs. Here, we discuss these issues and unveil the complex interplay between MNPs and the human gut microbiome. Therefore, the elucidation of the biological consequences of this interaction on both host and microbiota is undoubtedly challenging. It is expected that microbial biotechnology and microbiome research could help decipher the extent to which gut microorganisms diversify and MNP-determinant species, mechanisms, and enzymatic systems, as well as become important to understand our response to MNP exposure and provide background information to inspire future holistic studies.

Bioaccessibility of microplastic-associated heavy metals using an in vitro digestion model and its implications for human health risk assessment

Microplastics can act as carriers of heavy metals and may enter humans through ingestion and threaten human health. However, the bioaccessibility of heavy metals associated with microplastics and its implications for human health risk assessments are poorly understood. Therefore, in this study, four typical heavy metals (As(V), Cr(VI), Cd(II), and Pb(II)) and one typical microplastic (polyvinyl chloride, PVC) were chosen to estimate the human health risk of microplastic-associated heavy metals by incorporating bioaccessibility. Significant adsorption of heavy metals was observed with the following order for adsorption capacity: Pb(II) > Cr(VI) > Cd(II) > As(V); the efficiencies for desorption of these four heavy metals from PVC microplastics were all below 10%. The Fourier transform infrared spectroscopy results indicated that the functional groups on the surface of the virgin PVC microplastics did not play an important role in the capture process. Heavy metals in both gastric and small intestinal phases were prone to release from PVC microplastics when bioaccessibility was evaluated with the in vitro SBRC (Soluble Bioavailability Research Consortium) digestion model. In addition, Pb(II) bioaccessibility in the gastric phase was significantly higher than those in the other phases, while As(V), Cr(VI), and Cd(II) bioaccessibilities showed the opposite trend. After incorporating bioaccessibility adjustments, the noncarcinogenic hazards and carcinogenic risks determined were lower than those based on total metal contents. The individual hazard quotients (HQ) and carcinogenic risks (CR) for ingestion of these four heavy metals from PVC microplastics were all lower than the threshold values for adults and children. In summary, this study will provide a new view of the human health risks of heavy metals associated with microplastics.

A Review on Heavy Metal Ion Adsorption on Synthetic Microfiber Surface in Aquatic Environments

Synthetic microfibers (SMFs), tiny particles which gets fragmented from large fragments of large synthetic fibers having less than 10 µm in diameter, have gathered ubiquitously in each and every corner of the earth. After their release into the aquatic environment, they remain there without natural degradation. Furthermore, it can be anticipated that floating units are transported along the food chain leading to bioaccumulation. It has been estimated that approximately 10-20 Mt of large fabric products as garbage enter into aquatic system per annum. Recently, these synthetic fragments have been investigated as transporters of heavy metal ions (HMs) showing different types of interactions. Yet, the underlying mechanism of these types of interaction is not known, especially the factors stimulating this process and how badly they affect biotic communities. Through this article, a detailed survey was carried out on the sources of microfibers and HMs into the aquatic environment, adsorption of different types of HMs on the SMF surface, mechanics favors these HM-MF interactions, particularly highlighting the significant roles of interaction on microbial biofilm formation. Their collaborative effects which possess harmful effects on aquatic as well as terrestrial organisms was also discussed. Lastly, the future investigations should focus on rigorous research in this field. This article to the best of our knowledge briefly describes the current research developments and emphasizes the vital function of the microorganisms on MFs-HMs interactions with the encouragement for rigorous research in this field to reveal accurate mechanisms and decrease the hazards related with MF presence.

Seeking for a perfect (non-spherical) microplastic particle - The most comprehensive review on microplastic laboratory research

In recent decades, much attention has been paid to microplastic pollution, and research on microplastics has begun to grow exponentially. However, microplastics research still suffers from the lack of standardized protocols and methods for investigation of microplastics under laboratory conditions. Therefore, in this review, we summarize and critically discuss the results of 715 laboratory studies published on microplastics in the last five years to provide recommendations for future laboratory research. Analysis of the data revealed that the majority of microplastic particles used in laboratory studies are manufactured spheres of polystyrene ranging in size from 1 to 50 µm, that half of the studies did not characterize the particles used, and that a minority of studies used aged particles, investigated leaching of chemicals from microplastics, or used natural particles as a control. There is a large discrepancy between microplastics used in laboratory research and those found in the environment, and many laboratory studies suffer from a lack of environmental relevance and provide incomplete information on the microplastics used. We have summarized and discussed these issues and provided recommendations for future laboratory research on microplastics focusing on (i) microplastic selection, (ii) microplastic characterization, and (iii) test design of laboratory research on microplastics.

Microplastics as an aquatic pollutant affect gut microbiota within aquatic animals

The adverse impact of microplastics (MPs) on gut microbiota within aquatic animals depends on the overall effect of chemicals and biofilm of MPs. Thus, it is ideal to fully understand the influences that arise from each or even all of these characteristics, which should give us a whole picture of consequences that are brought by MPs. Harmful effects of MPs on gut microbiota within aquatic organisms start from the ingestion of MPs by aquatic organisms. According to this, the present review will discuss the ingestion of MPs and its following results on gut microbial communities within aquatic animals, in which chemical components, such as plastic polymers, heavy metals and POPs, and the biofilm of MPs would be involved. This review firstly analyzed the impacts of MPs on aquatic organisms in detail about its chemical components and biofilm based on previous relevant studies. At last, the significance of field studies, functional studies and complex dynamics of gut microbial ecology in the future research of MPs affecting gut microbiota is discussed.

Uptake and Accumulation of Nano/Microplastics in Plants: A Critical Review

The ubiquitous presence of microplastics (MPs) and nanoplastics (NPs) in the environment is an undeniable and serious concern due to their higher persistence and extensive use in agricultural production. This review highlights the sources and fate of MPs and NPs in soil and their uptake, translocation, and physiological effects in the plant system. We provide the current snapshot of the latest reported studies with the majority of literature spanning the last five years. We draw attention to the potential risk of MPs and NPs in modern agriculture and their effects on plant growth and development. We also highlight their uptake and transport pathways in roots and leaves via different exposure methods in plants. Conclusively, agricultural practices, climate changes (wet weather and heavy rainfall), and soil organisms play a major role in transporting MPs and NPs in soil. NPs are more prone to enter plant cell walls as compared to MPs. Furthermore, transpiration pull is the dominant factor in the plant uptake and translocation of plastic particles. MPs have negligible negative effects on plant physiological and biochemical indicators. Overall, there is a dire need to establish long-term studies for a better understanding of their fate and associated risks mechanisms in realistic environment scenarios for safe agricultural functions.

Coexistence and Adsorption Properties of Heavy Metals by Polypropylene Microplastics

Plastic particles with a diameter of 5 mm or less are called microplastics. Microplastics are one of the primary sources of pollution in the environment. It has been proven that microplastics are also carriers of heavy metals, but there are few studies on their adsorption mechanism. In this study, the adsorption of Pb, Cu, Cd, and Zn by polypropylene (PP) microplastics was analyzed and discussed. The morphology of PP was observed by scanning electron microscopy (SEM), the surface elemental composition of PP was determined by X-ray photoelectron spectroscopy (XPS), and the functional groups of PP were analyzed by Fourier transform infrared spectroscopy (FTIR). The results showed that the adsorption behavior of microplastics to different heavy metals could be balanced in 32 hours. Kinetics experiments showed that the adsorption process could be fitted well by a two-stage dynamic model, and the adsorption of Pb and Cu by PP is greater than that of Cd and Zn. The Freundlich model has the best fitting effect on Pb for the adsorption isothermal results. The Langmuir model showed that the process is favorable for adsorption. The adsorption of mixed heavy metals by microplastics showed that when the concentration of the mixed adsorption mass was low, the presence of a coexistence system promoted the adsorption of Zn and Cu by microplastics. With an increasing concentration, the adsorption of 4 heavy metals by microplastics is inhibited.

Influence of Microplastics on the Mobility, Bioavailability, and Toxicity of Heavy Metals: A Review

Microplastics (MPs) can pose ecological risk to the environment and have the potential to negatively affect human health, raising serious public concerns. It is recognized that MPs could act as a vector for various environmental pollutants including heavy metals and potentially influencing their mobility, fate, and bioavailabilty in the environment. However, knowledge on the mechanisms underpinning the interaction processes between MPs and heavy metals is far from clear. This review discusses the effects of MPs on the adsorption/desorption, speciation and bioavailability, and toxicity of various heavy metals. The present review also systematically identifies the environmental factors (e.g., pH, ionic strength, and organic matters) that could affect their interaction processes. This work aims to establish a meaningful perspective for a comprehensive understanding of the indirect ecological risks of MPs as vectors for contaminants. The work also provides a reference for the development of better regulatory strategies in mitigating the negative effects caused by the co-existence of MPs and heavy metals.

Interactions Between Microplastics and Heavy Metals in Aquatic Environments: A Review

Microplastics (MPs), tiny particles broken down from larger pieces of plastics, have accumulated everywhere on the earth. As an inert carbon stream in aquatic environment, they have been reported as carriers for heavy metals and exhibit diverse interactive effects. However, these interactions are still poorly understood, especially mechanisms driving these interactions and how they pose risks on living organisms. In this mini review, a bibliometric analysis in this field was conducted and then the mechanisms driving these interactions were examined, especially emphasizing the important roles of microorganisms on the interactions. Their combined toxic effects and the potential hazards to human health were also discussed. Finally, the future research directions in this field were suggested. This review summarized the recent research progress in this field and highlighted the essential roles of the microbes on the interactions between MPs and heavy metals with the hope to promote more studies to unveil action mechanisms and reduce/eliminate the risks associated with MP presence.

Lifetime Accumulation of Microplastic in Children and Adults

Human exposure to microplastic is recognized as a global problem, but the uncertainty, variability, and lifetime accumulation are unresolved. We provide a probabilistic lifetime exposure model for children and adults, which accounts for intake via eight food types and inhalation, intestinal absorption, biliary excretion, and plastic-associated chemical exposure via a physiologically based pharmacokinetic submodel. The model probabilistically simulates microplastic concentrations in the gut, body tissue, and stool, the latter allowing validation against empirical data. Rescaling methods were used to ensure comparability between microplastic abundance data. Microplastic (1-5000 μm) median intake rates are 553 particles/capita/day (184 ng/capita/day) and 883 particles/capita/day (583 ng/capita/day) for children and adults, respectively. This intake can irreversibly accumulate to 8.32 × 10³ (90% CI, 7.08 × 10²-1.91 × 10⁶) particles/capita or 6.4 (90% CI, 0.1-2.31 × 10³) ng/capita for children until age 18, and up to 5.01 × 10⁴ (90% CI, 5.25 × 10³-9.33 × 10⁶) particles/capita or 40.7 (90% CI, 0.8-9.85 × 10³) ng/capita for adults until age 70 in the body tissue for 1-10 μm particles. Simulated microplastic concentrations in stool agree with empirical data. Chemical absorption from food and ingested microplastic of the nine intake media based on biphasic, reversible, and size-specific sorption kinetics, reveals that the contribution of microplastics to total chemical intake is small. The as-yet-unknown contributions of other food types are discussed in light of future research needs.