Lifetime Accumulation of Microplastic in Children and Adults

Disturbed Gut-Liver axis indicating oral exposure to polystyrene microplastic potentially increases the risk of insulin resistance

Human uptake abundance of microplastics via various pathways, and they accumulate in human liver, kidney, gut and even placenta (especially with a diameter of 1 μm or less). Recent scientific studies have found that exposure to microplastics causes intestinal inflammation and liver metabolic disorder, but it remains largely unknown that whether the damage and inflammation may cause further development of severe diseases. In this study, we discovered one of such potential diseases that may be induced by the exposure to small-sized microplastics (with a diameter of 1 μm) performing a multi-organ and multi-omics study comprising metabolomics and microbiome approaches. Unlike other animal experiments, the dosing strategy was applied in mice according to the daily exposure of the highly exposed population, which was more environmentally relevant and reflective of real-world human exposure. Our studies on the gut-liver axis metabolism have shown that the crosstalk between the gut and liver ultimately leaded to insulin resistance and even diabetes. We proactively verified this hypothesis by measuring the levels of fasting blood glucose and fasting insulin, which were found significantly elevated in the mice with microplastics exposure. These results indicate the urgent need of large-scale cohort evaluation on epidemiology and prognosis of insulin resistance after microplastics exposure in future.

Exploring the adsorption behavior of benzotriazoles and benzothiazoles on polyvinyl chloride microplastics in the water environment

As a kind of emerging pollutant, microplastics (MPs) play an important role as a carrier for pollutant migration in the water environment. Carried by the MPs, benzotriazoles, and benzothiazoles (collectively referred to as BTs)¹ are ubiquitous water contaminants. In this paper, the adsorption behavior of BTs on polyvinyl chloride (PVC) MPs was first studied systematically to explain the adsorptive mechanisms and the consequential pollution caused by the absorption-desorption process. The studies on kinetics, isotherms, and thermodynamics revealed that the adsorption of BTs on PVC MPs was a multi-rate, heterogeneous multi-layer, and exothermic process, which was affected by external diffusion, intra-particle diffusion, and dynamic equilibrium. The factors including pH, salinity, and particle size also influenced the adsorption process. In the multi-solute system, competitive adsorption would occur between different BTs. The desorption of BTs from PVC MPs was positively associated with the increase of adsorption amount. Based on the results, the adsorption mechanisms of PVC MPs were clarified, involving hydrophobic interaction, electrostatic force, and non-covalent bonds. It was demonstrated that BTs in the water environment could most probably be accumulated and migrated through MPs, and eventually carried into organisms, posing an increased risk to the ecological environment.

Microplastics May Be a Significant Cause of Male Infertility

Due to the problematic degradation properties of plastics, the decomposition of plastic results in the formation of numerous microplastics (MPs), less than 5 mm in diameter. These MPs enter the soil and the ocean, eventually passing through the air, water, or food chain back to the human body and harming human health. In the last 80 years, male semen analysis parameters have shown a significant decline for unknown reasons, speculated to be caused by pollutants. No studies examined the relationship between human MP exposure and male infertility. In this article, we reviewed the relevant animal experimental research literature in recent years and calculated that the minimum human equivalent dose of MPs leading to abnormal male semen quality is 0.016 mg/kg/d. The literature comparison found that MP exposure in Japan and South Korea was close to this value. These results suggest that MPs can affect male semen quality and that MPs may significantly impact male fertility.

From properties to toxicity: Comparing microplastics to other airborne microparticles

Microplastic (MP) debris is considered as a potentially hazardous material. It is omnipresent in our environment, and evidence that MP is also abundant in the atmosphere is increasing. Consequently, the inhalation of these particles is a significant exposure route to humans. Concerns about potential effects of airborne MP on human health are rising. However, currently, there are not enough studies on the putative toxicity of airborne MP to adequately assess its impact on human health. Therefore, we examined potential drivers of airborne MP toxicity. Physicochemical properties like size, shape, ζ-potential, adsorbed molecules and pathogens, and the MP's bio-persistence have been proposed as possible drivers of MP toxicity. Since their role in MP toxicity is largely unknown, we reviewed the literature on toxicologically well-studied non-plastic airborne microparticles (asbestos, silica, soot, wood, cotton, hay). We aimed to link the observed health effects and toxicology of these microparticles to the abovementioned properties. By comparing this information with studies on the effects of airborne MP, we analyzed possible mechanisms of airborne MP toxicity. Thus, we provide a basis for a mechanistic understanding of airborne MP toxicity. This may enable the assessment of risks associated with airborne MP pollution, facilitating effective policymaking and product design.

Distribution and characteristics of microplastics in beach sand near the outlet of a major reservoir in north Mississippi, USA

Plastic debris both affects and is affected by the beaches it accumulates on. Most studies of microplastics (MPs) in beach sand are focused on coastal beaches or beaches of large lakes near population centers. Here, we assessed MP pollution at a sandy beach near the outlet of a major flood control reservoir (Sardis Lake) in a relatively unpopulated area in north Mississippi, USA, focusing on two prominent wrack zones and areas in-between. Putative MPs were isolated by density separation and matrix digestion, and then examined using stereomicroscopy, with a subset of samples additionally analyzed by μ-FTIR. MP abundance (particles/kg ± 1 standard error (SE), n = 15) averaged of 590 ± 360, with 950 ± 100 in the lower wrack zone, 540 ± 40 in the upper wrack zone, and 270 ± 30 in areas between; these differences were statistically significant (p < 0.01). The MPs generally had similar size and shape characteristics across sites. The majority were fibers (64%), followed by fragments (23%), beads (7%) and films (6%), with a slightly greater proportion of fibers in the wrack zones compared to areas in-between. The number of MPs rose dramatically with decreasing size. Beads were only found in the < 500 μm size fraction. Clear and blue were the predominant colors for all MPs. A total of 29 different types of polymers were detected, with more than half of the particles being composed of polyethylene and polyamide, followed by poly(methyl methacrylate), polyethylene terephthalate, polycarbonate, polypropylene, and others; although this distribution varied some depending on size fraction and location. Because there are no major wastewater discharges into Sardis Lake, the source of the MPs is likely degradation of carelessly discarded plastic, as well as atmospheric fallout. Overall, we found that MP concentrations were highest in the wrack zones and influenced by rates and duration of discharge from the reservoir. Thus, like coastal beaches, wrack zones on freshwater beaches along or downstream of reservoirs accumulate both macro- and micro-plastics and are prime locations for plastic cleanup. Finally, we show that MPs made from naturally weathered LDPE plastic film are prone to fragmentation during pretreatment procedures, which may result in its overestimation.

Supposedly identical microplastic particles substantially differ in their material properties influencing particle-cell interactions and cellular responses

Microplastics and its putative adverse effects on environmental and human health increasingly gain scientific and public attention. Systematic studies on the effects of microplastics are currently hampered by using rather poorly characterised particles, leading to contradictory results for the same particle type. Here, surface properties and chemical composition of two commercially available nominally identical polystyrene microparticles, frequently used in effect studies, were characterised. We show distinct differences in monomer content, ζ-potentials and surface charge densities. Cells exposed to particles showing a lower ζ-potential and a higher monomer content displayed a higher number of particle-cell-interactions and consequently a decrease in cell metabolism and proliferation, especially at higher particle concentrations. Our study emphasises that no general statements can be made about the effects of microplastics, not even for the same polymer type in the same size class, unless the physicochemical properties are well characterised.

Key knowledge gaps for One Health approach to mitigate nanoplastic risks

There are increasing concerns over the threat of nanoplastics to environmental and human health. However, multidisciplinary barriers persist between the communities assessing the risks to environmental and human health. As a result, the hazards and risks of nanoplastics remain uncertain. Here, we identify key knowledge gaps by evaluating the exposure of nanoplastics in the environment, assessing their bio-nano interactions, and examining their potential risks to humans and the environment. We suggest considering nanoplastics a complex and dynamic mixture of polymers, additives, and contaminants, with interconnected risks to environmental and human health. We call for comprehensive integration of One Health approach to produce robust multidisciplinary evidence to nanoplastics threats at the planetary level. Although there are many challenges, this holistic approach incorporates the relevance of environmental exposure and multi-sectoral responses, which provide the opportunity to identify the risk mitigation strategies of nanoplastics to build resilient health systems.

Microplastic consumption induces inflammatory signatures in the colon and prolongs a viral arthritis

Global microplastic (MP) contamination and the effects on the environment are well described. However, the potential for MP consumption to affect human health remains controversial. Mice consuming ≈80 μg/kg/day of 1 μm polystyrene MPs via their drinking water showed no weight loss, nor were MPs detected in internal organs. The microbiome was also not significantly changed. MP consumption did lead to small transcriptional changes in the colon suggesting plasma membrane perturbations and mild inflammation. Mice were challenged with the arthritogenic chikungunya virus, with MP consumption leading to a significantly prolonged arthritic foot swelling that was associated with elevated Th1, NK cell and neutrophil signatures. Immunohistochemistry also showed a significant increase in the ratio of neutrophils to monocyte/macrophages. The picture that emerges is reminiscent of enteropathic arthritis, whereby perturbations in the colon are thought to activate innate lymphoid cells that can inter alia migrate to joint tissues to promote inflammation.

Conversion of plastic waste into fuels: A critical review

Plastic wastes have posed serious threats to the environment, including decrease of soil nutrient effectiveness and agricultural production as well as emerge of ecological instability. Fuel conversion from plastic waste is regarded as a promising strategy for its disposal and energy utilization. Plastic wastes can be converted into target fuels by adjusting cracking of chemical bonds. Currently, numerous technologies regarding fuel conversion from plastic wastes have been reported, including conventional pyrolysis, novel heat treatment and advanced oxidation. However, systematic summary and comparative analysis of different technologies are still scarcely reported. In this review, fuel conversion from plastic wastes was summarized comprehensively, highlighting novel heat treatment and advanced oxidation technologies reported in recent years. Furthermore, the superiority and drawbacks of each technology were analyzed, and future prospects of technology application were proposed. With lower reaction temperature and higher-value fuel, novel heat treatment of plastics is more popular than traditional one. Advanced oxidation can be controlled to convert plastics into fuels under room temperature and pressure, guiding the new normal in energy utilization of plastic wastes. This review aims to provide inspiration for energy utilization of solid waste, addressing the issues of white pollution and energy shortage.

The impact of nano/micro-plastics toxicity on seafood quality and human health: facts and gaps

Contamination of the food and especially marine environment with nano/micro-plastic particles has raised serious concern in recent years. Environmental pollution and the resulting seafood contamination with microplastic (MP) pose a potential threat to consumers. The absorption rate of the MP by fish is generally considered low, although the bioavailability depends on the physical and chemical properties of the consumed MP. The available safety studies are inconclusive, although there is an indication that prolonged exposure to high levels of orally administered MP can be hazardous for consumers. This review details novel findings about the occurrence of MP, along with its physical and chemical properties, in the marine environment and seafood. The effect of processing on the content of MP in the final product is also reviewed. Additionally, recent findings regarding the impact of exposure of MP on human health are discussed. Finally, gaps in current knowledge are underlined, and the possibilities for future research are indicated in the review. There is an urgent need for further research on the absorption and bioavailability of consumed MP and in vivo studies on chronic exposure. Policymakers should also consider the implementation of novel legislation related to MP presence in food.

Occurrence, human exposure, and risk of microplastics in the indoor environment

Microplastics (MPs) are a group of emerging contaminants that have attracted increasing scientific and societal attention over the past decade due to their ubiquitous detection in all environmental compartments. So far, most studies on MPs focus on characterizing their occurrence, fate, and impact in the aquatic environment. Therefore, very little is known about the magnitude, patterns, and associated risks of human exposure to MPs, particularly indoors. This is a significant research gap given that people spend most of their time (up to 90%) indoors, which is exacerbated over the past year by COVID-19 lockdown measures. Critical evaluation of the existing literature revealed the presence of MPs at higher concentrations in indoor air and dust (from homes and offices) compared to outdoors. This was attributed to several factors including: indoor MPs sources (e.g. furniture, textiles), increased deposition of atmospheric MPs indoors, and less atmospheric mixing and dilution compared to outdoor air. Current understanding is that indoor human exposure to MPs occurs via a combination of inhalation, ingestion, and dermal contact. Dietary intake was considered the major pathway of human exposure to MPs until recent studies revealed potential high exposure via inhalation. Moreover, exposure via inadvertent dust ingestion and dermal contact cannot be neglected, particularly for young children. This is alarming due to the potential toxic implications of MPs exposure. Early toxicological evidence indicates that small MPs (<20 µm) can cause oxidative stress and inflammation, while particles <5 µm can be engulfed by cells and translocated to accumulate in different organs. Also, there is increasing concern over potential leaching of toxic chemicals used as plastic additives (e.g. plasticizers and flame retardants) upon exposure to MPs due to their large surface area. However, MPs exposure and risk assessment in humans is still in its infancy and more research is necessary to provide the knowledge base required for regulations to protect human health and environment against MPs.

Comparing the effects of polystyrene microplastics exposure on reproduction and fertility in male and female mice

Microplastics (MPs) may have an impact on the reproductive development of humans and mammals. However, any effects of MPs exposure on male and female reproductive systems and fertility are still ambiguous. In this study, male and female C57BL/6 mice were exposed to saline or 0.1 mg/d polystyrene microplastics (PS-MPs) for 30 days or 44 days to determine the effects of MPs on reproductive systems, following which some of the mice were caged for 10 days to mate to test fertility. Another group of mice were given fluorescent PS-MPs to determine the accumulation of MPs. The results show that PS-MPs exposure resulted in more significant accumulation and oxidative stress in the ovary than in the testis. In male mice, the number of viable epididymis sperm and spermatogenic cells in the testes after PS-MPs exposure was significantly reduced, and the rate of sperm deformity increased. In female mice, PS-MPs exposure induced a decrease in ovary size and number of follicles. After exposure to PS-MPs, the levels of Follicle stimulating hormone, Luteinizing hormone and testosterone were reduced, and the estradiol levels increased in the serum of male mice, while the changes in these hormone levels of female mice was the opposite. The mice exposed to PS-MPs had a reduced pregnancy rate and produced fewer embryos. These findings suggest that exposure to PS-MPs damaged the testes and ovaries, induced oxidative stress, altered the serum hormone levels, and induced changes in reproduction and fertility. Female mice appear to be more susceptible to MPs in reproduction and fertility than male mice.

Analysis of Microplastics in Human Feces Reveals a Correlation between Fecal Microplastics and Inflammatory Bowel Disease Status

Human ingestion of microplastics (MPs) is inevitable due to the ubiquity of MPs in various foods and drinking water. Whether the ingestion of MPs poses a substantial risk to human health is far from understood. Here, by analyzing the characteristics of MPs in the feces of patients with inflammatory bowel disease (IBD) and healthy people, for the first time, we found that the fecal MP concentration in IBD patients (41.8 items/g dm) was significantly higher than that in healthy people (28.0 items/g dm). In total, 15 types of MPs were detected in feces, with poly(ethylene terephthalate) (22.3-34.0%) and polyamide (8.9-12.4%) being dominant, and their primary shapes were sheets and fibers, respectively. We present evidence indicating that a positive correlation exists between the concentration of fecal MPs and the severity of IBD. Combining a questionnaire survey and the characteristics of fecal MPs, we conclude that the plastic packaging of drinking water and food and dust exposure are important sources of human exposure to MPs. Furthermore, the positive correlation between fecal MPs and IBD status suggests that MP exposure may be related to the disease process or that IBD exacerbates the retention of MPs. The relative mechanisms deserve further studies. Our results also highlight that fecal MPs are useful for assessing human MP exposure and potential health risks.

Tiered testing of micro- and nanoplastics using intestinal in vitro models to support hazard assessments

The uncertainty of potential risks associated with micro- and nanoplastics (MNPs) are of growing public concern. However, the diversity of MNPs in the environment makes a systematic analysis of potential health effects challenging. New tools and approaches are necessary to investigate biological effects of MNPs. With this quick scoping review, we aim to analyse the suitability of in vitro models for assessing the interaction of MNPs with intestinal cells. Our analysis revealed that currently the majority of in vitro tests are based on the three cell lines Caco-2, HT-29, and HCT-116. They have particularly been used to assess endpoints related to basal cytotoxicity, the internalisation of MNPs and effects on the intestinal barrier. When co-cultured with various cell lines, they also allow to investigate additional effects such as inflammation, metabolic actions and the relevance of the intestinal mucus. However, methodological gaps remain regarding the assessment of a potential accumulation of MNPs, leaching of additives/impurities and in resulting long-term effects as well as cell-type specific toxicities. In addition, only few in vitro studies investigated effects of MNPs on the microbiome. Stem cell-based assays using, for example, the emerging organoid technology are promising for analysing MNP effects on tissue-like structures, while avoiding the particular characteristics of the currently used cancer derived cell lines. The various cell lines and culture techniques can be combined in testing strategies, to better elucidate potential biological interaction of MNPs with biological systems. We suggest to implement a tiered testing strategy, in which monocultures can serve as a tool for high-throughput testing of MNPs. In the next steps co-cultures can be used to assess the potential of a systemic uptake of MNPs and organ-on-a-chip models will provide more reliable insights into relevant doses triggering biological effects. Finally, organoids can help to discover new and more complex reactions initiated by MNPs.

Genotoxic effect of microplastics and COVID-19: The hidden threat

Microplastics (MPs) are ubiquitous anthropogenic contaminants, and their abundance in the entire ecosystem raises the question of how far is the impact of these MPs on the biota, humans, and the environment. Recent research has overemphasized the occurrence, characterization, and direct toxicity of MPs; however, determining and understanding their genotoxic effect is still limited. Thus, the present review addresses the genotoxic potential of these emerging contaminants in aquatic organisms and in human peripheral lymphocytes and identified the research gaps in this area. Several genotoxic endpoints were implicated, including the frequency of micronuclei (MN), nucleoplasmic bridge (NPB), nuclear buds (NBUD), DNA strand breaks, and the percentage of DNA in the tail (%Tail DNA). In addition, the mechanism of MPs-induced genotoxicity seems to be closely associated with reactive oxygen species (ROS) production, inflammatory responses, and DNA repair interference. However, the gathered information urges the need for more studies that present environmentally relevant conditions. Taken into consideration, the lifestyle changes within the COVID-19 pandemic, we discussed the impact of the pandemic on enhancing the genotoxic potential of MPs whether through increasing human exposure to MPs via inappropriate disposal and overconsumption of plastic-based products or by disrupting the defense system owing to unhealthy food and sleep deprivation as well as stress. Overall, this review provided a reference for the genotoxic effect of MPs, their mechanism of action, as well as the contribution of COVID-19 to increase the genotoxic risk of MPs.

A Children's Health Perspective on Nano- and Microplastics

BACKGROUND

Pregnancy, infancy, and childhood are sensitive windows for environmental exposures. Yet the health effects of exposure to nano- and microplastics (NMPs) remain largely uninvestigated or unknown. Although plastic chemicals are a well-established research topic, the impacts of plastic particles are unexplored, especially with regard to early life exposures.

OBJECTIVES

This commentary aims to summarize the knowns and unknowns around child- and pregnancy-relevant exposures to NMPs via inhalation, placental transfer, ingestion and breastmilk, and dermal absorption.

METHODS

A comprehensive literature search to map the state of the science on NMPs found 37 primary research articles on the health relevance of NMPs during early life and revealed major knowledge gaps in the field. We discuss opportunities and challenges for quantifying child-specific exposures (e.g., NMPs in breastmilk or infant formula) and health effects, in light of global inequalities in baby bottle use, consumption of packaged foods, air pollution, hazardous plastic disposal, and regulatory safeguards. We also summarize research needs for linking child health and NMP exposures and address the unknowns in the context of public health action.

DISCUSSION

Few studies have addressed child-specific sources of exposure, and exposure estimates currently rely on generic assumptions rather than empirical measurements. Furthermore, toxicological research on NMPs has not specifically focused on child health, yet children's immature defense mechanisms make them particularly vulnerable. Apart from few studies investigating the placental transfer of NMPs, the physicochemical properties (e.g., polymer, size, shape, charge) driving the absorption, biodistribution, and elimination in early life have yet to be benchmarked. Accordingly, the evidence base regarding the potential health impacts of NMPs in early life remains sparse. Based on the evidence to date, we provide recommendations to fill research gaps, stimulate policymakers and industry to address the safety of NMPs, and point to opportunities for families to reduce early life exposures to plastic. https://doi.org/10.1289/EHP9086.

Development and application of a health-based framework for informing regulatory action in relation to exposure of microplastic particles in California drinking water

Microplastics have been documented in drinking water, but their effects on human health from ingestion, or the concentrations at which those effects begin to manifest, are not established. Here, we report on the outcome of a virtual expert workshop conducted between October 2020 and October 2021 in which a comprehensive review of mammalian hazard studies was conducted. A key objective of this assessment was to evaluate the feasibility and confidence in deriving a human health-based threshold value to inform development of the State of California's monitoring and management strategy for microplastics in drinking water. A tiered approach was adopted to evaluate the quality and reliability of studies identified from a review of the peer-reviewed scientific literature. A total of 41 in vitro and 31 in vivo studies using mammals were identified and subjected to a Tier 1 screening and prioritization exercise, which was based on an evaluation of how each of the studies addressed various quality criteria. Prioritized studies were identified largely based on their application and reporting of dose-response relationships. Given that methods for extrapolating between in vitro and in vivo systems are currently lacking, only oral exposure in vivo studies were identified as fit-for-purpose within the context of this workshop. Twelve mammalian toxicity studies were prioritized and subjected to a Tier 2 qualitative evaluation by external experts. Of the 12 studies, 7 report adverse effects on male and female reproductive systems, while 5 reported effects on various other physiological endpoints. It is notable that the majority of studies (83%) subjected to Tier 2 evaluation report results from exposure to a single polymer type (polystyrene spheres), representing a size range of 0.040 to 20 µm. No single study met all desired quality criteria, but collectively toxicological effects with respect to biomarkers of inflammation and oxidative stress represented a consistent trend. While it was possible to derive a conservative screening level to inform monitoring activities, it was not possible to extrapolate a human-health-based threshold value for microplastics, which is largely due to concerns regarding the relative quality and reliability of current data, but also due to the inability to extrapolate data from studies using monodisperse plastic particles, such as polystyrene spheres to an environmentally relevant exposure of microplastics. Nevertheless, a conservative screening level value was used to estimate a volume of drinking water (1000 L) that could be used to support monitoring activities and improve our overall understanding of exposure in California's drinking water. In order to increase confidence in our ability to derive a human-health-based threshold value in the future, several research recommendations are provided, with an emphasis towards strengthening how toxicity studies should be conducted in the future and an improved understanding of human exposure to microplastics, insights critically important to better inform future risk assessments.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1186/s43591-022-00030-6.

Low abundance of microplastics in commercially caught fish across southern Australia

Plastic pollution has increased significantly in the past decades and is now a major global environmental issue. Plastic objects enter the ocean and are broken down into smaller pieces, while wastewater and runoff also carry microplastics (plastics <5 mm) into the ocean. Plastic has been found in over 700 different species of marine wildlife but little research has examined fish sold for human consumption. We determined the microplastic abundance in nine commercially important, wild-caught fish species purchased from seafood markets across 4000 km of Australia (Western Australia, South Australia, Victoria, Tasmania, New South Wales). For microplastic quantification, fish gastro-intestinal tracts were chemically digested and the amount and type of microplastic identified under a microscope and Fourier transform infrared spectrometer. Across all states, an average of 35.5% of fish samples had at least one piece of microplastic in their gastro-intestinal tract. South Australia had the highest percentage of fish with plastic (49%) and Tasmania the lowest (20%). The average microplastic load was 0.94 piece per fish but ranged from 0 to 17 pieces, with polyolefin identified as the dominant polymer group. Overall, the ingestion of microplastic was widespread across species, locations, diets and habitat niches of fish species investigated, but the average plastic ingestion was less than other similar global studies. This study provides novel insights on the use of fish species from seafood markets to assess environmental contamination by microplastic, as well as an important perspective of the potential for microplastic contamination to enter the human food chain.

Spatiotemporal distribution of microplastics in surface water, biofilms, and sediments in the world's largest drinking water diversion project

Investigations of microplastics have increased exponentially over the past decade, yet no information is currently available on the status of microplastics in strictly regulated, artificial bodies of water. The Middle Route of the South-to-North Water Diversion Project (SNWDP) in China, a highly regulated canal, supplies water to 19 cities and more than 53.10 million residents since 2014, as part of the world's largest inter-basin drinking water diversion project. In this study, the spatiotemporal distribution, characteristics, and polymer types of microplastics were surveyed for the first time in the Middle Route of the SNWDP. On average, microplastics were distributed at abundances of 516 items m-3 in water, 20 items kg-1 in biofilms (wet weight), and 24 items kg-1 in sediments (wet weight), lower than that in other typical inland waters. Both sites and seasons significantly affected microplastic abundance in water, biofilms, and sediments; microplastic abundance in water was also significantly positively correlated with distance to the headwork. The main microplastics in the canal were small (0.05-1 mm) polyethylene terephthalate (PET) fibers. Interestingly, microplastics were concentrated in biofilms, indicating that biofilms could serve as a sink for microplastics in the canal. Vehicular harvester was used to demonstrate the practicality of biofilm harvest to mitigate contamination with microplastics. Our results showed that microplastics are consistently transported long distances through the canal, biofilms play an important role in the fate of microplastics in the canal, and that biofilm harvest could be potentially used to mitigate microplastic pollution.

Microplastics in the Environment: Intake through the Food Web, Human Exposure and Toxicological Effects

Recently, studies on microplastics (MPs) have increased rapidly due to the growing awareness of the potential health risks related to their occurrence. The first part of this review is devoted to MP occurrence, distribution, and quantification. MPs can be transferred from the environment to humans mainly through inhalation, secondly from ingestion, and, to a lesser extent, through dermal contact. As regards food web contamination, we discuss the microplastic presence not only in the most investigated sources, such as seafood, drinking water, and salts, but also in other foods such as honey, sugar, milk, fruit, and meat (chickens, cows, and pigs). All literature data suggest not-negligible human exposure to MPs through the above-mentioned routes. Consequently, several research efforts have been devoted to assessing potential human health risks. Initially, toxicological studies were conducted with aquatic organisms and then with experimental mammal animal models and human cell cultures. In the latter case, toxicological effects were observed at high concentrations of MPs (polystyrene is the most common MP benchmark) for a short time. Further studies must be performed to assess the real consequences of MP contamination at low concentrations and prolonged exposure.

Characterizing the multidimensionality of microplastics across environmental compartments

Understanding the multidimensionality of microplastics is essential for a realistic assessment of the risks these particles pose to the environment and human health. Here, we capture size, shape, area, polymer, volume and mass characteristics of >60,000 individual microplastic particles as continuous distributions. Particles originate from samples taken from different aquatic compartments, including surface water and sediments from the marine and freshwater environment, waste water effluents, and freshwater organisms. Data were obtained using state-of-the-art FTIR-imaging, using the same automated imaging post-processing software. We introduce a workflow with two quality criteria that assure minimum data quality loss due to volumetric and filter area subsampling. We find that probability density functions (PDFs) for particle length follow power law distributions, with median slopes ranging from 2.2 for marine surface water to 3.1 for biota samples, and that these slopes were compartment-specific. Polymer-specific PDFs for particle length demonstrated significant differences in slopes among polymers, hinting at polymer specific sources, removal or fragmentation processes. Furthermore, we provide PDFs for particle width, width to length ratio, area, specific surface area, volume and mass distributions and propose how these can represent the full diversity of toxicologically relevant dose metrics required for the assessment of microplastic risks.

A Review of Human Exposure to Microplastics and Insights Into Microplastics as Obesogens

The ubiquitous exposure of humans to microplastics (MPs) through inhalation of particles in air and ingestion in dust, water, and diet is well established. Humans are estimated to ingest tens of thousands to millions of MP particles annually, or on the order of several milligrams daily. Available information suggests that inhalation of indoor air and ingestion of drinking water bottled in plastic are the major sources of MP exposure. Little is known on the occurrence of MPs in human diet. Evidence is accumulating that feeding bottles and medical devices can contribute to MP exposure in newborns and infants. Biomonitoring studies of human stool, fetus, and placenta provide direct evidence of MP exposure in infants and children. MPs <20 µm were reported to cross biological membranes. Although plastics were once perceived as inert materials, MP exposure in laboratory animals is linked to various forms of inflammation, immunological response, endocrine disruption, alteration of lipid and energy metabolism, and other disorders. Whereas exposure to MPs itself is a concern, MPs can also be sources of exposure to plastic additives and other toxicants. Exposure of human cell lines to MP additives such as phthalates, bisphenols, and organotins causes adverse effects through the activation of nuclear receptors, peroxisome proliferator-activated receptors (PPARs) α, β, and γ, and retinoid X receptor (RXR), leading to oxidative stress, cytotoxicity, immunotoxicity, thyroid hormone disruption, and altered adipogenesis and energy production. The size, shape, chemical composition, surface charge, and hydrophobicity of MPs influence their toxicity. Maternal transfer of MPs to the developing fetus has been demonstrated in exposed laboratory animals and through the analysis of human placenta. In laboratory animal studies, maternal exposure to MPs altered energy and lipid metabolism in offspring and subsequent generations. Moreover, concomitant with the global increase in plastics production, the prevalence of overweight and obesity in human populations has increased over the past five decades, and there is evidence to support the hypothesis that MPs and their additives are potential obesogens. Even though MP exposures are ubiquitous and toxic effects from such exposures are a concern, systematic studies on this topic remain urgently needed.

Are Biobased Plastics Green Alternatives?-A Critical Review

Environmental sustainability is driving an intense search for "green materials". Biobased plastics have emerged as a promising alternative. Their building blocks can now be obtained from diverse biomass, by-products, and organic residues due to the advances in biorefineries and bioprocessing technologies, decreasing the demand for fossil fuel resources and carbon footprint. Novel biobased polymers with high added value and improved properties and functionalities have been developed to apply diverse economic sectors. However, the real opportunities and risks of such novel biobased plastic solutions have raised scientific and public awareness. This paper provides a critical review on the recent advances in biobased polymers chemistry and emerging (bio)technologies that underpin their production and discusses the potential for biodegradation, recycling, environmental safety, and toxicity of these biobased solutions.

Microplastics contamination in food and beverages: Direct exposure to humans

Since microplastics (MPs) bring the potential risks to human health when plastics are ingested, more needs to be known about the presence and abundance of human ingestion of MPs. To address these issues, we reviewed 108 publications in Web of Science concerning abundances, sources, and analytical methods of MPs in human daily intake including fish, salt, drinking water, beverages, package food, and other food. The results demonstrate that aquatic food products (fish and bivalves) present a wide range of 0-10.5 items/g for bivalves and 0-20 items/individual for fish. Salt data in literatures present a concentration of 0-13,629 particles/kg. Drinking water is also a pathway of MPs exposure to human, presenting a concentration range from 0 to 61 particles/L for tap water and 0 to 6292 MPs/L for bottled water. Besides, MPs have been found in beverages, package food, sugar, honey, vegetables, and fruits. Therefore, human intake of MPs via ingestion is a nonnegligible exposure route.