Where is the evidence that human exposure to microplastics is safe?

Biodegradation and bioaugmentation of the co-contamination of chloramphenicol and microplastics by Exiguobacterium sp. CAP4 isolated from a contaminated plastisphere

Microplastics (MPs) and antibiotics are newly emerging contaminants that have heavily accumulated in the environment and are a great cause of concern due to their co-contamination. Although the removal and degradation of individual MPs and antibiotics have been studied in various environments, our understanding of how to eliminate the co-contamination of MPs and antibiotics remains poor. In this study, the biodegradation of both micro polyethylene (mPE) and chloramphenicol (CAP) was analyzed in a wastewater sample. Members of the genera Exiguobacterium, Methanospirillum, Methanosaeta, and Candidatus Nitrocosmicus were proposed as biomarkers in plastisphere, which may contribute to the biodegradation of both contaminants. Notably, Exiguobacterium sp. CAP4 was isolated from the plastisphere and exhibited a high potential to degrade both CAP and mPE. Bioaugmentation with Exiguobacterium sp. CAP4 in mPEs and CAP contaminated wastewater facilitated the biodegradation of both mPE and CAP. This work expands the knowledge base regarding the simultaneous elimination of MPs and antibiotics in situ and identifies a promising bacterial strain for both MP and antibiotic biodegradation.

Concerning influences of micro/nano plastics on female reproductive health: focusing on cellular and molecular pathways from animal models to human studies

The female reproductive system can face serious disorders and show reproductive abnormalities under the influence of environmental pollutants. Microplastics (MPs) and nanoplastics (NPs) as emerging pollutants, by affecting different components of this system, may make female fertility a serious challenge. Animal studies have demonstrated that exposure to these substances weakens the function of ovaries and causes a decrease in ovarian reserve capacity. Also, continuous exposure to micro/nano plastics (MNPs) leads to increased levels of reactive oxygen species, induction of oxidative stress, inflammatory responses, apoptosis of granulosa cells, and reduction of the number of ovarian follicles. Furthermore, by interfering with the hypothalamic-pituitary-ovarian axis, these particles disturb the normal levels of ovarian androgens and endocrine balance and delay the growth of gonads. Exposure to MNPs can accelerate carcinogenesis in the female reproductive system in humans and animal models. Animal studies have determined that these particles can accumulate in the placenta, causing metabolic changes, disrupting the development of the fetus, and endangering the health of future generations. In humans, the presence of micro/nanoplastics in placenta tissue, infant feces, and breast milk has been reported. These particles can directly affect the health of the mother and fetus, increasing the risk of premature birth and other pregnancy complications. This review aims to outline the hazardous effects of micro/nano plastics on female reproductive health and fetal growth and discuss the results of animal experiments and human research focusing on cellular and molecular pathways.

Presence of microplastics in human stomachs

This study presents the first definitive confirmation of microplastic presence in the human stomach, based on samples from 26 cadavers. 97 microplastic particles were extracted from stomach contents, across all 26 individuals, revealing a universal prevalence of microplastics in the cadavers. Morphological analysis of the extracted particles unveiled distinct shapes, with fibers constituting the majority (52.04 %), followed by fragments (39.80 %) and films (8.16 %). The average quantity of microplastics per individual was calculated to be 9.4 ± 10.4 particles, with an estimated daily intake of microplastics at 32.2 particles per day. These figures are lower than estimates derived from both daily microplastic consumption alone and notably, those calculated from stool analyses. Our study also suggests that the breakdown or transformation of microplastics cannot be ruled out during their passage through the digestive tract. Although the number of microplastics in stomach contents reported in this study was even lower than the daily microplastic intake rates reported in the literature, it provides conclusive evidence for the presence of microplastics in the human stomach and provides important preliminary data in terms of the risks that may arise for human health.

Optimization of sample preparation, fluorescence- and Raman techniques for environmental microplastics

Microspectroscopic imaging techniques based on spontaneous Raman scattering, Stimulated Raman Scattering (SRS), or fluorescence (with a selective dye) can be used to detect environmental microplastics (MPs) and determine their chemical as well as physical properties. The present study first focuses on optimizing the sample preparation, including a new design for a density separation apparatus and optimization of the Nile Red staining procedure. Tests were carried out with both white and colored reference materials, as well as environmental MPs in a suspended matter sample from the Rhine river. The new 'MESSY' system has a mean recovery of 95 ± 5.5 % (three polymer materials, in duplicate). The optimized Nile Red staining allows coarse categorization of MPs into "polar" vs. "non-polar" materials based on their Fluorescence Index (emission wavelength), but fluorescent additives in the polymer can cause misclassification. For unambiguous identification of the polymer type, Raman spectroscopy can be used. Even colored polymers, with or without Nile Red staining, were readily identified by Raman spectroscopy using a red laser (785 nm), except for particles containing carbon black. A Deep-UV Raman microscope (ex = 248.6 nm) was constructed, which allowed identification of all colored plastics, even those pigmented with carbon black. Since unsupervised mapping with spontaneous Raman is very slow, point measurements are preferably used after preselection of particles of interest based on fluorescence imaging. SRS is several orders of magnitude faster than spontaneous Raman mapping but requires multiple scans at different z-heights and at multiple wavenumber settings to detect and identify all particles. The results are expected to contribute to the development of suitable methodologies for the detection and identification of environmental microplastics.

Detection and analysis of microplastics in tissues and blood of human cervical cancer patients

Microplastics (MPs) can enter the reproductive system and can be potentially harmful to human reproductive health. In this study, 13 types of microplastics (MPs) were identified in patient blood, cancer samples, and paracarcinoma samples using Raman spectroscopy, with polyethylene, polypropylene and polyethylene-co-polypropylene being the most abundant polymer types. Futher, cotton was also found in our study. The diversity and abundance of MPs were higher in blood samples than in cancerous tissues, and there was a significant positive correlation between diversity (p < 0.05). Furthermore, the diversity and abundance of MPs in cancerous tissues were higher than in paracancerous tissues. The dimensional sizes of MPs in these samples were also very similar, with the majority of detected MPs being smaller in size. Correlation analysis showed that patient's age correlated with the abundance of MPs in blood samples, body mass index (BMI) correlated with the abundance of MPs in cancerous tissues. Notably, the frequency with which patients consume bottled water and beverages may also increase the abundance of MPs. This study identifies for the first time the presence of MPs and cotton in cancerous and paracancerous tissues of human cervical cancer patients. This provides new ideas and basic data to study the risk relationship between MP exposure and human health.

Re-thinking human interactions with the oceans

Earth's marine ecosystems are changing rapidly, in large part owing to the damaging effects of human activities. Unless humans find better ways of interacting with the seas and oceans, the marine resources upon which we rely will diminish as more ecosystems collapse. The consequences for human health and wellbeing will be severe. The meta-discipline of Oceans and Human Health has catalogued how the oceans and their constituents benefit human lives. Examples include access to seafood, pharmaceuticals and physical and mental health benefits. This interdisciplinary research effort has also revealed how the integrated impact of anthropogenic activities has disrupted ocean processes resulting in extensive losses of marine biodiversity, increasing chemical and microbial pollution, proliferation of harmful algal blooms and increased coastal inundation, all of which threaten human populations. In response, non-governmental organizations and national governments have established various agreements and treaties to prevent further damage, restore what has been lost and grasp new economic opportunities. Nevertheless, ocean-related risks continue to escalate rapidly in the absence of political commitment. New thinking regarding the interconnectedness of all human/ocean interactions is required to remove the barriers and impediments that hamper tackling the wicked problem of fostering health and wellbeing while achieving ocean sustainability.

Discovery and analysis of microplastics in human bone marrow

The health implications of human exposure to microplastics (MPs) have raised significant concerns. While evidence indicates MPs can accumulate in closed human organs like the heart, placenta, and blood, there is no available data on MP exposure specifically within the human bone marrow. To fill the research gap, this study detected the concentration of microplastics (MPs) in bone marrow samples by pyrolysis gas chromatography-mass spectrometry (Py-GC/MS) and assessed the size range and morphological characteristics of MPs by Laser Direct Infrared Spectroscopy (LD-IR) and scanning electron microscopy (SEM). Our study shows that MPs were present in all 16 bone marrow samples, with an average concentration of 51.29 µg/g ranging from 15.37 µg/g to 92.05 µg/g. Five polymer types-polyethylene (PE), polystyrene (PS), polyvinyl chloride (PVC), polyadiohexylenediamine 66 (PA66), and polypropylene (PP), were identified. PE was the most frequent polymer detected in the bone marrow, with an average concentration of 30.02 µg/g ranging from 14.77 µg/g to 52.57 µg/g, with a detection rate of 93.75 %. PS had the highest detection rate at 100 % of bone marrow samples, while PVC and PA66 were found in 75 % of samples each. LD-IR analysis revealed the identification of 25 polymer types, with an average abundance of 19.72 particles/g. Of these, 89.82 % of the MPs were smaller than 100 µm. In summary, this study has, for the first time, demonstrated the presence of MPs are deeply embedded within human bone marrow, providing a basis for future investigations into their potential toxicological effects and underlying mechanisms affecting the hematopoietic system.

Degradation of PET microplastic particles to monomers in human serum by PETase

More than 8 billion tons of plastic waste has been generated, posing severe environmental consequences and health risks. Due to prolonged exposure, microplastic particles are found in human blood and other bodily fluids. Despite a lack of toxicity studies regarding microplastics, harmful effects for humans seem plausible and cannot be excluded. As small plastic particles readily translocate from the gut to body fluids, enzyme-based treatment of serum could constitute a promising future avenue to clear synthetic polymers and their corresponding oligomers via their degradation into monomers of lower toxicity than the material they originate from. Still, whereas it is known that the enzymatic depolymerization rate of synthetic polymers varies by orders of magnitude depending on the buffer and media composition, the activity of plastic-degrading enzymes in serum was unknown. Here, we report how an engineered PETase, which we show to be generally trans-selective via induced fit docking, can depolymerize two different microplastic-like substrates of the commodity polymer polyethylene terephthalate (PET) into its non-toxic monomer terephthalic acid (TPA) alongside mono(2-hydroxyethyl)terephthalate (MHET) in human serum at 37 °C. We show that the application of PETase does not influence cell viability in vitro. Our work highlights the potential of applying biocatalysis in biomedicine and represents a first step towards finding a future solution to the problem that microplastics in the bloodstream may pose.

Unveiling the ecotoxicological impact of microplastics on organisms - the persistent organic pollutant (POP): A comprehensive review

Microplastics have been ubiquitous in our environment for decades, and numerous studies have revealed their extensive dispersion, reaching far beyond the surface of the land, soil, aquatic ecosystems. They have infiltrated the food-chain, the food web, even the air we breathe, as well as the water we drink. Microplastics have been detected in the food we consume, acting as vectors for hazardous chemicals that adhere to their hydrophobic surfaces. This can result in the transfer of these chemicals to the aquatic life, posing a threat to their well-being. The release of microplastics into different environmental settings can give rise to various eco-toxicological implications. The substantial body of literature has led scientists to the consensus that microplastic pollution is a global problem with the potential to impact virtually any type of ecosystem. This paper aims to discuss crucial information regarding the occurrence, accumulation, and ecological effects of microplastics on organisms. It also highlights the new and emerging disease named "Plasticosis" that is directly linked to microplastics and its toxicological effects like permanent scarring and long-term inflammation in the digestive system of the seabirds. By comprehending the behaviour of these microplastic pollutants in diverse habitats and evaluating their ecological consequences, it becomes possible to facilitate a better understanding of this toxicological issue.

Bibliometrics analysis of hotspots research on infertility syndromes and polystyrene

Polystyrene plastic pollution poses a pressing environmental concern and represents a significant risk factor for infertility. Despite this, a comprehensive overview of the field remains scarce, with future trends largely unknown. Bibliometrics, an applied mathematical and statistical method, offers a means to analyze textual information across various levels, facilitating quantitative assessments of all knowledge carriers and unveiling the nature and developmental trajectories of a discipline. This study aimed to employ bibliometric methods to scrutinize the current status and research hotspots within the realm of polystyrene and infertility. Literature spanning from 1980 to 2023 pertaining to polystyrene and infertility was retrieved from the core database of Web of Science. Quantitative analyses were conducted utilizing CiteSpace (version 5.7.R7), VOSviewer (version 1.6.18.0), and an online literature analysis website (https://bibliometric.com/). The analysis visually represented countries, institutions, authors, journals, and keywords within the field. This study delved into the development history, knowledge structure, research hotspots, and potential trends in the field, furnishing a macro perspective for researchers. The investigation encompassed 267 articles published across 120 journals by 1,352 authors affiliated with 417 institutions in 51 countries, with these articles garnering 10,310 citations across 2,811 journals. The top three countries contributing the most articles were China, the United States, and Germany. In essence, the research hotspots primarily revolved around metabolism, endocrinology, and immunity. Despite China's relatively recent entry into this field, its rapid development is evident. However, the low citation frequency suggests a need for improved article quality.

Single exposure of food-derived polyethylene and polystyrene microplastics profoundly affects gut microbiome in an in vitro colon model

Microplastics (MPs) are widespread contaminants highly persistent in the environment and present in matrices to which humans are extensively exposed, including food and beverages. MP ingestion occurs in adults and children and is becoming an emerging public health issue. The gastrointestinal system is the most exposed to MP contamination, which can alter its physiology starting from changes in the microbiome. This study investigates by an omic approach the impact of a single intake of a mixture of polyethylene (PE) and polystyrene (PS) MPs on the ecology and metabolic activity of the colon microbiota of healthy volunteers, in an in vitro intestinal model. PE and PS MPs were pooled together in a homogeneous mix, digested with the INFOGEST system, and fermented with MICODE (multi-unit in vitro colon model) at loads that by literature correspond to the possible intake of food-derived MPs of a single meal. Results demonstrated that MPs induced an opportunistic bacteria overgrowth (Enterobacteriaceae, Desulfovibrio spp., Clostridium group I and Atopobium - Collinsella group) and a contextual reduction on abundances of all the beneficial taxa analyzed, with the sole exception of Lactobacillales. This microbiota shift was consistent with the changes recorded in the bacterial metabolic activity.

Inhalation of Microplastics-A Toxicological Complexity

Humans are chronically exposed to airborne microplastics (MPs) by inhalation. Various types of polymer particles have been detected in lung samples, which could pose a threat to human health. Inhalation toxicological studies are crucial for assessing the effects of airborne MPs and for exposure-reduction measures. This communication paper addresses important health concerns related to MPs, taking into consideration three levels of complexity, i.e., the particles themselves, the additives present in the plastics, and the exogenous substances adsorbed onto them. This approach aims to obtain a comprehensive toxicological profile of deposited MPs in the lungs, encompassing local and systemic effects. The physicochemical characteristics of MPs may play a pivotal role in lung toxicity. Although evidence suggests toxic effects of MPs in animal and cell models, no established causal link with pulmonary or systemic diseases in humans has been established. The transfer of MPs and associated chemicals from the lungs into the bloodstream and/or pulmonary circulation remains to be confirmed in humans. Understanding the toxicity of MPs requires a multidisciplinary investigation using a One Health approach.

Assessment of human dermal absorption of flame retardant additives in polyethylene and polypropylene microplastics using 3D human skin equivalent models

To overcome ethical and technical challenges impeding the study of human dermal uptake of chemical additives present in microplastics (MPs), we employed 3D human skin equivalent (3D-HSE) models to provide first insights into the dermal bioavailability of polybrominated diphenyl ether (PBDEs) present in MPs; and evaluated different factors influencing human percutaneous absorption of PBDEs under real-life exposure scenario. PBDEs were bioavailable to varying degrees (up to 8 % of the exposure dose) and percutaneous permeation was evident, albeit at low levels (≤0.1 % of the exposure dose). While the polymer type influenced the release of PBDEs from the studied MPs to the skin, the polymer type was less important in driving the percutaneous absorption of PBDEs. The absorbed fraction of PBDEs was strongly correlated (r2 = 0.88) with their water solubility, while the dermal permeation coefficient Papp of PBDEs showed strong association with their molecular weight and logKOW. More sweaty skin resulted in higher bioavailability of PBDEs from dermal contact with MPs than dry skin. Overall, percutaneous absorption of PBDEs upon skin contact with MPs was evident, highlighting, for the first time, the potential significance of the dermal pathway as an important route of human exposure to toxic additive chemicals in MPs.

Evidence of internalized microplastics in mussel tissues detected by volumetric Raman imaging

Microplastics are a global ecological concern due to their potential risk to wildlife and human health. Animals ingest microplastics, which can enter the trophic chain and ultimately impact human well-being. The ingestion of microplastics can cause physical and chemical damage to the animals' digestive systems, affecting their health. To estimate the risk to ecosystems and human health, it is crucial to understand the accumulation and localization of ingested microplastics within the cells and tissues of living organisms. However, analyzing this issue is challenging due to the risk of sample contamination, given the ubiquity of microplastics. Here, an analytical approach is employed to confirm the internalization of microplastics in cryogenic cross-sections of mussel tissue. Using 3D Raman confocal microscopy in combination with chemometrics, microplastics measuring 1 μm in size were detected. The results were further validated using optical and fluorescence microscopy. The findings revealed evidence of microplastics being internalized in the digestive epithelial tissues of exposed mussels (Mytilus galloprovincialis), specifically within the digestive cells forming digestive alveoli. This study highlights the need to investigate the internalization of microplastics in organisms like mussels, as it helps us understand the potential risks they pose to aquatic biota and ultimately to human health. By employing advanced imaging techniques, challenges associated with sample contamination can be overcome and valuable insights into the impact of microplastics on marine ecosystems and human consumers are provided.

Elucidating the effects of naturally weathered aged-polypropylene microplastics and newly procured polypropylene microplastics on raw 264.7 macrophages

In this work, we investigated weathered aged-PPMPs and naturally obtained polypropylene microplastics (NP-PPMPs) with raw 264.7 macrophages, which causes cytotoxicity and an imbalance in the intracellular system.

Marine plastic pollution: fishers' coping strategies and its welfare effect in Volta region, Ghana

The issue of marine plastic pollution has drawn significant attention from around the world due to the harm it poses to marine and coastal ecosystems. Despite this, the scholarly literature has not been able to fully explore the coping strategies adopted by fishers and their welfare effects. Motivated by this argument, this study examines the determinants of the coping strategies employed in response to marine plastic pollution, and its effect on fishers' productivity in the Volta region, Ghana. Empirically, the multinomial endogenous switching regression (MESR) model established that the drivers of the coping strategies adopted were age, knowledge, marital status, fishers' experience in fishing, and household size. Fishers that adopted purse net only, drift-gill net only, both purse and drift-gill nets and all the three fishing techniques (purse, drag and drift-gill) have a greater productivity compared to the non-adopters. Policy implications are proposed.

Recent progress of microplastic toxicity on human exposure base on in vitro and in vivo studies

Microplastics are widely distributed in the environment, including the atmosphere, soil and water bodies. They have been found to have toxic effects on organisms. The impact on human health is also receiving considerable attention. Microplastics can be found in drinking water, food, air and plastic products, and they can enter human body through the pathways such as ingestion, inhalation, and skin contact. After exposure to microplastics, they can induce cellular toxicity and produce toxic effects on multiple organs and systems, including the digestive, respiratory, nervous, reproductive and cardiovascular systems. This paper presents a comprehensive review and analysis on the recent progress of human exposure studies, in vitro experiments, rodent experiments, and other model experiments in microplastic human toxicity research. It comprehensively analyzes the potential human toxic effects of microplastics, providing a theoretical basis for further research on microplastic human toxicity and its mechanisms. Furthermore, this paper highlights the knowledge gaps and provides the recommendations for future research on human toxicity of microplastics.

Decadal Assessment of Microplastics, Pharmaceuticals, and Pesticides as Contaminants of Emerging Concern in Kenya's Surface Waters: A Review

Studies investigating microplastics, pharmaceuticals, and pesticides as contaminants of emerging concern (CECs) in surface water sources in Kenya are reviewed. Contaminants of emerging concern are chemicals that have recently been discovered that may pose a threat to the environment, aquatic life, and human life. Microplastics in surface waters range from 1.56 to as high as 4520 particles/m3 , with high concentrations recorded in coastal waters. The dominant microplastics are fibers, fragments, and films, with foams, granules, and pellets making up only a small percentage. The main source of pharmaceuticals in water sources is not wastewater-treatment plants but rather raw untreated sewage because high concentrations are found near informal settlements with poor sewage connectivity. Antibiotics are detected in the range of the limit of quantification to 320 μg/L, with sulfamethoxazole, trimethoprim, and ciprofloxacin being the most abundant antibiotics. The high frequency of detection is attributed to the general misuse of antibiotics in the country. A health risk assessment indicated that only ciprofloxacin and acetaminophen posed noncarcinogenic health risks in the Ndarugo River and Mombasa periurban creeks, respectively. Similarly, the detection of antiretroviral drugs, mainly lamivudine, nevirapine, and zidovudine, is associated with human immunodeficiency virus prevalence in Kenya. In the Lake Naivasha, Nairobi River, and Lake Victoria basins, frequently detected organochloride pesticides (OCPs) are methoxychlor, alachlor, endrin, dieldrin, endosulfan, endosulfan sulfate, α-hexachlorocyclohexane (α-HCH), γ-HCH, and dichlorodiphenyltrichloroethane (DDT), some of which occur above permissible concentrations. The presence of DDT in some sites translates to illegal use or historical application. The majority of individual OCPs posed no noncarcinogenic health risk, except dieldrin and aldrin which had a hazard quotient >1 in two sites. Therefore, more surveying and regular monitoring in different regions in Kenya concerning CECs is essential to determine the spatial variability and effective measures to be taken to reduce pollution. Environ Toxicol Chem 2023;42:2105-2118. © 2023 SETAC.

Early screening of suspected microplastics in bottled water in the Santiago Metropolitan Region of Chile

Bottled water has emerged as a possible healthier alternative due to concerns about the quality of drinking water sources. However, recent studies have detected worrying concentrations of environmental contaminants in bottled water, including microplastics. Therefore, it is an emerging need to quantify their concentrations in local suppliers which could differ among countries and regions. In this work, we used fluorescence microscopy with Nile Red for the identification and quantification of potential microplastics in twelve brands of bottled water distributed in the Santiago Metropolitan Region of Chile. The average concentration of microplastics was 391 ± 125 p L-1, while the highest concentration observed was 633 ± 33 p L-1. Microplastics between 5 and 20 μm were the major contributors, a size fraction that has been reported to be susceptible to accumulate in the digestive tract or generate potential alterations in the lymphatic and circulatory systems. The estimated daily intake value for per capita was estimated to be 229 p kg-1 year-1 for people weighing 65 kg and 198 p kg-1 year-1 for those weighing 75 kg.

Effects of Micro(nano)plastics on the reproductive system: A review

Microplastics (100nm-5 mm) and nanoplastics (1-100 nm) are collectively referred to as micro(nano)plastics (MNPs), which are refractory to degradation, easy to migration, small in size, strong in adsorption, and can widely present in human living environment. A number of studies have confirmed that MNPs can be exposed to the human body through a variety of routes, and can penetrate various barriers to enter the reproductive system, suggesting that MNPs may pose potential harm to human reproductive health. Current studies most were limited to phenotypic studies and their subjects were basically lower marine organisms and mammals. Therefore, in order to provide theoretical base for further exploring the effects of MNPs on the human reproductive system, this paper searched the relevant literature at home and abroad, mainly analyzed rodent experiments, and concluded that the main exposure routes of MNPs are dietary intake, air inhalation, skin contact and medical plastics. After entering the reproductive system, MNPs produce reproductive toxicity mainly through oxidative stress, inflammation, metabolic disorders, cytotoxicity and other mechanisms. More work is required to comprehensively identify the exposure routes, improve the detection methods to evaluate the effective exposure and deeply study the specific mechanisms of toxic effects, withing the aim of conducting relevant studies at the population level in the next step.

A critical review on recent research progress on microplastic pollutants in drinking water

Plastic pollution is an emerging issue in recent days. Persistent plastic particles reach the atmosphere, land and water by multiple pathways. Research has confirmed that the existence of plastic particles is found surprisingly everywhere, from the Artic to the Antarctic region. The probability of ingestion of plastic by all living forms is quite natural, as the whole planet's environment is polluted with microplastic particles. The bioaccumulation of microplastics is a threat and the consequences for living beings are yet to be explored. Microplastics present in different drinking water sources like rivers, lakes, treatment units etc. are studied by several researchers, covering various aspects. Research carried out by various scientists on the microplastics in different drinking water sources is highlighted in this review. In view of the previous research carried out on various aspects of microplastic particles, the necessity of a uniform protocol for qualitative and quantitative analysis of microplastic is ascertained. Microplastic pollution is an ongoing environmental concern, it must be addressed and research should be expanded.

Discussion about suitable applications for biodegradable plastics regarding their sources, uses and end of life

This opinion paper offers a scientific view on the current debate of the place of biodegradable plastics as part of the solution to deal with the growing plastic pollution in the world's soil, aquatic, and marine compartments. Based on the current scientific literature, we focus on the current limits to prove plastic biodegradability and to assess the toxicity of commercially used biobased and biodegradable plastics in natural environments. We also discuss the relevance of biodegradable plastics for selected applications with respect to their use and end of life. In particular, we underlined that there is no universal biodegradability of plastics in any ecosystem, that considering the environment as a waste treatment system is not acceptable, and that the use of compostable plastics requires adaptation of existing organic waste collection and treatment channels.

Quantification of polyethylene terephthalate micro- and nanoplastics in domestic wastewater using a simple three-step method

Concerns about impact of small plastic particles, known as microplastics (<5 mm) and nanoplastics (<1 μm), together abbreviated as MNP, on the environment and on human health have increased in recent years. Polyethylene terephthalate (PET) microplastics have been detected previously in different environmental samples including freshwater and wastewater sludge. In the present study, we target all small plastic particles of PET with a diameter smaller than 5 mm ('PET MNP'). A simple three-step method of drying, (in matrix) PET depolymerization in ethylene glycol and liquid chromatography-mass spectrometry (LC-MS) analysis, was applied for the quantification of PET MNP in influents and effluents collected from ten Dutch wastewater treatment plants. The PET recovery was 98 % in the wastewater matrix. The limits of detection (LOD) for PET in influents and effluents were 2.0 μg/L and 1.2 μg/L, respectively. PET MNP was detected in all the influents (ranging from 24.9 μg/L to 680 μg/L) and most of the effluents (ranging from <LOD to 23.1 μg/L). The results of the present study confirmed that WWTP effluents can be a source of PET MNP in the environment.

Additives in polypropylene and polylactic acid food packaging: Chemical analysis and bioassays provide complementary tools for risk assessment

Plastic food packaging represents 40 % of the plastic production worldwide and belongs to the 10 most commonly found items in aquatic environments. They are characterized by high additives contents with >4000 formulations available on the market. Thus they can release their constitutive chemicals (i.e. additives) into the surrounding environment, contributing to chemical pollution in aquatic systems and to contamination of marine organism up to the point of questioning the health of the consumer. In this context, the chemical and toxicological profiles of two types of polypropylene (PP) and polylactic acid (PLA) food packaging were investigated, using in vitro bioassays and target gas chromatography mass spectrometry analyses. Plastic additives quantification was performed both on the raw materials, and on the material leachates after 5 days of lixiviation in filtered natural seawater. The results showed that all samples (raw materials and leachates) contained additive compounds (e.g. phthalates plasticizers, phosphorous flame retardants, antioxidants and UV-stabilizers). Differences in the number and concentration of additives between polymers and suppliers were also pointed out, indicating that the chemical signature cannot be generalized to a polymer and is rather product dependent. Nevertheless, no significant toxic effects was observed upon exposure to the leachates in two short-term bioassays targeting baseline toxicity (Microtox® test) and Pacific oyster Crassostrea gigas fertilization success and embryo-larval development. Overall, this study demonstrates that both petrochemical and bio-based food containers contain harmful additives and that it is not possible to predict material toxicity solely based on chemical analysis. Additionally, it highlights the complexity to assess and comprehend the additive content of plastic packaging due to the variability of their composition, suggesting that more transparency in polymer formulations is required to properly address the risk associated with such materials during their use and end of life.

Antioxidant Defense in Primary Murine Lung Cells following Short- and Long-Term Exposure to Plastic Particles

Polystyrene nano- and micro-sized plastic particles (NMP) are one of the common plastic materials produced that dramatically pollute the environment, water, and oceanic habitats worldwide. NMP are continuously absorbed by the body through a number of routes, especially via intestinal ingestion, dermal uptake, and inhalation into the lung. Several studies provided evidence of NMP provoking oxidative stress and affecting cellular responses. Yet, the NMP effects on primary lung cells have not been studied. To this end, we isolated and cultured murine lung cells and exposed them short-term or long-term to polystyrene 0.2-6.0 µm-sized NMP. We studied cellular consequences regarding oxidative stress, morphology, and secretion profiling. Visualization, distribution, and expression analyses confirmed lung cells accumulating NMP and showed several significant correlations with particle size. Moreover, we found substantial evidence of biological consequences of small-scale NMP uptake in lung cells. Besides alterations of cytokine secretion profiles resulting in inflammatory responses, indicators of oxidative stress were identified that were accompanied by Nrf2 and β-catenin signaling changes. Our results serve as an important basis to point out the potential hazards of plastic contaminations and uptake in lung cells.

Short- and long-term polystyrene nano- and microplastic exposure promotes oxidative stress and divergently affects skin cell architecture and Wnt/beta-catenin signaling

Nano- and microplastic particles (NMP) are strong environmental contaminants affecting marine ecosystems and human health. The negligible use of biodegradable plastics and the lack of knowledge about plastic uptake, accumulation, and functional consequences led us to investigate the short- and long-term effects in freshly isolated skin cells from mice. Using fluorescent NMP of several sizes (200 nm to 6 µm), efficient cellular uptake was observed, causing, however, only minor acute toxicity as metabolic activity and apoptosis data suggested, albeit changes in intracellular reactive species and thiol levels were observed. The internalized NMP induced an altered expression of various targets of the nuclear factor-2-related transcription factor 2 pathway and were accompanied by changed antioxidant and oxidative stress signaling responses, as suggested by altered heme oxygenase 1 and glutathione peroxide 2 levels. A highly increased beta-catenin expression under acute but not chronic NMP exposure was concomitant with a strong translocation from membrane to the nucleus and subsequent transcription activation of Wnt signaling target genes after both single-dose and chronic long-term NMP exposure. Moreover, fibroblast-to-myofibroblast transdifferentiation accompanied by an increase of α smooth muscle actin and collagen expression was observed. Together with several NMP-induced changes in junctional and adherence protein expression, our study for the first time elucidates the acute and chronic effects of NMP of different sizes in primary skin cells' signaling and functional biology, contributing to a better understanding of nano- and microplastic to health risks in higher vertebrates.

Comprehensive in vitro polymer type, concentration, and size correlation analysis to microplastic toxicity and inflammation

The ubiquitous nature of microplastic particles (MP) is a growing environmental and ecological concern due to their impact on aquatic and terrestrial systems and potentially on human health. The potential impact on human health may be due to MP daily exposure by several routes, but little is known about the cellular effects. Previous in vitro and in vivo studies have described inflammation, oxidative stress, and metabolic disruption upon plastic exposure, while the effect of individual plastic parameters is not fully unraveled. To this end, we investigated plastic exposure to different polymer types, sizes, and concentrations in three human cell lines (A549, HEK293, and HeLa). Particles were polystyrene (PS) or polymethylmethacrylate (PMMA) in three sizes and concentrations, and amine-modified PS served as positive control. After MP size validation using dynamic light scattering, a high-throughput high-content imaging-based and algorithm-driven multi-z-stack analysis was established to quantify intracellular fluorescent particle accumulation in 3D objects and cell maximum intensity projections. MP uptake correlated with concentration and for PS with size (1.040 μm), while for PMMA it was maximal for 400 nm MP. Uptake increased in HEK cells independent of MP parameters. Except for positive controls, no major effect on metabolic activity, viability, and cell cycle was observed, while intracellular thiol content and cytokine secretion were affected to a considerable extent. Interestingly, particle uptake was correlated significantly with particle size and concentration, underlining the dependence of MP parameters on biological effects.

Enhanced coagulation process for removing dissolved organic matter, microplastics, and silver nanoparticles

Dissolved organic carbon (DOC), microplastics (MPs), and silver nanoparticles (AgNPs) in water are of major concern because of their direct and indirect toxic effects on aquatic organisms and human exposure via water. This work investigated the effect of poly aluminum chloride (PACl) coagulation for reducing DOC, MPs, and AgNPs. This work used water from a canal in Thailand with a DOC of 5.2 mg/L in the experiment. AgNPs of 5-20 mg/L were added to canal water to create synthetic water for the PACl coagulation. Polyethylene and polypropylene (PP) type MPs were identified in the raw water with Fourier transform infrared spectroscopy. Coagulation with 15 mg/L of PACl performed better in the PP removal. The PACl coagulation at dosages of 15, 40, and 70 mg/L removed DOC by 16-20%, 44-52%, and 46-63% and AgNPs by 34-90%, 53-93%, and 81-95%, respectively. The presence of AgNPs at high levels could inhibit the efficiency of DOC reduction by the PACl coagulation. The FESEM identified the adsorption of silver-containing nanoparticles onto the flocs with increased dosages of PACl. So, PACl is a coagulant in the removal of AgNPs that can reduce health hazards and eco-toxicological risks in water sources due to the release of silver.

Prospect of microplastic pollution control under the "New normal" concept beyond COVID-19 pandemic

Coronavirus disease (COVID-19) has led to increasing demand for single-use plastic which aggravates the already existing plastic waste problem. Not only does the demand for personal protective equipment (PPE) increase, but also people shift their preference to online shopping and food delivery to comply with administrative policies for COVID-19 pandemic control. The used PPEs, packaging materials, and food containers may not be handled or recycled properly after their disposal. As a result, the mismanaged plastic waste is discharged into the environment and it may pose even greater risks after breaking into smaller fragments, which was regarded as the source of secondary microplastics (MPs, < 5 mm) or nanoplastics (NPs, < 1 μm). The main objective of this manuscript is to provide a review of the studies related to microplastic release due to pandemic-associated plastic waste. This study summarizes the limited work published on the ecotoxicological/toxicological effect of MPs/NPs released from PPE on aquatic organisms, soil organisms, as well as humans. Given the current status of research on MPs from COVID-related plastic waste, the immediate research directions needed on this topic were discussed.

Microplastic profusion in food and drinking water: are microplastics becoming a macroproblem?

Microplastics are extremely complex, and as the food chain comes full circle, it is dreaded that these could have a deleterious influence on humans. Although the risk of plastics to humans is not yet established, their occurrence in food and water destined for human consumption has been reported. The prevalence of micro-sized plastics in the ecosystem and living organisms, their trophic transfer along the food web, and the discernment of food species as competent indicators have become research priorities. The scale of the issue is massive, but what are the main culprits and causes, and could there be a solution in sight for this global problem? Despite the massive amount of research in the field, a collation of available data and pertinent hazard evaluation remains difficult. In order to identify the knowledge gaps and exposure pathways, several traits related to food chain assessment are presented with the goal of properly evaluating and managing this emerging risk. We apprehend three possible noxious consequences of small plastic particles, firstly, due to the plastic particles themselves; secondly, due to the extrication of tenacious organic pollutants adsorbed onto the plastics; and thirdly, due to the leaching of components such as monomers and additives from the plastics. The exigency for the standardization of protocols to bring about consistency in data collection and analysis, involving solutions, stakeholder costs, and benefits, are discussed. Harmonized methods will enable meticulous assessment of the impacts and threats that microplastics pose to the biota and increase the comparability between studies. We emphasize the contribution of the "honest broker" in science, providing an overarching analysis to devise the most viable solutions to microplastic pollution for private and public leadership to utilize.

A scoping review protocol on in vivo human plastic exposure and health impacts

BACKGROUND

Global plastic production has increased exponentially since the 1960s, with more than 6300 million metric tons of plastic waste generated to date. Studies have found a range of human health outcomes associated with exposure to plastic chemicals. However, only a fraction of plastic chemicals used have been studied in vivo, and then often in animals, for acute toxicological effects. With many questions still unanswered about how long-term exposure to plastic impacts human health, there is an urgent need to map human in vivo research conducted to date, casting a broad net by searching terms for a comprehensive suite of plastic chemical exposures and the widest range of health domains.

METHODS

This protocol describes a scoping review that will follow the recommended framework outlined in the 2017 Guidance for the Conduct of Joanna Briggs Institute (JBI) Scoping Reviews, to be reported in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) Checklist. A literature search of primary clinical studies in English from 1960 onwards will be conducted in MEDLINE (Ovid) and EMBASE (Ovid) databases. References eligible for inclusion will be identified through a quality-controlled, multi-level screening process. Extracted data will be presented in diagrammatic and tabular form, with a narrative summary addressing the review questions.

DISCUSSION

This scoping review will comprehensively map the primary research undertaken to date on plastic exposure and human health. Secondary outputs will include extensive databases on plastic chemicals and human health outcomes/impacts.

SYSTEMATIC REVIEW REGISTRATION

Open Science Framework (OSF)-Standard Pre-Data Collection Registration, https://archive.org/details/osf-registrations-gbxps-v1 , https://doi.org/10.17605/OSF.IO/GBXPS.

Monitoring microplastics in drinking water: An interlaboratory study to inform effective methods for quantifying and characterizing microplastics

California Senate Bill 1422 requires the development of State-approved standardized methods for quantifying and characterizing microplastics in drinking water. Accordingly, we led an interlaboratory microplastic method evaluation study, with 22 participating laboratories from six countries, to evaluate the performance of widely used methods: sample extraction via filtering/sieving, optical microscopy, FTIR spectroscopy, and Raman spectroscopy. Three spiked samples of simulated clean water and a laboratory blank were sent to each laboratory with a prescribed standard operating procedure for particle extraction, quantification, and characterization. The samples contained known amounts of microparticles within four size fractions (1-20 μm, 20-212 μm, 212-500 μm, >500 μm), four polymer types (PE, PS, PVC, and PET), and six colors (clear, white, green, blue, red, and orange). They also included false positives (natural hair, fibers, and shells) that may be mistaken for microplastics. Among laboratories, mean particle recovery using stereomicroscopy was 76% ± 10% (SE). For particles in the three largest size fractions, mean recovery was 92% ± 12% SD. On average, laboratory contamination from blank samples was 91 particles (± 141 SD). FTIR and Raman spectroscopy accurately identified microplastics by polymer type for 95% and 91% of particles analyzed, respectively. Per particle, FTIR spectroscopy required the longest time for analysis (12 min ± 9 SD). Participants demonstrated excellent recovery and chemical identification for particles greater than 50 μm in size, with opportunity for increased accuracy and precision through training and further method refinement. This work has informed methods and QA/QC for microplastics monitoring in drinking water in the State of California.

The polymers and their additives in particulate plastics: What makes them hazardous to the fauna?

Due to the increasing concerns on global ecosystems and human health, the environmental risks posed by microplastics (MPs) and nanoplastics (NPs) have become an important topic of research. Their ecological impacts on various faunal species have been extensively researched and reviewed. However, the majority of those studies perceive these micro(nano)-plastics (MNPs) as a single entity rather than a collective term for a group of chemically distinct polymeric particulates. Each of the plastic polymers can possess unique physical and chemical behavior, which, in turn, can determine the possible environmental impacts. Furthermore, many studies explore the adsorption, absorption, and release of other environmental pollutants by MNPs. But only a handful of them explore the leaching of additives possessed by these polymers. Data on the environmental behavior and toxicity of individual additives associated with different polymer particulates are scarce. Knowledge about the leachability and ecotoxicity of the additives associated with environmental MNPs (unlike large plastic particles) remains limited. The ecological impacts of different MNPs together with their additives and the basis of their toxicity have not been explored yet. The present review systematically explores the potential implications of environmentally predominant polymers and their associated additives and discusses their physicochemical characteristics. The review ultimately aims to provide novel insights on what components precisely make MNPs hazardous to the fauna. The paper also discusses the major challenges proposed in the available literature along with recommendations for future research to throw light on possible solutions to overcome the hazards of MNPs.

Scientific Evidence about the Risks of Micro and Nanoplastics (MNPLs) to Human Health and Their Exposure Routes through the Environment

Nowadays, a large amount and variety of plastic is being produced and consumed by human beings on an enormous scale. Microplastics and nanoplastics (MNPLs) have become ubiquitous since they can be found in many ecosystem components. Plastic particles can be found in soil, water, and air. The routes of human exposure are numerous, mainly involving ingestion and inhalation. Once ingested, these particles interact with the gastrointestinal tract and digestive fluids. They can adsorb substances such as additives, heavy metals, proteins, or even microorganisms on their surface, which can cause toxicity. During inhalation, they can be inhaled according to their respective sizes. Studies have reported that exposure to MNPLs can cause damage to the respiratory tract, creating problems such as bronchitis, asthma, fibrosis, and pneumothorax. The reports of boards and committees indicate that there is little data published and available on the toxicity of MNPLs as well as the exposure levels in humans. Despite the well-established concept of MNPLs, their characteristics, and presence in the environment, little is known about their real effects on human health and the environment.

Discovery and quantification of plastic particle pollution in human blood

Plastic particles are ubiquitous pollutants in the living environment and food chain but no study to date has reported on the internal exposure of plastic particles in human blood. This study's goal was to develop a robust and sensitive sampling and analytical method with double shot pyrolysis - gas chromatography/mass spectrometry and apply it to measure plastic particles ≥700 nm in human whole blood from 22 healthy volunteers. Four high production volume polymers applied in plastic were identified and quantified for the first time in blood. Polyethylene terephthalate, polyethylene and polymers of styrene (a sum parameter of polystyrene, expanded polystyrene, acetonitrile butadiene styrene etc.) were the most widely encountered, followed by poly(methyl methacrylate). Polypropylene was analysed but values were under the limits of quantification. In this study of a small set of donors, the mean of the sum quantifiable concentration of plastic particles in blood was 1.6 µg/ml, showing a first measurement of the mass concentration of the polymeric component of plastic in human blood. This pioneering human biomonitoring study demonstrated that plastic particles are bioavailable for uptake into the human bloodstream. An understanding of the exposure of these substances in humans and the associated hazard of such exposure is needed to determine whether or not plastic particle exposure is a public health risk.

Occurrence of Microplastics in Tap and Bottled Water: Current Knowledge

A narrative review was carried out to describe the current knowledge related to the occurrence of MPs in drinking water. The reviewed studies (n = 21) showed the presence of microplastics (MPs) in tap (TW) and bottled (BW) water, increasing concerns for public health due to the possible toxicity associated with their polymeric composition, additives, and other compounds or microorganism adsorbed on their surface. The MP concentration increase by decreasing particles size and was higher in BW than in TW. Among BW, reusable PET and glass bottles showed a higher MP contamination than other packages. The lower MP abundance in TW than in natural sources indicates a high removal rate of MPs in drinking water treatment plants. This evidence should encourage the consumers to drink TW instead of BW, in order to limit their exposure to MPS and produce less plastic waste. The high variability in the results makes it difficult to compare the findings of different studies and build up a general hypothesis on human health risk. A globally shared protocol is needed to harmonize results also in view of the monitoring plans for the emerging contaminants, including MPs, introduced by the new European regulation.

Consequences of nano and microplastic exposure in rodent models: the known and unknown

The ubiquitous nature of micro- (MP) and nanoplastics (NP) is a growing environmental concern. However, their potential impact on human health remains unknown. Research increasingly focused on using rodent models to understand the effects of exposure to individual plastic polymers. In vivo data showed critical exposure effects depending on particle size, polymer, shape, charge, concentration, and exposure routes. Those effects included local inflammation, oxidative stress, and metabolic disruption, leading to gastrointestinal toxicity, hepatotoxicity, reproduction disorders, and neurotoxic effects. This review distillates the current knowledge regarding rodent models exposed to MP and NP with different experimental designs assessing biodistribution, bioaccumulation, and biological responses. Rodents exposed to MP and NP showed particle accumulation in several tissues. Critical responses included local inflammation and oxidative stress, leading to microbiota dysbiosis, metabolic, hepatic, and reproductive disorders, and diseases exacerbation. Most studies used MP and NP commercially provided and doses higher than found in environmental exposure. Hence, standardized sampling techniques and improved characterization of environmental MP and NP are needed and may help in toxicity assessments of relevant particle mixtures, filling knowledge gaps in the literature.

Plastic Debris As a Vector for Bacterial Disease: An Interdisciplinary Systematic Review

Pathogens and polymers can separately cause disease; however, environmental and medical researchers are increasingly investigating the capacity of polymers to transfer pathogenic bacteria, and cause disease, to hosts in new environments. We integrated causal frameworks from ecology and epidemiology into one interdisciplinary framework with four stages (colonization, survival, transfer, disease). We then systematically and critically reviewed 111 environmental and medical papers. We show 58% of studies investigated the colonization-stage alone but used this as evidence to classify a substratum as a vector. Only 11% of studies identified potential pathogens, with only 3% of studies confirming the presence of virulence-genes. Further, 8% of studies investigated μm-sized polymers with most (58%) examining less pervasive cm-sized polymers. No study showed bacteria can preferentially colonize, survive, transfer, and cause more disease on polymers compared to other environmental media. One laboratory experiment demonstrated plausibility for polymers to be colonized by a potential pathogen (Escherichia coli), survive, transfer, and cause disease in coral (Astrangia poculata). Our analysis shows a need for linked structured surveys with environmentally relevant experiments to understand patterns and processes across the vectoral stages, so that the risks and impacts of pathogens on polymers can be assessed with more certainty.

Towards Risk Assessments of Microplastics in Bivalve Mollusks Globally

The ubiquitous presence of microplastics in bivalve mollusks and related risks have raised particular concerns. In this study, the available data on the abundance and polymer type of microplastics in bivalves from twenty-two countries were extracted to comprehensively understand the risks of microplastics in bivalves. Following the data from 52 peer-reviewed papers, the abundance, chemical composition, and human exposure risks of microplastics of bivalves among countries were initially assessed. Abundance risk results indicated that bivalves from 22 countries presented a low pollution load index, showing a lower risk level (level I). The polymer risk index (H) of bivalves from Portugal (Hcountry = 1335, level IV) and India (Hcountry = 1187, level IV) were higher than the other countries due to the occurrence of hazardous microplastics, such as polyvinyl chloride. For the human exposure risks, the global mean value of microplastic exposure to humans via mollusk consumption is estimated to be 751 microplastics/capita/year, with the maximum intake by the Chinese. This study suggests that abundance risk may be a fundamental indicator for assessing the potential hazard to humans until the chemical composition risks are confirmed. This study is the first attempt to assess the potential risks of microplastics in bivalves using three evaluation models based on microplastic abundances and polymer types, which will contribute to establishing future human health risk assessment frameworks. These findings will also assist efforts in policy-making to minimize microplastic risks in seafood.

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.

Weathering of geotextiles under ultraviolet exposure: A neglected source of microfibers from coastal reclamation

Geotextiles are a group of polymeric materials widely used in coastal reclamation projects. However, long-term exposure to solar illumination deteriorates the performance of geotextiles, resulting in physicochemical changes and high risks of releasing microfibers. This study investigated the photoaging behavior of geotextiles and evaluated the capacity of geotextiles to release microfibers in coastal reclamation areas through a combination of field research and laboratory experiments. A field survey in the coastal reclamation area of Yancheng (China) confirmed that many geotextiles made from polyethylene terephthalate (PET) existed on the beach, which was accompanied by a high value of carbonyl index of 0.70-0.93. The results from laboratory experiments revealed that ultraviolet exposure activated the photooxidative process and promoted the breakdown of PET geotextiles. Data of scanning electron microscope and laser particle analyzer showed that, initially, particles with the size of less than 1 μm were generated on the surface of geotextiles, followed by fragments with sizes of 1-100 μm falling off with the passage of time. The number of particles on the surface was calculated using Image-Pro Plus software and the maximum particle density was found to be around 2.52 million particles·mm^-2. In addition, based upon the conversion of irradiance between the simulated solar and natural solar, it was roughly estimated that the annual emissions of PET geotextile fibers in coastal reclamation areas were 0.24-0.79 million tons all over the world. It is inferred that polymer-made geotextile is a significant source of microplastic pollution in reclamation zones of coastal areas.

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.

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.

Microplastics in Wastewater and Drinking Water Treatment Plants: Occurrence and Removal of Microfibres

Microplastics (MPs), and specifically microfibres (MPFs), are ubiquitous in water bodies, including wastewater and drinking water. In this work, a thorough literature review on the occurrence and removal of MPs, and specifically MPFs in WWTPs and DWTPs, has been carried out. When the water is treated, an average microfiber removal efficiency over 70% is achieved in WWTPs and DWTPs. These high percentages are still inefficient for avoiding the presence of a large number of microfibres in treated wastewater and also in tap water. RSF, DAF, oxidation ditch and CAS processes have been described as the most efficient treatments for eliminating MPFs from wastewater treatment. It is remarkable the wide range of the data reported on this topic; for example, treated wastewater contains between not detected and 347 MPFs/L, whereas tap water contains between not detected and 168 MPFs/L. Microfibres constitute more than half of the MPs found in treated wastewater and sewage sludge, whereas in DWTP effluents the percentage of MPFs is around 32%. Nevertheless, the relative amount of MPFs reported in tap water is notably higher (71%). Microfibres from WWTPs are discharged to the environment, being a source of MP pollution. Additionally, MPs released by DWTPs directly enter the drinking water lines, which constitute a direct route for MP human consumption, so that it has been estimated that an adult may ingest an average value of 7500 MPFs per year only via tap water. Thus, this review provides an update on the performance of WWTPs and DWTPs in removing MPs from water, which is an issue of great interest.

Microplastics in terrestrial ecosystems: Moving beyond the state of the art to minimize the risk of ecological surprise

Microplastic (plastic particles measuring <5mm) pollution is ubiquitous. Unlike in other well-studied ecosystems, for example, marine and freshwater environments, microplastics in terrestrial systems are relatively understudied. Their potential impacts on terrestrial environments, in particular the risk of causing ecological surprise, must be better understood and quantified. Ecological surprise occurs when ecosystem behavior deviates radically from expectations and generally has negative consequences for ecosystem services. The properties and behavior of microplastics within terrestrial environments may increase their likelihood of causing ecological surprises as they (a) are highly persistent global pollutants that will last for centuries, (b) can interact with the abiotic environment in a complex manner, (c) can impact terrestrial organisms directly or indirectly and (d) interact with other contaminants and can facilitate their transport. Here, we compiled findings of previous research on microplastics in terrestrial environments. We systematically focused on studies addressing different facets of microplastics related to their distribution, dispersion, impact on soil characteristics and functions, levels of biological organization of tested terrestrial biota (single species vs. assemblages), scale of experimental study and corresponding ecotoxicological effects. Our systematic assessment of previous microplastic research revealed that most studies have been conducted on single species under laboratory conditions with short-term exposures; few studies were conducted under more realistic long-term field conditions and/or with multi-species assemblages. Studies targeting multi-species assemblages primarily considered soil bacterial communities and showed that microplastics can alter essential nutrient cycling functions. More ecologically meaningful studies of terrestrial microplastics encompassing multi-species assemblages, critical ecological processes (e.g., biogeochemical cycles and pollination) and interactions with other anthropogenic stressors must be conducted. Addressing these knowledge gaps will provide a better understanding of microplastics as emerging global stressors and should lower the risk of ecological surprise in terrestrial ecosystems.

Adoption and diffusion of marine litter clean-up technologies across European seas: Legal, institutional and financial drivers and barriers

This study reviews existing legal, institutional and policy tools and frameworks, relevant to the introduction and adoption of new marine litter clean-up technologies in two regional European seas, the Mediterranean and the Baltic. A combination of desk studies in six countries bordering the Baltic (Estonia, Germany, Sweden) and the Mediterranean (Greece, Italy, Tunisia), and interviews with experts and stakeholders, is used to identify key drivers and barriers to the adoption and diffusion of marine litter technologies. The main conclusion of the study is that the most influential pieces of legislation relevant to marine litter management are top-down EU policies, often forming the basis of regional and national plans. Moreover, the study finds that several drivers of marine litter technologies may at the same time be critical barriers. These factors include public awareness, consumer behaviour, enforcement of legislation, and the rise of SMEs engaged in recycling and eco-labelling of marine litter.

Placing nanoplastics in the context of global plastic pollution

Numerous studies have made the ubiquitous presence of plastic in the environment undeniable, and thus it no longer comes as a surprise when scientists measure the accumulation of macroplastic litter and microplastic fragments in both urban and remote sites. Nanoplastics have recently emerged in the discussions of scientists, regulators and the public, as the weathering of macroplastics may lead to a substantial burden of nanoplastics in various ecosystems. While nanoplastics particles themselves have not (yet) been extensively measured in the environment, there is increased concern that this size fraction of plastic may be more extensively distributed and hazardous that larger-sized particles. This assessment may emanate from an unease with the term 'nano', which may elicit a negative response over uncertainties of the pervasiveness of nanoplastics specifically, or from the lessons learned by many years of intensive environmental health and safety research of engineered nanomaterials. Ultimately, the different physical and chemical characteristics of the different size classes of plastic pollution (macroplastics, microplastics and nanoplastics) will result in divergent fate and hazards. As nanoscientists specializing in understanding the fate, transport and interactions of nanoparticles in human and environmental systems, in this Perspective, we try to place nanoplastics in the context of global plastic pollution by assessing its sources and risks, and by assessing commonalities nanoplastics may share with other nanosized objects in environmental systems, such as engineered nanomaterials and natural colloids.