Microplastics and nanoplastics in the atmosphere: the potential impacts on cloud formation processes

A review on advancements in atmospheric microplastics research: The pivotal role of machine learning

Microplastics (MPs), recognized as emerging pollutants, pose significant potential impacts on the environment and human health. The investigation into atmospheric MPs is nascent due to the absence of effective characterization methods, leaving their concentration, distribution, sources, and impacts on human health largely undefined with evidence still emerging. This review compiles the latest literature on the sources, distribution, environmental behaviors, and toxicological effects of atmospheric MPs. It delves into the methodologies for source identification, distribution patterns, and the contemporary approaches to assess the toxicological effects of atmospheric MPs. Significantly, this review emphasizes the role of Machine Learning (ML) and Artificial Intelligence (AI) technologies as novel and promising tools in enhancing the precision and depth of research into atmospheric MPs, including but not limited to the spatiotemporal dynamics, source apportionment, and potential health impacts of atmospheric MPs. The integration of these advanced technologies facilitates a more nuanced understanding of MPs' behavior and effects, marking a pivotal advancement in the field. This review aims to deliver an in-depth view of atmospheric MPs, enhancing knowledge and awareness of their environmental and human health impacts. It calls upon scholars to focus on the research of atmospheric MPs based on new technologies of ML and AI, improving the database as well as offering fresh perspectives on this critical issue.

Nanoplastics in Water: Artificial Intelligence-Assisted 4D Physicochemical Characterization and Rapid In Situ Detection

For the first time, we present a much-needed technology for the in situ and real-time detection of nanoplastics in aquatic systems. We show an artificial intelligence-assisted nanodigital in-line holographic microscopy (AI-assisted nano-DIHM) that automatically classifies nano- and microplastics simultaneously from nonplastic particles within milliseconds in stationary and dynamic natural waters, without sample preparation. AI-assisted nano-DIHM identifies 2 and 1% of waterborne particles as nano/microplastics in Lake Ontario and the Saint Lawrence River, respectively. Nano-DIHM provides physicochemical properties of single particles or clusters of nano/microplastics, including size, shape, optical phase, perimeter, surface area, roughness, and edge gradient. It distinguishes nano/microplastics from mixtures of organics, inorganics, biological particles, and coated heterogeneous clusters. This technology allows 4D tracking and 3D structural and spatial study of waterborne nano/microplastics. Independent transmission electron microscopy, mass spectrometry, and nanoparticle tracking analysis validates nano-DIHM data. Complementary modeling demonstrates nano- and microplastics have significantly distinct distribution patterns in water, which affect their transport and fate, rendering nano-DIHM a powerful tool for accurate nano/microplastic life-cycle analysis and hotspot remediation.

Clothing Textiles as Carriers of Biological Ice Nucleation Active Particles

Microplastics have littered the globe, with synthetic fibers being the largest source of atmospheric microplastics. Many atmospheric particles can act as ice nucleators, thereby affecting the microphysical and radiative properties of clouds and, hence, the radiative balance of the Earth. The present study focused on the ice-nucleating ability of fibers from clothing textiles (CTs), which are commonly shed from the normal wear of apparel items. Results from immersion ice nucleation experiments showed that CTs were effective ice nucleators active from -6 to -12 °C, similar to common biological ice nucleators. However, subsequent lysozyme and hydrogen peroxide digestion stripped the ice nucleation properties of CTs, indicating that ice nucleation was biological in origin. Microscopy confirmed the presence of biofilms (i.e., microbial cells attached to a surface and enclosed in an extracellular polysaccharide matrix) on CTs. If present in sufficient quantities in the atmosphere, biological particles (biofilms) attached to fibrous materials could contribute significantly to atmospheric ice nucleation.

Characteristics and quantification of small microplastics (<100 µm) in seasonal svalbard snow on glaciers and lands

Small microplastics (SMPs < 100 µm) can easily be transported over long distances far from their sources through the atmospheric pathways and reach even remote regions, including the Arctic. However, these sizes of MPs are mostly overlooked due to different analytical challenges; besides, their pathways through atmospheric depositions, such as snow depositions, are mostly unknown. The spatial variability in bulk snow samples was investigated for the first time in distinct sites (e.g., glaciers) near Ny Ålesund, the world-known northernmost permanent research settlement in the Svalbard Islands, to better comprehend the presence of SMP pollution in snow. Seasonal snow deposited over the tundra and the summits of different glaciers were also sampled. A sampling procedure was designed to obtain representative samples while minimizing plastic contamination, thanks to rigorous quality assurance and quality control protocol. SMPs' weight (µg SMP L-1) and deposition load (mg SMPs m-2) result from being lower in the remote glaciers, where they may be subject to long-range transport. The SMPs' minimum length was 20 µm, with the majority less than 100 µm. Regarding their size distribution, there was an increase in the size length deriving from the local input of the human presence near the scientific settlement. The presence of some polymers might be site-specific in relation to the pathways that affect their distribution at the sites studied. Also, from the snow surface layer collected at the same sites to evaluate the variability of SMPs during specific atmospheric deposition events, the results confirmed their higher weight and load in surface snow near the scientific settlement compared to the glaciers. The results will enhance the limited knowledge of the SMPs in polar atmospheric compartments and deposition processes.

Plastics in the environment in the context of UV radiation, climate change and the Montreal Protocol: UNEP Environmental Effects Assessment Panel, Update 2023

This Assessment Update by the Environmental Effects Assessment Panel (EEAP) of the United Nations Environment Programme (UNEP) considers the interactive effects of solar UV radiation, global warming, and other weathering factors on plastics. The Assessment illustrates the significance of solar UV radiation in decreasing the durability of plastic materials, degradation of plastic debris, formation of micro- and nanoplastic particles and accompanying leaching of potential toxic compounds. Micro- and nanoplastics have been found in all ecosystems, the atmosphere, and in humans. While the potential biological risks are not yet well-established, the widespread and increasing occurrence of plastic pollution is reason for continuing research and monitoring. Plastic debris persists after its intended life in soils, water bodies and the atmosphere as well as in living organisms. To counteract accumulation of plastics in the environment, the lifetime of novel plastics or plastic alternatives should better match the functional life of products, with eventual breakdown releasing harmless substances to the environment.

Quantification and Characterization of Fine Plastic Particles as Considerable Components in Atmospheric Fine Particles

The negative effects of air pollution, especially fine particulate matter (PM2.5, particles with an aerodynamic diameter of ≤2.5 μm), on human health, climate, and ecosystems are causing significant concern. Nevertheless, little is known about the contributions of emerging pollutants such as plastic particles to PM2.5 due to the lack of continuous measurements and characterization methods for atmospheric plastic particles. Here, we investigated the levels of fine plastic particles (FPPs) in PM2.5 collected in urban Shanghai at a 2 h resolution by using a novel versatile aerosol concentration enrichment system that concentrates ambient aerosols up to 10-fold. The FPPs were analyzed offline using the combination of spectroscopic and microscopic techniques that distinguished FPPs from other carbon-containing particles. The average FPP concentrations of 5.6 μg/m3 were observed, and the ratio of FPPs to PM2.5 was 13.2% in this study. The FPP sources were closely related to anthropogenic activities, which pose a potential threat to ecosystems and human health. Given the dramatic increase in plastic production over the past 70 years, this study calls for better quantification and control of FPP pollution in the atmosphere.

Potential synergy of microplastics and nitrogen enrichment on plant holobionts in wetland ecosystems

Wetland ecosystems are global hotspots for environmental contaminants, including microplastics (MPs) and nutrients such as nitrogen (N) and phosphorus (P). While MP and nutrient effects on host plants and their associated microbial communities at the individual level have been studied, their synergistic effects on a plant holobiont (i.e., a plant host plus its microbiota, such as bacteria and fungi) in wetland ecosystems are nearly unknown. As an ecological entity, plant holobionts play pivotal roles in biological nitrogen fixation, promote plant resilience and defense chemistry against pathogens, and enhance biogeochemical processes. We summarize evidence based on recent literature to elaborate on the potential synergy of MPs and nutrient enrichment on plant holobionts in wetland ecosystems. We provide a conceptual framework to explain the interplay of MPs, nutrients, and plant holobionts and discuss major pathways of MPs and nutrients into the wetland milieu. Moreover, we highlight the ecological consequences of loss of plant holobionts in wetland ecosystems and conclude with recommendations for pending questions that warrant urgent research. We found that nutrient enrichment promotes the recruitment of MPs-degraded microorganisms and accelerates microbially mediated degradation of MPs, modifying their distribution and toxicity impacts on plant holobionts in wetland ecosystems. Moreover, a loss of wetland plant holobionts via long-term MP-nutrient interactions may likely exacerbate the disruption of wetland ecosystems' capacity to offer nature-based solutions for climate change mitigation through soil organic C sequestration. In conclusion, MP and nutrient enrichment interactions represent a severe ecological risk that can disorganize plant holobionts and their taxonomic roles, leading to dysbiosis (i.e., the disintegration of a stable plant microbiome) and diminishing wetland ecosystems' integrity and multifunctionality.

Micro- and nano-plastics in the atmosphere: A review of occurrence, properties and human health risks

The ubiquitous occurrence of micro/nano plastics (MNPs) poses potential threats to ecosystem and human health that have attracted broad concerns in recent decades. Detection of MNPs in several remote regions has implicated atmospheric transport as an important pathway for global dissemination of MNPs and hence as a global health risk. In this review, the latest research progress on (1) sampling and detection; (2) origin and characteristics; and (3) transport and fate of atmospheric MNPs was summarized. Further, the current status of exposure risks and toxicological effects from inhaled atmospheric MNPs on human health is examined. Due to limitations in sampling and identification methodologies, the study of atmospheric nanoplastics is very limited today. The large spatial variation of atmospheric MNP concentrations reported worldwide makes it difficult to compare the overall indoor and outdoor exposure risks. Several in vitro, in vivo, and epidemiological studies demonstrate adverse effects of immune response, apoptosis and oxidative stress caused by MNP inhalation that may induce cardiovascular diseases and reproductive and developmental abnormalities. Given the emerging importance of atmospheric MNPs, the establishment of standardized sampling-pretreatment-detection protocols and comprehensive toxicological studies are critical to advance environmental and health risk assessments of atmospheric MNPs.

Comparative study on physicochemical characteristics of atmospheric microplastics in winter in inland and coastal megacities: A case of Beijing and Shanghai, China

Atmospheric microplastics (MPs) have received global attention across various sectors of society due to their potential negative impacts. This study aims to understand the physicochemical characteristics of MPs in inland and coastal megacities for raising awareness about the urgent need to reduce plastic pollution. Laser Direct Infrared Imaging (LDIR) and Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray Spectroscopy (EDX) techniques were employed to characterize atmospheric MPs in megacities (inland megacity Beijing and coastal megacity Shanghai) in China, focusing on their physicochemical characteristics, including compositional types, number concentration, morphology, size, possible sources, and potential health risks. The LDIR analysis identified sixteen different types of MPs present in the atmospheres of Beijing and Shanghai. The number concentration of atmospheric MPs in Beijing (3.0 items/m3) is 1.8 times that of Shanghai (1.7 items/m3). The study found that the variations in MP pollution between Beijing and Shanghai are influenced by the urban industrial structure and geographical location. Morphological analysis indicates that fragment MPs have the highest relative abundance in Beijing, while fibrous MPs dominate the atmosphere of Shanghai. Additionally, the study assessed the potential health risks of atmospheric MPs to urban residents. The results suggest that residents of Beijing face more severe health risks from atmospheric MPs compared to those in Shanghai. These findings underscore the urgency to address the issue of atmospheric MPs and provide crucial evidence for the formulation of relevant environmental and health policies.

Emerging isolation and degradation technology of microplastics and nanoplastics in the environment

Microplastics (MPs, less than 5 mm in size) are widely distributed in surroundings in various forms and ways, and threaten ecosystems security and human health. Its environmental behavior as pollutants carrier and the after-effects exposed to MPs has been extensively exploited; whereas, current knowledge on technologies for the separation and degradation of MPs is relatively limited. It is essential to isolate MPs from surroundings and/or degrade to safe levels. This in-depth review details the origin and distribution of MPs. Provides a comprehensive summary of currently available MPs separation and degradation technologies, and discusses the mechanisms, challenges, and application prospects of these technologies. Comparison of the contribution of various separation methods to the separation of NPs and MPs. Furthermore, the latest research trends and direction in bio-degradation technology are outlooked.

Underappreciated microplastic galaxy biases the filter-based quantification

Long-term environmental loading of microplastics (MPs) causes alarming exposure risks for a variety of species worldwide, considered a planetary threat to the well-being of ecosystems. Robust quantitative estimates of MP extents and featured diversity are the basis for comprehending their environmental implications precisely, and of these methods, membrane-based characterizations predominate with respect to MP inspections. However, though crucial to filter-based MP quantification, aggregation statuses of retained MPs on these substrates remain poorly understood, leaving us a "blind box" that exaggerates uncertainty in quantitive strategies of preselected areas without knowing overview loading structure. To clarify this uncertainty and estimate their impacts on MP counting, using MP imaging data assembled from peer-reviewed studies through a systematic review, here we analyze the particle-specific profiles of MPs retained on various substrates according to their centre of mass with a fast-random forests algorithm. We visualize the formation of distinct galaxy-like MP aggregation-similar to the solar system and Milky Way System comprised of countless stars-across the pristine and environmental samples by leveraging two spatial parameters developed in this study. This unique pattern greatly challenges the homogeneously or randomly distributed MP presumption adopted extensively for simplified membrane-based quantification purposes and selective ROI (region of interest) estimates for smaller-sized plastics down to the nano-range, as well as the compatibility theory using pristine MPs as the standard to quantify the presence of environmental MPs. Furthermore, our evaluation with exemplified numeration cases confirms these location-specific and area-dependent biases in many imaging analyses of a selective filter area, ascribed to the minimum possibility of reaching an ideal turnover point for the selective quantitive strategies. Consequently, disproportionate MP schemes on loading substrates yield great uncertainty in their quantification processing, highlighting the prompt need to include pattern-resolved calibration prior to quantification. Our findings substantially advance our understanding of the structure, behavior, and formation of these MP aggregating statuses on filtering substrates, addressing a fundamental question puzzling scientists as to why reproducible MP quantification is barely achievable even for subsamples. This study inspires the following studies to reconsider the impacts of aggregating patterns on the effective counting protocols and target-specific removal of retained MP aggregates through membrane separation techniques.

Toxicity Mechanisms of Nanoplastics on Crop Growth, Interference of Phyllosphere Microbes, and Evidence for Foliar Penetration and Translocation

Despite the increasing prevalence of atmospheric nanoplastics (NPs), there remains limited research on their phytotoxicity, foliar absorption, and translocation in plants. In this study, we aimed to fill this knowledge gap by investigating the physiological effects of tomato leaves exposed to differently charged NPs and foliar absorption and translocation of NPs. We found that positively charged NPs caused more pronounced physiological effects, including growth inhibition, increased antioxidant enzyme activity, and altered gene expression and metabolite composition and even significantly changed the structure and composition of the phyllosphere microbial community. Also, differently charged NPs exhibited differential foliar absorption and translocation, with the positively charged NPs penetrating more into the leaves and dispersing uniformly within the mesophyll cells. Additionally, NPs absorbed by the leaves were able to translocate to the roots. These findings provide important insights into the interactions between atmospheric NPs and crop plants and demonstrate that NPs' accumulation in crops could negatively impact agricultural production and food safety.

Atmospheric microplastic deposition in a coastal city of India: The influence of a landfill source on monsoon winds

Coastal zones experience various wind events that may influence the characteristics, distribution, and dynamics of atmospheric microplastic pollutants. In the present study, we investigated the characteristics of the bulk atmospheric microplastic deposition in Kochi, Kerala, India, during three distinct seasons: Northeast Monsoon (NEM), Summer (SMR), and Southwest monsoon (SWM). Seasonally, the highest microplastic fallout rate was recorded for the NEM (37.29 particles m-2d-1), followed by SMR (15.17 particles m-2 d-1) and the SWM (11.57 particles m-2d-1). The microplastic abundance was not correlated to the amount of rainfall. Further, the wind rose and HYSPLIT trajectory analysis illustrated the arrival of northeast monsoon winds to the city via the region in and around the municipal landfill, which could be a major source of airborne microplastic to the sampling stations, and the forward trajectories from the landfill site extended into the Arabia Sea, providing evidence on the potential atmospheric transport and subsequent deposition of microplastics into the ocean. With respect to the qualitative characteristics, blue-coloured and fibrous microplastics dominated the samples with a considerable number of particles belonging to the size range of 200-500 μm. The practice of drying synthetic clothes under natural sunlight may have substantially contributed to the increased prevalence of airborne microfibers. The higher numbers of polyethylene (PE) and polypropylene (PP) in the bulk microplastic deposition reinforce the concept of low-density polymers being more susceptible to deflation by the wind. Overall, the work signifies the role of monsoon winds in transporting microplastics from an unscientifically managed municipal landfill site and also highlights the importance of reducing the quantity of plastic waste ending up at the landfill to reduce the emission of microplastics proportionately.

Shape Matters: Long-Range Transport of Microplastic Fibers in the Atmosphere

The deposition of airborne microplastic particles, including those exceeding 1000 μm in the longest dimension, has been observed in the most remote places on earth. However, their deposition patterns are difficult to reproduce using current atmospheric transport models. These models usually treat particles as perfect spheres, whereas the real shapes of microplastic particles are often far from spherical. Such particles experience lower settling velocities compared to volume equivalent spheres, leading to longer atmospheric transport. Here, we present novel laboratory experiments on the gravitational settling of microplastic fibers in air and find that their settling velocities are reduced by up to 76% compared to those of the spheres of the same volume. An atmospheric transport model constrained with the experimental data shows that shape-corrected settling velocities significantly increase the horizontal and vertical transport of particles. Our model results show that microplastic fibers of about 1 mm length emitted in populated areas are more likely to reach extremely remote regions of the globe, including the high Arctic, which is not the case for spheres of equivalent volume. We also calculate that fibers with lengths of up to 100 μm settle slowly enough to be lifted high into the stratosphere, where degradation by ultraviolet radiation may release chlorine and bromine, thus potentially damaging the stratospheric ozone layer. These findings suggest that the growing environmental burden and still increasing emissions of plastic pose multiple threats to life on earth.

Suspended and deposited microplastics in the coastal atmosphere of southwest England

Atmospheric microplastics (MPs) have been sampled from coastal southwest England during twelve periods over a 42-day timeframe in late autumn. MPs were dominated by fibres, with foams, fragments and pellets also observed. The majority of fibres were identified as the semisynthetic polymer, rayon, while other shapes were dominated by various petroleum-based thermoplastics (including polyvinyl acetate, polyvinyl alcohol, polyamide and polyester) and paints. MP concentrations suspended in air ranged from 0.016 to 0.238 items per m3 but displayed no clear dependence on wind speed or direction. Total depositional fluxes ranged from 0.47 to 3.30 m-2 h-1 and showed no clear dependence on wind conditions or electrical conductivity of precipitation (as a measure of maritime influence). However, the concentration of deposited MPs in rainwater was inversely related to rainfall volume, suggesting that incipient precipitation acts to efficiently washout microplastics. A comparison of deposited and suspended MPs by size, shape and polymer type suggests that larger fibres constructed of rayon, polyamide and acrylic are preferentially removed from the atmosphere relative to smaller, non-fibrous MPs and particles constructed of polyester. A quantitative comparison of deposited and suspended MPs provided estimates of location- and environment-specific net settling velocities of between about 7 and 180 m h-1 and corresponding residence times for an air column of 5000 m of between about 30 and 700 h. The findings of the study contribute to an improved understanding of the occurrence, transport and deposition of MPs in the atmosphere more generally.

Long-range atmospheric transport of microplastics across the southern hemisphere

Airborne microplastics (MPs) can undergo long range transport to remote regions. Yet there is a large knowledge gap regarding the occurrence and burden of MPs in the marine boundary layer, which hampers comprehensive modelling of their global atmospheric transport. In particular, the transport efficiency of MPs with different sizes and morphologies remains uncertain. Here we show a hemispheric-scale analysis of airborne MPs along a cruise path from the mid-Northern Hemisphere to Antarctica. We present the inaugural measurements of MPs concentrations over the Southern Ocean and interior Antarctica and find that MPs fibers are transported more efficiently than MPs fragments along the transect, with the transport dynamics of MPs generally similar to those of non-plastic particles. Morphology is found to be the dominant factor influencing the hemispheric transport of MPs to remote Antarctic regions. This study underlines the importance of long-range atmospheric transport in MPs cycling dynamics in the environment.

Chemical characterization of microplastic particles formed in airborne waste discharged from sewer pipe repairs

Microplastic particles are of increasing environmental concern due to the widespread uncontrolled degradation of various commercial products made of plastic and their associated waste disposal. Recently, common technology used to repair sewer pipes was reported as one of the emission sources of airborne microplastics in urban areas. This research presents results of the multi-modal comprehensive chemical characterization of the microplastic particles related to waste discharged in the pipe repair process and compares particle composition with the components of uncured resin and cured plastic composite used in the process. Analysis of these materials employs complementary use of surface-enhanced Raman spectroscopy, scanning transmission X-ray spectro-microscopy, single particle mass spectrometry, and direct analysis in real-time high-resolution mass spectrometry. It is shown that the composition of the relatively large (100 μm) microplastic particles resembles components of plastic material used in the process. In contrast, the composition of the smaller (micrometer and sub-micrometer) particles is significantly different, suggesting their formation from unintended polymerization of water-soluble components occurring in drying droplets of the air-discharged waste. In addition, resin material type influences the composition of released microplastic particles. Results are further discussed to guide the detection and advanced characterization of airborne microplastics in future field and laboratory studies pertaining to sewer pipe repair technology.

Impacts of Micro(nano)plastics on Terrestrial Plants: Germination, Growth, and Litter

Micro(nano)plastics (MNP) are pervasive in various environmental media and pose a global environmental pollution issue, particularly in terrestrial ecosystems, where they exert a significant impact on plant growth and development. This paper builds upon prior research to analyze and consolidate the effects of MNP on soil properties, seed germination, plant growth, and litter decomposition. The objective is to elucidate the environmental behavior of MNP and their mechanisms of influence on the plant life cycle. The unique physicochemical and electrical properties of MNP enable them to modify soil structure, water retention capacity, and pH. They can potentially act as "electron shuttles" or disrupt natural "electron shuttles" in litter decomposition, thereby interfering with nutrient transport and availability in the soil. Furthermore, MNP can physically obstruct nutrient and water channels within plants, impacting nutrient and water absorption. Once infiltrating plant tissues, MNP can form eco-coronas with plant proteins. Together with MNP adsorbed on the plant's surface and within its tissues, they disrupt normal physiological processes, leading to changes in photosynthesis, biomass, cellular toxicity, genetics, nutrient uptake, and gene expression. These changes, in turn, influence seed germination and plant growth and development. As a burgeoning research field, future studies should delve deeper into various aspects of these changes, such as elucidating the pathways and mechanisms through which MNP enter plant tissues, assessing their intensity and mechanisms of toxicity on different plant species, and exploring the relationship between micro(nano)plastics and "electron shuttles". These endeavors will contribute to establishing a more comprehensive theoretical framework for understanding the environmental behavior of MNP and their impact on plants.

Microplastics in snow from protected areas in Hokkaido, the northern island of Japan

Snowfall is regarded as a carrier of airborne microplastics (MPs). Deposited snow can function as a temporary reservoir for atmospheric MPs. Nevertheless, knowledge and understanding of MPs in snow remain sparse. This study investigates the abundance, composition, size (> 30 µm), and shape of MPs in snow specimens from various nature preservation areas and also from urban sites in Hokkaido. Various polymeric-type MPs with mostly fragmentary shapes were detected among the specimens. More than half of MPs were in the smallest size class (30-60 µm), implying the presence of more MPs below the limit (< 30 µm). Concentrations of MPs ranged from 1.5 × 10² to 4.2 × 10³ particles/L. The results demonstrated that microplastic abundance generally decreases concomitantly with increasing remoteness of sampling sites. Observed features of MPs at different locations and their relation to geographical settings have indicated that the ubiquitously observed fine particles (mainly alkyd, ethylene-vinyl acetate, and polyethylene) are attributable to long-distance atmospheric transportation, whereas the rubber and larger particles especially found near highways and cities are from local sources of plastic. Taken together, these findings suggest important implications for elucidating the nature and distribution of atmospheric MPs.

Microplastics in snow of a high mountain national park: El Teide, Tenerife (Canary Islands, Spain)

Human activities have introduced high amounts of microplastics (MPs) into the atmosphere that can be transported long distances and be later deposited in terrestrial and aquatic ecosystems with precipitation (rain or snow). In this work, it has been assessed the presence of MPs in the snow of El Teide National Park (Tenerife, Canary Islands, Spain, 2150-3200 m above sea level) after two storm episodes (January-February 2021). The data set (63 samples) was divided into three groups: i) samples from "accessible areas" (after the first storm episode and in places with a strong previous/recent anthropogenic activity); ii) "pristine areas" (after the second storm episode, in places with no previous anthropogenic activity), and iii) "climbing areas" (after the second storm episode, in places with a soft recent anthropogenic activity). Similar pattern profiles were observed among sampling sites in terms of morphology, colour and size (predominance of blue and black microfibers of 250-750 μm length), as well as in composition (predominance of cellulosic -either natural or semisynthetic-, with a 62.7 %, polyester, 20.9 %, and acrylic, 6.3 %, microfibers); however, significant differences in MPs concentrations were found between samples collected in pristine areas (average concentration of 51 ± 72 items/L) and those obtained in places with a previous anthropogenic activity (average concentration of 167 ± 104 and 188 ± 164 items/L in "accessible areas" and "climbing areas", respectively). This study shows, for the first time, the presence of MPs in snow samples from a high altitude protected area on an insular territory and suggests that the sources of these contaminants could be atmospheric transport and local human outdoor activities.

Potential effects of micro- and nanoplastics on phyllosphere microorganisms and their evolutionary and ecological responses

Plastic pollution is among the most urgent environmental and social challenges of the 21st century, and their influxes in the environment have altered critical growth drivers in all biomes, attracting global concerns. In particular, the consequences of microplastics on plants and their associated soil microorganisms have gained a large audience. On the contrary, how microplastics and nanoplastics (M/NPs) may influence the plant-associated microorganisms in the phyllosphere (i.e., the aboveground portion of plants) is nearly unknown. We, therefore, summarize evidence that may potentially connect M/NPs, plants, and phyllosphere microorganisms based on studies on other analogous contaminants such as heavy metals, pesticides, and nanoparticles. We show seven pathways that may link M/NPs into the phyllosphere environment, and provide a conceptual framework explaining the direct and indirect (soil legacy) effects of M/NPs on phyllosphere microbial communities. We also discuss the adaptive evolutionary and ecological responses, such as acquiring novel resistance genes via horizontal gene transfer and microbial degradation of plastics of the phyllosphere microbial communities, to M/NPs-induced threats. Finally, we highlight the global consequences (e.g., disruption of ecosystem biogeochemical cycling and impaired host-pathogen defense chemistry that can lead to reduced agricultural productivity) of altered plant-microbiome interactions in the phyllosphere in the context of a predicted surge of plastic production and conclude with pending questions for future research priorities. In conclusion, M/NPs are very likely to produce significant effects on phyllosphere microorganisms and mediate their evolutionary and ecological responses.

Heterogeneous Nucleation of Supersaturated Water Vapor onto Sub-10 nm Nanoplastic Particles

Nanoplastic pollution by atmospheric transport processes is a recently discovered environmental problem on a global scale that is attributed to the dispersion of aerosolized nanoplastics. However, knowledge about the basic physicochemical properties of aerosol nanoplastic particles is scarce. Here, we present experiments on the heterogeneous nucleation of supersaturated water vapor onto sub-10 nm polyethylene terephthalate (PET) seeds. We determined onset saturation ratios for the activation of PET seeds in comparison to the well-documented reference system of silver particles, resulting in lower onset saturation ratios of the PET seeds compared to silver seeds. By using different PET bulk materials for the generation of nanoparticles, we report a strong material dependence of the onset saturation ratios, pointing to a strong effect of additives from commodity plastics in heterogeneous nucleation. Moreover, our results show a strong dependence on nucleation temperature that might be of immediate atmospheric relevance. Our work can be considered as an initial step in airborne nanoplastic detection by condensation techniques, and we anticipate our study to serve as a basis for further research that will eventually allow assessing the impact of nanoplastic dispersion on atmospheric processes.

Assessing and managing environmental hazards of polymers: historical development, science advances and policy options

Polymers are the main constituents of many materials and products in our modern world. However, their environmental safety is not assessed with the same level of detail as done for non-polymeric chemical substances. Moreover, the fundamentals of contemporary regulatory approaches for polymers were developed in the early 1990s, with little change occurring since then. Currently, the European Commission is working on a proposal to initiate registration of polymers under the European Union's (EU) chemicals legislation REACH. This provides a unique opportunity for regulation to catch up on recent scientific advances. To inform this process, we here critically appraise the suggested regulatory approaches to the environmental assessment and management of polymers against the latest scientific findings regarding their environmental fate, exposure, and effects, and identify the remaining critical knowledge gaps. While we use the EU draft proposal as an example, our findings are broadly applicable to other polymer legislations worldwide, due to the similarity of polymer assessment criteria being used. We emphasize four major aspects that require more attention in the regulation of polymers: (i) increased transparency about chemical identities, physical characteristics and grouping approaches for in-use polymers; (ii) improved understanding of the environmental fate of polymers and materials composed of polymers across size and density categories and exposure profiles; (iii) comprehensive assessment of the environmental hazards of polymers, considering the effects of degradation and weathering and taking into account the actual uptake, long-term toxicity, and geophysical impacts; and (iv) consideration of the production volume and use/release patterns in determining regulatory data and testing requirements. Transitioning toward a toxic-free and sustainable circular economy will likely require additional policy instruments that will reduce the overall complexity and diversity of in-use polymers and polymeric materials.