Atmospheric Microplastics Research Articles

Evidence of free tropospheric and long-range transport of microplastic at Pic du Midi Observatory

The emerging threat of atmospheric microplastic pollution has prompted researchers to study areas previously considered beyond the reach of plastic. Investigating the range of atmospheric microplastic transport is key to understanding the global extent of this problem. While atmospheric microplastics have been discovered in the planetary boundary layer, their occurrence in the free troposphere is relatively unexplored. Confronting this is important because their presence in the free troposphere would facilitate transport over greater distances and thus the potential to reach more distal and remote parts of the planet. Here we show evidence of 0.09–0.66 microplastics particles/m3 over 4 summer months from the Pic du Midi Observatory at 2877 meters above sea level. These results exhibit true free tropospheric transport of microplastic, and high altitude microplastic particles <50 µm (aerodynamic diameter). Analysis of air/particle history modelling shows intercontinental and trans-oceanic transport of microplastics illustrating the potential for global aerosol microplastic transport.

The indoor exposure of microplastics in different environments

The atmospheric microplastics (MPs) in indoor environment have attracted great attention in recent years. In the study, we selected five indoor study cases with students of different as the research objects, including kindergartens, primary schools, middle schools, high schools and university. The atmospheric MPs fallouts were continuously collected in the different study rooms. Simultaneously, the morphological characteristics and composition of MPs were also investigated. The level of MPs pollution greatly varied due to different characteristics of indoor environments. The highest and lowest abundance of MPs appeared in senior high school and kindergarten classroom, respectively. Fibers were the main form of MPs, since fibers were easily detached from the textile products. Besides, the abundance of MPs was significantly related to indoor population density and duration of human activity. This study provides the first evidence of atmospheric MPs in different study rooms, which could be helpful for understanding environmental behavior of MPs and providing further information to assess potential risks of exposure to indoor airborne MPs.

Modeling microplastics’ climate impact

Microplastics are abundant in the world’s waterways and even in the air. In fact, researchers estimate there are hundreds to thousands of microplastic particles in each cubic meter of air in urban environments. University of Canterbury environmental physicist Laura Revell wondered how atmospheric microplastics might impact the climate. After all, she says, “other types of particulates in the atmosphere, such as dust, soot, and sulfate aerosols, influence the climate by absorbing and scattering sunlight.” To determine whether atmospheric microplastics are warming or cooling the planet, Revell’s group analyzed their optical properties, finding that the types of particles assumed to be abundant scatter ultraviolet and visible light but absorb infrared radiation. The researchers plugged those data, along with estimates of these particles’ abundance, into a global climate simulation ( Nature 2021, DOI: 10.1038/s41586-021-03864-x ). The climate impact of microplastics depends on what altitudes they reach—something researchers don’t yet know, Revell says.

Characteristics, Toxic Effects, and Analytical Methods of Microplastics in the Atmosphere.

Microplastics (MPs) (including nanoplastics (NPs)) are pieces of plastic smaller than 5 mm in size. They are produced by the crushing and decomposition of large waste plastics and widely distributed in all kinds of ecological environments and even in organisms, so they have been paid much attention by the public and scientific community. Previously, several studies have reviewed the sources, occurrence, distribution, and toxicity of MPs in water and soil. By comparison, the review of atmospheric MPs is inadequate. In particular, there are still significant gaps in the quantitative analysis of MPs and the mechanisms associated with the toxic effects of inhaled MPs. Thus, this review summarizes and analyzes the distribution, source, and fate of atmospheric MPs and related influencing factors. The potential toxic effects of atmospheric MPs on animals and humans are also reviewed in depth. In addition, the common sampling and analysis methods used in existing studies are introduced. The aim of this paper is to put forward some feasible suggestions on the research direction of atmospheric MPs in the future.

Enhanced impacts evaluation of Typhoon Sinlaku (2020) on atmospheric microplastics in South China Sea during the East Asian Summer Monsoon

Atmospheric transport is an important pathway through which microplastics (MPs) are widely exchanged between marine and terrestrial environments. However, the impacts of frequent extreme weather events, such as typhoons, on atmospheric MPs is poorly understood. To address this issue, we collected suspended atmospheric MPs (SAMPs) and rainfall samples in the South China Sea during Typhoon Sinlaku (2020). Our results revealed a higher abundance of suspended MPs (1.05 ± 0.55 n/100 m3) during the typhoon than in the pre-typhoon period (0.59 ± 0.48 n/100 m3). Nine polymer types were identified by micro-FTIR, among which the dominant were polyethylene terephthalate (PET, 62.82%) and polypropylene (PP, 19.23%). Moreover, rainfall appeared more inclined to remove larger sizes, more colors and more polymer types of MPs from the atmosphere. The trajectory source-receptor plot indicated that the typhoon significantly changed the pathway of MP transport in the atmosphere, including the direction and distance. To our knowledge, this is the first study to elucidate the impact of typhoons on atmospheric MP transportation. Our results indicate that airborne MPs may pose unexpected ecological risks to marine and coastal ecosystems due to their increased abundance from more distant sources, resulting from typhoon events.

The Pollution of Atmospheric Microplastics and Their Potential Risks to Humans

As an emerging environmental pollutant, microplastics have widely existed in the global environment. Not like water and soils, the cognition of airbone microplastics is limited. Studies have shown that fiber is the main form of airbone microplastics. For humans, due to the small size of microplastics, microplastics in the atmosphere are easily brought into the human respiratory system through breathing, posing potential risks to human health. This article reviews the characteristics of microplastics in the atmosphere, the transmission routes, and the potential hazards to humans. The characteristics and sources of atmospheric microplastics are investigated, and the airborne transmission path and deposition rules of atmospheric microplastics are summarized. Future research should focuse on on small-size atmospheric microplastics, which are smaller in size and more biologically toxic. The abundance of atmospheric microplastics need to be expressed in a global unified standard manner to increase feasibility in comparison of research works. Future research should explore the effects of plastics on the composition, structure and functions of terrestrial biota.

Airborne microplastics in indoor and outdoor environments of a coastal city in Eastern China

Microplastics (MPs) in marine and terrestrial environments have been intensively studied, but the dynamics of airborne MPs remains limited. Existing studies on atmospheric MPs are mostly derived from collection of atmospheric deposition, whereas direct measurements of airborne MPs are scarce. However, the abundance of airborne MPs is more relevant for evaluating human inhalation exposure risk. Herein, airborne MPs in indoor and outdoor environments from urban and rural areas of a coastal city in eastern China were investigated. MP concentrations (mean±SD) in indoor air (1583 ± 1180 n/m3) were an order of magnitude higher than outdoor air (189 ± 85 n/m3), and airborne MP concentrations in urban areas (224 ± 70 n/m3) were higher than rural areas (101 ± 47 n/m3). MPs smaller than 100 µm dominated airborne MPs, and the predominant shape of airborne MPs was fragments, as opposed to fibers. The larger MP size fractions contained a higher proportion of fibers, whereas the smaller size fractions were nearly exclusively composed of fragments. The health risk caused by ubiquitous airborne MPs should not be discounted as the maximum annual outdoor exposure of airborne MPs can reach 1 million/year, while indoor exposure may be even higher due to higher indoor airborne MP concentrations.

Plastic dust in the wind

Microplastics Plastic pollution is ubiquitous throughout the environment, the endmember being microplastics generated from the breakdown of larger, more primary pieces. Brahney et al. investigated the sources of atmospheric microplastics using a combination of observations and atmospheric transport models. They found that the majority of microplastics in the air are derived from the fragmentation of plastics on roadways, with much smaller fractions coming from oceans and agricultural soils. This finding underscores the importance of controlling primary plastic pollution. Proc. Natl. Acad. Sci. U.S.A. 118 , e2020719118 (2021).

The abundance and characteristics of atmospheric microplastic deposition in the northwestern South China Sea in the fall

Atmospheric microplastics have been widely reported and detected in remote mountain areas and oceans, indicating that they can be transported over long distances through the atmosphere. Regional transport and deposition processes of atmospheric microplastics have a significant impact on the source and sink patterns, as well as the flux mechanisms of microplastics in terrestrial and marine environments. However, few studies have been conducted on the deposition of atmospheric microplastics. Thus, in this study, we collected atmospheric microplastic samples from the northwestern South China Sea and estimated that in the fall the dry deposition of atmospheric microplastics into the ocean was 1.4 × 103 t, which had a greater contribution than riverine inputs of microplastics in this region, suggesting that atmospheric microplastics are non-negligible sources of marine plastic litter with high environmental risk. Additionally, we reported on the abundance (0.035 ± 0.015 n/m3), morphological characteristics, composition, and sources of atmospheric microplastics in the northwestern South China Sea. Smaller-sized microplastics had a high abundance that decreased with increased proximity from the coast. Most of the detected microplastics were fibers, which accounted for approximately two-thirds of the total quantity. The spectral analysis detected seven polymer types, and polyester was predominant (29%). Combined with the cluster analysis of the backward trajectories of airflow, we demonstrated that the airflow affecting the northwestern South China Sea originated mainly from the northeast, potentially carrying microplastics from cities located in southeastern Chinese provinces to the South China Sea.

Efficient transport of atmospheric microplastics onto the continent via the East Asian summer monsoon

The presence of microplastics (MPs) in the atmosphere is a global concern because of its environmental and health impacts; however, the monsoonal transport of atmospheric MPs has not yet been investigated. To fully understand the effect of the monsoon on atmospheric MP transport, we conducted a study along the southeast coast of China during the East Asian summer monsoon (EASM). We found that the EASM transports atmospheric MPs back onto the continent at a flux of up to 212.977–213.433 kg/EASM/year. The backward trajectory and wind field results indicate that the EASM provides an effective MP transport pathway from Vietnam, the Philippines, and Malaysia to southeastern China. This suggests that only some of the airborne MPs over the ocean enter the marine ecosystem. The average abundance of atmospheric MPs over the sampling area was 0.39 items/100 m3 (0.39 ± 0.43 items/100 m3) during the EASM season, with high variability among the sampling sites. This study improves our understanding of the impact of the EASM on atmospheric MP transport, which can help quantify the contributions of atmospheric MPs to marine or terrestrial ecosystems.

Atmospheric deposition of microplastics in the coastal zone: Characteristics and relationship with meteorological factors

In this study, the quantitative and qualitative compositions of microplastics (MPs) deposited from the atmosphere in the coastal zone were analysed. Moreover, links between MP deposition and meteorological factors (air humidity, wind speed, precipitation height, and air mass trajectories) were investigated. MP deposition samples were collected in the southern Baltic area in 2017 and 2018 for 286 days in total. The morphological features of MPs (shape and size) were analysed using a digital microscope. Qualitative analysis was performed using micro-attenuated total reflectance Fourier-transform infrared spectroscopy (μATR FT-IR). The size of the deposited MPs ranged from 5 μm to 5000 μm, and smaller size classes (<720 μm) were predominant (70%). Fibres were of the dominant type (60%). Films and fragments constituted 26% and 14% of the total MPs, respectively, while 55% of the MPs found in the study were polymers often used in textiles, packaging materials, and fishing gear (polyesters and polypropylene). The atmospheric MP deposition ranged from 0 m−2·d−1 to 30 m−2·d−1 (average: 10 ± 8 m−2·d−1; median: 8 m−2·d−1). Based on the air mass trajectory cluster analysis, MPs deposited in Gdynia mainly originated from local sources (<100 km). Furthermore, higher MP deposition occurred when the inflowing air masses were terrestrial, and lower deposition occurred when they were marine. On average, during wet periods twice the amount of MPs was deposited in comparison with dry periods. During dry periods deposition increased with increasing wind speed and was intensified by high relative humidity.

Microplastics as emerging atmospheric pollutants: a review and bibliometric analysis

Microplastics are ubiquitously present in various environments; thus, they have become a noteworthy issue by researchers. The present study aimed to provide state-of-the-art on microplastic studies and in detail to review the researches on atmospheric microplastic pollution in terms of occurrence, distribution, sampling, analysis, sources, and transport. The results of the bibliometric analysis showed that the annual output in microplastic research has increased, especially during the last 5 years. The research hot spots in the microplastic topic are marine environment, surface water, freshwater, wastewater, toxic effects, and fate and transport of microplastics. The number of studies investigating atmospheric microplastic pollution is still so limited, although microplastics in the atmosphere became one of the notable subjects. Natural and synthetic fibers were mainly detected in the studies investigating microplastic pollution in the air. Textile clothes, anthropogenic activities, and fragmentation of large plastics were indicated as the main sources, while the wind was pointed out as the predominant transport mechanism of atmospheric microplastics. Detailed and comprehensive studies on the determination of the fate and transport of microplastics in the air as well as their health effects are needed.

Terrestrial plants as a potential temporary sink of atmospheric microplastics during transport

Atmospheric transport is an important pathway by which terrestrial microplastics (MPs, with sizes less than 5 mm) can move long distances to remote areas. However, little is known about the environmental behaviors of atmospheric MPs during movement. To address this issue, deposits of MPs on the leaves of plants were studied in two regions, with abundance ranging from 0.07 n/cm2 (pieces per area of leaves) to 0.19 n/cm2. The attached substances were mainly natural materials, but 28% of the total substances were plastics. There was a similar physical-chemical composition of the attached MPs in the two regions suggesting a similar origin. Leaves, regardless of plant species, can indiscriminately retain atmospheric MPs. About 0.13 trillion pieces of MPs are estimated to be attached to leaf surfaces in the top 11 green countries. Leaves of terrestrial plants could be a temporal sink and a source of MPs pollution to remote areas. This is not fully recognized and merits further study.

Examination of the ocean as a source for atmospheric microplastics.

Global plastic litter pollution has been increasing alongside demand since plastic products gained commercial popularity in the 1930’s. Current plastic pollutant research has generally assumed that once plastics enter the ocean they are there to stay, retained permanently within the ocean currents, biota or sediment until eventual deposition on the sea floor or become washed up onto the beach. In contrast to this, we suggest it appears that some plastic particles could be leaving the sea and entering the atmosphere along with sea salt, bacteria, virus’ and algae. This occurs via the process of bubble burst ejection and wave action, for example from strong wind or sea state turbulence. In this manuscript we review evidence from the existing literature which is relevant to this theory and follow this with a pilot study which analyses microplastics (MP) in sea spray. Here we show first evidence of MP particles, analysed by μRaman, in marine boundary layer air samples on the French Atlantic coast during both onshore (average of 2.9MP/m3) and offshore (average of 9.6MP/m3) winds. Notably, during sampling, the convergence of sea breeze meant our samples were dominated by sea spray, increasing our capacity to sample MPs if they were released from the sea. Our results indicate a potential for MPs to be released from the marine environment into the atmosphere by sea-spray giving a globally extrapolated figure of 136000 ton/yr blowing on shore.

A New Contaminant Superhighway? A Review of Sources, Measurement Techniques and Fate of Atmospheric Microplastics

Microplastic pollution is a significant and growing environmental issue. Recent studies have evaluated the atmosphere as an important pathway of microplastic contamination. Airborne microplastics can be transported long distances and accumulate in various terrestrial and aquatic environmental matrices, where they represent a threat to the biosphere. This review systematically summarizes the existing knowledge on airborne microplastics, including the different sampling and analytical techniques, occurrence and sources. We investigate the different sample collection techniques from street dust to indoor and outdoor air and examined sample preparation, pre-treatment and characterization techniques. We further explored the key factors with respect to their occurrence in the environment such as concentration levels, polymer composition, size distribution, shape and colour characteristics. The sources of airborne microplastics were also summarized. The results show that microplastics are ubiquitous in all atmospheric compartments including street dust and indoor and outdoor air at various concentrations, which is influenced by the community’s lifestyle choices, anthropogenic activities and meteorological conditions. Various forms of microplastics including spherules, film, fragments, fibres and granules were identified with fibrous microplastics being the most dominant. Additionally, microplastics of 20 different polymers and varying colour characteristic have been reported in studies focusing on airborne microplastic contamination. The size distribution of microplastics varied among the studied air compartments; however, they were mostly distributed towards the smaller size ranges, less than 1 mm. Our review highlights a need to consider atmospheric pathways in addition to soil and water migration dispersion processes for any holistic assessments of microplastic threats to the biosphere. Moreover, standardization of airborne microplastic sampling methods is needed to optimize the effectiveness of future work in this area.

Microplastic fluxes in a large and a small Mediterranean river catchments: The Têt and the Rhône, Northwestern Mediterranean Sea.

This paper aims at quantifying current riverine fluxes of microplastics (MPs) in two Mediterranean river catchments, a large one and a small one, namely the Rhône and the Têt, which are discharging to the Gulf of Lion in the Northwestern Mediterranean Sea. MP fluxes change markedly through time and space in both river systems. However, no clear relationships between MP concentrations and hydroclimatic conditions have been observed. In the Rhône River a non-linear dilution pattern of MPs in total suspended matter (TSM) during flood conditions could be observed. Although dilution is important, samples during floods exert a strong control on average MP fluxes. Compared to the Rhône River, average MP concentrations in the Têt River were throughout greater and more variable in shape and polymer composition. However, as the study year was exceptionally dry, the average specific MP flux, 76gkm-2y-1, is only slightly larger than the non-flooding value of the Rhône River. We further monitored MP concentrations in shoreline sediments at the mouth of the Têt River to test whether these sediments can represent MP transport in the river. Besides fibers, which probably are easily washed out and transported offshore, MP concentrations and compositions are in agreement with MP loads upstream the river. We also examined the potential role of atmospheric deposition as a source of MP to the Têt River. The average atmospheric MP deposition of 6kgkm-2 y-1 exceeds by far the river average specific MP flux. Moreover, all MPs in atmospheric deposits were fibers, which in terms of mass are of minor importance in the bulk river fluxes. Atmospheric MP deposits may either have been overestimated and/or may be removed from surface waters by efficient removal processes (such as waste water treatment plants).

Accurate quantification and transport estimation of suspended atmospheric microplastics in megacities: Implications for human health

Although atmospheric microplastics have been found to be ubiquitous even on untraversed mountains and have potential impacts on human health, little information concerning their sampling methodology and transport is currently available. Until a realistic quantification of suspended atmospheric microplastics (SAMPs) is obtained, however, any potential health risk assessment for this pollutant will be open to criticism for using an ambiguous dataset. To address this knowledge gap, in May 2019 a trial experiment was performed to explore the potential relationship between sampling volume and SAMP abundance. A significant logarithmic regression between SAMP abundance and the sampling volume of filtrated air was found and the sufficient volume of filtrated air for accurate SAMP quantification was recommended. Investigation results indicated that fibrous and fragment-shaped SAMPs comprised 91% of all of the identified synthetic particles. Interestingly, for the first time, plastic microbeads were also observed in the collected air, constituting 9% of the all of the SAMPs by quantity. Spectral analysis revealed that these SAMPs consisted of polyethylene terephthalate (PET), epoxy resin (EP), polyethylene (PE), alkyd resin (ALK), rayon (RY), polypropylene (PP), polyamide (PA), and polystyrene (PS). PET, EP, PE, and ALK constituted the majority (90%) of all of the polymer types, with quantitative percentages of 51%, 19%, 12%, and 8%, respectively. Based on our numerical modeling simulation, the approximate transport flux of SAMPs during June in Shanghai was estimated, ranging from 9.94 × 104 n/(m·d) to 6.52 × 105 n/(m·d), with a mean of 3.00 ± 1.58 × 105 n/(m·d). The goal of our study was to provide an essential methodological aid for the accurate determination of SAMPs in the environment and a better understanding of terrestrial microplastic transport in megacities.

Consistent Transport of Terrestrial Microplastics to the Ocean through Atmosphere.

Although atmospheric transport and deposition could be an important pathway of terrestrial pollutants to the ocean, little information concerning the presence and distribution of these suspended atmospheric microplastics in marine air is available. We investigated, for the first time, the occurrence and distribution of suspended atmospheric microplastics (SAMPs) in the west Pacific Ocean. In this study, the spatial distribution, morphological appearance, and chemical composition of suspended atmospheric microplastics were studied through continuous sampling during a cruise. SAMPs abundance ranged from 0 to 1.37 n/m3, the median of 0.01 n/m3. Fiber, fragment, and granule SAMPs quantitively constituted 60%, 31%, and 8% of all MPs, respectively. Interestingly, plastic microbeads with numerical proportion of 5% were also observed. A high suspended atmospheric microplastics abundance was found in the coastal area (0.13 ± 0.24 n/m3), while there was less amount detected in the pelagic area (0.01 ± 0.01 n/m3). The amount of suspended atmospheric microplastics collected during the daytime (0.45 ± 0.46 n/m3) was twice the amount collected at night (0.22 ± 0.19 n/m3), on average. Our observations provide field-based evidence that suspended atmospheric microplastics are an important source of microplastics pollution in the ocean, especially the pollution caused by textile microfibers.

Importance of atmospheric transport for microplastics deposited in remote areas

Atmospheric transport is an important pathway for the deposition of micro- and nano-plastics in remote areas. However, the sources and fate of atmospheric microplastics remain poorly understood. A study on atmospheric transport and deposition in the Pyrenean Mountains highlights the movement of microplastics away from known sources (cities, agriculture, and industry) into remote areas. Following this first evidence of atmospheric microplastic deposition in a pristine location, it is necessary to reconsider previous studies on atmospheric microplastic deposition and behavior in remote areas.

Source and potential risk assessment of suspended atmospheric microplastics in Shanghai

A growing body of research has recently revealed that airborne microplastics could be an important source of microplastic pollution in marine environments. However, the origins and spatial distributions of suspended atmospheric microplastics (SAMPs) are poorly understood. Further, SAMPs abundances have only been observed using passive sampling devices that could lead to underestimates of abundances. To address these knowledge-gaps, the current study investigated the potential source and spatial distribution of SAMPs in Shanghai during May 2018 using an active suspended particulate sampler. SAMPs abundances from filtered air ranged from 0 to 4.18 n/m3 (items per cubic meter of air). Microfibers comprised 67% of all SAMPs, followed by fragments and granules comprising 30% and 3% of SAMPs, respectively. μ-FT-IR analysis revealed that the SAMPs consisted of polyethylene terephthalate (PET), polyethylene (PE), polyester (PES), polyacrylonitrile (PAN), poly(N-methyl acrylamide) (PAA), rayon (RY), ethylene vinyl acetate (EVA), epoxy resin (EP), and alkyd resin (ALK). Synthetic compounds comprised 54% of the observed particles, of which PET, PE, PES, PAN, PAA, and RY comprised 91% of the microplastics. Our preliminary evaluation indicated that textile clothes are likely major source of the airborne microplastics. Modeling estimated that approximately 120.7 kg of SAMPs are annually transported through Shanghai air. Moreover, an estimation of the ecological risk from SAMPs indicated that a minor ecological consequence was present, necessitating further evaluation of SAMPs pollution. In addition, modeling estimated that approximately 21 particles of microplastics are inhaled daily by people in Shanghai from outdoor environments. Given the prevalence of airborne microfibers, it is critically urgent to reevaluate procedures for sampling, transporting, and processing microplastic field samples. Future investigations should seek to develop more rigorous and conclusive methods to evaluate these types of samples.