Abstract

Plastic production has increased significantly over the past few decades and has impacted the environment in a negative way. Plastic products have the ability to break down into smaller particles less than 5 mm in size, known as microplastics, which can accumulate in a variety of places such as food and water sources. Recently, a multitude of studies have suggested that microplastics pollute the air we breathe, and humans inhale a great quantity of microplastic particles on a day to day basis. The toxic effects that microplastic inhalation have on the human body are not clearly known because airborne microplastic pollution has emerged as a more recent problem. However, scientists have been able to make some predictions on what could happen to the human body if microplastics are inhaled, based on the limited data available. This paper will give an overview of these studies and suggest mitigation strategies. Steps to lower and prevent airborne microplastic pollution have to be taken urgently to prevent future negative health consequences.

Introduction

Plastic pollution is arguably one of the biggest ecological threats that our planet is currently facing [1]. It is estimated that almost 40 million tons of plastic enter the natural environment each year, and this will continue to grow unless there are dramatic shifts globally in plastic production, recycling, and waste management [2].While physical processes, such as wave action, can break plastic debris into ever smaller fragments [3], and the majority of this plastic waste is not biodegradable. In other words, this debris will remain as plastic, albeit in smaller fragments, and it will likely take hundreds of years for the plastics to break down chemically into its elemental components [4].

Once plastic debris breaks down into fragments less than 5 mm in size, they are termed microplastics [5]. Due to their small size, they can be transported readily, and microplastics have now been found in almost all habitats on this planet, including the polar ice caps [6] and the deepest depths of the ocean [7]. Recently, it has also been discovered that microplastics are now common in our atmosphere [8]. Such air-borne microplastics have the potential to pose a significant threat to human health through chronic inhalation[9]. To assess the extent of this threat, we will review the current knowledge on airborne microplastics and their potential effects on the human body.

In this review, we have five main goals: (1) Examine how microplastics are formed and identify their sources. (2) Examine how we measure and analyse airborne microplastics. (3) Examine how microplastics are distributed throughout the atmosphere. (4) Examine the inhalation of airborne microplastics and the deleterious effects they have on the human body. (5) Examine and suggest directions for future research and policy.

Where do airborne microplastics come from?

In 2018, 359 million tons of plastic were manufactured globally [10]. Most of this plastic production was to create macroplastics (plastic fragments over 5 mm in size); however, this process often simultaneously creates microplastics as a waste product. For example, the grinding and chopping of synthetic material can produce significant quantities of microplastic that are small enough to be emitted directly into the atmosphere via exhaust fumes [11]. Common examples of other sources of airborne microplastics include materials from buildings and construction, waste incineration, landfills, industrial emissions, particles released from traffic, and sewage sludge used as fertilizers[12].

Even after production, macro-plastics will eventually fragment into smaller pieces. Such fragmentation is largely driven by physical processes. For example, the washing of synthetic clothes has been shown to produce significant quantities of airborne micro-fibres [13]. Similarly, marine debris can be readily ground up into smaller fragments by wave action [14]. Moreover, this process of fragmentation is facilitated by photodegradation (from sunlight), thermo-oxidative degradation (slow oxidative breakdown at moderate temperatures), and thermal degradation (at high temperatures) [15]. These degradation processes often make the plastic more brittle and thus promote its fragmentation.

At a certain point, depending on the size, shape, and composition of the microplastic, these plastic fragments will be so small that they can be picked up directly by air currents [16]. Marine microplastics may also enter the atmosphere via a bubble-burst ejection pathway. During this process, micro- and nano- sized particles are ejected from the sea when the breaking of the waves cause bubbles of trapped air to rise to the surface and burst. This bursting of the bubble leaves the nano sized particles expelled and suspended in the air, and available for wind transport [9].

Due to the various pathways that can produce airborne microplastics, the composition of these micro-plastic particles is diverse. The microplastic chemical types found in the air include, but are not limited to: polyvinyl acetate (PVA), polyurethane (PUR), teflon (PTFE), 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) [17].

Measuring and analysing airborne microplastics

To date, three main methods have been used for quantifying the abundance of airborne microplastics. (1) Using an air-vacuum filter. In this method, a vacuum pump attached to a funnel is used to draw a known volume of air over a filter. The microplastics are screened out by the filter, where they can be quantified. (2) Using a rain sampler. The rain sampler is similar to the air-vacuum filter, except that the sampler passively collects microplastics over a filter instead of actively drawing air over the filter. The sampler can be angled straight up to collect particles as they settle or can be placed parallel to the ground to collect samples from horizontal wind currents. (3) Using a Caltech Active Strand Cloudwater Collector (CASSC). The CASCC allows for the collection of microplastics that are suspended in airborne water droplets. The CASCC consists of a fan that drives air over teflon filaments. The moisture in the air containing the microplastics condenses onto the filaments and the microplastics can then be collected in a glass bottle. There is also another alternative method that has been used specifically to assess not just how much microplastics are in the air, but to more specifically assess how much can be inhaled by humans. This method used a breathing thermal manikin that simulates the natural breathing patterns of a human [18].

Distribution of airborne microplastics

Airborne microplastics can undoubtedly travel considerable distances and this likely explains the presence of microplastics in many remote and largely uninhabited locations, including the poles [19]. According to table 1, airborne microplastic pollution has been documented in places all over the globe. The primary vector for transporting airborne microplastics is likely air currents, and thus global wind patterns may be used to explain their overall distribution [12]. Microplastics have also been noted to travel farther if they are attached to dust [17]. Because meteorological factors, such as wind patterns and rainfall, are responsible for the airborne transport of microplastics, there is likely seasonal variation of distribution of microplastics based on seasonal patterns of airflows and precipitation. Indeed, both Zhou et al. (2017) [20] and Allen et al. (2019) [21] recorded higher quantities of airborne microplastics during the spring, summer, and winter, than the fall. In February and March, there was an increased amount of rainfall and snowfall while the distribution of PE was higher [17].

Another important factor is deposition, or the downward movement of airborne microplastics to the ground surface and out of the atmosphere. One of the primary factors depositing plastic out of the atmosphere is precipitation and snowfall. This was shown by Bergman et al. (2019) [6], when they analysed snow deposition on ice platforms in Norway that were not connected to land. As microplastics were found in these samples, it was suggested that they were part of the snow precipitation.

It is clear that densely populated indoor areas may generate more domestic microplastic particles because of a higher frequency of anthropogenic activities such as washing clothes or utilising products/furniture that produce airborne microplastics [11]. Moreover, airborne microplastic levels have also been recorded to vary significantly between outdoor and indoor environments [22]. As expected, indoor concentrations of airborne microplastics tend to be higher than outdoor concentrations. In France, indoor and outdoor air was evaluated for airborne fibers by Dris et al.(2017) [22]. The indoor study sites were apartments and office buildings and the outdoor study site was air outside of the apartment [17]. The indoor concentrations ranged from 1.0 to 60 fibers while the outdoor concentrations ranged from 0.3 to 1.5 fibers. In addition, 67% of indoor fibers were made of natural materials while 33% of fibers contained chemicals [8]. These differences are likely because the dispersion mechanisms are lower in indoor environments (nominal ventilation and air currents), and because of the release of microplastics by indoor furniture and the washing and drying of clothes with tumble dryer exhaust [12].

Inhalation of Airborne Microplastics and Potential Effects on the Human Body

When humans breathe, they inhale not only air but all the additional particles suspended in air. As airborne microplastics are now so prevalent in our atmosphere, it is estimated that humans breathe in approximately 26-130 microplastics per day. To understand how this may affect the human body however, we must make a distinction between inhalation and respiration of airborne microplastics. Inhalation is when particles and fibers enter the nose and mouth and deposit in the upper airway, whereas respiration is when particles are able to reach and deposit in the deep lung [23].

Once microplastics are inhaled, they enter the upper airway and can have a direct effect by colliding with the walls of the upper airway. Some of the particles descend into the smaller airways by gravity. Where they go after inhalation depends on particle properties, physiology and lung anatomy[24][25][26]. After the microplastics are inhaled, clearance methods will start to occur in order to rid the body of microplastic particles. Some examples of clearance methods include sneezing, mucociliary escalator, phagocytosis by macrophages, and lymphatic transport[25][23][27][28][29].

If microplastics are respirable they reach the deep lungs. This occurs when the clearance methods do not work and as a result, the microplastics have nowhere else to go therefore, they remain in the human body and cannot be taken out. Some of the respired microplastics have been detected in lymph nodes, which are nodes where lymphatics collect[27][29]. The microplastics can be removed through these lymphatics however, the majority remain in the lung. Those that remain in the lung cause the loss of mobility of the macrophages and the induction of chemical factors by chemicals. Through this, scarring can occur. For example, Polystyrene has been shown to cause reactive oxygen species (ROS) production which is cytotoxic [30].When microplastics accumulate in the lungs, chronic irritation and inflammation could occur and it may possibly lead to cancer as a result of DNA damage. The effects on the lung could include bronchial asthma like reaction, fibrosis (scar tissue), inflammatory and fibrotic changes of the bronchioles causing chronic bronchitis, and interalveolar septa lesions causing pneumothorax [1]. Additionally, microplastics of 15 to 20 μm cannot be successfully removed from the lungs through macrophages. Therefore, all the microplastic particles that are respired into the deep lung stay there and cannot be removed [31].

Microplastics are harmful to the human body because they are composed of toxic chemicals. Plastics contain many additives. Additives are chemicals intentionally added during plastic production to give the plastic color and transparency and to enhance the performance of plastic products. Although additives improve the efficiency of plastic, they are toxic to the human body. Toxicity is dependent upon the dosage, the exposure, the chemicals, age, sex, etc. One example of a plastic additive is bisphenol A (BPA). BPA is a carbon-based synthetic compound that was added to many plastic products because it made plastic very efficient. BPA was found to be very dangerous because of its hormonal disrupting properties in the human body [32]. Another example of a plastic additive is a phthalate. Phthalates are a class of compounds that are produced in high quantities specifically for plastics. They also make plastics more efficient; however, they are toxic. Because of this, phthalates cannot be present in more than 0.1% of plastic material [33]. Another example of a plastic additive is a heavy metal element. These are added to plastics to make them more efficient because they slow down plastic degradation. These can also be toxic;they have been correlated with cancer in humans and animals [34]. All of these additives are extremely harmful to the human body and some of these chemicals are known as endocrine disrupting chemicals (EDC). If EDCs are inhaled or ingested, illnesses such as hormonal cancers (breast, prostate, testes), reproductive problems (genital malformations, infertility), metabolic disorders (diabetes, obesity), asthma, and neurodevelopmental conditions (learning disorders, autism spectrum disorders) may occur[35].

Not many studies have been conducted on the effects of microplastics on the human body, but plastic debris is known to cause disease in industry workers who are exposed to high concentrations of plastic particles for long periods of time. For example, it has been found that people working in the following industries have suffered consequences from inhaling airborne microplastics: the synthetic textile industry [36], the flock industry[37][38][39][40], and vinyl chloride and PVC industries [41]. Synthetic fibers, such as nylon, polyester, polyurethane, polyolefin, acrylic and vinyl-type polymers, have been linked to respiratory illnesses in people who work in these industries. It has also been found that people who work in these industries have an increased risk of cancer compared to others who do not, and there is a high prevalence of systemic respiratory symptoms in 64.7% of production and maintenance workers in these industries.

Conclusion and Future Research

Research has shown that airborne micro-plastics are now abundant in all surveyed habitat on this planet. Moreover, it is clear that chronic inhalation of micro-plastics has the potential to incur a significant risk to human health [42][43]. Yet, we are still in the early stages of researching airborne microplastics and their effect on human health. Thus, we would like to recommend five focus areas for future research:

1 – Determining which household products are producing the most airborne microplastics.

2 – Further research into how much microplastic needs to be inhaled before it has a noticeable effect on human health.

3 – Further research to determine if certain microplastics pose a greater threat to human health than others.

4 – Clinical studies to link the prevalence of certain lung issues to the potential presence of microplastics in the lungs.

5 – Further studies to quantify the levels of airborne microplastics in countries and continents that have not been assessed, e.g. Africa, Australasia, Antarctica.

In summary, airborne microplastics have been located in vast geographic terrains.The detrimental effects to human health and well being are beginning to be studied. As we generate more information from these research areas, we can better assess the amount of airborne microplastics we are inhaling and the effects this will have on our health. This knowledge is key to assessing the risk of airborne microplastics and for designing strategies to prevent and eliminate airborne microplastics on a global scale.

FIGURES

Figure 1. The Cycle of Microplastics – This figure represents how microplastics flow through the atmosphere. The yellow, green, and pink shapes represent the microplastics while the arrows represent how the microplastics flow from the earth to the atmosphere.

References

1. Beaumont, M. Aanesen, M. C. Austen, T. Börger, J. R. Beckett, and S. William \”Occupational respiratory diseases.\” New England Journal Of Medicine 342, no. 6: 406-413 (2000).
2. Lau, W. W., Y. Shiran , R. M. Bailey, E. Cook, M. R. Stuchtey, J. Koskella, C. A. Velis, L. Godfrey, J. Boucher, M. B. Murphy, R. C. Thompson, E. Jankowska, A. C. Castillo, T. D. Pilditch, B. Dixon, L. Koerselman, E. Kosior, E. Favoino, J. Gurberlet, S Baulch, M. E. Atreya, D. Fischer, K. K. He, M. M. Petit, U. R. Sumaila, E. Neil, M. V. Bernhofen, K. Lawrence, and J. E. Palardy “Evaluating scenarios toward zero plastic pollution.” Science (2020).
3. Min, K., J. D. Cuiffi, and R. T. Mathers \”Ranking environmental degradation trends of plastic marine debris based on physical properties and molecular structure.\” Nature Communications 11.1: 1-11 (2020).
4. Zheng, Y., E. Yanful, and A. Bassi “A review of plastic waste biodegradation.” Critical Reviews In Biotechnology 25, no. 4: 243-250 (2005).
5. Thompson, R. C., Y. Olsen, R. P. Mitchell, A.Davis, S. J. Rowland, A. W. John, D. McGonigle and A. E. Russell. “Lost at sea: where is all the plastic?” Science, 304, no. 5672, 838 (2004).
6. Bergmann, M., S. Mützel, S. Primpke, M. B. Tekman, J. Trachsel, and G. Gerdts \”White and wonderful? Microplastics prevail in snow from the Alps to the Arctic.” Scientific Advances 5: eaax1157 (2019).
7. Peng, G., R. Bellerby, F, Zhang, X. Sun and D. Li The ocean’s ultimate trashcan: Hadal trenches as major depositories for plastic pollution. Water Research, 168, 115121 (2020).
8. Gasperi, J., S. L. Wright, R. Dris, F. Collard, C. Mandin, M. Guerrouache, V. Langlois, F. J. Kelly, and B. Tassin \”Microplastics in air: are we breathing it in?.\” Current Opinion in Environmental Science And Health 1: 1-5 (2018).
9. Prata, J. C “Airborne microplastics: consequences to human health?” Environmental Pollution, 234, 115-126 (2018).
10. AISBL, PlasticsEurope. \”Plastics–the Facts 2018.\” Information accessed at http://www.-plasticseurope. org/application (2019).
11. Dris, R., J. Gasperi, M. Saad, C. Mirande, and B. Tassin \”Synthetic fibers in atmospheric fallout: a source of microplastics in the environment?.\” Marine Pollution Bulletin 104, no. 1-2: 290-293 (2016).
12. Kaya, Ahmet Tunahan, Meral Yurtsever, and Senem Çiftçi Bayraktar. \”Ubiquitous exposure to microfiber pollution in the air.\” The European Physical Journal Plus 133, no. 11: 488 (2018).
13. De Falco, F., G. Gentile, E. Di Pace, M. Avella, and M. Cocca “Quantification of microfibres released during washing of synthetic clothes in real conditions and at lab scale.” The European Physical Journal Plus, 133, no. 7: 257 (2018).
14. Corcoran, P. L., M. C. Biesinger, and M. Grifi. “Plastics and beaches: a degrading relationship.” Marine Pollution Bulletin, 58, no. 1: 80-84 (2009).
15. Andrady, A. L \”Microplastics in the marine environment.\” Marine Pollution Bulletin 62, no. 8: 1596-1605 (2011).
16. Enyoh, C. E., A. W. Verla, E. N. Verla, F. C. Ibe, and C. E. Amaobi \”Airborne microplastics: a review study on method for analysis, occurrence, movement and risks.\” Environmental Monitoring And Assessment 191, no. 11: 668 (2019).
17. Allen, S., D. Allen, K. Moss, G. Roux, V. R. Phoenix, and J. E. Sonke \”Examination of the ocean as a source for atmospheric microplastics.\” PloS One 15, no. 5: e0232746 (2020).
18. Vianello, A., R. L. Jensen, L. Liu, and J. Vollertsen \”Simulating human exposure to indoor airborne microplastics using a Breathing Thermal Manikin.\” Scientific Reports 9, no. 1: 1-11 (2019).
19. Obbard, R. W., S. Sadri, Y. Q. Wong, A. A. Khitun, I. Baker, and R. C. Thompson \”Global warming releases microplastic legacy frozen in Arctic Sea ice.\” Earth\’s Future 2, no. 6: 315-320 (2014).
20. ZHOU, Qian, ChongGuo TIAN, and YongMing LUO. \”Various forms and deposition fluxes of microplastics identified in the coastal urban atmosphere.\” Chinese Science Bulletin 62, no. 33: 3902-3909 (2017).
21. Allen, Steve, Deonie Allen, Vernon R. Phoenix, Gaël Le Roux, Pilar Durántez Jiménez, Anaëlle Simonneau, Stéphane Binet, and Didier Galop. \”Atmospheric transport and deposition of microplastics in a remote mountain catchment.\” Nature Geoscience 12, no. 5: 339-344 (2019).
22. Dris, R., Johnny G., C. Mirande, C. Mandin, M. Guerrouache, V. Langlois, and B. Tassin \”A first overview of textile fibers, including microplastics, in indoor and outdoor environments.\” Environmental Pollution 221: 453-458 (2017).
23. Donaldson, K., and C. L. Tran \”Inflammation caused by particles and fibers.\” Inhalation Toxicology 14, no. 1: 5-27 (2002).
24. Carvalho, T. C., Jay I. Peters, and Robert O. Williams III \”Influence of particle size on regional lung deposition–what evidence is there?\” International Journal Of Pharmaceutics 406, no. 1-2: 1-10 (2011).
25. Brauer, M. and Churg, A. \”Ambient atmospheric particles in the airways of human lungs.\” Ultrastructural Pathology 24, no. 6: 353-361 (2000).
26. Geiser, M., P. Gerber, I. Maye, V. I. Hof, and P. Gehr \”Retention of Teflon particles in hamster lungs: a stereological study.\” Journal of aerosol medicine 13, no. 1: 43-55 (2000).
27. Lippmann, M., D. B. Yeates, and R. E. Albert \”Deposition, retention, and clearance of inhaled particles.\” Occupational And Environmental Medicine 37, no. 4: 337-362 (1980).
28. Morrow, P. E \”Possible mechanisms to explain dust overloading of the lungs.\” Toxicological Sciences 10, no. 3: 369-384 (1988).
29. Tran, C. L., D. Buchanan, R. T. Cullen, A. Searl, A. D. Jones, and K. Donaldson \”Inhalation of poorly soluble particles. II. Influence of particle surface area on inflammation and clearance.\” Inhalation Toxicology 12, no. 12: 1113-1126 (2000).
30. Schwarze, P. E., J. Øvrevik, M. Låg, M. Refsnes, P. Nafstad, R. B. Hetland, and E. Dybing \”Particulate matter properties and health effects: consistency of epidemiological and toxicological studies.\” Human And Experimental Toxicology 25, no. 10: 559-579 (2016).
31. Wright, S. L., and F. J. Kelly \”Plastic and human health: a micro issue?.\” Environmental Science And Technology 51, no. 12: 6634-6647 (2017).
32. Villanueva, O. , E., J. Jaumot, R. Martínez, L. N. Martín, B. Piña, and R. Tauler. \”Assessment of endocrine disruptors effects on zebrafish (Danio rerio) embryos by untargeted LC-HRMS metabolomic analysis.\” Science Of The Total Environment 635: 156-166 (2018).
33. Rani, Manviri, W. J. Shim, G. M. Han, M. Jang, N. A. A. Odaini, Y. K. Song, and S. H. Hong\”Qualitative analysis of additives in plastic marine debris and its new products.\” Archives Of Environmental Contamination And Toxicology 69, no. 3: 352-366 (2015).
34. Tchounwou, P. B., C. G. Yedjou, A. K. Patlolla, and D. J. Sutton \”Heavy metal toxicity and the environment.\” In Molecular, clinical and environmental toxicology, pp. 133-164. Springer, Basel (2012).
35. Cingotti, N., and G.K. Jensen Health and Environment Alliance (HEAL). Food Contact Materials and Chemical Contamination; Health and Environment Alliance: Brussels, Belgium (2019).
36. Pimentel, J. Cortez, R. Avila, and A. Galvão Lourenço \”Respiratory disease caused by synthetic fibres: a new occupational disease.\” Thorax 30, no. 2: 204-219 (1975).
37. Atis, S., B. Tutluoglu, E. Levent, C. Ozturk, A. Tunaci, K. Sahin, A. Saral, I. Oktay, A. Kanik, and B. Nemery \”The respiratory effects of occupational polypropylene flock exposure.\” European Respiratory Journal 25, no. 1: 110-117 (2005).
38. Barroso, E., M. D. Ibañez, F. I. Aranda, and S. Romero \”Polyethylene flock-associated interstitial lung disease in a Spanish female.\” European Respiratory Journal 20, no. 6: 1610-1612 (2002).
39. Eschenbacher, W. L., K. Kreiss, M. D. Lougheed, G. S. Pransky, B. Day, and R. M. Castellan \”Nylon flock–associated interstitial lung disease.\” American Journal Of Respiratory And Critical Care Medicine 159, no. 6: 2003-2008 (1999).
40. Kern, D. G., C. Kuhn III, E. W. Ely, G. S. Pransky, C. J. Mello, A. E. Fraire, and J. Müller. \”Flock worker\’s lung: broadening the spectrum of clinicopathology, narrowing the spectrum of suspected etiologies.\” Chest 117, no. 1: 251-259 (2000).
41. Xu, H., E. Verbeken, H. M. Vanhooren, B. Nemery, and P. HM Hoet \”Pulmonary toxicity of polyvinyl chloride particles after a single intratracheal instillation in rats. Time course and comparison with silica.\” Toxicology And Applied Pharmacology 194, no. 2: 111-121 (2004).
42. Campanale, C., C. Massarelli, I. Savino, V. Locaputo, and V. F. Uricchio \”A detailed review study on potential effects of microplastics and additives of concern on human health.\” International Journal of Environmental Research And Public Health 17, no. 4: 1212 (2020).
43. Chen, G., Q. Feng, and J. Wang \”Mini-review of microplastics in the atmosphere and their risks to humans.\” Science Of The Total Environment 703: 135504 (2020).

APPENDIX

TABLES

Table 1.

Summary table containing data from a thorough literature review of all published studies on airborne microplastics worldwide. The different types of microplastics found in these studies include: polyvinyl acetate (PVA), polyurethane (PUR), teflon (PTFE), 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).

Location:	Average Concentration:	Polymer Types:	Colors:	Size:	Shape:	Reference:
Paris, France	118 n/m2/day, 110 ± 96 n/m2/day (urban)	N/A	N/A	100- 5000μm	fiber, fragment	Dris et al., 2015
Paris, France	53 ± 38 n/m2/day, (sub-urban) 29% MPs, 5.4 n/m3 (outdoor)	N/A	N/A	50-5000μm	fiber	Dris et al., 2016
Paris, France	0.9 n/m (indoor), 33% MPs	PA, PP	N/A	50-3250μm	fiber	Dris et al., 2017
Dongguan, China	36 ± 7 n/m2/day	PE, PP, PS	blue, red, yellow, white, black	<00-4200μm	fiber, fragment, film, foam	Cai et al., 2017
Yantai, China	400 n/m2/day	PET, PE, PVC, PS	white, black, red, transparent	50-3000μm	fiber, fragment, film, foam	Zhou et al., 2017
Shanghai, Chan	1.42 ± 1.42 n/m3	PET, PE, PES, PAN, PAA, EVA, RY, EP, ALK	blue, black, red, transparent, brown, green, yellow, gray	23-5000μm	fiber, fragment, granule	Liu et al., 2019
Hamburg, Germany	275 n/m2/day	PE, EVAC, PTFE, PVA, PET	N/A	63-5000μm	fragment, fiber	Klein et al., 2019
Asaluyeh, Iran	1 n/m3	N/A	white/transparent, red, yellow, blue, black	N/A	fiber, film, spherule, fragment	Abbasi et al., 2019
Pyrenees	365 n/m2/day	PS, PP, PE, PET	N/A	50-2600μm	fiber, fragment, film	Allen et al., 2019
London, United Kingdom	510 to 925 fibrous microplastics/m2/d	PS, PP, PE, PET, PUR, PVC, PVA	N/A	400–500 μm	fragment, film, granules, foam, fiber	Wright et al., 2020
California, United States	12.8 ± 4.0 (indoor) 12.0 ± 3.4 (outdoor)	PVC, PVC, HS, PE, PS, PC, PA, ABS, PET	N/A	indoors: 641±810.7 μm outdoors: 616±536.7 μm	fiber, fragment	Gaston et al., 2020
Indian Ocean to South China Sea	1.0 items/100 m3	PP, PEVA, PET, PEP, PAN-AA, PR	black, blue, brown, red, white, yellow	58.59 μm to 2251.54 μm		Wang et al., 2019
Coastal Ireland	23 mf L–1	PET, PAN, PE, PP, organic	N/A	2-4 mm	N/A	Roblin et al., 2020

About The Author

Maya Mallavarapu is a sophomore at Cedar Falls Highschool. In her free time, she enjoys spending time with her family and friends and playing tennis. She competes in tennis tournaments throughout the Missouri Valley year round. She is passionate about helping the environment and saving the planet.