Title: Rethinking microplastics as a diverse contaminant suite
Abstract: Environmental Toxicology and ChemistryVolume 38, Issue 4 p. 703-711 ET&C FocusFree Access Rethinking microplastics as a diverse contaminant suite Chelsea M. Rochman, Corresponding Author Chelsea M. Rochman [email protected] orcid.org/0000-0002-2642-6574 Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript. Address correspondence to [email protected] for more papers by this authorCole Brookson, Cole Brookson Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorJacqueline Bikker, Jacqueline Bikker Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorNatasha Djuric, Natasha Djuric Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorArielle Earn, Arielle Earn Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorKennedy Bucci, Kennedy Bucci Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorSamantha Athey, Samantha Athey Department of Earth Sciences, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorAimee Huntington, Aimee Huntington Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorHayley McIlwraith, Hayley McIlwraith Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorKeenan Munno, Keenan Munno Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorHannah De Frond, Hannah De Frond Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorAnna Kolomijeca, Anna Kolomijeca Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorLisa Erdle, Lisa Erdle Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorJelena Grbic, Jelena Grbic Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorMalak Bayoumi, Malak Bayoumi Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorStephanie B. Borrelle, Stephanie B. Borrelle Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, Canada David H. Smith Conservation Research Program, Society for Conservation Biology, Washington, DC, USAThese authors contributed equally to this manuscript.Search for more papers by this authorTina Wu, Tina Wu Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorSamantha Santoro, Samantha Santoro Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorLarissa M. Werbowski, Larissa M. Werbowski Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorXia Zhu, Xia Zhu Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorRachel K. Giles, Rachel K. Giles Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorBonnie M. Hamilton, Bonnie M. Hamilton Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorClara Thaysen, Clara Thaysen Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorAshima Kaura, Ashima Kaura Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorNatasha Klasios, Natasha Klasios Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorLauren Ead, Lauren Ead Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorJoel Kim, Joel Kim Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorCassandra Sherlock, Cassandra Sherlock Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorAnnissa Ho, Annissa Ho Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorCharlotte Hung, Charlotte Hung Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this author Chelsea M. Rochman, Corresponding Author Chelsea M. Rochman [email protected] orcid.org/0000-0002-2642-6574 Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript. Address correspondence to [email protected] for more papers by this authorCole Brookson, Cole Brookson Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorJacqueline Bikker, Jacqueline Bikker Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorNatasha Djuric, Natasha Djuric Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorArielle Earn, Arielle Earn Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorKennedy Bucci, Kennedy Bucci Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorSamantha Athey, Samantha Athey Department of Earth Sciences, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorAimee Huntington, Aimee Huntington Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorHayley McIlwraith, Hayley McIlwraith Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorKeenan Munno, Keenan Munno Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorHannah De Frond, Hannah De Frond Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorAnna Kolomijeca, Anna Kolomijeca Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorLisa Erdle, Lisa Erdle Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorJelena Grbic, Jelena Grbic Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorMalak Bayoumi, Malak Bayoumi Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorStephanie B. Borrelle, Stephanie B. Borrelle Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, Canada David H. Smith Conservation Research Program, Society for Conservation Biology, Washington, DC, USAThese authors contributed equally to this manuscript.Search for more papers by this authorTina Wu, Tina Wu Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorSamantha Santoro, Samantha Santoro Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorLarissa M. Werbowski, Larissa M. Werbowski Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorXia Zhu, Xia Zhu Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorRachel K. Giles, Rachel K. Giles Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorBonnie M. Hamilton, Bonnie M. Hamilton Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorClara Thaysen, Clara Thaysen Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorAshima Kaura, Ashima Kaura Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorNatasha Klasios, Natasha Klasios Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorLauren Ead, Lauren Ead Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorJoel Kim, Joel Kim Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorCassandra Sherlock, Cassandra Sherlock Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorAnnissa Ho, Annissa Ho Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this authorCharlotte Hung, Charlotte Hung Department of Ecology and Evolutionary Biology, University of Toronto, St. George Campus, Toronto, Ontario, CanadaThese authors contributed equally to this manuscript.Search for more papers by this author First published: 25 March 2019 https://doi.org/10.1002/etc.4371Citations: 442 AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Microplastics are not microplastics are not microplastics, just like pesticides are not pesticides are not pesticides. “Microplastics,” like other classes of chemical contaminants, is a catch-all term for a variety of unique chemical compounds. Yet, many scientific publications, policy reports, and media articles present microplastics as if they are simply a single compound or type of material. Such simple communications have consequences, leading to simplified studies and protocols that may be inadequate to inform us of the sources and fate of microplastics, as well as their biological and ecological implications. For example, studying the fate and effects of one plastic type with a specific shape and size does not tell us the fate and effects of microplastics in general. Moreover, not recognizing the diversity of materials in a microplastics sample may overlook the complexity necessary to inform robust quality analysis and quality control (QA/QC) needed in sampling and analytical measurement techniques. For instance, some methods are better at recovering specific sizes, shapes, or types of microplastics. Simplifying microplastics as a single compound has also led to confusion around the need for new policies and strategies to reduce future emissions of microplastics. For example, some policymakers and scientists are under the impression that banning microbeads from rinse-off personal care products has eliminated future releases of microplastics in general to the environment. In reality, such bans eliminate only one source of the diverse and complex emerging global contaminant suite that is “microplastics.” This can be compared to banning one specific use of a pesticide (e.g., in the home), leaving the market full of other applications of diverse pesticides that need to continue to be assessed for environmental persistence, bioavailability, and toxicity. In our Focus article, we make the case that it is necessary to rethink microplastics (plastic particles <5 mm in size) and consider them a suite or class of contaminants, in the same way we do for pesticides, trace metals, or flame retardants. Microplastics are diverse; they come from many different product types; incorporate a broad range of sizes, colors, and morphologies; are composed of various polymers; and include a broad array of chemical additives (Figure 1 and Textboxes 1 and 2). This diversity is important to consider, and thinking of them like we do other classes of contaminants may help us advance methods for sampling and analysis and help us better understand the sources from which they enter the environment; their fate in water, sediment, and organisms; their toxicity; and relevant policies for mitigation. Figure 1Open in figure viewerPowerPoint Microplastics are made with a variety of polymers, augmented with an array of additives that can be manufactured into a multitude of products. Sources of microplastics can be either primary or secondary, and microplastics may be any size less than 5 mm. Microplastics are described with at least 7 morphologies and are found in many different colors. When in the environment, microplastics can sorb numerous chemical contaminants, including heavy metals and persistent organic pollutants. This is not an exhaustive list. PP = polypropylene; LDPE = low density polyethylene; HDPE = high-density polyethylene; PVC = polyvinyl chloride; PU = polyurethane; PET = polyethylene terephthalate; PS = polystyrene; ABS = acrylonitrile butadiene styrene; PMMA = polymethyl methacrylate; POM = polyoxymethylene; PBT = polybutylene terephthalate; PC = polycarbonate; PA = polyamides; SAN = styrene-acrylonitrile; PEEK = polyether ether ketone; PSU = polyarylsulfone; PAH = polycyclic aromatic hydrocarbon; PCB = polychlorinated biphenyl; DDT = dichlorodiphenyltrichloroethane; PBDE = polybrominated diphenyl ethers. RETHINKING MICROPLASTICS TO INCORPORATE THEIR DIVERSITY Just like pesticides are made of diverse molecules, have varying molecular structures, and can be used for a variety of applications (e.g., fungicides, herbicides), microplastics are made from diverse molecules, have varying molecular structures, and come from products with various applications (e.g., tires, textiles, and packaging). What is unique to pesticides and other chemical contaminants is that microplastics are particles, comprising different sizes, shapes, and colors. Microplastic particles are not simply “microplastic” but a diverse suite of contaminants that we refer to as “microplastics.” Diverse product types As a contaminant class, microplastics come from a large diversity of product types and are generally classified as either primary or secondary. Primary microplastics are manufactured to be <5 mm in size. They include preproduction pellets used to make plastic products and microbeads used as abrasives for industrial purposes or in personal care products. Secondary microplastics are small pieces of plastic which are not produced intentionally but instead are the result of the breakup and fragmentation of larger plastic items via biological, physical, and chemical processes. Secondary microplastics can form during product use (e.g., microfibers shed from clothing during washing or tire wear particles) or once released into the environment (e.g., via fragmentation). Fragmentation is mediated by the polymer type and environmental conditions, which can be highly variable (Sivan 2011; Gewert et al. 2015). Microplastics can be a by-product of many plastic products, including construction materials, agricultural materials, furniture, clothing, and food packaging (Figure 1). Diverse sizes Microplastics encompass a broad range of sizes. Most often, they are defined as any plastic particle <5 mm in one dimension as defined by the National Oceanographic and Atmospheric Association (Figure 1). Others argue for size categorization that matches the metric system (e.g., 1–999 μm are microplastics). However, there is generally no lower limit, and nano-sized plastics (<0.1 μm) are often included in this definition. The way that discrete sizes and ranges of size are reported among researchers varies. For example, researchers may use multiple grades of sieves to size-fractionate samples, and thus their categorization is defined by the sizes of their sieves used during sample preparation. Defining how microplastics are described in relation to size is a prevalent topic of discussion among researchers in the field. Historically, researchers predominantly sampled microplastics using manta trawls with a 333-μm mesh net, but methods are evolving toward using smaller mesh sizes or collecting bulk water (Barrows et al. 2017). In addition, researchers are beginning to expand their analytical techniques to incorporate those that can detect and identify smaller and smaller microparticles. As a result, the sizes of microplastics reported in the literature are becoming more diverse, incorporating a broader range that is dictated by the lower limit defined by our sampling or analytical methodologies. Diverse shapes and colors Microplastics come in many shapes and colors. The shape of a microplastic is often used to assign it to a common category, which helps inform the source (Helm 2017). Generally, researchers use somewhere between 4 and 7 different categories defined by shape or morphology, which include fiber, fiber bundle, fragment, sphere (or bead), pellet, film, and foam (Figure 1). To help with source apportionment, we know that certain shapes are generally shed from different products. This provides clues related to where microplastics in nature may originate. For example, fibers and fiber bundles tend to shed from clothing, upholstery, or carpet; pellets are generally associated with industrial feedstock; spheres may be microbeads from personal care products or industrial scrubbers; and foam often comes from expanded polystyrene foam products such as insulation or food packaging. Detailed descriptions and images of each of these shapes can be found in Textbox 1. TEXTBOX 1: Fibers may have clean-cut ends (a) or fraying (b). Fiber bundles (c) are in a tightly wound mass that cannot be untangled. Fragments are rigid (d,e) and irregular (f). Spheres (g) are round with a smooth surface. Pellets (h) are typically rounded or cylindrical. Films (i) are flat, thin, and malleable. Foams (j) are soft and compressible TEXTBOX 1: Fibers may have clean-cut ends (a) or fraying (b). Fiber bundles (c) are in a tightly wound mass that cannot be untangled. Fragments are rigid (d,e) and irregular (f). Spheres (g) are round with a smooth surface. Pellets (h) are typically rounded or cylindrical. Films (i) are flat, thin, and malleable. Foams (j) are soft and compressible. Fibers are flexible, with equal thickness throughout and ends that are clean-cut, pointed, or fraying. Typically, they are tensile and resistant to breakage. The durability varies among materials and their state of degradation. Fibers are present in a range of colors, which may be inconsistent across one particle due to bleaching. Fiber bundles comprise 20 or more individual fibers tightly wound in a mass that cannot be untangled. Fiber bundles should only be classified as such when it is too challenging to quantify individual fibers or when untangling the mass may lead to breakage of individual fibers. Fibers present in bundles should be consistent in appearance (i.e. color, thickness, surface texture). Fragments have a rigid structure and sometimes irregular shape. They can be round, subround, angular, or subangular. They are not always equally thick throughout and can appear twisted or curled. Shavings, droplets, and seams from plastic manufacturing fit within this category. Fragments can be any color or combination of colors. Spheres are round in shape with smooth surfaces. Spheres may also be present as hemispheres, possibly the result of breakage during manufacturing, use, or weathering. They typically range in size between 100 µm and 2 mm. Pellets (sometimes called “nurdles”) are similar to spheres but tend to be larger, generally ranging between 3 and 5 mm. Pellets are often rounded or cylindrical in shape. Both spheres and pellets can be any color. Films are flat, thin, and malleable. Films can fold or crease but do not break apart easily. Films are typically partially or fully transparent and are found in a range of colors. Foams are soft, compressible, and cloud-like. They are usually white and/or opaque but can be any color. Diverse polymer types Microplastics are composed of a diverse suite of polymer types just like pesticides are composed of a diverse suite of molecular structures. All plastic polymers consist of repeating monomers, which form the backbone of the polymer. This backbone structure is the fundamental difference between polymer types, informing a plastic's physical and chemical properties (Textbox 2). The most produced and consumed polymer types are polypropylene, low-density polyethylene (LDPE), high-density polyethylene (HDPE), polyvinyl chloride (PVC), polyurethane, polyethylene terephthalate (PET; also known as polyester), and polystyrene (PlasticsEurope 2017). This diversity of polymers is necessary to fulfill the many applications of plastics. For example, LDPE is too flimsy to be used in water bottles, and thus PET is used instead. Also, LDPE is often used in single-use shopping bags, food packaging, and film. In addition to bottles, PET is produced in fiber form to make synthetic clothing. Although the polymers listed in the previous paragraph are the most commonly used, countless others exist. Plastics are divided into 2 families: thermoplastics and thermosets. Thermoplastics can be melted when heated and hardened when cooled. They include many of the plastics described in the previous paragraph (PET, polypropylene, polystyrene, LDPE, HDPE, polyurethane, PVC) and others, such as acrylonitrile butadiene styrene, polymethyl methacrylate, polyoxymethylene, polybutylene terephthalate, polycarbonate, polyamides, elastomers, styrene-acrylonitrile, polyether ether ketone, fluoropolymers, and polyarylsulfone. Thermoset plastics undergo a chemical change when heated. They include polyurethane, epoxy resins, acrylic, urea-formaldehyde, vinyl esters, and phenolic resins. Thus, microplastics are not comprised of one material; instead, they come from a complex group of hundreds of chemically unique substances. TEXTBOX 2: Some examples of different chemical structures of polymers associated with common plastic types TEXTBOX 2: Some examples of different chemical structures of polymers associated with common plastic types. Polyethylene terephthalate (PET) Polypropylene (PP) Polystyrene (PS) Polyethylene (PE) Polyvinyl chloride (PVC) Polyurethane (PU) Diverse chemical cocktails For some applications, chemical contaminants like pesticides or flame retardants are used in mixtures of various different chemical congeners. For microplastics, they are always found in the environment as a mixture or diverse suite of chemicals. Although plastic is often described as an inert material because of its bulky molecular structure, every piece of plastic contains a complex chemical cocktail of monomers, oligomers, and additives. In addition, chemical additives are added to the polymers during production, sometimes accounting for a large proportion of the overall weight (e.g., phthalates, which are used to alter the properties of plastics, can comprise up to 50% of a PVC product's total weight). There are several categories of additives, including plasticizers, colorants, reinforcements or fillers, flame retardants, and stabilizers. Plasticizers, such as phthalates, alter plastic from a hard, glassy material into a soft, rubbery material. Colorants are used to color the plastic product. Reinforcements or fillers enhance the mechanical properties of plastic, such as the strength of the material. Flame retardants are used for specific applications, such as building materials and electronics. Stabilizers increase the longevity and stability of an end product. When found in nature, the complex mixture of chemicals associated with microplastics also includes sorbed pollutants. Microplastics accumulate organic chemicals and trace metals from the surrounding environment (Rochman 2015). For example, microplastics are known to sorb persistent organic pollutants, such as polycyclic aromatic hydrocarbons, polychlorinated biphenyls, and DDT, as well as