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Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2021. Reckoning with the U.S. Role in Global Ocean Plastic Waste. Washington, DC: The National Academies Press. doi: 10.17226/26132.
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Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2021. Reckoning with the U.S. Role in Global Ocean Plastic Waste. Washington, DC: The National Academies Press. doi: 10.17226/26132.
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Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2021. Reckoning with the U.S. Role in Global Ocean Plastic Waste. Washington, DC: The National Academies Press. doi: 10.17226/26132.
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Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2021. Reckoning with the U.S. Role in Global Ocean Plastic Waste. Washington, DC: The National Academies Press. doi: 10.17226/26132.
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Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2021. Reckoning with the U.S. Role in Global Ocean Plastic Waste. Washington, DC: The National Academies Press. doi: 10.17226/26132.
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Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2021. Reckoning with the U.S. Role in Global Ocean Plastic Waste. Washington, DC: The National Academies Press. doi: 10.17226/26132.
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Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2021. Reckoning with the U.S. Role in Global Ocean Plastic Waste. Washington, DC: The National Academies Press. doi: 10.17226/26132.
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Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2021. Reckoning with the U.S. Role in Global Ocean Plastic Waste. Washington, DC: The National Academies Press. doi: 10.17226/26132.
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Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2021. Reckoning with the U.S. Role in Global Ocean Plastic Waste. Washington, DC: The National Academies Press. doi: 10.17226/26132.
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Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2021. Reckoning with the U.S. Role in Global Ocean Plastic Waste. Washington, DC: The National Academies Press. doi: 10.17226/26132.
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Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2021. Reckoning with the U.S. Role in Global Ocean Plastic Waste. Washington, DC: The National Academies Press. doi: 10.17226/26132.
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Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2021. Reckoning with the U.S. Role in Global Ocean Plastic Waste. Washington, DC: The National Academies Press. doi: 10.17226/26132.
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Summary Global ocean plastic waste originates from materials introduced in the 20th century to deliver wide-ranging benefits at low cost. Plastics increased an era of disposability for products and packaging used for a short time and then thrown away. The result has been a dramatic rise in plastic waste, which in turn leaks to the environment, including the ocean. Plastic waste has a range of adverse impacts, some of which are only beginning to be recognized and understood. Over the past decade, research on ocean plastic pollution has revealed that plastic waste is present in almost every marine habitat, from the ocean surface to deep sea sediments to the ocean’s vast mid-water region, as well as the Laurentian Great Lakes. An estimated 8 million metric tons (MMT) of plastic waste enter the world’s ocean each year—the equivalent of dumping a garbage truck of plastic waste into the ocean every minute. If current practices continue, the amount of plastics discharged into the ocean could reach up to 53 MMT per year by 2030, roughly half of the total weight of fish caught from the ocean annually. Society is grappling with the massive scale of the challenge of plastic waste with responses ranging from beach cleanups and local bans to extended producer responsibility schemes, circular economy commitments, country-level plans and commitments, and a call for a global treaty. Decision makers are calling for reliable syntheses of the state of scientific knowledge at national and global levels. This report is designed to provide that synthesis for U.S. decision makers. The contribution arose from the Save Our Seas 2.0 Act, sponsored by a bipartisan group of 19 senators, which passed into law on December 18, 2020, in the 116th Congress. Among a variety of components in the law, it called for the National Academies of Sciences, Engineering, and Medicine to lead a study examining the United States’ contribution to global ocean plastic waste. The task for the committee was to review data on the size of U.S. contribution to plastic waste generation, waste mismanagement, the paths these wastes take to the ocean, and the distribution and fate of these wastes once they leak into the ocean. The committee assessed the potential value of a national marine debris tracking and monitoring system and how such a system might be designed and implemented. Finally, the committee identified knowledge gaps and recommended potential means to reduce U.S. contributions to global ocean plastic waste. U.S. PRODUCTION AND GLOBAL TRADE Over a 50-year period, global plastic production increased nearly 20-fold, from 20 MMT in 1966 to 381 MMT in 2015. The U.S. contribution to global ocean plastic waste begins with the plastics produced and used in this country or exported to other nations, as well as plastics manufactured elsewhere that enter the U.S. waste stream through trade. Petrochemical plants convert fossil-based feedstocks (e.g., crude oil, natural gas liquids) into polymers, while biobased plastics are plastics in which the carbon originates, in whole or in part, from renewable biomass feedstock such as sugar cane, canola, and corn. More than 99% of the plastic resin produced globally is made from fossil-based feedstocks. The majority of plastics are hydrocarbon plastics (from fossil-based or biobased feedstocks). Hydrocarbon plastics have a strong carbon-carbon bond, making them resistant to biodegradation. Prepublication Copy 1

Reckoning with the U.S. Role in Global Ocean Plastic Waste Plastics are a family of synthetic polymers composed of resins that have different chemical and physical structures; examples include polyethylene, polyethylene terephthalate (PET), and polypropylene. In 2019, a total of 70 MMT of plastic resin was produced in North America, which can be compared to a global production of 368 MMT, according to Plastics Europe. Data for resin production are not available for the United States alone. While trends for different types of plastic resin vary, the overall trend for resin supply and production has increased over the past 10 years. Using the American Chemistry Council data, the committee estimated in 2020 that for eight resins, a total of 41.1 MMT was produced in North America. This estimate is not complete and does not include all plastics produced because the committee was unable to identify data for PET, thermoset, and resin fibers. In addition to producing plastic resin, the United States imports and exports plastic products. The U.S. trend of both plastic exports and imports has been increasing over the past three decades. According to the U.S. Census Trade data, in 2020 the United States exported 2,342,368 categories of plastic products, defined as “the number of individual export line items,” at a value of $60.2 billion. In 2020, the United States imported 5,747,472 categories of plastic products (“the number of individual import line items”) at a value of $58.9 billion. Conclusion 1: Because the vast majority of plastics are carbon-carbon backbone polymers and have strong resistance to biodegradation, plastics accumulate in natural environments, including the ocean, as pervasive and persistent environmental contaminants. PLASTIC WASTE AND ITS MANAGEMENT From 1950 through 2017, the world cumulatively produced 8.3 billion metric tons (BMT) of plastics for use. By 2015, 6.3 BMT of plastics had become waste. Annually, the world generates 2.01 BMT of waste, of which 242 MMT is estimated to be plastic waste. U.S. Plastic Waste Generation The U.S. per person municipal solid waste (MSW) generation rate ranges from 2.04 to 2.72 kg/person/day (4.5–6 lb/person/day), depending on the reference examined. This is 2-8 times the waste generation rates of many countries around the world. While only 4.3% of the world’s population lives in the United States, the nation was the top generator of plastic waste and total waste in 2016, with a total plastic waste at 42 MMT and a per capita plastic waste generation of 130 kg/year. MSW plastic waste generation has been increasing in the United States since 1960, with the fastest increase seen from 1980 to 2000 (Figure S.1). The steep increase in plastic production has been mirrored by an increase in the percent of U.S. plastic solid waste (by mass)—from 0.4% in 1960 to the 12.2% observed in 2018, with a peak of 13.2% in 2017. While both recycling and combustion as plastic waste management techniques expanded in the 1980s and 1990s, the amount of plastic waste managed using these techniques has not expanded relative to the increase in plastic waste, resulting in more plastic waste in landfills (Figure S.2). Designing plastics at the end of onset so that they are able to be appropriately managed at their end of life could address this trend. 2 Prepublication Copy

Summary FIGURE S.1 U.S. annual plastic solid waste generation from 1960 to 2018 in million metric tons. SOURCE: U.S. EPA (2020a). FIGURE S.2 U.S. plastic waste management of municipal solid waste from 1960 to 2018 in million metric tons (MMT) per year. Composted levels are zero during this period. SOURCE: U.S. EPA (2020a). U.S. Contribution to Plastic Waste Leakage Solid waste management systems are important to understanding the difference between managed and mismanaged solid waste. In theory, solid managed waste should not contribute to ocean plastic waste because it is contained either by treatment and/or conversion into other products (recycling, composting, incineration) or contained in an engineered landfill environment. Prepublication Copy 3

Reckoning with the U.S. Role in Global Ocean Plastic Waste In practice, plastic waste still “leaks” from managed systems through blowing out of trash cans, trucks, and other managed scenarios. In addition, waste not put into the solid waste or other management system, whether intentionally or unintentionally, through actions such as illegal dumping, littering, or unregulated disposal or discharge, also “leaks” into the environment. The U.S. Environmental Protection Agency does not monitor or report on any of these sources of leaked plastic waste. Even with an advanced solid waste management system, U.S. plastic waste is estimated to “leak” from MSW at a rate of 1.13–2.24 MMT per year, based on 2016 estimates. This includes domestic leakage as well as mismanagement of exported waste (plastic scrap) by the United States to other countries. Comparing mismanaged plastic waste from other countries, Law et al. (2020) concluded that the United States was the 3rd to 12th largest contributor of plastic waste into the coastal environment with 0.51–1.45 MMT in 2016. Not all waste, or plastic waste, leaks from the waste management system equally. Surveys and community science efforts (at large scales) have shown that plastics make up a large percentage of what ends up in the environment (70–80%), with the majority of plastic items being single-use, including packaging, as well as tobacco-related (e.g., cigarette filters, product packaging, and e-cigarette cartridges) and unidentified fragments sourced from larger items. Conclusion 2: Materials and products could be designed with a demonstrated end-of-life strategy that strives to retain resource value. Conclusion 3: Effective and accessible solid waste management and infrastructure are fundamental for preventing plastic materials from leaking to the environment and becoming ocean plastic waste. Solid waste collection and management are particularly important for coastal and riparian areas where fugitive plastics have shorter and more direct paths to the ocean. Conclusion 4: The United States has a need and opportunity to expand and evolve its historically decentralized municipal solid waste management systems, to improve management while ensuring the system serves communities and regions equitably, efficiently, and economically. Conclusion 5: Although recycling will likely always be a component of the strategy to manage plastic waste, today’s recycling processes and infrastructure are grossly insufficient to manage the diversity, complexity, and quantity of plastic waste in the United States. Recommendation 1: The United States should substantially reduce solid waste generation (absolute and per person) to reduce plastic waste in the environment and the environmental, economic, aesthetic, and health costs of managing waste and litter. PHYSICAL TRANSPORT AND PATHWAYS TO THE OCEAN The ocean is the Earth’s ultimate sink, lying downstream of all activities. Almost any plastic waste on land has the potential to eventually reach the ocean. Major paths of plastics to the ocean are summarized in Figure S.3. These include urban, coastal, and inland stormwater; treated wastewater discharges; atmospheric deposition; direct deposits from boats and ships; beach and shoreline wastes; and transport from inland areas by rivers and streams. 4 Prepublication Copy

Summary FIGURE S.3 Major transport pathways for plastics from land to the ocean. Waterborne Pathways The presumptive largest path of plastic mass from land to the ocean is from rivers and streams moving plastic wastes from inland and coastal areas to the sea. Rain and snowmelt flow over impervious surfaces such as paved streets and parking lots, carrying pollutants, including plastics, either into urban and stormwater systems that discharge to local areas, or directly into rivers, streams, lakes, and coastal waters. Studies conducted in California indicated that the highest rates of plastic waste generation and loading were from industrial, retail, and residential areas, as well as highways and expressways. Urban and suburban sewer flows to wastewater treatment plants are a smaller contributor of plastics to rivers or near shore environments. They carry appreciable quantities of microplastics shed from clothing and other textiles. In wastewater treatment plants, most plastics are removed and concentrated in wastewater sludges that are buried in landfills or spread on land. Other Pathways for Plastic Waste: Wind and Direct Input As with water bodies, plastic items including everyday litter, such as bags and wrappers, large debris mobilized in severe wind storms, and microplastics can be suspended in the Prepublication Copy 5

Reckoning with the U.S. Role in Global Ocean Plastic Waste atmosphere and transported. Plastics also can be directly deposited into the ocean through losses of fishing and aquaculture gear, recreational gear (e.g., during boating or scuba diving), overboard litter, unregulated direct discharge, and cargo lost from ships and barges. Additionally, major storm events, such as hurricanes, floods, or tsunamis, can deposit massive amounts of debris in a relatively short period. Challenge of Estimating Plastics Entering the Ocean Although there is a fair understanding of the major mechanisms that transport plastic wastes to the ocean, it is difficult to make aggregate estimates of plastic fluxes to the ocean. A challenge in assessing paths and quantitative transport of plastics to the ocean is the limited number of quantitative studies and the variety of methods used and data reporting within the scientific community. Conclusion 6: Regular, standardized, and systematic data collection is critical to understanding the extent and patterns of plastic waste inputs to the environment, including the ocean, and how they change in time. DISTRIBUTION AND FATES OF PLASTIC WASTE IN THE OCEAN The input of plastic waste in the ocean, as well as the Laurentian Great Lakes, is a reflection of the amount and type of plastic waste that enters the environment from a diversity of sources as well as the efficiency of the transport of this waste from upstream locations to the ocean and lakes. Its distribution and fate in the ocean are a reflection of transport by ocean currents and surface winds, and the degradation of plastics in the ocean. Plastic waste is found throughout the ocean including on coastlines and in estuaries, in the open ocean water column, on the seafloor, and in marine biota (Figure S.4). FIGURE S.4 Schematic of plastic waste in the ocean and interactions that can occur from land to sea and from surface to seafloor. SOURCE: Law (2017). 6 Prepublication Copy

Summary Plastic Waste on Shorelines and Estuaries Coastlines, including sandy beaches, rocky shorelines, and estuarine and wetland environments, are the recipients of plastic waste that may be generated locally, carried from inland sources, or brought ashore by storms, tides, or other nearshore processes. Items carried ashore may have been locally generated items that were trapped in the coastal zone or items generated elsewhere that were transported long distances. In 2019, more than 32 million individual items were collected and categorized from more than 24,000 miles of beaches around the globe in the International Coastal Cleanup (Ocean Conservancy). The Top 10 list (highest number of items collected) has included the same consumer products year after year, including cigarette filters, food wrappers, beverage bottles and cans, bags, bottle caps, and straws. Regional differences in amounts and trends of coastal debris are driven in part by debris source characteristics such as population size, land use, and degree of fishing activity. The state of Hawaii is particularly well known for suffering a disproportionately heavy marine debris burden, not only from locally based marine litter but also due to the state’s mid-Pacific Ocean location and associated exposure to widely circulated plastic pollution originating throughout the Pacific Rim. Like Hawaii, Alaska coastlines are also a reservoir for significant amounts of plastic debris, which is often characterized by large, buoyant objects such as lines, buoys, and fishing nets. Several major estuaries and inland freshwater waterways in the United States have been surveyed for plastic debris, especially microplastics in the water column or buried in sediments. These studies are widespread geographically—carried out in California, the Pacific Northwest, and along the eastern seaboard from New York to Florida, as well as in regions far from the ocean (Illinois, Montana, Wyoming, Wisconsin, western Virginia). Although a relatively small fraction of estuaries and rivers have been studied, the presence of microplastics in every study indicates that this waste is ubiquitous. Plastic Waste in the Ocean Water Column and on the Seafloor Sampling on the ocean’s surface has allowed scientists to assess the large-scale accumulation of floating debris across ocean basins, which occurs in ocean gyres in both the northern and southern hemispheres. These accumulation zones, commonly referred to as “garbage patches,” are mainly composed of microplastics that have broken apart from larger items, although large floating debris (especially derelict fishing gear, including nets, floats, and buoys) is also found. Contrary to common misperceptions of “garbage patches,” floating plastic debris is not aggregated together in a single large mass in the subtropical gyres and is instead dispersed across an area estimated to be millions of square kilometers in size. Even within the accumulation zones, particle concentrations (measured using plankton nets) can vary by orders of magnitude across spatial scales of tens of kilometers or less. Microplastics, and occasional larger items such as plastic bags, have also been detected in the water column between the surface of the water and the seafloor. Vertical mixing of the water column driven by wind energy can distribute buoyant plastics to depths of tens of meters or greater, and interactions with organic matter and biota may also cause initially buoyant particles to become dense enough to sink. Macroplastics and microplastics have been found in seafloor (benthic) environments around the world. Observed concentrations vary greatly, both in the oceans and Laurentian Great Lakes, suggesting that proximity to sources, movement by water currents, and seafloor topography can act as concentrating mechanisms. Prepublication Copy 7

Reckoning with the U.S. Role in Global Ocean Plastic Waste Impacts on and Distribution by Marine Life Plastic waste has two especially well-studied impacts on marine and freshwater life: entanglement in plastic waste and ingestion-egestion of plastic waste. Ingestion is the taking in or consuming of food or other substances into the mouth or body. Egestion is discharging or voiding undigested food or other material, such as through feces or vomiting. One review by Kuhn and van Franeker (2020) found documented cases of entanglement or ingestion by marine biota in 914 species from 747 studies—701 species having experienced ingestion and 354 species having experienced entanglement. Ingestion of plastic waste occurs at spatial scales ranging from the planktonic ingestion of micro- and nanoplastics to the ingestion of all sizes of plastic debris by whales (Kuhn and van Franeker 2020, Santos, Machovsky-Capuska, and Andrades 2021). Microplastics in particular are ingested by marine biota and may move through the food web, ultimately to humans, but there is limited knowledge of effects throughout the food web and to humans specifically. Entanglement of marine life in ocean plastic waste is harmful or even deadly, and may distribute this pollution via the active or passive movement of living or dead entangled organisms across aquatic habitats, though the frequency and ramifications of this mode of plastic waste distribution and transport are essentially unstudied. In addition to entanglement or ingestion, plastics are also colonized by microbes, and these microbial communities may serve as disease or pollutant vectors. Transformation Two main mechanisms are involved in the transformation and ultimate fate of plastics in the ocean: chemical and physical degradation. Physical degradation involves the breakage of bulk pieces of plastic. Chemical degradation involves the breakage of chemical bonds in the plastic structure and may be accelerated by exposure to ultraviolet radiation, high temperatures, and elevated humidity. Biodegradation of plastics by microbes has been proposed as a third mechanism, but measurable biodegradation (complete carbon utilization by microbes) in the environment has not been observed. Conclusion 7: Without modifications to current practices in the United States and worldwide, plastics will continue to accumulate in the environment, particularly the ocean, with adverse consequences for ecosystems and society. TRACKING AND MONITORING SYSTEMS Documentation of the extent and character of plastic waste and potential sources or hotspots (reservoirs and sinks) informs prevention, management, removal, and cleanup strategies. This report illustrates the limited, or absence of, data from which to inform and implement effective plastic intervention actions. To inform source reduction strategies and policies, a national-scale tracking and monitoring program (or system of systems) is needed that spans the plastic life cycle (i.e., from plastic production to leakage into the ocean). No comprehensive life- cycle tracking and monitoring of ocean plastic waste presently exists. Tracking and monitoring systems currently in place focus on solid waste management inputs and plastic waste items detected in the environment and ocean. Tracking and monitoring plays a critical role in evaluating the effectiveness of any interventions or mitigation actions, such as source reduction strategies or policies. 8 Prepublication Copy

Summary The Role of the National Oceanic and Atmospheric Administration Marine Debris Monitoring and Assessment Project The Marine Debris Monitoring and Assessment Project (MDMAP) is the flagship community science initiative of the National Oceanic and Atmospheric Administration Marine Debris Program that engages partner organizations and volunteers to foster a national shoreline monitoring program in support of research, science-based policies, and prevention efforts. The MDMAP surveys and records the abundance and types of marine debris on shorelines. To date, there are 9,055 surveys at 443 sites that span 21 U.S. states and territories and nine countries. Studies have demonstrated the utility of MDMAP data to estimate marine debris abundance and temporal trends, while also identifying associated limitations in spatial and temporal coverage, site selection, and variability among participants. A key shortcoming is the lack of a comprehensive national baseline for debris densities along the coast that hinders the ability to monitor change in general. Vision for U.S. Marine Debris Tracking and Monitoring A single, national U.S. marine debris (or plastic waste) tracking and monitoring system does not exist, nor does such a system appear to be feasible given the complexity of plastic production, use, and disposal (including leakage) and the diversity of environments through which plastics are transported and distributed. Furthermore, the specific aims of local, regional, national, and international efforts require the application of tracking and monitoring tools and technologies effective at particular spatial and temporal scales. However, the use of multiple, complementary tracking and monitoring systems in a synergistic approach implemented at sufficient spatial and temporal scales would contribute to (1) understanding the scale of the plastic waste problem and (2) identifying priorities for source reduction, management, and cleanup and assessing progress in reducing U.S. contribution to global ocean plastic waste. The following describes tracking and monitoring systems of plastic waste items expected to have the greatest efficacy in ultimately reducing plastic waste inputs to aquatic systems. The specific type or types of plastic waste addressed by any system, including polymer types, associated chemicals, or other characteristics or parameters of interest, will necessarily reflect the aims and drivers of those entities establishing the tracking and monitoring system. ● Tracking and monitoring systems that are scientifically robust, hypothesis-driven, and conceptualized a priori to answer critical knowledge gaps, rather than approaches applied post-hoc to plastic waste tracking and monitoring questions. ● Technologically adaptive tracking and monitoring systems that are able to incorporate and utilize current and emerging technologies to improve the spatial and temporal resolution of mismanaged plastic waste including the application of ○ remote sensing, autonomous underwater/remotely operated vehicles, sensor advances, passive samplers, and others; ○ crowdsourcing apps; ○ barcode tracking for recyclability and traceability; ○ biochemical markers and tracers that provide information on organismal exposure to environmental plastics, including legacy exposure and that which relates to organismal, including human, health; and ○ other current or emergent technologies. Prepublication Copy 9

Reckoning with the U.S. Role in Global Ocean Plastic Waste ● Tracking and monitoring systems that are applied with sufficient spatial and temporal resolution to capture meaningful data concerning knowledge and policy needs. For example, monitoring from a watershed perspective or including pre- and post- intervention tracking and monitoring to assess progress. ● Tracking and monitoring systems that collect data that are comparable and, when scientifically robust, compatible with prior efforts. Examples including using standardized measurement units or experimental design. ● Tracking and monitoring systems that leverage, rather than separate, U.S. federal investment in the reduction of mismanaged plastic waste among government departments and create synergies in the federal response to such waste. ● Tracking and monitoring systems that encompass the full life cycle of plastics, thereby achieving an understanding of the “upstream” plastic waste compartments and associated leakages. Recommendation 2: The National Oceanic and Atmospheric Administration (NOAA) Marine Debris Monitoring and Assessment Project, led by the NOAA Marine Debris Program, should conduct a scientifically designed national marine debris shoreline survey every 5 years using standardized protocols adapted for relevant substrates. The survey should be designed by an ad hoc committee of experts convened by NOAA in consultation with the Interagency Marine Debris Coordinating Committee, including the identification of strategic shoreline monitoring sites. Recommendation 3: Federal agencies with mandates over coastal and inland waters should establish new or enhance existing plastic pollution monitoring programs for environments within their programs and coordinate across agencies, using standard protocols. Features of a coordinated monitoring system include the following: ● Enhanced interagency coordination at the federal level (e.g., the Interagency Marine Debris Coordinating Committee and beyond) to include broader engagement of agencies with mandates that allow them to address environmental plastic waste from a watershed perspective—from inland to coastal and marine environments. ● Increased investment in emerging technologies, including remote sensing, for environmental plastic waste to improve spatial and temporal coverage at local to national scales. This will aid in identifying and monitoring leakage points and accumulation regions, which will guide removal and prevention efforts and enable assessments of trends. PRIORITIZED KNOWLEDGE GAPS The committee identified the following knowledge gaps that impeded the ability to produce a complete assessment of the quantification of the U.S. contribution to global plastic waste requested in the statement of task. Production: Limited access to transparent data on plastic production is a significant barrier to understanding the amounts and trends in quantities and types of plastic resins, a starting point for understanding how much may become waste. 10 Prepublication Copy

Summary Waste Management: There are not many national-scale data sets to understand sources, types, and relative scale of plastic waste generated and disposed or leaked to the environment beyond MSW data in the United States. Transport and Pathways: A comprehensive understanding of the contribution of various transport pathways to plastics in the ocean is hindered by the complexity of the transport processes and the data needed to measure and model variability in fluxes over space and time. Improved understanding of the absolute and relative contributions of each pathway to plastics in the ocean could inform and prioritize actions to reduce the transport of plastics to the ocean. Distribution and Fate: There is insufficient information to create a robust (gross) mass budget for marine plastics and their distribution in ocean reservoirs. In order to improve understanding of distribution and fate of plastics in the ocean, research is needed on the following issues: 1. The rate at which plastics degrade at various depths in the ocean, and how this varies by polymer type. 2. The fate of plastics in marine biota, including residence time, digestive degradation, and egestion and excretion rates. Tracking and Monitoring: Currently, data collected by various monitoring efforts are not well integrated. There would be significant value in developing a data and information portal by which existing and emerging marine debris/aquatic plastic waste data sets could be integrated to provide a more complete picture of the efforts currently tracking plastic pollution across the nation. Such a portal would need to be supported by (1) standardized methods of data collection and (2) support for long-term data infrastructure. The ability to visualize the data contained in the portal would greatly enhance its utility for the public and decision makers to inform and assess the progress of plastic waste reduction efforts. INTERVENTIONS TO REDUCE GLOBAL OCEAN PLASTIC WASTE Despite limitations in complete quantification of plastic waste to the ocean, it is clearly ubiquitous and increasing in magnitude. There is no one solution to reducing the flow of plastic waste to the ocean. However, a suite of actions (or “interventions”) taken across all stages of the path from source to ocean could reduce ocean plastic waste and achieve parallel environmental and social benefits (Figure S.5). Taking systemic action across the plastic life cycle is necessary to avoid the current mismatch between how, and from what sources, plastic products are generated, and the waste and management systems that seek to control or limit the waste they produce. Choices of interventions within a systemic approach can help overcome limitations of each individual intervention. Actions to reduce ocean plastic wastes at each stage have different effectiveness and costs but together could constitute a regional, national, or global strategy for managing plastic wastes in the ocean and the environment. A policy challenge is to organize and implement a portfolio of interventions along this chain of plastic use and management to most effectively reduce or eliminate plastic wastes entering the ocean in light of both benefits and costs. Prepublication Copy 11

Reckoning with the U.S. Role in Global Ocean Plastic Waste FIGURE S.5 Flow diagram of potential plastic waste interventions from plastic production to direct input into the ocean. SOURCE: Modified from Jambeck et al. (2018). U.S. Federal Strategy for Reducing Plastic Waste Although the United States lacks a nationwide systemic strategy for reducing plastic waste at all stages of the plastic waste cycle, many other countries (and some states) have been taking steps to address the plastic waste problem. As of 2018, 127 out of 192 countries regulated plastic bags restricting free retail distribution, and 63 countries mandated extended producer responsibility for single-use plastics, including deposit-refunds, product take-back, and recycling targets. In addition, the European Union, Canada, and China have established systemic national goals and strategies designed around system-wide interventions. The United States could similarly design and implement a coherent portfolio of effective and system-wide interventions by using a strategy and implementation plan that builds on existing efforts and adopts new models. Such a system could provide multiple benefits by (1) creating a clear policy or legal framework for reducing plastic waste in the ocean, (2) creating economic incentives toward reduction through reuse and recycling and away from production, (3) filling “leaks” in the U.S. waste management and pollution control systems, and (4) addressing funding gaps and reversing inequitable cost burdens. Creating a framework for a system of interventions can align the United States with an emerging global approach. Moreover, a U.S. leadership role would help to position the nation to shape and influence global scale requirements around production, formulation, design, innovation, and waste reduction. This, in turn, can create innovation and economic opportunities that also internalize economic externalities and increase societal and environmental well-being. Recommendation 4: The United States should create a coherent, comprehensive, and crosscutting federal research and policy strategy that focuses on identifying, implementing, and assessing equitable and effective interventions across the entire plastic life cycle to reduce U.S. contribution of plastic waste to the environment, including the ocean. This strategy should be developed at a high level with a group of experts (or external advisory body) by December 31, 2022, and its implementation assessed by December 31, 2025. Such a strategy would enhance U.S. leadership in creating solutions to global plastic pollution and shaping modern industrial plastic policy. 12 Prepublication Copy

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An estimated 8 million metric tons (MMT) of plastic waste enters the world's ocean each year - the equivalent of dumping a garbage truck of plastic waste into the ocean every minute. Plastic waste is now found in almost every marine habitat, from the ocean surface to deep sea sediments to the ocean's vast mid-water region, as well as the Great Lakes. This report responds to a request in the bipartisan Save Our Seas 2.0 Act for a scientific synthesis of the role of the United States both in contributing to and responding to global ocean plastic waste.

The United States is a major producer of plastics and in 2016, generated more plastic waste by weight and per capita than any other nation. Although the U.S. solid waste management system is advanced, it is not sufficient to deter leakage into the environment. Reckoning with the U.S. Role in Global Ocean Plastic Waste calls for a national strategy by the end of 2022 to reduce the nation's contribution to global ocean plastic waste at every step - from production to its entry into the environment - including by substantially reducing U.S. solid waste generation. This report also recommends a nationally-coordinated and expanded monitoring system to track plastic pollution in order to understand the scales and sources of U.S. plastic waste, set reduction and management priorities, and measure progress.

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