Results

KGs related to plastic production

KG 1.1 Sustainable levels of production

Defining sustainable production levels for plastics remains a difficult task due to the complex environmental impacts associated with the feedstock extraction of raw materials and primary plastic production, including air and water emissions that affect frontline communities and nearby ecosystems, greenhouse gas emissions, and plastic losses during production.17,18,19 Data about primary plastic production are opaque; environmental impact databases carry significant uncertainties due to variations in feedstock and processes, and there is no transparent reporting of these activities.20 While global plastic production continues to increase, we lack robust frameworks for determining production thresholds that remain within the carrying capacity of critical Earth systems, as well as a widely accepted reference baseline of impacts associated with production. While defining a sustainable level of production is not solely a scientific task but also requires societal choices about the impacts of a production restriction on both ecosystems and economies; evidence strongly points to the need for reducing production.21,22 This is also recognized by more than 100 states, including the EU member states, that have supported the inclusion of production restrictions in the plastic treaty negotiations, showcasing the political relevance for this type of knowledge. Expanding the knowledge base and valuation procedures for defining sustainable plastic production is necessary for plastic governance to adequately protect our climate and ecosystems.

KG 1.2 Material substitution and problem shifting

As pressure mounts to find alternatives to petrochemical plastics, there is insufficient understanding of when and how substitution leads to unintended consequences or merely shifts environmental burdens, e.g., higher climate impact for specific products and applications, or conflicts over land and water use.23,24,25 Without standardized assessment methodologies for comparing petrochemical plastics to alternatives (e.g., biobased, biodegradable, whether biobased or petrochemical-based, and other substitutes including non-material-based systems and infrastructure) across diverse applications and contexts throughout their life cycle, decision makers lack the evidence base needed for sound material selection policies. While life cycle assessment (LCA), a method intended to evaluate the environmental impact of a product from production to disposal, is expected to play a central role in this process, current LCA methodologies remain underdeveloped.26 Consequently, policymakers risk promoting alternatives that may have worse overall environmental impacts than the plastics they replace.

KG 1.3 Chemical composition

There is limited transparency regarding the chemical composition of plastic products. With thousands of additives used in plastic manufacturing and limited disclosure requirements, critical information about the chemical compounds used in plastic products is not disclosed or available to regulators, recyclers, and citizens.27,28 This lack of transparency is compounded by the presence of non-intentionally added substances (NIAS), which are by-products from manufacturing and degradation, or sorbed during use.29 Because the identity, concentration and formation pathways of NIAS are often unknown and can vary, depending on, for example, manufacturing conditions or product use, they present an additional layer of uncertainty.30,31

This opacity undermines governance efforts aimed at ensuring product safety and enabling greater plastic circularity (cf. hazard and exposure). Without comprehensive knowledge and transparency about plastic composition, policymakers cannot develop targeted regulations for substances of concern, recyclers cannot establish appropriate sorting and processing techniques, and citizens cannot make informed choices. This KG also complicates efforts to establish circular economy systems, as unknown additives and contaminants can render recycled materials unsuitable for high-value applications.

KGs related to plastic use

KG 2.1 Plastic waste prevention efforts

Methods to measure and monitor plastic waste prevention are underdeveloped,32,33,34 which means it is unclear how much plastic waste is avoided through efforts to extend product lifespans, that is, the period a product remains in active use.34 Such efforts include, for instance, reuse, where products are used again for their original purpose as well as repair, which extends the functionality of the product.34 While some EU member states quantify the reuse of selected product groups, there is currently no national monitoring across a broad set of product categories. Moreover, to contribute to waste prevention, reuse should replace the purchase of a new product. However, information on product-specific replacement rates is not available, which means we cannot assume that data on reuse reflect actual waste prevention.32

This KG hinders the institutionalization of policy efforts to prevent plastic waste, as the lack of data inhibits both the assessment of progress and the evaluation of the impact of current waste prevention policies.35 Furthermore, a better understanding of how actual product lifespans compare to the lifetime a manufacturer intends its product to remain functional, the so-called designed lifetime, would be useful to evaluate and prioritize policy interventions aimed at extending product lifespans.34

KG 2.2 Essential plastic use

While plastic use has expanded across all sectors and systems of society, with projections indicating continued and substantial growth in production and consumption,36 there remains no broadly agreed and operationalized framework for assessing the essentiality of plastic use and polymers across different contexts, including for prioritizing uses37 and phasing out of hazardous plastic chemicals.38 Although essential-use approaches have begun to emerge in EU chemicals policy,39,40 important conceptual and implementation gaps remain. A key challenge in this regard is that essentiality is inherently context-specific and time-bound, varying across regions depending on socioeconomic conditions, infrastructure, and the availability of technically and economically feasible alternatives.

In the absence of context-sensitive criteria for assessing essentiality, decision makers in the EU as well as in other regional contexts, lack the necessary guidance to eliminate or reduce risks from non-essential plastics and hazardous plastic chemicals. This further constrains the development of policies that ensure feedstock is allocated to essential uses, such as the transition to green energy and applications essential for healthcare. Moreover, determining essentiality must necessarily be linked to an understanding of the plastic production volumes society can sustainably manage (cf. sustainable levels of production).

KGs related to the end-of-life of plastics

KG 3.1 Plastic waste volumes

EU waste statistics do not fully account for the volume of plastic waste. Plastics ending up as litter is not accounted for, as the plastic is not collected. Data on plastic waste in non-packaging waste streams are lacking or are of lower quality and comprehensiveness, although they represent most of the European plastic consumption.41 Finally, waste composition analyses of residual waste identify additional plastics that are not included in recorded plastic waste volumes.42,43

This incomplete picture results in an overestimation of plastic recycling rates in the EU,44 which hampers assessment of policy progress. Moreover, the limited data on non-packaging plastics hampers investment decisions in future plastic waste management infrastructure by making it difficult to assess what technologies and capacity are needed. For example, without reliable estimates of how much durable plastic from sectors such as electronics or construction enters the waste stream, it is difficult to determine whether investments in specialized sorting or advanced recycling facilities are warranted.41

KG 3.2 Recycling outcomes

In the EU, little data are available on how, when, and where mechanically recycled plastic materials are used, even for the most strictly controlled fraction of PET bottles. In part this KG results from restricted access to verifiable primary industry data. Consequently, it is hard to track the quality of plastic recycling and degradation over multiple recycling stages, as well as whether recycled plastics substitute primary materials.45,46 These partial understandings hamper the assessment of policy impact and progress and make it particularly difficult to assess the human health, climate, and environmental impacts of recycling.

KG 3.3 Chemical recycling

Multiple uncertainties and a lack of research, knowledge, and understanding prevail regarding chemical recycling and the technologies used for it, including their effects on the environment and climate, technical and economic feasibility, and industrial-scale performance and outcomes (proportion of monomers, base chemical products, and fuel).47,48,49 These uncertainties are, in part, linked to a lack of transparency in the chemical recycling sector, where public access to verifiable evidence supporting industry claims of viability remains limited.50,51,52

Consequently, there is sparse knowledge to base regulation on, which is particularly concerning given that public funds are already being spent,53 and investments in these technologies increased almost 10-fold from 2019 to 2023, reaching more than 600 million EUR in the EU.54 In addition, little is known about potential human health implications for workers in chemical recycling facilities, reflecting a broader KG in occupational health in the EU waste sector.55

KG 3.4 Remediation of plastic pollution

Knowledge is missing on the most suitable technologies and methods for the remediation of plastic pollution across different natural environments. Numerous plastic remediation technologies have been developed, some aimed at preventing more plastics from entering aquatic environments, others targeted at cleaning up existing plastics from the environment.56 While a range of plastic remediation technologies exist, their effectiveness, potential unintended consequences, and trade-offs are not well known.57,58,59 Research also questions the scale of impact of current remediation efforts under the ongoing increases in virgin plastic production60 and points to challenges for remediated plastics to re-enter the economy due to low recycling potential and high transportation and energy costs.58 These uncertainties complicate decisions on prioritizing support and investment for remediation efforts. Even with an immediate halt to plastic pollution, existing pollution in ecosystems would remain a major challenge, emphasizing the need to better understand the potential of remediation strategies.

KGs across the plastics life cycle

KG 4.1 Micro(nano)plastics

Microplastics, commonly defined as plastic particles between 1 μm and 5 mm, and nanoplastics, typically considered to be in the size range 1–1000 nm,61 are an emerging concern as the sources and extent of micro(nano)plastic leakage as well as the prevalence and fate of particles remain a significant KG. We lack data on the release of primary and secondary (formed via fragmentation, mechanical abrasion, heat/UV irradiation, etc.) micro(nano)plastics during all stages of the plastic life cycle. Current research highlights significant contributions from sources, including pellets (early in the life cycle, pre-product manufacturing) or fibers during production, shedding during use (textiles, car tyres, packaging, and paint) and later during recycling or end-of-life, but no consolidated overview exists. Although larger-size microplastics are more extensively documented, understanding across the full-size range is still limited.62,63,64 In addition to these source-related uncertainties, major gaps remain regarding the prevalence and fate of micro(nano)plastics in the ecosystems they end up in.65,66

Without better knowledge of micro(nano)plastic sources, as well as their prevalence and fate, interventions to minimize leakage and assess exposure to hazardous substances are unlikely to be effective (cf.hazard and exposure). The recently approved EU regulation on preventing plastic pellet losses illustrates how scientific knowledge on microplastic pollution can directly inform targeted policy measures. In this case, the regulation is explicitly motivated by evidence showing that “plastic pellet losses constitute the third largest source of microplastics unintentionally released to the environment in the Union”.67 This illustrates how identifying, in this case sources, can support the motivation for targeted policy.

KG 4.2 Hazard and exposure

There is a considerable KG related to the hazard of, and exposure to plastic chemicals and particles for humans and the environment, which impedes the ability to assess and manage the risk of plastics. A substantial portion of plastic chemicals lack hazard information,68,69 meaning it is currently unknown whether many chemicals present in plastics have the intrinsic potential to cause harm to human health or the environment.70 Furthermore, interactions among chemical additives in plastics are unknown in most cases, so potential cocktail effects are not adequately accounted for in current hazard and exposure assessments.71

This KG is linked to methodological challenges. For example, for plastic particles72 methodologies for identifying and quantifying nanoplastics remain insufficiently developed,72,73 and existing toxicity tests, developed for soluble chemicals, are not necessarily well-suited to assess particle toxicity.74 Similarly, robust data on exposure to plastic chemicals, which take mixture toxicity and NIAS into account, are not available and difficult to collect.75,76

This KG hinders the development of science-based safety thresholds, leaving uncertainty around acceptable levels of exposure to plastic chemicals and particles for both humans and the environment. The lack of knowledge is compounded for recycled plastics because the source material is heterogeneous and not easily determined.31,77,78 Related uncertainties also remain regarding how repeated use and material degradation in reuse systems may influence chemical exposure over time.31,79 Together, these KGs hamper the ability to make informed decisions about the appropriate use of circular plastic applications, which is particularly alarming considering the strong policy push in the EU to increase plastic circularity, noticeably through achieving higher recycling rates.15

KG 4.3 Plastic trade flows

A significant KG exists regarding the movement of plastics that remain within the economic system. The main challenge in understanding plastic trade flows is capturing the full spectrum of plastic materials and their life cycle stages in official statistics.80,81 Upstream, global primary plastic trade is estimated at over 1 trillion USD annually.82 However, this figure still underestimates the full scale of the global plastic trade due to “hidden” plastics embedded in various products and packaging such as electronics and textiles.

Downstream, multiple challenges co-exist that prevent reliable data on plastic waste flows. First, while trade statistics like UN COMTRADE offer insight into the legal trade of waste plastics,83 underreporting again follows from failure to capture plastics in other traded waste products.43,84 Second, illegal plastic exports are significant, with estimates suggesting that 15%–30% of EU waste trade involves illegal shipment.85 Third, plastic waste exported for recycling is frequently mismanaged and may end up in the environment.86

Without reliable data on the quantity, composition, and destination of traded plastics and plastic-containing products, governments struggle to enforce existing trade regulations, prevent illegal exports, and ensure environmentally sound management of plastic waste. Incomplete information on plastic trade flows also undermines the ability to assess the effectiveness of policy instruments such as export bans and waste shipment regulations. Moreover, the lack of transparency around hidden plastics in traded goods complicates efforts to allocate responsibility for plastic pollution along global value chains, which in turn weakens accountability.

KG 4.4 Social cost of plastics

Social costs broadly refer to the total impact of an activity on societal welfare, combining direct expenses, productivity losses, health impacts, environmental degradation, and other external costs shifted onto the public.87 Little research quantifies the full social cost of plastics. Plastics play an important role in most sectors and systems of production and consumption, making it highly challenging to calculate aggregated social costs. Some studies calculate the benefits of reduced, or the costs of increased, plastic pollution,88,89 but no standard methodologies exist.90 Some estimates quantify the economic consequences of plastic pollution on activities like fishing, tourism, and shipping.91 However, these estimates overlook values of people and places burdened by pollution (e.g., human life, human health, aesthetic values, cultural or religious significance, and recreational value), including variation across geographies and population groups.80,91,92 On top of these social costs, should be added the costs of current fossil fuel subsidies to plastic production. While estimates demonstrate that subsidies are substantial,93 it is highly complicated to assess the overall level of subsidies for fossil-based plastics and consolidated data are unavailable.91

Without robust and comprehensive estimates of the social costs of plastic pollution, governments lack the evidence base needed to justify and design effective policy instruments and regulatory interventions. The absence of standardized methodologies also limits the comparability of assessments across countries and over time, potentially reducing the political feasibility of ambitious preventive measures. As a result, the true societal benefits of immediate action may be underestimated, leading to delayed interventions and potentially higher long-term social costs.