This model builds on previous stock and flow models presented in Breaking the Plastic Wave, ReShaping Plastics and Achieving Circularity. In particular, the model expands on Towards Ending Plastic Pollution by 2040, which quantified a Global Rules Scenario (GRS) encompassing 15 policy interventions for the instrument across all main economic sectors and plastic applications. The Global Full Lifecycle Scenario described in this report is the same as the Global Rules Scenario described in Towards Ending Plastic Pollution by 2040.

The model incorporates the following innovations and additions:

• modelling of four different scenarios for the instrument;
• in-depth regional analysis, encompassing nine regions;
• a new ‘upstream’ module that includes flows of the six largest groups of primary plastic polymers from production to conversion;
• an assessment of economic activity across the value chain; and
• the Scenario Explorer online tool, which allows stakeholders to see the impact of making different high-level assumptions.

The model also helped inform the report ‘The Plastic Pollution Fee: Closing the financing gap for implementing an ambitious global plastics treaty‘ (forthcoming) by the Minderoo Foundation outlining potential design options for a Plastic Pollution Fee that serves as an innovative funding mechanism.

We would also like to acknowledge the modelling efforts conducted by others, including the Organisation for Economic Co-operation and Development, the Universities of California Berkeley and Santa Barbara, the Pew Charitable Trusts and the World Bank. Given the importance and complexity of modelling the global plastics system, it is encouraging to see differing approaches resulting in significant alignment in terms of the scale and nature of the policy interventions required.

The model includes all main economic sectors and plastic applications across nine regions:

Sector and geographic scope of modelling

The economic case for action becomes even stronger when the costs of externalities are considered. The modelling for this report does not include the environmental and social externality costs related to plastic pollution, such as the costs of dealing with legacy plastics; the human and ecological impacts of chemicals (see Box 4); the social cost of GHG emissions; and the impact of mismanaged plastics on different industries (eg, fisheries, tourism, infrastructure). While they are complex to quantify and the scientific understanding is still evolving, it is clear that these externality costs are significant. For example, studies of the health impacts of plastic pollution point towards potential annual costs in the hundreds of billions in the United States alone. As these estimates are based on a limited subset of plastic chemicals and the associated health impacts, they likely understate the total health costs of these chemicals – let alone those ensuing from all plastic-related chemical exposures. These figures do not include other externality costs – such as the health impact of air pollution through open burning of waste, which disproportionately affects LMICs, or the contribution of plastics to climate change – and may thus underestimate the full economic losses resulting from the negative effects of plastics on human health and the environment.

The scenarios vary in terms of the funding mechanisms they envisage. The Global Full Lifecycle Scenario assumes the global adoption of EPR schemes and the imposition of national/regional fees on primary polymer production as part of a wider package of policies. However, due to their national/regional nature, these schemes do not allow for funds to be channelled to the regions where they are needed most. Instead, the measures encompassed in this scenario will result in a financial surplus – even once all waste management (ie, not just for plastics) has been funded and 30% of the revenues generated have been invested in de-risking circular economy solutions. By contrast, a similarly designed fee assumed under the National Full Lifecycle Scenariog will fall far short of generating the funds needed to close the waste management gap outlined above.

Chemicals and polymers of concern

Overall, more than 16,000 chemicals are potentially used or present in plastic materials and products. Over 4,200 of these are chemicals of concern due to their hazardous properties. Critically, hazard information is lacking for over 10,000 chemicals. Hazardous properties in this context include associated effects such as cancer risks, mutagenicity, reproductive toxicity, endocrine disruption and ecotoxicity to aquatic organisms, impacting human health, ecosystems and biodiversity. Yet only 128 of these chemicals are regulated internationally.

There is an urgent need to tackle the use of chemicals that have the potential to cause human and environmental harm. The Scientists’ Coalition for an Effective Plastic Treaty and the recent State of the Science on Plastic Chemicals report outline the relevant issues and how the instrument can address them. Recommendations include comprehensive and efficient regulation of plastic chemicals – for example, by grouping chemicals based on their structure to simplify categorisation and hazard-based prioritisation while avoiding regrettable substitutions (eg, to less well-studied chemicals presenting similar hazards). Another critical step will be to dramatically increase transparency (‘no data, no market’), to ensure that essential information about plastic chemicals is publicly available (eg, through a global inventory and comprehensive definitions). Measures such as negative lists of chemicals based on recognised hazard criteria and positive lists of chemicals that comply with hazard and safe-by-design criteria could be used to promote the redesign and simplification of plastics and the transition to a non-toxic plastic economy. Policies to increase capacity to effectively manage plastic chemicals and innovate for safer and sustainable plastics (eg, through knowledge sharing and cooperation) will also be needed. Similarly, various reports have called for the creation of a strong science-policy interface as part of the instrument (eg, through a subsidiary scientific body) to facilitate the regular, independent and evidence-based refinement of assessment criteria. Similar measures may also be needed for other material types, to guard against undesirable substitutions.

Plastic production

Virtually all plastic is made from fossil fuels such as crude oil, natural gas and coal. The environmental concerns associated with these industries are thus closely linked to plastic production – for example, negative impacts on workers exposed to hazardous substances; and on ecosystems and biodiversity through the contamination of water from fossil fuel extraction and spillage and the release of toxins during production. There is also evidence that production facilities expose surrounding communities to hazardous substances and cause adverse health effects.

Plastic use

Consumers are constantly exposed to plastics and plastic-associated chemicals. For example, of 419 chemicals found in plastic children’s toys, 126 were identified as of potential concern; while over 1,000 chemicals have been found to have migrated into food.

Mechanical recycling

Studies underline the need for further research on the possible negative impacts of mechanical recycling on human health, ecosystems and biodiversity, including the risk of reintroducing chemicals of concern as unwanted contaminants during the sorting and recycling process26 These studies indicate that informal workers are especially vulnerable to health impacts through unprotected exposure to heated plastics, plastic dust and fine particles, and to chemical pollution in the air. Finally, a recent study has indicated that recycling facilities – especially at the washing stage – can end up releasing microplastics into wastewater systems which, without filtration and controlled disposal, can then make their way into oceans and waterways.

Chemical recycling

Two main concerns have been raised regarding the potential negative impact of chemical recycling on human health. First, the emissions and discharge from chemical recycling processes contain hazardous chemicals, which may impact on nearby communities and environment; and second, substances of concern from feedstock waste can be reintroduced into output recyclates. Further research on both issues is needed.

Incineration

Historically, there is evidence that incinerators contribute to environmental impacts due to inadequate emission controls. This can result in the release of pollutants (eg, dioxins, furans, polycyclic aromatic hydrocarbons and particulate air pollutants) linked to a range of adverse health effects. Well-managed incinerators can minimise emissions by controlling combustion temperature, input composition, material flow speeds and gas flow cleaning; but this requires extensive management, which can be problematic in regions with limited resources or regulation.

Open burning

One self-management strategy which is frequently adopted by the roughly 2 billion people worldwide who lack formal waste collection services is to burn discarded plastic on open, uncontrolled fires. This contributes significantly to GHG emissions and the release of particulate matter, reactive trace gases and toxic compounds. These pose significant health risks, with waste pickers who lack safe workplaces and protective equipment most at risk.

Landfill

Sanitary landfill standards vary and many countries have struggled to implement globally accepted standards, leading to post-landfill leakage of materials and leachates containing pollutants and microplastics. Measures including landfill liners can mitigate this risk somewhat. However, while macroplastics are unlikely to breach landfill liners, microplastics may pass through them; and even modern sanitary landfills present a risk of leachate contaminating groundwater. The long-term stability of landfill liners is unknown, but they are unlikely to function fully beyond 100 or 200 years.

Plastic alternatives and substitutes

As plastic alternatives are not without risk, a case-by-case analysis to prevent unintended consequences of substitution will be required in each context. As best practice, product lifecycle assessments (LCAs) should be conducted to measure the overall environmental, health and social impacts. This is also the case for safe reuse and refill models, and food contact materials that may go through multiple use cycles. Transparency on the types of substances used in plastic alternatives and their potential toxicological properties should also be considered (see note on ‘Chemicals and polymers of concern’ above).

Microplastics

Microplastics present a significant potential health risk without established safety thresholds, and have reportedly been detected in human placentas, blood, expressed breast milk, lungs and the plaques that block blood vessels in cardiovascular disease. Although the precise impact of this exposure remains unclear, the evidence calls for further examination of the potential threats that microplastics pose to human health. Ingested microplastics have been shown in vitro, in diverse human cells in culture, and in vivo, in diverse model organisms, to induce alterations in gene and protein expression, inflammation, disrupted feeding behaviour, growth inhibition, modifications in brain development and impaired filtration and respiration rates. Studies also suggest that nanoplastics may pose greater hazards than microplastics due to their higher likelihood of translocating beyond the gastrointestinal tract and acting as transmitters for chemical contaminants

Ecosystems and biodiversity

Extensive accumulation of plastic in the oceans and on land poses threats to ecosystems and biodiversity.  Marine plastic pollution is reported to negatively affect over 800 species. From coral reefs to deep sea trenches and from remote islands to the Poles, plastic alters habitats, harms wildlife and can damage ecosystem functions and services. Macroplastic waste in the environment can lead to fatalities, injuries and indirect harm such as malnutrition through ingestion or entanglement. Microplastics have been forecast to cause pervasive ecological damage if current or increased levels of release into the environment persist. Plastic-associated chemicals are known to bioaccumulate and biomagnify in marine food webs, while bioaccumulation of micro and nano-plastics has been demonstrated in some studies. Microplastics and the chemicals they contain can also move up the food chain.