Chemicals and Polymers of Concern – a Plastic Treaty Priority

Anatomy of plastics – overview of key components in plastics.
Image credit: United Nations Environment Programme

One of the proposed core objectives of the international plastic treaty is “banning, phasing out, and/or reducing the production, consumption, and use of chemicals and polymers of concern” found in plastics. A recent United Nations technical webinar addressed this issue as a preliminary to the next round of treaty negotiations in November 2023.

The International Panel on Chemical Pollution (IPCP) provided a framework for understanding the problem. The framework was derived from the United Nations Environment Programme's (UNEP) recent publication, Chemicals in Plastic: A Technical Report.

Chemicals are an integral part of plastics. According to the UNEP report more than 13,000 substances have been associated with plastics. 7,000 of these have been analyzed. More than 3,200 are of potential concern. The Research Council of Norway has identified even more chemicals in plastic: 16,000, 25% of which have been classified as hazardous. In addition, no plastic chemical has been classified as safe. The Council has created a framework to prioritize chemicals relative to their safety and anticipates publishing a state-of-the-art science report in January 2024.

Chemicals in plastic can be lumped into four categories:

1. Monomers and polymers – the main building blocks of plastic materials.
2. Additives – which bring desired functionality to the plastic material.
3. Other intentionally added substances – such as starting materials and catalysts.
4. Non-intentionally added substances – such as solvents, cleaning agents, or impurities from manufacturing or recycling.

Ten groups of chemicals are of concern due to their hazardous properties, according to the IPCP. Additives are of particular concern since they are typically not bound to the polymer and, therefore, are released from plastic over time, leading to ecosystem and human exposures. They are categorized into another group of four:

1. Plasticizers – to make plastic softer and flexible.
2. Fillers – that occupy space without changing functional properties.
3. Flame retardants – to reduce flammability and prevent the spread of fire.
4. Other – including colorants, antioxidants, heat and light stabilizers, lubricants, biocides, or antistatic agents.

Human exposure to chemicals in plastics.
Image credit: United Nations Environment Programme

Plastic chemicals impact human health and the environment

Chemicals of concern in plastics impact human health and the environment. Women and children are particularly susceptible. Chemicals reach humans through inhalation of contaminated air, ingestion of contaminated food, water, and dust, and dermal contact.

Humans are exposed to chemicals in plastic in everyday plastic products such as food contact materials, electronics, textiles, clothing, personal care and household products, children’s toys, clothing, or furniture, and through occupational exposure.

Examples of adverse health effects from chemicals in plastic include abnormal hormone functions, reduced fertility, a damaged nervous system, hypertension/cardiovascular disease, and lung and liver cancer.

Hazardous chemicals can be released all along the plastic life cycle, finding their way into air, water, and soil. They are released during extraction and processing of raw materials, plastic production, plastic product manufacturing, use of plastic products, recycling, and disposal. Open burning of plastic waste releases toxic chemicals such as dioxins and furans.

The above summary provides a simple view of the challenges of chemicals in plastic which is necessary to fulfill the core objective of the plastic treaty in regard to these chemicals.

The plastic treaty mandate to address chemicals of concern looks to existing international agreements that can serve as models according to the Secretariat of the Basel, Rotterdam, and Stockholm conventions. The Montreal Protocol addresses ozone-depleting substances, the Basel Convention focuses on hazardous wastes and control of transboundary movements, the Stockholm Convention controls production use, import/exports, and unintentional releases of persistent organic pollutants, and the Rotterdam Convention has a review process for 55 hazardous chemicals to protect human health and the environment. These models will hopefully be helpful in crafting the elements of the plastic treaty addressing chemicals of concern.