“Plastic” is not a single material. It refers to thousands of different formulations created for different purposes. A squeezable shampoo bottle, a robust phone case, a resistant component of heavy industrial equipment or an insulating cable coating all depend on a carefully selected mix of chemicals, including polymers. These chemical choices influence durability, flexibility, transparency, colour, temperature resistance and many other key performance attributes. They also shape the chemical impacts plastics pose across their lifecycle, from production to disposal, including potential effects on human health and the environment.

At the design phase, the focus is often on product functionality and properties. Yet the chemicals that deliver these properties are not always examined as closely. Considering chemical choices early in the design process can help reduce health and environmental impacts across a product’s lifecycle. The report A Chemicals Perspective on Designing with Sustainable Plastics shows how applying a “chemicals lens” during material selection and conceptualisation allows designers and engineers to make more informed chemical-selection decisions, leading to safer and more sustainable products. As with any systems approach, there are trade-offs and challenges involved in considering multiple attributes. However, considering chemical selection choices early on helps ensure that material choices are made more deliberately and transparently.

Relationship between system, product, materials and a chemicals perspective. The chemicals perspective is interconnected with design decisions made at a system, product and material level.

As countries work to increase plastic recycling, an important question emerges: how well do we understand which chemicals are present in these recycled materials? Plastics contain many different substances, which makes it difficult to fully understand their composition even when they are new. As plastics move through use, disposal and recycling, tracing these substances becomes even more challenging. As a result, there can be uncertainty about which chemicals remain in recycled plastics and whether they may pose risks when the material is reused in new products. A new OECD report on Chemical content validation of recycled plastics reviews chemical considerations across standards, certifications and quality control measures for recycled plastics. It also examines analytical techniques used to characterise the chemical content of secondary materials. The report reveals several insights:

• Chemical information is often incomplete or lost across value chains, particularly in open-loop recycling systems where materials are recycled into products different from their original application.
• Existing standards and certifications address material traceability and recycled content but generally do not require chemical content analysis, limiting the ability to ensure chemical safety.
• No single technique can detect all chemicals of interest in recycled plastics. Recyclers rely on combinations of targeted and non-targeted methods to characterise chemical composition.
• A more integrated approach that combines harmonised international standards, robust analytical methods, chemical traceability systems, economic incentives and research collaboration can strengthen global capacity to validate chemical safety while increasing recycling rates.

These findings mainly relate to mechanical recycling, which remains the most common method used today. Chemical recycling, which breaks plastics down into their basic building blocks, may offer advantages for removing contaminants, but it is still deployed on a much smaller scale and comes with its own sustainability challenges.

Chemical selection considerations influence impacts across life cycle stages

For more than 50 years, the OECD has been working with countries and stakeholders to strengthen chemical management and to support the harmonisation of regulatory frameworks. Many tools and approaches developed for chemical assessment and risk management can be used in the context of plastics as summarised in this brochure. Highlights include:

• Setting common definitions supports a common basis for regulation

Polymers are molecules made of repeating building blocks, known as monomers. Most plastics are made from synthetic polymers, combined with other chemicals to give them the characteristics needed for specific products. The OECD definition of polymer, established in the early 1990s, has helped provide a common basis for chemical legislation in many countries. Building on this definition, the OECD has facilitated discussions on criteria for decision-making regarding low concern for polymers. While final criteria were not agreed, several countries implemented criteria for reduced regulatory requirements for some polymers that fit within their regulatory systems.

• Standards for testing chemicals including polymers help countries generate reliable and comparable data

The OECD continues to develop harmonised standards for testing of chemicals in a regulatory context. Information obtained from studies following OECD Test Guidelines is used for assessing how chemicals may affect human health and the environment, including those chemicals and polymers that make up plastics. 

• Supporting the shift to proactive selection of safer and more sustainable chemicals

Designing safer and more sustainable plastics also means choosing chemicals that minimise potential risks. OECD work on alternatives assessment, substitution and sustainable chemistry helps governments and industry identify safer options and advances proactive risk management. The Safe(r) and Sustainable Innovation Approach (SSIA) for nano-enabled, emerging and advanced materials proposes a systematic and comprehensive approach that considers sustainability aspects hand in hand with safety considerations very early on at the material design stage.