Insights from Life Cycle Assessment to Inform Chemical Substitution, Alternatives Assessment and Safe and Sustainable-by-Design.

Designing chemicals and pharmaceuticals with optimal properties yet minimal negative effects on humans and the environment remains challenging. Chemical substitution enables us to address this challenge but requires significant methodological advancements and testing to become mature and more widely adopted worldwide. We use insights from life cycle assessment (LCA) to explore and synthesize synergies for advancing substitution approaches, including alternatives assessment and comparative safe and sustainable-by-design (SSbD). We screen boundary conditions for LCA and substitution and use an illustrative case study on comparing two sets of pest control options to discuss learnings for addressing challenges toward a mature chemical substitution field. For some aspects, LCA provides strong inspiration to inform developments of substitution approaches, such as using a common functional comparison basis, aligning assessment metrics and units, and considering full life cycles to avoid burden shifting. For other aspects, LCA is less informative and substitution requires additional developments. This includes systematic overviews of possible context-specific alternatives, mapping of chemical, material, and other functions, more detailed life cycle inventories, and rapid-screening assessment methods. Combining learnings from LCA with ways to address remaining challenges will help advance chemical substitution to support the objectives of UNEP's Global Framework on Chemicals and other policy instruments for a broader, much needed sustainability transition.