Material flow analysis of chemical additives in plastics: A critical review

The exponential growth in plastic production and usage has escalated global concerns about plastic pollution, particularly regarding harmful chemical additives. Understanding the anthropogenic cycles of these additives is the prerequisite to developing effective strategies for plastic pollution control and a toxics-free circular economy. Here we analyze 269 anthropogenic cycles of plastic additives by reviewing 42 extant academic articles to identify research gaps and needs. Based on their characteristics and the available knowledge, we classify these plastic additives into five research priority levels, with 3,116 designated as "urgent level", further subgrouped into 17, 14, and 20 additive categories considering their functions, polymer types, and application sectors, respectively, to inform future investigations. Four key research gaps are highlighted: limited research coverage for hazardous chemical additives, lack of specificity to plastic products, incomplete consideration of life cycle stages and relevant flows, and insufficient attention to policy implications. To close these gaps, we recommend expanding the scope of plastic additives with a specific focus on urgent-level cases, exploring all chemical flows tailored to various plastic types, enhancing the quality and accessibility of relevant data, and fostering a mechanism for strong science-policy-society interactions on the management of plastic additives. This review offers a roadmap for advancing research on material flow analysis of plastic additives and sustainable plastic management.