A Physicochemical and Source-Based Perspective on Microplastic Risks in Aquatic Systems

Recommendations P lastics are ubiquitous in modern life and contribute to widespread environmental contamination.Microplastics (MPs), defined as plastic particles smaller than 5 mm, have emerged as pollutants of growing concern, and have been detected in marine and freshwater environments, soils, and the atmosphere. 1 Microplastics (MPs) in aquatic systems originate from multiple sources, including primary MPs intentionally produced at the microscale and secondary MPs generated by the fragmentation of larger plastic debris via physical, chemical, and biological processes.2 Despite extensive research on MP occurrence and ecological effects, the revailing classification of primary and secondary MPs is still based largely on their sources.This source-focused framework can obscure key physicochemical attributes, including particle size, shape, polymer composition, surface chemistry, and transformation pathways, that govern fate and transport, contaminant sorption, and biological interactions.Therefore, definitions based on sources alone are insufficient for robust ecological and human health risk assessment.MPs are physicochemical materials whose properties, including size, morphology, density, and surface functionality, influence buoyancy, transport and fate, interactions with cooccurring contaminants, and persistence in aquatic systems.For