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Formation and Transformation of Micro(nano)plastics: Mechanisms and Environmental Health Implications.

Environment & health (Washington, D.C.) 2026

Summary

This review pulls together existing research showing that most microplastics we encounter in the environment aren't fresh, pristine particles—they've been broken down and chemically altered by sunlight, heat, weathering, and even bacteria, which changes how easily they can enter our bodies and how harmful they might be. This matters because the tiniest fragments (nanoplastics) created through this breakdown process may be more reactive and easier for our bodies to absorb, yet we still lack good tools to detect and study them. The authors argue that understanding how plastics degrade and transform—not just where they come from—is essential for accurately assessing health risks and developing better

Micro-(nano)-plastics (MNPs; <5 mm plastic particles including nanoscale fractions) are increasingly recognized as pervasive environmental pollutants, with risks arising not only from their original emission sources but also from ongoing transformations. This review systematically integrates current evidence on the formation and transformation of MNPs under mechanical, photochemical, thermal, oxidative, and biological processes, highlighting that environmental MNPs are predominantly aged rather than pristine particles. Aging significantly reshapes particle shape, size, surface chemistry, and reactivity, thereby altering mobility, persistence, and interactions with copollutants, biota, and humans. By adopting a sourcetransformationexposurerisk framework, this review clarifies the critical importance of understanding transformation pathways for tracing pollution origins, revealing exposure routes and doses, and improving health risk assessment. Particular attention is directed toward nanoplastics, whose elevated reactivity and bioavailability remain poorly understood due to analytical limitations. Strategic research priorities are identified, including the development of multifactorial aging simulation models, advanced detection and characterization techniques, and lifecycle-oriented mitigation strategies. This work advances a forward-looking perspective that connects mechanistic understanding with risk governance, providing a scientific foundation for more accurate prediction, monitoring, and control of MNP pollution.

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