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Understanding plastic degradation and microplastic formation in the environment: A review

Environmental Pollution 2021 1378 citations ? Citation count from OpenAlex, updated daily. May differ slightly from the publisher's own count.
Kai Zhang, Amir Hossein Hamidian, Aleksandra Tubić, Yu Zhang, James Kar‐Hei Fang, Chenxi Wu, Paul K.S. Lam

Summary

This review covers how plastics break down in the environment through sunlight, heat, water, and microbial action to form microplastics smaller than 5 millimeters. The process depends on both the type of plastic and environmental conditions, but knowledge about real-world degradation rates and pathways is still limited. Understanding how microplastics form is essential for predicting where they accumulate and how they might enter the food chain and drinking water.

Plastic waste are introduced into the environment inevitably and their exposure in the environment causes deterioration in mechanical and physicochemical properties and leads to the formation of plastic fragments, which are considered as microplastics when their size is < 5 mm. In recent years, microplastic pollution has been reported in all kinds of environments worldwide and is considered a potential threat to the health of ecosystems and humans. However, knowledge on the environmental degradation of plastics and the formation of microplastics is still limited. In this review, potential hotspots for the accumulation of plastic waste were identified, major mechanisms and characterization methods of plastic degradation were summarized, and studies on the environmental degradation of plastics were evaluated. Future research works should further identify the key environmental parameters and properties of plastics affecting the degradation in order to predict the fate of plastics in different environments and facilitate the development of technologies for reducing plastic pollution. Formation and degradation of microplastics, including nanoplastics, should receive more research attention to assess their fate and ecological risks in the environment more comprehensively.

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