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

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. F0B7 Large amount of plastic waste enters the environment due to inappropriate disposal. F0B7 Ocean gyres, farmlands, reservoirs, beaches are potential hotspots for plastic wastes. F0B7 Plastics degrade in the environment due to chemical, biological and mechanic processes. F0B7 Physicochemical and mechanical properties alter due to oxidation and chain scission. F0B7 Microplastics are generated as a result of the fragmentation of plastics. Degradation of plastics and formation of microplastics in the environment should be better understood to assess their fate and risks more comprehensively.