Microplastics and tire wear particles in aquatic environment: A comparative review on generation, characteristics and environmental behavior

Tire wear particles (TWPs), produced by friction between tire tread and road surface, are one of the largest sources of microplastics (MPs). TWPs and conventional MPs both pose potential threats to the aquatic ecosystems and attract substantial interest. However, current reviews predominantly concentrate on conventional MPs, overlooking the critical distinctions or connections between MPs and TWPs. Here we review the contrasts between the physicochemical properties and environmental behavior of MPs and TWPs. It provides a comprehensive summary of commonly employed laboratory characterization methods for these particles, alongside an analysis of disparities in detection methodologies. Furthermore, the review delves into discrepancies between MPs and TWPs with respect to aging processes, toxic substance leaching, pollutant adsorption/desorption behavior. The diverse environmental factors and their underlying influencing mechanisms are also reviewed in detail. It is evidenced that TWPs exhibits special characteristics in the risks of all MPs types. Fortunately, most of the methodologies for both MPs and TWPs can be referenced or can be mutually optimized. We call for greater attention to the special challenges posed by TWPs and advocate for the establishment of a comprehensive methodological framework based on the well-developed research system for MPs.