Vehicle-Road Wear Microplastics: Fragmented Understanding of Their Impacts on Environment

Vehicle-road wear microplastics (VRWMPs) are microplastic-sized polymer-containing particles generated from the vehicle-road system, including tire-road wear particles (TRWPs) as the dominant composite class and other polymer-bearing wear debris (e.g., road marking wear). Their complex chemical composition and wide particle size distribution pose potential ecological risks. However, their impacts on ecosystems have long been overlooked because overlapping terminology (e.g., TRWP versus broader non-exhaust emissions) and nonstandardized characterization methods hinder cross-study comparability, while a tire-centered research focus and limited field monitoring obscure the contribution of pavement materials and realistic exposure scenarios. Existing studies largely emphasize tire-derived contributions, while the role of pavement materials remains underrepresented, resulting in an incomplete understanding of VRWMP formation mechanisms. In addition, limited long-term and systematic monitoring data constrain current knowledge of VRWMP migration, transformation, and environmental risks. From a road engineering perspective, this review synthesizes the full lifecycle of VRWMP, from generation to environmental fate. It focuses on formation mechanisms, preparation and characterization methods, migration, and transformation processes within roadway systems, and associated ecological and human health effects. Evidence indicates that VRWMP generation is jointly controlled by tire characteristics and pavement materials, yet a standardized characterization framework is still lacking. The migration and transformation of VRWMP are difficult to model due to data scarcity and pronounced regional variability related to geography, climate, and traffic conditions. Soil and aquatic environments represent major sinks, and exposure pathways such as inhalation may induce adverse biological effects, including oxidative stress and DNA damage. With the increasing complexity of pavement materials, establishing full-chain control of VRWMP, from generation to environmental fate, is becoming an urgent research priority. This review provides a scientific basis for advancing cleaner and more sustainable transportation infrastructure.