Beyond Microplastics: How Tire Wear Particles Influence Plant Performance

Tire wear particles (TWPs), a major source of microplastic pollution, are mainly released in soils. TWPs are rubber-mineral composites that release evolving mixtures of metals, polycyclic aromatic hydrocarbons, and reactive additives and transformation products (e.g., N-(1,3-dimethylbutyl)-N-phenyl-p-phenylenediamine-quinone). Unlike polymer-based microplastics, both TWP particle properties and leachate composition change with aging, potentially causing nonlinear toxic effects on ecosystems. Though TWPs are ubiquitous in terrestrial environments, their impacts on plant performance cannot be extrapolated from polymer-focused microplastic research. Here, we synthesize emerging evidence and propose a plant-centric, eco-evolutionary framework to explain how TWPs influence plants through soil-rhizosphere pathways. We emphasize three connected paradigms: (i) disentangling particle-driven physical effects on soil structure and root habitats from leachate-mediated chemical stress; (ii) integrating plant physiology, soil biogeochemistry, and pollutant chemistry to capture rhizosphere "hotspots" and microfood-web responses; and (iii) linking mechanistic understanding to exposure modeling, risk assessment, and policy. We organize TWP impacts as an inputs-processes-outputs chain, where dynamic exposure inputs (particle traits, mixtures, aging state, root-particle contact, etc.) regulate processes (chemical mobilization, microenvironment change, biotic interactions, etc.) and shape plant performance and plant-soil feedbacks. We propose testable hypotheses, including that weathering shifts dominant impacts from particle to leachate pathways and that root-particle interfaces create localized exposure gradients that restructure nutrient coupling and plant-microbe interactions. Finally, we outline research priorities such as aging-dependent and long-term assessments and interactions with co-occurring pollutants and global-change drivers to accelerate predictive understanding of TWP risks to soil-plant systems.