Tire wear particles in aquatic environments: From biota to ecosystem impacts.

Tire wear particles (TWPs), mainly generated through friction between tires and road surfaces, represent a major source of traffic-related microplastic pollution, posing threats to biota and ecosystem functions. These particles are a complex mixture of toxic compounds, including heavy metals (e.g., zinc) and organic compounds (e.g., 6-PPD), and their diverse leachates exacerbate their ecological impacts. This review collates current knowledge on the occurrence of TWPs and their leachates in aquatic systems, emphasizing their toxicological effects on species and cascading ecological consequences at the community and ecosystem levels. TWP concentrations in aquatic environments span several orders of magnitude, ranging from 10-5 to 104 mg/L in water via pyrolysis-GC/MS. TWPs and their leachates induce oxidative stress, DNA damage, and alter immune responses of aquatic biota, while disrupting feeding behavior, reproduction, and survival. At the ecosystem level, TWPs and their leachates cause shifts in species composition, reduce biodiversity, and alter trophic interactions, destabilizing natural food web dynamics through selective pressure that promotes tolerant taxa and triggers cascading ecological effects. Their presence significantly influences carbon and nitrogen cycling, with environmentally relevant concentrations could promote primary producers, while higher concentrations inhibit photosynthetic nitrogen-fixing biota, disrupt microbial communities, and impair processes such as denitrification and carbon mineralization. Their toxicological and ecological impacts are likely to be intensified by global environmental change, highlighting the need for long-term studies under realistic environmental conditions to better understand underlying mechanisms and develop effective mitigation strategies.