Tire wear particles and leachable compounds: Occurrence and fate in the aquatic environment

Tire wear particles (TWPs) have emerged as significant contaminants in the aquatic environment, posing risks to local flora and fauna. Tire waste management methods like reuse and pyrolysis offer benefits but raise environmental concerns, including leachate and toxic emissions. TWPs accumulate in landfills and enter aquatic systems through atmospheric fallout and runoff. TWPs substantially contribute to the presence of synthetic polymers in the ocean, with emissions making up a notable proportion. The primary concern of TWPs lies in the leaching of chemical additives and their transformation products. A prominent example is the highly toxic quinone transformation product of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), a globally prevalent tire antioxidant. 6PPD-quinone was identified using Effect-Directed Analysis (EDA), a promising strategy for the identification of unknown toxic chemicals. This review explores current knowledge on the occurrence and fate of these hazardous TWPs and their leachates, analytical methods, their potential toxicity, and strategies for mitigation. As of the time this review was written, no standardized protocol has been universally adopted for tire wear particles (TWP) and their leachate collection, isolation, and analysis. Therefore, establishing standardized methodologies is essential to ensure consistency and comparability across studies. Additionally, research on TWP and its environmental impacts in developing countries remains limited. This lack of data poses a significant challenge in addressing TWP contamination in aquatic environments within these regions.