Chemical Characterization of Tire Wear Particles: Size-Resolved Composition and Source Signatures in Near-Road PM Samples

XING WANG, Yushan Su, Colman Wong, Michael A.R. Tawadrous, Chelsea Rochman, Bonnie Hamilton, Alex K.Y. Lee, Greg J. Evans, Arthur W. H. Chan, University of Toronto

     Abstract Number: 138
     Working Group: Chemicals of Emerging Concern in Indoor and Outdoor Aerosol: Sources, Vectors, Reactivity, and Impacts

Abstract
Tire wear particles (TWPs) have become an increasingly important source of traffic-related particulate matter due to the declining emissions from internal combustion engine vehicles. However, their chemical composition and contribution to near-road air pollution remain poorly characterized. This study employs offline pyrolysis gas chromatography mass spectrometry technique to investigate polymeric composition and tire-derived additives in both lab-generated tire particles and size-selected particulate matter samples collected near a highway. Distinct tire chemical-to-rubber ratios are observed for new, worn, and ambient TWPs. New tire tread particles exhibit higher antioxidant ratios, whereas worn tread particles show elevated pyrene levels. Field samples display an increased chemical-to-rubber ratios with decreasing particle size, highlighting mechanistic differences in fine and coarse TWP generation. Additionally, the natural-to-synthetic rubber ratios in ambient particles were higher on weekdays than weekends across all size fractions, consistent with increased truck traffic volume and higher natural rubber content in truck tires. While TSP and PM10 ratios fell below model predictions, PM2.5 ratios exceeded theoretical values, suggesting different emission processes for fine and coarse TWPs. Our findings provide insights into the size-resolved chemical and polymeric profiles of TWPs, enabling more accurate source apportionment and assessment of their environmental and health impacts.