Field collection and laboratory aging of tire-wear particles from electric and conventional versions of the same passenger car

Non-exhaust emissions are now the dominant source of traffic-related particulate matter as tailpipe emissions decline. Tire- and road-wear particles (TRWP) are among the most persistent pollutants. This study compared TRWP from an electric vehicle (EV) and an internal combustion engine vehicle (ICEV) using the same passenger car platform, combining on-road collection with laboratory weathering. On-road measurements showed that the EV emission factor (EF) was 7.6 ± 4.2 mg/vkm, compared with 5.8 ± 1.9 mg/vkm for the ICEV. EV-derived TRWP contained larger rubber and silica fractions (8.01% and 3.95%) than ICEV (2.83% and 0.43%), whereas ICEV TRWP were enriched in carbon black (23.8%) and brake-wear magnetic particles (20.5% vs. 7.1% in EV). Laboratory analyses confirmed these differences. EV-derived TWPs showed higher bulk density (0.179 g/cm vs. 0.170 g/cm), finer suspended fractions (1.02 μm vs. 2.86 μm after UV aging), and greater colloidal stability in water, while ICEV-derived TWPs aggregated and settled more rapidly. Chemical analyses revealed similar initial levels of the tire antioxidant 6-PPD (9547 μg/g in EV vs. 12,102 μg/g in ICEV), but 6-PPD of EV TWPs was depleted more rapidly under photo-oxidation, with a half-life of 7.4 days versus 24.9 days for ICEV. The oxidative transformation of 6-PPD to 6-PPDQ was also proceeded faster in EV samples (k = 0.180 day vs. 0.030 day). These results show that EVs, while eliminating tailpipe emissions, generate larger amounts of more persistent and reactive TRWP. Mitigation will require improved tire formulations, reduced vehicle mass, and road management to extend electrification's environmental benefits.