Unveiling Chlorinated Paraffin Emissions via Tire Wear and Airborne Release from Various Types of Tires

Ubiquitous vehicle operation leads to the continuous emission of tire additives into the environment via tire wear particles (TWPs) and air emission. Significant knowledge gaps remain regarding the abundant additive chlorinated paraffins (CPs) in tires. This work investigates short-, median-, and long-chain CPs (SCCPs, MCCPs, and LCCPs) in end-of-life and new tires of the same models for sedans, SUVs, trucks, and vans in China. CP levels ranged from 81-245 μg/g (mean 137 μg/g) in 2018 end-of-life tires and 6-183 μg/g (mean 71 μg/g) in 2023 new tires, dominated by SCCPs and MCCPs (mainly C_13-14). A decreasing trend of CPs (2018-2023) was observed in SUV, truck, and van tires. Tire mass evaluation and a simulated air emission experiment indicated that TWP emission and air emission contributed approximately 20% and 6%, respectively, to the total CP loads of tires over their lifespan. TWP emissions made tires significantly more efficient in spreading CPs compared with other CP-containing products. The discharge of CPs from TWPs was estimated at 160 tons per year in China, with a dominant contribution from sedans and heavy trucks. This study enhances understanding of CPs’ presence and environmental emissions in tires and underscores the significant impact of tire-derived CPs.