Tire and Road Wear Particles as Vectors of Hydrophobic Tire Additives: Quantifying Contributions to Chlorinated Paraffins in Urban Road Environments

Abstract

A recently developed large-scale separation protocol enabled gram-scale isolation of tire and road wear particles (TRWPs) from road dust and roadside soils, providing sufficient material to evaluate their role as carriers of tire-derived chemical additives. An abundant class of hydrophobic tire additives, chlorinated paraffins (CPs), was detected in all samples, with concentrations ranging from 11 to 36 μg g^–1 in road dust, 9.6–15 μg g^–1 in roadside soils, and 110–290 μg g^–1 in dust- and soil-derived TRWPs collected from multiple road environments in a megacity. CP homologue fingerprints in road dust were strongly correlated with those in corresponding TRWPs, suggesting a potential shared source. An exponential relationship between TRWP abundance and its contribution rates to CPs (R² = 0.95, p < 0.01) showed that TRWP levels govern CP contributions in road dust. TRWPs contributed more than 45% of total CPs at nearly half of the dust sampling sites and 9.8–24.8% in roadside soils. From a broader environmental perspective, estimated contributions were >44% in TRWP-rich environments, 15–36% in urban road dust, and 5–10% in roadside soils. These results provide the first evidence of CPs in environmentally derived TRWPs and quantitatively demonstrate the dissemination of hydrophobic tire additives via TRWPs across urban road environments.