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

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.