Tire and road wear particles contribute highly to N-(1,3-dimethylbutyl)-N′ -phenyl-p-phenylenediamine (6PPD) and heavy metals in road dust on driving school grounds and their risk implications in China

Tire and road wear particles (TRWPs) have received much attention due to their substantial emission and potentially adverse environmental impacts. The specific contribution of observed contaminants, as critical additives of tires, from TRWPs has not yet been comprehensively studied in the environment. As one of TRWPs generated hotspots, driving school grounds in China were chosen to identify source contributions of heavy metals (HMs) and N-(1,3-dimethylbutyl)-N′ -phenyl-p-phenylenediamine (6PPD) from TRWPs. Significant correlations (P < 0.05) were found between TRWPs and 6PPD and zinc (Zn). The average measured content of 6PPD in road dust was 0.47 ± 0.18 μg/g (n = 50). The estimated level of 6PPD in road dust (5.68 ± 3.36 μg/g, n = 50) was far higher than the measured level of 6PPD in road dust on driving school grounds, implying that TRWPs contributed to 6PPD in road dust from driving school grounds. Compared to the levels of 6PPD in other road dusts, 6PPD in road dust from driving school grounds was higher, exhibiting more significant exposure risks to children with the higher estimated daily intakes. Furthermore, source apportionment through the lead isotopic analysis and positive matrix factorization model revealed that TRWPs were confirmed to contribute more Zn, cadmium (Cd) and lead (Pb) on driving school grounds, notably accounting for 76 %, 31 % and 29 %, respectively. These three HMs presented relatively moderate to strong pollution and corresponding potential ecological risks. Our findings can help identify specific contributions of tire-related additives released from TRWPs in the environment and their potential risks.