Tire-additive chemicals and their derivatives in urban road dust: Spatial distributions, exposures, and associations with tire and road wear particles

Tires, as a globally utilized product, emit pollutants including various tire-additive chemicals (TACs), and tire and road wear particles (TRWPs) containing substantial microplastics. Several TACs have been proven to have aquatic toxicity, induce health risks including endocrine disruption, allergic effects, and cardiovascular problems, while TRWPs are also very strongly suspected. With the emergence of multiple novel TAC derivatives recently, yet knowledge of their occurrence, spatial distribution, and potential associations remains largely insufficient. In this work, we have systematically investigated 25 TACs, including para-phenylenediamine (PPDs), several newly identified quinones (PPD-Qs) first reported in urban dust, and TRWPs across road dust from Hong Kong and Berlin. By coupling UPLC-MS/MS and pyrolysis-GC/MS analyses, we achieved concurrent quantification of trace TAC derivatives and TRWPs. Distinct spatial patterns of these tire-derived contaminants were identified, in which Hong Kong exhibited higher TACs linked to dense traffic, while the TRWP levels reached 9420 μg/g near auto factory in Berlin. Highway dust contained maximum contaminant loads of both TACs (5.0-fold higher) and TRWPs (5.3-fold higher) compared to other road types. Significantly linear associations were found between emerging TAC derivatives and TRWPs, implying their potential as candidate markers. Exposure assessments revealed PPDs and PPD-Qs intake doses surpassed benzothiazole and its derivatives, highlighting non-negligible risks caused by emerging TAC derivatives. This work establishes a framework for evaluating region-specific emission drivers and provides critical baseline data of multiple tire-related contaminants across different compartments. Potential markers for TRWPs were identified, which may be further utilized for their identification and determination.