Distribution patterns of rubber tire-related chemicals with particle size in road and indoor parking lot dust

In recent years, concerns have arisen from the chemicals incorporated into tire material which are of potential to leach with the tire and road wear particles (TRWP) into the environment. In this study, the distributions of substituted benzothiazoles (BTHs) and p-phenylenediamines (PPDs), two groups of representative TRWP-related chemicals, were investigated in various size fractions (<20, 20-53, 53-125, 125-250, 250-500, 500-1000 μm) of dust samples from open roads and indoor parking lots in the urban region of Guangzhou (Guangdong, China). Mass weight distribution of the dust samples showed that fractions of <250 μm accounted for >72% of the total dust in both microenvironments. Widespread occurrence was observed with >80% detection frequency for almost all target compounds in all the particle fractions. Concentrations of BTHs and PPDs were similar between the two dust matrices. In addition, the newly defined transformation product of 6PPD, 6PPD-Q was at the median concentration of 122 ng/g in road dust and 154 ng/g in indoor parking lot dust. Overall, concentrations of the target BTHs and PPDs varied in different size fractions, which were mostly dominated in fine particle sizes (<53 μm). Specially, >70% of the target compounds were in the size fractions of <250 μm, suggesting the necessity of using <250 μm fractions of particles for monitoring and evaluating contamination levels and exposure risks of BTHs and PPDs from dust in future studies.