Characterization of tire and road wear microplastics and phthalates in inhalable PM₁₀ road Dust: Implications for urban air pollution

Road dust (RD) is a major contributor to urban environmental pollution. Among its constituents, tire and road wear microplastics (TRWMPs) and phthalates are of increasing concern due to their adverse impacts on human health and ecosystems. This study presents the first integrated analysis of TRWMPs and phthalates in inhalable PM₁₀ RD, collected from industrial and residential areas in Seoul, Korea. Mean TRWMP concentrations were higher in industrial areas (18 mg/g) than in residential areas (16 mg/g), reflecting the influence of truck-bus radial (TBR) vehicles, which have greater tire wear emission factors than passenger car radial (PCR) vehicles. However, elevated styrene-butadiene rubber (SBR) to natural rubber ratios in PM₁₀ compared to PM₇₅ RD suggest that PCR vehicles contribute more to the formation of smaller TRWMP particles, as PCR tires generally contain more SBR than TBR tires. Phthalates were detected at notable concentrations (mean: 245 μg/g), with bis(2-ethylhexyl) phthalate (DEHP) as the dominant species, followed by diisononyl phthalate (DINP) and dibutyl phthalate (DBP). A moderate positive correlation between DEHP and TRWMPs indicates that traffic-related emissions may be a key source. Additionally, a pronounced DBP–SBR correlation in residential areas suggests PCR vehicles as major DBP contributors. Estimated atmospheric emissions of PM₁₀ TRWMPs (61,194 kg/yr) and phthalates (756 kg/yr) underscore their significance as urban airborne contaminants. This study offers novel insights into the characteristics, spatial distribution, and co-occurrence of TRWMPs and phthalates in PM₁₀ RD, providing a foundation for assessing their environmental and health impacts and for developing targeted mitigation strategies in urban environments.