Region-specific characterization and ecotoxicity assessment of PAH compounds in winter PM2.5 from three capital cities in Northeast Asia

Industrialization and urbanization in Northeast Asia have heightened PM_2.5 pollution, posing significant public health risks. This study examined the spatial and chemical variability of polycyclic aromatic hydrocarbons (PAHs) and their ecotoxicity in winter PM_2.5 from three capitals-Ulaanbaatar (UB, Mongolia), Beijing (BJ, China), and Seoul (SE, South Korea)-using two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC-TOF MS). PM_2.5 samples collected between December 15, 2020 and January 14, 2021 revealed UB had the highest concentrations (85.7 ± 36.7 μg m^-3) and PAH levels (758.9 ± 224.7 ng m^-3), primarily from coal combustion and biomass burning. BJ (30.3 ± 16.9 μg m^-3; 41.4 ± 18.4 ng m^-3) and SE (26.0 ± 14.4 μg m^-3; 6.2 ± 2.4 ng m^-3) had lower PAH levels but a higher share of secondary products, including oxygenated (OPAHs) and nitrogen-containing PAHs (NPAHs). Overall, 646 PAH compounds were identified: UB was dominated by methylated alkyl and sulfur-containing PAHs, while BJ and SE had more hydroxylated and carbonylated PAHs. QSAR ecotoxicity analysis indicated the highest toxicity in SE from hydroxylated PAHs and a broader toxic range in UB. These findings support air quality strategies to reduce coal combustion in UB and secondary PAH formation in BJ and SE.