The indoor-outdoor relationship of Polycyclic Aromatic Hydrocarbons (PAHs) from PM_2.5 in Beijing during APEC

Studies confirm that polycyclic aromatic hydrocarbons (PAHs) in PM_2.5 elevate cancer risk. Recognized globally, the majority of exposure to outdoor particulate matter (PM) occurs indoors. Control measures such as traffic restrictions, industrial shutdowns, and designated holidays during the APEC summit significantly altered the concentration of PAHs in indoor and outdoor environments. The indoor-to-outdoor (I/O) ratio for total PAHs concentration is 0.540, while for equivalent toxicity concentration (ETC) and equivalent carcinogenic risk concentration (ECRC), the ratios are 0.552 and 0.549, respectively. In severe pollution, these ratios drop to 0.348 and 0.353. These results show that the containment structure effectively reduces PAHs, particularly in severe pollution conditions. The total average exposure concentration of the population during and after the control measures was 10.780 ng/m³ and 18.600 ng/m³, respectively. The results indicate that the control strategy effectively reduced the concentrations of PAHs indoors and outdoors during the meeting, providing a reference for controlling pollutant concentrations in indoor and outdoor environments.