The impact of the energy consumption and environmental policies in northeast Asia to the air quality in Seoul, a megacity in South Korea was studied by combining the results of receptor modeling, air parcel trajectory analysis, energy consumption trend, and policies in the region. A chemical mass balance (CMB) modeling study was carried out based on the measurement data of particulate PAHs during 2002–2003 and 2006–2007 along with backward trajectory analysis. The reliability of the modeling result was checked by performance test and sensitivity analysis by including loss term in the source profiles. For both periods transportation and coal consumption for coke oven were major sources for the PAHs level at Seoul. However, during 2006 to 2007, the contribution from coke oven became larger than transportation, while during 2002 to 2003 the contribution from transportation was higher. Furthermore, it was observed that when air parcels moved from north China or Shandong Province the relative contribution from coke oven was higher than when air parcels moved from northeast/north China and North Korea. This observation was in accordance with the trends of coal consumption and cokes production in north China, Shandong Province, and northeast China. On the other hand, the contribution from transportation decreased, mainly due to the emission reduction in Seoul through several policies regulating vehicular emissions. It was suggested that the impacts of China to the air quality of Seoul might continuously keep increasing for some years ahead since the consumptions of coal in general and in coke oven, in particular, are increasing. Thus, more strict policies with additional regulation and introduction of more stringent standards should be considered. Also, uncertainty and limitation of this study result was discussed and further research directions are suggested.