Trend of air quality in Seoul: Policy and science

The trend of air pollutant concentrations in the Seoul Metropolitan Area (SMA)—particularly the city of Seoul—in the Republic of Korea, is shown and analyzed along with applied policy; furthermore, the remaining challenges are identified, and the direction of future research is discussed. The policies adopted from developed countries, notably, direct emission control measures, such as limiting the sulfur content in fuel and tightening emission standards, have been successful in reducing primary air pollutants, e.g., carbon monoxide, sulfur dioxide, and lead; however, these policies have not been effective in controlling the increased number of emission sources and secondary air pollutants, such as particulate matter with an aerodynamic diameter less than or equal to a nominal 2.5 µm (PM_2.5), and ozone. To develop effective control policies on air pollution, the following actions are recommended: (1) creating a reliable emission inventory; (2) reducing uncertainties about the regional contribution to the air quality in Seoul; and (3) understanding the major chemical pathways of ozone and secondary aerosols. Suggestions for accomplishing these goals in future research are also provided.