A Comparative Study of Urban Air Quality in Megacities in Mexico and Japan: Based on Japan-Mexico Joint Research Project on Formation Mechanism of Ozone, VOCs and PM2.5, and Proposal of Countermeasure Scenario

Photochemical ozone and black carbon are key substances both for regional air pollution and global climate change. These two pollutants are so-called SLCPs (Short-Lived Climate Pollutants). International comparison studies among megacities with widely different conditions are effective in clarifying the formation mechanisms of SLCPs. A comparison study in megacity areas of Japan and Mexico mainly focusing on ozone, VOCs (volatile organic compounds) and PM2.5 was conducted based on air pollution trend analysis and field measurements including vertical soundings of ozone and meteorological parameters. In this study, co-beneficial countermeasure scenarios based upon the obtained scientific data has been proposed. Photochemical ozone, EC (elemental carbon; a major SLCP), and NOx (nitrogen oxides) and VOCs (NOx and VOCs are implicit SLCPs) need to be controlled to improve the regional and global atmospher ic environment. In Japan, countermeasures including the whole Asian area wil l be necessary because there is considerable contribution from trans-boundary air pollution. In Mexico, regulation of VOCs including energy shift and diesel exhaust gas control will be effective. These findings will be utilized to formulate and/or evaluate ProAire (Program for Air Quality Improvement) for the three studied megacity areas of Mexico.