Background of the many photochemical smog advisories issued around 2007 in Kyushu and Yamaguchi

Background of the many photochemical smog advisories issued around 2007 in Kyushu and Yamaguchi
The first such event in a decade, the number of alerts covering wide areas of Fukuoka, Nagasaki, Kumamoto, Oita, and Yamaguchi had a major impact on the local community. Photochemical smog is caused by the reaction of nitrogen oxides and volatile organic compounds with strong solar radiation, and after becoming severe in the 1970s, it decreased for a time in Japan due to stricter regulations, but in the 2000s, it began to increase again in western Japan.
There are two factors that are responsible for this trend. First, rapid urbanization and industrialization in coastal China led to a sharp increase in air pollutant emissions through the early 2000s. As pointed out by the National Institute for Environmental Studies, transboundary pollution from China became a new policy issue for Japan at that time, and it was also a problem that local governments were unable to address. Second, changes in weather conditions contributed to photochemical reactions: the combination of higher temperatures and increased solar radiation in the summer around 2007 created a weather pattern in which the westerly wind flow shifted to the south, causing air from mainland China to flow easily into northern Kyushu.
In response to this situation, the governor of Fukuoka Prefecture requested the Ministry of Foreign Affairs to take countermeasures, and there was widespread recognition of the need for a broad-based, international framework. The high number of advisories in Kyushu and Yamaguchi was an impetus for moves toward air quality talks and a joint international observation system between Japan, China, and South Korea, as local countermeasures were limited This phenomenon in 2007 symbolized a new era of environmental problems, in which climate change, changes in industrial structure, and transboundary air pollution are all intricately intertwined.