Haikou, Xiamen, Fuzhou, and Guiyang met the daily air quality standard, while Hengshui, Jinan, and Xingtai met the standard less than 50 percent of the time. For those cities failing to meet targets, ozone was the primary pollutant, followed by PM2.5. In general, the Jing-Jin-Ji and Yangtze River Delta regions have decreased their major pollution concentrations, but ozone increased, especially in the Yangtze River Delta. PM2.5 and PM10 concentrations increased in the Pearl River Delta region, while other pollutant concentrations decreased.
（Source：The Paper）
