Since 2006, there has been an apparent reduction in the PM2.5 concentrations and PM2.5 exceedance days in the five AQZs.PM2.5 concentration was reduced from 32.45 µg m−3 in 2006 to 19.53 µg m−3 in 2017, PM2.5 exceedance days were reduced from 60 days in 2006 to only 15 days in 2017.In particular, during the most recent three-year period (2015–2017),the reduction in the PM2.5 concentrations and the PM2.5 exceedance days was very small in the KP area.