Fig. 2

Temporal variations of air quality parameters during January 2010 – July 2015. The monthly averages of the daily mean values of temperature, relative humidity, the concentrations of carbon monoxide, nitrogen dioxide, oxidants, sulfur dioxide, PM2.5, and SPM, and the number of ASD events per month. Data were collected from the ministry of environment of Japan and all the monitoring stations from which data were available. Data except for the number of ASD events were presented as mean ± SD. Open circles and closed circles represent the data in Kumamoto and Niigata, respectively. The national ambient AQS is shown as a dotted line