Aside from the analysis of the API, we also paid attention to the actual pollutant concentration level of those Olympic cities, especially the trend of concentration level from 2000 to 2007 in monthly scale. In this section, PM10 concentration levels were calculated based on the API data as published by the relevant environmental departments. The calculation method is derived from national standard used for calculating API data (for more information, please refer to http://www.sepa.gov.cn/quality/background.php). In the following part, monthly average PM10 concentrations were calculated, and the trends of the same month from 2000 to 2007 were analyzed.
The analysis shows that July and August are comparatively two clear months, with the lowest API concentration and PM10 concentration level.
For most Olympic cities, the January average concentration level decreased generally from 2001 to 2008, especially for cities like Beijing, Qingdao and Tianjin.