China is mulling more stringent appraisal standards for air quality, and pilot projects are likely to start from coastal cities in the Yangtze River delta and Pearl River delta next year.

The environmental authorities are planning to include particles less than 2.5 microns (PM2.5) and ozone, into the Air Pollution Index (API), which currently measures the concentration of sulfur dioxide, nitrogen dioxide and PM10, or particles smaller than 10 microns.

The new evaluating system will cover all the airborne pollutants that are damaging to health as per the global air quality guidelines issued by the World Health Organization (WHO) in 2005.