Beijing, Aug. 23 : The Air Pollution Index (API) in the Olympic host city has dropped by over 20 percentage points compared with the same period last year, said an official here on Saturday.

The API declined from around 80 points last year to about 56 during the Olympic Games in August, said Du Shaozhong, deputy director of the Beijing Municipal Environmental Bureau at a press conference.

Major air pollutants on average dropped 40 percent, with nitrogen oxide emission directly related to vehicles down by 61 percent, and inhalable particulate matters falling 40 percent, said Du.

According to the Beijing municipal government, the city has invested more than 140 billion yuan (20.5 billion U.S. dollars) since 1998 to improve its air quality.

ANI