The average density of PM 2.5, airborne particles measuring less than 2.5 microns, dropped by 73.2 percent after efforts were made to ensure clean air for IAAF World Championships and WWII V-Day military parade, the Beijing Municipal Environmental Protection Bureau said on Sunday.

"For 15 days, residents have experienced good air quality," said Zhang Dawei, director of the Beijing Municipal Environmental Monitoring Center. "It was as good as the annual index in some metropolises in developed countries, such as Paris, London, Moscow and Singapore."

The reduction on PM2.5 was mainly due to the restriction of coal consumption and use of vehicles, said Zhang. And the sulfur dioxide concentrations were also reduced.

Beijing began to adopt temporary measures to ensure air quality on August 20. The density of nitric oxide, a vehicle exhaust, more than halved in the morning rush hours.

Nearly 2,000 industrial firms, including petrochemical and cement plants, suspended or cut production in Beijing.

Similar measures were adopted in neighboring Tianjin, Hebei, Shanxi, Shandong, Inner Mongolia and Henan.

Without the measures, the density of PM 2.5 could have been 70 percent higher, said Pan Tao, deputy director of Beijing Municipal Research Institute of Environmental Protection.

Such measures contributed to blue skies during the 2008 Summer Olympics and the APEC meetings last year.