The Beijing sky turned from grey to blue on Friday with the capital's hosting of the Olympic Games only a week away.

The average air pollution index fell to 28, dubbed as "level I" or "excellent," the Beijing Municipal Bureau of Environmental Protection reported on a day when the temperature hit 30 degrees Celsius.

The average index was based on the data of 27 monitoring stations across the city, the bureau said.

A pollution reading below 50 is classified as "excellent", between 51 to100 is "fairly good", between 101 to 200 is "slightly polluted", between 201 to 300 is "poor", and over 301 is "hazardous", according to the bureau.

The city had registered 150 "blue sky" days, or days with fairly good air quality, for the year as of August 1.

Last month saw 26 such days, three more than in the corresponding period last year.

"Car restrictions and other pollution-reduction measures are paying off," said Du Shaozhong, the bureau deputy director.

The city has imposed an odd-even system based on license plate numbers that will keep vehicles off the road on alternate days from July 20 to September 20.

Beijing's neighboring municipality Tianjin and the nearby provinces of Hebei, Shanxi and Shandong, plus the Inner Mongolia Autonomous Region, are also helping the capital to attain its anti-pollution goals by closing major polluters, removing high-emission cars from roads and restoring grassland vegetation.

Last week, Du told reporters the said major air pollutants, such as carbon monoxide, carbon dioxide and particulate matter from vehicles had dropped by 20 percent in Beijing from a year earlier.

More polluting businesses will be shut and more vehicles will be restricted if the air quality worsens due to "extreme unfavorable weather conditions" during the Olympics and Paralympics, according to the Ministry of Environmental Protection.

(Xinhua News Agency August 2, 2008)