Air quality in Beijing this year has been at the best level in a decade, the city's environment authorities said Friday.

"As of Thursday, Beijing has reported 214 grade I and grade II days, about 82.3 percent of all the monitored days," said Chen Tian, deputy head of the Beijing Municipal Environmental Protection Bureau. "It only takes 46 more days for the city to achieve its goal of 260 full-compliance days this year."

The Chinese capital uses a five-grade classification of air quality on the basis of pollution indices, with Grade I being the best and Grade V the worst. Days with Grade I and II air quality are regarded as "blue sky" days.

Chen said as of Thursday, Beijing had reported an increase of 18 "blue sky" days compared with the same period last year, when a massive effort was made to improve the air quality for the Olympic Games.

"Now it is still hard to predict the air quality on Oct. 1, when a military parade will be held in Beijing to celebrate the 60th anniversary of the founding of the People's Republic of China," Chen said.

He said the city's environment authorities had taken measures to ensure the air quality that day, including dust pollution control and vehicle exhaust reduction.

"Anyway, it depends on both the human and the climate elements," Chen said.

Beijing has halted or relocated more than 140 pollution factories in the downtown area over the past years. As of Sept. 11, it has upgraded or banned more than 92,100 vehicles which failed to meet the city's emission standard.

Also on Friday, Li Kunsheng, an official with the bureau said Beijing was expected to upgrade its vehicles' emission standard to China 5, an equivalent of the Euro 5, in around 2012.

He said the move would not only help better the city's air quality but also make room for the rapid growth of Beijing's vehicle number.

The Euro system of standards sets limits on the amount of nitrogen oxides, carbon monoxide and other compounds permitted in car emission. Beijing introduced the standards for new vehicles and plans to gradually retire older models that don't meet the standards.

Euro 5 standard, which has been adopted in Europe since September, slashed emissions of particulates from diesel cars by 80 percent and nitrogen oxides (NOX) by 20 percent. It would also cut NOX and hydrocarbon emissions from gasoline or petrol-powered cars by 25 percent.

Statistics showed that Beijing had more than 3.8 million vehicles at the end of August.