Temporary measures designed to improve air quality for next month's Olympics have cut overall air pollution by about 20 per cent, Beijing officials said on Friday.
"I'm sure the effects have already been felt and are quite evident," Du Shaozhong, deputy director of the Beijing Environmental Protection Bureau, told reporters.
The aggregated level of major air pollutants such as carbon monoxide, carbon dioxide and particulate matter dropped this month by 20 per cent year-on-year compared with July 2007, Du said, reported dpa.
The city said it recorded 22 "blue sky" days in the first 25 days of July, and 13 more "blue sky" days year-on-year in the first six months of 2008.
"These (numbers) show that the temporary measures have had a significant effect," Du said.
But China does not use international standards for monitoring air quality and the accuracy of its systems remains unclear.
Even the government's official Xinhua news agency, in its report on the new measures on Friday, said residents and visitors to Beijing "still complain, as the city is covered by mist and fog as usual."
China had a 12.3-billion-dollar budget for environmental work for the Olympics and has imposed temporary restrictions on vehicles before and during the August 8-24 Games.
All private vehicles are limited to alternate-day usage from July 20 to September 20, based on licence plates ending in odd and even numbers.
Many heavy trucks and all vehicles which do not meet the European number one emissions standard are banned completely.
The traffic control measures are expected to remove a daily average of about one-third of the city's 3.3 million vehicles.
China has also ordered controls on industrial pollution and suspended dust particles, including limits on coal burning in neighbouring provinces.
At the opening of the Olympic media centre in early July, Hein Verbruggen, the IOC's games coordinator, said air quality was one of "a very small number of open issues" remaining.
The IOC has contingency plans for the possible rescheduling of cycling, distance running and other events demanding high respiratory function for more than an hour, depending on pollution and other factors such as heat, humidity and wind.
The United Nations Environmental Programme said last October that the relocation of major polluting industries, a switch away from coal burning and the scrapping of highly polluting vehicles in Beijing had also spurred a fall in concentrations of several key air pollutants, including sulphur dioxide and carbon monoxide.
But the agency said Beijing's level of small suspended particles, known as PM10, often greatly exceeded World Health Organization guidelines. PM10 are hazardous inhalable particles between 2.5 and 10 micrometers in diameter.
Dust storms and mountains blocking the circulation of air in Beijing exacerbate the problem, the UN agency said.