Natural factors have been blamed for the worst air pollution Beijingers have experienced this year.
The municipal environmental protection bureau said that current weather conditions meant the city's pollution was not being dispersed.
Specifically, there has been low air pressure and strong temperature inversion, which is where a band of warm air rests above a band of cold air.
This makes it difficult for air to circulate and so blow Beijing's pollution away.
Air quality between Monday and Wednesday slumped to the fifth level, a standard reserved for only the most seriously polluted air, according to Beijing Environmental Protection Bureau.
Although the sunshine was strong during the three days, there were heavy fog and smoke, preventing residents from enjoying the blue sky.
The bad air quality has influenced residents' life and work.
"When I got up on Tuesday morning my nose felt uncomfortable. I can feel the air is full of dust. Considering that I am now expecting a baby and I have allergic rhinitis, I had to ask for one day's leave and stayed at home to rest," said Chen, a lady who has lived in Beijing for 11 years.
"Before I came to Beijing, I had never suffered from the allergic rhinitis. The capital's weather always upsets me," she added.
Rick Eldridge, from the United States and who has worked in Beijing for two years, also believes Beijing's weather is terrible. "When I check the weather in the world on the Internet, I always find that Beijing is smoggy. I think the reason for the bad weather might be the fact that cars have increased in recent years."
"I know the government is making efforts to improve the air quality, but today's air is still terrible. I miss the blue sky in my hometown when Beijing is smoggy. But I have to live here because I am working here," he told China Daily.
The bureau reminded residents to cut the amount of time they spend outdoors to avoid inhaling too many pollutants.
Besides the weather, the smog is also the result of pollution. Industrial smoke, car emissions, fumes from coal burners and dust from construction sites are all to blame for the capital city's perennial air pollution headache, said Zhao Chengyi, an official with the bureau.
The municipal government is striving to improve Beijing's air quality through various methods, said Zhao.
To deal with the city's industrial smoke, Beijing Shougang Group, one of the country's leading iron and steel producers and Beijing's biggest polluter, has been ordered to move out of the capital. This began at the end of last year and is expected to be completed before 2010.
Car emissions have contributed greatly to the city's air pollution in the past few years as the number of private cars has rocketed. At present, the city has more than 2.3 million automobiles. To curb car emission pollution, the municipal government will implement the "Euro III" standard on July 1.
And since 1998, the capital has begun a large-scale transformation of its traditional coal-fired boilers. In Xicheng District alone more than 1,600 traditional boilers now use clean energy, the Beijing Youth Daily reported yesterday.
As to the dust emitted from the city's 6,300 or so construction sites, which occupy some 100 million square meters, the municipal government has required them to stop work when it is too windy.
(China Daily April 7, 2005)