The Chinese government is clearly concerned with the health and welfare of Beijing residents, as evident from the frenzy of environmental conferences and government conferences being held out at luxury villa compounds out near the airport and in the western hills.

The yesterday's air pollution level 5 or 500 microgram of particulate matter (PM10) per cubic meter was not an all time high. Level 5 was reached for the 7th time this year. Thereof 3 times at least 500 mgr/m3. They stop counting above 500. You can check the history of Beijing's air by entering Beijing and 2006-01-01 to 2006-12-13 at this link: http://www.zhb.gov.cn/english/air-list.php3

The Insider’s guide to Beijing once published a statement of a Doctor from the Beijing United Family Hospital saying that you should avoid going outside when 150 mgr/m3 are reached.
Others see it even more critical. E.g., the Australian Department of Environment and the German Ministry of Environment aim for a daily maximum concentration of 50 micrograms of PM10 per cubic metre (level 1). In Germany every city is allowed to exceed this goal only 35 days per year while in Australia apparently only five days. So in Beijing do not look at the terrible ‘500’-days but look at all the bad days in 2006 when the ‘50’-goal was exceeded: Year to date, there were 347 polluted days in Beijing. Only 25 days where ‘healthy’ days.

I was in Beijing from December 9 through 16. The 9th was definitely the worst - absolutely pisonous air. The cause is not industrial pollutants or power plants. The cause is the burning and uncontrolled emissions from home heating coal furnaces (that's the particulatres and sulfur dioxide) and the growing numbers of automobiles on the streets (Nitrous oxides and sulfur dioxide). In the winter, the coal smoke dominates the picture.