Gray Wall Dims Hopes of 'Green' Games

For athletes unaccustomed to Beijing's pollution, the assault can feel like "an invisible wet rag that chokes your lungs," Cassmassi said. "Eventually you acclimatize yourself, but a lot of people are going there and all of a sudden they're hit with pollutants they're not used to."

"Carbon monoxide replaces oxygen in the bloodstream and reduces the body's ability to oxygenate its tissue," said James M. Lents, a former top executive of air pollution control programs in Los Angeles and Colorado. Ozone and sulfur dioxide attack tissue in the airways, hampering breathing and the processing of oxygen.

Even Chinese researchers have complained about the overly general pollution data, saying they are forced to purchase more specific information from various jurisdictions.

"We have been trying to get more detailed statistics on deaths from respiratory disease from the health department and pollutant concentration from the environmental department, but it's just too hard to get it," said Pan Xiaochuan, a Beijing University medical school professor studying the effect of inhalable particles on respiratory systems and death rates. "It has been secret information for the departments."

Chinese officials prefer to publish a citywide average for pollutants, arguing that readings from one location lack context. But averages tell nothing about pollution in a specific part of a city, analysts say.

What the government does measure, and is fond of citing, are "blue sky days," which its own environmental scientists concede are of no use when trying to actually measure pollution. "Blue sky days can't be considered a serious scientific notion," said Du Shaozhong, deputy director of the Beijing Municipal Environmental Protection Bureau. "It's just a saying that is understandable to the media and the public."

China has no national standard for evaluating ozone, Du said, because the explosion in the number of cars has been a relatively recent phenomenon. Its focus on sulfur dioxide follows years of burning coal.

"We promised for the Olympics that we will closely monitor carbon monoxide, nitrogen dioxide, sulfur dioxide and particulate matter. Of course, considering that ozone is important to people's health, we are also watching it," he said. "But the formation of ozone needs special conditions, like enough light, humidity and temperature, so once we can control one condition, we can control the ozone."

Some analysts express hope that a new environmental information law meant to take effect next year will help.

"What's going on now is a complex negotiation among those who share the Beijing airshed," said Deborah Seligsohn, who monitors energy and pollution issues in China for the Washington-based World Resources Institute.

"In the last year, the Chinese have put continuous monitoring equipment on power plants of 25 megawatts or more, which is a huge improvement," Seligsohn said. "There's a lot of work to be done. They're moving forward on many fronts at the same time, some of which will bear fruit by the Olympics and some of which won't."

News researcher Li Jie contributed to this report.