"We race all around the world, but I've never noticed pollution so badly as in Beijing. Sometimes we'd go for a bike ride before the race, then you'd get back and blow your nose and it's all black," said Reed, the triathlete who suffered an asthma attack last year in Beijing.
To prepare for the Olympics, athletes customarily train for extraordinary conditions such as high altitude or heat. But to train for pollution would not be possible, short of racing behind a bus -- something athletes have actually joked about in the run-up to Beijing.
Jarrod Shoemaker, a 25-year-old triathlete from Sudbury, Mass., said that after racing in Beijing he noticed that "I was so out of breath that I couldn't carry on a conversation, and if I tried to laugh, I'd be doubled up with pain."
He intends to wear a face mask most of his time in Beijing, even if he risks offending the Chinese. "I know it's probably not the best statement to make, but I have to protect my lungs and body."
Jos Hermens, a Dutch sports agent who represents Gebrselassie, says that marathon runners who compete in hot, polluted environments can suffer permanent damage to their health.
"You have to decide how much you want to risk for a particular event. Will you put it all at stake for an Olympic medal?"
Hermens said in a telephone interview Tuesday that he advised Gebrselassie, who still must qualify for the 10,000-meter race, not to run the marathon in Beijing because he already has two gold medals and wants to compete again in 2012. "I suspect other people might follow his example."
Chinese broadcasts of the BBC and CNN on Tuesday night blacked out reports of Gebrselassie's statements.
U.S. official optimistic
In an e-mailed response to questions, U.S. Olympic committee spokesman Darryl Seibel said he did not know of any U.S. athletes who were considering dropping out because of air pollution. He also said the United States would discourage athletes from missing the opening ceremonies.
"We have confidence the air quality during the Games will be at a level that is safe and suitable for elite-level athletic competition," Seibel wrote in the response.
In addition to the triathlon team training in South Korea, American rowers will prepare on the west coast of Japan.
Not every athlete, however, is worried.
Donny Robinson, a 24-year-old cyclist from the Napa Valley, says that some of his fellow athletes are getting hysterical.
"It's all mental with everybody. If they worry so much, it will affect their performance," Robinson said. "I know the Chinese are going to do everything in their power to make the air amazing."
And at least some Beijing residents appreciate all the fuss about the athletes' lungs. After all, they will be breathing the same air.
"We Chinese are too tolerant. We don't complain a lot like the Australians or the Japanese or the Americans," said Bing Xing, a 63-year-old retiree who lives a few blocks from the new Olympic stadium.
Gesturing toward the construction site on a particularly murky afternoon, he said, "As you can see, the situation is not good. Whatever they do to fix it for the Olympics will benefit all of us."