Sell will be hunkering down at the U.S. track and field team's base in the resort town of Dalian in northern China, near the border of South Korea until just four days before the marathon. Dalian has a nice golf course to run on, and the air is usually clear.
"I am a little concerned about having trouble breathing after running two-plus hours," Sell says, "and inhaling as deep as I will be during the marathon in that pollution."
There is precious little research on the impact of particulate pollution, which causes visible smog, specifically on athletes. But what little exists suggests that Sell is right to be concerned.
In a study published in January in the
The hockey players completed two six-minute rides in low pollution over three days, and then a week later did a six-minute ride in high pollution, and then three days after that, they did a final ride in high pollution. In the first three rides (two in low pollution and one in high) the subjects performed the same. But in the second high-pollution test, three days after the first, the amount of work the hockey players got done in six minutes decreased by about 5.5 percent.
The effects of pollution on the body are complex and little understood, but, theoretically, a 5.5 percent percent reduction in the workload an athlete could achieve might translate to as much as seven lost minutes for an elite marathoner. It isn't clear what exactly causes the apparent delayed response to pollution that the researchers documented -- lung inflammation and increased blood pressure are among the suspects -- but it does suggest that in a high pollution environment, according to
Beyond being inconvenient, or impossible for those running multiple heats and events, like U.S. 1500/5K star
Some articles have suggested that Chinese athletes may even have a "home smog" advantage, having developed a tolerance to pollution, and in the case of ozone -- which is a concern in many American cities as well -- this may have some truth to it. With respect to particulate pollution, however, building a tolerance is not a good strategy. "If you live in [a high particulate pollution environment]," says Rundell, "it's not too far from smoking in terms of decreased lung function over time."
Worst off will be athletes with asthma or those who are especially sensitive to particulate pollution. They will experience a greater decrease in lung function if the smog rolls in. At a meeting of the American College of Sports Medicine in 2007, several scientists suggested that British track luminary
Ovett came to Los Angeles in 1984 hoping to defend his 800 title, but started experiencing breathing difficulties before he even ran. Ovett not only didn't defend his title, he finished last in the final, collapsed after the line, and spent the next two nights in the hospital. "Many suffered from the bad air," Ovett later wrote in the journal
Perhaps of primary concern to athletes, though, should be carbon monoxide. This is the stuff that kills you if you're locked in a room with a running automobile, but because it's clear, odorless, and doesn't cause smog, it has largely drifted below the media radar in the run up to the Beijing Games.
Carbon monoxide occupies the same spot -- attached to a protein called hemoglobin -- in red blood cells as oxygen. But CO clings to hemoglobin much more tightly than O. Once a carbon monoxide molecule gets hold of hemoglobin, any nearby oxygen had better look for a home next door. Athletes won't experience any long-term damage from carbon monoxide, but "for competition, this is a serious concern," says
Studies of athletes exercising close to heavy traffic have shown carbon monoxide levels of about 5 percent in the blood -- similar to the level in a smoker who just indulged -- meaning that there is space for 5 percent less oxygen to be carried in the blood and then delivered to the muscles. "That could really make an impact on aerobic performance," Clifford says. And the impact might not be spread out equally.
Clifford guesses that athletes who have a lower hematocrit -- the proportion of blood that is oxygen carrying red blood cells -- will feel the effects more acutely than their high hematocrit counterparts. Because women generally have lower levels of hemoglobin and fewer red blood cells, if Clifford's suggestion is correct, female athletes are more likely to be effected by carbon monoxide.
"My sense is that it will make a difference," Clifford says of carbon monoxide pollution at the games. "Really small differences in the amount of oxygen in the blood can make a difference in performance when you're working at the maximal level of the body to bring in and deliver oxygen."
On the bright side, the measures that Chinese officials have taken to get cars off the streets during the Olympics, and to shutter factories and construction sites should decrease the amount of carbon monoxide at event venues, even though it will have little or no impact on visible smog. Smog causing particulate pollution
Nonetheless, Chinese officials and, on Thursday, IOC president