Athletes participating in the Beijing Olympics this summer could face a troubling combination of polluted air and hot, humid weather conditions if the Chinese government is not able to clear the skies in time for the games.

China is planning to shut down factories and limit automobile use starting in July in a push to get rid of the city's heavy smog by the opening ceremonies on Aug. 8.

Concerns over pollution have prompted the U.S. Olympic Committee to create a preventative plan centered on alternate training sites that will allow athletes to adjust to the time zone and heat conditions, without the pollution.

Most of the athletes will live and train in South Korea, Japan or Singapore in the days before the games to avoid the poor air quality, U.S. Olympic Committee senior sport physiologist Randall Wilber said in an e-mail.

"It is disadvantageous to attempt to acclimatize to air pollution," Wilber said, though some of the indoor sport participants will train in Beijing on a limited basis.

Wilber also has recommended athletes wear specially designed face masks when they are outside in Beijing. The British Olympic Association abandoned a similar plan in April, after finding that face masks were not effectively preventing pollutants from entering the lungs.

The air quality issue has coaches and athletes, like U.S. cyclist Kristin Armstrong, on the alert.

She traveled to Beijing in December to check out the courses and assess the pollution problem.

"We wanted to make sure if I did have any real problems we took action," Armstrong said. She was content with her performance, but the pollution problem was evident.

"There were days that were really bad. I'd look out my hotel window and couldn't see the next building."

The USOC's Wilber visited Beijing in early April and reported no improvement in the air quality yet, but said he is confident the government will be able to reduce the level of air pollution to prevent problems for the athletes.

The president of the International Olympic Committee, Jacques Rogge, down-played the pollution issue at an April 5 press appearance, but acknowledged the air quality could reduce athlete performance.

Days earlier, Hein Verbruggen, chairman of the IOC coordination commission, told Reuters some events lasting more than an hour might be delayed if the pollution levels are high.

The pollutants present in Beijing's air, including carbon monoxide, ozone and particulate matter from smokestacks and construction sites can be detrimental to pulmonary function and oxygen transport.

If the pollution does not improve, athletes with asthma could be susceptible to serious health risks, Wilber said.

Already, Ethiopian world record holder Haile Gebrselassie, who has asthma, decided not to compete in the marathon because of the health risk. But for many athletes, the air quality is just another condition they will have to deal with at the games.

"I don't know what to expect, but this has been a life long goal so I'm not going to turn it down because of the air quality," U.S. marathoner Brian Sell said.

"It could be in Death Valley or the middle of the desert and I'm still going to run. It's the Olympics."

Pollution could have the greatest effect in outdoor events that involve being active for over 60 minutes, such as the marathon, triathlon, cycling and tennis.

Men's Olympic tennis coach Rodney Harmon said he will be sending his team members to a respiratory doctor and allergist. He said he also wants to get the athletes out on the court prior to their events to make sure their bodies are recovering correctly and their heart rates come down in a reasonable amount of time.

"The heat puts a lot of stress on your respiratory system, so if there is an issue with the air quality it makes it that much harder for your body to recover," Harmon said. "If we have any athletes that have asthma it's going to be a huge concern."

Armstrong will be competing in the 66-mile cycling road race in her second Olympics. She has been training in Lucerne, Switzerland, to compete with top cyclists.

Unlike the 2004 Athens games, when she attended the opening ceremonies and enjoyed the entire Olympic experience, Armstrong plans to arrive in Beijing just five days before her event to give her body time to adjust, but not too much time breathing the air.

"The more time you're there, the more time it has to get into your lungs and get into your chest," she said. "If you expose your lungs by working out prior to your event it can open up the risks to it affecting your event."

Marathoner Sell, who is training in Rochester Hills, Mich., said he is more concerned about the heat than the air quality and that as the Olympics get closer he will move his training to Florida to run in heat and humidity.

"As far as the pollution goes, there isn't a whole lot you can do besides run behind a Hummer," Sell joked.

Bryan Volpenhein has competed in two Olympics as a rower and will look to repeat this year. He said he is "a little concerned" about the air and plans to follow any recommendations, whether it is wearing a mask in Beijing or training in similar conditions on U.S. soil.

"There is always a buzz that goes around before the Olympics or the World Championships about how the conditions will be," Volpenhein said.

"In Athens it was the wind. People were worried we wouldn't be able to race."

Volpenhein, unlike Armstrong, said he would rather acclimate to the conditions than arrive right before his event.

"I think its better to just get into the environment -- your body will adjust. I think what is dangerous is not dealing with the initial shock that any environment is going to cause."

Volpenhein said he doesn't think it will give anyone an unfair advantage.

"The way I see it is that it's something you can't really change," Volpenhein said. "Everybody racing is going to be in the same environment."

For coach Harmon, part of the struggle will be to balance the athlete's desires to go out and live the Olympic experience, with what is best for performance and health.

Staying inside, and out of the polluted air, as much as possible will become a priority once events start, even if it's not what the athletes had in mind.

"I would hate for us to lose a match because one of our players couldn't play at their best because of respiratory issues," Harmon said.

-- By Talea Miller, Online NewsHour