But performance levels fell as exposure levels increased, suggesting that athletes should avoid air pollutants before competing, rather than trying to condition themselves by training in them, he said.
"My recommendation would be not to go running behind dump trucks," Rundell said. "If you just show up the day of the race, you're probably better off."
Beijing's unhealthy air is a byproduct of the city's geography, climate and industrial progress.
Like Baltimore, Beijing is near a coast and lies about the same distance north of the equator. But there the similarities end, said Russell Dickerson, a University of Maryland professor who has been to Beijing to measure air quality three times.
Unlike Baltimore, Beijing has nine months of dry weather when winds from the west bring in dust from the Gobi Desert, he said. The dust mixes with debris from construction projects, factory emissions and motor fuel exhaust to create a hazy mix.
During the warmer summer months, winds usually shift, bringing in moisture from the ocean. But when the wind dies down and it doesn't rain, the still air combines with industrial pollutants to create a terrible haze, Dickerson said.
"Over the past decade, it's definitely gotten worse," he said.
Dickerson said he has yet to feel any ill effects of trips to Beijing to measure air quality in 2004, 2005 and 2006 for the Chinese National Academy of Sciences. But an asthmatic colleague did have an attack and had to stay indoors at times.
Pollutants in Beijing's air include sulfur dioxide, carbon monoxide, nitrogen dioxide, particulate matter and ozone. Ozone is produced when car exhaust and other pollutants are heated by the sun. Because of its mix of sun and cloudy days, Beijing's ozone problems are no worse than Baltimore's, Dickerson said.
But the city of 17 million ranks 16th worldwide for particulate matter - an especially nasty pollutant composed of manmade and natural particles from industrial exhaust, bacteria, fungi and pollen as tiny as 10 microns. By contrast, a human hair is about 100 microns wide.
When inhaled, the tiny particles seep into the lungs, inflame them and cause coughing, sinus problems and asthma attacks, said Dr. Gregory Diette, a pulmonologist at the Johns Hopkins Obstructive Lung Disease Clinic.
"A lot of Olympic spectators will also be at risk," he said.
His advice to anyone with asthma headed to Beijing? Bring your medication.
dennis.obrien@baltsun.com
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Attack
16 border police killed in China. PG 3A
