MELBOURNE, Australia — The Australian Olympic Committee has begun screening some athletes for asthma in the lead up to the Beijing Olympics and the higher-than-normal pollution levels in the Chinese capital.

Australian officials said today that asthma testing for "high-risk prospective" athletes on the 2008 team, including triathletes and long-distance runners, was being conducted in an attempt to minimize the impact of air pollution on their performance, as well as identify those at risk.

Beijing is one of the world's most polluted cities. A mix of particulate matter, carbon monoxide, sulfur dioxide and nitrogen dioxide often blankets the city at levels five times higher than World Health Organizations safety standards.

"Many athletes may have underlying mild asthma or exercise-induced asthma, but not be aware of its presence, as the symptoms are 'normal' for that athlete when working hard," said Dr. Karen Holzer, an air quality specialist and a 2008 Australian team doctor.

"Athletes involved in sports requiring training or competing for prolonged periods in the outdoor air such as triathletes, middle and long distance runners, cyclists, rowers and kayakers, in addition to swimmers, of whom a significant proportion have asthma, are being screened for the presence and severity of underlying asthma or exercise-induced asthma."

Holzer said athletes identified as being at risk would have their cases monitored and have preventative measures put into place before they leave for Beijing.