As thousands of athletes prepare to breathe deeply in one of the world's most polluted cities, one group of Olympic competitors is contemplating a special challenge.

A startling number of elite athletes have some type of asthma – some studies suggest 20 percent or more, depending on the sport. In this Olympics, many of them will have to perform at their peak in potentially choking air, with airways already prone to spasm and narrow.

Athletes and doctors alike have been worrying about dirty air in Beijing and other Olympic sites since China was chosen for the 2008 Games.

Read the complete story at sacbee.com