Gebrselassie would be a favorite in the marathon on the final day of the Olympics, but health issues may rule him out. Gebrselassie won two 10,000-meter Olympic titles and holds the world record in the marathon.

"We have our doubts," Jos Hermens, Gebrselassie's manager, said today in a telephone interview. "It is an extremely dangerous marathon."

On a normal day, Beijing's pollution exceeds by nearly five times the safety benchmark set by the World Health Organization.

"He has a bit of a lung condition as well," Hermens said about Gebrselassie's pollen allergy. "So, all in all, is it worth it?"

Hermens is worried about heat stroke, which can leave lasting damage for an athlete. The 10,000 meters is less punishing, and Gebrselassie will likely try to qualify for the strong Ethiopian team at the shorter event.

Hermens' management team looked into the hottest marathon races over the past 20 years and found that many of the top finishers never really recovered for the rest of their careers.

That concerns the 34-year-old Gebrselassie.

"What he says is: 'Great if I win, but if it means the end of my career then I really don't feel like it,"' Hermens said. "He is convinced he still has a real chance" to win the marathon at the 2012 London Olympics.

Gebrselassie smashed the marathon world record last September with a time of 2 hours, 4 minutes, 26 seconds in Berlin, and ran the second fastest time Friday (2:04:53) when he won the Dubai race.

Those conditions will not compare to those in Beijing, though.

International Olympic Committee president Jacques Rogge has repeatedly said some competitions might be postponed if the Beijing air is too polluted.

After winning the 10,000 at the 1996 Atlanta Olympics and 2000 Sydney Games, Gebrselassie finished fifth in Athens in 2004 in a race won by teammate Kenenisa Bekele.

The marathon has a special aura in Ethiopia since barefoot runner Abebe Bikila won the 1960 Rome marathon and repeated the feat, with shoes, in Tokyo four years later.

"Of course, it is a dream for him as an Ethiopian to become a marathon champion after Bikila, but he can still do it in London, too," Hermens said.

Apart from his Olympic golds, Gebrselassie has four 10,000 world championship titles and has broken two dozen world records.

In an effort to cut pollution, Chinese authorities plan to shut down factories and take cars off Beijing's streets during the Olympics.