According to IOC Chair of the coordination commission, Hein Verbruggen, there is a small risk of damage to health for athletes competing in events lasting for more than one hour, such as the marathon and cycling road races. This is because of Beijing's poor air quality - which has alread led to marathon record holder Haile Gebrselassie, who suffers from asthma, saying that he will not compete in the marathon event.
Beijing is one of the most polluted cities in the world and, in spite of a multibillion dollar clean up over the past decade, air quality is a concern for many athletes intending to compete in the games.
According to Verbruggen they might delay events by one or two days if air quality is particular bad - which could lead to problems if, on the final day of the event, air pollution is too bad to stage the men's marathon. However, Verbruggen says that there is no risk of damage to health in events lasting less than one hour.
