Beijing smog forces Gebrselassie to withdraw from Olympic marathon

The Ethiopian marathon world record holder — an asthmatic — said the 26-mile race was too much of a risk, although he will still run in the 10,000 metres.

His dramatic withdrawal is a huge embarrassment for the Chinese authorities and they will now be worried that other athletes — including women's world record holder Paula Radcliffe, who also suffers from the respiratory disease — will follow suit.

Radcliffe, who last week withdrew from the London marathon due to injury, has said she may have to change medication to prevent an asthma attack during the Beijing race in August.

Gebrselassie said: "The pollution in China is a threat to my health and it would be difficult for me to run 42km in my current condition.

"But I am not pulling out of the Olympic event in Beijing altogether. I plan to participate in the 10,000-metre event."

Saying that pollution "would be a hazard to athletes, seriously affecting their performances", Gebrselassie called on China to deal with the problem.

Last year, tennis champion Justine Henin said she would not be defending her title because as an asthmatic she considered conditions too dangerous.

The International Olympic Committee have reacted to concerns over athletes' health by warning Games organisers that events in outdoor endurance sports such as the marathon and cycling distance races may have to be postponed.

Medical experts from the IOC will continue to monitor air quality and weather reports and reserve the right to delay these events by several hours, but the IOC are now satisfied that events will not have to be moved to another day.

Beijing authorities have invested large sums in anti-pollution measures, including moving factories out of the city centre and taking a third of the city's three million cars off the road.

However, pollution levels in Beijing were measured at 12 times the levels recommended by the World Health Organisation last December.

Such is the concern about pollution that the British Olympic Association have had special face masks — thought to be opposed by the IOC — developed for athletes. However the BOA have yet to decide whether they will back the masks being used in training or competition in Beijing.

A BOA spokeswoman said: "We have a strategy in place that looks at the environmental problem in Beijing and we are confident that if the situation becomes too bad for athletes then the IOC will take measures to deal with that."