Last updated at 12:55 11 March 2008

Haile Gebrselassie has pulled out of the

Olympic marathon because of the threat posed to

his health by air pollution, raising concerns that

other top runners may also quit the Beijing race.

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.

Smog fear: Gebrselassie seen here winning in Berling, will not be racing in Beijing

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."