For millions, it is a daily irritation as their breath shortens at the end of a jog around the block or a session in the gym. For Olympic athletes, an uncomfortable wheeze can become a life-threatening last gasp for breath as they push their bodies to the limits of human endurance. Which is why Haile Gebrselassie, the world's fastest marathon runner announced this week that he is not willing to take the risk, even for the sake of a gold medal.

Gebrselassie has unwittingly become the voice of hundreds of athletes who will be faced with competing in one of the most polluted cities on Earth when they travel to Beijing for the Olympic Games in August. The veteran Ethopian, like a quarter of the British Olympic squad (including Paula Radcliffe, our own marathon gold medal hope) suffers from exercise-induced asthma.

The Chinese authorities have waged a huge campaign against polluting factories, forcing some to close and others out of the city, and are threatening to ban cars from the traffic-choked streets for the duration of the Games to try to eradicate exhaust fumes. They are even considering “seeding” cloud formations to induce rain to wash the early-morning air in the hope that athletes can run, jump and throw unhindered. Whatever the assurances, they were not enough for Gebrselassie, arguably the greatest distance runner of all time. This is a man with nothing to prove and no reason to back out of an event for which he would be an automatic favourite. As a child, he used to run six miles to school from the family farm near Asela and by the age of 16 was running against adults. Accolades and money have rolled in since then: six World Championship and Olympic gold medals and enough prize-money and endorsements for him to start a business with 400 employees and build two schools at home in Ethopia.

Gebrselassie lives in a rarified atmosphere of celebrity at home in Ethopia, where he has built a palatial, marble-floored villa, high in the hills where there is clear air above the capital, Addis Ababa, for his family. He is a figurehead for his nation, providing employment, setting up numerous charities and inspiring hundreds of youngsters to run.

With his 35th birthday next month, Gebrselassie knows that athletes in the speed events will be less affected by Beijing's smog, while marathon runners will be sent out on more than 26 miles of Beijing streets, sucking in the same air that smoke-belching buses and lorries were rattling along only hours before.

Which is why he may opt to run the 10,000 metres in Beijing, a sprint by Gebrselassie's standards. By the standards of millions of fellow asthma suffers, though, 10,000 metres at full pelt would be a wheeze-inducing lung buster to avoid.