The cloud hanging over the Olympics

How bad is the air in Beijing?
It's pretty awful. Beijing's thick, nasty combination of carbon monoxide, sulphur dioxide, nitrogen dioxide, and assorted particulate matter routinely fails China's own relatively lenient air quality legislation; it fails the guidelines of the World Health Organisation (WHO) several times over. Often a dense, yellowish haze blankets the entire metropolis - or 'Greyjing', as it has been nicknamed. Researchers estimate that more than 400,000 Chinese people die prematurely from air pollution annually, with as many as 25,000 deaths in Beijing alone.

Why is there so much smog?
The problem dates from well before China's recent, ferocious economic development and is by no means confined to Beijing. In his brutal mid-century remodelling of the city, Mao Zedong tore down temples and palaces, declaring that he wanted to "look out from Tiananmen Gate and see smokestacks". In the past decade those factories have been running overtime. Since China was awarded the Olympics in 2001, the nation's industrial output has increased 80 per cent. Most of this growth has been fuelled by primitive, coal-fired furnaces and boilers, which spit out tons of choking hydrocarbons. Car ownership has also tripled in the last decade, with 3.3m cars now on Beijing's roads. Natural factors are at work, too. Dust storms from the Gobi Desert fill the air with soil, and since mountains surround Beijing on three sides, pollutants tend to stay trapped there, like soup in a bowl.

What does all this mean for athletes?
Considerable unease. The run-up to the Games has been marked by dire warnings and fears that the pollution could hamper athletes and harm spectators alike. Last year a WHO air quality expert told the BBC that people with heart and lung problems should not visit Beijing at all. Haile Gebrselassie of Ethiopia, the world's fastest long-distance runner, announced in March that he would not be running in the marathon, although he will still take part in the 10,000m. "It's going to be the hardest marathon in history," he said. "I'd love to go for it, but health is my first priority." The air is so dirty you can taste it, says US triathlete Jarrod Shoemaker. "You can feel the grit in your teeth." But there have been some unexpected benefits: the entire Australian Olympic team, for instance, was tested for asthma and several athletes turned out to be carrying the disease unawares. "These people had not had treatment and some are getting treatment now, and they are finding extra petrol they never realised they had," said Peter Baquie, the team's head doctor.

Is China dealing with the issue?
It's certainly trying. When Beijing won the Games, it promised to meet the WHO's air quality standards, and has spent $17bn on that effort. In advance of the Olympics, authorities have shut down or relocated 200 notoriously polluting plants and factories. They have also temporarily closed 1,000 coal mines and 144 gas stations. A total of 44,000 chimneys have come down. From 20 July, half of the city's cars were banned from city streets for the duration of the Games, and all construction was halted. A range of extra closures and traffic restrictions, to be enforced in case of emergency, are also on standby and smog-clearing pellets have reportedly been fired into the sky. "After we fully implement all of the Olympic measures," said environmental official Zhang Lijun, "it will be no problem for the air quality to meet acceptable standards."

Is it meeting those standards?
To some extent. Last year Beijing had 246 'blue sky' days of low or moderate pollution, up from only 100 in 1998. The Beijing Olympic Organising Committee says pollution levels have dropped 13.8 per cent since 2001. For most of June, pollution in Beijing averaged 87.75 on a government index of 500. That's a level that Chinese officials consider safe, though still double the typical levels in most Western cities. In July, the Sunday Times found that Beijing's pollution was five times worse than levels deemed safe by the WHO, while last week the BBC found levels of particulate matter six times over the limit. Beijing's Environmental Protection Bureau rates the current air quality as 'fair'.

How have athletes reacted?
Many stayed clear of the capital for as long as possible. The 'holding camp' for the British team was the gambling resort of Macau, where athletes tried to adapt to the heat and humidity. The US track-and-field team stayed in the eastern port city of Dalian, nearly 300 miles from Beijing, until the last minute, while Australia's track-and-field team plans to skip the opening ceremony altogether. The International Olympic Committee has promised to change the dates and venues of endurance events, such as the triathlon and marathon, if smog intervenes, but most teams are putting on a brave face. "It's not a concern to us," said Simon Clegg, chef de mission of Team GB. "The expert advice that we are getting is that the situation continues to improve."

Will the air affect the Games?
It's anyone's guess. Officials insist that the vehicle restrictions and industrial shutdowns will cut pollutants by as much as 40 per cent. But these restrictions have just begun, so the impact on Beijing's air has yet to be seen. The International Olympic Committee will monitor air quality levels every day during the Games, and its president, Jacques Rogge, has compared smog to the threat of bad weather, which is hardly new. "If the atmospheric conditions are too cold in crosscountry, or if it's too hot for a marathon, we change the dates," he says. Meanwhile, the presence of 20,000 foreign journalists will mean constant (if disputed) updates, and lots of pictures of grey weather, something which has already annoyed Beijing's environmental officials. But the authorities will be unmoved by photographic evidence. "Pictures cannot reflect reality," the deputy director of Beijing's environmental agency told the Xinhua news agency. "They are not accurate." ·