The Big Question: Is pollution going to choke the life out of the Beijing Olympics?

Why are we asking this now?

With less than a month to go until the Beijing Olympics, it's not just the athletes who are sweating. There are growing concerns that the host city has failed to meet its promises to resolve its appalling pollution problems, and that the city smog may damage athletes' health.

Despite a report by the Chinese government showing that levels of serious pollutants such as sulphur dioxide and COD (chemical oxygen demand), a measure of water pollution, both fell significantly last year, the grim pollution in Beijing is plain to see, obscuring the marvellous "Bird's Nest" Olympic stadium itself, and the futuristic Water Cube, which will host the aquatic events, in a yellow-tinged smog.

Meanwhile, environmental experts are working feverishly to clear a large smelly bloom of bright green algae from the sailing venue in Qingdao.

So will the air in Beijingbe breathable?

The Beijing Organising Committee (BOCOG) concedes that the city has a problem, and China failed to meet pollution-busting targets in 2006, but says its critics are only interested in creating "noise pollution". They insist everything will be all right on the night of the opening ceremony on 8 August. They say that all the measures they have taken to combat pollution will have ensured clean air for the athletes and the 3.5 million visitors expected in the city.

The International Olympic Committee (IOC) has spoken up in support Beijing's efforts to combat pollution, though their remarks seem to ahve been made through gritted teeth. It has had to concede that this Olympics will not be a great one in terms of securing records in endurance events such as long-distance running. The IOC's chief inspector, Hein Verbruggen, said Beijing "looked ready" but added that the IOC needed "to see how temporary measures in the city will make an impact on air quality".

So have Beijing's critics got a point?

China has pitched the Olympics as the "Green Games" to showcase the country's efforts to combat pollution and encourage sustainable energy use. However, Beijing is one of the world's dirtiest cities, choked with smog that is often two or three times the maximum allowed for by the World Health Organisation. China is a developing country, and home to the factories where most of the world's industrial goods are now made; pollution is a sorry by-product of this development. The World Bank says China is home to 16 of the world's 20 most polluted cities.

The United Nations Environmental Programme (UNEP) warns that air quality remains a problem, and it is particularly worried about the high levels of small particulate matter (PM10), which are sometimes at more than double recommended safe amounts. Having sneaked a hand-held detector to test for PM10 particles, a BBC reporter found that Beijing's air failed to meet the WHO's air quality guidelines for PM10 on six days out of seven. Last year, Beijing just outdid its target of 245 "blue-sky days" – by a single day.

What's being done to stop the pollution?

The Games organisers are spending vast quantities of cash to get the air breatheable in time – £8.9bn on environmental programmes to combat pollution, plus there are the hidden costs to the city's economy of measures such as the odd-even licence plate system, which starts on 20 July, and should lead to about half of the city's 3.3 million cars going off the roads for the duration of the Games.

The capital's top five power plants, all coal-fired, are committed to cutting emissions, and Beijing has demanded factories in surrounding provinces stop work or cut production to clean the city's air. Coal-burning furnaces are being converted to natural gas in the city centre; millions of trees are being planted and dust clouds from building sites kept under control. The government says that the measures are working – sulphur dioxide emissions, which cause acid rain, fell by 4.7 per cent last year, while COD dropped by 3.2 per cent in 2007, the environmental watchdog's official publication reported.

Should the athletes be worried?

An endurance athlete inhales up to 150 litres of air a minute, about 10 times that of an average office worker, so marathon runners and cyclists in the road races have reason to feel anxious. Some 24 countries, including Canada, Germany, France, Israel and the United States, have decided to hold training camps in Japan instead of Beijing before the Olympics, and the Australian cyclist Stuart O'Grady has spoken out about the "insane" health risks he and his fellow-cyclists face. The great marathon world record holder Haile Gebrselassie of Ethiopia has pulled out of the event, believes that the pollution could affect his asthma, while the governing body for athletics in Australia said that it did not want its athletes marching in the opening ceremony because of the pollution.

No one wants a repeat of the marathon in St Louis in 1904, when only 14 of the 32 competitors finished the course through the city's dirty streets, and one American runner died after inhaling too much dust.

In other respects, are the Games on track?

Absolutely. In marked contrast to the Athens Games of four years ago, preparations are already nearly complete for much of the Olympic infrastructure. At the Olympic sites, thousands of workers are putting the final coats of paint and tightening the nuts and bolts on what has been a £20bn programme of urban renewal. The 31 venues for the Games are ready, and the new road system and subway network are on stream.

The organisers will be expecting more criticism as the Games approach of how China has fallen short of the media freedoms and human rights improvements it promised to win the Games. Murmurs of discontent are still coming from Tibet, but the hardware for the Olympics is pretty much there.

Is there a worst-case scenario?

As things stand, the pollution situation looks dire, and if China is transformed into the Dirty Olympics, it would scupper the billions of pounds that the Games' organisers have spent in transforming the city. A key element in hosting the Games is the chance for China to open up to the world and demonstrate its emergence as a global economic power. If Beijing fails in that aim because of the city's atmosphere, it would be a disaster. It would also be a major blow to the dreams of millions of ordinary Chinese who are frantic with excitement at the prospect of playing host to the biggest sporting event in the world.

So are the Games under a cloud?

Yes...

* There is no sign that pollution in the capital city is easing up at all – just look out the window

* Taking half of 3.3 million cars off the roads still leaves an awful lot of cars on the road

* Controlling pollution on such a scale in such a short period of time is too big a job

No...

* The government says air and water pollution indicators are showing less pollution

n* Taking half the cars off the streets did reduce local pollution in a test run last year

* The Communist Party has single-party rule, and it can bring the whole country to a standstill to reduce pollution if it needs to

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