PICTURE SPECIAL: Olympic Stadium shrouded in smog as pollution levels soar ahead of Beijing Games

The level of pollution in the Chinese capital has been one of the major concerns since it was awarded the Games seven years ago.

Beijing's bid included a commitment that the city's air would meet World Health
Organisation standards by the time the Olympics began.

Wish you were here? Thick smog blankets Beijing with the Olympics just 30 days away

Car trouble: Too many vehicles are choking Beijing

But, using a handheld detector to test for airborne particles known as PM10, the BBC found the air there failed to meet the WHO's air quality guidelines on six days out of seven.

PM10 particles are caused by traffic, construction work and factory emissions, and are responsible for much of Beijing's pollution.

The BBC found that on one of the days tested, the pollution reading was seven times over the WHO's air quality guideline, whereas readings taken in London - the site of the 2012 Games - all fell within acceptable limits.

Beijing officials have previously insisted they will fulfil their clean-air promise.

Shrouded in mystery: The main Olympic Stadium

Hazy days: Cars line the road approaching the Olympic Stadium

The city's air is expected to begin clearing this month as strict, two-month pollution controls come into force July 20.

Factories and heavy industry in several provinces around the capital will be
temporarily shut down, and up to two million vehicles will be taken off the roads using an even-odd plate registration system.

International Olympic Committee president Jacques Rogge has previously warned
some outdoor endurance events lasting more than an hour will be postponed if Beijing's air quality is found to be poor.

The IOC remain hopeful the air quality in Beijing will improve markedly leading
up to the Games.

Now this is what we want: International Olympic Committee Coordination Commission Chairman Hein Verbruggen explains to Chinese officials that clean air looks like this and cannot be cut with a knife

Soldiering on: A Chinese guard watches over proceedings in Tiananmen Square as the smog closes in

Hein Verbruggen, chairman of the IOC's co-ordination commission for Beijing 2008, said: 'Here in the Chinese capital you can now really sense the excitement and anticipation. The city feels ready; it looks ready, with the stunning venues all completed.'

He added: 'A very small number of open issues remain - such as some matters
with broadcasters and our need to see how temporary measures in the city will
make an impact on air quality.

'But across the board ... we are satisfied. When athletes, sports officials,
spectators and media arrive in this city over the coming weeks, I have no doubt
they will be impressed when they see things with their own eyes; and they will
be touched by the warmth of the welcome the Chinese people will show them.'

Exhausted: Endless traffic is turning day to night in Beijing

Down with this sort of thing: Taxis line the route to Beijing airport, increasing the smog factor