It's the first thing one notices on the 20 kilometre drive from the airport into the city centre.

It's been a hot topic ever since China were awarded the Olympic Games more than five years ago.

And it could still undo all the immaculate preparations made by thousands upon thousands of Chinese workers to ensure that Beijing is more than a worthy choice to stage the greatest show on earth.

Smog. You can see it, you can smell it, you can breathe it.

Olympic organisers, desperate to convince the rest of the world it won't affect the Games, claim that overcast, hazy skies don't equate to pollution or poor quality air.

Visitors who have been in the city for some time might disagree. At times, looking out of a hotel window across the city, it's difficult to pick out other high-rise buildings less than half-a-mile away.

Despite the shutting down of factories, stopping construction work and taking cars off the road, measures implemented by the Beijing Olympics Organising Committee (BOCOG), it still might be a case of "too little, too late."

With a spectacular opening ceremony at the newly-built National Stadium - aptly named the 'birds nest' - scheduled to kick off the Games today, there remains a real concern that smog will affect athletes, particularly those participating in outdoor endurance events, especially the marathon.

And there's still a provision that 26.2 mile race could be held elsewhere if conditions worsen over the next week. But it's highly unlikely that events such as the triathlon, in which Bermuda's Flora Duffy will compete, will be moved at this late stage.

Duffy, however, is the only Bermuda competitor who might be affected as she attempts to negotiate the 1.5 km swim, 40 km bike ride and 10k road race.

Swimmers Kiera Aitken - who will be the first of Bermuda's team to compete on Sunday - and Roy Allen Burch will be sheltered under the roof of the magnificent National Aquatics Centre and long jumpers Tyrone Smith and Arantxa King aren't likely to be bothered as they build up a head of steam as they burst into the sand pit.

Equestrienne Jill Terceira, who will carry Bermuda's flag at today's Opening Ceremony, heads for Hong Kong, venue for all horse-riding events.

Hong Kong also has its own poor quality air problems, but again that should have little effect on the showjumpers.

As late as yesterday, Sarah Liao Tung, environmental advisor to the BOCOG, was insisting that smog would not be a problem. Quoting weather experts, she said it was unlikely that the Games would experience "a stagnant atmosphere that would trap pollutants" and in turn deteriorate air quality. Others, it seems, have less confidence.