BEIJING - A white haze hung over Beijing with one day to go before the Olympic opening ceremonies.

The good news? It's not as bad as it looks, according to the Canadian Olympic team's medical and weather experts.

The fog is generated by heavy humidity rather than skyrocketing levels of pollution, according to COC climatologist Doug Charko.

"That's what gives it that white appearance," Charko said Thursday. "It's the early stages of fog. If you were on a tropical island with the best air quality, you'd get that hazy appearance because of the humidity."

The temperature was above 30 C with 85 per cent humidity.

Smog has been a burning issue in Beijing heading into the Olympics and the organizing committee shut down factories and pulled half the city's 3.3 million vehicles off the roads to combat it.

Four U.S. cyclists caused a stir when they left the Beijing airport wearing masks Wednesday. The athletes have since apologized to the organizing committee.

Masks have been sparse among the athletes.

"I will say all those countries -- the Americans, the Japanese, the British -- that spent a lot of time talking about masks, their athletes aren't using them," said Canadian chief medical officer Bob McCormack.

Road cyclist Michael Barry says he's seen only one or two athletes wearing masks.

Athletes in outdoor endurance events would be most affected by dirty air. Barry was feeling no ill effects after riding 130 kilometres at the Olympic course, which is 46 kilometres from downtown Beijing.

"I wasn't coughing," said the Toronto native. "The course is outside the city and I notice the pollution more in the city because my eyes sting."

The rowing venue is about an hour's drive outside the city centre and the air is clearer.

"I'm convinced that this more of a haze than a smog because we've had no respiratory issues," said rowing coach Al Morrow. "If it was really bad smog, especially when you're doing a hard workout, if there was a problem with the air quality, we'd have respiratory problems.

"We haven't noticed anything."

Charko takes daily air quality readings, which measure the combination of nitrogen oxides, sulphur oxides and ozone in the air, plus particulant matter, which is basically fine dust.

He said from Monday to Wednesday the air quality was in the mid-80's "which is average for what Beijing has been getting."

"It's equal to a bad day in southwestern Ontario," Charko explained.

But Whitehorse weightlifter Jeanne Lassen is accustomed to the more pristine Yukon air.

"I do feel it," she said. "I don't know if it's affecting my performance at all but I definitely feel dirty all the time and like I want to cough but I don't have to."

Charko received readings as low as 27 last week and said the skies over Beijing improve when there's a north wind.

Unfortunately for the opening ceremonies, that's not in Friday's forecast with temperatures as high as 34 C and a southern breeze predicted.

In data gathered during five previous visits to Beijing, the Canadian team's environmental physiologist determined the country's athletes were not in danger of damaging their lungs in the two weeks or less that they will be competing in the city.

"The bottom line is, and other countries have found the same thing, there wasn't an impact on ventilation as a result of being here for a couple of weeks," said Dr. Jon Kolb. "It's a much different situation long-term. There is higher incidence of cardiopulmonary disease and lung challenges for people who live here their whole life."

Athletes were tested prior to their arrival for respiratory ailments, he added.

"We've kind of cased out those individuals we think might be at risk and for those individuals that show an exercise-induced asthma, we continue with lab testing and if it's appropriate they end of getting a therapeutic-use exemption for an inhaler," Kolb explained.

Heat and humidity might end up being the real challenge Canadian athletes have to overcome.

The women's soccer team already experienced that in its preliminary match against Argentina on Wednesday.

"You start to feel a bit more tired earlier on in the game than you would maybe in another environment," said striker Kara Lang. "It's something both teams have to deal with so I don't think it's going to necessarily change the game too much or the outcome of the game."

Kolb says athletes and coaches were told what to expect a long time ago so they could prepare strategies to keep cool.

Some athletes have worn ice vests while members of the women's softball team have chosen to drape themselves in ice-coated towels.

Athletes and teams were encouraged to get to Beijing and train and compete as much as possible in the months leading up to the Games so they'd know what was coming.

Most have held their pre-Games training camps elsewhere in the country before arriving in Beijing to get acclimatized.

The white shroud over the city looks ominous, but the Canadian team's top doctor says it could be worse.

"It looks terrible," said McCormack. "We've actually had days where it's been much clearer, but the pollution count has been higher.

"In actual fact, our athletes and mission staff are not having the same symptoms that we've had in previous visits with scratchy throats and congested nose and the cough. They've been uncomfortable in previous visits and they're not experiencing that this time."