"The Beijing Olympics will be a good example of what can be done with the Games in a city."Despite the IOC's assurance, members of the U.S. cycling team were seen wearing masks Tuesday afternoon when they arrived at Beijing's capital airport.

"For the general visitors, I don't see the need for it honestly unless there are very uncomfortable days and you are sensitive to those conditions," Ljungqvist told a press conference.

Ljungqvist said that air quality data from 27 measurement sites around Beijing since July 27 showed "encouraging" results.

"Although the first two days suggested some measurement a little above the interim target, they have now gone down and we are steadily below the interim target," he said.