Beijing is one of the most polluted cities in the world and, despite a $17.12 billion clean-up over the last decade, air quality remains a concern for many athletes coming to the Olympics.
"There can be a risk, but it's not big, for endurance events that last longer than an hour," Verbruggen told Reuters on the sidelines of the final inspection of preparations for the Games.
"In that case, we are developing a Plan B.
|"We might delay certain events for a couple of days."|
"We might delay certain events for a couple of days. But to do that it must be very bad."
Organisers could face a dilemma if pollution levels are too high to stage the men's marathon on the final day of competition.
For events that take less than an hour to complete, Verbruggen said there was no chance of any damage to the health of an athlete.
"The Chinese together with our medical commission have done an excellent job," the Dutchman added.
"They have scientifically proved there is no risk for the wide majority of sports."
Kevan Gosper, IOC press commission chief, said Beijing's investment had already delivered better air quality and he was confident that contingency plans would be effective.
"At Games' time, they've got many levers to pull... they've given us a great list of details of what they propose to do," Gosper said.
"Every Games I've been to as an administrator since 1984, we've worried about air quality... in all cases, things turned out to be normal."
Beijing plans to take about half of its 3.5 million cars off the roads and partially shut down industry in the capital and five surrounding provinces for two months for the Olympics and Paralympics.