BEIJING - Beijing’s pollution is increasing the likelihood some Olympic events may be postponed, though special restrictions may help keep the skies clean, the International Olympic Committee said Thursday.

With less than 10 months to go before the 2008 Olympics, air pollution emerged as one of Beijing’s biggest headaches. A report by the United Nations Environment Program criticized Beijing’s cleanup as slow, noting some pollution exceeded World Health Organization standards.

In an overall positive assessment of Beijing’s preparations, an IOC inspection team said air quality was a major concern and it was monitoring the situation.

Inspection team leader Hein Verbruggen said the impact of pollution on athletes’ performance was a specific concern.

“The air quality is a big problem,” he said.

IOC president Jacques Rogge had warned in the past that pollution might force some outdoor endurance events to be delayed.

Verbruggen and other IOC officials said they were confident that measures such as traffic controls should reduce pollution. But if that fails, some events would be delayed.

“You might wait a day or two but it is something that we’re used to,” Verbruggen said. “It is a normal standard procedure that we have.”

Organizers have dwindling options to combat pollution ahead of the Aug. 8-24 Olympics. Some countries are delaying their teams’ arrivals in Beijing until the last possible moment to protect their athletes. But competition times have limited leeway.

Rogge underscored the IOC’s concerns in a speech saying that athletes “need clean and healthy conditions in which to train and compete.” But he did not read out a warning to Beijing contained in the prepared text that said “time may be running out.”

China has one of the world’s fastest-growing economies, but its cities pay for it with choking pollution. Beijing is often blanketed by a gray haze, some from coal-fired industries, others from the soaring numbers of cars.

“Extensive use of coal, the city’s geographical location and a growing number of motor vehicles means the pace of improvement in Beijing’s air quality is slow,” said Eric Falt, who heads the U.N. Environment Program’s sports and environment project.

Falt said small particulate matter — fine particles of pollution that can easily pass into people’s lungs and harm health — were “particularly worrying.”

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The U.N. report found that the average level of small particulate matter in Beijing’s air in 2006 was eight times higher than the level recommended by the World Health Organization.

Other forms of air pollution — sulfur dioxide, nitrogen dioxide and carbon monoxide — rose or failed to drop in 2006 following three years of decline, according to the report, which was based on Chinese government statistics.

“(China) never committed to reaching those specific WHO standards within the time frame of the games,” Falt said.

Beijing’s Olympic organizers have said contingency measures, such as the selective banning of cars or temporary closure of factories, will have to be used to clear the skies — pledges that were reiterated by officials Thursday.

Verbruggen and other IOC officials defended Beijing’s efforts, saying organizers have spent more than the $12 billion they promised for pollution control, but growth has outpaced all predictions when the city won the bid in 2001.

“As far as we’re concerned, there is no blame to be addressed,” Verbruggen said at that news conference. “We all know that the development of this country and the development of this city has accelerated or enhanced the air quality problems.”

The U.N. report was generally positive about other environmental aspects of the preparations, praising the Beijing organizing committee’s efforts in waste management, transportation and water treatment.

Solar power will be used at venues and the Olympic village, and organizers have made an “extraordinary achievement” in avoiding chemicals that damage the ozone layer, the report said.

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