The International Olympic Committee says Beijing's air pollution could force some outdoor events to be postponed at next year's Olympics in the Chinese capital.
A United Nations report issued Thursday criticized Beijing's progress on cleaning its air, 10 months before the Games begin in August.
An IOC Inspection team said air quality is a leading concern. Team leader Hein Verbruggen said the pollution's impact on elite athletes is of particular concern.
IOC President Jacques Rogge said some events - especially endurance events like marathon running or cycling - could be postponed to preserve the athletes' health. Neither Rogge nor Verbruggen said pollution is a threat to Beijing's hosting next year's Olympics.
The United Nations report said that the average level of pollutants in Beijing's air in 2006 was eight times higher than the level recommended by the World Health Organization.
The U.N. report was generally positive about other environmental aspects of Beijing's preparations, including waste management, transportation and water treatment.
China has one of the world's fastest-growing economies, but its cities have paid a high environmental price. Beijing often is covered in a shroud of haze and smoke from factory and automobile pollution.
Some information for this report was provided by AFP and AP.