BEIJING, Aug. 9 (Xinhua) -- A senior United Nations official urged the world on Saturday to allow some time for developing countries to improve their air quality.

    "The reason why the World Health Organization have intermediate standards [about the impact of pollution on health] is that developing countries need time," Achim Steiner, Executive Director of the United Nations Environment Program (UNEP).

    He also argued that air pollution has been part of the Olympic history for as long as he could remember. "It's not necessary to look out of the window and make a judgment based on your visual image."

    In fact, at the Los Angles Olympic Games, more than 90 percent of the days were rated as unhealthy by the air quality standards of the United States. At the Games in Athens and Seoul, air quality was also an issue of concern, according to Achim.

    The International Olympic Committee (IOC) had made decisions whether the air was sufficiently good and the issue was being managed properly, he added.

    He said the UNEP is working with the IOC to develop the standard for the green quality of Olympic cities, so that people can assess and compare to the standard in terms of environmental performance and improvement for competing hosting cities.

    Achim spent two days going around the public transport system in Beijing, and visited the city's Environmental Protection Bureau and some environmental monitoring stations.

    He said Beijing had invested more efforts and resources than previous host cities and its measures had proved effective.

    "Perhaps there is only 5 percent of the broader picture of environmental issues being addressed. But millions of Beijing residents will benefit from the Games in terms of air quality and more attention should be given to this [improvement]."

    He also said that athletes with masks in Beijing should not be blamed. "If you read the reporting of the air quality in Beijing in the last few weeks, every athlete has reason to concern because it's the moment of their dreams."

    "They come to Beijing for the Olympics and maybe have nine or ten seconds to win the big prize."