Air pollution in Beijing was so bad yesterday that the United States Embassy, which has been independently monitoring air quality, ran out of conventional adjectives to describe it, at one point saying it was "crazy bad."

The embassy deleted the phrase, saying it was an "incorrect" description and added it would revise the language to use when the air quality index goes above its highest point of 500, which means the air is hazardous for all people if the US standards adopted.

The hazardous haze has forced schools to stop outdoor exercises, and health experts asked residents, especially those with respiratory problems, the elderly and children, to stay indoors.

"We've canceled 10 days worth of games since August," said David Niven, chief operating officer of China ClubFootball, which runs extensive youth and adult football leagues in Beijing. "If the air is above 240 (on the air quality index), some of the schools will ask us to move football games indoors or cancel them altogether."

Experts say Beijing's frequently bad air has been even dirtier recently because a growing number of factories and villages on the outskirts of the city are burning coal for the winter and more than 1,200 new cars are hitting the roads each day.

"If the city's planning was better, people from the outskirts wouldn't have to commute for hours each day," said Ma Jun, director of the Institute of Public and Environmental Affairs in Beijing. "Beijing needs to place more of a priority on the environment."