BEIJING >> Air pollution in Beijing was so bad Friday that the U.S. 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 later deleted the phrase, saying it was an “incorrect” description and adding that it was working to revise the language to use when the air quality index goes above its highest point of 500, which means the air is considered hazardous for all people by U.S. standards.

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. Because of the bad air this year, we’ve had to cancel more games than ever before.”

Health experts say that breathing polluted air can affect respiratory functions and worsen problems for those with asthma or allergies.

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 hit the roads each day.

The capital underwent a massive cleanup in 2008 for the Olympic Games, such as planting thousands of acres (hectares) of trees in and around the city, but has since allowed some factories to reopen and lifted some traffic restrictions, bringing pollution levels back up.

“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. The health of Beijing residents is no less important than the health of those athletes who were here for a few weeks.”

“We can’t just expect wind, snow or rain to wipe out the pollution when it gets bad,” Ma added. “The city must take pollution more seriously and implement preventive measures.”

When China’s air pollution index, which measures four major pollutants, is under 100, China considers it a “blue sky day.”

According to the China Daily newspaper, Beijing experienced 285 blue sky days in 2009, compared to 274 in 2008.

But in the first half of this year, Beijing saw 140 blue sky days, six less than the same period the previous year, it said.