Between July 20 and Sept. 20, Chinese officials say there will be a freeze on construction. Nineteen industries -- including steel and petroleum plants -- will have to reduce emissions by 30% this summer or risk closure. Quarrying, cement production and spray painting outdoors will come to a halt.

Maybe half the city's 3.5 million vehicles will be pulled off the roads at times.

Beijing is one of the world's most polluted cities. A brew of particulate matter, carbon monoxide, sulfur dioxide and nitrogen dioxide hangs in the city at levels five times higher than World Health Organization's safety standards. It is well beyond any pollution levels in the San Joaquin Valley.

Will the last-minute measures be enough for world-class athletes to perform? Some people doubt it. But Chinese officials assured Olympic officials this week that the air will be fit for the games.

Said Du Shaozhong, deputy director of the city’s Environmental Protection Bureau, during a news
conference: “Just tell everybody they don’t have to worry.”