A child laughs as she passes by a smog-shrouded residential district in Beijing on Jan. 29, 2013. Extremely high pollution levels shrouded eastern China for the second time in about two weeks, forcing airlines in Beijing and elsewhere to cancel flights because of poor visibility and prompting government warnings for residents to stay indoors. (Associated Press)

Photo by: Ng Han Guan

A child laughs as she passes by a smog-shrouded residential district in Beijing on Jan. 29, 2013. Extremely high pollution levels shrouded eastern China for the second time in about two weeks, forcing airlines in Beijing and elsewhere to cancel flights because of poor visibility and prompting government warnings for residents to stay indoors. (Associated Press)