Tourists put on their masks after they posed for souvenir photos as they visit Tiananmen Square on a severely polluted day in Beijing, China, Tuesday, Feb. 25, 2014. Pollution across a large swath of ... more 
Tourists put on their masks after they posed for souvenir photos as they visit Tiananmen Square on a severely polluted day in Beijing, China, Tuesday, Feb. 25, 2014. Pollution across a large swath of northern China worsened on Tuesday. (AP Photo/Alexander F. Yuan) less 
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Associated Press | Photo By Alexander F. Yuan
Mon, Feb 24, 2014 11:33 PM EST