A person wears a mask while crossing a bridge in Beijing on Monday, December 19. A gray haze of smog descended on Northeast China over the weekend, and China has issued a red alert for 23 cities.
A person wears a mask while crossing a bridge in Beijing on Monday, December 19. A gray haze of smog descended on Northeast China over the weekend, and China has issued a red alert for 23 cities.
Andy Wong/AP
Tourists visit the Zhan Qiao, a wharf in Qingdao, China, on December 19.
Tourists visit the Zhan Qiao, a wharf in Qingdao, China, on December 19.
VCG/Getty Images
A cyclist rides in heavy smog in Lianyungang, China, on December 19.
A cyclist rides in heavy smog in Lianyungang, China, on December 19.
VCG/Getty Images
A pedestrian walks on an overpass in Tianjin, China, on December 19.
A pedestrian walks on an overpass in Tianjin, China, on December 19.
VCG/Getty Images
A cyclist crosses a smog-shrouded street in Lianyungang on December 19.
A cyclist crosses a smog-shrouded street in Lianyungang on December 19.
STR/AFP/Getty Images
A man rides an escalator in Beijing on December 19.
A man rides an escalator in Beijing on December 19.
WANG ZHAO/AFP/Getty Images
Women walk through Beijing's Ritan Park on December 19.
Women walk through Beijing's Ritan Park on December 19.
Andy Wong/AP
Tourists visit Tiananmen Square in Beijing on Sunday, December 18.
Tourists visit Tiananmen Square in Beijing on Sunday, December 18.
VCG/Getty Images
Smoke rises from a Tianjin factory on December 18.
Smoke rises from a Tianjin factory on December 18.
Li xiaofei/Imaginechina/AP
A tourist takes a selfie in Beijing on Saturday, December 17.
A tourist takes a selfie in Beijing on Saturday, December 17.
Mi duke/Imaginechina/AP