1A traffic police officer signals to drivers during a smoggy day in Harbin, China, Oct. 21, 2013.
2A woman wearing a mask checks her mobile phone during a smoggy day on the square in front of Harbin's landmark San Sophia church, China, Oct. 21, 2013.
3People ride along a street on a smoggy day in Daqing, Heilongjiang province, China, Oct. 21, 2013.
4People walk on a bridge during a smoggy day in Jilin, Jilin province, Oct. 21, 2013.