Photo taken on Jan. 22, 2013 shows a building in fog in Bazhou city, North China's Hebei Province, January 22, 2013. (Xinhua/Wang Geming)
A traffic policeman is on guard in fog in Bazhou city, North China's Hebei Province, January 22, 2013. (Xinhua/Wang Geming)
Vehicles run on a fog-shrouded road in Tianjin, North China, January 22, 2013. (Xinhua/Zhou Qinlong)
Combo photo taken on January 22, 2013 (up) and January 18, 2013 (bottom) show views of buildings in the same place in Nanjing, capital of East China's Jiangsu Province. (Xinhua)
A boat runs on a fog-shrouded river in Suzhou city, East China's Jiangsu Province, January 22, 2013. (Xinhua/Wang Jiankang)
A pedestrian walks in fog in Bazhou city, North China's Hebei Province, January 22, 2013. (Xinhua/Wang Geming)
A man rides on a fog-shrouded bridge in Suzhou city, East China's Jiangsu Province, January 22, 2013. (Xinhua/Wang Jiankang)