Heavy fog shrouds Beijing Vehicles run on a fog-affected road in Beijing, capital of China, on the morning of Feb. 22, 2012. A fog appeare...

Heavy fog shrouds Beijing

Vehicles run on a fog-affected road in Beijing, capital of China, on the morning of Feb. 22, 2012. A fog appeared here on Wednesday with the arrival of a cold wave. (Xinhua/Li Fangyu)

Vehicles wait at the traffic light on a fog-affected road in Beijing, capital of China, Feb. 22, 2012. A fog appeared here on Wednesday with the arrival of a cold wave. (Xinhua/Li Fangyu)

Vehicles run on a fog-affected road in Beijing, capital of China, on the morning of Feb. 22, 2012.

A fog appeared here on Wednesday with the arrival of a cold wave.