A policeman wearing a mask works on the Tiananmen Square in Beijing, Oct 5, 2013. China will build a nation-wide network within three to five years to monitor the impact of air pollution on health, a latest step to deal with a persistent smog crisis in big cities, an official said. [Photo/CFP]

Giant waves whipped by Typhoon Fitow surge up against a residential area near the shoreline of Dongtou Island in Wenzhou city, East China's Zhejiang province, on Oct 6, 2013. [Photo/Xinhua]