A petitioner with her grievances written on her clothes walks along a street in Beijing Tuesday, December 22, 2015. After months behind bars, Pu Zhiqiang, one of China's most prominent human rights lawyers, left a detention center Tuesday after receiving a suspended prison sentence in a case involving online comments critical of the ruling Communist Party. (Photo by Ng Han Guan/AP Photo)





A policeman talks to the driver of a motor-tricycle on a road amid heavy haze in Handan city in northern China's Hebei province Thursday, December 24, 2015. Meteorological authorities in Hebei, a province which neighbors Beijing and is regarded as China's most polluted, issued its first red alert for smog on Tuesday as more Chinese cities are issuing their first red alerts for pollution in response to forecasts of heavy smog. (Photo by Chinatopix via AP Photo)





Clothes hang from a line in a residential building under construction in the town of Gushi in Henan Province, in this March 28, 2010 file photo. (Photo by David Gray/Reuters)





A man riding a truck yawns in Beijing, China, December 18, 2015. (Photo by Kim Kyung-Hoon/Reuters)





Ethnic Dong children wearing traditional costumes clap as they participate in a singing contest in Rongjiang, Guizhou province, December 18, 2015. (Photo by Reuters/Stringer)





A woman wearing a protective mask stretches at a park as China's capital Beijing braces for four days of choking smog starting Saturday, in Beijing, China, December 19, 2015. (Photo by Kim Kyung-Hoon/Reuters)





A woman wearing a protective mask dances in a park as China's capital Beijing braces for four days of choking smog starting Saturday, in Beijing, China, December 19, 2015. (Photo by Kim Kyung-Hoon/Reuters)





A woman wearing a protective mask stretches her leg at a park as China's capital Beijing braces for four days of choking smog starting Saturday, in Beijing, China, December 19, 2015. (Photo by Kim Kyung-Hoon/Reuters)





Women wearing protective masks visit the Temple of Heaven park as China's capital Beijing braces for four days of choking smog starting Saturday, in Beijing, China, December 19, 2015. (Photo by Kim Kyung-Hoon/Reuters)





Clerks of a souvenir shop wearing traditional costumes play Chinese hacky sack game at the Temple of Heaven park in Beijing, China, December 19, 2015. (Photo by Kim Kyung-Hoon/Reuters)





A man wearing a protective mask stretches on an exercise equipment at a park as China's capital Beijing braces for four days of choking smog starting Saturday, in Beijing, China, December 19, 2015. (Photo by Kim Kyung-Hoon/Reuters)





A man helps a woman stretch her leg at a park in Beijing, China, December 19, 2015. (Photo by Kim Kyung-Hoon/Reuters)





A school girl wearing a protective mask makes her way in a shopping district as China's capital Beijing braces for four days of choking smog starting Saturday, in Beijing, China, December 19, 2015. (Photo by Kim Kyung-Hoon/Reuters)





A man wearing a protective mask stands next to Christmas installations in a shopping district as China's capital Beijing braces for four days of choking smog starting Saturday, in Beijing, China, December 19, 2015. (Photo by Kim Kyung-Hoon/Reuters)





A woman an a child wearing protective masks ride a bicycle on the second day after China's capital Beijing issued its second ever “red alert” for air pollution, in Beijing, China, December 20, 2015. (Photo by Kim Kyung-Hoon/Reuters)





A man wearing a protective mask walks past statues of pandas on the second day after China's capital Beijing issued its second ever “red alert” for air pollution, in Beijing, China, December 20, 2015. (Photo by Kim Kyung-Hoon/Reuters)





Jiang Zhen's son Doudou checks the air quality outside the window of his room with a portable device measuring air quality during an interview with Reuters in his home, on the second day after China's capital Beijing issued its second ever “red alert” for air pollution, in Beijing, China, December 20, 2015. (Photo by Kim Kyung-Hoon/Reuters)





Jiang Zhen's son Doudou shows the air quality around an air purifier with a portable device that measures air quality during an interview with Reuters in his house, on the second day after China's capital Beijing issued its second ever “red alert” for air pollution, in Beijing, China, December 20, 2015. (Photo by Kim Kyung-Hoon/Reuters)





A portable device measuring air quality is placed on a desk while Jiang Zhen's daughter Dudu does her homework in her room, on the second day after China's capital Beijing issued its second ever “red alert” for air pollution, in Beijing, China, December 20, 2015. (Photo by Kim Kyung-Hoon/Reuters)





Jiang Zhen, his wife Zhang Fang and their children Doudou (2nd R) and Dudu (2nd L) pose with a portable device that measures air quality and an air purifier in the children's room, on the second day after China's capital Beijing issued its second ever “red alert” for air pollution, in Beijing, China, December 20, 2015. (Photo by Kim Kyung-Hoon/Reuters)





Jiang Zhen's wife Zhang Fang fetches water from a mineral water tank, on the second day after China's capital Beijing issued its second ever “red alert” for air pollution, in Beijing, China, December 20, 2015. (Photo by Kim Kyung-Hoon/Reuters)





Deliverymen of JD.com dressed as Santa Claus set off to work in Chengdu, Sichuan province, December 22, 2015. (Photo by Reuters/China Daily)





A courier drives amid the heavy smog in the late afternoon, on the last day after China's capital Beijing issued its second ever “red alert” for air pollution in Beijing, China, December 22, 2015. (Photo by Jason Lee/Reuters)





A woman wearing a mask plays mahjong with other residents near a street amid heavy smog in Jinan, Shandong province, China, December 22, 2015. (Photo by Reuters/China Daily)





A motor tricycle runs on the road during a hazy day in Beijing, China, 20 December 2015. Beijing issued a red alert for smog on 18 December 2015, urging schools to close and residents to stay indoors for the second time in 10 days. Restrictions began on 19 December and will last until 22 December, the city's emergency management headquarters announced on the Beijing government website. (Photo by Wu Hong/EPA)





Chinese students who are children of migrants wait in line for lunch in a classroom at an un-official school on December 18, 2015 in Beijing, China. Schools for children of migrants are often unofficial or unrecognized by the state, and were established as a response to the education void created by the decades-long household registration or hukou system. A person's hukou entitles them to social services in their birthplace, meaning millions of Chinese who have migrated from rural areas to cities have been denied rights to urban public services. Reforms to the hukou system come after heavy criticism that it has aggravated a deep social divide in China. The changes could pave the way for up to 70 million children of migrant workers left behind in villages to join their parents in cities. (Photo by Kevin Frayer/Getty Images)





Chinese students who are children of migrants play around as they take a break at an un-official school on December 18, 2015 in Beijing, China. (Photo by Kevin Frayer/Getty Images)





Chinese students who are children of migrants take part in classes at an un-official school on December 18, 2015 in Beijing, China. (Photo by Kevin Frayer/Getty Images)





A man with a mask looks on as a child gets off a donkey cart in Beijing, China, Saturday, December 19, 2015. (Photo by Ng Han Guan/AP Photo)





Young tourists wear masks as they stand near a Chinese Paramilitary policeman in Tiananmen Square in Beijing, China, Saturday, December 19, 2015. Smog built up in the Chinese capital as the second red alert of the month went into effect, forcing many cars off the roads and restricting factory production. (Photo by Ng Han Guan/AP Photo)





Heavily armed Chinese paramilitary police guard a popular mall in the Sanlitun district of Beijing, China, Thursday, December 24, 2015. Increased security could be seen at the area as the U.S. and British embassies in the Chinese capital issued travel advice on possible threats against westerners in the Sanlitun area. (Photo by Ng Han Guan/AP Photo)





A woman clasps her hands together in a prayer at the Forbidden City during a sunny day in Beijing Friday, December 18, 2015. Residents in the Chinese capital are preparing for its second smog red alert as a wave of smog is forecasted to settle over the city from Saturday to Tuesday. (Photo by Ng Han Guan/AP Photo)





A vendor selling national flags and other memorabilia during a sunny day in Beijing Friday, December 18, 2015. (Photo by Ng Han Guan/AP Photo)