A citizen rides in smog on December 20, 2016 in Jinan, Shandong Province of China. Air quality index (AQI) readings exceeded 400 and some schools have suspended classes in Jinan. (Photo by VCG/VCG via Getty Images)

Models painted in camouflage colours to blend in with the background pose for Chinese artist Liu Bolin's artwork “Dongji”, or Winter Solstice, on the second day after China's capital Beijing issued its second ever “red alert” for air pollution, in Beijing, China, December 20, 2015. In this artwork, Liu wants to express his concerns about China and its people, including air pollution problem, Liu told Reuters. (Photo by Kim Kyung-Hoon/Reuters)

A woman wearing a scarf to cover her face looks on as she waits for a passenger bus on a smoggy morning in New Delhi, India, November 8, 2017. The Great Smog of Delhi is an ongoing severe air-pollution event in New Delhi and adjoining areas in the National Capital Territory of India, in November 2017. Air pollution at this time peaked on both PM 2.5 and PM 10 levels. It has been reported as one of the worst levels of air quality in Delhi since 1999. (Photo by Saumya Khandelwal/Reuters)

Participants wearing masks during a hazy day at the Beijing International Marathon in front of Tiananmen Square, in Beijing, October 19, 2014. (Photo by Reuters/Stringer)

This picture taken on April 12, 2017 shows men carrying bamboo through a forest near Dashan village near the city of Lin'an, Zhejiang Province. Lin'an is in a area of eastern Zhejiang province whose rich bamboo forests are estimated to supply up to two-thirds of China's bamboo shoots, plus a range of other products derived from the fast-growing plant that are produced both for domestic and overseas markets. (Photo by Johannes Eisele/AFP Photo)

Residents carry an injured woman rescued from a collapsed house in Funing county in Yancheng city of eastern China's Jiangsu Province on Thursday June 23, 2016. A powerful tornado hit Thursday, with reports of dozens killed and large numbers of buildings destroyed in the eastern Chinese province of Jiangsu, according to state media. (Photo by Chinatopix via AP Photo)

A Chinese rescuer evacuates a young boy from flooded areas caused by heavy rains in Changsha city, central China's Hunan provincehangsha, capital of Hunan on July 3, 2017. (Photo by Imaginechina/Rex Features/Shutterstock)

This picture taken on July 9, 2013 shows heavy flood waters sweeping through Beichuan in southwest China´s Sichuan province. Rainstorms sweeping across parts of China have affected millions, causing landslides and disabling transportation in provinces such as Sichuan and Yunnan, state media reported. (Photo by AFP Photo)