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)

In this photo taken on Tuesday, December 20, 2016, dancers of the U.S. company “Catapult” create a group of ostriches, during their show “Magic Shadows”, in Milan, Italy. Dancers in the company create shadow sculptures with their bodies, giving a contemporary twist to the ancient Chinese art of shadow theaters. (Photo by Luca Bruno/AP Photo)

A model presents a creation from the Fall/Winter 2017/18 collection by designer Lena Hoschek during the Mercedes-Benz Fashion Week Berlin, in Berlin, Germany, 17 January 2017. The Mercedes-Benz Fashion Week Berlin runs from 17 to 20 January. (Photo by Clemens Bilan/EPA)

An Afghan girl carries water on her back as she climbs a hill in Kabul, Afghanistan February 20, 2017. A growing population is straining water supplies in Afghanistan's capital, forcing those who can afford it to dig unregulated wells ever deeper to tap a falling water table. Finding water in arid Afghanistan is virtually always a challenge, but a drop in the groundwater level in Kabul caused by overuse and drought is making it even more difficult for residents, especially the poor. (Photo by Omar Sobhani/Reuters)

High-rise buildings are partly covered by heavy fog at Hong Kong's Victoria Harbour Monday, March 20, 2017. Fog blanketing Hong Kong is common in springtime and may greatly affect shipping and aviation. (Photo by Vincent Yu/AP Photo)

An Afghan Army soldier secures the hill overlooking the Kart-e Sakhi mosque in Kabul, Afghanistan, Wednesday, March 20, 2013. Thousands of Afghans will celebrate Nowruz on Thursday, March 21, 2013 to mark the first day of spring and the beginning of the year on the Iranian calendar. (Photo by Ahmad Jamshid/AP Photo)

A man watches the approaching flames as the Springs fire continues to grow near Camarillo, California, on May 3, 2013. The wildfire has spread to more than 18,000 acres on day two and is 20 percent contained. (Photo by David McNew)

A member of the “Ladies in White” dissident group shouts as she is carried away by police officers after they broke up a regular march of the group, detaining about 50 people, hours before U.S. President Barack Obama arrives for a historic visit, in Havana, Cuba March 20, 2016. (Photo by Ueslei Marcelino/Reuters)