A woman wearing a mask walk in a street in a Yonghegong Lama temple compound seen shrouded in smog in Beijing, China, 30 November 2015. Beijing issued an orange alert for heavy smog 30 November, the highest level this year. Authorities in the Chinese capital warned of 'severe pollution' and advised the capital's 20 million inhabitants to stay indoors. (Photo by How Hwee Young/EPA)

A man drinks at a "colored" water cooler in a streetcar terminal in Oklahoma City, July 1939. (Photo by Reuters/Library of Congress)

Pro-Russian activists attack policemen guarding the burned trade union building in the southern Ukrainian city of Odessa on May 3, 2014. More than 30 people were killed in a “criminal” blaze in Ukraine's southern city of Odessa, as violence spread across the country during the bloodiest day since Kiev's Western-backed government took power. Ukraine's interior ministry said at least 31 people had died in the fire Friday, with local media reporting that pro-Russian militants were believed to have been in the burning building at the time. (Photo by Anatolii Stepanov/AFP Photo)

A police officer detains a woman on suspicion of collaborating with the 18th street gang during a "Safe House" operation at the Concepcion neighbourhood in San Salvador, July 2, 2015. Salvadoran police make “Safe House” operations at dangerous neighbourhoods of the capital to prevent murders, according to local media. (Photo by Jose Cabezas/Reuters)

A girl bathes to cool off herself with water that is leaking from a broken pipe valve on a hot summer day on the outskirts of Ahmedabad, India, May 18, 2015. (Photo by Amit Dave/Reuters)

A Lebanese man is reflected in a pool of dirty water as he casts his fishing pole from a rocky coastal area along the Beirut coastline, Lebanon, Monday, October 3, 2016. (Photo by Hassan Ammar/AP Photo)

A street vendor sells sliced fruits during a pro-government rally in Caracas, Venezuela, June 21, 2016. (Photo by Mariana Bazo/Reuters)

Friends outside the convention center during opening day of the annual Comic-Con International in San Diego, California, United States July 21, 2016. (Photo by WENN/SIPA Press)