Pedestrians cover their face as they walk along the dusty road in Kathmandu, Nepal February 27, 2017. Nepal has forced 2,500 old vehicles off roads in its capital city of Kathmandu, part of a fight against alarming air pollution levels that have hit nine times World Health Organisation (WHO) limits. Air pollution has been a chronic problem in rapidly growing Kathmandu, which sits in a Himalayan valley and is home to more than 3mn people. (Photo by Navesh Chitrakar/Reuters)

Two women lighting cigarettes on a tennis court in Essex, England circa 1930's. (Photo by Keystone View/FPG/Getty Images)

A man dressed as Hindu Lord Shiva performs during a religious procession ahead of the Hindu festival of Maha Shivaratri, in Jammu February 23, 2017. (Photo by Mukesh Gupta/Reuters)

Traditional sculptures by Chin tribe in, Mindat, Myanmar, November 2016. In the mountains of Myanmar lives a tribe where the women have taken a unique approach to their beauty regime by decorating their faces with tattoos. The Chin people in the remote mountain town of Mindat, have been marking women in the area with intricate face tattoos for centuries. (Photo by Teh Han Lin/Barcroft Images)

A woman takes part in a global March for marijuana in Medellin, Colombia, May 7, 2016. The Global Marijuana March (GMM) is an annual rally held at different locations across the planet. It refers to cannabis-related events that occur on the first Saturday in May, or thereabouts, and may include marches, meetings, rallies, raves, concerts, festivals and information tables. (Photo by Fredy Builes/Reuters)

N.C. Dezendorf, wife of the general manager of the Electro-Motive division of General Motors, christens the new lightweight “Aerotrain” at the company's locomotive works in La Grange, Ill. on August 22, 1955. (Photo by Edward Kitch/AP Photo)

A voodoo believer, dressed as "Gede", a spirit of voodoo, sits on the cross of Baron Samdi during celebrations at the cemetery of Port-au-Prince, Haiti, November 1, 2016. Voodoo believers and devotees offer candles, alcohol and food. The Day of the Dead is celebrated on the first two days of November during All Saints and All Souls Day. (Photo by Andres Martinez Casares/Reuters)

A Bedouin rifleman hides behind his camel while he carefully takes aim in the Sahara desert. (Photo by Three Lions/Getty Images). Circa 1955