A young visitor interacts with a baby hippopotamus swimming in its enclosure at the Berlin Zoo on January 1, 2018. Tourists and locals flocked to the zoo in the German capital on the unseasonably warm first day of the year. (Photo by Odd Andersen/AFP Photo)

Residents carry a slaughtered pig with a bamboo pole as they walk home on a street, which was shut to traffic due to ice, in Leishan county, Guizhou province January 31, 2015. Blizzards and icy rain that lasted for several days at the end of January have disrupted traffic, collapsed houses and decimated crops in central Chinese provinces, Xinhua News Agency reported. (Photo by Reuters/Stringer)

Three secondary schoolboys smoking an illicit cigarette in Hyde Park, London. (Photo by Evening Standard/Getty Images). May 1972

Winner of the Sandow bodybuilding competition, Mr. Murray. (Photo by Reinhold Thiele/Thiele/Getty Images). Circa 1905

Graffiti is painted on the bathroom walls at a restaurant in the Williamsburg area of Brooklyn borough in New York, United States, October 1, 2015. Some 2.4 billion people around the world don't have access to decent sanitation and more than a billion are forced to defecate in the open, risking disease and other dangers, according to the United Nations. To mark World Toilet Day on November 19, Reuters photographers captured pictures of toilets in cities, towns and villages around the globe. (Photo by Shannon Stapleton/Reuters)

A niqab-wearing Salafist protester takes a selfie as she attends a demonstration against the ban on the sale and manufacturing of the full-burqa in Rabat January 15, 2017. (Photo by Reuters/Stringer)

In this November 28, 1966 file photo, one of the 10 beagles involved in the first test of the Veterans Administration Hospital in East Orange, N.J. smokes a cigarette through a machine linked to its windpipe by a plastic tube to test any link between smoking and emphysema. (Photo by AP Photo)