People in Kathmandu joke that the face mask has now become part of the national dress – an indispensable accessory in an effort to protect themselves from the dust. Nepal has the worst air quality in the world, according to the Environmental Performance Index. (Photo by Pete Pattisson/The Guardian)

An anti-extradition bill protester throws a stone at a police station in Tseung Kwan O residential district, in Hong Kong, China, August 4, 2019. (Photo by Kim Kyung-Hoon/Reuters)

Laura and Chris Marriott pose during a press photo call with their winning carrot at 3.8kg and Beetroot at 17.840kg following judging for the giant vegetable competition at the Harrogate Autumn Flower Show on September 13, 2019 in Harrogate, England. (Photo by Ian Forsyth/Getty Images)

A frosty sunset is seen through icicles in Peremilovo village, 65 km (40,6 miles) north of Moscow, Russia, Sunday, December 16, 2018. Temperatures in the Moscow region on Sunday dropped to –12 degree Celsius (10 Fahrenheit). (Photo by Alexander Zemlianichenko/AP Photo)

Demonstrators help a fellow protester during clashes with security forces during an opposition rally in Caracas, Venezuela on April 4, 2017. Protesters clashed with police in Venezuela Tuesday as the opposition mobilized against moves to tighten President Nicolas Maduro' s grip on power. Protesters hurled stones at riot police who fired tear gas as they blocked the demonstrators from advancing through central Caracas, where pro- government activists were also planning to march. (Photo by Carlos Garcia Rawlins/Reuters)

An Indian Runner duck searches for food on a snow-covered meadow in Aitrang, southern Germany, Wednesday. April 19, 2017. (Photo by Karl-Josef Hildenbrand/DPA via AP Photo)

Princess Charlene poses after the arrival of the Riviera Water Bike Challenge in support of the Princess Charlene of Monaco Foundation, in Nice, France, June 4, 2017. (Photo by Eric Gaillard/Reuters)

Zamora, 55, self-employed, poses for a photograph in front of the Cuban and U.S. flags after buying a pineapple in Havana, March 25, 2016. Regarding Obama's historic visit to the island, Zamora said “It's good for the Cubans that he came and re-established relationships between the two countries”. (Photo by Ueslei Marcelino/Reuters)