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)

A student protester throws a stone against a riot police vehicle during a demonstration to demand changes in the education system in Santiago, Chile, April 21, 2016. (Photo by Ivan Alvarado/Reuters)

Kim Goodman, from Chicago, Illinois, US, holds the record for the farthest eyeball protrusion, at 12mm. (Photo by Paul Michael Hughes/Guinness World Records/PA Wire Press Association)

A woman dressed in a Tang-dynasty costume performs at a show by designer Chu Yan at China Fashion Week in Beijing, China, October 30, 2018. (Photo by Jason Lee/Reuters)

Getting her tongue pierced was “exciting and scary” says a teen who succumbed to pressure from her best friend in Austin, Texas, February 22, 2008. This image is featured in National Geographic's exhibition “Women of Vision: National Geographic Photographers on Assignment”, on view at the Palm Beach Photographic Centre, Jan. 22 - Mar. 22, 2015. (Photo by Kitra Cahana/National Geographic)

Savita, a street performer, helps her dog to balance on empty tin containers as they perform at a roadside in Ahmedabad September 7, 2014. (Photo by Amit Dave/Reuters)

Chloe Lewis attends “The Ony Way Is Essex” season finale filming in Wintney, Hook, England on October 29, 2017. (Photo by Beretta/Sims/Rex Features/Shutterstock)

A father crosses a road with his twin daughters in Shanghai, China September 28, 2018. (Photo by Aly Song/Reuters)