Peruvian surfer Carlos “Huevito” Areola rides a reed board, or “caballito” (little horse), into a wave at Sydney's Bondi Beach, February 24, 2016. Areola is part of a group of Peruvian surfers touring Australia’s east coast to promote the use of the “caballito”. The “caballito” is thought to have been invented around 3,000 BC in northern Peru. (Photo by Jason Reed/Reuters)

Handguns turned in from the public as part of the “Gun Turn-in” event where a $100 gift card is given for every firearm and a $10 gift card for each BB-gun, air-gun, or replica firearm turned over to police at Universal Missionary Baptist Church in Chicago, Illinois, U.S. May 28, 2016. (Photo by Jim Young/Reuters)

Swiss police officers stand beside of mock gates of the NEAT Gotthard Base Tunnel inside the event hall for the upcoming opening ceremony near the town of Erstfeld, Switzerland May 31, 2016. The celebrations of the opening of the Gotthard Base Tunnel will start on June 1, 2016. With a length of 57 km (35 miles) crossing the Alps, the Gotthard Base tunnel is the world's longest train tunnel. (Photo by Arnd Wiegmann/Reuters)

Britain Horse Racing, Royal Ascot, Ascot Racecourse on June 16, 2016. Ladies Day Racegoers wear hats. (Photo by Toby Melville/Reuters)

A model presents a creation by Chinese designer Chen Wen at China Fashion Week in Beijing, China March 29, 2017. (Photo by Jason Lee/Reuters)

A blue-throated macaw receives acupuncture and laser therapy treatment at the veterinary hospital in Brasilia Zoo, July 30, 2015. The zoo's veterinary hospital uses acupuncture and laser therapy to improve the health and well-being of animals with chronic diseases. (Photo by Ueslei Marcelino/Reuters)

A Hindu devotee wearing a t-shirt printed with a portrait of Lord Shiva takes a holy dip while participating in the “Bol Bom” pilgrimage in Kathmandu August 10, 2015. The faithful, chanting the name of Lord Shiva, run about 15 km (9 miles) barefooted toward Pashupatinath temple seeking good health, wealth and happiness. (Photo by Navesh Chitrakar/Reuters)

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)