In this November 30, 2017 photo, Douglas scoops up mud from the bottom of the polluted Guaire River, in search of gold and anything valuable he can sell, in Caracas, Venezuela. Some stretches of the river smell of sewer while others emit a toxic odor of fuel, a stench that stays in ones nose for hours after leaving the water. (Photo by Ariana Cubillos/AP Photo)

Iraqi firefighters try to stop the fire of burning oil wells in Kirkuk, northern Iraq, 02 June 2016. Two Khabbaz oil field wells in Kirkuk Province, northern Iraq, exploded by suspected insurgents, a security official said. (Photo by EPA/Stringer)

A worker sprays disinfectant at Independence Square during a disinfection operation, amid the coronavirus disease (COVID-19) outbreak in Kuala Lumpur on October 17, 2020. (Photo by Lim Huey Teng/Reuters)

Ukraine's Olga Polyuk falls while competing in the freestyle skiing women's aerials qualification during the Beijing 2022 Winter Olympic Games at the Genting Snow Park A & M Stadium in Zhangjiakou on February 14, 2022. (Photo by Marco Bertorello/AFP Photo)

Police detain a demonstrator during an action against Russia's attack on Ukraine in St. Petersburg, Russia, Wednesday, March 2, 2022. Protests against the Russian invasion of Ukraine resumed on Wednesday, with people taking to the streets of Moscow and St. Petersburg and other Russian towns despite mass arrests. (Photo by Dmitri Lovetsky/AP Photo)

A Sikh devotee carries on over-sized religious sword during a religious procession to celebrate the birth anniversary of the first Sikh Guru or master, Sri Guru Nanak Dev Ji, the founder of Sikhism in Amritsar, India, 05 November 2014. The birth anniversary of Guru Nanak Dev Ji will be observed on 06 November. (Photo by Raminder Pal Singh/EPA)

The 26th annual National Geographic Traveler Photo Contest is now accepting submissions. Official categories include: “Travel Portraits”, “Outdoor Scenes”, “Sense of Place” and “Spontaneous Moments”. The contest is accepting entries until June 30. Photo: “Forest lights”. Aurora Borealis over the forest of the Pyhae Luosto National Park, Finland. (Photo and caption by Nicholas Roemmelt/National Geographic Traveler Photo Contest)

A general view of Hong Kong's business district is seen Thursday, August 1, 2013. (Photo by Vincent Yu/AP Photo)