A woman wearing a scarf to cover her face looks on as she waits for a passenger bus on a smoggy morning in New Delhi, India, November 8, 2017. The Great Smog of Delhi is an ongoing severe air-pollution event in New Delhi and adjoining areas in the National Capital Territory of India, in November 2017. Air pollution at this time peaked on both PM 2.5 and PM 10 levels. It has been reported as one of the worst levels of air quality in Delhi since 1999. (Photo by Saumya Khandelwal/Reuters)

Italy's Mount Etna, Europe's tallest and most active volcano, spews lava as it erupts on the southern island of Sicily, Italy, February 28, 2017. (Photo by Antonio Parrinello/Reuters)

Eddie Ladd and Gwyn Emberton perform as Dylan and Caitlin Thomas in “Caitlin” at the Lauriston Hall, Edinburgh, Scotland on August 25 2017. (Photo by Mary Turner/Reuters)

A Geoffroy's Monk Saki is seen at the Parque de Las Leyendas zoo in Lima, Peru, February 14, 2018. (Photo by Guadalupe Pardo/Reuters)

In this February 20, 2018 photo, fair vendor Noelia Flores holds up a black backdrop behind a small statue of an “Ekeko”, the god of prosperity, for a portrait at her booth during the annual Alasita Fair in La Paz, Bolivia. Every year, thousands of Bolivians head to the feast of Alasitas that is held in his honor to buy miniature cars, houses and toy dollar bills symbolizing their dreams of prosperity. (Photo by Juan Karita/AP Photo)

In this Sunday, May 29, 2016 photo, fighters take a selfie while firing artillery during fight against Islamic State militants in Fallujah, Iraq. Iraqi forces this week pushed into the city's southern sections after securing surrounding towns and villages more than 50,000 people are believed to be trapped inside the Sunni majority city, about 65 kilometers (40 miles) west of Baghdad. (Photo by Anmar Khalil/AP Photo)

Resident Taina holds her brother Ysaque in the hallway outside their apartment in an occupied building in the Mangueira “favela” community on August 13, 2016 in Rio de Janeiro, Brazil. (Photo by Mario Tama/Getty Images)

Boys play with a drainage culvert used for flood control in Las Pinas, Metro Manila February 28, 2016. (Photo by Erik De Castro/Reuters)