Students stand on the roof of a wooden boat as haze blankets the Musi River while they travel to school in Palembang, on Indonesia's Sumatra island, September 10, 2015. Indonesia is investigating 10 firms over worsening forest fires that have created a blanket of smog over Southeast Asia, threatening them with sanctions if they are found responsible, a government minister said on Tuesday. The thick haze from Indonesia's Sumatra and Kalimantan islands has forced the repeated cancellation of flights in the area and pushed air quality to unhealthy levels in neighbouring Singapore and Malaysia. (Photo by Reuters/Beawiharta)

An Egyptian passenger sits on the locomotive of a train as it leaves Cairo train station in Egypt, Wednesday, October 14, 2015. (Photo by Amr Nabil/AP Photo)

A conductor (C) collects fares from candy floss sellers as they travel in a tram to a marketplace early morning in Kolkata, India, December 23, 2015. (Photo by Rupak De Chowdhuri/Reuters)

A plane battling the Ferguson Fire passes the setting sun in unincorporated Mariposa County Calif., near Yosemite National Park on Sunday, July 15, 2018. (Photo by Noah Berger/AP Photo)

A photojournalist is silhouetted by the sunset as a lightning strike at a resort affected by Saturday's tsunami in Carita, Indonesia, Tuesday, December 25, 2018. Christmas celebrations traditionally filled with laughter and uplifting music were replaced by somber prayers for tsunami victims in an area hit without warning following a volcanic eruption, leaving hundreds of people dead and thousands homeless in disaster-prone Indonesia. (Photo by Fauzy Chaniago/AP Photo)

A man stands by an installation depicting “2019” in the Red Square in Moscow, Russia on December 17, 2018. (Photo by Maxim Shemetov/Reuters)

English singer-songwriter, dancer, model and actress Sarah Harding attends the launch of Walkers Bring It Back Campaign at Vinopolis on September 3, 2015 in London, England. (Photo by Joseph Okpako/WireImage)

American model and actress Emily O'Hara Ratajkowski attends the Jacquemus Spring Summer 2020 show on June 24, 2019 in Valensole, France. (Photo by Arnold Jerocki/Getty Images)