Thousands of heavy-duty trucks loaded with coal are lined up for up to 130 kilometres from the Mongolia-China border on a sole road in the Gobi desert, Mongolia, October 29, 2017. The journey can take more than a week. (Photo by Bazarsukh Rentsendorj/Reuters)

Bicycles of various bike-sharing services are seen at an urban village in smog during a polluted day in Shanghai, 2017. Rapid expansion of shared bicycle companies across China has led to massive piles of abandoned bikes as supply outstrips demand. (Photo by Aly Song/Reuters)

A model presents a creation from fashion label Maison Lejaby during the Festival of Young Fashion Designers, an event held in tribute to Azzedine Alaia, a Franco-Tunisian fashion designer who died in November 2017; in Tunis, Tunisia, 04 May 2018. (Photo by Mohamed Messara/EPA/EFE)

Vehicles pass through the heavy fog and air pollution that cover Skopje valley in the early morning, in Skopje, The Former Yugoslav Republic of Macedonia, 14 December 2017. According to media reports, Skopje is considered one of the most polluted cities in the world. (Photo by Georgi Licovski/EPA/EFE)

A reveller holds her dog dressed in costume, during the Rio Dog Carnival, known as the Blocao – with “bloco” meaning street party and “cao” dog, during pre- carnival celebrations at Copacabana beach in Rio de Janeiro, Brazil, on February 19, 2017. (Photo by Yasuyoshi Chiba/AFP Photo)

Paramasivan points to the statue of sun god Surya at a temple outside the Kodaikanal Solar Observatory, India, February 5, 2017. In the early morning darkness, Devendran P. walks up a hill to a solar observatory in India's southern hill town of Kodaikanal, trudging the same path his father and grandfather walked in a century-old family tradition of studying the sun. (Photo by Danish Siddiqui/Reuters)

Carnival revellers dressed as “Peliqueiros” run along a street in the village of Laza, Spain February 26, 2017. “Peliqueiros”, or ancient tax collectors, pursued villagers through the streets ringing their cowbells and hitting villagers with their sticks. (Photo by Miguel Vidal/Reuters)

A doorman stands at the entrance of the “The Walled Off Hotel” in the West Bank city of Bethlehem, Friday, March 3, 2017. The owner of a guest house packed with the elusive artist Banksy's work has opened the doors of his West Bank establishments to media, showcasing its unique “worst view in the world”. The hotel, several of whose rooms look onto an Israeli security watchtower, is awash in the trademark satirical work of the mysterious artist. (Photo by Dusan Vranic/AP Photo)