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)

Children in Hiroshima, Japan, wearing masks to combat the odour of death after the city was destroyed by the first atom bomb. (Photo by Keystone/Getty Images). 1945

An employee walks past a rotary dredge working at an open-cast iron ore mine of the Stoilensky mining and concentration plant (GOK), owned by the Novolipetsk (NLMK) steel mill, in the city of Stary Oskol in Belgorod region, Russia, August 4, 2015. (Photo by Maxim Shemetov/Reuters)

Myouchin Munehisa, 44, as he finishes Hibashi iron bells made of iron on a production line at Myochin Honpo shop on April 25, 2014 in Himeji, Japan. Myochin family's iron business, started in the Heian period (794-1185) of Japan as an armor and helmet maker, shifted as the needs of people changed in the course of history. (Photo by Buddhika Weerasinghe/Getty Images)

Chinese artist Zhou Jie takes a nap on an unfinished iron wire bed, one of her sculpture works, after lunch at Beijing Now Art Gallery, in Beijing August 11, 2014. Zhou started her art project titled “36 Days” on August 9, in which she would live inside an exhibition hall with an unfinished iron wire bed, some iron wire sculptures in the shape of stuffed animal dolls, a certain amount of food and her mobile phone, for 36 days. The entire process is open to visitors and she may also interact with them, according to Zhou. (Photo by Jason Lee/Reuters)

Mount Whaleback iron ore mine 23°21’32.3”S, 119°40’40.1”E. The Mount Whaleback Iron Ore Mine in the Pilbara region of Western Australia. Roughly 98% of the world’s mined iron ore is used to make steel and is thus a significant component in the construction of buildings, automobiles, and appliances such as refrigerators. (Photo by Daily Overview/DigitalGlobe, a Maxar Company)

Two students in Birmingham, United Kingdom dressed as policewomen enjoy a takeaway on October 31, 2018. Halloween party-goers enjoyed one hell of a night for the annual fright-fest. (Photo by Caters News Agency)