A woman wears a face mask in the part of the city near neighbourhoods known for burning coal for heating in Ulaanbaatar, Mongolia January 26, 2017. Not many people in Ulaanbaatar wear masks to protect themselves against pollution. (Photo by B. Rentsendorj/Reuters)

Iraqi Kurdish refugees wait with children in Cukurca refugee camp in Turkey April 8, 1991. Reuters photographers have chronicled Kurdish refugee crises over the years. In 1991 Srdjan Zivulovic documented refugees in Cukurca who had escaped a military operation by Saddam Hussein's government in Iraq aimed at “Arabising” Kurdish areas in the north. Hundreds of thousands fled into Turkey and Iran. Images shot in recent months show familiar scenes as crowds of people flee Islamic State militants in Syria. There are as many as 30 million Kurds, spread through Turkey, Iraq, Syria and Iran. Most Kurds are Sunni Muslims, but tend to feel more loyalty to their Kurdishness, rather than their religion. (Photo by Srdjan Zivulovic/Reuters)

Indigenous Sahrawi girls play on an improvised see-saw at a refugee camp of Boudjdour in Tindouf, southern Algeria March 3, 2016. UN Secretary General Ban Ki-moon is scheduled to visit the Sahrawi refugees in south-west Algeria's Tindouf region. (Photo by Zohra Bensemra/Reuters)

Naked activists take part in a protest against fur trade, called by international non profit animal rights organisation AnimaNaturalis, in Barcelona, on December 1, 2019, on the eve of the opening of the UN Climate Change Conference COP25. (Photo by Pau Barrena/AFP Photo)

Walkers cross the river Waalbrug during the first day of the 98th annual four-days walking event, the “Vierdaagse” in Nijmegen, Netherlands, July 15, 2014. The “Nijmeegse Vierdaagse” is an annual public four-day field march which is held since 1909 in the third week of July. (Photo by Erik van 't Wout/EPA)

A women sell food under the wing of a plane wreckage being used as housing in M'Poko Internally Displaced Persons camp in Bangui, Central African Republic on Saturday, February 13, 2016. The M'Poko IDP camp, just outside the capitol's airport, currently houses close to 20,000 people displaced due to the ongoing conflict in Central African Republic. (Photo by Jane Hahn/The Washington Post)

In this August 31, 2017, photo, mock fish are displayed to offer to the ancestors during the “Hungry Ghost Festival” in Hong Kong. Countless hungry and restless ghosts are roaming Hong Kong, and the world, to visit their living ancestors, at least according to Chinese convention. In traditional Chinese belief, the seventh month of the lunar year is reserved for the Hungry Ghost festival, or Yu Lan, a raucous celebration marked by feasts and music. (Photo by Kin Cheung/AP Photo)

A policewoman tries to stop an anti-Occupy protester from breaking a police cordon to charge at pro-democracy protesters during a confrontation in Hong Kong October 13, 2014. Hundreds of unidentified people, some wearing masks, tried to break down protest barriers in the heart of Hong Kong's business district on Monday, scuffling with protesters who have occupied the streets for the past two weeks. (Photo by Bobby Yip/Reuters)