It is now the second most common cause of mortality among Mongolian children, accounting for 15 percent of all deaths.A 2011 study by Ryan Allen, associate professor of environmental health at Simon Fraser University, found that one in 10 deaths in Ulaanbaatar can be attributed to air pollution.Here, tree stumps dot the landscape, felled by city residents for essential fuel.
Setevdorj Myagmartsogt lives with his wife, four children and two relatives in his ger near a coal depot not far from the centre of the Mongolian capital.
This winter, the rate of pollution-related pneumonia among children has been so high that the city's hospitals are full.
The dzuds ruin the farmers' livelihoods, and due to lack of social support systems, the only choice left is to move to Ulaanbaatar and find a job.
As more people arrive in the city in their gers, the number of stoves increases too, each belting out enough heat to cook three meals a day and heat the cold gers through winter.
Weather patterns, called dzud, have forced many to leave their traditional way of life herding cattle and sheep and move to the capital.
Dzud is an ultra cold-weather phenomenon believed to occur in five-yearly cycles, but has been increasing in frequency, especially in the Gobi Desert region of Mongolia.When you enter the ger districts it gets so much worse."A ger house is perfect for a nomad.A large, tent-like structure, it is built using poles and felt, and can be collapsed in two hours.Wearing face masks to protect them from the smog, the crowds marched in minus 20 degree temperatures waving banners reading, "Wake up and smell the smog." In this ex-Soviet city, protests are rare.Mongolians understand the seriousness of the situation.Ulaanbaatar is one of the world's most heavily polluted cities—in December it experienced pollution levels five times higher than in Beijing.For families, trying to survive in the world's coldest capital is expensive: many throw everything onto the family stove—old shoes, tyres, and scrap plastic.The levels of fine particulate matter (PM2.5), part of what causes pollution to be damaging to human health, have been recorded as 80 times higher than WHO guidelines, and the organization predicts the situation will worsen over the next 10 years.On December 16 the level of PM2.5 peaked at 1,985 micrograms per cubic metre (µg/m 3 ).The WHO recommends PM2.5 exposure of no more than 25µg/m 3 on average over a 24-hour period.Setevdorj Myagmartsogt smokes a cigarette outside his tent-like ger home, which is heated by coal burning stove, in Ulaanbaatar, Mongolia, January 29.