When Mongolia established its modern incarnation in 1992 after the fall of the Soviet Union, over half of its population lived as nomads who derived their primary income from herding. These nomads lived in tents with canvas walls and buckled down for the occasional harsh winter. It was one of the least densely populated countries in the world, with just 1.2 million people living in urban areas, and Ulaanbaatar, the nation’s capital, had a population of just 606,000.

That’s all changed, except for the yurts. Desertification as a result of climate change has driven Mongolia’s herders to abandon their nomadic lifestyle and set up their gers — the squat, one-room tents originally made to be dismantled and moved to enable a nomadic lifestyle — permanently on the outskirts of Mongolia’s cities. The resulting districts have had disastrous consequences for the country’s air quality, mainly due to the fact that gers are heated by individual coal-burning stoves.

Ulaanbaatar has been hit hardest: 600,000 domestic migrants have taken up residence since 1992, and almost 60 percent of the city’s residents now live in the ger district, with 200,000 gers burning an estimated 600,000 tons of coal every winter. The resulting smog accounts for 80 percent of the capital’s air pollution emissions.

That’s according to a 2017 report by the Mongolian National Agency for Meteorology and Environment Monitoring. Today, the IQ Air live rankings found it to be the world’s fifth most polluted city. Mongolia emits just a tiny percentage of the world’s carbon — .07 percent compared to the United States’ 13.77 percent — but for its residents, Ulaanbaatar’s pollution is an enormous problem.

Not only is Ulaanbaatar home to the country’s largest ger district, but it is also now home to 47 percent of Mongolia’s total population. With almost half of the population subjected to the smog that blankets Ulaanbaatar every winter, the cost to the country’s health system is considerable — and growing. Figures released by UNICEF say air pollution–related diseases in children cost the city’s public health services $4.8 million in 2016. When the cost to adults is factored in, the figure rises to $8.5 million, accounting for 4.6 percent of Ulaanbaatar’s entire annual health care budget. Over the past decade, respiratory infections have risen by 270 percent. Children in Ulaanbaatar have 40 percent lower lung function than those in the countryside. By comparison, growing up in a house with a smoker can reduce a child’s lung function by 20 percent.

Steps are being taken to find solutions, but results are varied. UNICEF helps ensure “that the health sector is well prepared for winter season to manage the overwhelming number of sick children and pregnant women” by providing training to health care professionals and ensuring medicine is readily available, says UNICEF Mongolia representative Alex Heikens. The government has outlawed the burning of raw coal and plans are in place to sell 600,000 cleaner burning charcoal briquettes to the residents of Mongolia’s ger districts every winter. Critics argue the former is almost impossible to police and the latter difficult to sell.

Last year, UNICEF’s Office of Innovation invited a number of companies and experts to help modernize Mongolia’s gers. As part of the project, outdoor clothing company Arc’teryx used its expertise in insulation and design to limit the amount of coal needed for warmth by making them better insulated. “The current ger community get the issues they face in using a ger as a permanent place of residence, as opposed to one eminently suited to a nomadic way of life,” says Patrick Fitzsimmons, design developer for tooling and machines at Arc’teryx. “The prevalence of outdoor insulation … indicates a basic understanding of the nature of the problem, but the solutions in play are, at best, stopgap.”

Efforts by UNICEF, private companies like Arc’teryx and Mongolian authorities are in the early stages and have so far been slow to show signs of progress. According to the National Statistics Office of Mongolia, average monthly readings for PM10 (airborne particle matter with less than 10 microns), PM2.5 and sulphur dioxide levels in Mongolia’s capital increased from 2018 to 2019. “Pollution levels seem to have leveled off, and may even be improving slightly,” says Ryan Allen, professor in environmental health at Simon Fraser University. “But concentrations remain several times higher than international guidelines, particularly in winter, so without unprecedented improvements in air quality, this is going to remain a public health crisis for the foreseeable future.”

As the ger districts swell and expand as even more herders abandon the nomadic way of life in favor of permanence, the people of Mongolia’s cities, particularly the young, will continue to face the consequences. The issue may be a seasonal one, but the effects on the country’s collective health will likely be felt year-round for generations to come.