Every winter, as many as 220,000 households burn coal to stay warm. When families cannot afford coal they sometimes burn tyres and other scraps.

The hospitals are packed every winter, as thousands of children fall sick. Visibility is so bad that two people can be walking hand in hand and not be able to see each other. Air pollution, or “smoke” as the residents call it, often reaches several times that of Beijing or Delhi.

“I wanted more for my children but the air is prohibitive,” Darii says. “I’ve never seen air pollution like this before … The food, pollution, everything, is really bad in Ulan Bator.”

Mongolia’s rural residents have flooded the capital in search of a better life. Now, as pollution worsens, officials and residents are looking for ways to lure people back to the countryside.

Today, Ulan Bator, a city designed to accommodate about half a million people, holds three times this number – almost half of the country’s population of 3 million. Harsh winters have killed off millions of livestock, forcing rural herders to the capital for work.

In 2004, almost 70,000 people moved from rural areas to the city, equivalent to the population of an entire province. Since then as many as 45,000 have moved to the capital annually. Most collect in the ger district, an area officials say accounts for 80 per cent of the city’s air pollution.

Under pressure, the government decided last year to ban migration, and recently extended the ban until 2020. But high levels of pollution persist. About 15,000 people marched in Ulan Bator, last year protesting against the smog, in one of the country’s biggest demonstrations in years. In January, concentrations of PM2.5, breathable airborne particles, reached 3,320 micrograms per cubic meter, more than 133 times the level the World Health Organisation deems safe.

“If we do not act, shall we all die burning whatever we want?” asks Batbayasgalan Jantsan, the city’s deputy mayor in charge of green development.

“What are the primary rights of human being? The right to life. The right to a healthy and safe environment. The state is obliged to provide that. The state has to protect its citizens from environmental pollution.”

Many say a migration ban alone is not enough to resolve the pollution problem. The real issue, experts and locals say, is the stark divide between the city and the countryside. Erdeneburen Ravjikh, the former state secretary of Mongolia’s ministry of construction and urban development, is on a mission to reverse this mass migration and repopulate the countryside.

Growing up in the steppe of southern Mongolia, Erdeneburen thought a lot about how to upgrade his rural hometown, Gurvansaikhan. There was no central heating, just coal-fired metal stoves. Getting water required a mile-long trek, and the bathrooms – wooden stalls outside – were brutal during the winter when temperatures fell to as low as -40C.

“I used to freeze my arse off,” he says.

Most families lived in gers, and made their living by raising goats and selling cashmere. Many of the people Erdeneburen grew up with have left. He has also spent most of his adult life outside his hometown.

“To fight air pollution, we need to develop the rural areas, to make life good so people stay,” he says. “The main reason people move to Ulan Bator is the quality of life – having proper heating, proper toilets, good water supply.”

After four years of fundraising, designing, and construction, today, Gurvansaikhan looks more like a suburban neighbourhood dropped in the middle of the Gobi desert. Paved roads cut through the town, lined with solar-powered lamps. Residents share a waste water treatment plant, a central heating system, and a water plant. City planners have even kept trees and shrubbery alive in the desert.

Officials at the city, provincial and national level are now working on a programme to encourage citizens to migrate from Ulan Bator to the provinces.

“Creating jobs in the countryside is important. This is what citizens want. They say, ‘I want to go back home, but I need a job’,” Batbayasgalan says.

Convincing people to move will take time. More than half of the country’s GDP is generated in Ulan Bator. Last year when unemployment in the city was 8.7 per cent, in rural areas it was as high as 10.7 per cent.

Erdenechimeg Sanlig came to the capital from the countryside six years ago with her children, following their oldest daughter to university. She goes home once a year and always finds that not much has changed.

“Having animals is difficult,” she says, sitting on a neatly made bed inside their ger, a traditional Mongolian yurt on the outskirts of Ulan Bator or tent.

A television plays the local news. Next to a microwave, a cabinet holds a cup of toothbrushes and a roll of toilet paper. A pink table decorated with images of Disney princesses, for her three granddaughters, sits on the far side of the tent.

“In the countryside our children would not find jobs. It’s better here to find jobs,” she says.

Scientists find first evidence air pollution particles reach mothers’ placentas

Still, increasingly more residents in the ger district are growing tired of life in the capital. Many complain about the food, the congestion, as well as the pollution. Before the ban, migration to the capital had already been falling since 2014. Last year, the number of people leaving Ulan Bator exceeded the amount moving in for the first time since the 1990s.

Zolzaya Amgalan, 32, and her husband Myanganbaatar Tsend, 41, have been here for the last three years with their son and daughter. When their son was a little more than a year old and struggling to walk, a doctor diagnosed him with rickets, and advised the family take a break in the countryside for a year.

“The difference was obvious. In the countryside the air, food, everything is good for the kids,” Zolzaya says. “If there were more development [in the countryside], of course we would move. Everyone would want to move.”