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 ).
In Ulaanbaatar, Mongolia's rapidly expanding capital, light falls in a soft yellow haze over the centre and surrounding suburbs.
Coal smoke fills the air, interspersed with a more acrid, throat-tickling taste of burning plastic.
However, this year, many in Ulaanbaatar started to raise their voices in protest at pollution levels, with two large demonstrations in the capital.
On January 28 thousands gathered in the city center carrying black balloons.
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.
In 2009 nearly eight million animals were wiped out in one of Mongolia's worst ever winters, destroying the herds of 9,000 families.
Researchers studying the impact of pollution estimate 29 percent of cardiopulmonary deaths, and 40 percent of lung cancer deaths in Mongolia are caused by pollution.
In a bid to fight the recent outbreak of influenza and pneumonia, the Central Military Hospital opened 50 beds for children to deal with overspill from other hospitals, while the mayor requested 30 new beds to be added to the Second Central Hospital in January.
The city's center has modern skyscrapers that look out over a sea of Soviet tower blocks.
Beyond this brutalist crust are 180,000 gers, or yurts, home to the city's most recent arrivals.