By Victoria Whall
BBC News, Ulan Bator
Mongolia is known fondly as the Land of Blue Sky by those who live here, but in the winter months the capital Ulan Bator is often shrouded in dense smoke.
Ulan Bator's famous blue skies are turning to grey
The city lies in a valley surrounded by mountains, so grey clouds of smoke can get trapped between them and shroud the city for hours on end.
Entire buildings disappear from view in some areas because of the smoke, and airlines often blame poor visibility when they cancel or delay international flights in and out.
The smoke can make it hard to breathe and it's affecting the health of Ulan Bator's burgeoning population.
The director of the environmental health research centre in Ulan Bator, Dr N Saijaa, said: "The mortality rate is increasing, people's health is getting worse and the incidence of respiratory diseases such as bronchitis, pneumonia and lung cancer has increased."
Mongolia is one the most sparsely populated countries in the world, with about 2.6 million people. But it is becoming increasingly urbanised - according to the UN Population Fund, 60% of the population live in urban areas, approximately one third of them in Ulan Bator.
Sarantuya Myagmarjav, an official at the ministry of nature and environment, says that migration to the capital increased in 1991 due to economic and social problems in rural parts. At that time the country was in transition to a market economy.
Districts of traditional tents or gers have sprung up
Since then, the trend has continued with people moving to Ulan Bator in order to find work, get an education and in the hope of a better life.
The latest figures from the statistical department of the city governor's office show that more than 220,000 people moved to Ulan Bator between 2000-2006.
As apartments are relatively expensive and limited in number, many of those moving to the city set up their traditional felt tents - or gers - in informal settlements called ger districts.
In the ger districts there is no access to the city's main water supply so people continue the tradition of burning coal, wood and whatever else they can find to heat their homes.
The ger districts contribute in large part to the air pollution. But the city's three coal-fired power stations and an ever increasing number of cars also contribute to the winter smog.
Question of survival
Tuvshinjargal, her husband and five children moved to one of Ulan Bator's ger districts in 2001. The family used to live in a small village 95 km (59 miles) away, where they used to help look after her sister's livestock.
When most of the herd perished due to adverse weather conditions, her sister could not support the family any more.
Tuvshinjargal thought her children would get a better education
"If you don't have any livestock there's no way to live in the countryside. Plus there are no jobs so you can't afford your living expenses," Tuvshinjargal said.
"We wanted to improve our lives and had more hope of finding work in Ulan Bator."
Another factor, says Tuvshinjargal, was their children's education.
"We thought it would be better to get our children into school in Ulan Bator as it can be hard to get in to schools in the countryside."
The family burns coal to keep their ger warm. They have access to electricity but like many families in the ger districts, cannot afford to use it to heat their homes.
"For us it's a big problem because our finances are not that good, so we just use coal not an electric heater," Tuvshinjargal explained.
The Air Quality Management Department of the Institute of Meteorology and Hydrology and Environmental monitoring measures the levels of nitrogen dioxide and sulphur dioxide in the air at four points around the city.
In the month of January, the levels of both gases were above the Mongolian standard almost every single day. But the measurements do not tell the whole story as levels of other pollutants such as particulates are not being monitored due to a lack of technology.
The mountains surrounding Ulan Bator are barely visible
Although the pollution is not a new phenomenon, this year there seems to be more of an impetus to do something about it.
In December, the editors of several daily papers wrote a joint letter asking the international donor community for help in reducing air pollution. Since then they and the country's broadcast media have kept the issue in the minds of the public with a barrage of news reports on pollution.
In response, the speaker of parliament has set up a working group to look at ways to reduce the problem. The group - made up of specialists and members of parliament - is putting together an action plan.
Sarantuya Myagmarja, who has played a major role in drafting the plan, says it will include:
- amendments to the law
- various projects designed to encourage the use of alternative fuel
- a review of ways of tackling migration to the city.