The Mongolian capital, Ulan Bator is struggling with an air pollution crisis. During the winter months, air quality is 25 to 30 times worse than internationally accepted standards. The pollution is blamed for deadly respiratory illnesses among city residents, including many children and pregnant women.  The problem is linked to rapid urbanisation, as traditional nomads move to the capital, but continue to live in traditional ger tents heated by burning coal. Purevkhuu Tserendorj, a former…