Bad air returns to Chiang Mai

Habitual burning and stagnant air conditions have brought back the annual smog that blankets Chiang Mai in March each year. So far it hasn’t been quite as bad as 2007, but visibility in the mountains has been poor and the air quality index is approaching unhealthy levels.

Tourism in this Northern city takes a knock for a few weeks in March each year as farmers burn fields or mountain sides, contributing think smoke to the ambient air which at times can be dangerous to breathe. At present measuring stations at the airport and in the old town have yet to record any days were the PM<10 index has topped the critical 120 level. This is a measure of the sub 10 microns in the air, which are able to lodge in the membranes of the lungs.

When the measure of parts per million increases above 120, the air is considered unhealthy to breathe, and during one week last year it topped 300. This was a result of unusual climate conditions where a lack of moisture in the air (to bind the particles) and a lack of wind in the Ping valley exasperated the situation.

Such conditions are not expected this year, but travellers with asthma conditions or young children are advised to avoid the city or spend their time here up in mountain reaches or outside of the valley – which acts as a natural trap. By the end of March the hazard usually passes.

In addition to poor breathable air, the natural beauty of the mountainous north disappears as visibility drops. On Thursday March 6th the PM>10 value was measured at 97, and Doi Suithep mountain was barely visible from the city. However, by contrast the industrial suburb of Bangkok, Samut Prakarn had a measure of 186. Lampang is another Northern area particularly at risk, measuring 140.

Pollution Control Department regional air quality data