Graph showing variation in levels of PM10 pollution is four northern cities – Orange, Phrae Green,Phayao Green, Nan Red and what appears to be faulty equipment in mountainous Loei.
During this period the best air quality was in Nan.
Over 17 years ago a program working with villagers in the north of the province was undertaken to prevent and control smoke and fire.
The motivating factor at the time was the forced closure of the airport at Nan due to smoke.
It appears the beneficial results are continuing nearly 20 years after the program inception.