Unhealthy levels of fine dust remained high in the northern provinces on Monday, held there by stagnant air, while a southerly wind was easing the pollution in Greater Bangkok.
The Pollution Control Department said levels of particulate matter up to 2.5 microns in diameter (PM2.5) ranged from 97 to 225 microgrammes per cubic metre (μg/m³) of air in many northern provinces over the previous 24 hours, as of Monday morning.
Unhealthy PM2.5 were reported in Chiang Mai, Chiang Rai, Mae Hong Son, Nan, Phitsanulok and Sukhothai provinces. The worst reading was in tambon Chong Kham of Muang district in Mae Hong Son province.
The safe threshold is set…