Levels of PM2.5 fine dust reached the "unhealthy" red zone in the northern province of Lampang -- at 104-134 microgrammes per cubic metre of air -- over the past 24 hours, due partly to forest fires.
The Pollution Control Department reported the high levels of particulate matter of 2.5 micrometres or less in diameter (PM2.5) on Tuesday morning. The safe threshold in Thailand is set at 50mcg.
Average PM2.5 levels over a 24-hour period were 104mcg in tambon Phra Bat of Muang district, 112mcg in tambon Mae Mo of Mae Mo district, 116mcg in tambon Sob Pad of Mae Mo district, and 134mcg in tambon Ban Dong of Mae Mo -- all in the 'red zone'.
Levels of airborne pollutants at 10am on Tuesday. (Screenshot from aqmthai.com)
Airborne carcinogenic pollutants were especially thick on Vajiravudh Damnoen Road (Lampang-Denchai) from Mae Tha district, Mae Mo up to Doi Phra Bat mountain in Muang district. Officials said stagnant air trapped smoke haze from forest fires on Doi Phra Bat.