Hazardous levels of PM2.5 dust were again recorded in the North and upper Northeast on Monday morning, peaking at 550 microgrammes per cubic metre of air over 24 hours in Chiang Rai's Mae Sai district.
The Pollution Control Department reported the levels of particulate matter 2.5 micrometres and less in diameter (PM2.5) ranged from 37-550 microgrammes per cubic metre of air in the region over the past 24 hours as of 10am. The government-set safe threshold is 50, higher than in most countries.
The PM2.5 level was recorded at 37 in Muang district of Tak, which appeared to be the only "safe" area in the North.
PM2.5 levels north of Tak included 550 in Mae Sai district of Chiang Rai, 304 in Pai district of Mae Hong Son, 290 in Chiang Dao district of Chiang Mai, 278 in Chiang Khong district of Chiang Rai, 268 in Chaloem Phra Kiat district of Nan, 131 in Muang district of Phrae and 113 in Muang district of Chiang Mai.
In the upper Northeast, PM2.5 levels reached 93 in Muang district of Loei, 96 in Muang district of Nakhon Phanom, in Muang district of Nong Khai and 222 in Muang district of Bueng Kan.
The Ministry of Natural Resources and Environment attributed the intense air pollution to burning of farmland, smoke haze from other countries and stagnant air.
PM2.5 levels were lower and at safe levels in other parts of the country, cleared by southerly winds.
The Geo-Informatics and Space Technology Development Agency reported there were 5,572 fire hotspots in the country, the highest in five years.
According to Gistda, the weather satellite Suomi NPP detected the most hotspots on Sunday. The majority were in forests, 4,767, with 376 hotspots in farmland.
Nan province had the most hotspots, 638, followed by 558 in Mae Hong Son and 430 in Uttaradit.
On Sunday, there were 10,563 hotspots in Myanmar, 9,652 in Laos, 1,342 in Cambodia, 870 in Vietnam and 22 in Malaysia.
Two rain-making planes were being used in Chiang Mai province on Monday in an effort the reduce the dense smog.
