Heavy haze forced at least three flights due to land at Chiang Mai airport to turn back yesterday as the province was ranked worst in the US Air Quality Index (AQI) at 2pm yesterday.
Airport authorities reported the haze reduced visibility at the airport from 2,000 metres to 1,300 metres. Three incoming commercial flights from Bangkok were turned back, one to the capital and two others to Chiang Rai and Phitsanulok.
In downtown Chiang Mai, the municipal office deployed water trucks which sprayed mist to curb the haze. At the Tha Phae gate, sprinklers were also turned on to help humidify the area.
One of the hardest hit spots in Chiang Mai was tambon Chang Puek in Muang district where the PM2.5 pollutant reading stood at 199 microgrammes per cubic metre of air, which exceeds the safe level.
The Prince Royal's College in Muang district announced it has cancelled classes tomorrow and Tuesday.
At 2pm yesterday, Chiang Mai topped the worst air pollution chart with a US AQI of 452, followed by Denpasar in Indonesia with 175 US AQI.
According to the Air4Thai website run by the Pollution Control Department, many areas of the upper North were marked red, signifying a surge in the PM2.5 level at 2pm yesterday.
In Mae Sariang district of Mae Hong Son, water trucks were sent to communities to pump out mist to thin out the haze reported to be severe in the past three days.
In tambon Jong Kham of Muang district, the PM2.5 level reached 174 microgrammes per cubic metre of air, which poses a health hazard.
A survey by the authorities found 162 forest fire hot spots across seven districts of the mountainous province.
Chayaphon Thitisak, director-general of the Disaster Prevention and Mitigation Department chief, said vast areas of nine provinces -- Chiang Mai, Chiang Rai, Lampang, Lamphun, Mae Hong Son, Nan, Phrae, Phayao and Tak -- were battling the haze yesterday.
The PM2.5 in the affected red zones of the nine provinces was measured at between 59-199 microgrammes per cubic metre of air.
The department is working with local authorities to constantly monitor the air quality in the North and mobilise resources, manpower and equipment to deal with the problem.
Forest fires are mainly blamed for the thick haze.
The authorities have strictly enforced a ban on the slash-and-burn practice by farmers in the mountains which created the hot spots.
Mr Chayaphon said farmers were encouraged instead to pile up the soil to get rid of the weeds rather than burn them.