Bush fires were blamed for severe haze that blanketed Chiang Mai with ultra-fine PM2.5 dust particles exceeding the safe level on Saturday.
The province was shrouded in a thick haze from bushfires, according to a source, adding the haze was so severe that the Doi Suthep mountain peak was no longer visible from downtown Chiang Mai city.
Locals also began complaining about eye and nasal irritation, the source said.
The highest PM2.5 level was measured at 104 microgrammes per cubic metre (μg/m³) -- exceeding the government's 50μg/m³ safe exposure threshold -- in tambon Mae Sa in Mae Rim district, the source said, noting the PM2.5 levels at 50 other air quality monitoring stations in the province also recorded high levels.
Bushfires by illegal wildlife poachers was to blame for the hazardous condition in Chiang Mai, he said.
In neighbouring Lampang, the provincial disaster prevention and mitigation office reported 117 wildfire hotspots detected in 12 districts, citing information provided by a satellite survey by the Geo-Informatics and Space Technology Development Agency (GISTDA).
Most of the hotspots were found in forest reserve areas, mostly in Thoen district, where up to 30 such hotspots were found, followed by Mae Phrik district where 26 hotspots were reported.
The mitigation office said more than 200 wildfire hotspots have been spotted in this part of Lampang since last month, resulting in spikes of between 68 to 87μg/m³.
Teerapat Prayoonsit, chairman of the government's subcommittee on air pollution resolution, yesterday said Bangkok should brace for a new wave of air pollution today, and again on Wednesday and Friday.