Smog from field burning was even worse in the North on Friday with PM2.5 levels at 76-202 microgrammes per cubic metre of air and the highest reading again in Chiang Rai's Mae Sai district, the Pollution Control Department reported.
The levels of particulate matter 2.5 micrometres or less in diameter (PM2.5) rose from its range of 64-199 μg/m³ announced at 9am Thursday.
The peak level in the 24 hours to 9am Friday was 202 μg/m³ reported in tambon Wiang Phang Kham of Chiang Rai's Mae Sai district. The air quality index (AQI) there was at 302, the highest in the country. The deemed safe threshold for PM2.5 is 50 μg/m³ and for AQI it is 100.
Elsewhere in the North, unhealthy levels of PM2.5 were recorded in tambon Mae Pa of Mae Sot district in Tak province; tambon Nai Wiang of Muang district and tambon Huai Kone of Chalerm Prakiat district in Nan province; tambon Ban Tom in Muang district of Phayao province; tambon Ban Klang of Muang district in Lamphun; tambon Wiang of Muang district in Chiang Rai; tambon Na Chak of Muang district in Phrae; and tambon Jong Kham of Muang district in Mae Hong Son.
In Lampang province residents of tambon Phra Bat of Muang district and tambon Sob Pat, tambon Ban Dong and tambon Mae Mo of Mae Mo district suffered most.
In Chiang Mai province, the problem was paramount in tambon Chang Phuak, tambon Sri Phum and tambon Suthep of Muang district and tambon Chang Khoeng in Mae Chaem district.
Pralong Damrongthai, deputy director-general of the Pollution Control Department, said officials would have to be more serious in asking people to stop burning off fields and forests, and would spray water hourly instead of twice a day in affected areas.