The levels of small particle matter of up to 10 microns in diameter (PM10) were recorded at 143 and 157 micrograms per cubic metre in Lampang and Lamphun respectively. The safe limit is 120. The Lampang reading was taken in Tambon Sob Pad in Mae Mo district and Lamphun reading was recorded in Tambon Nai Muang in Muang district, said Phasit Seuksanapapat of the Chiang Mai Provincial Office for Natural Resources and Environment.

The other northern provinces’ PM10 readings remained within the safe level, he said, adding that Chiang Mai recorded a high of 106 micrograms.

The region’s 60-day outdoor-burning ban would be enforced from today, he said, so the smog situation should be less severe.

However, Agriculture and Cooperatives Ministry spokesman Surapol Jarupong urged the Land Development Department, the Department of Agriculture Extension and the Department of Royal Rainmaking and Agricultural Aviation to implement measures to stop farmers in 10 northern provinces from burning agricultural waste.

The 2015 statistics found that such outdoor burning covered 1.83 million rai (293,000 hectares) of farmland in the 10 provinces, with some 200 tambons reporting high levels of outdoor burning activities, Surapol added.