Bush fires caused by open burning on farms yesterday sent the level of PM2.5 to 484.23 microgrammes per cubic metre at Song Hospital in Phrae province, according to an air quality monitoring system developed by the Climate Change Data Centre of Chiang Mai University.
The World Health Organization (WHO) sets the safe maximum level of PM2.5 at 25 microgrammes per cubic metre (µg/m³) while Thailand's Pollution Control Department (PCD) opts for a more liberal limit of 50µg/m³.
This air quality measurement tool known as "Dust Boy" was developed by Chiang Mai University researchers and has been used by villagers in the northern region since 2018.
Data is collected by 800 small air-monitoring machines developed by Chiang Mai researchers and shows air quality in real-time. The price of each monitor is about 5,000 baht.
Meanwhile, levels of PM2.5 in Chiang Mai's in tambon Bong Tan of Doi Tao district spiked at 476 µg/m³ reportedly because of bushfires on the mountains in Doi Tao district on Sunday near Wat Phra Borommathat Doi Koeng, with the fire then expanding to adjacent Hot and Chom Thong districts.
The PCD blamed the fires on farmers conducting open burning to clear their land.
Data from Air4Thai, the official PCD air monitoring station went in the same direction. The PCD's air monitoring quality is known for its conservative estimations as it calculates average air quality over 24 hours.
It reported that the average PM2.5 level yesterday in Lampang, Phrae and Nan were in the "red zone," and exceeded 100 µg/m³.
In Phrae, the fine dust rose to 152 µg/m³ while Lampang recorded 144 µg/m³ in tambon Phrabat of Muang district. In Nan, tambon Nai Wiang of Mueang district was measured at 95 µg/m³.
Col Sirichan Ngathong, deputy spokeswoman for the Royal Thai Army, said yesterday the army has arranged for helicopters to help douse forest fires and to release water droplets into the atmosphere to clear the air of harmful dust in Lampang, Phrae, Nan, Phayao and Tak.
Meanwhile, in Bangkok, Metropolitan Police Bureau chief Pakkapong Pongpetra said over 9,000 drivers have been told by police to reduce the amount of black smoke coming from their vehicles' exhausts.
However, air quality in the capital has improved massively during the past week with PM2.5 levels having dropped to an average of between 20-40 µg/m³.