Most provinces in the North were blanketed with dangerous red-coded levels of PM2.5 on Monday morning, with Chiang Mai rated the city with the worst air pollution in the entire world.
The Geo-Informatics and Space Technology Development Agency (Gistda) reported at 8am on Monday that 14 provinces were facing red (seriously harmful) levels of particulate matter 2.5 micrometres and less in diameter (PM2.5), ranging from 75.9 to 173.6 microgrammes per cubic metre of air over the past 24 hours. The safe threshold is at 37.5µg/m³.
The worst level, 173.6, was measured in Mae Hong Son, followed by 153.1 in Chiang Mai, 152.2 in Chiang Rai, 140.8 in Lamphun, 138.6 in Phayao, 128.9 in Lampang, 125.5 in Nan, 118.9 in Phrae, 105.8 in Uttaradit, 103.4 in Tak, 101.4 in Sukhothai and 88.1 in Kamphaeng Phet. All of them are northern provinces.
Two provinces in the upper Northeast also suffered red levels of PM2.5 – 85.9 in Loei and 75.9 in Bueng Kan.
Orange (initially unsafe) levels of PM2.5 were detected in 20 other provinces, mostly in the Northeast. They ranged from 39.2 to 74.6µg/m³.
The provinces were, in descending order, Nakhon Phanom, Phitsanulok, Nong Bua Lam Phu, Udon Thani, Sakon Nakhon, Phetchabun, Kalasin, Nong Khai, Khon Kaen, Mukdahan, Chaiyaphum, Maha Sarakham, Phichit, Amnat Charoen, Roi Et, Yasothon, Ubon Ratchathani, Uthai Thani, Kanchanaburi and Nakhon Sawan.
Provinces in the lower Central Plain, the lower Northeast and the South had moderate and good air quality. Samut Prakan had the best air quality with 10.6µg/m³ of PM2.5, followed by Bangkok with 11.5µg/m³.
Swiss air quality technology company IQAir rated Chiang Mai as the major city with the world's worst air pollution on Monday morning, followed by Jakarta, Hanoi and Hangzhou.
The map from Gistda shows red levels of PM2.5 blanketing the North on Monday morning.