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 fourth worst air pollution in the entire world.
The Geo-Informatics and Space Technology Development Agency (Gistda) reported at 8am on Monday that 11 provinces were facing red (seriously harmful) levels of particulate matter 2.5 micrometres and less in diameter (PM2.5), ranging from 82.1 to 158.8 microgrammes per cubic metre of air over the past 24 hours. The safe threshold is at 37.5µg/m³.
The worst level, 158.8, was measured in Chiang Rai, followed by 141.9 in Chiang Mai, 136.4 in Lamphun, 131.6 in Phayao, 128.2 in Mae Hong Son, 118.6 in Lampang, 102.3 in Phrae, 94.9 in Nan, 87.8 in Sukhothai, 85.5 in Uttaradit and 82.1 in Tak. All of them are northern provinces.
Orange (initially unsafe) levels of PM2.5 were detected in 46 other provinces, mostly in the Northeast and the Central Plains. They ranged from 38.2 to 67.6µg/m³.
The provinces were, in descending order, Loei, Kamphaeng Phet, Phitsanulok, Phetchabun, Chaiyaphum, Phichit, Nakhon Sawan, Khon Kaen, Uthai Thani, Bangkok, Maha Sarakham, Kanchanaburi, Mukdahan, Kalasin, Roi Et, Pathum Thani, Nonthaburi, Nong Bua Lam Phu, Chai Nat, Nakhon Ratchasima, Ubon Ratchathani, Ratchaburi, Si Sa Ket, Amnat Charoen, Yasothon, Samut Prakan, Lop Buri, Udon Thani, Nong Khai, Phetchaburi, Prachuap Khiri Khan, Nakhon Pathom, Suphan Buri, Samut Sakhon, Ayutthaya, Nakhon Nayok, Sing Buri, Surin, Bueng Kan, Buri Ram, Samut Songkhram, Ang Thong, Saraburi, Prachin Buri, Sakon Nakhon and Nakhon Phanom.
Provinces in the East and the South had moderate and good air quality. Phuket had the best air quality with 15.3µg/m³ of PM2.5, followed by Phang Nga with 15.7µg/m³. Both are in the South.
Swiss air quality technology company IQAir rated Chiang Mai as the major city with the world's fourth worst air pollution on Monday morning after Delhi, Lahore and Kathmandu.
The map from Gistda shows red levels of PM2.5 in the North on Monday morning.