Fifty-four out of 77 provinces in Thailand were blanketed with hazardous levels of ultrafine dust on Thursday morning, with 27 provinces, mostly in the North and the Northeast, experiencing red (seriously harmful) levels of pollution.
The Geo-Informatics and Space Technology Development Agency (Gistda) reported at 11am on Thursday that the highest level of particulate matter 2.5 micrometres and less in diameter (PM2.5) was detected in the northernmost province of Chiang Rai, at 128.8 microgrammes per cubic metre (µg/m³) of air over the past 24 hours. The government's safe threshold for PM2.5 is 37.5 µg/m³, while the World Health Organization (WHO) guidelines recommend 25 µg/m³.
After the worst level in Chiang Rai, Tak faced a PM2.5 level of 120.1 µg/m³, followed by Chiang Mai (116.5), Mae Hong Son (113.8), Lamphun (113.8), Phayao (111.1), Nan (108.8), Lampang (103.8), Loei (94.8), Phrae (91.2), Nong Khai (90.5), Kamphaeng Phet (87.2), Nong Bua Lam Phu (85.6), Amnat Charoen (84.8), Udon Thani (83.8), Uttaradit (83.1), Sukhothai (82.7), Khon Kaen (81.6), Yasothon (81.6), Bung Kan (81.4), Kalasin (79.4), Sakon Nakhon (79.0), Maha Sarakham (78.1), Nakhon Phanom (77.1), Mukdahan (76.4), Roi Et (76.2) and Ubon Ratchathani (76.1).
The map from Gistda shows thick levels of PM2.5 in red mainly in the North and the Northeast at 11am on Thursday.
Twenty-seven other provinces, mostly in the Central Plains, reported orange (initially harmful) levels of PM2.5. They were Phitsanulok, Phetchabun, Chaiyaphum, Si Sa Ket, Surin, Buri Ram, Nakhon Ratchasima, Uthai Thani, Phichit, Nakhon Sawan, Kanchanaburi, Sing Buri, Chai Nat, Sa Kaeo, Lop Buri, Suphan Buri, Prachin Buri, Ang Thong, Saraburi, Trat, Chanthaburi, Nakhon Nayok, Ayutthaya, Narathiwat, Chachoengsao, Phetchaburi and Pathum Thani.
PM2.5 levels were safe in Bangkok, its nearby provinces and a number of southern and eastern provinces.
On Thursday, the Meteorological Department warned that summer storms and gusty winds are expected in the northern and northeastern regions as well as the Central Plains, including Bangkok, from Friday to Sunday.