The levels of particulate matter smaller than 2.5 microns, known as PM2.5, reached dangerous levels in parts of the North and the western region on Thursday morning, while Samut Songkhram was the only province in the red zone, indicating PM2.5 readings exceeded the acceptable standard of 50 microgrammes per cubic meter (µg/m³) of air.
The Geo-Informatics and Space Technology Development Agency (Gistda) reported at 9am on Thursday that the central province of Samut Songkhram, located west of Bangkok, recorded 77.1 microgrammes of PM2.5 per cubic metre of air over the past 24 hours.
Meanwhile, 26 other provinces experienced orange levels of PM2.5, ranging from 38.3 to 69.9µg/m³.
In a descending order of the levels, these provinces were Samut Sakhon, which is adjacent to Samut Songkhram, Ratchaburi, Nakhon Pathom, Phetchaburi, Nonthaburi, Kanchanaburi, Ayutthaya, Suphan Buri, Chai Nat, Ang Thong, Pathum Thani, Lamphun, Uthai Thani, Lop Buri, Bangkok, Saraburi, Nakhon Sawan, Sing Buri, Samut Prakan, Prachin Buri, Prachuap Khiri Khan, Chiang Rai, Nakhon Nayok, Lampang, Tak and Nakhon Ratchasima.
The South and parts of the Northeast, the Central Plains and the East reported safe levels of PM2.5, with the safe threshold set at 37.5µg/m³.
The lowest level, 14.4 µg/m³, was measured in the northeastern province of Amnat Charoen, followed by 15.2 in Krabi, 16.2 in Trat, 18.0 in Phuket and 18.1 in Surat Thani in the South.
Comparatively, Thursday's situation was an improvement over Wednesday morning, with 27 provinces facing unsafe PM2.5 levels, down from 33 on Wednesday. The highest level recorded was 95.2µg/m³ on Wednesday morning, reduced to 77.1µg/m³ on Thursday morning.