Unsafe levels of ultrafine dust were detected across Bangkok and 30 other provinces on Sunday morning, with pollution concentrated largely in the Central Plains, according to the Geo-Informatics and Space Technology Development Agency (Gistda).
The agency reported at 8am that concentrations of particulate matter measuring 2.5 micrometres or less in diameter (PM2.5) ranged from 37.8 to 62.6 microgrammes per cubic metre (µg/m³) of air in Bangkok and surrounding provinces.
These readings exceeded the government’s safety threshold of 37.5µg/m³, indicating unhealthy air quality for sensitive groups and the general population.
Sing Buri recorded the highest PM2.5 level nationwide at 62.6µg/m³, placing it firmly in the unhealthy category.
Several neighbouring provinces also experienced heavy smog, including Samut Sakhon and Samut Prakan, while Bangkok itself was among areas facing unsafe pollution levels.
Other provinces affected by thick haze included Ang Thong, Nakhon Pathom, Pathum Thani, Nonthaburi and Ayutthaya. Elevated readings were also reported in Samut Songkhram, Chai Nat, Ratchaburi, Lop Buri, Saraburi and Suphan Buri.
Further inland, pollution spread to Phetchaburi, Chachoengsao, Kanchanaburi, Uthai Thani, Nakhon Ratchasima, Nakhon Nayok and Prachin Buri.
Southern and border provinces were not spared, with unsafe PM2.5 levels recorded in Prachuap Khiri Khan, Yala, Pattani, Phatthalung, Narathiwat, Songkhla and Sa Kaeo. Nong Khai and Nakhon Sawan were also listed among affected areas.
In contrast, air quality in the North remained favourable. Chiang Mai, Chiang Rai, Mae Hong Son and Nan reported very good conditions, with PM2.5 levels between 9.9 and 14.9µg/m³.
According to the agency, other provinces nationwide recorded air quality ranging from good to moderate, based on monitoring data collected on Sunday morning.
