Air pollution hazardous or moderately dangerous to health was detected in 58 out of 77 provinces across Thailand on Thursday morning.
The Geo-Informatics and Space Technology Development Agency (Gistda) reported on its website at 9am that ultrafine dust reached red (hazardous) levels in 20 provinces and orange (starting to affect health) levels in 38 provinces.
Red levels of particulate matter 2.5 micrometres and less in diameter (PM2.5) were reported in 20 provinces, mostly in the Central Plains. They ranged from 73.5 to 117.1 microgrammes per cubic metre of air over the past 24 hours. The safe threshold is 37.5µg/m³.
The highest red level, 117.1, was in Samut Sakhon, followed by Samut Songkhram (109.1) and Rayong (103.9).
Seventeen other provinces faced two-digit red levels ranging from 75.3 to 99.4.
In descending order, they were Nakhon Pathom, Ratchaburi, Samut Prakan, Phetchaburi, Nonthaburi, Bangkok, Phitsanulok, Pathum Thani, Ayutthaya, Chon Buri, Suphan Buri, Kamphaeng Phet, Chachoengsao, Chai Nat, Uthai Thani, Kanchanaburi and Phichit.
Thirty-eight provinces had pollution classified as orange, ranging from 37.8 to 74.2µg/m³.
PM2.5 was at good and moderate levels, meaning safe to breathe, in 19 provinces. They ranged from 18.8 to 37.4.
Fifteen provinces had moderate (yellow) levels of PM2.5. They were, in descending order, Maha Sarakham, Ranong, Chiang Rai, Chiang Mai, Ubon Ratchathani, Yasothon, Surin, Roi Et, Phatthalung, Amnat Charoen, Si Sa Ket, Nakhon Si Thammarat, Surat Thani, Chumphon and Songkhla.
Four provinces had good (green) levels: Krabi, Phuket, Mae Hong Son and Satun.