Ultrafine dust levels were in the red (hazardous-to-health) in 44 out of Thailand's 77 provinces on Thursday morning, with only six provinces reporting moderate to good air quality.

The Geo-Informatics and Space Technology Development Agency (Gistda) reported at 8am that PM2.5 was at red levels in 44 provinces and at orange (starting to affect health) levels in 27 provinces.

Nineteen provinces were shrouded with three-digit red levels of PM2.5. The government-set safe threshold is 37.5µg/m³.

The highest level of PM2.5 recorded over the preceding 24 hours was 139.6 microgrammes per cubic metre of air in Saraburi province, with 100.7 in Bangkok.

Twenty-five other provinces were at two-digit red levels of PM2.5, ranging from 77 to 99.2µg/m³.

Safe levels of PM2.5 were recorded in six northern and southern provinces.

Five of them had moderate air quality with yellow levels of PM2.5 ranging from 25.6 to 36.7µg/m³. In descending order, they were Ranong, Surat Thani, Chiang Rai, Chumphon and Chiang Mai.

Mae Hong Son was the only one province with good air quality with the green level of PM2.5 at 17.8µg/m³.

Twenty-seven provinces faced orange levels (starting to affect health) ranging from 44 to 72.6µg/m³.