Unsafe levels of ultrafine dust blanketed 48 out of the 76 Thai provinces, and Bangkok, on Tuesday, with red levels in parts of the Central Plain and the East, the Geo-Informatics and Space Technology Development Agency (Gistda) reported.
Gistda reported at 9am that red levels (hazardous to health) of particulate matter 2.5 micrometres and less in diameter (PM2.5) ranged from 75.1 to 90.8 microgrammes per cubic metre of air over the past 24 hours in seven provinces, mostly in the Central Plain.
In descending order of PM2.5 levels, they were Samut Sakhon, Samut Songkhram, Nakhon Pathom, Ratchaburi, Chai Nat, Sing Buri and the eastern province of Chon Buri. The government-set safe threshold is 37.5µg/m³.
Twenty-nine provinces had safe air. Of these, 25 provinces had moderate air quality represented with yellow levels of PM2.5 ranging from 25.4 to 37.4µg/m³. They included Chiang Mai, Krabi, Mae Hong Son, Nakhon Si Thammarat, Phuket and Surat Thani.
Four southern provinces had good air quality with green levels of PM2.5 ranging from 21.7 to 23.6µg/m³. They were Chumphon, Phatthalung, Ranong and Trang.
Forty-one provinces were shrouded with orange levels (starting to affect health) of PM2.5 ranging from 38.6 to 73.3µg/m³. They included Ayutthaya, Bangkok, Chiang Rai, Kanchanaburi, Nakhon Ratchasima, Phetchaburi, Prachuap Khiri Khan and Samut Prakan.