Fifty-seven out of 77 provinces in Thailand were blanketed with unsafe levels of ultrafine dust pollution on Monday morning, according to the Geo-Informatics and Space Technology Development Agency (Gistda).

Thirteen provinces faced red levels (hazardous to health) of PM2.5, Gistda reported at 8am.

Nong Bua Lam Phu suffered the highest red level of PM2.5 at 99.1 microgrammes per cubic metre of air over the past 24 hours.

Bangkok had 75.5µg/m³, and the government-set safe threshold is 37.5µg/m³.

Twenty provinces had safe air quality. They are in the North and the South.

Sixteen provinces had moderate air quality represented by yellow levels of PM2.5 ranging from 27 to 36.5µg/m³.

Good air quality was detected in Krabi (24), Lamphun (22.1), Chiang Mai (19.2) and Mae Hong Son (16.5).

Forty-four other provinces faced orange levels (starting to affect health) of PM2.5 ranging from 44.1 to 74.8µg/m³. They included Ayutthaya, Kanchanaburi, Nakhon Ratchasima, Prachuap Khiri Khan, Rayong and Samut Prakan.