Levels of PM2.5 pollution surpassed the safe threshold throughout Bangkok on Tuesday morning.
According to the Geo-Informatics and Space Technology Development Agency (Gistda), the satellite-based Check Foon (dust check) air quality app showed 49 districts in the capital had surpassed the safe threshold of 37.5 microgrammes per cubic metre (µg/m³).
There were 10 districts where the dust levels exceeded more than 100 µg/m³, which is considered to have “serious” effects on health, with Bangkok Yai peaking at 107.5.
Dust levels in nine other districts — Bang Kholaem, Thung Kru, Thon Buri, Bang Na, Yannawa, Klong San, Bang Khunthian, Rat Burana and Phra Khanong — ranged from 105 to 107.1.
Wang Thonglang was the only district where the dust level remained at the orange-coded level that began to affect health at 70.3.
In the provinces, the highest level was reported in Samut Sakhon adjacent to Bangkok at 101.6.
Dust levels ranging from 95.6 to 75.4 µg/m³ were reported (from low to high) in Samut Prakan, Pathum Thani, Ratchaburi, Nonthaburi, Ayutthaya, Samut Songkhram, Phetchaburi, Nakhon Pathom, Saraburi, Suphan Buri and Chachoengsao.
Meanwhile, the Thai Meteorological Department said fine dust concentrations would accumulate continuously in Bangkok and adjacent provinces due to weak winds.
The department also said hotspots caused by burning, such as forest fires, had been detected in many areas around neighbouring countries, which also caused the rise of PM2.5 levels throughout the central region of Thailand.
The highest number of hotspots was detected in Cambodia.
The department also warned people to wear face masks in public areas to mitigate the impact on the respiratory system. People can get air quality updates on the Check Foon app, it added.