Chiang Mai was ranked the most polluted major city in the world on Monday 30 March, as forest and man-made fires pushed air quality to hazardous levels across the northern province. Swiss air monitoring firm IQAir reported an Air Quality Index (AQI) of 263 at 10am, classified as “very unhealthy”, with PM2.5 levels measured at 188.0 microgrammes per cubic metre. The pollution level far exceeded that of Delhi, the second most polluted city, which recorded an AQI of 198 and PM2.5 at 122.0.

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The severe smog was forecast to persist until around 4pm on Monday before gradually improving through the rest of the day and continuing to ease until at least Wednesday. Authorities linked the pollution to a surge in fire hotspots, driven by seasonal bushfires, agricultural burning, and deliberate fire-setting. On Sunday, Chiang Mai recorded 480 hotspots, nearly double the 247 detected in neighbouring Mae Hong Son, according to the Department of National Parks, Wildlife and Plant Conservation.

Despite repeated legal warnings, the number of hotspots has remained high. Department director-general Atthaphon Charoenchansa said on Sunday that the situation was worrying and reiterated strict penalties for offenders. Starting a fire in a state-protected area can result in fines ranging from 400,000 to 2 million baht and prison sentences of four to 20 years.

The Environmental and Pollution Control Office in Chiang Mai warned residents in at least 12 areas of the province and three neighbouring provinces about dangerous accumulations of fine particulate matter. The warning highlighted the health risks posed by prolonged exposure to PM2.5 pollution, particularly for vulnerable groups. Officials have urged the public to take precautions while enforcement efforts continue against illegal burning.

The Bangkokpost reported that authorities expect air quality to improve in the short term as weather conditions change, but the persistence of hotspots suggests the broader problem may continue. Efforts to control fires and enforce regulations are likely to intensify as officials attempt to reduce pollution levels and limit further environmental damage.

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Adapted by ASEAN Now Bangkokpost 31 Mar 2026

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Same as every year

But I have a filter in my room.