CHIANG MAI, THAILAND – Northern Thailand faced dangerously toxic air as authorities issued the highest pollution alert for nine areas across four provinces.
Worst-hit districts register extreme PM2.5 levels
According to the latest readings from 28 March 2026, fine dust (PM2.5) levels in nine areas of Chiang Mai, Chiang Rai, Lamphun and Mae Hong Son far exceeded acceptable health limits. The Li district in Lamphun recorded a critical value of 198.3 micrograms per cubic metre, nearly five times the World Health Organization guideline.
Wiang Phang Kham in Mae Sai, Chiang Rai, followed with 186.1 micrograms per cubic metre. Muang Na in Chiang Dao, Chiang Mai, also reached a highly dangerous peak of 167.9 micrograms.
Four consecutive days in the red zone
Officials expressed particular concern about the duration of exposure. The areas of Wiang Phang Kham (Mae Sai, Chiang Rai) and Li (Lamphun) had remained in the red dust zone continuously since 25 March 2026.
Residents there had breathed toxic air without interruption for four days, with potentially severe health consequences. The Environmental and Pollution Control Office 1 in Chiang Mai warned:
“The air quality is in the range from ‘beginning to affect health’ (orange) to ‘affecting health’ (red).”
said the Environmental and Pollution Control Office 1.
More locations on the danger list
Beyond the top hotspots, several other districts were also classified at risk. The red list covered nine areas across the four northern provinces.
These included Wiang, Chiang Khong, Chiang Rai (152.2 micrograms), Wiang Tai, Pai, Mae Hong Son (138.9 micrograms) and Mueang, Chiang Rai (94.1 micrograms). Chang Kheng, Mae Chaem, Chiang Mai (83.7 micrograms), Ban Klang, Mueang, Lamphun (77.5 micrograms) and Mae Sariang, Mae Hong Son (76.0 micrograms) were also affected.
In all these locations, the air already posed a serious health risk for sensitive groups.
High-risk groups urged to stay indoors
Authorities issued urgent appeals to the public, with a strong focus on those most vulnerable. Children, older people, individuals with chronic conditions such as asthma or cardiovascular disease, and pregnant women were identified as key risk groups.
A spokesperson stressed that these people should avoid going outdoors wherever possible.
“If you belong to one of these groups, you must absolutely avoid being outside,”
said a spokesperson for the Environmental and Pollution Control Office 1.
Anyone experiencing symptoms such as coughing, shortness of breath or eye irritation was urged to seek medical attention immediately.
Protective measures for residents and tourists
Authorities issued clear guidance on how to reduce exposure. Every time people left their homes, they were advised to wear a proper PM2.5 protective mask, as ordinary cloth masks were deemed insufficient.
Outdoor activities were to be kept to an absolute minimum, and exercise outside was described as completely off limits. Windows should remain closed to prevent polluted air from entering homes, while air purifiers could help improve indoor air quality.
People with asthma or other respiratory diseases were told to keep their medication within easy reach at all times. Both residents and tourists in the affected areas were asked to follow these instructions strictly.
Burning ban and call to reduce emissions
Officials also appealed to the public to stop all forms of open burning. People were urged not to burn agricultural waste, rubbish or garden debris, as any additional fire would worsen the already critical situation.
Motorists were asked to avoid using vehicles that produced excessive smoke.
“Everyone can do their part to help reduce the pollution load,”
said the Environmental and Pollution Control Office 1.
How to monitor current air quality
The Environmental and Pollution Control Office provided daily updates on current measurements. Information was made available via the Facebook page “Office of Environmental and Pollution Control at 1”.
Up-to-date values for each region could also be checked on the website air4thai.pcd.go.th and through the Air4thai app. Officials indicated that the situation remained tense, with no significant improvement expected in the coming days.