Chiang Mai Faces Hazardous Smog as Agricultural Burning and Wildfires Drive Record Air Pollution in Northern Thailand

A toxic smog emergency continues to escalate across northern Thailand, with Chiang Mai repeatedly ranking among the world’s most polluted cities as wildfire smoke and agricultural burning drive hazardous air quality levels.

On March 29, Chiang Mai topped IQAir’s global pollution index with an AQI of 263, recording PM2.5 levels of 188 micrograms per cubic meter. The city remained in the “Very Unhealthy” range throughout the final week of March, with air quality showing no immediate signs of improvement due to its mountainous basin geography that traps smoke from regional fires.

By March 30, Chiang Mai had risen to number one globally on IQAir’s real-time rankings with an AQI of 233, as PM2.5 concentrations reached 188 micrograms per cubic meter — a level classified as “Very Unhealthy” for all population groups under U.S. Air quality standards. Agricultural burning of rice, sugarcane, and maize fields, combined with forest fires originating in Laos, Myanmar, and Cambodia, has been identified as the primary driver of the crisis.

In early April, pollution levels worsened significantly. On April 4, PM2.5 spiked to 409 micrograms per cubic meter at Nakornping Hospital in Mae Rim, far exceeding the World Health Organization’s daily safety guideline of 15 micrograms per cubic meter. By mid-April, hazardous conditions persisted across 39 provinces, with northern regions including Chiang Mai, Chiang Rai, and Nan recording PM2.5 readings between 56.7 and 228.8 micrograms per cubic meter.

Air quality in Chiang Mai has frequently exceeded an AQI of 200 this season, placing it in the “Very Unhealthy” category, with some days reaching “Hazardous” levels where health risks apply to the general population, not just vulnerable groups. Medical officials have warned that the fine particulate matter poses serious lung risks due to its ability to penetrate deeply into respiratory systems.

Tourism in nearby Pai has collapsed as the hazardous haze drives visitors away, compounding economic strain on communities already burdened by health concerns. Local authorities have been ordered to intensify efforts to combat PM2.5 pollution, though relief remains elusive as seasonal burning continues across the region.

The crisis has prompted national discussions about reevaluating agricultural practices, particularly rice stubble burning, as part of broader efforts to address Thailand’s recurring seasonal smog problem. Officials face mounting pressure to implement effective measures that balance environmental protection with the livelihoods of farming communities dependent on traditional land-clearing methods.