Severe Air Pollution Crisis Hits Northern Thailand

Chiang Mai and other regions of northern Thailand are currently experiencing a severe air pollution crisis, with PM2.5 levels reaching concentrations described as extremely dangerous to human health. The haze, driven by seasonal agricultural burning, forest fires, and specific weather patterns, has significantly reduced visibility and created a public health emergency in the region.

On April 4, 2026, PM2.5 concentrations at Nakornping Hospital in the Mae Rim district reached 409 micrograms per cubic metre at 9:00 AM. This level of pollution caused visibility to plummet, leaving nearby buildings barely visible through the dense haze.

Public Health Impact and Medical Alerts

Health officials have warned that the toxic haze is causing immediate respiratory distress, particularly among vulnerable populations. Patients have reported breathing difficulties as pollution levels intensify throughout the day. Maharaj Hospital reported that the number of patients has surged 1.5 times due to the conditions.

The physical toll on residents working outdoors has been severe. Pon Doikam, a 36-year-old coconut seller in Chiang Mai, reported to AFP that the haze is so intense it has left her nose burning and bloodied, describing the experience as suffocating.

Authorities are urging residents to take the following immediate precautions to mitigate health risks:

• Avoid all outdoor activities, including exercise or prolonged exposure in open areas.
• Use properly fitted N95 masks when going outside, as standard surgical masks cannot effectively filter PM2.5 particles.
• Create indoor safe zones by sealing windows and utilizing air purifiers.
• Seek immediate medical attention for symptoms such as chest tightness, cough, eye irritation, or difficulty breathing.

Causes and Environmental Factors

The crisis is attributed to a combination of biomass burning and illegal forest fires. Satellite imagery, including data from Suomi NPP VIIRS, has identified large clusters of hotspots across Chiang Mai province and adjacent northern regions. These fires are located in both farm zones, often linked to field clearing after harvest, and protected forest areas, which suggests unlawful activity.

Dry weather and ongoing fires have sustained the haze for several days. In late March 2026, the Chiang Mai Municipality reported a US AQI of 181, placing the city in the Unhealthy category. At that time, PM2.5 levels were recorded at 98.1 micrograms per cubic meter, which is approximately 19 to 20 times the annual guideline set by the World Health Organization.

Based on IQAir data, Chiang Mai was ranked as the third most polluted major city in the world, trailing only Beijing and Delhi.

Government and Emergency Response

In response to the escalating crisis, disaster status has been declared in three northern Thai provinces. The government has mobilized aircraft to combat the PM2.5 levels and address the wildfires contributing to the smoke.

Despite these measures, residents who have lived in the region for decades have described the current pollution levels as exceptional. Pon Doikam stated that in her experience living in Chiang Mai since childhood, this is the worst the pollution has ever been.