Poor air quality most likely caused by agricultural burning endangered the health of millions of people living in Southeast Asia on Wednesday, March 16. . The threat was especially acute in Chiang Mai, Thailand, a tourist hub and home to over one million people within the metropolitan area.

Picture: Extensive fires impacted air quality in northern Southeast Asia on 16 March 2022

Picture: Air quality in Chiang Mai, Thailand on 16 March 2022. Red dots indicate air quality in the “unhealthy” range, while orange dots display air quality levels that are “unhealthy for sensitive groups.”

Air quality maps showed dozens of fires burning in northern Thailand and across nearby neighboring Laos and Myanmar. Air quality monitors in Chiang Mai measured unhealthy concentrations of PM2.5 throughout the city – measurements of U.S. AQI reaching as high as 161 – and in neighboring cities and towns. By late afternoon, Mae Hong Son was “very unhealthy” with a US AQI of 229 and Uttaradit measured an AQI of 207. PM2.5 and ultrafine particles are key ingredients of smoke, along with gaseous pollutants.

Chang Mai was the 14th most polluted city in the world among a selection of major cities, with a US AQI of 133. Nearby Yangon, Myanmar was the 11th most polluted city on the list.

“In this region, PM2.5 concentrations are significantly higher during the months of January, February, and March compared to the rest of the year,” said IQAir air quality science manager Dr. Christi Chester Schroeder. “In 2020, the average PM2.5 concentration during this three-month period was anywhere from three to nine times higher than the average for the whole rest of the year for the cities reporting data in this region.”

The Southeast Asia agricultural burning season is a regional environmental and health concern that ignores national boundaries. From December to April of each year, farmers burn crop residue as a low cost and efficient means of clearing fields for future planting. The burns result in clouds of smoke and air pollutants being carried throughout the region and contributing to existing industrial and motor vehicle pollution in cities.

Regional farmers may burn stalks from pigeon pea, cotton, sugarcane, rice, and maize crops. Though open burning practices are illegal in Thailand, farmers often can’t afford the expense of hiring workers to cut and gather leaves and the delay in the next crop cycle.

Picture: Air quality in nearby Yangon, Thailand on 16 March, 2022 ranged from “unhealthy for sensitive groups” up to “unhealthy.”

The regional poor air quality may be far more extensive than is currently visible. Though there are many air quality monitoring stations throughout Thailand, there are none in Laos and only four in Myanmar, all in Yangon. Air quality in Yangon, which is about 227 miles by direct travel from Chiang Ma, Thailand, measured into the “unhealthy” range at an AQI of 153.

Until better alternatives are made available for farmers in the region, poor air quality will continue to be a seasonal hazard.

Inhaling PM2.5 – particulate matter measuring less than 2.5 microns in diameter per cubic meter – has been linked to multiple health risks, including heart and lung disease, heart attacks, and premature death. Ultrafine particles are even tinier; smaller than 0.1 micron and can be as small as 0.003 microns. The miniscule pollutants enter the bloodstream from the lungs. Once in the circulatory system, ultrafine particles can endanger every organ in the body.