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Air pollution

A continuing environmental issue in Chiang Mai is the incidence of air pollution that primarily occurs every year between December and April. In 1996, speaking at the Fourth International Network for Environmental Compliance and Enforcement conference—held in Chiang Mai that year—the Governor Virachai Naewboonien invited guest speaker Dr. Jakapan Wongburanawatt, Dean of the Social Science Faculty of Chiang Mai University, to discuss air pollution efforts in the region. Dr. Wongburanawatt stated that, in 1994, an increasing number of city residents attended hospitals suffering from respiratory problems associated with the city's air pollution.

During the December–April period, air quality in Chiang Mai often remains below recommended standards, with fine-particle dust levels reaching twice the standard limits. It has been said that smoke pollution has made March "the worst month to visit Chiang Mai".

The northern centre of the Meteorological Department has reported that low-pressure areas from China trap forest fire smoke in the mountains along the Thai- Myanmar border. Research conducted between 2005 and 2009 showed that average PM10 rates in Chiang Mai during February and March were considerably above the country's safety level of 120 μg/m³, peaking at 383 μg/m³ on 14 March 2007. PM2.5 rates (fine particles 75% smaller than PM10) reached 183 μg/m³ in Chiang Mai in 2018. According to the World Health Organization (WHO), the acceptable level of PM10 is 50 μg/m³ and PM2.5 is 25 μg/m³.

To address the increasing amount of greenhouse gas emissions from the transport sector in Chiang Mai, the city government has advocated the use of non-motorised transport (NMT). In addition to its potential to reduce greenhouse gas emissions, the NMT initiative addresses other issues such as traffic congestion, air quality, income generation for the poor, and the long-term viability of the tourism industry.