Chiang Mai Air pollution

A continuing environmental problem facing Chiang Mai is the incidence of air pollution which primarily occurs for a period of several weeks up to the beginning of April. This issue has been acknowledged for some time.

Back in 1996, speaking at the Fourth International Network for Environmental Compliance and Enforcement conference, which was held in Chiang Mai in that year, the then governor of Chiang Mai, Virachai Naewboonien invited guest speaker Dr. Jakapan Wongburanawatt, the Dean of the Social Science Faculty of Chiang Mai University at that time, to discuss the state of Chiang Mai air pollution efforts. Dr. Wongburanawatt stated that back in 1994, there were already increasing numbers of city residents coming to hospitals suffering from respiratory problems associated with city air pollution.

The Thailand Pollution Control Department of the Ministry of Natural Resources and Environment is actively engaged in finding solutions with public awareness campaigns and other initiatives. During this period, unlike the majority of the year, air quality in Chiang Mai often remains below recommended standards with fine-particle dust levels reaching twice the standard. 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. Chiang Mai’s air quality has been perceptibly deteriorating over the past ten years. This is being addressed by a number of initiatives, and in part, is often seen in cities with increasing economic growth at the expense of a strong corresponding programme to counteract the negative effects of environmental impact.


The city is often shrouded in smog during this period leading up to the rainy season. Fine particulate dust levels have sometimes been tested between 190 micrograms and 243 micrograms per cubic meter. (The standard acceptable level is 120 milligrams per cubic meter.) Amongst the minor sources of particulate matter pollution in Chiang Mai is the prevalence of burning in the city, with cremations, burning garbage, or vehicular emissions from poorly maintaineddiesel vehicles contributing. Added to these minor causes is dust raised during building and excavations.

A forest fire in the mountains west of Chiang Mai
in Mae Hong Son Province

Main cause
A forest fire in the mountains west of Chiang Mai in Mae Hong Son Province

The majority cause of air pollution however as proven by recorded satellite imagery, is the age-old practice of burning-off undergrowth in forests in the mountainous regions, especially along the Thai-Myanmar border.
Chiang Mai’s problems are exacerbated by the fact that the city, like other areas such as Los Angeles and Salt Lake City, is located in a natural geographic bowl surrounded by mountains.


The result is a slowing of air movement, picking up more particulates as they are released by cars and burning trash. Also as a result of this inversion effect, as air rises in the bowl, it effectively turns over and settles back down over the city until a welcome wind shift or rainstorm cleans the air. The Thailand Pollution Control Department of the Ministry of Natural Resources and Environment is actively engaged in finding solutions to this hazardous problem and has been for several years as Chiang Mai's air quality index numbers are ever decreasing. Exacerbating this problem, one the most popular modes of convenient low-cost public transportation in Chiang Mai—as in the rest of Thailand—is provided by differently coloured pick-up trucks called 'Songtheouw'. Red Songtheouws (Red Cars or Rod Daeng) provide passenger requested journeys whilst other colours operate on fixed routes. People ride in the back of these trucks which are equipped with diesel engines.


The exhaust systems on all of these trucks are bored out in order to increase horse power which then increases the amount of carbon emissions and heavy metals which get ejected out of the back of the vehicles. As a result, the streets of Chiang Mai are increasingly difficult to ride on when using a motorcycle. It is a very common sight to see motorcyclists protecting their breathing passages as they follow these trucks. The same can be said from the famous Tuk tuks which are ubiquitous in Thailand. The city authorities are well aware of this issue and have enacted a campaign to replace all of the older, poorly tuned offending vehicles with modern yellow and blue metered passenger taxis. As these older, air quality offenders are slowly retired, it remains to be seen if the regulating bodies will be able to effect change in Chiang Mai in the face of resistance the drivers of these vehicles who have traditionally made their living in this way for many years. It should be said that Chiang Mai is not the only Thai city with this problem as Songtheow and Tuk Tuk is the major mode of low cost transportation in Thailand.


Unfortunately, because of Chiang Mai's inversion effect as the result of it being situated in a geographic bowl, the carbon emissions emitted from vehicles is made an even more troubling problem.



For several years, as Chiang Mai's air quality index has become more and more troublesome, in relation to the rest of the region, the recognition of the problem has been growing locally. Doctors in Chiang Mai have been noticing an increase in people coming to see them with upper respiratory difficulties. Chiang Mai has now enacted stringent regulation of emissions standards for all vehicles. Since 2008, police sometimes set up roadblocks to test exhaust emissions on the spot and officers will enact the law to ban offending vehicles as Chiang Mai continues to work actively towards a cleaner environment.