Air quality in Mae Hong Son

How polluted is the air in Mae Hong Son?

Mae Hong Son is located in the far northern region of Thailand, having the nickname of ‘the city of three mists’, due to it being flanked by the high mountain ranges of the Shan hills. With its northern position, as well as being surrounded by tall mountains, the air quality in Mae Hong Son is unfortunately subject to some high levels of pollution, for the same reasons that many cities and provinces in the northern region in Thailand do.

Along with other ambient pollution sources, a majority of this comes from the slash and burn practices carried out by farmers, causing massive spikes in air pollution during the burning season. This practice, along with other causes of pollution will be discussed in further detail in the following question.

Observing some of the current air quality data in Mae Hong Son, it can be seen that it came in with a US AQI reading of 68 in late May of 2021. This reading placed it into the ‘moderate’ air pollution ratings bracket for the particular day and time in which it was taken, which requires a reading of anywhere between 51 to 100 on the US AQI scale (color coded as yellow on air quality maps and graphs).

US AQI is itself a unit aggregated from the volume of several main pollutants found in the air, both in Mae Hong Son and in cities and states across the globe (due to the universal prevalence of these chemical and particle based pollutants, being present wherever anthropogenic and industrial activity is taking place).

These pollutants are ones such as ozone (O₃), which itself is a secondary pollutant formed when the various oxides of nitrogen (NOx) in the air, along with other gases and chemical pollutants are exposed to a high degree of sunlight, with the solar radiation causing a chemical reaction to take place, thus forming ozone, or smog as it is more well known as when it gathers in large enough amounts, often seen blanketing busy cities such as Bangkok over the various busy roads and streets.

Other pollutants used in the calculation of the US AQI level include nitrogen dioxide (NO₂), sulfur dioxide (SO₂), and the two types of particles, namely PM2.5 and PM10. Out of both of these, PM2.5 is the most dangerous pollutant that one can find in the air, with its ultrafine size of 2.5 microns or less in diameter enabling it to penetrate deep within the lungs of those who inhale it, and from there potentially crossing over into the bloodstream, causing all manner of health issues. Hence, yearly average readings are often calculated in PM2.5, which is measured in micrograms per cubic meter (μg/m³), using the same ratings system as US AQI (good, moderate, unhealthy) albeit with vastly different units required for group classification.

With other US AQI readings present in the months of May 2021 in Mae Hong Son, lows of 15 and 17 came in on certain days, indicating a ‘good’ level of air quality (color coded as green), along with highs of 81, once again sitting in the moderate pollution ratings bracket, although on the higher end. Of note is that whilst all these readings are deemed as acceptable as per the US Environmental Protection Agency (EPA), which states that any US AQI reading between 0 to 150 is within the acceptable range, looking at the readings recorded in other months of the year (particularly the early ones that are in the middle of the burning season), one can see why Mae Hong Son is such a poorly ranked city in terms of its air quality and pollution levels.

Why is the air in Mae Hong Son so polluted?

As touched on briefly, the burning of vast swathes of forested land, along with the burning of crop stubble and other areas that contain organic material, is the biggest cause of air pollution present in Mae Hong Son, as well as nearly all cities present in the northern region of Thailand. This burning season is notorious for causing a myriad of ill health effects, with many locals and expatriates fleeing from their homes during these months to escape the clouds of smoke, haze, smog and hazardous particulate matter.

Besides the burning of farm or forest land (which can also occur in neighboring Myanmar and drift over to cities and provinces in Thailand), other prominent causes of air pollution would be ones such as vehicular emissions and fumes, along with power plants and factories contributing further. Construction sites are also a significant source of hazardous particles such as finely ground silica, along with heavy metals such as lead and mercury.

What are some resulting health issues that come from breathing polluted air in Mae Hong Son?

Health issues that may arise during the highly polluted periods taking place in Mae Hong Son include ones such as severe coughs and inflammation of the lungs, leading to heightened risk of respiratory infections. Chronic obstructive pulmonary disease (COPD) may present itself, with illnesses such as pneumonia, bronchitis, emphysema and asthma falling under the COPD bracket.

More severe conditions can be ones such as increased rates of heart attacks and arrythmias, along with strokes, and even death, with many deaths throughout the whole of Thailand being attributed to air pollution alone.

When is the air pollution level at its worst in Mae Hong Son?

Observing the air quality data as collected over the course of 2020, it can be seen that the months of February through to April had some rather severe readings of PM2.5.

They came in respectively with readings of 87.3 μg/m³, 129.1 μg/m³ and 73 μg/m³, before lowering down to more appreciable levels. This made March the most polluted month of the year by a significant amount, being nearly 13 times over the what the world health organization (WHO) considers as being the safest quality of air, at 10 μg/m³ or less.

When does the air quality show signs of improvement in Mae Hong Son?

Whilst the early months of the year during burning season (which typically runs from December through to April of the following year) came in with their extreme highs of PM2.5, Mae Hong Son thereafter entered into a period of time in which the air quality was extremely good, falling within the WHO's target goal of 10 μg/m³ or less, for an impressive five months in a row.

These months were June through to October, with even September having a ‘good’ rating of air quality at 12 μg/m³. After this the pollution levels rapidly spiked once again due to the aforementioned reasons. Out of all of the months mentioned above, July came in with the cleanest reading at 3.6 μg/m³, indicating a near perfect quality of air and highlighting just how damaging the effects of these fires really are (with Mae Hong Son coming in at 397^th place out of all cities ranked worldwide in 2020).

If these practices were to be ceased altogether, many cities and provinces in northern Thailand would make their way out of being classed as the most highly polluted cities in the world, and instead move to being some of the cleanest, based on their non-burning season readings of air pollution.