Qualité de l’air à Hang Dong

How bad is the pollution level in Hang Dong?

Hang Dong is a city located in the northern region of Thailand, within Chiang Mai. It is a city that sees some fairly bad levels of air quality for a number of reasons, some of which being discussed in the following question. In May of 2021, Hang Dong came in with a US AQI reading of 75, indicating a ‘moderate’ level of air pollution for the time in which the reading was taken. Other readings on record include the yearly PM2.5 average that was taken over the course of 2020.

Hang Dong’s yearly PM2.5 reading for 2020 was 36.8 μg/m³, placing it in the ‘unhealthy for sensitive groups’ bracket, which requires a PM2.5 reading of anywhere between 35.5 to 55.4 μg/m³. This reading placed it in 6^th place out of all cities ranked in Thailand for that year, as well as 253^rd place out of all cities ranked worldwide.

Why are there bad levels of air pollution in Hang Dong?

The main causes of badly polluted air in Hang Dong include sources such as vehicular exhaust and fumes, along with the variety of oil vapors and fine particulate matter that older and more defunct models can give out (more common in cities around Thailand due to lack of strict regulations regarding vehicle condition). Others include factory emissions, particles from construction sites and road works, along with the most prominent and devastating cause of pollution in northern Thailand, that of fires started mainly by farmers for the purposes of clearing vast areas of both forest and farmland.

These fires can also drift over from Myanmar, and together with the local ones surrounding Hang Dong, cause the US AQI and PM2.5 count to rise significantly. This is one of the more prominent causes and as such the cessation of it in years to come will be of the utmost importance, for both the citizens of Hang Dong as well as the entire surrounding region.

When does Hang Dong see the highest level of polluted air?

Observing the levels of air pollution data collected in 2020, it is clear that Hang Dong had several months that came in with some severe levels of air pollution, with the PM2.5 count being far in excess of the rest of the year. The PM2.5 count can be seen to rise at the end of the year, indicating the pollution levels would start their ascent and then hit their peak in the early months of the following year, a pattern that is seen over and over in many cities in Chiang Mai.

January through to April had the highest levels of air pollution present, coming in with respective readings of 56.5 μg/m³, 70.9 μg/m³, 108 μg/m³ and 76.6 μg/m³. All of these readings fell within the ‘unhealthy’ ratings bracket, which requires a sizeable PM2.5 reading of 55.5 to 150.4 μg/m³ to be classified as such. March was by far the most polluted month of the year with its reading of 108 μg/m³, putting it many magnitudes higher than the cleanest month of the year.

When does Hang Dong see its cleanest period of air?

Once again looking at the PM2.5 levels collected over the course of 2020, it can be seen that after the spikes in pollution came to a close, Hang Dong entered into a period of time in which the air quality levels dropped considerably, indicating that if its forest and farmland fire issues were to be permanently stopped, or at least massively reduced, both Hang Dong and the entirety of the northern region of Thailand would see huge improvements in its pollution levels.

May through to October had the best levels of PM2.5 on record, coming in with readings of 23.9 μg/m³, 7.1 μg/m³, 7.4 μg/m³, 10.7 μg/m³, 10.9 μg/m³ and 13.8 μg/m³ respectively, after which they started to rise again rapidly.

These numbers showed that June and July had the cleanest levels of air quality, falling into the world health organization's (WHO's) target goal for the best quality of air at 10 μg/m³ or less. August and September also hit ‘good’ levels of air quality, which requires a very fine bracket of entry at 10 to 12 μg/m³ to be classified as such.

What are some of the main pollutants found within Hang Dong?

As mentioned previously as to the main causes of pollution, they typically revolve around various combustion sources present within Hang Dong as well as surrounding towns, villages and rural areas. These combustion sources usually give out a number of main pollutants, many of which go into the calculation of the overall level of US AQI, which itself is a composite number based off of the calculation of these main pollutants.

These main ones are nitrogen dioxide (NO₂), sulfur dioxide (SO₂), ozone (O₃), as well as the two varieties of particulate matter, that is, ultrafine ones (PM2.5) and larger or coarse particles (PM10). Ozone can be formed from the various oxides of nitrogen (NOx) being exposed to the sun’s rays, and can form vast clouds of smog (as it is better known as) during times of intense sunlight.

Other pollutants such as a variety of gases or other chemical compounds may also undergo this chemical reaction and create ozone. Whilst it is an essential part of the upper atmosphere, namely the ozone layer, when it accumulates on the ground level it can cause all manner of health issues to occur, ranging from shortness of breath and headaches, to nausea and irritation or inflammation of the mucous membranes and lung tissue.

Other pollutants found would be ones such as black carbon and volatile organic compounds (VOCs), with black carbon being the main component of soot, belong to the PM2.5 collective, as well as having many dangerous properties to both human health as well as the environment. It is a known carcinogen (along with other fine particles such as silica dust), and has the ability to warm the air around it causing a heating and thus climate changing effect, due to its ability to absorb solar radiation and convert it directly to heat. It can be found in large quantities usually coated on the sides of roads that have a high level of traffic, as well as highways and other areas that produce soot, with even fireplaces and traditional kitchens seeing thick layers of it.

Some examples of these mentioned VOCs include chemicals such as benzene, toluene, xylene, methylene chloride, styrene and benzene. They can also be found emanating from household products (mostly scented items such as candles, certain bathroom products, as well as items containing glue or layers of varnish), making them one of the main sources of indoor pollution. They are able to maintain their gaseous state (hence their ‘volatile’ nature) even during colder spells which are common in northern Thailand, and hence they are easy to breathe, making them even more harmful due to their ease of inhalation.