曼谷的空气质量

Is Bangkok a polluted city?

Bangkok, the capital of Thailand, is a very densely populated city, with over ten and half million people estimated to be living there in 2020, with a city size of 1,569 km². In 2019 the average reading of fine particulate matter in the air, or PM2.5, was found to be concentration of 22.8 μg/m³. This puts it at a ‘moderate’ rating according to the US Air Quality Index, which according to the stringent US standards of measurement, is any number between 12.1 to 35.4μg/m³. Observing data taken from 2019, the months of June through to August are the months that have the cleanest levels of pollution, with drastically lowered PM2.5 ratings.

Reasons for the lowered PM2.5 readings may be directly linked to seasonal influence, with the rainy season starting at around July and lasting till October. The rain offers a cleansing to the air quality as it naturally pulls the fine particulate matter and other pollutants such as nitrogen dioxide (NO₂) and sulfur dioxide (SO₂) out of the air.

However, despite the readings classing it at a moderate level, there are times when it crosses rapidly over this line to significantly worse pollution with levels of PM2.5 and other contaminants found lingering in the air. A large number of schools were closed in January of 2019, an unprecedented order at the time because the level of air quality has only something that has recently been made more transparent and available for the average citizen, as well as the government keeping a closer eye on it. The schools were closed in order to protect children from a particularly heavy haze that persisted for several weeks.

During this time, in the month of January during 2019, the levels of PM2.5 rose significantly higher than the rest of the year to a reading of 47.4 μg/m³, putting it in the ‘unhealthy for sensitive groups’ bracket of the US AQI. Whilst this presents significant health risks on certain demographics of people, including the young and elderly, as well as those with respiratory problems such as COPD (chronic obstructive pulmonary disease), Bangkok actually came in at a ranking of 48th most polluted city in the whole of Thailand, out of 68 cities recorded on the database. This may come as a surprise to many people, due to the extremely large number of vehicles on the road, the heavy tourism year in and year out (an industry that has come somewhat to a halt in the year of 2020 due to the outbreak of COVID-19). Many visitors and locals alike who have had to traverse the streets of Bangkok know how intense the pollution and haze can get, with visible smoke lining the air and thick black soot covering many of the city’s roadsides and underpasses.

Despite these discrepancies, Bangkok remains as its own entity, with a low ranking of pollution and PM2.5. Yet it is still capable of becoming rapidly more polluted in a very sudden manner, and as such visitors or residents should keep an eye on the air quality index rating, or the Bangkok air quality map, which shows live updates of the PM2.5 and other pollutant levels across the city. AirVisual’s air pollution app can help to provide live information and updates on such readings.

What causes deterioration of air quality in Bangkok?

There are many things that factor into the pollution levels in the city of Bangkok. The exhaust fumes from automobiles are among one of them, the burning of plants and other organic matter in the farming industry releasing its own fair share of smoke and volatile organic compounds (VOC's) into the air, in addition to the boating industry. Bangkok is tied together by a lengthy series of waterways and canals, that are imperative for the livelihood and travel of the city’s residents, as well as providing for many other industries such as tourism and travel, both touristic and residential commuting. It is estimated that over 300,000 boat trips are taken every single day (estimates taken at the beginning of 2020 before imposed lockdown).

The main issue within this industry is that these boats are powered primarily by diesel engines, which inevitably release large amounts of pollution and PM2.5 into the atmosphere, along with black carbon (BC), a dangerous pollutant formed from the incomplete combustion of various biomass and fossil fuels combined. This can take a heavy toll on the quality of the air, with even post COVID-19 readings pushing themselves dangerously high, a reading on the 10th of November 2020 coming in at 92 on the US AQI.

The deterioration is caused by the choking levels of traffic, both on the roads and on the waterways, the burning of agricultural material which releases large amounts of smoke and PM2.5 into the atmosphere, as well as pollution from factories and the industrial sector.

How can Bangkok’s air pollution be reduced?

For a start, the reduction in vehicle emissions would go a long way to reducing the overall level of pollution in Bangkok’s air and reducing its levels of PM2.5, as well as improving its air quality. Measures are already being taken to reduce the massive number of vehicles on the road at certain given times, but these measures are fairly transient and fail to put a dent into the long term AQI rating.

Many of the boats that populate the waterways release large amounts of pollution and PM2.5 and black carbon, and whilst Thailand and other neighboring Asian countries are on the brink of bringing their motorization rates to that of developed countries, there still remains to be a lack of strict fuel standards in regards to the quality of the fuel that is being used, with subsequent exhaust fumes exceeding what would be considered low-emitting standard.

Further measures to reduce the amount of pollution emitted from the burning of organic materials in the farming sector and other related industries would also go a long way, along with more stringent rules on the fume emissions from factories. As these three things are the main culprits in terms of contributing to the higher pollution levels and poorer air quality ratings, an implementation of stricter rules in the farming, vehicular and factory/industry sectors would be a good step to lowering air pollution emissions.

How does Bangkok’s air quality compare to other cities in Thailand?

According to the 2019 air quality index ratings of Thailand, it is shown that indeed Bangkok is significantly lower down on the list of most polluted cities. To give some examples of cities that have worse air quality or higher levels of pollution, the well-known city of Chiang Mai had an average PM2.5 rating of 32.3 μg/m³ as compared to Bangkok’s rating of 22.8 μg/m³. Chiang Mai saw PM2.5 ratings of 98.7 μg/m³ in March and 74.1 μg/m³ in April, ratings that catapulted it into the ‘unhealthy’ rating of the US AQI, far surpassing any readings taken in Bangkok during that year. By contrast the months of June through to August saw PM2.5 readings that fell into the WHO’s target rating of below 10 μg/m³, something that Bangkok failed to achieve throughout 2019. However, the months of March and April were high enough to give it a higher yearly average than Bangkok, in regards to its air pollution.

This gives one example of a comparison to other cities in Thailand, as can be found within IQAir’s 2019 World Air Quality Report. They follow a fairly thematic pattern of pollution spikes in certain months and drops during the rainy season, with variations of these numbers appearing across the 68 ranked cities.

What are the health impacts of pollution in Bangkok?

Numerous studies have been conducted on the effects of PM2.5 on the human body, and the results of being exposed to it over long periods of time. The other particulate matter of a larger size, of a width of 10 or less micrometers across (PM10), whilst larger than the more lethal PM2.5, are still small enough to enter via the respiratory tract and end up in the lungs, causing potential issues to both the lungs and the heart. PM2.5 on the other hand, being of a much smaller size (particles with a diameter of 2.5 micrometers or less) has the ability to not only get into the body via the respiratory tract, but can enter the bloodstream whereby they gain the ability to circulate to the rest of the body, causing much more adverse health impacts.

On a short-term basis, these health effects may include irritation to the eyes and nose, as well as the throat or other mucous membranes. PM10 can worsen cases of asthma, triggering attacks leading to other numerous forms of COPD. People with preexisting heart problems or diseases may find their condition worsening, with heart attacks or arrythmias (irregular heart beat) also possible.

Longer term exposure can lead to even more reduced lung function, or a worsening of COPD symptoms, as well as reduced life expectancy from the development of diseases affecting both the respiratory system and heart. PM2.5 cannot be easily removed from the body, if at all, making the need for the reduction of pollution and air filtration systems ever more important.

Commuting down the roads or waterways of Bangkok on a daily basis could have highly negative effects on a person’s health and a significant reduction in life expectancy, and as such mask use is recommended, as well as being aware of the pollution forecast and the daily levels of PM2.5 in the air.