Qualité de l’air à Narayanganj

Is Narayanganj a very polluted city?

Narayanganj is a city in central Bangladesh, situated in a province of the same name around 16 kilometres south east of Dhaka which is the capital city. According to a census conducted in 2012, Narayanganj had an estimated population of approximately 1.5 million people which ranked it as the sixth largest city in Bangladesh. It is known as a centre for the jute trade.

Towards the end of the third quarter in 2021, Narayanganj was experiencing a period of “Moderate” quality air with a US AQI reading of 74. This United States Air Quality Index figure is worked out by taking note of the recorded levels of six of the most prolific air pollutants. These may include, both diameters of PM (PM10, PM2.5), nitrogen dioxide, sulphur dioxide, ozone and carbon monoxide. If figures are not available for all six, a level can still be calculated by using what information there is. It can then be used as a metric when comparing one city with another, anywhere in the world. In the case of Narayanganj, the only record was for that of PM2.5 which was 23.1 µg/m³. This level of PM2.5 can be seen to be almost two and a half times higher than the target figure of 10 µg/m³, as recommended by the World Health Organisation (WHO). This is considered to be an acceptable level although no amount of air pollution can be considered as being safe.

This is not an extremely high level of air pollution, but care still must be taken. The advice would be to remain indoors and close all doors and windows to stop more dirty air from getting inside. Those of a sensitive disposition should avoid venturing outside until the air quality improves and even then, a mask should be worn at all times. There is an app available from AirVisual which can be downloaded to any mobile device which gives up-to-the-minute details about air quality. This should help with that decision.

Is the level of air pollution the same throughout the year in Narayanganj?

Looking back at the figures for 2020, published by IQAir.com, it can be seen that Narayanganj achieved the WHO target figure of less than 10 µg/m³ from May until the end of November. The best month being July with a very low reading of just 1.6 µg/m³. The month of April returned “Good” quality air with a figure of 10.6 µg/m³.

March and December saw figures between 12.2 and 35.4 µg/m³ which placed them in the “Moderate” category. However, the months of January and February saw figures plummet into the “Unhealthy” category with figures of 94.8 and 60.2 µg/m³.

There were no records regarding air pollution before 2020 when the recorded annual average was 21.8 µg/m³. This figure may be lower than expected because of the ongoing COVID-19 situation. Many vehicles were taken off the road as their drivers were no longer required to drive to the office each day. There were also several small factories and processing units that were closed temporarily so their emissions were no longer part of the local atmosphere.

What is the cause of air pollution in Narayanganj?

The level of pollution has gone so high that the World Health Organisation has placed it among the 25 cities with the most polluted air in the world. Industrial smog, emissions from vehicles and brick kilns, and dust from construction sites are the main source of pollution in the city. The level of pollution is particularly high during the winter. As the amount of rainfall reduces in the winter, the pollution level in the air goes up.

Among 1,600 cities of the world, Narayanganj was identified as the 17^th city with the worst air quality.

The local authority has found a very high level of gaseous pollutants in the air such as carbon monoxide (CO), sulphur dioxide (SO₂), nitrogen oxide (NOx) and ozone (O₃) and methane (CH₄). They also discovered the damaging PM particles which are carrying sulphates, nitrates, ammonia, sodium chloride, black carbon and mineral dust. These are particularly dangerous as they can often penetrate deep into the lungs and even pass into the bloodstream.

Local environmentalists say brick kilns, construction work, road dust, car smoke, etc. are major causes of air pollution. In Narayanganj, fly ash from the cement factory has been added to all this. When you breathe in, it seems that fly ash is entering your nose.

What can be done to improve air quality in Narayanganj?

New guidelines from the WHO have reduced the acceptable levels of 3 main air pollutants. These elements are Particulate Matter (PM2.5, PM10 and nitrogen dioxide (NO₂).

PM or particulate matter is a mixture of solid and liquid matter floating in the air, which cannot be seen with the naked eye without a microscope. These can easily enter our body through inhalation and adversely affect our health. PM can be made by combining different types of chemical elements. The diameter of PM2.5 is less than 2.5 microns and the diameter of PM10 is about 10 microns.

What are the detrimental effects of breathing in polluted air?

Air pollution increases the risk of heart disease, stroke, chronic obstructive pulmonary disease (COPD), lung cancer and other diseases including acute lower respiratory infections in children.

Toxic gases and fine dust in the air affect human respiratory function. When carbon monoxide gas is absorbed by our lungs, it reacts with the haemoglobin in our blood to form carboxyl haemoglobin, resulting in a decrease in the amount of haemoglobin needed to carry oxygen in the human blood. So, people who suffer from oxygen deprivation are more likely to be affected by it.

Sulphur dioxide is one of the most serious and widespread air pollutants. As the amount of sulphur dioxide decreases, the smooth muscles of the human bronchioles relax, and as the amount or concentration increases, mucus production increases. Respiratory protection cilia are also affected by this gas.

Another air pollutant, ozone, is a type of irritating gas that enters the lungs more quickly than sulphur dioxide. The presence of very small amounts of ozone can cause respiratory problems, even heart problems, and even bleeding.

One of the most common air pollutants in the air is hydrocarbons, which cause lung cancer.

Lead from car fumes is a dangerous toxin, especially in children, because it damages children's brains.

In addition, air pollution causes chronic problems such as lung cancer, bronchitis, asthma and shortness of breath.