DHAKA’S POLLUTION PROBLEM
Dhaka, the capital city of Bangladesh not only holds the title for being the largest city in the country, but for also being the 9th largest city worldwide. The growing city also ranks 6th among the most populated cities in the world with 9 million people existing within the city’s periphery. Coupled with these reasons, as well as Dhaka’s position as the economic center of the whole country, the city is subjected to exacerbating levels of pollution annually. Despite brief periods of respite where levels drop, the pollution readings still remain relatively high, making its air caustic to breathe all year-round.
Dhaka recorded PM2.5 readings of 83.3 μg/m³ as the yearly average in 2019, catapulting it in the “unhealthy” bracket of air quality where PM2.5 levels between 55.5 to 150.4 μg/m³ are classified as unhealthy. Apart from this just being a classification, this reading is evident that the air quality of Dhaka is indeed unhealthy to breathe. In January, the numbers went well above the yearly average recording a national high of 181.8 μg/m³, putting it into the ‘very unhealthy’ bracket (150.5 to 250.4 μg/m³).
Particulate matter with diameter less than 2.5 micrometer usually known as PM2.5 particulate matter, called “fine” particulate, is primarily a result of combustion products emitted into the atmosphere as well as those particles that are formed in the atmosphere from gaseous pollutants as a result atmospheric chemistry (secondary formation). Generally, the fine particulate poses a greater health risk because these particles can deposit deep in the lung and contain chemicals that are particularly harmful to health.
CAUSES OF POLLUTIONIN DHAKA
Due to Dhaka being highly populated, the city faces pollution problems from all sides. It is subjected to air contamination because of the extensive use of cars, motorbikes and trucks, most of which are out of the purview of regulation in terms of age or quality of their engines, or the fuels they run on. These vehicles operate on fossil fuels such as diesel, as a result emitting far more pollution then a regular car would releasing high levels of contaminants in the air.
Contributing to the ever-growing pollution levels are the industries that operate within and in the margins of the city. Brick kilns are primarily responsible for excessively elevated levels of pollution. Alongside factories and production sites contribute to rising pollution. Dhaka’s brick kilns have seen a subsequent increase in demand owing to an economic boom, and are known to produce billions of bricks each year. These kilns rely on unregulated fuel sources like burning of coal, wood and other combustible materials for their power. These fuel sources release excessive amounts of noxious fumes and smoke into the atmosphere.
Apart from these two glaring issues, dust concentrations building up in the city also work to trap pollutants which causes contaminants to remain in the atmosphere longer. Burning sites where refuse containing organic matter as well as toxic materials such as plastics and rubber are set alight in the streets contribute to pollution.
THE MAIN CULPRIT ARE CONTAMINANTS
Most of the pollution is caused by vehicles. Industries and construction sites. These subject Dhaka to extremely dangerous pollutants being released into its atmosphere. Materials such as black carbon and volatile organic compounds are all released in copious amounts from the use of fossil fuels such as diesel in coal, present in vehicles and factories alike, as well as arising from the aforementioned open burn sources (with the incomplete combustion of materials such as wood often leading to large amounts of black carbon being produced, often in the form of soot).
Chemical compounds such as nitrogen dioxide (NO2) and sulfur dioxide (SO2) are also abundant in the atmosphere, once again finding their creation from both cars and factories alike. The brick kilns produce vast amounts of their own smoke and haze, containing other compounds such as carbon monoxide (CO) and ozone (O3). The large amounts of dust given off by poorly maintained construction sites would contain a variety of PM2.5 and PM10, such as silica dust, or finely ground soil or gravel particles, all of which can cause a number of long-term health effects when breathed in.
PEAK POLLUTION SEASON
Pollution levels start to show a considerable rise in the month of October, which coincides with the end of the monsoon season. Due to the lack of monsoon showers which are helpful to clean the city air, dust particles remain in the atmosphere uncleansed.
September saw a PM2.5 reading of 37.7 μg/m³ in 2019. This jumped up significantly in October to 64.6 μg/m³, an increase of nearly twofold. These numbers continued to rise until they hit their absolute peak in January, with a reading of 181.8 μg/m³ being present.
With air pollution levels this bad, preventative measures become vital for Dhaka’s citizens, with the avoidance of outdoor activities as well as the wearing of fine particle filtering masks being highly necessary. After the peak in January, pollution levels still remained extremely high but showed a steady drop, with a reading of 145.7 μg/m³ in February, followed by 107.4 μg/m³ in March. These numbers continued to drop until reaching the cleanest months of the year, June through to September, with August coming in with the cleanest reading of the year at 31.3 μg/m³.
THINKING OF A CLEANER DHAKA
In order to reduce such elevated levels of pollution, many steps need to be taken, albeit in the face of such economic growth it would be a task that the city of Dhaka will be hard pressed to do. The introduction of stricter regulations regarding fuels and vehicles allowed on the road will be helpful in the fight against reducing ambient pollution levels in the air, with the removal of diesel fuel as well as ancient fume producing engines.
Other steps would be to introduce stricter measures to both factories and construction sites, holding individual organizations accountable for the amount of pollution that they produce, with the possibility of adding fines to those that exceed unsafe levels of pollution, as well as particulate matter. Whilst certainly a compounded issue, the introduction of these initiatives would be a step in the right direction for Dhaka to obtain a cleaner level of air quality, and improve its US AQI readings as well as PM2.5 levels.