Dhaka has been in the bottom of air-quality indexes in the recent times. Being exposed to the Dhaka air for substantially longer time poses serious threats to health. There are six pollutants considered as the Criteria Air Pollutant for their abundances as pollutants in the atmosphere and their ability to harm human health and other life forms and Dhaka air is brimming with them, writes Sakib Rahman Siddique Shuvo
WHAT can we feel if we close our eyes and think about the smell of Dhaka? Imagine it is possible to store the scent of things as we read in the 1985 masterpiece novel by Patrick Süskind, Perfume, can we store the aroma of the street flowers from any road in Dhaka? Can we save the odour of the surroundings while someone passes by Indira Road or Elephant Road?
The 21st most polluted city of the world, Dhaka, which is second amongst the capitals, emerged as the country with the worst particulate matter (PM2.5) pollution, most dangerous type of airborne pollution, roughly 1/30 the width of a human hair. According to the US Consulate’s real-time Air Quality Index (AQI), it was 263 when I was writing this piece, which is considered as ‘very unhealthy’ air quality on the scale. The dust particles of the road, cars, constructions, brick klins and mismanaged wastes have made a mess around the city causing this amount of air pollution.
There are six pollutants considered as the Criteria Air Pollutant (CAP) for their abundances as pollutants in the atmosphere and ability to harm human health and other life forms. Sulfur dioxide, a colourless gas with a pungent odour, generated from fossil fuel combustions at power plants and other industrial facilities, affects children, elders and asthma patients. In essence, respiratory paralysis and pulmonary oedema with a risk of death can be produced by exposure to high concentrations of SO2 for several minutes.
Nitrogen Oxides are released from motor vehicle exhaust or burning coal and other fuels. High levels of NO and N2O exposure can cause collapse, rapid burning and swelling of tissues in the throat and upper respiratory tract, difficult breathing, throat spasms and fluid build-up in the lungs.
Ozone comes third on the list. Infamous greenhouse gas, Ozone is not directly emitted into the air; it is formed by the interaction of sunlight, mostly ultraviolet light, with hydrocarbons and nitrogen oxides, which are released by automobile tailpipes and smokestacks.
Talking about hydrocarbons, Carbon Monoxide and Carbon Dioxides are the most eminent culprits, which are also greenhouse gases. Carbon Monoxide is another CAP, a colourless, odourless, tasteless gas which is flammable and quite toxic to humans and other oxygen-breathing organisms. CO is a byproduct of fossil fuel combustion, biomass burning and the oxidation of volatile hydrocarbons.
Particulate Matters or PM is the fifth CAP, the mixture of solid particles or liquid droplets suspended in the air includes both organic and inorganic particles – dust, pollen, soot, smoke, and liquid droplets. Particle fractions which are smaller than 2.5 micrometres are considered as fine particles, the most harmful component in the air for human health.
Chemically enriched fine particles can penetrate deep into the respiratory system and inflict significant damage to the system. Recently the relationship between fine particles with fatal diseases like cancers, heart attack et cetera has been revealed by studies.
A recent report published by the Department of Environment, MoEFCC, revealed the scenario of air pollution in Dhaka. According to AQI categorisation, the concentration of PM2.5 and PM10 is poor, which causes breathing discomfort to all. The rate of PM2.5 and PM10 varies seasonally. During November to April, the concentration remains high and January is the most polluted month of the year followed by December and February.
In the dry season, the daytime variation of the concentration is very steep. It gets higher from 7:00 am to 9:00 am for the fumigation effect and office-bound traffic, since the level goes sheer downward up to 5:00 pm. The concentration again rose to the pick at 8:00 pm to 9:00 pm, since then it continues diving up to the morning the next day. With relatively lower concentration rate diurnal concentration during the wet season is not steep; instead, it follows a wave pattern with little deviations from 9:00 am to 5:00 pm.
Not only the traffics are the leading cause of this high concentration rate in the dry season but also the northwestern winds, which carries most of the PM to the city. In the dry season, a large number of brick kilns operate from that direction. The vast amount of brick kilns and industries at the northwestern side of the city are also working as a driver of air pollution. The study also showed that the initiatives are taken by the government to set up fixed kiln chimney in those brickfields caused a considerable drop in PM concentrations of Dhaka.
Living for one year in an area with high levels of fine particulate matter (PM2.5) is as bad for human health as smoking 150 cigarettes a year, according to the British Heart Foundation. They scaled the number up to figure out how much daily exposure to PM2.5 is equal to smoking one cigarette, which they believe, is around 28.88μg/m3. In Dhaka the mean amount of PM2.5 is 80.5 μg/m3 in 2017.
That means the smokers around the city are smoking extra 2.78 cigarettes daily, which is free. Another study shows that burning one mosquito coil would release the same amount of PM2.5 mass as burning 75-137 cigarettes. So living in Dhaka for one month can cost you one-mosquito-coil equivalent pollution.
Are the 20-million people living in the city aware of this? Can they feel the air is killing them day by day, making them vulnerable to cancer and other respiratory problems? What is the way to break free from this problem? Will these people going to stop using private transports and start using public transportation system? Will they stop polluting the environment and begin to use a proper waste management system? The answer is in the policy making level.
That was a sunny afternoon at Dhaka, and I was travelling by a rickshaw. It was Pilkhana road, a two-lane street connecting Hazaribag with Azimpur, ten feet boundary of BGB headquarters on the one side, and various shops and houses on the other side. This road is always jam-packed because of the curve and of course traffic mismanagement.
It takes almost 30 minutes to reach Nilkhet from BGB Gate number 1. I was sitting on a rickshaw and thinking about my first instalment of this article series and decided to write about the Aminbazar landfill site. The rickshaw was standing near a mini waste station, where the wastage from the households and waiting for a truck to pick up the waste and through them to the Secondary Transfer Station.
Alongside the waste dumping place, there is a residential building of the Border Guards of Bangladesh. I noticed a senior lady, offering her prayers, the windows were open. She was on the third floor of the building. But I can bet the bitter smell of the dumping zone was easily noticeable from even more elevation than the third floor of a building. Has she got used to it? Or had her olfactory nerve is not properly working and she cannot sense the smell, I wonder.
Sakib Rahman Siddique Shuvo is a freelance geographer and a student of Jahangirnagar University.
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