Urbanization increases the health hazards associated with air pollution by causing emissions and urban expansion, which in turn influences air pollution. However, the health risks related to urbanization are rarely estimated, especially for cities with complex areas.
Air pollutants are substances that damage humans, plants and animals drastically when present in the atmosphere at sufficient concentrations. The most common air pollutants are ozone (O3), fine particulate matter (PM2.5, particulate matter with an aerodynamic diameter of 2.5?µm or less), sulfur dioxide (SO2) and nitrogen oxides (NOx, which is comprised of NO and NO2). These air pollutants threaten human health in many parts of the world, evoking a series of health risks including cardiovascular diseases, respiratory diseases and chronic obstructive pulmonary disease. According to the World Health Organization (WHO), exposure to ambient air pollutants is associated with 4.2 million premature deaths worldwide annually.
Most of those premature deaths occur in urban areas, as urban areas currently host more than 50?% of the population (over 3.5 billion people). This proportion is projected to increase to 70?% by 2050 due to ongoing urbanization.
Since Bangladesh gained independence in 1971, its capital has exploded into one of the most densely populated cities on Earth. Dhakas traffic congestion is monumental - average driving speeds have plummeted to 4.5 kilometers per hour, around walking speed. But thats only one of several factors that darken the skies over a massive metro area of more than 20 million people. Residents of a low-lying city who
e already extremely vulnerable to the effects of climate change suffer physical and mental health impact from the toxic atmospheric stew generated by coal-fired brick kilns, dust from roads and construction sites, industrial pollution, and smog blown in from neighboring nations[10].
In a recent study, researcher found that construction is the highest contributor to Dhakas pollution - 30% of the total - as the city sprawled from about 50 square kilometers in 1990 to 300 square kilometers today. A near second, at 29%, is industrial pollution from the 1,000 brick kilns and other factories across the city. Vehicles emissions add a further 15%; "transboundary pollution" from neighboring India, Pakistan and Nepal make up 10%. Activities such as burning waste and wood-fired stoves represent the remainder.
"Whats so troubling is how complex and wide-ranging the sources of Dhakas air pollution are," says investigator. "Still, we are a long way from even starting to solve the problem."
The toxic air is having a deadly impact.Bangladesh is the country with the worst air pollution in the world every year since 2018, according to a report by the Energy Policy Institute at the University of Chicago, which estimates that air pollution costs the average citizen in Dhaka eight years of their life. Research published last April in Science Advances estimated 24,000 people in Dhaka died prematurely due to air pollution between 2005 and 2018, the highest among the 46 cities studied.
In a first study of its kind, analyzing 12,000 Bangladeshis, the World Bank last year found that a 1% increase in exposure to PM2.5 above WHO guidelines led to a 12.8% rise in the probability of a person having breathing difficulties and a 20% rise in the probability of depression. It also found those with higher incomes - one point higher on a socioeconomic indicator known as an asset score - had a 45% lower exposure.
PM2.5 particles - small enough to bore through lungs, enter the bloodstream and damage internal organs - are linked to cardiovascular and respiratory diseases and cancer. Along with this health cost, air pollution has a significant financial impact. According to a World Bank research, losses from air pollution in 2019 ranged from $11.5 billion to $13 billion, or 3.9% to 4.4% of Bangladeshs GDP.
"We have a public health emergency on our hands," saysa professor atDhakaUniversity specializing in air pollution. "But it is being overlooked since it is not something that the general people can see or recognize with ease."
Dhaka ranked fifth on the list of cities worldwide with the worst air quality on Monday, November20, 2023. The air in Dhaka city was classified as "unhealthy" with an AQI score of 164 at 9:55am and PM2.5 concentration in Dhaka was 16 times the WHO annual air quality guideline value.
In order to reduce such elevated levels of pollution, many steps would need to be taken, albeit in the face of such economic growth it would be a task that the city of Dhaka would be hard pressed to do. Stricter restrictions on fuels and vehicles allowed on the road would be beneficial in the fight to reduce ambient pollution levels in the air, with the removal of diesel fuel and old fume-producing engines being especially beneficial.
Other initiatives involve stricter regulations for factories and building sites, holding organizations responsible for the quantity of pollution they produce, and potentially fining those who exceed harmful pollution and particulate matter thresholds. Although there are undoubtedly complex factors involved, implementing these initiatives would be a positive step towards improving Dhakas air quality and raising its PM2.5 and US AQI readings.
The writers Dr. Md. Shamim Hayder Talukder is Chief Executive Officer and Md Wahiduzzaman is Urban Health Officer of the Eminence Associates for Social Development
