URBAN air pollution is a complex mix of toxic pollutants and key contaminants like nitrogen oxides (NOx), sulphur oxides (SOx), ozone (O3), and particulate matter (PM). Particulate matter is classified primarily by size due to the varying health effects associated with particles of different diameters. It refers to a mixture of solid particles and liquid droplets suspended in the air, including aerosols, smoke, fumes, dust and ash. The composition of particulate matter can change depending on location, season, and weather conditions.
Fine particulate matter, known as PM2.5, consists of particles with diameters of 2.5 microns or smaller. 2.5 micrometres is tiny — about 30 times smaller than the diameter of an average human hair, which is around 70 micrometers. These tiny particles are also called respirable particles because they can penetrate deeper into the respiratory system compared to larger particles. In Dhaka, PM2.5 mainly consists of sulphate and nitrate particles (called secondary pollutants formed by the chemical reaction of SO2 and NO2 in the atmosphere), elemental and organic carbon, and soil. SO2 and NO2 are the primary pollutants emitted due to the internal combustion of mainly coal, diesel and natural gas, and they are the primary contributors of transboundary pollution, especially from India.
PM2.5 or smaller pose the greatest health risk, linked to hospital admissions, serious conditions, and premature death. Those most vulnerable include people with asthma, cardiovascular or lung disease, children, and the elderly. Health effects from PM2.5 exposure can occur over both short (daily) and long-term (yearly) periods. This article will only cover the current exposures of PM2.5 in Dhaka, major contributing sources, historical investment in air quality management and how they failed to improve the quality of air, and what can be done in the short and long term to resolve the crisis.
Current exposures to PM2.5
BANGLADESH standards for PM2.5 are 65 microgram per cubic meter (ug/m3) for 24 hours and 15 ug/m3 for annual averaging times. On the other hand, corresponding guideline values from the World Health Organisation are 5 ug/m3 and 15 ug/m3, respectively. A quick overview of the air quality index and concentration for PM2.5 indicates that Dhaka’s population was exposed to unhealthy air (55.5–125.4 ug/m3) for 1,445 days (46 per cent) from 2016 to 2024. During the same period, exposures to very unhealthy air (125.5-225.4 ug/m3) were 687 days (22 per cent). This is extremely alarming and has been reflected in the health of the population at large. In 2024 alone, Dhaka’s population has been breathing toxic air for 127 days, more than 50 per cent of the time.
Major sources of PM2.5
A COMPREHENSIVE source apportionment (a technique to identify and quantify the contributions of different pollution sources) on Dhaka’s air quality was never done. Some independent studies were conducted; however, they could not exclusively conclude the actual source contributions. A GAINS model developed by the International Institute for Applied Systems Analysis (2018) predicted the various source allocations of population exposures. The study concluded that about 10 ug/m3 from the same city (local contributions from automobiles, brick kilns, indoor air pollution, etc.), 26 ug/m3 from the same division, 36 ug/m3 from other divisions, 24 ug/m3 from other countries (transboundary pollution, mainly from India), and 4 ug/m3 from natural soil dust, respectively, are the source allocations of population exposure to PM2.5. Dhaka is the main victim of transboundary pollution (24 ug/m3), compared to Kathmandu (8 ug/m3), Rawalpindi (4 ug/m3), and Delhi (1 ug/m3) in South Asia. Due to the geolocation of Bangladesh, a downwind country, wind blows mainly from the north-west of India during October to March. India generates 205.2 GW of power from 180 coal-fired powerplants, emitting particles SO2 and NO2, which are the main transboundary contributors of PM2.5 in Bangladesh. Recent air quality monitoring in remote locations of Bangladesh also confirmed the significantly high background concentrations of PM2.5: 14 ug/m3 in Pekua, Cox’s Bazar and 15.8 ug/m3 in Hiron Point, Sundarbans. Most striking observations reported during the strictest lockdown of the Covid pandemic period during July 23 to August 5, 2021, where daily average concentration of PM2.5 were reported between 3.78 and 32.72 ug/m3, with an average of 13.23 ug/m3 during a season when wind is blowing from a southeast direction. Therefore, any strategy Bangladesh takes for air pollution control must include regional players, especially India under a shared airshed.
The World Bank conducted a study in 2022 titled ‘Breathing Heavy’ and made the following major conclusions based on air quality monitoring data between 2013 and 2021:
— Air pollution levels across the country vary significantly, with the western regions, such as Khulna and Rajshahi, experiencing higher pollution levels compared to the eastern regions like Sylhet and Chattogram. This disparity is largely due to the degraded airshed in neighbouring eastern Indian states, including Bihar, West Bengal and Jharkhand.
— Urban areas in Bangladesh experience the highest pollution concentrations in locations with ongoing major construction and heavy traffic, followed closely by areas with a high density of brick kilns.
Investment in air quality improvements
‘A STATE of Global Air Quality Funding’ conducted by Climate Policy Initiative in 2023 found that, for every $1,000 spent by a development funder, just $7 (0.7 per cent) was spent on tackling outdoor air pollution. Most outdoor air quality funding was channelled to transport investments (46 per cent) followed by multi-sector air pollution control programmes (32 per cent). Air quality monitoring and modelling received less than 1 per cent of funding. In the most recent five years for which data is available, 86 per cent of outdoor air quality funding provided by international development funders, or $12 billion, was concentrated in only five countries: China (37 per cent), the Philippines (20 per cent), Bangladesh (17 per cent), Mongolia (6 per cent) and Pakistan (6 per cent).
Bangladesh received a commitment of $2.4 billion in air quality finance in the seven years between 2015 and 2021. Over the past decade, much of the Department of Environment’s funds were reportedly wasted on construction, cars and foreign trips, neglecting the intended work. Under the ‘Clean Air and Sustainable Environment (CASE) Project’ funded by the World Bank, 296 officials went abroad for training, with one going 10 times but no longer working with the DOE. Despite all these investments, Dhaka’s air quality worsened. The ‘Bangladesh Environmental Sustainability and Transformation (BEST) Project’, supported by the World Bank with a budget of $484 million, is currently in preparation. Its key components include: (a) environmental governance and infrastructure; (b) green financing for air pollution control; (c) vehicle emission control through BRTA; and (d) e-waste management infrastructure. However, this project is unlikely to significantly improve air quality in Bangladesh’s major cities. The focus appears to be on heavy investment in infrastructure and capacity development, echoing past ineffective approaches, suggesting a misalignment of priorities.
What can be done?
AIR quality experts working on Dhaka’s air pollution are already well aware of the major sources and are familiar with the city’s socioeconomic structure. For international short-term specialists brought in to help, it is crucial to understand which measures are truly effective in delivering tangible results. For example, investing in BRTA’s emission inspections may not yield positive outcomes if we recognise the challenges within BRTA’s vehicle registration renewal process. Therefore, it is unnecessary to revisit these discussions here. Instead, let’s focus on highlighting the key actions that need to be taken at the source level without repeating some of the initiatives the government has already taken in the transport sector.
Alternative to bricks
FLY ash bricks are produced by blending fly ash (a byproduct of coal-fired power plants, produced in large quantity) with cement, sand, and water. These bricks are highly valued for their strength, durability, and thermal insulation. Environmentally, they offer significant benefits by repurposing fly ash that would otherwise contribute to landfill waste. Their cost-effectiveness is another advantage, as the abundant availability of fly ash minimises cement usage, reducing overall production costs while supporting sustainable construction practices. Fly ash bricks are lighter than clay bricks, have more compressive strength, and are made in a more environmentally friendly way on hydraulic machines. Bangladesh recently invested heavily in coal-fired powerplants. Few of them are already in operation (Barapukuria, Rampal, Matarbari, and Payra); coordination is needed with the Powerplant Authority for manufacturing of fly ash bricks. Relocating polluting red brick kilns from Dhaka to more environmentally friendly fly ash brick production facilities in remote areas will reduce the population’s exposure to PM2.5 by addressing a significant source of air pollution.
Transboundary pollution management
THE strong spatial interconnections between emission sources in South Asia prevent cities, states, and provinces from significantly reducing pollution on their own, even if they eliminate all local emissions. This challenge is not unique to South Asia. Other regions have adopted the airshed approach, which promotes shared responsibility for air quality across regions. An airshed, a region with shared air flow, is shaped by emissions, geography, and weather patterns, often spanning hundreds of kilometers. In South Asia, where much of the PM2.5 pollution is imported, coordinated action between cities and surrounding regions is essential for complying with national standards and achieving WHO air quality targets cost-effectively.
To effectively address transboundary pollution, which crosses national or regional borders, coordinated policies, technologies, and cooperation are crucial. Key strategies include:
Strengthen regional cooperation: Establish international agreements like the Convention on Long-range Transboundary Air Pollution (CLRTAP) and create joint airshed management plans for shared air quality goals.
Improve monitoring and data sharing: Install cross-border air quality monitors and ensure transparent data sharing for informed decision-making.
Set regional emissions standards: Harmonise emission standards and collaborate on reduction targets for pollutants like PM2.5, SO2, and NOx.
Implement market-based mechanisms: Invest in the best available emission control technologies (e.g., flue-gas desulfurization, electrostatic precipitator, NOx burner, etc.) in coal-based power plants. This can only be done by investing in regional air quality improvement projects and by engaging experts with experience in each airshed. Establish emissions trading schemes and promote green technology exchange across borders.
Strengthen legal frameworks: Enforce international environmental laws and set up compliance mechanisms for accountability.
Build capacity and share knowledge: Provide technical training, foster knowledge exchange, and support developing countries in pollution control.
Raise public awareness: Educate the public and engage civil society in advocating for regional air quality improvements.
These strategies can help manage and reduce transboundary pollution, improving air quality in Dhaka.
Institutional strengthening
HUMAN resources capacity of the Department of Environment must be diversified. DOE cannot be led by only one expertise. Staffs should have education and background in environmental engineering, environment management and science, air quality modelling, biodiversity, fisheries, GIS, climate change, etc.
Staffs can be trained in different universities as part of their continued education and refrain from expensive overseas trips (which are normally considered leisure trips) wasting taxpayers money. Various universities can be strengthened to offer this education and training to DOE and other government staffs with minimal costs. For example, BUET offers two air pollution courses, both in undergraduate and postgraduate studies. Similar courses are also offered in other government and private universities. In addition, for specialised training (e.g., dispersion modelling), expatriate Bangladeshi instructors can be recruited on a regular basis with minimal costs. They can offer both physical and online courses.
Decentralisation of administration
DECENTRALISATION of administration involves distributing decision-making, management, and responsibilities from central authority at secretariat to upazila, pouroshova, and union parishad levels. It aims to reduce power concentration, enhance efficiency, and improve responsiveness, and hence reduce the number of trips to the capital. Key forms of decentralisation include:
Political: Transfer of full decision-making to upazila administration. No interference and administrative power of the secretariat.
Administrative: Redistribution of authority to local or regional administrations (de-concentration, delegation, devolution). Secretariats will be relieved of all administrative duties of upazila.
Fiscal: Granting local control over finances and revenue. Taxes and revenues generated from the upazila should be used for the development and administration of upazilas.
This approach enhances efficiency, aligns decisions with local needs, and fosters citizen participation. While challenges such as unequal capacity and potential corruption may arise, improved monitoring and accountability can help mitigate these risks, ensuring that the benefits are sustained.
Decentralising economic and administrative activities can reduce pressure on the capital. Key strategies include:
Improving infrastructure in other regions: Investing in transportation, top-tier educational institutions, state-of-the-art healthcare facilities, and entertainment in other cities makes them more attractive for businesses and residents, easing the burden on the capital.
Relocating economic, administrative, and defence hubs: Relocating key economic hubs, such as corporate headquarters and financial districts, along with administrative offices like select ministries, and defence establishments including cantonments, BGB, Air Force, and Navy headquarters, to other regions can significantly shift traffic patterns, reducing the need for people to travel to the capital for work.
Encouraging regional development: Offering incentives like tax breaks, subsidies, and infrastructure investment can encourage businesses to set up in other cities or rural areas, decentralising economic activity.
Reducing the capital’s centrality: The goal is to make Dhaka less essential, so people can avoid expensive trips to Dhaka for administrative, educational, or healthcare needs.
By dispersing economic, governmental and social functions, the capital becomes unattractive, less congested, improved air quality, and more liveable as activity and traffic are spread across a wider region.
Dr Masud Karim, an expatriate Bangladeshi based in Toronto, is a renowned environmental specialist engaged in some of the major infrastructure projects in South Asia.