Staff Correspondent

Dhaka, a city of narrow alleyways and congested streets, remains one of the world's most polluted, leaving its residents trapped in urban smog and struggling to recall the last time they breathed fresh air, as experts warn of rising life-threatening diseases due to alarming pollution levels.

The city’s air is choked with black fumes emitted from thousands of private cars, buses, motorcycles, CNG-run auto-rickshaws, and double-decker buses. Besides, ongoing construction projects, brick kilns, and industrial emissions further deteriorate Dhaka’s air quality.

Making matters worse, pollutants from neighbouring countries are also mixing with the city’s already toxic air.

Experts estimate that about 35% of Bangladesh’s air pollution originates from external sources. However, the government has yet to take any meaningful action to curb this transboundary pollution.

A City Suffocating in Smog

Since Bangladesh’s independence in 1971, Dhaka has transformed into one of the most densely populated cities in the world. The average speed of vehicles in the capital has plummeted to just 4.5 km per hour—barely faster than walking.

According to the Air Quality Index (AQI), Dhaka consistently ranks among the most polluted cities globally. On Wednesday (19 February) at 9:00 pm, Dhaka topped the list with an AQI score of 209, marking it as "very unhealthy" for residents.

A recent survey by the Centre for Atmospheric Pollution Studies (CAPS) found that air pollution in December was at its highest level in the past nine years. The situation worsened in January, with pollution levels peaking beyond any recorded in the past decade. On several days that month, the AQI surpassed 300, a level categorised as “hazardous.”

In 2023, the average concentration of PM2.5 particles in Bangladesh was 16 times higher than the World Health Organization’s (WHO) annual air quality guideline.

What is Transboundary Air Pollution?

Dr Abdus Salam, a professor in the Department of Chemistry at the University of Dhaka, explains that transboundary air pollution refers to pollutants crossing national borders. “Pollution from the Himalayas, as well as parts of India, Pakistan, Nepal, and China, reaches Bangladesh, significantly impacting our air quality,” he said.

The phenomenon is particularly pronounced in winter, when pollution from neighbouring countries drifts into Bangladesh. “The finer the particles, the longer they remain airborne and the further they travel,” Dr Salam added, drawing on his 25 years of research into air pollution.
He noted that while some pollutants travel from Bangladesh to India during the monsoon season, about 30-35% of the country’s total air pollution originates from external sources.

Prof Ainun Nishat, former vice-chancellor of BRAC University, agrees that air movement naturally carries pollution across borders. “No country deliberately sends pollution to another. However, if all nations in the region take coordinated action, the problem can be mitigated,” he said.

Dust on the Roads is Not Air Pollution

Contrary to popular belief, road dust does not significantly contribute to air pollution. “Larger dust particles cannot enter the human respiratory system, so they are not the primary health hazard,” explained Dr Salam. Instead, air pollution is driven by ultrafine particulate matter (PM2.5), which penetrates deep into the lungs and bloodstream.

He highlighted that old vehicles are major culprits in Dhaka’s air pollution crisis. “CNG-powered machines alone generate trillions of ultrafine particles. Additionally, black carbon and brown carbon emissions from outdated private cars and heavy vehicles further degrade air quality,” he said.

To address this, Dr Salam stressed the need for stricter regulations on vehicle emissions, phasing out older vehicles, and ensuring the use of cleaner fuel.

Way Forward

To combat transboundary air pollution, Bangladesh must engage in diplomatic dialogue with its neighbouring countries, Dr Salam advised. “We should urge them to control their emissions while improving our own policies,” he said.

Other measures include enforcing pollution laws, improving urban planning, and ensuring industrial compliance with environmental regulations. “We must mandate cleaner fuels and impose restrictions on high-emission vehicles. Similar policies are already in place in neighbouring countries,” he added.
Regional collaboration is essential to addressing air pollution. Countries like Pakistan, India, Nepal, Sri Lanka, the Maldives, and China must be part of the solution. “We need to implement the Kathmandu Roadmap effectively,” he said.

Professor Ainun Nishat suggested two key strategies: sharing data between countries and conducting behavioural studies to raise awareness. “Both India and Bangladesh monitor air pollution. If India warns us when their pollution levels rise, we can alert our citizens accordingly,” he explained.

Why is Dhaka So Polluted?

The primary factors contributing to Dhaka’s severe air pollution include emissions from vehicles, industrial pollution, and construction dust.

“Vehicles that burn fuel inefficiently emit black smoke. Newer cars don’t have this problem, but older vehicles with poorly maintained engines release excessive emissions,” Professor Nishat noted.

Besides, overloaded trucks struggling up flyover slopes often produce more smoke due to inefficient fuel combustion. “A truck designed for 10 tonnes often carries 25 tonnes, leading to increased emissions,” he said.

Dhaka’s rapid infrastructure development has also contributed to rising dust levels. “If you look towards the airport from Uttara, you’ll see a dense haze. Construction materials like sand and cement are often left uncovered, allowing dust to disperse into the air,” he added.

Brick kilns surrounding the city, particularly in Gazipur, also contribute significantly to Dhaka’s pollution levels. “Wind patterns carry emissions from these kilns directly into the capital,” he said.

How New Delhi Tackled Pollution

Professor Nishat pointed to New Delhi’s experience as a cautionary tale. “During the harvesting season, farmers in northern India burn leftover stubble, causing severe pollution in Delhi. At times, visibility on roads drops to just 20-25 feet,” he said.

Since burning crop residue is cheaper than removing it manually, many farmers continue the practice despite its environmental consequences.

What Happened to the Kathmandu Roadmap?

The Kathmandu Roadmap, launched in December 2022, was a joint initiative by Bangladesh, India, Nepal, and Pakistan to improve air quality across the region. The plan aimed to reduce PM2.5 concentrations to 35 micrograms per cubic metre by 2030.
However, an anonymous official from Bangladesh’s Department of Environment admitted that the initiative has lost momentum. “The roadmap was adopted, but no progress has been made. It’s now ineffective,” the official told UNB.

Echoing this sentiment, Syeda Rizwana Hasan, an environmental advisor, said, “We have not even managed to control our own air pollution, let alone implement a regional plan.”

Health Impact of Air Pollution

According to the Massachusetts-based Health Effects Institute, air pollution is the second leading cause of premature death worldwide, following high blood pressure.

Short-term exposure to polluted air can trigger asthma, heart attacks, and strokes, particularly among vulnerable individuals. Long-term exposure increases the risk of chronic respiratory diseases, heart conditions, and even early mortality.

A recent UNICEF report revealed that over 500 million children in East Asia and the Pacific breathe unhealthy air daily. The report links air pollution to reduced lung development, cognitive impairment, and increased child mortality.

Dr Salam warned that air pollution is cutting the average Bangladesh's life expectancy by six to eight years. “Every year, 150,000 to 200,000 people in Bangladesh die due to air pollution. The economic cost is staggering, amounting to around 5% of the country’s GDP—equivalent to Tk 1.6 trillion ($15 billion),” he said.

“The damage is generational. If we fail to act now, we risk losing an entire generation to pollution-related illnesses,” he concluded.