‘Biomass burning, high sulphur-containing gasoline are compounding air pollution’

The Business Standard: The government introduced CNG three-wheelers in 2003 to reduce air pollution in Dhaka. But several studies have now traced some other factors contributing to air pollution. What are the present threats to the capital's air?

Abdus Salam: In 1996, a group of scientists from the Atomic Energy Center, Dhaka measured concentrations of the chemical substance lead (Pb) in the Dhaka air. At that time, the concentration of lead in the Dhaka air was 463 nanogram per cubic metre (ng/m3). That was the highest in the world after Mexico City. 

The alarming news spread fast through our media. The government eventually banned all leaded gasoline to eradicate lead pollution. The government also provisioned the use of lead-free octane, petrol and diesel, and motor engines devised with catalytic converters. As a result of the measures, there was a drastic fall in lead concentration in the air. Between 2003 and 2013, we had several tests and measured a downward trend of lead pollution and at one point, it was as low as 70 (ng/m3). 

However, lead contamination of the air started to intensify again from 2014 onwards. A recent study about the Dhaka air by SPARTAN (The Surface PARTiculate mAtter Network) has found lead concentration at 210-220 nanogram per cubic metre. That means lead contamination has intensified around three times compared to the lowest ever measured.

If the motor vehicles are still following the anti-lead provisions, then what is now contributing to the lead in the air? We see a huge number of battery-run vehicles plying the roads. The lead-acid batteries are recycled haphazardly. The surrounding environment is contaminated with lead when the batteries are recycled in a hazardous way. Dust in the air carries a small amount of lead. As the density of dust in the air is growing, so is the presence of lead. Amid the increased use of household electronic gadgets in the last decade, e-wastes are now piling up every day. 

Recycling the e-waste in unauthorised facilities, also releases lead into the environment. Besides the electroplating process, an ever-increasing number of constructions also contribute to heavy metal contamination of the air.

What we call the particulate matters like PM2.5 or PM10 are actually some solid matters including organic and inorganic carbon, water-soluble sulphate, phosphate, organic acids, dust and heavy metals. There are some gasses like  nitrogen dioxide, sulphur dioxide, benzene, and naphthalene in the air.  The rapid pace of industrialisation and machine-based activities that consume fossil fuels have compounded the atmospheric chemical reaction of the volatile organic substances and the concentration of pollutants like nitric oxide and sulphur dioxide has been increasing in the air.

TBS: Ingestion of dust particles and heavy metals harm people of all age groups, particularly children. Can you please tell us more about these risks on the basis of your research?

AS: I am not a physician. However, my research experience suggests that children and senior citizens are the most vulnerable population demographic because of the growing air pollution. In an environment where air is highly polluted, a pregnant mother inhales toxic air and so does the fetus. In recent times, low birth weight, childhood disability, kidney disorder, cardiovascular problems and skin diseases have become very common threats to children. 

Dr Abdus Salam. Illustration: TBS

Air pollution also impacts the cognitive development of children. High ingestion of particulate matter causes silicosis in children. Silicosis is a severe lung disease caused by inhaling large amounts of fine silica dust. Excess consumption and ingestion of chemical substances, irrespective of organic and inorganic, is injurious to health. As children and the elderly have weaker immunity, high concentrations of particulate matter harm their lungs quickly.

TBS: Some recent studies you were involved in find biomass burning and high diesel sulphur usage as among the major contributors to air pollution in Dhaka. Please tell us more about the findings of your studies?

AS: The burning of fossil fuel releases black carbon. Black carbon causes cancer. Moreover, black carbon in the air absorbs ultraviolet rays and increases the atmospheric temperature. Hence, black carbon is responsible for global warming. 

Recently we have done a carbon isotope-based study and found biomass burning is also equally responsible for black carbon emission in Dhaka city. The burning of wood, dried leaves, garbage and agricultural wastes is termed biomass burning.

Burning dried leaves to get warmth in winter is common here.  You see, black smoke has been blowing out continuously from the garbage landfills even though the government does not encourage such burning. A prominent example of biomass burning is wood burning for cooking. Still, 70% of household cooking in rural areas is dependent on biomass. 

Biomass burning in the traditional earthen stove highly pollutes the air because of incomplete combustion. Mothers, the common cooks in a traditional family structure, and often the toddlers, here are the primary victims of indoor air pollution.  Through satellite image analysis, we have spotted agricultural waste (biomass) burning in some parts of the country which is also very concerning.

The Euro VI standard suggests the diesel sulphur content (sulphur mixed with diesel) should remain below 10 ppm (parts per million). In Bangladesh, it has been said that the diesel sulphur content is below 400 ppm. However, we do not know about the composites.  Bangladesh should adopt a standard like Euro VI so that sulphur content in diesel can be reduced. Sulphur is among the major pollutants that transform into sulphur dioxide. The released sulphur dioxide induces nucleation events, like the transformation of gas to particulate matter. Due to the nucleation events, we see a sudden rise in air pollution. 

TBS: As air pollution continues unabated, what should we do? 

AS: First of all, a mass awareness about this issue covering public, private and individual entities is a must. All of us have to admit that we are dwelling within highly polluted air and we must control the emission or contamination of pollutants. Every individual should act responsibly. If an air conditioner (AC) user can correlate that their AC consumes power and power generation causes the emission of polluting gases, then they can minimise the consumption of power. This is how things can start to change but this will not happen on its own. 

Environmental laws against pollution should be implemented strictly. Even if a government project or a government vehicle pollutes the air or the environment, relevant rules must be imposed. Systematic monitoring of the quality of transport fuel and motorised vehicles is a must.

Coordination among the regulatory bodies is also a prerequisite. Infrastructural development projects need to be completed within the project tenure. Extension of the tenure creates the scope of more pollution. Naturally, wetlands absorb pollutants and keep the air fresh. But we have been destroying the wetlands in an unplanned manner. The government must restore the wetlands.  Being a teacher, I would suggest that school children be taught about environmental pollution and its consequences. 
The United States, Japan and other developed countries were once highly afflicted by air pollution. But these nations succeeded in controlling the hazardous pollutants.