South Asia has become the world's hotspot of air pollution. Bangladesh has the highest air pollution in the region. Excessive particulates as well as harmful gases have been found in the air of big cities including Dhaka. This is rapidly increasing in the air resulting in increasing risks for city dwellers, creating serious health hazards. The was revealed by a World Bank study on air pollution in South Asia last year.
The study was published in the science journal ‘Physics and Chemistry of the Earth’. Ashraful Islam, a teacher of Chittagong University of Engineering and Technology (CUET), Sarfaraz Gani Adnan from Oxford University in the United Kingdom and Khatun –E-Jannat of Leeds University were part of the study. The study was led by Ashraf Dewan, a climate change researcher at Curtin University in Australia. In addition, the Austria-based research institute International Institute of Applied Systems Analysis has worked at a part of the research.
The research has exposed another new danger regarding air pollution. It said, nitrogen dioxide gas has been found increasing in big cities of the country including Dhaka. The gas is increasing in areas where there is more population and vehicular traffic and where more development projects are underway. For so long, there had been concern about the rising PM2.5 and PM10 in the air in Dhaka. In addition to these particles, the gas is making the air more toxic.
Ashraf Dewan told Prothom Alo, “Population and residential areas are increasing in the cities. At the same time, the number of vehicles is increasing and industries are being coming up. As a result, the volume of this gas is increasing with very small particles. If these elements are not reduced in the air, most of the people in this city will gradually fall ill. Dhaka will become more uninhabitable.”
Life expectancy fell
Studies have shown that air quality in major cities in South Asian countries is 3 to 12 times worse than the World Health Organization (WHO) standards. Air pollution is the third leading cause of death in the region. On an average, 95 per cent of the people in the region are exposed to polluted air. In Bangladesh this rate is almost 100 per cent. Bangladesh is at the top in South Asia in terms of reducing the average life expectancy due to air pollution. Of these, the average life expectancy in Bangladesh is declining by 1.85 years. In India the rate is 1.56 years and in Pakistan it is 1.53.
The common perception about air pollution is that it is more prevalent on the roads or in the open. But indoors are not out of danger. Beside polluted air from outside, the use of wood, straw and other organic matter used in cooking cause this pollution. Eighty per cent of the region's population lives in rural areas, which suffer from indoor pollution.
Abdus Salam, a professor in the Department of Chemistry at Dhaka University and a researcher on air pollution, said, "Overall, we are getting a picture of pollution in big cities, including Dhaka. But in some areas the pollution is much higher than in other areas. As a result, city corporations will have to take initiatives to control region-based pollution.
The study identified a total of eight major sources of air pollution of which coal-fired power plants are at the top. This is followed by pollution of large scale industries, medium industries, small scale industries, residential and commercial areas, burning of urban waste in open space, burning of straw after harvesting of paddy and wheat, fertiliser and cattle dung and urine.
According to the research, dust (30 per cent) has the major role in air pollution in the country. Basically, the dust of various construction sites is mixing in the air and causing pollution. Almost 20 per cent of pollution comes from medium industries. Brick kilns are the source of 10 per cent of air pollution.
However, a survey conducted by the Department of Chemistry of Dhaka University in 2020 found that half (50 per cent) of Dhaka's air pollution is from smoke and dust created by burning liquid fuels. The source of 40 per cent of pollution is smoke from organic matter like straw, wood, husks and fine particulate matter. A 2015 study by the Department of the Environment found that brick kilns cause largest part (55 per cent) air pollution.
Director of the Department of Environment (Dhaka region) Ziaul Haque said, "Air pollution has been reduced due to the drives against brick kilns over the past few years. I have asked the city corporations of Dhaka division to sprinkle water on the roads regularly to reduce the pollution from construction dust. It has been instructed to cover construction materials, soil and sand.”
New risk
Nitrogen dioxide is one of the gaseous substances that pollutes the air. These gases are produced by chemical reactions due to the use of fossil fuels, black smoke from vehicles, use of natural gas without outlets, burning of kerosene, liquefied petroleum gas (LPG), tobacco, lightning and burning wood. It can cause heart disease, lung cancer and other respiratory diseases.
Nitrogen dioxide contamination was observed for 12 months from July 2018 to June 2019. A terrestrial satellite, Tropomi, has been used for data collection. At the same time the amount of pollution was also measured in the field level.
Comparing the data obtained in two methods, it was found that the intensity of pollution is higher from September to March. In November, the level of pollution became evident. Dhaka, Narayanganj, Gazipur and Munshiganj had the highest concentration of nitrogen dioxide during winter season as compared to other parts of the country. Industries are mainly situated in these districts.
Studies have shown that pollution was highest when the maximum temperature was below 26 degrees Celsius. During the monsoon, the level of pollution is usually lower due to the effects of rainfall. Urban areas with dense trees had lower levels of pollution.
Sarfaraz Gani Adnan, a teacher at Oxford University and an air quality researcher, said residents of places where there is such contamination should wear masks. Authorities can conduct campaigns. Additional taxes may be levied on polluting industries. Overall cities and industrial areas need to be decentralised.
*The report originally published in Prothom Alo Bangla has been rewritten in English by Farjana Liakat