One of the key environmental determinants for human health is air pollution, be it outdoor or indoor. Air quality in the big cities of many developing countries is abnormally poor; given the population density in these countries a large number of people are regularly exposed to high concentrations of air pollutants. Major sources of air pollution in urban areas of developing countries are exhaust from vehicles, brick kilns, industrial and construction activities, unsustainable farming, open waste dumping, and combustion of fossil fuels. From these sources, different types of gaseous compounds such as Carbon Monoxide, Nitrogen Dioxide, Ozone, Sulphur Dioxide and Particulate Matter (coarse and fine particles) can be released to the atmosphere. Among these compounds, Nitrogen Dioxide and fine Particulate Matter (PM2.5) are monitored continuously in urban areas since these compounds have adverse impacts on human health. Almost 91% of the world’s population lives in most air polluted places in the world. Particulate Matter (PM), especially fine particles (=2.5µ) which do not settle down and have the capability to remain suspended in air that eventually recognized as one of the major elements of air pollution. These fine particles originate from biomass and fossil fuel burning, brick kilns, motorized vehicles, soil dust, pollen, sea spray etc.These pollutants are inhaled by living being and suffering from acute and chronic diseases. It has been determined that worldwide more than two million deaths each year can be attributed to lung and respiratory impairment because of fine particulate matter.
Dhaka is an overcrowded city, experiencing tremendous environmental problems in which air pollution is foremost. It is among the 20 mega cities with around 20 million inhabitants (UN HABITAT) which is suffering from severe air pollution problems. According to IQAir report on 2019, Bangladesh has reached out top air polluted country in the world. Apart from, air pollution poses Dhaka to become 2ndleast livable cities in the world. PM along with other air pollutants is reported as the serious public health issue during the last three decades. Receptor modeling studies found 50% of fine particles i.e., PM2.5 are originated from vehicles, PM2.5-PM10 from mechanical processes whereas 35% of ambient PM10 and 15% of PM2.5 were found to be originating from brick kilns emissions.
A number of studies in Bangladesh showed that, the ratio of fine particulate matter is high in Dhaka city particularly in winter season which is mainly comes from burning process and vehicle activities. Brick kilns are operated in dry season (November to May) where the PM concentrations were found to be high in comparison to any other seasons of the year. A study of Center for Atmospheric Pollution Studies (CAPS) found that strong and positive correlation between PM2.5 and number of brick kilns in Dhaka city and its vicinity. Besides, the fine particles were high in predominantly motorized areas compare to vehicle free and non-motorized areas in Dhaka city.
The use of frequent watering with water trucks near major roadways would reduce airborne dust. Dust curtains placed near each of major project would lessen airborne dust. The government could require all buses be converted to a cleaner operating fuel system, such as CNG or electric operation and retire the old diesel buses. The effect of the COVID-19 lockdown on air pollution is a unique opportunity to analyze the effects of the reduction of various emission sources and can be applied to assess further air quality policies. Many scientific studies have been reported that, air pollution significantly reduced due to COVID-19 lockdown. A study done by Stamford CAPS shows, Air pollution reduced almost 30-40% in Dhaka when compare to previous year during corona period. During the lockdown in the major cities, traffic flow was greatly reduced. Improved traffic flow by increasing use of mass transit or restriction of vehicles in certain areas of each city could result in similar improvement in air quality.Emissions from manufacturing and industrial facilities were reduced since the companies were shut down. Improvement in in industrial emission standards could assist in these cities reaching similar air quality during normal operations. The policy makers can take the COVID-19 lesson to combat the air pollution problem in future days. In these circumstances, The UN General Assembly unanimously adopted the resolution to designate September 7 as the International Day of Clean Air for Blue Skies as part of an effort to improve air quality, enhance global awareness of air pollution, and promote necessary action. Improving air quality and reducing air pollution will have a positive impact on people’s health, climate, and ecosystems worldwide. At the same time, it requires the kind of immediate, integrated and decisive actions to which national governments have so far proven averse.
(Dr. Majumder is Dean, Faculty of Science,Chairman, Department of Environmental Science, Stamford University Bangladesh, Founder and Director, Center for Atmospheric Pollution Studies & Joint Secretary, Bangladesh Poribesh Andolon. E-mail: [email protected])
