Background

Air Pollution is one of the foremost environmental problems in Dhaka city. It continues to receive a great deal of interest worldwide due to its adverse impacts on human health and welfare. Anthropogenic causes of air pollution in the city of Dhaka, primarily from fossil fuel burning, building and demolition practices, exciting road dust (especially on unpaved roads), domestic solid waste, household cooking, smoking and agricultural operations and trans-boundary issues. Many studies have found out that diseases like sore throat, breath, chest pain, nausea, asthma, bronchitis, and lung cancer have a chance to occur because of air pollution. However, various scientific studies in Bangladesh have already identified all the sources, causes, and impacts of air pollution. Hence, now we have to give our focus to the reduction of air pollution in Dhaka city.

In Bangladesh, air pollution becomes most severe in the winter season (December to February), followed by post-monsoon (October-November). Based on characteristics of air pollutants and its sources, the control strategy would be in three stages for the permanent solution of the air pollution problem in Dhaka city. The High Court issued the nine-point directive on January 13, 2020 to curb air pollution in Dhaka city after hearing a writ petition filed by the Human Rights and Peace for Bangladesh (HRPB). On Tuesday, November 24, 2020 again The High Court ordered the authorities concerned to take steps within 30 days to implement its nine-point directive given earlier (on January 13, 2020) to bring down air pollution level in Dhaka and its adjacent areas. With supporting these nine-point, following suggestions could be consider by government to curb air pollution in Mega cities-

A. Short-term Strategy

For curbing air pollution in Dhaka city a short term strategy is a practical method for dealing with, especially worthwhile now as we are in abnormal or emergency situations in terms of air pollution and thus use of all available resources is necessary. The government can take following strategies which may accomplish right at the moment.

During the dry seasons air pollution becomes severe in Dhaka city. So, for personal protection from corrosion using improved quality masks could be a temporary solution for the individual. However, to reduce air pollution in Dhaka city, the coordination of governmental bodies is mandatory. In Dhaka city, the roads are digging by WASA, Cable Network Company, Gas Supply Company etc. for their renovation of services in every winter season in Dhaka. If, both bodies maintain the integration process to dig the roads for their renovation work it may reduce the emission of air pollutants from construction activities. Besides, the government must ensure that road building or excavation work or carpeting is done in compliance with the laws and regulations and that construction materials are shielded so as to prevent dust from spreading during work. Besides, it may also reduce the residence's suffering from traffic jam.

During the dry season, specially November to March, the government can take the initiative to watering in the roads two times in a day. Dhaka WASA, City Corporation, Fire service and Bangladesh police department have a good number of water sprinkling vehicles. So, the government can use it during winter seasons to wash the roads to reduce the dust particles in Dhaka city temporarily. The government can also issue a request to the city corporation to request the authorities of each building to spray water on the street in front of their building every two to three hours on their own initiative. And in this work they can use the water created from AC. More than 3 lakh ACs are used in Dhaka city. Because of condensation an AC with a capacity of 2 tons produces at least 2 liters of water every two to three hours as a by-product.

We must ensure that trucks transporting sand, soil or building materials in the capital city are shielded. Less fitness vehicles is a significant contributor of total air pollution in Dhaka city. Hence, strict control of expired and less fitness vehicles and seize the vehicles emitting black smoke could be a useful reduction strategy. However, fixing the economic life of different cars or vehicles as per section 36 of the Road Transport Act 2018 and restrict the plying of those vehicles which have no economic life to run on roads in the capital might down pollution level. Introducing the unparalleled driving or alternative day movement according to even and odd number plates of the vehicle on different days of the week.

There are almost 1200 brick kilns in and around Dhaka city which are the top responsible air pollution sources. Apart from that, the government should take steps to shut down all illegal kilns operating without any license. Additionally, enormous tire-burning and Used Lead Acid Batteries (ULAB) factories in Dhaka city pose Dhaka to be worst. So, that should also stop to come down the pollution level. Proper waste management is must to control air pollution from municipal waste. We should ensure that all the market owners or shopkeepers keep their garbage in bags and the city corporations to remove those after the shops or markets are closed. Waste burning at the city corporation dumping station as well as on the street sides must be avoided. Dhaka North and South both city corporations have to stop open waste burring method to reduce waste volume. Regular monitoring and enforcement is mandatory to fulfill these targets. Eventually, improved cooking stoves and quality fuel in slum areas would contribute to better air quality in city areas.

B. Mid-term Strategy

There are some midterm strategies that may be taken in to account reduced air pollution problem in Dhaka city. The government can take few strategies which may accomplish within 6 months. Among this, Introduction of suction trucks and vacuum sweeping trucks instead of manual broom to clean the road and collect road dust. It may play a significant role to reduce pollution from road dust. Mandatory introduction of more separated bicycle lanes for residence of Dhaka city would be one of the major steps to reduce pollution level as the city's first bicycle lanes has been introduced in Manik Mia Avenue by DSCC in early December, 2020.

As we all know, world's forests absorb a third of global emissions every year. Particles, odors and pollutant gases such as nitrogen oxides, ammonia and sulfur dioxide settle on the leaves of a tree. Trees absorb these toxic chemicals through their stomata, or 'pores', effectively filtering these chemicals from the air. Hence, proper tree plantation and encouraging the rooftop gardening in city area may help to improve the air quality. Additionally, the number of surface water bodies should be increased. A clear improvement of air quality has seen in the locations where there are more greeneries and Water bodies. For example inside the Dhaka contentment, Pilkhana and Ramna area the air quality is much batter then the other built-up are like Motijheel, Uttara and Mohakhali area.

To reduce indoor air pollution adequate mechanical ventilation should be ensure inside the house to control indoor air pollution. Cleaner Brick making technologies such as the Vertical Shaft Brick Kilns (VSBK) and the Hybrid Hoffmann Kilns (HHKs) should be introduce instead of Fixed Chimney Kilns (FCKs). According to World Bank, Fixed Chimney Kilns contribute up to 20 percent of the total premature mortality due to urban air pollution in Dhaka. By replacing the brick cluster of northern Dhaka with Vertical Shaft Brick Kilns would reduce the impact of brick pollution on premature mortality by more than 60 percent while Hybrid Hoffmann Kilns would reduce it by 45 percent. Moreover, the government has decided to phase out the use of bricks by 2025 in all its construction works to reduce the air pollution as brick kilns are one of the major sources of air pollution in Bangladesh. The government plans to use concrete blocks in 10 percent of its construction projects from this fiscal year. According to the plan, concrete blocks will be used in 20 percent of the government's construction projects from 2020-2021, 30 percent from 2021-2022, 60 percent from 2022-2023, 80 percent from 2023-2024, and 100 percent by 2024-2025. Hopefully, the government will keep their focused more in this issue. Cleaner fuel in vehicle must be introduced to decrease the air pollution level in Dhaka city.

Number of Continuous Air Monitoring Station (CAMS) should be increased in urban as well as in semi urban areas. Data that collected by CAMS must be disseminating to public regularly through website. Besides, AQI forecasting and warning system should be introduced by Department of Environment (DoE). The most important function of air pollution early warning systems is to report the air quality by relevant departments when the air quality reaches the early warning standard. A complete pollution warning system includes the pollutant, resource, and scope of influence. Air quality forecasting is an effective way of protecting public health by providing an early warning against harmful air pollutants.

C. Long-term Strategy

The government should take separate long term plans with adding local and international organizations to a platform. The Independent Air Pollution Control Commission (APCC) or Air Pollution Control Board (APCB) may be formed as like the National River Conservation Commission (NRCC). Department of Environment (DoE) should take necessary steps to enact and implement final Clean Air Act-2019 to effectively deal with the entire air pollution as soon as possible. Proper enforcement of this act will help minimize the large number of pollution sources in the city of Dhaka and in Bangladesh. It is urgent to introduce strong city governance for proper coordination of the renovation and development activities throughout the city.

Private cars and fitness less vehicle should be avoided as this is one the main source of pollution in Dhaka city. Modern public transport with proper planning should be introduced to curb air pollution in city area. By public transport, people move efficiently while producing significantly less air pollution to move one passenger one mile than moving a person one mile in a single-occupant auto. Alignment of the city development is an important issue for the air circulation which helps to disperse the polluted air away. Nowadays, air pollution from waste burning is concern issues for Dhaka dwellers. City Corporation should not burn the waste openly to reduce its volume at dumping site. They can start using the advanced technology of incinerators to reduce waste volume. Even waste to energy project may start by the government to reduce waste volume instead of direct burning.

Recently, one of major important issue of Bangladesh is coal fired power plants installation. When coal is burned it releases a number of airborne toxins and pollutants. They include mercury, lead, sulfur dioxide, nitrogen oxides, particulates, and various other heavy metals. So, the government should escape the installation of coal fired power plan. It's time to think of introduced Artificial Rain with a weekly interval in the dry season. Eventually, more scientific research on air pollution and its impacts in Bangladesh should be done by an academician. In this stage, the government can provide financial and technical support to the researcher. Besides, basic of air pollution, sources and its impacts might be added in the school's text book. Above and beyond, environmental cadre service in the Bangladesh Civil Service (BCS) should be introduced urgently to sustainable solution of air pollution problem in district and sub-district level as well. Lastly creating more awareness through print, electronic and social media is important.

Conclusion

Better air quality is a major aspect of environment. Sustainable Development Goal has also addressed its importance. Air pollution is mentioned specifically in SDG 3 and SDG 11. By significant reduction of air pollution may contribute to achieve the targets of above SDGs. DoE has to play a vital role to implement suggested strategies to diminish this problem in Dhaka city as well as in entire country. However, the government won't be able do anything alone. They need support of mass people. With proper guidance, knowledge and motivation, the public can be made a crucial part of the air quality management in Dhaka city.

Professor Dr. Ahmad Kamruzzaman Majumder, Dean, Faculty of Science, Chairman, Department of Environmental Science, Stamford University Bangladesh, Founder and Director, Center for Atmospheric Pollution Studies (CAPS) and Joint Secretary, Bangladesh Poribesh Andolon (BAPA), E-mail: dk@stamforduniversity.edu.bd)