Table of Contents
1.0
Introduction ................................................................................................................ 2
2.0
Description of Dhaka City ........................................................................................... 3
3.0
Problems in Dhaka City .............................................................................................. 4
4.0
Air pollution in Dhaka City .......................................................................................... 4
5.0
Factors that cause air pollution in Dhaka City ............................................................. 6
5.1.0
Diesel vehicles found causing air pollution in Dhaka city ..................................... 6
5.1.1
Air pollution in the Dhaka city Caused By Lead: .................................................. 8
6.0
Air pollution of Dhaka city environment is harmful .................................................... 10
7.0
Effects of Air Pollutants On Human Health ................................................................. 11
7.1.0
Carbon Monoxide (CO) ..................................................................................... 11
7.1.1
Hazardous Air Pollutants (HAPs) ....................................................................... 11
7.1.2
Lead (Pb) .......................................................................................................... 11
7.1.3
PM10 .................................................................................................................. 12
7.1.4
Hydrocarbon (HC) ............................................................................................ 12
7.1.5
Sulfur Oxides and Total Suspended Particulate (TSP) ...................................... 12
8.0
Proposal Of Solution For Air Pollution ...................................................................... 13
8.1.0 9.0
Control of Automible Emissions ......................................................................... 13
Conclusions .............................................................................................................. 15
References ......................................................................................................................... 16
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1.0
Introduction
Air pollution may be defined as an atmospheric condition in which various substances are present at concentrations high enough above their normal ambient levels to produce a measurable effect on people, animals, vegetation, or materials. ‘Substances’ refers to any natural or manmade chemical elements or compounds capable of being airborne. These may exist in the atmosphere as gases, liquid drops, or solid particles. Air quality has deteriorated both due to human activities, and natural phenomenon such as wind blown dust particles etc. There are two major sources of air pollution in Bangladesh, vehicular emissions and industrial emissions. However, these are mainly concentrated in the cities. Recently, air pollution has received priority among environmental issues in Asia, as well as in other parts of the world. Exposure to air pollution is the main environmental threat to human health in many towns and cities. Particulate emission is mainly responsible for increased death rate and respiratory problems for the urban population. This problem is acute in Dhaka being the capital of the country and also the hub of commercial activity. Dhaka is a major, cultural, and manufacturing center. The common types of industries in and around the periphery of Dhaka are ready-made garment manufacturing, jute, tanneries, textile, tea processing, fertilizer, cement, paper and pulp, chemicals and pesticides, food and sugar, pharmaceuticals, petroleum refinery, distillery, rubber, plastics, and brick manufacturing, assembling buses, trucks, and motorcycles, assembling radios and televisions. Air of Dhaka is being polluted day by day very badly.
Air pollution also is a contamination in the atmosphere that caused by the discharge, accidental or deliberates of a wide range of toxic substances. Often the amount of the released substance is relatively high in a certain locality, so the harmful effects are more noticeable. The major sources of air pollution are transportation engines, power and heat generation, industrial processes and the burning of solid waste. A new source of air pollution is an increasing 'hole' in the ozone layer in the atmosphere above Antarctica and also growing of global ozone depletion. Air pollution has also long been known to have an adverse effect on human beings, plants, livestock and aquatic ecosystem through acid rain (Mackenzie L. Davis, 2013).
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A Case Study of Air Pollution in Dhaka City, Bangladesh
2.0
Description of Dhaka City
The Dhaka city age is more than 400 years old. Over 400 years of this city the population of people increased dramatically. Dhaka city is live on sleeping volcano which can blow up any time that may give problem and crisis to Dhaka people (Khondkar Abdus Saleque, April, 2008). For about 37 years of independence of the capital of Bangladesh, the historic city have bears with many symbols of national pride like Language Martyr monument, Monument for martyred freedom fighters, Historic relics of Mogul Dynasty which unfortunately have become a concrete slum soaked for fresh air and thirsty for pure drinking water (Khondkar Abdus Saleque, April, 2008). This happens because the water river around the city has been polluted, the air is poisonous of obnoxious particles, gas, electricity and water are getting threatened.
Figure 1.0 : Map of Dhaka City (Khondkar Abdus Saleque, April, 2008)
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3.0
Problems in Dhaka City
Dhaka city in Bangladesh is fast turning into a civilized city. Air and water are saturated with poisonous elements, sound pollution that reaching until unacceptable limits, gas electricity and water supply crisis become increased and the depletion of subsurface of water level make the Dhaka city exposed to mild earth quake. In addition, the Dhaka city is expanding in all direction from east to west and north to south which increased the population of people (Khondkar Abdus Saleque, April, 2008). Thus, the public facilities cannot meet with the growing demand which various utilities cannot be supply because the demanding is increasing.
The
supply
of
pure
drinking
water,
safe
accommodation
for
the
growing population, appropriate sanitation, municipal waste collection, supply of electricity and gas for about 150 Million city residents are progressively turning into serious crisis. In this serious situation the news about Dhaka city air reported contained a higher proportion of lead and CO which must be considered to take precaution. Besides, the serious noises are going to unacceptable sound level which can cause hearing problem. Then, in the modern Dhaka city there are many automobiles are expanding uses in this city and all water and air environment city is not healthy because have been poison. The unhealthy environment in Dhaka city affected the city citizen with various kinds of diseases.
4.0
Air pollution in Dhaka City
Dhaka city has a very high level air pollution which air pollution has become a matter and be a great concern for Dhaka citizen in recent years. Thus, Dhaka have already realized how seriously air pollution has been poisoning life and degrading the environment. People living in major towns of Bangladesh experience the problems of air pollution in varied degrees. The number of automobiles has been increasing in Dhaka city at the rate of at least 10 per cent annually, which has been contributed to air pollution and traffic jamming. Air pollution occur because many vehicles especially diesel run vehicles, dust from roads, construction sites and toxic fumes from industries has been exposed that may lead to air pollution.
Besides, the main air pollutants is come from gasoline powered internal combustion engines which contain carbon monoxide, hydrocarbons, nitrogen oxides, sulphur dioxide particulates of lead compound and unburned carbon particles. The emissions from diesel engines are smoke, carbon monoxide, unburned carbon, nitrogen oxides and sulphur dioxide that cause 4
serious problem in air pollutant (Xie J, 1998). Air pollution seriously affects the respiratory tract and causes irritation, headache, asthma, high blood pressure, heart ailments and even cancer. If this trend of air pollution continued, those living in major cities including the capital city will become exposed to these diseases and also other complications. The air that contained lead also can become harmful and affect the central nervous system and cause renal damage and hypertension. The level of small particles which less than 10micro that present in the air was very high, which could cause severe lung cancer according to Bangladesh based Centre for Science an Environment (CSE).
The air quality of Dhaka city shows that the concentration of suspended particles in the ambient air is many times higher than normal. This air, which the city citizen and road users regularly breathe are contain lead in concentrations that almost ten times higher than the government safety standard set by the Department of Environment (DOE).
About 50 tons of leads are emitted into Dhaka city's air annually and the emission reaches its highest level in dry season which is from November to January which has been revealed by scientists of Bangladesh Atomic Energy Commission (BAEC). The density of lead in the air of Dhaka city in dry season reaches 463 monograms which is the highest in the world compared to the lead concentration in the polluted air of Mexico city is 383 monograms and in Mumbai is 360 monograms per cubic meter (Xie J, 1998).
In addition, there are two major sources of air pollution in Dhaka city which are industrial emissions and vehicle emissions. The industrial sources include brick kilns, fertilizer factories, sugar, paper, jute and textile mills, spinning mills, tanneries, garment, bread and biscuit factories, chemical and pharmaceutical industries, cement production and processing factories, metal workshops, wooden dust from saw mills and dusts from ploughed land, and salt particles from ocean waves near the and coastal lands. These sources produce enormous amount of smokes, fumes, gases and dusts, which create the condition for the formation of fog and smog. Certain industries such as tanneries at Hazaribag in Dhaka City which emit hydrogen sulphide, ammonia, chlorine, and some other odorous chemicals that are poisonous and cause irritation and public complaints (Xie J, 1998). This will cause headache and other health problems.
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5.0
Factors that cause air pollution in Dhaka City
5.1.0 Diesel vehicles found causing air pollution in Dhaka city The increased rate of urbanization in the country will affect the number of vehicles to increasing rapidly and can contribute more air pollution. The Department of Environment (DOE) and other related organizations have identified the two-stroke engines used in auto rickshaws (baby-taxies), tempos, mini-trucks, and motorcycles as major polluters. Recently, there are about 65000 baby-taxies more than 296,000 motor vehicles are used in Dhaka City alone (Motors, 1998). Moreover, the overloaded of poorly maintained old trucks and minibuses are also give the city streets emitting smokes and gases. Thus, diesel vehicles emit black smoke, which contain unburned fine carbon particles is a major problem in Dhaka city.
Vehicles that run diesel is more than 80 per cent of the air pollution in Dhaka which most of them fail to comply with the approved emission standard. About 60 per cent of the city citizen consider motor vehicles as the main source of air pollution, about 55 per cent consider diesel-run buses to be most polluting the air and 22 per cent feel that diesel-run trucks cause the air pollution. Nearly 60 per cent of the citizen said they contract diseases because of air pollution and 88 per cent believed smoke and dust are the most important air pollutants. The public perception of air pollution was revealed in the survey of Stakeholders Perception on Air Pollution by Diesel Vehicles in Dhaka City which conducted by the Air Quality Management Project of the Department of Environment and the World Bank (Core, 1998).
The visible signs of ambient air quality of Dhaka are indicating an upward trend in gross emissions in recent years. Motor vehicles, especially the two strokes engine vehicles (TSEV) are responsible for the increase in emissions of both local pollutants and greenhouse effect due to the rapid growth in the number and use of motor vehicles (Motors, 1998). Data shows that number of registered vehicles in Dhaka has grown by 60% from 1990 to 1996. The Table 1.1 shows the vehicle population by type, utilization, and fuel economy.
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Table 1.0 : Vehicle population by type, utilization, and fuel economy (Motors, 1998)
Besides, the initial estimates reveal that motor vehicles annually emit 3700 tons of particulate matters (PM), 8550 tons of nitrogen oxides, 50700 tons of carbon dioxide, 21800 tons of hydrocarbons, 37 tons of lead, 1507 tons of carbon dioxide and 400 tons of methane. The three wheeler baby taxis shows the highest contributor which can be seen from Table 1.2 below : Table 1.1 : Initial estimate of pollutants from vehicles (Motors, 1998)
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From the Table 1.1, two strokes engine baby taxis pollute intensively in terms of per vehicle per kilometer driven which a typical baby taxi is driven 100-120 kms per day. Thus, in 360 days of a year,17% of 30,000 strong baby taxis in Dhaka is responsible to 25% of total vehicles PM10, 62% of hydrocarbons, and 32% of carbon monoxide. The transport sector gives Green House Gas (GHG) and air pollution effect that may cause diseases to the Dhaka citizens. Then, Table 1.2 below shows the statistic of motorized vehicle by type on road in Dhaka city. Table 1.2 : Motorized Vehicles by Type on Road in Greater Dhaka (Motors, 1998)
5.1.1 Air pollution in the Dhaka city Caused By Lead: The International Atomic Energy Agency (IAEA) stated in its News Briefs, the pollution levels of lead in Bangladesh are the highest among the world during dry season (Xie J, 1998) . According Dr. M. Khaliquzzaman, a chief scientific officer of Bangladesh Atomic Energy Commission (BAEC) the lead pollution occurs during the levels falling periods of medium and heavy rainfall which attribute to the high lead levels to the use of leaded fuel in vehicles. He said that lead can cause a public health danger especially to children which the lead can get through the human body by penetrating the lungs and entering the blood stream and can lead to impaired intelligence or mental retardation (Xie J, 1998). The effect of lead by penetrating the lungs and entering the blood stream may cause irreversible neurological damage as well as renal disease, cardiovascular effects, and reproductive toxicity. The Table 1.3 shown the statistics of lead during season in Dhaka city, Bangladesh :
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Table 1.3 : The statistics of lead during season in Dhaka city, Bangladesh
Table 1.4 : Lead dispersion and lead in gasoline in Dhaka
From the Table 1.4, the lead acces in the Bangladesh Gasoline because of the Eastern Refinery processes Arabian Light Crude which lacks branch chain or cyclic hydrocarbon. It is a small skimming refinery which performs crude distillation. Then, Gasoline produced has low octane number which used Lead as a based additive to increase octane number. One of most common additives is TEL (Tetraethyl lead) and TEL is 100% imported. Automobiles that only used old technology with soft valve seats need some lead for lubrication in order to avoid valve recession. A lead level around 0.02 to 0.05 g/l is sufficient to this technology.
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6.0
Air pollution of Dhaka city environment is harmful
The volume of poisonous particles in the city air has the level limit for human body in recent years. The Dhaka city citizens are at a serious health risk due to the highly polluted air. According to the experts of Air Quality Management Project (AQMP) under the Department of Environment (DOE), the increasingly high concentration of toxic elements in the air cause a fog in the city sky and may harmful to the citizens that going outside (Core, 1998). The AQMP advised the city citizens to stay indoors during this time to avoid health hazards from the pollution.
According to the Department of Environment (DOE), poisonous carbon monoxide, sulphur dioxide, nitrogen dioxide, suspended particulate matter (PM-10) and particulate matter (PM2.5) exist in Dhaka's air is harmful for human body (Core, 1998). Thus, the increases of PM10 and PM-2.5 may cause people lose lung function and suffer from chronic respiratory and cardiovascular diseases while nitrogen dioxide increase risks of bronchitis and pneumonia and nitrogen dioxide causes respiratory infection. Carbon monoxide will reduce delivery of oxygen into the human body and cause headache.
According to AQMP, faulty vehicles are the largest source of air pollution. Only the diesel-run vehicles contribute about 60 per cent of such particles in the air. 70% of the diesel-run vehicles, mainly buses and trucks are emitting toxic particles beyond the permissible limit. In other hand, the brick kilns in the northern edge of the city contribute at least 20 per cent to the air pollution. There are 4,000 brick kilns around the city which use tyres, wood and lowquality coal which can emitted poisonous particles into the air (Motors, 1998).
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7.0 Effects of Air Pollutants On Human Health
7.1.0 Carbon Monoxide (CO) This colorless,odourless gas is lethal to human within a few minutes at concentrations that more than 5000ppm. CO reacts with haemoglobin in the blood to form carboxyhemoglobin (COHb). Haemoglobin has a greater affinity for CO than it does for oxygen. Thus, the formation of COHb effectively removes the oxygen body. If CO is exposed to human inhale, it will be absorbed from the lung alveoli 300 times faster than oxygen. High concentration of CO in blood makes heart difficult to pump blood through arteries. Thus, it will cause circulatory ailments and chronic pulmonary disease (Mackenzie L. Davis, 2013).
7.1.1 Hazardous Air Pollutants (HAPs) Exposure to air toxics in the work place is generally much higher than in ambient air. The HAPs regulated under the NESHAP program have been identified as casual agents for many type of disease. For example, asbestos, arsenic, benzene, coke oven emission and radio nuclides that may cause cancer. Mercury is released during the combustion of coal. Thus, it is one of HAPs that wide spread to the environment and who are exposed to it will lead to poor performance on neurobehavioral tasks such as those measuring attention, language skills and verbal memory (Mackenzie L. Davis, 2013).
7.1.2 Lead (Pb) Lead is a cumulative poison. Lead can be ingested in food and water as well as being inhaled. For that ingestion, around 5 to 10 per cent is absorbed in the body (Mackenzie L. Davis, 2013). Those portions that not absorbed are excreted in the feces and urine. Lead is measured in the urine and blood for checking the lead poisoning.
Acute lead poisoning can cause milld anaemia which deficiency of red blood cells. If the blood level of lead is greater than 120 µg/100g it will cause acute brain damage (Mackenzie L. Davis, 2013) Then, the atmospheric lead occurs as a particulate. The particle size range is between 0.16 and 0.43 µm. it will be harmful to human that inhaled the air which cause fatigue, mild hedacheand others.
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Exposure to NO2 concentrations above 5 ppm for 15 minutes will lead in cough and irritation of the respiratory tract (Mackenzie L. Davis, 2013). If the exposure of NO2 is continued, it can produce abnormal accumulation of fluid in lung which causes pulmonary ederma.
The gas of NO2 reddish colour is in concentrated form meanwhile for brownish yellow is at low concentration of NO2. NO2 causes damages to bronchioles and alveolar ducts. NO2 is also suspected to impair the defense mechanism of respiratory system.
7.1.3 PM10 A large particle cannot inhale deeply into the lungs. This is why EPA switched from air quality standard based on total suspended matter to one based on particles with an aerodynamic diameter less than 10µm (PM10) (Mackenzie L. Davis, 2013).
The higher particulates level will increase risk of respiratory, cardiovascular and cancer that can cause death and also pneumia and lung function loss. Hence, diesel emits suspended particulate matter (SPM) which contains shoot. Shoot is responsible for reduction of atmospheric visibility and absorb and carry organic compound to lungs.
7.1.4 Hydrocarbon (HC) Unburnt hydrocarbon may form ozone with oxides of nitrogen which is a central nervous system depressant. Other hydrocarbons cause convulsion of CNS.
7.1.5 Sulfur Oxides and Total Suspended Particulate (TSP) The sulphur oxides includes sulphur dioxide (SO2), sulphur trioxides (SO3), acids and salts of their acids. Sulphur oxides can be caused by volcanoes, industry and ocean that emit sulphur oxides. The exposure of sulphur oxides can be suffering to chronic bronchitis.
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8.0
Proposal Of Solution For Air Pollution
8.1.0 Control of Automible Emissions
1. Blowby
The flow of air past the moving vehicle is directed through the crankcase in order to rid it of any gas-mixture that has blown past the piston, any evaporated lubricant oil and any escaped exhaust product. The air is drawn in through a vent and emitted through a tube xtending from the crankcase at a rate that depends on the speed of the car. About 20 to 40 per cent of the car’s total hydrocarbon emissions are sent into the atmosphere from the crankcase. These emissions are called crankcase blowby. All vehicles manufactured after 1963 are required to have a positive crankcase ventilation (PCV) valve to eliminate blowby emissions (Mackenzie L. Davis, 2013).
2. Fuel Tank Evaporation Loses
Evaporation of volatile hydrocarbons from the fuel tank is controlled by one of the systems. The simplest system is to place an activated charcoal adsorber in the tank vent line. Thus, as the gasoline expands during warm weather and forces vapour out of the vent, the hydrocarbon is trapped on the activated carbon.
3. Engine Exhaust
Engine exhaust becayse of engine modifications are not sufficient to meet stringent emission standard which an external catalytic reactor is placed on the exhaust system. The function of catalytic converter is to promote the reactions that convert NO2 to N2, CO to CO2 and hydrocarbon to Co2 and H2O. A three way catalyst (TWC) that simultaneously oxidizes the hydrocarbon and CO and reduces NO2 is active. The catalyst is a precious metal on an alumina support structure. Thus, the gases that entered the catalyst bed must be carefully controlled (Mackenzie L. Davis, 2013).
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However, the major problem with this catalysts are their susceptibility to be poison by lead, phosphorus and sulphur. The poisoning problem can be solved by removing the lead, phosphorus and sulphur from the fuel. The fuel modification is been implemented in 1996. In addition, diesel fuel refining is being changed so that it will contain less sulphur and emit 20 percent less VOC’s. by lowering the gasoline vapour gas will reduce the hydrocarbon emission which can reduce the air pollution from vehicles.
4. Inspection/Maintenance (I/M) Programs
The devices installed by automobile manufacturers are extremely successful in minimizing the pollution from the exhaust and from evaporating fuel. The implemented programs have been implemented to ensure the control devices. These programs require periodic checks of the exhaust and the evaporative controls. If the vehicle fails the inspection, the owner is required to provide the required maintenance and have the vehicle reinspected (Mackenzie L. Davis, 2013).
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9.0
Conclusions
In conclusion, Bangladesh be implemented a National Air Quality Standard which there are no detail air quality regulations based on which Environmental Impact Assessment could be done.. There are recommendation to reduce air pollution which are national steering committee constituting experts must be functioning to cope with the problem. Then, form a guideline for policy makers, city planners, traffic engineering practitioners towards mitigating traffic pollution problems and make recommendations for setting National Air Quality Standard.
Besides, Auto-rickshaw (AR) should be restricted in Dhaka city. Consequently, an equivalent and efficient alternative mode of transport should initiate in Dhaka so that those who are importing AR, driving AR can do the same for the new mode of transport. Current initiative of taxi-cab is appreciating, however, the pre-conditions, NEW and 2000CC car seem to be policy makers ignorance in understanding modal choice in Dhaka. A pre-condition is really necessary that is "not the diesel car".
Lastly, for motor vehicles, especially two-strokes engine vehicles are an increasingly important source of air pollution emissions in Dhaka. Further understanding of the sources of air pollution, the contribution of vehicles to air pollution emissions, and the characteristics of vehicular emission control measures is necessary to design a cost effective action plan. It is recommended that government will undertake actual measurement of emission factors, complete the emission inventory and conduct an investigation on emission control measures. A set of cost effective technical measures are already available for controlling pollution emissions by two strokes 3-wheelers. Government should strengthen vehicle emission standards, regulations and enforcement and also ensures to reduce fuel demand and improve traffic conditions are also critical to ensuring a net emission reduction and should be used as a complement to technical measures.
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References Core, J. (1998). Consultant World Bank in Dhaka. Papeworld bank in Dhanka. . Sources of air pollution and control options, 26-27. Khondkar Abdus Saleque, S. I. (April, 2008). Dhaka Sitting on a Sleeping Volcano, Bangladesh. Mackenzie L. Davis, D. A. (2013). Introduction to Environmental Engineering. McGraw Hill. Motors, U. (1998). Integrated Approach to Vehicular Pollution Control in Dhaka. Effect on Dhaka air quality by two strokes engines and suggested remedies, 26-27. Xie J, B. C. (1998). Fighting urban transport air pollution for local and global good . The case of two strokes engine three-wheelers in Dhaka.
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