Environmental problems in all major cities of Bangladesh occur due to lack of environmental facilities, such as infrastructure, coupled with the rapid rise in transport demand, industrial growth, construction activities, and open burning. Ever increasing traffic congestion in the streets, use of leaded gasoline, increasing number of two stroke engine vehicles and high content of sulfur in diesel fuel enhance sufferings of the inhabitants of Dhaka City from vehicle emissions. This demands an air quality management study for Dhaka and other major cities. A comprehensive study on air quality problems of Dhaka and other major cities is yet to be undertaken. There is therefore an urgent need to examine the present state of the problem, identify the causes and accordingly develop appropriate technological and management tools. Such investigation will provide knowledge to the urban, environment and transport planners, traffic engineering practitioners and assist policy makers to make both short and long term actions for a better future.

The proposed air quality management tool will review field surveys on monitoring pollutant concentration and data analysis, emission inventories and modeling techniques appropriate to Dhaka. It will also prepare recommendation for appropriate sustainable technology (especially in replacing two stroke engines) for low emission vehicles and alternative fuels, especially lead and sulfur free lubricants (such as CNG, LPG, etc), and review benefit-cost and cost effectiveness analysis.

INTRODUCTION

In south Asia, the number of motor vehicles will increase from 3.0 per 1000 persons in 1980 to 7.2 per 1000 persons in 2000 (Faiz et al, 1990). This rising tendency is also prevalent in Bangladesh where the number of motor vehicles per 1000 people rose from 1.4 in 1982 to 2.28 in 1991, and 2.72 in 1995 (BBS, 1995). In Bangladesh, motor vehicles are classified in the following major categories: heavy truck, tractor, bus/minibus, car, jeep, trawler, auto-tempo, auto-rickshaw (baby-taxi, mishuk), and motor cycle. Nearly one third of motor vehicles are operated by diesel (truck, bus), which contribute a greater portion of urban suspended particulate matter (SPM), sulfur oxides (SO_x), and nitrogent oxides (NO_x), sometimes private cars are energized using a proportion of (3:2) Petrol (regular gasoline) and Octane (extra leaded) (Karim, 1999). In Bangladesh, pollution severity occur due to the high content of lead in gasoline because the country's only refinery is not able to produce lead-free fuel, large number of high polluting vehicles, impure fuel, inefficient landuse, and overall poor traffic management (Karim et al, 1997). Major issues are the heterogeneous flows of traffic and two stroke engines moving in urban streets which emit greater proportion of black smoke. Another dominating factor of urban traffic pollution is the number of auto-rickshaw and auto-tempo. This increase is most remarkable in Dhaka where the proportion of such two-stroke vehicles in the total vehicle population rose from 2.2% in 1982-83, 18% in 1990-91 and as high as 23% in 1996-97 (Karim et al, 1997). It is not out of subject to mention here that the two-stroke engines (auto-rickshaw) moving in Dhaka City are simple modified forms of an Italian model of 1960's. These two stroke engine vehicles have technology disadvantages of inefficient combustion and results high tailpipe emissions. It is estimated that a baby-taxi emit several folds more pollution than a normal car. Moreover, gasoline pilfered from official vehicles find its way into the informal market for sale to the baby-taxi and auto-tempo drivers. Such pilfered gasoline is often mixed with kerosene before sale and when used on 2-stroke engines, it becomes a potent agent for pollutant emission (DITS, 1994).

The Department of Environment (DOE), People's Republic of Bangladesh, created in 1989 is the sole official agent dedicated to the scientific and regulatory measures. DOE conducted a National Environment Monitoring and Pollution Control Project funded by Asian Development Bank in 1990. In this project, it monitored ambient air quality of SPM, SO₂, and NO_x at three locations of Dhaka City. It was observed that from January to April (dry and calm season) the ambient concentration of SPM exceeded the WHO standard of 150-230 mg/m³ for daily average hourly concentration. The maximum daily average hourly concentration of SPM observed was 570 mg/m³ at Motijheel in January (Islam and Islam, 1990). However, this study did not find any alarming situation for ambient SO₂ and NO₂ concentrations. Apart from the systematic study, some additional information was obtained from the document of the DOE. Such reports indicate that SPM, SO_x, and NO_x were measured in Chittagong, Rajshahi and Khulna between 1990 to 1996 and found high concentrations of SPM and SO_x in some of the industrial areas. Another such report indicates that 1982 and 1988, 19757 vehicles (of all categories) nationwide were checked for subjective assessment through vehicle counts for environmental pollution (black smoke and noise). Of them, 13308 vehicles (67.4%) were found to be emitting excessive amounts of black smoke (DOE, 1990). The DOE conducted a 10 day (May 7-16, 1990) monitoring survey in Dhaka using a scientific smoke meter (Bashar and Reazuddin, 1991). This survey indicates that among 908 vehicles, only 126 (13.9%) emit black smoke below the standard set by DOE 65 Hartridge Smoke Unit (HSU) (DOE, 1991) and 90% of the polluting vehicles emit black smoke above 90 HSU.
 

A representative assessment of black smoke emission through vehicle count at Farmgate intersection was performed in December 1992 under the Dhaka Integrated Transport Study (DITS). Movement of vehicles was observed for black smoke emission during peak hours. Five categories of vehicles were surveyed: bus/minibus, truck, car, auto-tempo, and auto-rickshaw. Of all vehicles, 90% auto-rickshaws, 80% auto-tempos, 75% buses, and 75% trucks were observed to emit black smokes (DITS, 1994a).

Ambient air samples were collected by Hussam et. al., 1998 for 30-45 minutes by solid phase micro-extraction (SPME) at four locations near Shewrapara, Dhaka. More than 200 organic compounds were detected in the air; 35 of these compounds were identified with known chemical structures. These are normal hydrocarbons pentane (n-C₅H₁₂) through nonacosane (n-C₂₉H₆₀), aromatic hydrocarbons: benzene, toluene, ethylbenzene, xylenes (BTEX mixture), 3-methoxy benzenethiol, 1-isocyanato-3-methoxybenzene, n-propylbenzene, n-butylbenzene, 1,3,5-trimethylbenzene and 3,3'-dimethoxy-2-butanone as the ketone. Two samples collected near an autorickshaw stand contained 783,000 and 1,479,000 m g/m³ (micrograms per cubic meters of air) of VOCs. These values are 400% and 745% higher than accepted normal value of VOCs 193,000 m g/m³, respectively. In particular, the concentration of toluene (a known carcinogen) was 50-100 times higher than the threshold limiting value of 2000 m g/m³. Two other samples collected under normal traffic conditions at the mentioned site showed 135,000 m g/m³ and 180,000 mg/m³ of total VOCs.

In developing countries, higher SOx emissions from automobiles is due to high content of sulfur in fuels the poor fuel quality and the extensive use of diesel-powered, in some cases impure diesel, vehicles. Shahriar and Hassan (1993) performed a study on Dhaka City's air quality. They identified that motor vehicles, construction activities, and industries are the major contributors to Dhaka's air pollution. A study on emission source inventory performed in winter 1995-96 at Dhaka found total emissions of SO₂ and NOx to values 70 and 72 t/d, respectively (Azad & Kitada, 1998). Karim et. al., (1997) assessed the total emissions from different energy consumption sectors and emission factors to transportation energy use in Bangladesh. They found that NO_x and SO_x emissions from transportation systems in national pollution averaged 34% and 47%, respectively. Emissions in Dhaka metropolitan have been increasing at a steady rate since 1990. Annual average increases of 6.5% in NO_x, 5.8% in HC, 5.9% in CO, 5.6% in PM, and 6% in SO_x emissions were observed from 1981 to 1996 (Karim et. al., 1997). Karim (1999) has undertaken a recent study for emission inventories and modeling of Dhaka metropolitan. In this study, modal contributions of CO, HC, PM, NO_x, and SO₂ in Dhaka City have been calculated by analyzing vehicle population, emission factors of mode, and total kilometers traveled by each mode of traffic. Also the daily average concentrations of CO, HC, PM, and NO_x at 82 street locations have been estimated by using Gaussian Plume Model. A comprehensive field survey of NO_x has been performed in this study, which covers 51 road intersections, one residential location, and four personal exposures.

Dhaka, Bangladesh has the highest lead pollution in the world for a part of the year, 1996, scientists at the Bangladesh Atomic Energy Commission (BAEC) observed. A 17-month survey study by BAEC scientists detected 463 ng/m³ of lead in air over Dhaka during the dry months (November'95-January'96) (Khaliquzzaman et al, 1997). Whereas, World Health Organization Standard for lead in ambient air is 50 to 100 ng/m³. A recent survey performed by the Health Economics unit of the Ministry of Health and Family welfare indicated that the concentration of lead in blood among the residents of the metropolis has reached alarming levels. Blood samples of 39 people that were analyzed under the survey were all above the maximum tolerable limit of 10 mg/dl. The concentration levels ranged from a minimum of 13 mg/dl to a maximum of 132 mg/dl. The survey also indicated that the lead levels in the blood of 12 professionals who attend offices in the Motijheel Commercial Area averaged 55.8 mg/dl. The blood of one motor vehicle driver gave a reading of 86 mg/dl, those of six rickshaw-pullers averaged 46.3 mg/dl and those of 11 baby-taxi drivers averaged 44.6 mg/dl. Similarly three outdoor laborers had on an average 79.3 mg/dl, one traffic police had 77 mg/dl, one housewife 49 mg/dl, two indoor workers had an average of 25 mg/dl, and one student 13.6mg/dl (The Independent, 1998). Environmental problem in Bangladesh is a new issue. In an economic evaluation of air pollution in Bangladesh, the World Bank estimated that nearly 15,000 deaths would be avoided annually (10,800 in Dhaka, 2,060 in Chittagong, 1,020 in Khulna, and 975 in Bogra), if the level of air pollution in Bangladesh four largest cities reduced to the WHO annual average standard. In addition, there would be an estimated 6.5 million fewer cases of sickness requiring medical treatment; and 850 million fewer restricted activity days, respiratory symptom days, cases of lower respiratory illnesses in children, and other minor sicknesses. The economic cost of this sickness and death is estimated to be US$200-800 million per year, or 0.7% - 3.0% of GDP per year (Brandon, 1997).

Many urban areas of the world have high concentrations of air pollution sources resulting from human activities; sources such as motor vehicle traffic, power generation, residential heating and industry. Urban air pollution not only represents a threat to human health and the urban environment, but it can also contribute to serious regional and global atmospheric pollution problems. Air pollution is experienced in most urban areas and is therefore a worldwide problem and an issue of global concern. It has been estimated by World Health Organization (WHO) that globally about 500,000 people die prematurely each year as a consequence of exposure to ambient pollution of suspended particulate matter. Increases in morbidity from respiratory diseases due to air pollution are estimated to occur about 40 million; several million infants die each year from acute respiratory infections exacerbated by air pollutants.

Cities in developing nations are increasing rapidly in size and diversity. The marked increase in urban populations occurring in many cities, together with industrialization, will lead to an increase in the emissions of pollutants and to an increase in public and environmental exposure to these pollutants. By the year 2000, close to 6,000 million people will be living in the world and it is expected that about 45% of them will be in urban areas. Increasing emissions from vehicular traffic, industry, domestic heating (in temperature climates), cooking, and refuse burning all pose potential risks for large air pollution exposures. The rapidity of economic development combined with the lack of emission controls makes Asia's megacities prone to more serious air pollution problems than similar cities in industrialized nations.

This paper intends to review available literature on air pollution problem of Dhaka, discusses a tool to manage air quality and provides available research results. The management tool presents in this study will help decision makers planning future projects on air quality management, assists researchers to undertake future study, and provides a basis for development plan for all urban areas of Bangladesh.

Air Quality Management

Poor air quality due to pollution is a serious environmental problem in most urban areas. The greatest burden of pollution is on human health. Urban air quality management requires an integrated approach that (i) identifies the most serious problems and measures that offer cost-effective and feasible solutions across a range of economic sectors and pollution sources including industries, utilities, traffic and households; and (ii) builds a consensus among key stakeholders concerning environmental objectives, policies, implementation measures and responsibilities.

Rapid urbanization, motorization and economic growth are contributors to an increasing air pollution problem in most large developing urban centers. Comparative risk assessment and health studies, carried out in a number of cities (e.g., Bangkok, Cairo, Mexico City, Quito, Santiago, cities of Central and Eastern Europe), have indicated that typically fine suspended particulate (PM₁₀ and smaller) and exposure to lead (Pb) cause the greatest damage to human health. Other pollutants of concern are sulfur dioxide (SO₂) (to the extent it contributes to fine particulate and long-range environmental damage); ozone (O₃) (mainly in warmer, sunny locations with unfavorable topographic conditions), volatile organic compounds (VOC) (some of which are known carcinogens); nitrogen oxides (as contributors to ozone formation) and carbon monoxide (CO) (associated with global warming).

An air quality management system (AQMS) has the following components:

• Air quality assessment;
• Environmental damage assessment;
• Abatement options assessment;
• Cost-benefit analysis or cost-effectiveness analysis;
• Abatement measures selection (action plan); and
• Optimum control strategy.

Air Polluting Activities and Emissions

An emission inventory contains a list of relevant air pollutants in the area, broken down by activity sector, for example, traffic, industry, construction, and open burning. The inventory is usually geographical, based on the locations of industries, major roads and population distribution. Depending on the level of detail of activity data, emissions per sector are further divided into emissions per process, technology, and class of vehicles or other factors and as a function of time. Figure 2 indicates an emissions module.

Dispersion Conditions and Modules

Dispersion module is a tool to calculate air pollution concentrations in urban areas as a function of time and location. For primary pollutants (i.e. non-reacting compounds), modules can calculate contributions to local concentrations from each activity or technology sector. The elements of a dispersion module are illustrated in Figure 3. The input parameter required for emission dispersion calculations include data on meteorology, topography, emission characteristics of sources, and data from the emissions module. Meteorological data consists of wind speed and direction presented as time series (hourly averages) or as climatological statistics (wind roses, annual or seasonal), temperature and its variation at different altitude. Topography (like street canyon, high-rise buildings etc) and the presence of water bodies, land or vegetation, influence of wind and hence dispersion and in turn, pollution concentrations. It is observed that wind speed greater than 3.0 m/s can transport all pollutants from the ground level (Karim and Matsui, 1995).

Air Pollution Exposure and Damage Assessment

An exposure module shown in Figure 4 provides data on the impact of air pollution on human health and damage to ecosystem, buildings, and material. The exposure or impact is defined as the product of the local air pollution concentration (e.g. within a grid square), and the number of objects within that location (e.g. people and materials). A simple equation would be as follows:

Exposure = Population x Concentration

This estimates the number of people exposed to concentrations above permissible guidelines, where and how often this exposure occurs. This provides a population exposure distribution for each studied compound for each abatement scenario. The concentrations may be calculated as averages over differing periods (annual, monthly, daily, hourly) depending upon the pollutant in question, and the averaging time specified in the air quality standard or guideline. For pollutants that have acute effects like SO₂, O₃, and CO hourly averages should be considered, while for pollutants such as TSP, Pb, and persistent organic compounds, long-term averaging period are considered for damage assessment.

Categories of damage include health impacts; impact on materials, buildings, monuments; impact on plant; and higher production costs for firms needing clean air. For assessment of damage in physical terms, dose-response relationships are developed from epidemiological data and exposure distributions for people, objects, buildings, monuments, and plant between isopleths. For health damage assessment, dose-response relationships are used to identify the impact of pollution levels of several different pollutants (such as particulate, PM₁₀, lead, SO₂, ozone, NO₂) on various aspects of public health. Air pollution related premature death, respiratory hospital admissions, emergency room admissions, restricted activity days, cases of chronic bronchitis, asthma attacks, respiratory symptom days, and lower respiratory tract infections in children can all be estimated. Methods for monetary assessment of damage include the valuation of productivity loss, defensive or averting expenditures, and willingness to pay to avert damage, market or non-market derived. Typical exposure and damage assessment modules are shown in Figures 4 and 5, respectively.

Cost-benefit Analysis and Cost-effectiveness Analysis Module

The goal of cost-benefit analysis (CBA) and cost-effectiveness analysis (CEA) is to investigate and identify the best set of measures. In CBA, the costs of a set of measures are compared to the benefits; for example, reduced environmental damage would be calculated in monetary terms. Because the monetary estimation of reduced environmental damage (a benefit) is usually not accurate enough to compare to costs of achieving such an outcome, CEA is often used as an alternative. In CEA, benefits like reduced environmental damage are not monetized. Standards are set for emissions or concentrations, and the set of measures, which meets such standards at the least cost selected. A typical CBA and CEA module is shown in Figure 6.

Both methods must analyze three kinds of costs: investment, operation, and maintenance. The discount rate serves to convert estimated costs (and in CBA, also the benefits) over various years into one discounted number.

Abatement Measures Selection

Policy Instruments

Environmental authorities normally use a broad range of policy instruments to prevent and combat air pollution. In practice, however, the choice of instruments is limited by a number of factors, including the following:

• Legal and institutional framework,
• Technical feasibility,
• Administrative feasibility,
• State of knowledge for use of the instrument,
• Public support,
• Economic costs,
• Distribution aspects of costs, and
• Influence on technological development.

There are number of technological developments in vehicle engine for the last decade, such as low emission vehicle, alternative fuel vehicles, zero emission vehicles, electric vehicles. Proper technologies appropriate to Bangladesh socioeconomic condition in each sector can be proposed to reduce emission in transport and other sectors.

Economic Instruments

Typical economic instruments are:

• Environmental charges or taxes for high emitting vehicles and industries,
• Subsidies and tax credits on emission reduction,
• Liability for environmental damage by high polluter.

• Awareness building, creating a sense of responsibility, and the provision of information are the main elements of a communication plan. Specific information to the target groups like: advisory centers and information services for specific branch of industry; educational and training courses; publicity and propaganda for clean products and courses of action and directions for an environment-friendly way of using products and appliances.
• Environmental Impact Assessment is not an environmental policy instrument but a procedure that assists in environmental decision making.

• Air pollution control institutions
• Air pollution laws and regulations
• Levels of government.

Objectives of air quality management study are to develop data base on air pollutants (e.g., CO, HC, NO_x, SO₂, organic compounds, and particulate matter) from various sources in Dhaka City, determine level of air pollution at major problem areas/locations, and study possible relationships among source types/classes, source composition (e.g. factories/industries, motorized and non-motorized vehicles) and traffic congestion and pollution. Results obtained from such study can be used to identify strategies and formulate guidelines for better management of air quality related problems in Dhaka as well as in other cities.

Specific objectives are as follows:

• estimation of the extent of emissions of pollutants (e.g., CO, HC, NO_x, SO₂, VOC, and particulate matter) from point, mobile, and area sources in Dhaka City using real world emission and modeling technique.
• measure meteorological parameter like, hourly wind speed and direction, temperature, and humidity.
• establish dispersion models capable of dealing with the complex canyon-meteorology- dispersion conditions and improve the input database to such model, regarding hourly air pollution concentration data, hourly dispersion parameter, spatial resolution, and hourly emissions data.
• identify major problem areas/locations with respect to air pollution and examine level of air pollution (in terms of ambient concentration of major air pollutants).
• characterize industry category, traffic composition/characteristics (e.g., various categories of motorized vehicles, non-motorized vehicles and their driving pattern) in some major problem areas and study possible relationships among industry type, traffic composition/characteristics, traffic congestion, and air pollution.
• approximate the reduction of emission of harmful gases emitted by motorized vehicles and industry and calculate the effects of air pollution on health and premature death.
• identify high emitting modes and develop strategy to phase out them using proper technology replacement.
• compare the pollution situation with other developing/developed countries with particular regard to various air quality guidelines and standards (e.g., WHO).
• identify strategies, viz. planning, management, and legislative for controlling vehicle and industry emissions and suggest appropriate and effective technology and policy measures that could find applications in Bangladesh.
• perform cost-benefit analysis and cost-effectiveness analysis.
• formulate guidelines for policy makers, city planners, traffic engineering practitioners towards mitigating air pollution problems, technology transfer of vehicular modes, and make recommendations for setting Community and National Standards related to industry, road traffic, and other sectors.

The methodology to be followed should finalize following extensive literature review, discussion, and exchange of views with local and international experts. Extensive review of literature and discussion with various local organizations dealing with air pollution issues would provide an overview of environmental pollution problems in Bangladesh and abroad. It would also help acquire knowledge of technology transfer in measuring and monitoring pollution. Seminars/workshops organized in collaboration with Department of Environment, other local government organizations, NGOs, and private bodies to facilitate exchange of knowledge and experience and to finalize detail methodology.

Possible methodology should follow in order to attain the above goals is described below:

Meteorological Analyses

In addition to source characteristics and emissions data, the representative meteorological parameters from the study area is needed to perform the modeling analyses. The meteorological parameters, which influence transport and dispersion of pollution, are of importance in the modeling study. The wind speed, wind direction, temperature, humidity, precipitation, and mixing height data for the study period and study area must be gathered to run these models. The airport, weather service, transportation agencies, and government environmental agencies frequently collect these meteorological parameters. These agencies should be contacted to retrieve historical meteorological data and the representative data for the study area of analysis. If adequate meteorological data cannot be found, devices equipped with appropriate channels for collecting each meteorological parameter should be collocated with the pollution monitors or samplers during the field study. The analytical meteorological data construction models, such as prognostic or diagnostic models may also be used to complement the collected data. The statistical wind roses can be plotted for each data set and location, which will depict the predominant wind direction. The predominant wind direction allows one to construct pollution transport direction, and trace the path of pollution from the source to the impact area.

Dispersion Modeling Analyses

Real time monitoring and sampling provides a way to collect base line data, which is valuable to describe the existing level of air pollution. The monitoring methodology establishes data points applicable only to the location and time of the sampling. No prediction about the ambient level in future or other locations can be made from a single sampling event. In an urban area, such as Dhaka City, the continuous coverage of monitoring at all locations is cost prohibitive and impractical. However, by conducting dispersion modeling using the information gathered about sources and emissions, ambient concentrations of locations where monitoring data is not available can be estimated. Furthermore, the modeling technique will allow predicting future ambient levels from the emissions growth projection. The city planners and growth management agencies will find this information valuable to integrate the predicted future level of air quality in the land use decision making.

In order to analyze impacts of the industry and motor vehicle emissions, this study can select an applicable model among models currently being used in the regulatory agencies of developed nations. The United States Environmental Protection Agency (USEPA) developed a number of air quality models for its regulatory application in the field of stationary and mobile source emissions and dispersion. The US EPA has a model called �gMOBILE" which can easily be incorporated in this study to estimate total emissions of CO, PM, and hydrocarbons produced by all the modes of transportation in Dhaka city. This emissions model require detailed information on fleet characteristics, vehicle mix, driving pattern, total kilometers travel, localized cold and hot start percentages, etc. Some of these data are already available from previous studies, some can be obtained from transportation and motor vehicle registration agencies, and others can be estimated. The dispersion of emissions at an intersection or roadway can be simulated using a widely used US EPA model named �gCAL3QHC.�h Among many congested roadway dispersion studies, CAL3QHC showed a good match between observed and predicted ambient concentration for a New York City regulatory application. The CAL3QHC model demands extensive data on roadway geometry, traffic queue, vehicle count, vehicle speed, etc. While some of these data already exist and available from prior studies and respective government agencies, the field studies can be conducted to obtain other missing data. In the event, neither field studies nor prior data set is available, default parameters and the results of other studies from cities in the developing nations of South/Southeast Asia will be substituted.

Stationary sources with one or two source together can be analyzed using screening analysis. For more than two sources refined analysis are more economical. A refined analysis starts with assembling the necessary data, selecting a receptor grid, running the appropriate model, and finally analyzing the results to identify the maximum concentration.

Extent of Emissions

One of the major objectives of air quality management (AQM) study is estimation of the extent of emissions of pollutants (e.g., CO, HC, NO_x, SO₂, and particulate matter) from various categories of industries and motorized vehicles. This is usually done by experimental determination of emission factors (grams of pollutants per second for stationary source and gram of pollutant emitted per kilometer travel for mobile source) of each category (Pattas et al., 1987, Kyriakis, 1993). However, the experimental set up (consisting of a chassis dynamometer unit) for determination of emission factors from vehicles is expensive and is not available in anywhere in Bangladesh. In the absence of chassis dynamometer, an in vehicle device can be used. A device suggested by the Radian International LLC, USA (Burnette et al., 1997) can be set up for emission factors measurements. Which consists of two distinct systems; one is for collecting driving data and the other is to collect emission data. Gram per kilometer emission factors are calculated for gaseous exhaust emissions by converting the measured concentrations to gram per liter of fuel used emission factors. This gram per liter emission factor is then converted to gram per kilometer by using the measured fuel efficiencies of vehicles.

Average traffic emissions for a particular area can be estimated based on the emission factors of different vehicle categories, the average annual distance traveled by each vehicle category and the number of vehicles of each category (Kyriakis, 1993). Vehicle population and category for Dhaka City can be estimated based on data available with the Bangladesh Road Transport Authority (BRTA), while an estimate of average annual distance traveled by each category can be obtained by interviewing vehicle operators, by actual field survey (e.g., by counting mileage of vehicles of various categories for a particular period), and by the total trips of different vehicle modes and corresponding trip length (Karim et al., 1997).

Identify Black Spot Zones

Another major objective of AQM study is to examine air pollution at high concentration/frequency areas/locations (black spots). For such study, road sections with high volume of traffic can be treated as "black spots". A number of such locations have already been identified, although only limited characterization in terms of traffic composition, total trips, air and noise pollution (Rahman et al., 1992, Rahman et al. 1993) and experimental determination using passive sampler (Karim et al., 1997) have been performed for these locations. A maximum of four locations can be selected for monitoring air pollution. At list one out of these four locations should have traffic flow/volume considerably less than the others, a little far from the vicinity of road in order to be able to determine the background concentration and the effect of motorized traffic on air pollution. Another location (out of these four) should be selected on a road with only motorized traffic in order to study the effect of non-motorized vehicles on air pollution. Ambient concentrations of major air pollutants should be monitored at these locations for a period of at least one year to have close look on the seasonal and meteorological variability on pollution. Inventories of road and road side environment should be made with particular regard to quantifiable and non-quantifiable variables.

At the four selected locations, traffic composition, and characteristics (e.g., traffic flow, modes of vehicles, motorized vs. non-motorized vehicles, average speed and hourly variation of these parameters) should be determined through actual field survey over extended period of time.

It should be noted that hourly average emissions for a particular road could be estimated based on hourly traffic flow, fleet composition, road geometry, and emission factors of kilometerage travel. Such an approach has been adopted by Kyriakis (1993) to estimate traffic emission in some major roads of a city where traveled distance for each vehicle has been taken as the geometrical length of the road. Following this approach traffic emission for the four selected roads should be calculated based on the measured emission factors and traffic composition.

Ambient concentrations of major air pollutants, estimated traffic emissions and traffic composition data for the four selected locations shall be analyzed to study possible effect of traffic composition on air pollution levels. And determine the sources of the deadly pollutants and phase them out using modern cost-effective technology replacement. Pollution data generated will then be analyzed to get a picture of the overall pollution situation and compare it with that in other developing and developed countries with special regard to WHO and other national and international guidelines.

Exposure and Damage of Pollution

An important reason for controlling air pollutants such as particulate matter or sulfur dioxide is the damaging effects they have on human health. These effects include premature death, as well as increases in the incidence of chronic heart and lung disease. Estimates of the health damages associated with air pollution are important because they can provide both an impetus for environmental controls and a means of evaluating the benefits of specific pollution control policies. Retrospective cross-sectional and time series studies for the estimation of premature death by air pollution effects can develop the environmental model. World Bank financed studies are available for Santiago, Chile (Ostro et al, 1995) and Jakarta, Indonesia (Ostro, 1994).

Cost-Benefit Analysis

Cost-benefit analysis (CBA) and cost-effectiveness analysis (CEA) are analytical methods to select a "best set" of policy measures (Mishan, 1988). A cost-benefit framework allows us to rank air pollution control measures in order of the net social benefits each measure confers. The benefits of an environmental measure consist of reduced environmental damages. However, the calculation of total benefits of a policy measure requires the following four steps:

• estimated reduction in emissions at source,
• estimated reductions in ambient concentrations as a result of reductions in emissions,
• estimated reduction in exposure to pollutants, and
• assessment of increased health benefits.

• Calculate the discounted cost stream for each of the measures: Suppose there are n measures and discounted cost per unit reduction in pollutant is -


C₁, C₂, . . . . . . . . . . . C_n, where: C₁,<C₂<C₃ . . . . . . .<C_n
 

• Estimate emissions reduction resulting from each measure: The reduction associated with each measure is -


X₁, X₂, . . . . . . . . . . . . X_n
 

• Calculate the costs per unit of reduction from the ratio of (1) and (2): The first t measures are chosen that satisfy the constraint -


X₁ + X₂ . . . . . . . . . . . >= T, where T equals the target reduction.
 

• Select the measure, which has the least cost per unit of reduction: The total cost across all of the most cost-effective measures required to meet the selected target is then -

The benefit/cost (B/C) ratio is a unit to assess if a set of measures is desirable or not. Only if the benefit/cost ratio exceeds the value of 1 is the set of measures worthwhile. In case of more sets of measures, one selects the set with the largest benefit/cost ratio.

Another unit that is often used is the internal rate of return (IRR). The IRR is that hypothetical discount rate at which the discounted costs equal the discounted benefits:

IRR is the rate at which

IRR should be above some minimal value (i.e. should exceed the official discount rate). Instead of the B/C ratio or IRR, the difference between benefits and costs (B-C) can be used as the criterion. This difference is used when, within a fixed budget restriction, the goal is to achieve maximum pollution reduction benefit.

SPECIFIC RESULTS

Sources and Mix of Emissions

Dhaka as the capital of Bangladesh has to accommodate a large share of the population, which has already crossed 10 million, with a rate of increase of about 7% per year. It is expanding rapidly due to high influx of people from the rural areas. Emissions from various kinds of diesel vehicle and badly maintained aged automobiles contribute most to air pollution. Brick has been used as the main raw materials for construction in Dhaka, a lot of brick manufacturing industries (which use coal as main fuel and operate only in winter) have grown up around Dhaka, especially in northwest and southeast side of the city. These brick manufacturing industries are another major contributors to severe air pollution in Dhaka. The anthropogenic emissions of SO₂ and NO_x in Dhaka in winter 1995-96 were computed using fuel consumption and emission factors for the unit consumption. The computed results show that the primary source of SO₂ is traffic vehicle (55.8%); followed by brick manufacturing industry (28.8%) and industry (10.5%). The remaining about 5% are due to navigation vessel in the Buriganga river, residential activity and commerce (Azad and Kitada, 1998). The primary source of NO_x emission is also traffic vehicle (54.5%), brick manufacturing industry is the second in the series (17.5%), residential (9.5%), other industry (8.8%), navigation (7.7%), and commerce (2%). Most CO emissions from vehicles are caused by incomplete fuel combustion, especially in two stroke engines and vehicles that are poorly maintained, uncontrolled (for example, vehicles not equipped with catalytic converters) or not operated at high altitudes (Onursal and Gautam, 1997). The contribution to the Dhaka City's total CO, HC, PM, NO_x, and SO₂ emission by each transportation modes are estimated for the year 1996 and presented in Figure 7.

The results indicate that auto-rickshaw and car are the major contributors to CO emission (35%), followed by motorcycle (24%) (Karim, 1999). In addition to motor vehicle exhaust emissions, major anthropogenic sources of HC include evaporative emissions from gasoline. Evaporative emissions are not included in the estimation, however it has a significant contribution in Dhaka's air. As fuels pilfered from vehicles are commerce in the open air. It has been estimated that auto-rickshaw is the major contributor of HC emission (56%), followed by motor cycle (26%). Mass transit has little contribution of HC emission. Hydrocarbon emissions are partially due to unburned fuel components, which can be reduced through improved engine efficiency. Oxides of nitrogen include predominantly nitric oxide (NO) and nitrogen dioxide (NO₂). The calculation of NO_x indicates that bus and minibus (diesel operated) and motor car have the significant contribution of NO_x (30%), followed by heavy-duty vehicles (truck and tanker) (28%). Three wheelers are the least contributing modes of NO_x in Dhaka City.

The significant pollutants from diesel-fueled vehicles are PM (including smoke) and NO_x exhaust. Because diesel engines operate at high air fuel ratios (30:1), they tend to have low HC and CO emissions. They have considerably higher PM emissions than gasoline-fueled vehicles. The estimated PM emissions from different modes indicate that around 54% emission contribution is from bus/minibus, followed by truck and tanker (26%). The modal contribution of SO₂ in Dhaka is coming from mainly high sulfur content in the diesel fuel. It is observed that buses powered by diesel fuel contributes 58% and truck and tanker emit the second largest share 34% of SO₂ emission in Dhaka City (Karim, 1999).

Emission Inventories

Gaussian Plume Model has been used to estimate pollutant concentrations at 82 road locations covering most of the major roads of Dhaka. Dhaka Urban Transport Project (DUTP, 1996) and DITS traffic data, road geometry, meteorological parameter have been used. DITS traffic data

(DITS, 1993c) have been extrapolated taking into account a 20% growth rate in traffic flow from 1992 to 1996. Traffic data are average of 16 hours traffic from 6:00 to 22:00 hrs. Traffic counts were taken for each 15 minutes period on each direction of movement for all modes of vehicles. Figure 8 presents black spots and the corresponding contribution of modes at 82 road locations of Dhaka. Top 5 locations polluted by CO are Moghbazar, Kakrail, Bijoynagar, Mohakhali Rail crossing adjacent road, and Mohakhali (Amtala). In addition, top 5 locations polluted by HC are Moghbazar, Kakrail, Bijoynagar, Mohakhali Rail crossing adjacent road, and Sonargaon hotel round. The major contributing mode is the auto-rickshaw. The second largest contributing mode of CO is motor car. Top five polluted locations of NO_x are Syedabad bus stand, Sheraton hotel round, Sonargaon hotel round, Farmgate intersection, and Moghbazar intersection. The principal contributing modes of these areas for NO_x are truck and tanker at Sayedabad bus stand, and motor car in Sheraton, Sonargaon, Farmgate, and Moghbazar areas. Top 5 locations polluted by PM are Sheraton, Farmgate, Sonargaon, Mohakhali-Gulshan intersection, and Banglamotor. Minibus and car are the principal contributors of PM in these zones.

AIR POLLUTION CONTROL MEASURES

Common measures for reducing air pollution from motor vehicles are shown in Table 1. These measures, which target vehicles, fuels, and transport management, are classified as command-and-control measures, market-based incentives, and additional measures. These measures are sometimes accompanied by actions that promote public awareness and education.

Pollution Control Technology (Two-stroke Engine)

The first step in controlling emissions from high polluting (two-stroke) vehicle is eliminating the excessive emissions from two-stroke engines. This can be done by switching to a four-stroke design incorporating timed fuel injection and crankcase lubrication. This would reduce hydrocarbon and particulate matter emissions by 90%, at a cost of about US$60 per vehicle (Faiz, et. al., 1996). Additional emission reductions are possible with improved four-stroke engine design and calibration and through the use of catalytic converters. Catalytic converters are used on two-stroke motorcycles in Taiwan and on mopeds in Austria and Switzerland. Automobile industry did major improvements in 90�fs. Car manufactured after 1988 are 90% cleaner than 1970's model. Bangladesh government does not allow to import more than 5 years old car. Therefore, no extra precautions are necessary during import of new and reconditioned cars. However, extra precautions are needed for two-stroke engines. Because, technology of two-stroke engines are before 1970�fs. Two stroke engine vehicles can be phased out replacing Japanese light duty vehicles of less engine capacity. These vehicles will be chosen taking care of Dhaka's road geometry, financial constraints, and environmental condition. Light duty four-stroke engine vehicles are in the market in Japan with engine capacity less than 660 cc. Table 2 provides a comparison between these vehicles with locally running two-stroke engine vehicles (auto-rickshaw). These cars are 3/4/5 doors with high quality interior seating comfort, built in AC etc. To avoid chaos from political, business, and union people our recommendation is to arrange a replacement in the existing two-stroke engine vehicles�f industry sector by:

• allowing importers of two-stroke engine vehicles to import new four-stroke engine vehicles.
• allowing importers of two-stroke engine parts to import new four-stroke engine parts, and
• providing permissions of driving new four-stroke light duty cars to those who have been driving two-stroke engine vehicles.

Fuel Targeted Measures

Lead in Gasoline

Exposure to lead is one of the most significant yet preventable threats to human health in the world today. Lead has no known benefits to human health and can adversely affect the neurological system. While all individuals are susceptible to lead�fs effects, the low body weight and maturing neurological systems of children make them particularly vulnerable. Children exposed to even low levels of lead may suffer reductions in IQ and develop learning disabilities. Research indicates that 10 microgram/deciliter increase in children�fs blood levels results in a two to four point drop in IQ. Persistent exposure to lead can increase the number of mentally retarded children in a society and reduce the number of children with superior intelligence. The National Environmental Council of Bangladesh at its sixth meeting in February 1999 chaired by Forest and Environment Minister of Bangladesh Government took the decision to import lead-free petroleum from July 1 1999 to minimize air pollution. The meeting also decided to impose high duties on imported two-stroke engines used in auto-rickshaws and make "catalytic converter" mandatory for buses, trucks and other vehicles. The imported fuel processed will have 0.2% lead instead of 0.5% in petrol and octane previously used by the vehicles.

This attempt by the government to supply lead-free petrol to auto operators in the country has started in August 1999 hit a snag from the very word 'go'. Reports in newspapers say that lead-free petrol being supplied to the market by the three state-owned oil companies through their agents all over the country is mixed with petrol with high lead content thereby nullifying the government's belated attempt to free the atmosphere of lead poisoning. The adulteration is said to be happening at the petrol pump end. The authorities imported 19,000 tons of lead-free petrol in July 1999 and started marketing it in late August 1999 (Ahmed and Alam, 1999). However, as there is no separate reservoir for lead-free fuel either at the terminals of the oil companies or at the pump-site, the imported fuel got mixed up with the old stock and the whole exercise backfired. This was corroborated by the pump-owners also. Since the switchover was not properly planned and executed the whole initiative of lead-free fuel supply has become a faulty system. The oil companies are marketing premier gasoline and regular gasoline and in the absence of proper storage facilities of fuel and separate pumps for delivery it will be impossible to identify leaded and unleaded gasoline. Moreover, in the absence of a particular facility at the Eastern Refinery Ltd. that separates sulfur-free diesel from lead-free petrol, the slogan for lead-free gasoline sounds hollow. However there is still time to manage the whole system of unleaded gasoline use in Bangladesh by proper planning and necessary renovation of the ERL and simultaneously supervising building of infrastructures in the marketing sector so that lead-free and leaded gasoline can be easily differentiated and accordingly used by the consumers. The elimination of lead from gasoline follows a series of events, Table 3 presents them which has been implemented in Costa Rica. Most gasoline used in Bangladesh is unleaded, hence lead pollution from vehicular emission continues to be a matter of concern. There is scope for improvement in this sector through phasing out unleaded gasoline and planning for alternative fuels like LPG or CNG for baby taxis and auto-tempos.

Sulfur in Diesel

The Sulfur content of diesel in Bangladesh is abnormally high. It is currently 1.0% (max) although BPC imports diesel containing 0.5% sulfur, compared to 0.05% in the US Europe and Japan. Sulfur is removed from fuel through a hydro-desulfurization (HDS) process. Low-pressure HDS plants can remove 65 to 75% of sulfur, reduce aromatic levels by 5 to 10%, and increase cetane number by 1 to 2. Newer HDS plants operating at medium to high pressures can remove more than 95% of sulfur and 20 to 30% of aromatics. The costs of reducing the sulfur content of diesel to 0.05% are considered moderate-less than one US cent (<49 Paisa) per liter and the estimated cost-effectiveness is attractive compared with other diesel control measures. A 1989 study by CONCAWE concluded that the costs of reducing diesel fuel sulfur content to 0.05% in Europe would be between 0.9 and 1.4 US cents per liter, equivalent to US$6,000-$9,000 per ton of sulfur removed (CONCAWE, 1989). The fixed costs of retooling refineries to produce low sulfur diesel, however, can be quite large, requiring substantial up-front investment. For example, hardware modifications to an Asian refinery to reduce the sulfur content of diesel from 0.5 to 0.2% were estimated to raise the production cost of diesel by 1.6 to 1.9 US cents (78 to 93 Paisa) per liter (Barakat, 1995). Ministry of Energy and Mineral Resources of GOB should consider to reduce sulfur content to 0.50% (max) immediately and 0.25% within very short time from diesel as a policy and issue directives to BPC/ERL.

CONCLUSIONS

An air quality management plan will enable the achievement of the objectives of the legislation on environmental protection and will minimize the health risks for the population. This study is based on literature review, existing urban air quality management plans of World Bank, abatement measures undertaken by a number of developing countries of the world. The objectives are compiled from a joint research proposal of the authors in metropolitan Dhaka, methodology of these objectives are compiled from authors previous studies and USEPA�fs international activities. The abatement measures have been analyzed in terms of their effectiveness in reducing air pollution in Bangladesh, however, a detail cost-benefit analysis needs to be undertaken for cost-effectiveness of the measures. We hope that the contents of this paper will be helpful in designing a comprehensive study in Bangladesh.

References

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• Karim, M. M., Matsui, H., Ohno, T and Hoque, M. S. (1997); Current State of Traffic Pollution in Bangladesh and Metropolitan Dhaka, Paper presented at 90th Annual Meeting of A&WMA, Toronto, Ontario, Canada, June 7-13, 1997.
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Source: Carbajo (1994)
 
 

Table 2: Comparison between auto-rickshaw & light duty four-stroke engine vehicles.
 
 

Table 3: How was lead eliminated from gasoline in Costa Rica?
 

A series of events led to the elimination of lead from gasoline in Costa Rica: Promulgation of Decree 19,088-S-MEIC-MIRENEM, which established a seven-year period to eliminate lead from gasoline (1989). Introduction of 95-Octane super gasoline, which is imported (1990). Undertaking of technical studies to evaluate alternative options for producing unleaded gasoline with 88 Octane (1991-92). Promulgation of the Transit Law, which establishes requirements for motor vehicle registration and emission standards (1993). Opinion survey of regular gasoline consumers to gather their views about the introduction of unleaded gasoline to the market and to devise a public awareness campaign strategy (1994). Introduction of an environmentally friendly super gasoline (1994). This gasoline is produced by blending imported high-octane unleaded gasoline with 10% by volume MTBE content (also imported). A massive campaign on the benefits of environmentally friendly super gasoline through television announcements and distribution of pamphlets (1994). Establishment of an inter-institutional commission for all entities involved in the elimination of lead from gasoline, including vehicle importers, the agency in charge of regulating prices, the Costa Rican Refinery (RECOPE), fuel consumers, and ministries of the environment, energy, public works, and transportation (1994). Evaluation of the impacts of lead elimination from regular gasoline (1995). Use of unleaded gasoline in RECOPE�fs entire fleet to prove to consumers that unleaded gasoline has no adverse impacts on engines (1995). Reduction of the price difference between regular and unleaded gasoline to 5% (1995). Promulgation of decree 24,637-MIRENEM-S, which prohibited the use of leaded gasoline in public institution vehicles (1995). Introduction of new unleaded gasoline called "bio-plus" (April 1996). This was done without any public announcement to allow time to clean the storage and distribution network of any residual lead. Bio-plus is prepared by blending naphtha produced by RECOPE and imported high-octane naphtha. Announcement of the introduction of bio-plus to the market and associated media campaigns through television and press (May 1996).

Source: Ministry of the Environment and Energy of the republic of Costa Rica (1996).

Fig. 1: Elements of the AQMS (Shah, et. al. (eds), 1997).
 
 

Fig. 2: Emissions module.

Fig. 3: Dispersion module.

Fig. 4: Exposure module.

Fig. 5: Damage assessment module.
 
 

Fig. 6: Cost benefit analysis module.
 
 

Fig. 7: Modal Contribution of Traffic Emission in Dhaka in the year 1996. (Source: Karim, 1999)
 
 

Figure 8: Emission Inventories in Dhaka (Source: Karim, 1999).