Dhaka Air Pollution :
Contribution by Urban Transport System
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Overview
Air polution in Dhaka is serious due to increasing population and associated motorization. Although existing air quality monitoring data is limited, it has been clearly shown that the average ambient concentrations of suspended particulate matter (SPM) and airborne lead are higher than the Bangladesh national ambient air quality standards and much higher than the WHO guidelines. The city's average SPM levels are about 2 times higher than the Bangladeshi standard of 200 µg/m3 in residential areas and are more than 10 times higher than the WHO guidelines of 120 µg/m3 (24 hours) in commercial areas. Lead levels are also high compared to other cities in the world. Although there is a lack of time-series data, the ambient air quality measurements available for 1990 and 1996 onward indicate that the air polution is worsening.
Severe air pollution is threatening human health and economic growth in Dhaka. Ostro (1994) and Brandon (1997) estimated that Dhaka encounters 3,580 premature deaths, 10 million restricted activity days and 87 million respiratory symptom days. The economic loss associated with these health problems could range from a low estimate of US$ 60 million to a high estimate of US$ 270 million, equivalent to 1.7% to 7.5% of the city's grows product. If added with traffic jams, global warming, soiling of materials, and asthetic degradation, the total cost of air pollution would be substantially larger.
Contribution of urban transport system to Dhaka's air pollution
The visible signs of ambient air quality of Dhaka is 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 green house gases due to the rapid growth in the number and use of motor vehicles. Data shows that number of registered vehicles in Dhaka has grown by 60% from 1990 to 1996. TSEVs have outgrown all other types of vehicles. The following table shows the vehicle population by type, utilization, and fuel economy.
Vehicle population, utilization, and fuel economy in Dhaka, 1996 (Source: European Economic Commission; Dhaka Urban Transport Project Working Papers)
| Vehicle population | Annual utilization (km/yr) | Total annual vehicle kms (millions) | Fuel economy (km/l) | |
| Cars & taxis | 42,000 | 19,200 | 806.4 | 8.0 |
| Jeep, station wagon, microbus | 12,000 | 19,200 | 230.4 | 8.0 |
| Diesel bus | 4,000 | 57,600 | 230.4 | 4.8 |
| Diesel truck | 5,000 | 64,000 | 320.0 | 2.4 |
| 3-wheeler vehicle | 14,500 | 38,400 | 556.8 | 2.4 |
| 2-wheeler vehicle | 73,500 | 10,000 | 735.0 | 35.0 |
Initial estimates reveal that motor vehicles annually emit 3,700 tons of particulate matters (PM10), 8,550 tons of nitrogen oxides, 50,700 tons of carbon dioxide, etc.TSEVs (mainly 3-wheeler baby taxis) are the significant contributors.
Baseline vehicular emissions inventory in Dhaka, 1996; Unit: 1,000 tons
| Particulate matters (PM10) | Hydrocarbons | Carbon monoxide | Nitrogen oxides | Lead | Carbon dioxide | Methane | |
| Light duty vehicles | 0.26 | 3.70 | 24.91 | 1.63 | 0.012 | 309 | 0.04 |
| Minibus | 0.21 | 0.12 | 0.30 | 0.58 | 0.003 | 115 | 0.02 |
| Diesel bus | 0.64 | 0.42 | 1.40 | 2.65 | 0 | 324 | 0.02 |
| Diesel truck | 1.11 | 0.74 | 1.91 | 3.61 | 0 | 563 | 0.03 |
| 3-wheeler | 0.93 | 13.52 | 16.37 | 0.07 | 0.011 | 147 | 0.19 |
| 2-wheeler | 0.55 | 3.31 | 5.81 | 0.02 | 0.011 | 50 | 0.11 |
| Total | 3.70 | 21.80 | 50.70 | 8.55 | 0.037 | 1507 | 0.40 |
Two strokes engine baby taxis pollute intensively in terms of per vehicle per kilometer driven. A typical baby taxi is driven 100-120 kms per day. Thus, in 360 days of a year, Dhaka's 30,000 strong baby taxis (<17% of total vehicles) are responsible for 25% of total vehicular PM10, 62% of hydrocarbons, and 32% of carbon mono oxide. The health related economic cost is US$ 360 per vehicle per year. The transport sector is an increasingly improtant Green House Gas (GHG) contributor. Bangladesh emitted 20 million tons of carbon dioxide in 1995 (International Energy Agency, 1995). But, public health impact of transport system is more compared to its impact on global warming.
Conclusion
Motor vehicles, especially two-strokes engine vehicles are an increasingly important source of air pollution emissions in Dhaka. Further understnading 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. Measures 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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Reference:
Xie J, Brandon CJ and Shaj JJ. Fighting urban transport air pollution for local and global good : The case of two strokes engine three-wheelers in Dhaka. Paper preseneted at the Consultative Meeting on Integrated approach to vehicular air pollution control in Dhaka held by World Bank and Department of Environment, Government of Bangladesh between April 26-27, 1998.
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© Medical Information Group (MIG), Dhaka, Bangladesh
November 22, 1998 10:19 PM
