The air pollution in Dhaka city with a population in excess of nine million is reported to be serious and damaging to public health. Uncontrolled emission from motor vehicles has been identified as one of the major causes of air pollution.
This paper presents the findings of a study of the air pollution level of a spot in Dhaka using an Environmental Monitoring Unit (EMU of Thermo Environmental Instruments Inc. USA) continuously for a period of 28 days (from July 19 to August 01 and August 26 to September 08, 2001). The spot was selected for heavy traffic involving various types of vehicles and it is located in the commercial area of importance. The parameters measured by EMU were: Carbon Monoxide (CO), Sulfur Dioxide (SO2), Nitrogen Oxides (NOx), Carbon Dioxide (CO2), Total Hydrocarbons (THC) and Ozone (O3). Particulate Matter d10 micron (PM10) was measured with an Anderson High Volume Sampler.
Generally, the concentration levels of the parameters studied remain low from 12 pm (midnight) to 8:00 am, then these start to rise and attain the highest values during 7 pm – 11 pm. This fact indicates that the concentration levels largely depend on the number and the nature of the vehicles on the road. The results show that the concentration levels of all pollutants studied exceed the standard levels recommended by the Department of Environment (DOE), Bangladesh and the US Environmental Protection Agency (EPA).
It has been observed that the vehicular emissions are the main sources of air pollution of the area. Compared to weekends the air pollution levels on the weekdays are higher as the number of vehicles increase during weekdays. The rain and wind condition have significant influence on the concentration of the parameters studied. It has been noticed that the rain decreases the concentration of CO2, NOx and SO2 in the air. The concentration levels of the parameters studied during the period from 7 pm to 11 pm exceed the standard values recommended by DOE, Bangladesh. The measured concentrations of Particulate Matter d10 micron (PM10) are very high compared to the USEPA standard value. The average concentration is 422.7 microgram/m3 but the EPA limit is 150 microgram/m3.