The Capital City Dhaka with a population close to ten million is reported to have serious air pollution from vehicular emission affecting public health badly. This paper deals with 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 in 2001 (from July 19 to August 01 and August 26 to September 08). The study spot was located in an important commercial district handling heavy traffic. The parameters measured by EMU were: CO, SO2, NO, NOx, CO2, total hydrocarbon (THC) and O3. Particulate matter 10 micron (PM10) was measured with an Anderson High Volume Sampler.
The concentrations of the measured parameters remain low from midnight to 8 am; and then increase and attain peak values during 7pm –11 pm. The concentrations depend on traffic volume and types of vehicles. The concentrations of the pollutants measured exceed the standards set by DOE Bangladesh and US EPA. The vehicular emissions mainly contribute to air pollution of the area. Air pollution levels on the weekdays are higher than weekends as the vehicular traffic increases significantly during weekdays. The rain and wind condition have noticeable influence on the concentration of the parameters measured. The rain decreases the concentration of CO2, NOx and SO2 in the air. The concentration levels of the parameters measured from 7 pm to 11 pm during the period exceed the standard values recommended by DOE Bangladesh. The measured concentrations of PM10 ( 10 micron) are high compared to the US EPA standard values, the average concentration being 427 ìg/m3 against 150 ìg/m3.
When this study was carried out the gasoline used was unleaded. From 2002 January, the two stroke engine vehicles have been replaced with CNG fuelled 4-stroke engine ones in the city limit; more CNG fuelled vehicles are on the road; and new standards require lower sulfur in diesel. The World Bank funded on-going studies on air quality of the city by DOE Bangladesh will demonstrate the impacts of these steps.