"Increased vehicle emission in Colombo is one of the most important environmental issues that has drawn the attention of policymakers, administrators, and environmentalists in the recent past. Various studies undertaken by regulatory agencies and researchers clearly indicate that inefficient combustion of petroleum in motor vehicles is the primary cause of growing air pollution in Colombo. Lack of information on economic and environmental costs of vehicle emission and its mitigation and prevention have inhibited public response and nforcement, and impeded the implementation of existing laws, and the development of further regulations. Policy-oriented research in these areas may contribute to a better understanding of the problem and the introduction of effective control measures.
The worst prevalent air pollutants emitted from vehicles include particulate matter (PM), lead (Pb), nonmethane volatile organic components (NMVOC), nitrogen oxide (NOx), sulfur dioxide (SO ), and carbon monoxide (CO). Of these, particulate matter and lead are the most harmful components of vehicle exhaust that affect the environment and human beings. Apart from pollutants emitted by petrol-driven vehicles, the amount of exhaust from diesel-driven vehicles is large and therefore a matter of major public concern due to its undesirable environmental effects. Although diesel-engine exhaust contains less toxic gases, it has a much higher particulate matter concentration than petrol-engine exhaust. In Sri Lanka, the observed levels of TSP, SO , O , and lead are significantly higher than air quality standards recommended by the World Health Organization (WHO) and the Central Environmental Authority (CEA) in Sri Lanka. This clearly demonstrates the special nature of the vehicle emission problem in the country which is directly linked with a wide range of factors such as composition and increase in number of vehicles, price structure of fuel, lack of traffic management, use of low-quality fuel, and absence of alternative fuels.
Colombo is the main commercial and business center of Sri Lanka and as a consequence, many people are drawn into the city daily. The central district, which comprises of Fort and Pettah, provides more than 100,000 jobs and is estimated to have a daytime population of more than 650,000. The greater Colombo area contains over 4 million people or 26% of the island's population, but covers only 5.6% of the total land area. Outside the city, Katunayake International Airport and the Free Trade Zone further increase traffic congestion in Colombo. As the most important business and dministrative center, Colombo attracts the highest number of vehicles and individuals and is therefore highly vulnerable to health hazards due to vehicle emissions."