ABSTRACT
In most major cities of developing countries, there is a large and growing population of poorly maintained vehicles with few, if any, pollution controls. Many of these vehicles are powered by unusually dirty fuels. By the late 1980s, therefore, most of the cities were experiencing serious motor vehiclerelated air pollution problems, often in addition to other serious environ mental problems. In virtually every city for which data are available, CO, Pb and SPM are the primary pollutants causing the problems. Furthermore, vehi cles contribute significant amounts of HC and NOx emissions. These are frequently toxic and contribute to photochemical smog in cities with unfavourable meteorological conditions.
