Impact of Road Transport on Air Quality in Kenya: Roadside Survey in the Cities of Mombasa and Nairobi

Abstract

Vehicle emissions have profound implications in human health and welfare, ecosystems and on climate (Finlayson-Pitts and Pitts Jnr., 12000; IPCC, 2001; Cacciola et aI., 2002). These emissions include particulate matter (PM), NOx (NO + N02), volatile organic compounds (VOCs), CO and S02. The emission effects are governed by the chemical and physical processes in the atmosphere for example the formation of greenhouse gases like 03 and CO2, from NOx and CO, and the participation of particles in cloud formation. Airborne particles, especially those with aerodynamic diameter (da) of < :2.S urn (PM25), are respirable and they penetrate deep into the lungs (Hinds, 1999) where they can il~terfere with oxygen exchange in the blood system or carry toxic and/or carcinogenic substances into the system. CO is known to reduce the oxygen carrying capacity in the blood. VOCs and NOx are known to react under sunlight with consequences of increasing CO2 and 03 besides formation of less volatile organic compounds and acids. Small particles are efficient scatterers of solar radiation and as a result they interfere with the earth's radiation budget resulting in perturbation of the climate system. Deposited acids on ecosystems, monuments and buildings are destructive. Vehicular emissions are well documented as major contributors of atmospheric aerosol especially at urban settlement. However studies of aerosol remains limited in developing countries despit~ the much needed knowledge of their local to regional distribution. The present study involved measurements of CO, NOx and PM in Mombasa and Nairobi cities of Kenya, East Africa