The last decade has shown an increase in public and government concern about environmental issues due to air pollution, in particular, that generated by man-made processes. The air pollution problem is widespread throughout the world and the elimination of the risks to human health is of paramount importance. Urban areas are one of the major sources of air pollution having characteristic patterns of pollutant emissions, with adverse consequences to the health of their inhabitants. The problem of urban air quality is of international concern, as it applies to cities throughout the world, to a lesser or greater degree. This book is the first of a series focusing on urban air pollution and contains a selection of invited review articles on topics in this field. In particular, it covers the mathematical modelling of mesoscale atmospheric dispersion. Topics include: urban heat island and air pollution; photochemical modelling of pollution scenarios in Mexico City; the reactivity of emissions - the set of conditions prevailing in Mexico City; intense pollution at Mexico City - ozone and solar ultraviolet radiation; spatial and temporal evaluation of automotive emissions for an urban area; T emissions on the mesoscale environment; air pollution in Athens; landfill emissions of gases to the atmosphere; importance of transport processes in the urban air quality; air pollution levels and trends from 1972 to 1992 in Belgium; atmospheric pollution in the Lisbon Airshed; air quality study for the city of Graz, Austria.