ISEE-551 Abstract: Air pollution in urban areas significantly affects human health, but a great deal of information is needed to attribute (and communicate) the risk levels to the different population categories living and/or working in a city centre. A detailed knowledge of traffic, pollutant emission and concentration patterns coupled with the population groups distribution is strongly effective to accurately assess exposure levels. Providing air pollution exposure information in urban areas on a census track basis and for long periods (hourly values for at least one year) is an ambitious goal because of the complexity of the phenomena and the wide range of variables involved. An integrated Decision Support System implementing on a GIS platform population, traffic, meteorological and air quality data together with traffic, emission and dispersion models at the proper scales is required. An application of the proposed methodology is represented by the Air Pollution Integrated Monitoring System of a medium (400,000 inhabitants) city in Southern Italy. The system core is a DSS on a GIS platform based on a complete modelling system simulating traffic distribution, pollutant emissions and atmospheric dispersion. The models are fully integrated: road network information and traffic data feed the traffic assignment model; traffic emission models (large scale and micro-scale) use the result of the previous and prepare the emission input for the dispersion models; a diagnostic meteorological model produces wind fields for the dispersion models. Different air quality models are implemented depending on the scale and on the pollutants to be investigated. Finally, GIS functions allow to overlap and merge pollutant concentration field and population groups distribution. Models outcomes clearly show that the 19th century central area is strongly affected from high emissions and concentrations levels due to traffic. Given the area is highly populated (more than 110,000 inhabitants with a population density of almost 40000 inhab/km2) and the relevant presence of commercial and institutional activities (about 37000 people work in the area), this gives rise to high exposure levels to pollutants like Benzene, PM10 and Dioxins. On the other hand industrial emission take place far enough from downtown and the sea-breeze regime allows satisfactory removal of the emitted pollutants. The proposed approach allows long term high spatial resolution both in terms of pollution levels (250m or lower square grid) and of exposed population target groups (census track data) thus being effective to investigate the interaction between airborne pollutants generated by traffic and citizen health risk.