The research work is made in close cooperation between researchers of Universidad Nacional de Colombia, Medellin, and UFZ-Helmholtz Centre for Environmental Research, Leipzig. The contributions of the UFZ comprise: mobile measurements in Medellin (using sensors for temperature, humidity, CO, PM(?) and a GPS); impact assessment of the collected samples (PAH) on human cell lines; proteome-analytical methods analyzing the mechanisms of health effects; modelling of the spatiotemporal distribution of air pollutants (PM, ozone, CO, …) and urban climate parameters (temperature, humidity). Laboratory analyses of samples gathered in Medellin will be made at the UFZ (PAH, VOC). The UNC contributes with data sampling (PAH, VOC) and data provision (meteorological data, classical air pollutants, socioeconomic data, census data?). An essential source of data will be the Red Aire Medellin that collects air quality data in an urban-wide monitoring network for many years. As the modelling of the urban distribution of air quality and climate data is based on land utilization, UNC will provide land use data in a spatial resolution as high as possible. An important implication of the urban air conditions is the personal burden that is correlated with adverse health effects. For a validation of the urban-wide observations and their downscaling to the locations where the individuals are, the mobile measurement-walks comprise additionally personal samplers for VOCs, ozone and PM. The combination of social and environmental data will provide an assessment of environmental justice for different social groups in the urban region. If health data are available (hospital admission data, survey data, medical emergency data) we will make a preliminary study of environmental epidemiology. Previous environmental data (collected by the monitoring network Red Aire Medellin) suggest that the dry season (Jan, Feb, March) is associated with elevated air contaminations. For that reason the dry season will be preferred for additional measurements and the results will be contrasted with the wet season and the average conditions throughout the whole year.