Background The health effects of air pollution have been subject of intense study in recent years. Exposure to pollutants such as airborne particulate matter (PM) has been associated with increases in mortality and hospital admissions due to respiratory and cardiovascular disease. PM is a complex mixture of microscopic particles derived from anthropogenic and natural sources. It is still a major environmental problem in several EU countries. While strategies for controlling anthropogenic emissions in European urban areas have greatly improved, the quantitative result of changes in human exposure to specific toxic particle compounds is largely unknown with respect to each of the emission sources. Objectives The main objective of LIFE Index-Air – by incorporating a database of outdoor and indoor air quality and a package of models – is to develop an innovative and versatile policy tool that will establish a relation between population exposure to mixtures of PM compounds and emission sources. Specific objectives are to: Develop and implement a method for producing a versatile and long-term, decision-making tool for public authorities; Create a database on chemical constituents of PM2.5 and PM10 sampled indoors and outdoors of EU cities; Develop an exposure assessment system and an operational platform for PM dose calculation to be incorporated into the tool; Identify the health end-points associated with the exposure to PM; Determine the contribution of emission sources to human exposure to PM and evaluate control strategies capable of underpinning the sustainable development of expected changes anticipating climate change and long-term changes in the atmosphere; and Consolidate the knowledge base to help authorities to implement the Thematic Strategy on Air Pollution and to formulate air quality action plans. Expected results: A management tool to identify efficient emission control strategies; A database on chemical constituents of PM from indoors and outdoors of European cities; An exposure assessment system; A platform for particle dose calculation; A platform for health impact assessment; A geographic information system (GIS) database covering population data, land use, micro-environments’ distribution for five European cities; Mapping of human exposure for five European urban areas at high spatial and temporal resolution, covering PM10, PM2.5 and elements regulated by EU legislation; Detailed dose calculations for individual human subjects; Meta-analysis of selected health end-points associated with the selected chemical and PM exposures; Identification of the impact of the current emission sources to human exposure levels; Identification of efficient abatement strategies to decrease human exposure to PM chemicals; Publication of 14 technical reports, covering time activity patterns, PM chemical characterisation in different micro-environments and sources’ identification, setup of the air quality modelling system, setup of the exposure model, model evaluation exercise, air quality and exposure modelling results, dose calculations for children, burden of disease associated with the target chemicals, five independent reports with guidelines for action plans (for Lisbon, Oporto, Kuopio, Athens and Venice), affecting an estimated 290 000 children (5-9 yrs), socio-economic impacts of the project; and Training materials produced and several courses/seminars organised.