The prevalence of allergies, asthma and other respiratory diseases in large populations has increased in recent decades. Among other factors, this phenomenon has been connected to adverse health effects of air pollution. Although some causal links between occupational exposures and their health effects are shown, still little is known about the health risks of lifelong exposure to indoor air pollutants. To assess the health risks of indoor air pollutants at prevailing concentration levels in Europe, the Joint Research Centre of the European Commission carried out a project called "Critical Appraisal of the Setting and Implementation of Indoor Exposure Limits in the EU" (INDEX). The aims of the project were: (1) to assess health risks of indoor-originated chemical pollutants that might be regulated in the EU and (2) to provide suggestions and recommendations on potential exposure limits or other risk management measures. The results of the INDEX project should contribute to the development of an EU strategy for the management of indoor air quality. The highest priority was given in this study to: formaldehyde, nitrogen dioxide, carbon monoxide, benzene and naphthalene. Exposure limits, recommendations and management options were also given to minimize the health risks for these compounds.