MED HISS project aimed at contributing to the updating and development of European Union environmental policy and legislation, in order to mitigate adverse health effects of air pollution. For many years the understanding of the association between long term exposure to air pollution and adverse health effects was based on cohort studies from USA, Canada, Japan, China. In recent years, new studies have been conducted in Europe, but often with restrictions on age of cohort recruited, on pollutant studied, and with poor geographical variability (mainly on urban areas). Health Impact Assessment (HIA) previously done on European population could have been biased due to the use of risks estimated from northern American cohorts to European population, exposed to different particulate chemical composition as well as with different population characteristics.