The negative impacts of air pollution on health are increasingly well understood and documented. In the literature, the health cost of air pollution has been estimated in different ways. Some papers focus on estimating the short-term impact of air pollution on mortality and morbidity; others estimate the cost associated with the induced medical treatments for the health system. In this project, we aim at estimating the short-term and long-term cost of air pollution associated with its impact on sick leave, by taking advantage of social security and fiscal data. This measure of the cost of air pollution is relevant for the State, who funds or co-funds the public system of sick leave in many countries, for firms who incur a disruption cost from sick leave episodes, and for individuals.