The findings of epidemiological studies over the past two decades have completely transformed our understanding of the impact of acute and chronic exposure to air pollutants—particularly particulate matter and ozone—on mortality and morbidity. The health impact of air pollution is largely dominated by the long-term effects of chronic exposure to particulate matter on cardiovascular morbidity and mortality. The expected health benefits of public policies aimed at improving air quality could be quite substantial, given the large size of the exposed population. However, there remains a clear disconnect between scientific knowledge regarding the health impacts of air pollution and the lack of ambition in public policies across Europe. (R.A.)