Almost every day, we hear news about high air pollution episodes in cities: in Milan and Rome at the end of 2015, in Stuttgart in January 2016, but also in many other cities throughout the world. These episodes raise public concern, cause health complaints and sometimes make air pollution literally visible. They remind us time and again that air pollution is a pressing issue.

With more than half of the world’s population now living in urban areas and population and urbanization expected to grow, ever more people are exposed to high levels of air pollution in cities. The latest data collected by the World Health Organization (WHO) on urban air quality shows that worldwide, more than 80% of people living in urban areas that monitor air pollution are exposed to air quality levels exceeding WHO limits. This is a shocking number. And the impacts are grave: respiratory and cardiovascular diseases attributable to air pollution are taking a heavy toll on human health and are thought to cause around 7 million deaths per year — or the equivalent of the whole population of Bulgaria!

The economic consequences of air pollution have been documented widely. TheOrganization for Economic Cooperation and Development (OECD) recently estimated that the global air pollution-related health-care costs are projected to increase from US$ 21 billion in 2015 to US$ 176 billion in 2060. Similarly, by 2060, the annual number of lost working days (currently around 1.2 billion) are projected to reach 3.7 billion at the global level.