Following improvements in the last decade, air pollution in cities has started to increase again.
The level of air pollution experienced by people in the place where they live is an important feature of their well-being and directly affects their health. Air pollution in cities is often higher than in other areas of a country due to the geographical concentration of people and economic activities, which results in higher emissions from different sources. In the countries of the OECD, air quality can be very different across cities within the same country. For example, average exposure to PM2.5 in Santiago (Chile), Mexico City (Mexico) and Windsor (Canada) is more than five times higher than in other cities of the same country. In contrast all cities in Ireland, Norway and Finland have relatively low levels of air pollution ( 4.20). In Finland, cities of more than 50 000 inhabitants even have air pollution levels that are less than the national average. Part of the differences observed across cities are driven by characteristics of the cities, including climate, altitude, as well as population density, and the type of economic activity. However, national and local efforts to reduce air pollution, such as policy and regulation in the fields of transport, energy and economic development, play a crucial role in reducing air pollution. Improvements in air quality in a city are fairly likely to benefit all or a large part of its population. It should be acknowledged that seasonal fluctuations in air quality can occur and affect the measure presented in this report.
