Many European cities suffer from poor air quality and regularly exceed both the European standards prescribed by the Air Quality Directive and the guidelines recommended by the World Health Organization. This is particularly the case for fine particulate matter (PM10) for which both the daily and yearly average limit values are regularly exceeded in many cities and several regions in Europe. Similar conclusions hold for PM2.5 where few cities manage to keep concentrations below the levels recommended by the WHO.
Actions have been proposed and taken at the international, national and urban scales to reduce air pollution. While they have undoubtedly resulted in an overall improvement of the air quality over the years, there are still problems which are localised in specific regions and many cities. A key issue is thus to determine at which scale to act in order to abate these remaining air pollution problems most effectively. Central to this for cities, is a quantitative assessment of the different origins of air pollution in the city (urban, regional, national and transboundary) to support the design of efficient and effective air quality plans, which are a legal obligation for countries and regions whenever exceedances occur.
The “Screening for High Emission Reduction Potentials for Air quality” tool (SHERPA) has been developed by the Joint Research Centre to quantify the origins of air pollution in cities and regions. In this Atlas, both the spatial (urban, country…) and sectoral (transport, residential, agriculture…) contributions are quantified for 150 European urban areas in Europe, where many of the current exceedances to the air quality EU limit values and WHO guidelines are reported.
There is a need to provide information to improve air quality policy governance, to support authorities in choosing the most efficient actions at the appropriate administrative level and scale. In particular, actions at the local level focusing on the urban scale and at national/international level needs to be carefully balanced. Key conclusions are:
• For many cities, local actions at the city scale are an effective means of improving air quality in that city.
The overall conclusion is that cities have a role to play by taking actions at their own scale. It is important to emphasise that the emissions in cities contribute significantly to country and EU overall PM concentrations, reinforcing the important role of cities in reducing the air pollution through a multilevel approach.
• Impacts of abatement measures on air quality are city specific
The impact of a given abatement measure on air quality differs from city to city, even for cities that are located in the same country. Actions taken at different scales or in different activity sectors therefore lead to impacts on air quality that are city-specific. The diversity of possible responses to abatement measures stresses the need to take into account these city-specific circumstances when designing air quality plans. Actions that are efficient in one city might not be efficient in others.
• Sectoral measures addressing agriculture at country or EU scale would have a clear benefit on urban air quality.
Although agricultural emissions are limited in the "city" as defined here, agriculture considerably impacts air quality in many EU cities. The extent of the impact of agriculture on air quality is indicative of the potential of EU- or country-wide measures addressing this sector. Moreover, other sectoral measures can have an important potential at the urban scale even though they are applied at EU or country scale. This is the case of road transport where the EURO norms are, in practice, most effective in the areas where traffic is most important, i.e. cities.