Here are some places to trace facts on air pollution levels.
UK DEFRA has a daily monitong site of levels.
there is also
There are also local authority CO2 emissionsFor a different perspective see the Friends of the Earth campaign for cleaner air. They have a national air pollution map
Eurostat has some data on excedence of air quality levels in urban areas in EU nations.
Its website also has a larger section on air polution statistics which provides free access to a range of data topics
European Topic Centre for Air Pollution and Climate Change Mitigation (ETC/ACM)
The ETC/ACM is a consortium of 14 European organisations with the Netherlands Institute for Public Health and the Environment (RIVM) as its lead organisation.
Main tasks of the ETC/ACM are to:
Assist the European Environment Agency (EEA) in its support to EU policy on air pollution. Its website provides free access to reports, guidelines and a number of free databases.
Airbase. The European air quality database system. It contains, next to multi-annual time series of measurement data and their statistics for a representative selection of stations throughout Europe
European Interpolated Air Quality Maps Annual European air quality maps for urban and rural background concentrations