This was published under the 2010 to 2015 Conservative and Liberal Democrat coalition government
This National Statistics release reports annual UK levels of pollution from particulates (PM10) and ozone (O3), the two pollutants thought to have the greatest health impacts, as well as the number of days on which levels of any one of five pollutants were ‘moderate or higher’. The release shows the historic increase in urban background ozone has levelled out, and is now at its lowest since 2001. Urban sites saw an average of eight pollution days, down from ten in 2009 and the lowest since records began in 1993. This followed a larger decrease in 2009, although there is no clear long-term trend. The drop is largely due to ozone.
Please see the release and accompanying spreadsheet here.