Air quality indicator for sustainable development 2008 final results The air quality indicator is one of the 68 indicators of the Government’s Sustainable Development Strategy. It measures annual 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 a basket of five pollutants were ‘moderate or higher’. Headline results Urban background particulate levels averaged 19 micrograms per cubic metre (µg  m-3) in 2008 compared to 22 µg m-3 in 2007. These levels have fluctuated in recent years, although there has been an overall decreasing trend since 1993, the first year for which data were available. Roadside particulate levels averaged 26 µg m-3 in 2008 compared to 27 µg m-3 in 2007. There has been a general downward trend since the series began in 1997, although this decline has slowed since 2001 and has been subject to increased fluctuation. Urban background ozone levels averaged 59 µg m-3 in 2008 compared to 57 µg m-3 in 2007 and 44 µg m-3 in 1992. These levels have shown an overall increasing long term trend since 1992, the first year for which data were available. Rural ozone levels* averaged 71 µg m-3 in 2008 compared to 68 µg m-3 in 2007 and 59 µg m-3 in 1987. There is no clear long term trend. In urban areas, air pollution in 2008 was recorded as moderate or higher on 26 days on average per site, compared with 23 days in 2007, and 59 days in 1993. This series has shown a high degree of year-on-year variability.   In rural areas, air pollution in 2008 was moderate or higher for 45 days on average per site, compared with 30 days  in 2007. This series has also fluctuated significantly over time. These results are an update of those published on 29th January following  the full quality control (ratification) process. The differences are minimal, the largest being a decrease in the number of days of moderate or higher pollution in rural sites from 47 days to 45 days, and a decrease in the annual average level of roadside PM10 from 28 µg m-3 to 26 µg m-3. There have also been some minor revisions to historical data since the provisional figures. * Measured as the daily maximum 8-hour running mean