The Headline Air Quality Indicator - Trends
Part of the Government's plans to ensure a better quality of life are Indicators of Sustainable Development. Below we present a series of graphs which have been calculated based on the latest figures up to 2008 (provisional) for Air Quality in Scotland.
Annual Mean trends for Nitrogen Dioxide
Plots for annual mean trends for NO2 at Roadside+Kerbside and background sites are presented and discussed below:
This graph shows a long-term decline in nitrogen dioxide concentrations in urban areas. Data prior to 2001 should be treated with caution due to the smaller number of monitoring locations.
Roadside and Kerbside NO2
In 2008 the calculation was based on 41 monitoring sites in 28 different urban areas. This coverage has increased rapidly in the last two years and will continue to do so as further monitoring stations are added to the Scottish Air Quality Database.
As the number of sites available increases, the indicator will become much less dependent on the inclusion (or exclusion) of any particular site and hence will become more robust.
2008 provisionally recorded the lowest annual mean NO2 concentration to-date, and for the first time the average across all the roadside and kerbside stations was below the annual mean objective of 40 µg/m3 (although it was not achieved at all locations).
Urban Background NO2
In 2008 the calculation was based on 9 monitoring sites in 7 different urban areas. These are relatively small numbers since most of the recent increases in NO2 monitoring station numbers across Scotland has been focussed on roadside or kerbside locations rather than at background. This is because most background locations already meet the 40 µg/m3 air quality objective.
Within the data set there is a clear downward trend with a provisional 2008 average NO2 concentration of 27 µg/m3 across all the background stations.
Ozone and PM10 Particulate Matter Trends
When the UK Air Quality Strategy was updated in 2005 a new air quality indicator was added, better reflecting the effects on health of long term exposure to lower levels of pollution. This focussed on annual trends for the pollutants PM10 and Ozone.
The provisional trend for this indicator to 2008 in Scotland is shown below:
It can be seen that on average the concentrations of ozone appear to be showing a gradually increasing trend, probably related to increasing northern hemisphere background ozone, and decreasing NOx concentrations in urban background areas in recent years. Ozone in urban background areas has now increased to very similar levels to rural concentrations, raising further concerns over public exposure to this pollutant. PM10 Particulate Matter concentrations show a steady decrease at urban background locations, but are more variable at roadside+kerbside locations. These trends are based on 8 monitoring stations in in 7 urban areas at background locations, and 38 monitoring stations in 25 urban areas at roadside+kerbside locations. The mean PM10 concenrtation was provisionally 17 µg/m3 at background locations in 2008, and 22 µg/m3 at roadside+kerbside locations. The average background level was below the Scottish Government objective of 18 µg/m3 for the first time in 2008, although it was not achieved at all locations. As for NO2, the PM10 trends should be treated with caution before 2001 due to the relatively small number of monitoring sites in Scotland.
