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 2006 (Ratified) 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 1998 should be treated with caution due to the smaller number of monitoring locations.
Roadside and Kerbside NO2
In 2006 the calculation was based on 18 monitoring sites in 10 different conurbations. This will continue to increase as additional stations are added to the Scottish Air Quality Database in future years. Although the plot shows a trend downwards in average concentrations, this is mainly due to the fact that prior to 2001 Glasgow Kerbside was the only site available. The indicator only decreases significantly in 2001 and 2002 because of the inclusion of the Dumfries and Inverness sites, which have much lower concentrations than Glasgow Kerbside.
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.
Urban Background NO2
Again although the graph shows a downward trend the number of available monitoring sites for this analysis was very low in the early years (increasing to 7 sites in 2006).
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 2006 in Scotland is shown below:
It can be seen that on average the concentrations of ozone in rural areas appear to be showing a gradually increasing trend, perhaps related to the recent warm summers. In urban background areas the increase is much more dramatic as concentrations of total NOx are decreasing. Ozone in these areas is now much more similar to the rural concentrations which is of great concern for public exposure to this pollutant. PM10 Particulate concentrations show a decrease up until 2004, but then an apparent slight increase over the most recent years. As for NO2, these trends should be treated with caution up until 2001 due to the relatively small number of monitoring sites in Scotland.
