e-Digest Statistics about: Air Quality
The UK Sustainable Development Air Quality indicator
In 1999, an air quality indicator was introduced in support of the UK Sustainable Development Strategy . When this strategy was updated in 2005 in Securing the future [48] the opportunity was taken to introduce a new air quality indicator better reflecting the effects on health of long term exposure to lower levels of pollution.
Part A of the indicator shows trends for annual exposure to the two pollutants believed to have the greatest effect on human health, particles and ozone . It has been introduced because there is evidence that suggests long-term exposure to even low levels of particulate (PM10) may have a significant effect on public health. The annual mean values for particulates are a useful measure of overall exposure to particulates at all concentrations. The annual average measures of PM10 have been included to reflect this. The impact of long term exposure to low levels of ozone is currently less clear, but if there is no lower limit on the levels which have a health impact then the parameter used in the new indicator gives the best representation of the total annual impact of the short term effects of ozone pollution.
Part A shows levels of particles and ozone for urban, and either rural or roadside sites. Annual average particulate levels have been decreasing since 1993 although the trend may be levelling off. Roadside concentrations tend to be higher, because of the emissions from road vehicles, but show a similar downward trend. Both urban and roadside particulate levels have increased since 2005 and 2006. There has been an upward trend in background ozone levels, which is due to rising hemispheric ozone levels. There is a more marked increase in urban areas. We believe this is due to the reduction in urban emissions of nitrogen oxides (mainly from road transport), which destroy ozone close to their emission source.
Part B of the indicator shows episodes of moderate or higher levels of pollution but it does not pick up the contribution of long term exposure to lower levels of pollution. It is based on the banding system of the Governments' Air Pollution Information Service which classifies levels of five major air pollutants (ozone, PM10, sulphur dioxide, nitrogen dioxide and carbon monoxide) into bands of 'low/moderate/high/very high' pollution. These were chosen on the basis of effects on health and advice from the Department of Health's Committee on Medical Effects of Air Pollutants and reflect the increased risk of suffering health effects by vulnerable groups on specific days.
This indicator shows trends in the number of days per year when air pollution was moderate or higher for any of the five pollutants at urban and rural monitoring sites in the UK. The weather can cause significant variation from year to year in the number of days of moderate or higher air pollution. For example, the hot summer of 2003 was a major factor in the high figures for that year. 2007 has seen a cooler, wetter summer than previous years, so ozone and particle concentrations and episodes did not increase as much at this time of year as they had in some previous years.
Further Information:
- References:
- [48] Securing the Future - UK Government sustainable development strategy. HM Government (2005)
- Internet Links:
- UK National Air Quality Archive National Air Quality Standards
- UK National Air Quality Archive Air Pollution Information Service
- Defra: Air Quality policy web pages
- Defra: Air Quality Strategy for England, Scotland, Wales and Northern Ireland
- Department of Health Committee on the Medical Effects of Air Pollutants (COMEAP)
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Page last modified: 29 April 2008
Page published: 28 April 2005