Rural Air Quality
Most people expect that air quality in the countryside should be better than air quality in town and cities. For the most part this is true, since emissions of primary pollutants, including particulates, nitrogen dioxide, carbon monoxide and volatile organic compounds, are significantly greater in urban areas. Levels of ozone, however, are generally higher in rural areas, by on average 20 to 40% because of its special atmospheric chemistry.
Ozone is a secondary photochemical pollutant, formed by the oxidation of other primary pollutants in the presence of sunlight Once formed, ozone is scavenged by nitric oxide (NO), more abundant in urban areas as a result of traffic fumes. Consequently, ozone usually occurs in higher concentrations during summer than winter, and in rural rather than urban areas.
The National Automatic Rural Monitoring Network in the UK provides information on secondary (photochemical) pollution across the UK, most significantly ozone, and information on particulates, nitrogen dioxide and sulphur dioxide concentrations in rural areas. This information is used to fulfil the requirements of a European legislation on ozone as a basis for UK government policy-making decisions, for scientific research on health and ecosystem effects, and for public information.
There is some evidence of a decline in magnitude of peak ozone concentrations during the last decade although no general downward trends in either average concentrations or exceedences of standards and guidelines have yet been detected.