Energy Indicators for Sustainable Development: Guidelines and Methodologies International Atomic Energy Agency United Nations Department of Economic and Social Affairs International Energy Agency Eurostat European Environment Agency

(b) Measuring Methods: Suitable air monitoring networks must fulfil several 
requirements, such as ensuring representative and comparable measurements, 
detection limits, interferences, time resolution, ease of operation and cost. There are 
numerous references on air monitoring and analysis in the literature or available from 
environmental agencies. The published scientific literature on the subject includes the 
most appropriate and recent air monitoring methods. Air quality data can be highly 
dependent on weather conditions, which can give rise to relatively large year-to-year 
variations. Time-trend data used for the indicator should therefore incorporate as long 
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Possible ways to avoid this problem include a method developed by the European Environment 
Agency (EEA) that counts the fraction of available stations recording exceedances and then uses a 
population-weighted average to calculate urban, national and regional averages. An approach 
similar to this is recommended (for more information on this methodology, see www.eea.eu.int). 

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a time frame as possible so that long-term trends can be properly assessed. 
Measurements for compliance purposes (i.e. the comparison of concentrations with air 
quality standards) should not just be limited to urban areas, as limit values should not 
be exceeded anywhere. Concerning exposure and health considerations, urban areas 
combine a large fraction of the population and elevated concentrations; nevertheless, 
rural areas should not be excluded from a measuring network. In the case of ozone, 
for example, rural concentrations can be high downwind of large emission point 
sources. A number of models are available for estimating ambient concentrations of 
air pollutants, most of which are based on the Gaussian air dispersion model.