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

(c) International Conventions and Agreements: There are several international 
conventions that focus on controlling air emissions as a means of improving air 
quality. Concern over emissions of acidifying pollutants has led to several 
international agreements, including the United Nations Economic Commission for 
Europe (UNECE) Convention on Long-range Transboundary Air Pollution 
(CLRTAP) (Geneva, 1979) and its protocols to reduce emissions of sulphur (Helsinki, 
1985; Oslo, 1994; Gothenburg, 1999) and nitrogen oxides (Sofia, 1988; Gothenburg, 
1999). Two other protocols have also been agreed upon that aim at reducing heavy 
metals (Aarhus, 1998) and non-methane volatile organic compounds (Geneva, 1991). 

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(d) International Targets/Recommended Standards: World Health Organization 
(WHO) air quality guidelines exist for all the pollutants covered by this indicator 
except nitrogen monoxide. Many countries have established their own air quality 
standards for many of these pollutants. 
(e) Linkages to Other Indicators: This indicator is closely linked to others that 
relate to energy use and environmental protection, such as annual energy use per 
capita and per unit of gross domestic product (GDP), air pollutant emissions from 
energy systems, share of non-carbon fuels and renewables, soil contamination, etc. 
METHODOLOGICAL DESCRIPTION 
(a) Underlying Definitions and Concepts: This indicator may be designed and 
constructed in a number of ways. An important aspect that must be considered is the 
definition of the statistic to be used; for example, where monitoring data are available, 
the indicator may be expressed in terms of a mean annual concentration, a percentile, 
or the nth highest daily mean, etc., on the basis of either an hourly or daily average. 
For health effects, the most appropriate averaging times and statistics are likely to be 
different for different pollutants. It is therefore recommended that the basis for the 
indicator be the number of days where concentrations exceed an established threshold 
(national or international air quality limits) and/or the percentage of the urban 
population exposed to concentration levels that exceed the target values (e.g. 
according to European Union legislation, 24-hour average PM10 concentrations 
above 50 
μg/m
3
are not to be exceeded more than 35 times a year). It should be noted 
that this type of comparison might need to be made with care because of possible 
changes or differences in guideline values. However, a simple count of the number of 
exceedances in a country is an inappropriate final measure for the indicator, as the 
number of exceedances is likely to increase with increasing numbers of monitoring 
stations.
1
Where monitoring data are unavailable, estimates of pollution levels may be made 
using air pollution models. Dispersion models, however, depend on the availability of 
emissions data; where these are not available, surveys may be conducted using rapid 
source inventory techniques. Because of the potential errors in the models or in the 
input data, results from dispersion models should ideally be validated against 
monitoring data.