1. Topic

2. Introduction

The first Daughter Directive (1999/30/EC) obliges Member States to ensure that up-to-date information on ambient concentrations of air pollutants is routinely made available to the public, by means, for example, of broadcast media, press, information screens or computer-network services. Information on ambient concentrations should be updated on a daily or hourly basis depending on the pollutant. Such information shall, at least, indicate any exceeding of the concentrations in the limit values and alert thresholds over the corresponding averaging periods. It should also provide a short assessment in relation to limit values and alert thresholds and appropriate information regarding effects on health. Air quality indicators and indices could be used for the Directive’s purpose to make the information made available to the public clear, comprehensible and accessible. The European Environmental Agency (EEA)’s definition of “indicator” is “an observed value representative of a phenomenon to study. In general, indicators quantify information by aggregating different and multiple data. The resulting information is therefore synthesised. In short, indicators simplify information that can help to reveal complex phenomenon”. Air quality indicators are parameters, or values derived from parameters, describing the driving forces and the pressures on the atmospheric environment, its state and its impact on human beings, ecosystems and materials and the responses steering that system. An indicator has gone through a selection and/or aggregation process to enable it to steer action.

“Index” usually means a composite indicator, where several compounds are seen together, and their levels (relative to limit values, or to WHO thresholds, etc.) are combined into one number, to synthesise the information to be reported to the public.

3. Discussion

Air quality indicators are used to report on the state of outdoor air quality and its potential effects on human health and the environment, how air quality is changing over time (e.g. trends in lead levels following the introduction of unleaded petrol), the difference between air quality in different areas, the factors influencing those differences and whether the policies adopted are improving air quality. The European Topic Centre on Air and Climate Change (ETC-ACC) has currently developed and used a huge set of indicators/sub-indicators for air pollution related issues. These indicators have been compiled over the past years for specific reports and fact sheets but are increasingly linked and harmonised. This core set of indicators will form part of a wider set of indicators that will be used, within EEA reports and services, to inform policy makers and the public on key European environmental problems. There are four types of indicators (analysis of the indicators can be found in detailed fact sheets on the EEA’s web site, see below). Pressure indicators are quantifying the stresses in the form of direct pressures, such as air emissions; state indicators describe the environmental conditions of ambient air; impact indicators are identifying and quantifying the changes in the ecosystems and human health, based on the conditions of the atmospheric environment; and response indicators describe the actions taken to improve the quality of the atmospheric environment. Following ETC-ACC’s guidelines, the core set-pressure indicators are: emissions of acidifying pollutants; emissions of ozone precursors; emissions of primary and secondary PM₁₀, emissions of SO₂, NO_X, NMVOC, NH₃, heavy metals and persistent organic pollutants (total and by sector). The core set-state indicators are: exceedance of critical load for total acidity and nutrients; exposure of agricultural crops and forests to ozone; exceedance of health- related limited values for “FWD” pollutants in urban areas (O₃, PM₁₀, NO₂/NO_X, SO₂, CO, benzene and Pb).

Air quality index is a scale usually developed by the national authority to measure how much pollution is in the air and for reporting daily air quality. It tells you how clean or polluted your air is, and what associated health concerns you should be aware of. Usually, an air quality index focuses on health effects that can happen within a few hours or days after breathing polluted air for the major air pollutants regulated by the legislation. Air quality data are derived from monitoring stations and “translated” in the specific index’s scale. A specific colour must be assigned to each air quality category, delimited by values of concentration corresponding to “legislative” limit values, or health effects-associated levels, etc. One of the most important examples of air quality index is the U.S. Environmental Protection Agency’s “AQI”, where the red colour means “unhealthy” conditions, while the purple colour means “very unhealthy” conditions. This colour scheme can help to quickly determine if air pollutants are reaching unhealthy levels in the urban area and in its surroundings.

4. Recommendation / Conclusion

· While air quality indicators help summarising a huge amount of information, deriving from emission data, measures of pollutants, etc. into the so-called DPSIR assessment framework (Driving forces, Pressures, State of the environment, Impacts, and societal Responses) that covers the most important aspects of the socio-economic and environment framework, air quality indices are in general used to describe the “present” (daily or even hourly) state of air quality, giving to the public an updated and more comprehensible information on the state of air quality in urban areas (and not only).

· In the urban “perspective” air quality indicators can be useful tools in air quality assessment, to describe the importance of pressures on urban air quality and to derive the trend of air pollution over time. Air quality indices can help communicating air quality-related information to the public, as well as to environmental organisations, consumer organisations, organisations representing the interests of sensitive populations and other relevant health-care bodies.

5. Examples / Further Reading

Air quality index review in some European and USA

Air Quality Index - UK

Further Examples:

6. Additional Documents / Web Links

Background references on Air Quality Indicators

· ETC/ACC and EEA’s indicators (fact sheets included): http://ims.eionet.eu.int/Topics/AP/indicators/

· WHO/EEA Health Related Indicators of Air Quality: http://org.eea.eu.int/documents/berlin/index.html

Background references on Air Quality Indices

· U.S. Environmental Protection Agency, Air Quality Index (AQI): http://www.epa.gov/airnow/aqibroch/

Examples of Air Quality Indicators

· Air quality Indicators in the City of Stockholm (S): http://www.slb.mf.stockholm.se/

Examples of Air Quality Indices

· Air pollution index in London (UK): http://www.erg.kcl.ac.uk/london/asp/PublicHome.asp?

· Air quality index in Paris (F), ATMO: http://www.airparif.asso.fr/english/indices/atmo.htm

· European Project EMMA (Integrated Environmental Monitoring, Forecasting and Warning Systems in Metropolitan Areas): http://vaxc.middlesex.ac.uk/emma/index.html

Last Updated

25th January 2005