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You are here: Home / Data and maps / Indicators / Exceedance of air quality limit values in urban areas / Exceedance of air quality limit values in urban areas (CSI 004) - Assessment published Dec 2009

Exceedance of air quality limit values in urban areas (CSI 004) - Assessment published Dec 2009

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Generic metadata

Topics:

Air pollution Air pollution (Primary topic)

Tags:
csi | pm10 | air pollution | air | ozone | so2 | air quality | no2
DPSIR: State
Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)
Indicator codes
  • CSI 004
Dynamic
Temporal coverage:
1997-2007
 
Contents
 

Key policy question: What progress is being made in reducing concentrations of air pollutants in urban areas to below the limit values (for sulphur dioxide, nitrogen dioxide and particulate matter) or the target values (for ozone) defined in air quality legislation?

Key messages

  • Particulate Matter (PM10)

In the period 1997-2007, 20-50 % of the urban population was potentially exposed to ambient air concentrations of particulate matter (PM10) in excess of the EU limit value set for the protection of human health (50 microgram/m3 daily mean not be exceeded more than 35 days a calendar year). There was no discernible trend over the period (Figure 1).

  • Nitrogen dioxide (NO2)

In the period 1997-2007, 13-41 % of the urban population was potentially exposed to ambient air nitrogen dioxide (NO2) concentrations above the EU limit value set for the protection of human health (40 microgram NO2/m3 annual mean). There was a slight downwards trend over the period (Figure 1).

  • Ozone (O3)

In the period 1997-2007, 14-62 % of the urban population in Europe was exposed to ambient ozone concentrations exceeding the EU target value set for the protection of human health (120 microgram O3/m3 daily maximum 8-hourly average, not to be exceeded more than 25 times a calendar year by 2010). The 62 % of the urban population exposed to ambient ozone concentrations over the EU target value was recorded in 2003, which was the record year. There was no discernible trend over the period (Figure 1).

  • Sulphur dioxide (SO2)

In the period 1997-2007, the fraction of the urban population in EEA-32 member countries that is potentially exposed to ambient air concentrations of sulphur dioxide in excess of the EU limit value set for the protection of human health (125 microgram SO2/m3 daily mean not to be exceeded more than three days a year), decreased to less than 1%, and as such the EU limit value set is close to being met everywhere in the urban background (Figure 1).

Percentage of urban population resident in areas where pollutant concentrations are higher than selected limit/target values, EEA member countries, 1997-2007

Note: The rationale for selection of pollutant and corresponding limit/target values for CSI 004 is given in the justification for indicator selection. Only urban and sub-urban background monitoring stations have been included in the calculations.

Data source:
Downloads and more info

Percentage of population resident in urban areas potentially exposed to PM10 concentration levels exceeding the daily limit value, EEA member countries, 1997-2007

Note: The limit value is 50 µg PM10/m3 (24 hour average, i.e. daily), not to be exceeded more than 35 times a calendar year. Over the years 1997-2007 the total population for which exposure estimates are made, increases from 25 to 109 million people due to an increasing number of monitoring stations reporting air quality data under the Exchange of Information Decision.

Data source:
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36th highest 24-hour mean PM10 concentration observed at urban background stations, EEA member countries, 1997-2007

Note: Only urban and sub-urban background monitoring stations have been included in the calculations.

Data source:
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Percentage of population resident in urban areas potentially exposed to NO2 concentration levels exceeding the annual limit value, EEA member countries, 1997-2007

Note: The annual mean limit value is 40 µg NO2/m3. Over the years 1997-2007 the total population, for which exposure estimates are made, increased from 54 to 113 million people due to an increasing number of monitoring stations reporting air quality data under the Exchange of Information Decision.

Data source:
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Annual mean NO2 concentration observed at urban background stations, EEA member countries, 1997-2007

Note: Only urban and sub-urban background monitoring stations have been included in the calculations.

Data source:
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Percentage of population resident in urban areas potentially exposed to O3 concentration levels over the long-term objective for protection of human health, EEA member countries, 1997-2007

Note: The target value is 120 µg O3/m3 as daily maximum of 8 hour mean, not to be exceeded more than 25 days per calendar year, averaged over three years. Over the years 1997-2006 the total population for which exposure estimates are made, increases from 48 to 112 million people due to an increasing number of monitoring stations reporting under the Exchange of Information Decision.

Data source:
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26th highest maximum daily 8-hour mean ozone concentration observed at urban background stations, EEA member countries, 1997-2007

Note: Only urban and sub-urban background monitoring stations have been included in the calculations.

Data source:
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Percentage of population resident in urban areas potentially exposed to SO2 concentration levels exceeding the daily limit value, EEA member countries, 1997-2007

Note: The limit value is 125 µg SO2/m3 as a daily mean, not to be exceeded more than three days in a year. Over the years 1997-2007 the total population for which exposure estimates are made, increases from 56 to 101 million people due to an increasing number of monitoring stations reporting under the Exchange of Information Decision.

Data source:
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4th highest 24-hour mean SO2 concentration observed at urban stations, EEA member countries, 1997-2007

Note: Only urban and sub-urban background monitoring stations have been included in the calculations.

Data source:
Downloads and more info

Key assessment

  • Particulate Matter (PM10)

PM10 in the atmosphere can result from direct emissions (primary PM10) or emissions of particulate precursors (nitrogen oxides, sulphur dioxide, ammonia and organic compounds) which are partly transformed into particles by chemical reactions in the atmosphere (secondary PM10).

For the period 1997-2007, the number of monitoring stations in some areas of Europe was relatively small and results may not be representative for all parts of Europe (Buijsman et al., 2004). Notwithstanding these limitations, it is clear that a significant proportion of the urban population (20-50 %) was exposed to concentrations of particulate matter in excess of the EU limit values set for the protection of human health (Figure 2).

The observed time series is short and the natural meteorological variability is large therefore it is not possible to draw firm conclusions on a possible trend in the data. Preliminary analyses indicate a downward change in the highest daily mean PM10 values although for the majority of stations the observed change is statistically not significant. In Figure 3, the 36th highest daily average is shown; compliance with the short-term limit value is assured when this value is below 50 microgram/m3.

Emissions of the gaseous precursors for secondary PM are being reduced by enforcement of EU legislation (e.g. NEC Directive) and UNECE LRTAP Convention protocols (United Nations Economic Commission for Europe, Convention on Long-range Transboundary Air Pollution). Abatement techniques to reduce precursor emissions often also reduce the primary particulate emissions. Other measures (e.g. traffic measures from Auto-Oil-I and II Programme, waste incineration directive, road traffic introduction of EURO standards and IPPC) should further reduce PM10 emissions.

Despite the likely future reductions in emissions, PM10 concentrations are expected to remain well above the daily limit values in most of the urban areas in the near future.

  • Nitrogen dioxide (NO2)

The main source of nitrogen oxides emissions to the air is the use of fossil fuels; road transport, power plants and industrial boilers account for more than 95% of European emissions.

In the period 1997-2007, 14-41 % of the urban population lives in cities with urban background concentrations in excess of the 40 microgram NO2/m3 limit value (Figure 4). However, it is expected that also in cities where the urban background concentration is below the limit value, limit values are exceeded at hot spots, in particular in locations with high density of traffic.

Enforcement of current EU legislation (Large Combustion Plant and IPPC Directive, Auto-Oil programme, the National Emissions Ceilings Directive (NECD) and LRTAP Convention protocols) have resulted in a reduction of nitrogen oxides (NOx) emissions. Until now this reduction has not been fully reflected in the annual averages of NOx concentrations observed at the urban background stations. Figure 5 shows a prevailingly decreasing trend.

Peak nitrogen dioxide levels occur often in busy streets in cities where road traffic is the main source. Since the introduction of catalytic converters at the end of the 1980s, their growing penetration in the car fleet and other measures have contributed to reducing emissions (-25 % since 1980 in the EU-15) [1]. The result has been a downward trend in the number of exceedances of the hourly limit value [2]. Peak levels depend on meteorological conditions; year-to-year fluctuations are 10 to 20 % or more.

In total 25 of the EEA member countries which are included in the Urban Audit have submitted information on nitrogen dioxide concentrations at 'urban background' and 'sub-urban background' stations to the air quality database 'AirBase'.

[1] http://www.ceip.at/

[2] http://reports.eea.europa.eu/eea_report_2007_2/en

  • Ozone (O3)

Although reductions in emissions of ozone precursors appear to have led to lower peak concentrations of ozone in the troposphere, the current target level is frequently exceeded for a substantial part of the urban population of the EEA member countries. Figure 6 shows estimates for 2007, indicating that 90 % of the urban population experienced exceedance of the 120 microgram O3/m3 level during at least one day (the long-term objective for protection of human health), while about 19 % of the urban population was exposed to concentrations above the 120 microgram O3/m3 level during more than 25 days. The target level was exceeded over a wide area (and much more than just 25 days).

Several studies have shown that ozone peak values have tended to decrease during the first half of the nineties. However, the officially reported data (available in AirBase) for a consistent set of stations over the period 1996-2001 shows hardly any variation for the 26th highest daily maximum 8-hour average. Figure 7 shows this 26th highest value; if it drops below 120 microgram O3/m3, there is compliance with the target value. Furthermore, the annual mean ozone concentrations have increased, which is in agreement with several studies.

The reductions in ozone precursor emissions that should result from enforcement of the NEC Directive and the LRTAP Convention protocols are unlikely to reduce ozone concentrations to below the current target value and long-term objective over the whole of the EEA area.

  • Sulphur dioxide (SO2)

Sulphur in coal and oil and in mineral ores is the main source of sulphur dioxide in the atmosphere. Up to 1960s, coal and oil combustion in large and small sources was the typical situation in many European cities, resulting in very high sulphur dioxide and PM concentrations. Since then, the combustion of sulphur-containing fuels have largely been removed from urban and other populated areas, first in western Europe and now also increasingly in most central and eastern European countries. Large point sources (power plants and industries), remain the predominate source of sulphur emissions. These sources, usually with high stacks, are most often located away from population centres.

As a result of the important reductions in sulphur dioxide emissions achieved in the last decades, the fraction of the urban population exposed to concentrations above the EU limit value has been reduced to less than 1 % (Figure 8). The reduction in sulphur dioxide peak concentrations is more clearly seen in the trend of the 4th highest daily sulphur dioxide concentration on urban stations in the period 1997-2007 (Figure 9). Compliance with the limit value for the daily mean is assured when the 4th highest concentration is below 125 microgram SO2/m3. A further decline in concentrations is expected in the coming years. However, peak concentrations above EU limit values still occur, especially close to sources and in cities. Peak levels strongly depend on meteorological conditions; year-to-year fluctuations are 10-20 % or more.

Several factors have contributed to the decrease in sulphur dioxide concentrations. The first (1985) and the second (1994) sulphur protocol under the UNECE LRTAP Convention, together with EC limit values set in the previous Air Quality Directive (89/427/EEC amending 80/779/EEC) have resulted in major European emission reductions and correspondingly decreasing ambient concentrations. Political changes in the beginning of 1990s in the central and eastern European countries connected with economic restructuring, decline of heavy industry and adoption of abatement measures on large point sources has contributed to decreasing winter smog episodes in central and western European countries. Policies and measures such as the Large Combustion Plants Directive, the IPPC Directive, standards regulating emissions from transport, the National Emission Ceilings Directive, and the reductions agreed under LRTAP Convention are expected to further reduce sulphur dioxide levels. Programmes for the reduction of sulphur emission from ships are also underway.

In total 22 of the EEA-32 member countries which are included in the Urban Audit have submitted information on sulphur dioxide concentrations at 'urban background' and 'sub-urban background' stations and the data is available in the air quality database AirBase. However, the majority of the information on sulphur dioxide concentrations results from stations in EU-15 Member States. The limit values tend to be more widely exceeded in the Central and Eastern European countries.

Data sources

More information about this indicator

See this indicator specification for more details.

Contacts and ownership

EEA Contact Info

Michel Houssiau

Ownership

EEA Management Plan

2010 (note: EEA internal system)

Dates

Frequency of updates

Updates are scheduled every 1 year in July-September (Q3)
Document Actions

Comments

European Environment Agency (EEA)
Kongens Nytorv 6
1050 Copenhagen K
Denmark
Phone: +45 3336 7100