Exceedance of air quality limit values in urban areas

Indicator Assessment
Prod-ID: IND-34-en
Also known as: CSI 004
expired Created 03 Nov 2014 Published 13 Nov 2014 Last modified 26 Nov 2015, 04:55 PM
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In the period 2000-2012, a significant proportion of the urban population in the EU-28 was exposed to ambient concentrations of pollutants above the EU limit (LV) or target (TV) values for the protection of human health. The numbers of people exposed was even higher in relation to the more stringent World Health Organization (WHO) guidelines. The figures (minimum-maximum in the period) are: For PM 2.5 , 4-14 % for EU LV and 87-98 % for WHO guideline (for the period 2006-2012 only). For PM 10 , 21-41 % and 64-92 %,. For ozone, 14-58 % and 93-99 %. For NO 2 , 8-27 % in both cases. For B(a)P, 20-28 % and 85-89 % (for the period 2008-2012 only). Air quality has slowly improved over past years. Following the decreasing tendencies, in 2012 fewer people (urban population) were exposed to concentrations above the PM 10 EU LV and WHO guideline; the O 3 EU TV; the NO 2 EU LV and WHO guideline; and the SO 2 EU LV and WHO guideline values.   

Key messages

In the period 2000-2012, a significant proportion of the urban population in the EU-28 was exposed to ambient concentrations of pollutants above the EU limit (LV) or target (TV) values for the protection of human health. The numbers of people exposed was even higher in relation to the more stringent World Health Organization (WHO) guidelines. The figures (minimum-maximum in the period) are:

  • For PM2.5, 4-14 % for EU LV and 87-98 % for WHO guideline (for the period 2006-2012 only).
  • For PM10, 21-41 % and 64-92 %,.
  • For ozone, 14-58 % and 93-99 %.
  • For NO2, 8-27 % in both cases.
  • For B(a)P, 20-28 % and 85-89 % (for the period 2008-2012 only).

Air quality has slowly improved over past years. Following the decreasing tendencies, in 2012 fewer people (urban population) were exposed to concentrations above the PM10 EU LV and WHO guideline; the O3 EU TV; the NO2 EU LV and WHO guideline; and the SO2 EU LV and WHO guideline values. 

 

What percentage of the European urban population is exposed to pollutant concentrations above the regulated thresholds?

Urban population exposed to air pollutant concentrations above selected limit and target values

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Urban population exposed to air pollutant concentrations above WHO air quality guidelines

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Fine Particulate Matter (PM2.5)

Before 2006, the number of PM2.5 monitoring stations in certain areas of the EU-28 was low, meaning measurements are not considered representative of the overall air quality status. Since then, the monitoring coverage has improved (but noting that the newest EU Member State, Croatia, has not yet reported data on urban PM2.5 measurements). Assuming  the monitoring station coverage is now more representative of Europe’s air quality, 4 to 14 % of the urban population is estimated to have been exposed to concentrations of PM2.5 in excess of the EU limit value set for the protection of human health during the period 2006-2012 (Figure 1).

With respect to the more stringent WHO guideline (Figure 2), a much larger proportion of the urban population (87-98 %) was exposed to concentrations above this threshold.

The time series is considered too short to draw any firm conclusion on changes over time.


Particulate Matter (PM10)

Prior to 2000, the number of monitoring stations in some areas of EU-28 was low. Since 2000 the coverage has improved, firstly in the EU-15 and since 2005 across the whole EU. Notwithstanding limitations in data coverage in the early 2000´s, a significant proportion of the urban population (21-41 %) was exposed to concentrations of particulate matter in excess of the EU daily limit value set for the protection of human health during the period 2000-2012 (Figure 1). A slightly decreasing tendency can be observed throughout the whole period.

For the more stringent WHO guideline (Figure 2), it can be observed that a higher proportion of the urban population (64-92 %) was exposed to concentrations above this threshold. Here a decreasing tendency is also observed, as in the case of the EU LV, until reaching 64 % in the last available year (2012).


Ozone (O3)

Although reductions in European emissions of ozone precursors have led to lower peak concentrations of ozone, the current long term objective (LTO) is frequently exceeded more than 25 days. In 2012, 14 % of the urban population was exposed to concentrations above the LTO during more than 25 days (Figure 1).  This is the lowest value since 2000 and is clearly below the 58 % recorded in 2003, the highest on record. In the last five years the proportion of the urban population exposed has not exceeded 20 %.

In relation to the more stringent WHO guideline (Figure 2), where no exceedance is allowed, the proportion of the population exposed to concentrations above the guideline value is as high as 93 – 99 %, with no discernible change over time.


Nitrogen dioxide (NO2)

In the period 2000-2012, the fraction of urban population exposed to concentrations in excess of the EU LV and the identical WHO guideline gradually decreased to 8 % (Figures 1 and 2). The highest proportion of the urban population exposed, 27 %, occurred in 2003.


Benzo(a)pyrene (B(a)P)

There are relatively few reported measurements of B(a)P, and these are not considered as being homogeneous across Europe until 2008. Considering data reported since then, the fraction of urban population exposed to concentrations above the B(a)P TV has shown little variation within the range of 20-28 %.

When considering the WHO “indicative concentration” for B(a)P, the proportion of the population exposed is much higher (85-89 %) and almost constant over the period. 


Sulphur dioxide (SO2)

The results for SO2 show that the proportion of urban population exposed to concentrations above the daily EU LV decreased in the period 2000-2012 to reach 0 % in the last two years (with a maximum of 2 % in 2006).

With respect to the WHO guideline, following a steady decrease from the maximum 84 % in 2000, around 36 % of urban population was exposed in 2012 to levels above this guideline.

 

Note to Figures 1 and 2:

Out of the 17 MS with PM2.5 data starting in 2006 or before, there are no data available for Ireland in 2006 and 2012. The first year Cyprus, Estonia, Lithuania, Malta and Romania (no data in 2008) are included is 2007. For Greece (no data in 2010, 2011 and 2012), Latvia, the Netherlands and Slovenia, it is 2008; and for Luxembourg, 2009. Croatia is not included due to lack of data.

Out of the 18 countries with PM10 data in 2000 or before, there are no data available for Bulgaria and Hungary in 2002; for Ireland in 2000; and for Lithuania in 2000, 2001 and 2002. The first year Denmark, Estonia, France and Greece are included is 2001. For Slovenia, it is 2002; for Romania, 2003; for Latvia, 2004 (no data in 2006); and for Croatia (no data in 2007) and Luxembourg, 2006. Malta has only been included in 2005, 2009, 2010 and 2012.

Out of the 23 countries with O3 data in 2000 or before, there are no data available for Bulgaria in 2002; for Denmark in 2000; for Lithuania in 2000, 2001 and 2002; and for Luxembourg in 2000 and 2001. The first year Ireland is included is 2002. For Luxembourg and Romania, it is 2004; for Malta, 2005 (no data in 2006 and 2011); and for Croatia, 2009 (no data in 2011).

Out of the 24 countries with NO2 data in 2000 or before, there are no data available for Bulgaria in 2000 and 2002; for Cyprus in 2008; for Hungary in 2002; for Lithuania in 2000, 2001 and 2002; and for Slovenia in 2000 and 2001. The first year Luxembourg and Romania are included is 2004. For Croatia it is 2006 (no data in 2007). Malta has only been included in 2007, 2010, 2011 and 2012.

What progress is being made in bringing concentrations of air pollutants in urban areas below the limit values (for particulate matter and nitrogen dioxide) or the target values (for particulate matter and ozone) defined in air quality legislation?

Annual mean PM2.5 concentration observed at (sub)urban background stations

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Percentile 90.4 of the daily PM10 concentrations observed at (sub)urban background stations

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Percentile 93.2 of the maximum daily 8-hour mean ozone concentrations observed at (sub)urban background stations

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Annual mean NO2 concentration observed at (sub)urban background stations

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Fine Particulate Matter (PM2.5)

Figure 3 shows the annual mean background concentrations for PM2.5. The available time series of measurement data is considered too short to draw any firm conclusion on changes over time.

A total of 24 EU Member States have submitted information on PM2.5 concentrations at 'urban background' and 'sub-urban background' stations to AirBase. Data for Croatia, Greece, Lithuania and Malta is not included since no urban or sub-urban background monitoring stations are present in the Urban Audit cities.


Particulate Matter (PM10)

Figure 4 shows the 90.4 percentile of the background daily concentrations, which is related to the attainment of the daily limit value. No clear tendency can be observed in the period 2000-2012.

A total of 25 EU Member States have submitted information on PM10 concentrations at 'urban background' and 'sub-urban background' stations to AirBase. Data for Croatia, Greece and Malta is not included since no urban or sub-urban background monitoring stations are present in the Urban Audit cities.


Ozone (O3)

Figure 5 shows, for urban background stations, the 93.2 percentile of the maximum daily 8-hour mean value, which is related to the attainment of the target value. No clear changes are observed over the period 2000-2012.

A total of 24 EU Member States have submitted information on ozone concentrations at 'urban background' and 'sub-urban background' stations to AirBase. Data for Croatia, Cyprus, Greece and Malta is not included since no urban or sub-urban background monitoring stations are present in the Urban Audit cities.


Nitrogen dioxide (NO2)

Figure 6 shows a steady decrease, on average, for the NO2 urban background concentrations.

A total of 24 EU Member States have submitted information on nitrogen dioxide concentrations at 'urban background' and 'sub-urban background' stations to AirBase. Data for Croatia, Cyprus, Greece and Malta is not included since no urban or sub-urban background monitoring stations are present in the Urban Audit cities.

Indicator specification and metadata

Indicator definition

This indicator shows the fraction of the EU28 urban population that is potentially exposed to ambient air concentrations of certain pollutants (PM2.5, PM10, O3, NO2, SO2 and BaP) that are in excess of the EU limit or target values (EU, 2004, 2008) set for the protection of human health; and to concentrations of these pollutants in excess of the WHO Guidelines (WHO, 2000, 2006).

It also shows the evolution of urban background levels of PM2.5, PM10, O3 and NO2 at European level.

The indicator is based on measurements of air pollutants as reported under the Air Quality Directives (EU, 2004, 2008) and the Decisions on the exchange of information (EU, 1997, 2011)

Units

The following units are used in this indicator:

Concentration:

  • micrograms (mg) of pollutant per cubic metre for PM2.5, PM10, O3, NO2 and SO2.
  • Nanograms (ng) of pollutant per cubic metre for BaP.

 

Urban population (POP): number of inhabitants in the 'core city' of the Urban Audit cities represented by the urban stations taken into account in the calculations.

Percentage of the urban population.


Policy context and targets

Context description

This indicator is relevant for the current European air quality legislation related to the protection of human health in the Air Quality Directives 2004/107/EC and 2008/50/EC (EU, 2004, 2008).

It is related to the WHO Air Quality Guidelines (WHO, 2000, 2006) for protecting public health.

The EU Clean Air Policy Package, adopted by the European Commission on 18 December 2013, proposes in the Communication “A Clean Air Programme for Europe” (EU, 2013b) the short-term objective of achieving full compliance with existing legislation by 2020 at the latest; and the long-term objective of no exceedances of the WHO guideline levels for human health.

The Seventh EU Environment Action Programme (EU, 2013a) includes priority objectives that aim, among others, to protect, conserve and enhance the Union's natural capital, safeguard the Union's citizens from environment-related pressures and risks to health and wellbeing and enhance the sustainability of the Union's cities.

Targets

EU ambient air limit and target values, and the long term objective set by the Directives 2008/50/EC and 2004/107/EC for the protection of human health

  • A target value for PM2.5 of 25 microgram/m3 as an annual average. In force since 1 January 2010.
  • A limit value for PM2.5 of 25 microgram/m3 as an annual average, with a margin of tolerance of 20% on 11 June 2008, decreasing on the following 1 January and every 12 months thereafter by an equal annual percentage to reach 0% by 1 January 2015.
  • A limit value for PM10 of 50 microgram/m3 as a daily average, not to be exceeded more than 35 times in a calendar year. In force since 1 January 2005.
  • An additional limit value for PM10 of 40 microgram/m3 as an annual average. In force since 1 January 2005.
  • A long-term objective for ozone of 120 microgram/m3 as a maximum daily 8 hour mean within a calendar year (not to be exceeded any day). No attainment date specified.
  • A target value for ozone, equal to the long term objective, not to be exceeded more than 25 days in a calendar year, averaged over three years. It had to be met in 2010 (average 2010 to 2012).
  • A limit value of NO2 of 200 microgram/m3 as an hourly average, not to be exceeded more than 18 times in a calendar year. In force since 1 January 2010.
  • An additional limit value for NO2 of 40 microgram/m3 as an annual average. In force since 1 January 2010.
  • A limit value of SO2 of 350 microgram/m3 as an hourly average, not to be exceeded more than 24 times in a calendar year. In force since 1 January 2005.
    • An additional limit value for SO2 of 125 microgram/m3 as a daily average, not to be exceeded more than 3 times in a calendar year. In force since 1 January 2005.
    • A target value for benzo[a]pyrene of 1 nanogram/m3 as an annual average. It had to be met by 1 January 2013.

     

    Exceedance of air quality limit/target values occurs when the concentration of air pollutants exceeds these limit/target values. When there are multiple limit values, the indicator uses the most stringent case:

    • PM10: the daily limit value. In this case, instead of the number of exceedances, the 90.4 percentile is used. This percentile represents, in a complete series of 365 elements, the 36th highest value. If it is below or equal to 50 microgram/m3 it indicates that the PM10 daily limit value has not been exceeded;
    • O3: the target value. In this case, instead of the three year average, only one year values are considered; and instead of the number of exceedances, the 93.2 percentile is used. This percentile represents, in a complete series of 365 elements, the 26th highest value. If it is above or equal to 120 microgram/m3 it indicates that the long term objective has not been exceeded on more than 25 days;
    • NO2: the annual limit value;
    • SO2: the daily limit value. In this case, instead of the number of exceedances, the 99.2 percentile is used. This percentile represents, in a complete series of 365 elements, the 4th highest value. If it is below or equal to 125 microgram/m3 it indicates that the SO2 daily limit value has not been exceeded.

     

    WHO Air Quality Guidelines

    • Annual mean of PM2.5: 10 microgram/m3
    • 24-hour mean of PM2.5 (99th percentile of the annual daily series (3 days per year)): 25 microgram/m3
    • Annual mean of PM10: 20 microgram/m3
    • 24-hour mean of PM10 (99th percentile of the annual daily series (3 days per year)): 50 microgram/m3
    • Daily maximum 8-hour mean of ozone: 100 microgram/m3
    • Annual mean of NO2: 40 microgram/m3
    • 1-hour mean of NO2: 200 microgram/m3
    • 24-hour mean of SO2: 20 microgram/m3
    • 10-minute mean of SO2: 500 microgram/m3
    • BaP is used as indicator of the carcinogenic risk of PAHs in ambien air. Since the WHO has not defined an air quality guideline for BaP, a reference level was estimated assuming the WHO unit risk for lung cancer for PAH mixtures and an acceptable risk of additional lifetime cancer risk of 1/100 000. This estimated reference level (also called “indicative concentration” for the purposes of this indicator) is fixed at 0.12 nanogram/m3 (ETC/ACM, 2011).

     

    Exceedance of the WHO guidelines or the reference level occurs when the concentration of air pollutants exceeds the corresponding values. For PM, the annual average is suggested to take precedence over the 24-hour average since, at low levels, there is less concern about remaining episodic excursions. For NO2 the annual mean is taken; and for SO2 the 24-hour mean, so these values can be compared with the corresponding limit value used in EU legislation. 

    Related policy documents

    • Directive 2004/107/EC
      Directive 2004/107/EC of the European Parliament and of the Council of 15 December 2004 relating to arsenic, cadmium, mercury, nickel and polycyclic aromatic hydrocarbons in ambient air.
    • Directive 2008/50/EC, air quality
      Directive 2008/50/EC of the European Parliament and of the Council of 21 May 2008 on ambient air quality and cleaner air for Europe.

    Methodology

    Methodology for indicator calculation

    Urban population exposure

    Information on cities is obtained from the Urban Audit (UA) data (Eurostat, 2014c). UA data collection, maintained by Eurostat, provides information and comparable measurements on the different aspects of the quality of urban life in selected European cities. The urban population considered is the total number of people represented by any of the urban monitoring stations in the 'core city' of the UA cities taking part in the calculations.

    Initially, stations in the EEA air quality database are spatially joined with UA core cities in a Geographical Information System in order to select those stations that fall within the boundaries of the cities included in the UA collection. The selected stations include station types classified as 'urban traffic', 'sub-urban traffic', 'urban background' and 'sub-urban background'. Stations classified as 'industrial' are influenced by other local emissions and such environments are generally not representative for residential areas. The industrial stations are therefore not selected for the indicator calculations.

    According to a study for the European Commission by Entec UK Limited (EC, 2006) in Europe, on average, 5% of the city population lives closer than 100 metres from major roads and is therefore potentially exposed to concentrations measured at traffic stations. The remaining 95% of the city population is assumed to be exposed to urban and suburban background concentrations.

    These percentages vary from country to country. To calculate them, national data on population living closer than 100 metres from major roads has been taken from Appendix D (EC, 2006). It has been divided by the total population figures for 2001 according to the Eurostat census (Eurostat, 2014a). For Croatia, Malta and the United Kingdom there is no data on 2001 population in that census, so the totals in (EC, 2007) have been used. Furthermore, for Cyprus and Malta there is no data for people living close to roads in (EC, 2006), so for them, and also for Turkey, the average value of 5% was used.

    The final percentages for each country (also for the five non EU28 EEA member countries not considered in this indicator but in the air pollution country fact-sheets) are shown in the following table  

    Country (j)

    Percentage of population living close to major roads (Ptj)

    Percentage of population exposed to background concentrations (Pbj)

     

     

     

    Austria

    6.4

    93.6

    Belgium

    7.4

    92.6

    Bulgaria

    3.6

    96.4

    Croatia

    4.1

    95.9

    Cyprus

    5.0

    95.0

    Czech Republic

    4.5

    95.5

    Denmark

    6.6

    93.4

    Estonia

    2.8

    97.2

    Finland

    3.8

    96.2

    France

    4.2

    95.8

    Germany

    6.2

    93.8

    Greece

    4.0

    96.0

    Hungary

    4.7

    95.3

    Ireland

    4.9

    95.1

    Italy

    4.9

    95.1

    Latvia

    3.8

    96.2

    Lithuania

    2.3

    97.7

    Luxembourg

    9.1

    90.9

    Malta

    5.0

    95.0

    Netherlands

    6.4

    93.6

    Poland

    3.4

    96.6

    Portugal

    3.8

    96.2

    Romania

    2.4

    97.6

    Slovakia

    5.7

    94.3

    Slovenia

    4.9

    95.1

    Spain

    5.3

    94.7

    Sweden

    2.2

    97.8

    United Kingdom

    5.8

    94.2

     

     

     

    Iceland

    0.7

    99.3

    Liechtenstein

    2.5

    97.5

    Norway

    1.9

    98.1

    Switzerland

    5.0

    95.0

    Turkey

    5.0

    95.0

    For PM10, PM2.5, O3, NO2 and SO2 only stations with data time coverage of at least 75% per calendar year are used. That is, in the case of daily values, those having more than 274 valid daily values per calendar year (or 275 days in a leap year). And in the case of hourly values, having more than 6 570 valid hourly values per calendar year (or 6 588 hours in a leap year). For BaP, the minimum data time coverage accepted is 14% (51 days), according to the data quality objectives related to indicative measurements in the Directive 2004/107/EU (EU, 2004).

    For every year, each city (i) in country (j), and every pollutant, the total number of urban or suburban traffic stations (nit) and the total number of urban or suburban background stations (nib) are obtained. Ptj% of the total population of the city (Popi) is proportionally assigned to each of the traffic stations and Pbj% of Popi is proportionally assigned to each of the background stations. So, every traffic station has an allocated population equal to ((Ptj / 100) * Popi / nit) and every background station has an allocated population equal to ((Pbj /100) *Popi / nib).


    EU LIMIT AND TARGET VALUES

    Particulate matter (PM2.5)

    The annual mean concentration is calculated for each of the selected stations fulfilling the data coverage criteria.

    Depending on the mean concentration, each station (and its allocated population) is then classified uniquely in one of the two concentration classes (below or equal to the target value (25 microgram/m3), or above it).

    The percentage of the urban population allocated to these two concentration classes is calculated by dividing the population represented by the stations assigned to each concentration class by the sum of the population assigned to each station.

    Particulate matter (PM10)

    For each selected station that fulfils the data coverage criteria the 90.4 percentile (P90.4) of the daily mean concentration series is calculated. P90.4 represents, in a complete series of 365 elements, the 36th highest value. When P90.4 is below or equal to 50 microgram/m3, it indicates that the daily limit value (DLV) would not have been exceeded on more than 35 days.

    Depending on the value of P90.4, each station (and its allocated population) is then classified uniquely in one of the two concentration classes (P90.4 > 50 microgram/m3, i.e. above the DLV and P90.4 ≤ 50 microgram/m3, i.e. below the DLV).

    The percentage of the urban population allocated to these two concentration classes is calculated by dividing the population represented by the stations assigned to each individual concentration class by the sum of the population assigned to each station.

    Ozone (O3)

    For each selected station fulfilling the data coverage criteria, the 93.2 percentile (P93.2) of the daily maximum 8-hourly mean concentration series is calculated. P93.2 represents, in a complete series of 365 elements, the 26th highest value. When P93.2 is below or equal to 120 microgram/m3, it indicates that the long term objective would have not been exceeded on more than 25 days.

    Depending on the value of P93.2, each station (and its allocated population) is then classified uniquely in one of the two concentration classes (P93.2 > 120 microgram/m3, i.e. exceedance of the long term objective on more than 25 days, and P93.2 ≤ 120 microgram/m3, i.e. exceedance of the long term objective is less or equal to 25 days).

    The percentage of the urban population allocated to these two concentration classes is calculated by dividing the population represented by the stations assigned to each individual concentration class by the sum of the population assigned to each station.

    Nitrogen dioxide (NO2)

    The annual mean concentration is calculated for each of the selected stations that fulfills the data coverage criteria.

    Depending on the annual mean concentration, each station (and its allocated population) is then classified uniquely in one of the two concentration classes (below or equal to the limit value (40 microgram/m3), or above the limit value).

    The percentage of the urban population allocated to these two concentration classes is calculated by dividing the population represented by the stations assigned to each concentration class by the sum of the population assigned to each station.

    Benzo[a]pyrene (BaP)

    The annual mean concentration is calculated for each of the selected stations fulfilling the data coverage criteria.

    Depending on the mean concentration, each station (and its allocated population) is then classified uniquely in one of the two concentration classes (below or equal to the target value (1.0 nanogram/m3), or above the target value).

    The percentage of the urban population allocated to these two concentration classes is calculated by dividing the population represented by the stations assigned to each concentration class by the sum of the population assigned to each station.

    Sulphur dioxide (SO2)

    For each selected station that fulfills the data coverage criteria the 99.2 percentile (P99.2) of the daily mean concentration series is calculated. P99.2 represents, in a complete series of 365 elements, the 4th highest value. When P99.2 is below or equal to 125 microgram/m3, it indicates that the daily limit value would have not been exceeded on more than three days.

    Depending on the value of P99.2, each station (and its allocated population) is then classified uniquely in one of these two concentration classes (P99.2 > 125 microgram/m3, i.e. above the daily limit value and P99.2 ≤ 125 microgram/m3, i.e. below the daily limit value).

    The percentage of the urban population allocated to these two concentration classes is calculated by dividing the population represented by the stations assigned to each individual concentration class by the sum of the population assigned to each station.


    WHO GUIDELINES

    Particulate matter (PM2.5)

    The annual mean concentration is calculated for each of the selected stations fulfilling the data coverage criteria.

    Depending on the mean concentration, each station (and its allocated population) is then classified uniquely in one of the two concentration classes (below or equal to the WHO air quality guideline (10 microgram/m3), or above it).

    The percentage of the urban population allocated to these two concentration classes is calculated by dividing the population represented by the stations assigned to each concentration class by the sum of the population assigned to each station.

    Particulate matter (PM10)

    The annual mean concentration is calculated for each of the selected stations that fulfills the data coverage criteria.

    Depending on the annual mean concentration, each station (and its allocated population) is then classified uniquely in one of the two concentration classes (below or equal to the WHO air quality guideline (20 microgram/m3), or above it).

    The percentage of the urban population allocated to these two concentration classes is calculated by dividing the population represented by the stations assigned to each concentration class by the sum of the population assigned to each station.

    Ozone (O3)

    For each selected station fulfilling the data coverage criteria, the daily maximum 8-hourly mean concentration series is calculated. When there is one value above 100 microgram/m3, it indicates that the WHO air quality guideline has been exceeded.

    Each station (and its allocated population) is then classified uniquely in one of the two concentration classes (at least one daily maximum 8-hourly mean value > 100 microgram/m3, i.e. above the air quality guideline, or all daily maximum 8-hourly mean values ≤ 100 microgram/m3, i.e. below the air quality guideline).

    The percentage of the urban population allocated to these two concentration classes is calculated by dividing the population represented by the stations assigned to each individual concentration class by the sum of the population assigned to each station.

    Nitrogen dioxide (NO2)

    Since the WHO guideline is the same as the EU limit value, the procedure is the same as described above under “EU limit and target values”.

    Benzo[a]pyrene (BaP)

    The annual mean concentration is calculated for each of the selected stations fulfilling the data coverage criteria.

    Depending on the mean concentration, each station (and its allocated population) is then classified uniquely in one of the two concentration classes (below or equal to the indicative concentration or reference level (0.12 nanogram/m3), or above it).

    The percentage of the urban population allocated to these two concentration classes is calculated by dividing the population represented by the stations assigned to each concentration class by the sum of the population assigned to each station.

    Sulphur dioxide (SO2)

    For each selected station that fulfills the data coverage criteria, the daily concentration series is calculated. When there is one value above 20 microgram/m3, it indicates that the WHO air quality guideline has been exceeded.

    Each station (and its allocated population) is then classified uniquely in one of the two concentration classes (at least one daily value > 20 microgram/m3, i.e. above the air quality guideline, or all daily values ≤ 20 microgram/m3, i.e. below the air quality guideline).

    The percentage of the urban population allocated to both concentration classes is calculated by dividing the population represented by the stations assigned to each individual concentration class by the sum of the population assigned to each station.

     

    Urban background concentrations

    Stations in the EEA air quality database are spatially joined with the Urban Audit core cities in a Geographical Information System in order to select those stations which fall within the boundaries of the cities included in the Urban Audit collection. The selected stations include station types classified as 'urban background' and 'sub-urban background'. These types of stations, not influenced by specific local emissions such as traffic or industry, are considered representative to assess the change overtime of urban air concentrations. Traffic and industrial stations are not used for the calculation of this part of the indicator. Only stations with data time coverage of at least 75% per calendar year are used.

    Particulate matter (PM2.5)

    For all the urban and suburban background stations considered, the average of the annual mean series is obtained, together with the 10th and 90th percentiles.

    Particulate matter (PM10)

    For all the urban and suburban background stations considered, the average of the series of the annual P90.4 of the daily PM10 concentrations is obtained, together with the 10th and 90th percentiles.

    Ozone (O3)

    For all the urban and suburban background stations considered, the average of the series of the annual P93.2 of the maximum daily 8-hour mean O3 concentrations is obtained, together with the 10th and 90th percentiles .

    Nitrogen dioxide (NO2)

    For all the urban and suburban background stations considered, the average of the annual mean series is obtained, together with the 10th and 90th percentiles . 

    Methodology for gap filling

    No gap filling is applied in the air quality data in the EEA air quality database.

    For countries with no information on cities and/or population in the Urban Audit data collection (Lichtenstein and Turkey), population data has been retrieved from http://www.citypopulation.de/. The gap filled mapping was done using the “station_city” attribute found in the EEA air quality database (AirBase) and compared with the city names found at http://www.citypopulation.de/. The London geometry is derived from the URAU2007 data set (all the others cities are derived from the UARU2012 data set, where “London” does not exist).

    For the countries with no data on the 2001 census in (Eurostat, 2014a), data in the publication (EC, 2007) has been used.

    For countries with no data on population living closed to major roads, the European average value of 5% has been used.

    Methodology references

    • ETC/ACC, 2009 - Indicators on urban air quality. A review of current methodologies. ETC/ACC Technical paper 2009/8

    Uncertainties

    Methodology uncertainty

    This indicator is thought to be representative of the total urban population in Europe as a whole, but only the urban population in the Urban Audit cities collection is covered. So, populations living in smaller towns and villages are not included.

    Only measurements from urban and suburban stations falling in the Urban Audit geometries are considered in the calculations. On one hand, this may lead to an incomplete assignment of stations. On the other hand, the representativeness of each station is not taken into account, instead in every city it is assumed that all stations of the same type have the same population representativeness.  

    Locally, the indicator is subject to year-to-year variations due to:

    • the fact that only two categories are described: below or above the environmental objective. A slight decrease (increase) in concentrations can make a station change its status and all the population associated to it from above to below (below to above) the corresponding objective. 
    • meteorological variability. When averaging over EU28 this meteorologically induced variation decreases in importance provided spatial data coverage is sufficient;
    • the number of available data series (monitoring stations and/or selected cities) that will influence the total number of monitored population; and
    • the geographical coverage of stations, determined also by the inclusion of new countries along the years. So variations over time might be influenced by changes in coverage.


    Traffic and background stations are unevenly distributed in countries and over Europe, which can introduce some bias when estimating the traffic-exposed population in the different countries.

    It has been assumed that all cities in a country have the same percentage of people living in traffic and background environments, which may lead to the underestimation of the population exposed to traffic concentrations in big and compact cities with a high population density.

    The percentages of people exposed to either traffic or background concentrations are assumed to remain constant, independently of possible urban developments and changes in cities population density. Also, the population in the cities is assumed to remain constant.

    Data sets uncertainty

    The air quality data is officially submitted by the national authorities. It is expected that data has been validated by the national data supplier and it should be in compliance with the data quality objectives as described in the Air Quality Directives (EU, 2004, 2008). There are different methods in use for the routine monitoring of pollutants.

    Station characteristics and representativeness are, in some cases, insufficiently documented. Also, the differences in the interpretation of the station characteristics and the the representativeness of the selection of urban sites might introduce differences among countries and cities, reducing the comparability between cities.

    For BaP, data may be influenced by the fact that cities where concentrations are below the lower assessment threshold do not need to take measurements to assess the air quality in relation to BaP, and they can use models for this purpose. So the calculated fraction of the population exposed to levels above the regulated thresholds may be biased because most of stations are placed in locations where the BaP concentrations are high.

    Rationale uncertainty

    It is assumed that people living closer than 100 metres from major roads are the ones potentially exposed to traffic concentrations, without taking into account the decline in concentrations as distance to the road axis increases or the fact that people may live and work in different places.

    It is assumed that the percentage of the total population living close to major roads (data in EC, 2006) is the same when it comes to urban population alone.

    Data sources

    Generic metadata

    Topics:

    Air pollution Air pollution (Primary topic)

    Tags:
    air quality | pm10 | soer2015 | quality of life | air | ozone | pm2.5 | health | air pollution | no2 | soer2015 european
    DPSIR: State
    Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)
    Indicator codes
    • CSI 004
    Dynamic
    Temporal coverage:
    2000-2012
    Geographic coverage:
    Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, United Kingdom

    Contacts and ownership

    EEA Contact Info

    Alberto Gonzalez Ortiz

    EEA Management Plan

    2014 1.1.2 (note: EEA internal system)

    Dates

    Frequency of updates

    Updates are scheduled once per year

    Related content

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