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Indicator Assessment
Air quality in Europe is slowly improving. However, between 2000 and 2014, a significant proportion of the urban population in the EU-28 was exposed to concentrations of certain air pollutants above the EU limit or target values. The numbers of people exposed were even higher in relation to the more stringent World Health Organization (WHO) air quality guideline values set for the protection of human health.
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 before that year are not considered representative of the overall air quality status. Since then, the monitoring coverage has improved and is now more representative of Europe’s air quality (NB: the newest EU Member State, Croatia, has not yet reported data on urban PM2.5 measurements). Between 2006 and 2014, 8 - 17 % of the EU-28's urban population is estimated to have been exposed to concentrations of PM2.5 in excess of the EU target value set for the protection of human health (Figure 1).
With respect to the more stringent WHO guideline value (Figure 2), a much larger proportion of the urban population (85 - 97 %) was exposed to concentrations above this threshold.
The time series are considered too short to draw any firm conclusion on changes over time, though values have been decreasing after the relative maximum in 2011.
Particulate Matter (PM10)
Before 2000, the number of PM10 monitoring stations in some areas of EU-28 was also low. Since 2000, coverage initially improved in the EU-15 Member States but from 2005 it has improved across the whole EU. Notwithstanding limitations in data coverage in the early 2000s, a significant proportion of the EU-28 urban population (16 - 42 %) was exposed to concentrations of PM10 in excess of the EU daily limit value set for the protection of human health between 2000 and 2014 (Figure 1). A slightly decreasing tendency can be observed throughout the whole period.
For the more stringent WHO guideline value (Figure 2), a higher proportion of the urban population (50 - 92 %) was exposed to concentrations above this threshold. Here, a decreasing tendency is also observed, as in the case of the EU limit value, until it reached 50 % in the most recent available year (2014). 2014 was the first year in which less than half of the urban population was exposed to concentrations exceeding the WHO guideline.
Ozone (O3)
Although reductions in European emissions of ozone precursors have led to lower peak concentrations of ozone, the current long term objective is frequently exceeded by more than 25 days. During the 2000-2014 period, between 8 % (in 2014) and 55 % (in 2003) of the urban population was exposed to concentrations above the long term objective for more than 25 days (Figure 1). In the last seven years, the proportion of the urban population exposed has not exceeded 20 % and reached a minimum of 8 % in 2014.
In relation to the more stringent WHO guideline (Figure 2), the proportion of the population exposed to concentrations above the guideline value is as high as 94 – 99 %, with no discernible change over time.
Nitrogen dioxide (NO2)
Between 2000 and 2014, the fraction of the urban population exposed to concentrations in excess of the EU limit value and the identical WHO guideline value gradually decreased to around 10 %, with a minimum of 7 % in 2014 (Figures 1 and 2). At 31 %, the highest proportion of the urban population exposed occurred in 2003.
Benzo[a]pyrene (BaP)
There are relatively few reported measurements of BaP and these were not considered to be homogeneous across Europe until 2008. Considering data reported after that year, the fraction of the urban population exposed to concentrations above the BaP target value has shown little variation within the range of 17 - 24 %.
When considering the estimated 'reference level' for BaP, the proportion of the population exposed is much higher (81 - 91 %) and almost constant over the period.
Sulfur dioxide (SO2)
The results for SO2 show that the proportion of the urban population exposed to concentrations above the daily EU limit value decreased between 2000 and 2014 to less than 0.1 % in the last four years (with a maximum of 3 % in 2006).
With respect to the WHO guideline, following a steady decrease from a maximum of 85 % in 2000, around 38 % of urban population was exposed to levels above this guideline value in 2014.
Note to Figures 1 and 2:
Different numbers of countries are included in the illustrated data sets over time.
Of the 18 Member States with PM2.5 data from 2006 or before, there are no data available for Ireland in 2006 and 2012; and for Greece in 2006 and 2014. The first year Cyprus, Estonia, Lithuania, Malta (no data in 2014) and Romania (no data in 2008) are included is 2007. For Latvia, the Netherlands and Slovenia, it is 2008; and for Luxembourg, 2009. Croatia is not included due to lack of data from urban and suburban stations for the whole period.
Of the 18 countries with PM10 data from 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, 2012, 2013 and 2014.
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 Latvia in 2000 and 2001; and for Lithuania in 2000, 2001 and 2002. The first year Ireland is included is 2002. For Luxembourg (no data in 2014) and Romania, it is 2004; for Malta, 2005 (no data in 2006, 2011 and 2014); and for Croatia, 2009 (no data in 2011).
Of the 25 countries with NO2 data from 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 is included is 2004. For Croatia it is 2006 (no data in 2007); and for Malta, 2007 (no data in 2008, 2009 and 2014).
Fine Particulate Matter (PM2.5)
Figure 3 shows the annual mean urban and suburban background concentrations for PM2.5. The available time series of measured data is considered too short to draw any firm conclusion on changes over time. In 2014, more than 90 % of (sub)urban background stations had registered values below the EU target value.
A total of 27 EU Member States have submitted information on PM2.5 concentrations at 'urban background' and 'sub-urban background' stations. Data for Croatia are not included, as no urban or sub-urban background monitoring stations are present in the Urban Audit cities areas.
Particulate Matter (PM10)
Figure 4 shows the 90.4 percentile of the urban and suburban background daily concentrations, which is related to the EU daily limit value. No clear tendency can be observed in the 2000-2014 period, though values have been decreasing since the relative maximum in 2011.
A total of 27 EU Member States have submitted information on PM10 concentrations at 'urban background' and 'suburban background' stations. Data for Croatia are not included, as no urban or suburban background monitoring stations are present in the Urban Audit cities.
Ozone (O3)
Figure 5 shows, for urban and suburban background stations, the 93.2 percentile of the maximum daily 8-hour mean value, which is related to the EU target value. No clear changes are observed over the 2000-2014 period.
A total of 26 EU Member States have submitted information on ozone concentrations at 'urban background' and 'suburban background' stations. Data for Croatia and Cyprus are not included, as no urban or suburban background monitoring stations are present in the Urban Audit cities.
Nitrogen dioxide (NO2)
Figure 6 shows a steady average decrease for NO2 urban and suburban background concentrations.
A total of 26 EU Member States have submitted information on nitrogen dioxide concentrations at 'urban background' and 'suburban background' stations. Data for Croatia and Cyprus are not included, as no urban or suburban background monitoring stations are present in the Urban Audit cities.
This indicator shows the fraction of the EU-28 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 and suburban background levels of PM2.5, PM10, O3 and NO2 at EU-28 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)
The following units are used in this indicator:
Concentration:
Urban population (POP): number of inhabitants in the 'core city' and, from 2016 on, 'greater city' of the Urban Audit cities represented by the urban stations taken into account in the calculations.
Percentage of the urban population.
This indicator is relevant for 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 Seventh EU Environment Action Programme (EU, 2013a) includes priority objectives that aim, among others, to protect, conserve and enhance the EU's natural capital, safeguard EU citizens from environment-related pressures and risks to health and well-being, and enhance the sustainability of EU cities.
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.
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:
WHO Air Quality Guidelines
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.
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' and, from 2016, the 'greater city' of the UA cities taking part in the calculations.
Initially, stations in the EEA air-quality database are spatially joined with UA core and, from 2016, greater 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', 'suburban traffic', 'urban background' and 'suburban 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 the population living closer than 100 metres from major roads have been taken from Appendix D (EC, 2006). These data have been divided by the total population figures for 2001 according to the Eurostat census (Eurostat, 2014a). For Croatia, Malta and the United Kingdom there are no data on the 2001 population in that census, so the totals in (EC, 2007) have been used. Furthermore, for Cyprus and Malta there are 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 EU-28 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 at least 75 % of valid data 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 valid data 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 µg/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 valid data 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 µg/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 µg/m3, i.e. above the DLV and P90.4 ≤ 50 µg/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 valid data 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 µg/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 µg/m3, i.e. exceedance of the long term objective on more than 25 days, and P93.2 ≤ 120 µg/m3, i.e. exceedance of the long term objective is less than 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 valid data 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 µg/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 valid data 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 ng/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.
Sulfur dioxide (SO2)
For each selected station that fulfills the valid data 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 µg/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 µg/m3, i.e. above the daily limit value and P99.2 ≤ 125 µg/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 valid data 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 µg/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 valid data 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 µg/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 valid data criteria, the daily maximum 8-hourly mean concentration series is calculated. When there is one value above 100 µg/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 µg/m3, i.e. above the air quality guideline, or all daily maximum 8-hourly mean values ≤ 100 µg/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 valid data 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 ng/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.
Sulfur dioxide (SO2)
For each selected station that fulfills the valid data criteria, the daily concentration series is calculated. When there is one value above 20 µg/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 µg/m3, i.e. above the air quality guideline, or all daily values ≤ 20 µg/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 and, from 2016, greater cities in a geographical information system in order to select those stations that fall within the boundaries of the cities included in the Urban Audit collection. The selected stations include station types classified as 'urban background' and 'suburban background'. These types of stations, not influenced by specific local emissions such as traffic or industry, are considered representative for the assessment of 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 at least 75 % of valid data 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.
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 have 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 was derived from the URAU2007 data set in the first two assessment versions.
For the countries with no data on the 2001 census in (Eurostat, 2014a), data in the publication (EC, 2007) have been used.
For countries with no data on the population living close to major roads, the European average value of 5 % has been used.
This indicator is thought to be representative of the total urban population in Europe as a whole, but only the 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 that are 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 because:
Traffic and background stations are unevenly distributed in countries and over Europe, which can introduce some bias when estimating the population exposed to traffic 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 city population density. Also, the population in cities is assumed to remain constant.
The air quality data are officially submitted by national authorities. It is expected that data have been validated by the national data supplier and they 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 representativeness of the selection of urban sites might introduce differences among countries and cities, reducing 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 and objective estimation for this purpose. So the calculated fraction of the population exposed to levels above the regulated thresholds may be biased because most stations are placed in locations where BaP concentrations are high.
It is assumed that people living closer than 100 metres from major roads are 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 considering urban population alone.
For references, please go to https://www.eea.europa.eu/data-and-maps/indicators/exceedance-of-air-quality-limit-3/assessment-2 or scan the QR code.
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