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Indicator Assessment
Annual mean NO2 concentrations observed at traffic stations, 2014
Note: The figure shows the annual mean of nitrogen dioxide (NO2) observed at traffic stations in 2014.
Annual mean NO2 concentrations observed at background stations, 2014
Note: The figure shows the background concentrations of nitrogen dioxide (NO2) observed at background stations in 2014.
90.4 percentile of PM10 daily mean concentrations observed at traffic stations, 2014
Note: The map shows the 90.4 percentile of the PM10 daily mean concentrations, representing the 36th highest value in a complete series. It is related to the PM10 daily limit value, which allows 35 exceedances of the 50 µg/m3 threshold over a 1 year period. The red and dark-red dots indicate stations with concentrations above this daily limit value. Only stations with more than 75 % valid data have been included in the map.
90.4 percentile of PM10 daily concentrations at background stations, 2014
Note: The map shows the 90.4 percentile of the PM10 daily mean concentrations, representing the 36th highest value in a complete series. It is related to the PM10 daily limit value, which allows 35 exceedances of the 50 μg/m3 threshold over a 1 year period. The red and dark-red dots indicate stations with exceedances of this daily limit value. Only stations with more than 75 % valid data have been included in the map.
Annual mean PM2.5 concentrations observed at traffic stations, 2014
Note: The figure shows the annual mean concentrations of particulate matter (PM2.5) observed at traffic stations in 2014.
Annual mean PM2.5 concentrations observed at background stations, 2014
Note: The figure shows the annual mean concentrations of particulate matter (PM2.5) observed at background stations in 2014.
Air quality in urban areas is significantly influenced by local road traffic. While considerable progress has been made over the past twenty years in improving urban air quality, a number of issues remain. Despite considerable improvements, air pollution is still responsible for more than 467 000 premature deaths in Europe each year. It also continues to damage vegetation and ecosystems. Since the late 1990s, concentrations of nitrogen dioxide (NO2) and particulate matter (PM10) in urban areas have not declined in line with emission trends. Although emissions from transport have been declining, there are still many areas where limit values for NO2 and PM10 are exceeded across Europe, mainly due to road traffic.
For example, the annual EU limit value for NO2, one of the main air quality pollutants of concern and one typically associated with vehicle emissions, was widely exceeded across Europe in 2014, with 94 % of all exceedances occurring at road‑side monitoring locations. Also, in 2014, about 16 % of the EU‑28 urban population was exposed to PM10 levels above the EU daily limit value.
The disparity between trends in emission estimates and ground level concentrations of these pollutants can be partly explained by the difference between the laboratory and real‑world emission performances of vehicles. However, there are further specific features of traffic and the urban environment that add to this disparity. For example, an increase in NO2 emitted directly into the air from diesel vehicles (the proportion of NO2 in the nitrogen oxides (NOx) emissions of a diesel vehicle is far higher than the proportion of NO2 in the NOx emissions of a conventional-petrol vehicle) has been reported. Some cities in Europe recorded an increase in NO2 concentrations measured close to traffic, mainly because of the increasing number of diesel vehicles.
Moreover, vehicle composition in urban areas is generally different to national composition. Actions to improve air quality need to take account of local composition to ensure targeted measures are implemented. For example, buses, mopeds and motorcycles make up a higher proportion of vehicle composition in urban areas than they do nationally. Buses can emit high levels of NOx and PM unless measures are taken to ensure they meet strict emission standards. Mopeds and motorcycles are high emitters of carbon monoxide (CO) and volatile organic compounds (VOC), particularly older models.
In addition, 'slow, stop and start' congested urban traffic conditions and frequent short journeys can result in higher emissions per kilometre compared with free-flowing longer journeys. This is a consequence of increased cold engine operation, and the higher fuel consumption and less efficient performance of exhaust emission abatement systems. Measures to reduce traffic congestion may therefore also benefit air quality in the immediate area, although the full impacts need to be assessed over a wider area to ensure that traffic and emissions are not simply moved elsewhere.
Other characteristics of the urban environment can increase the impact of traffic emissions on air quality. For example, the presence of high buildings on either side of roads, common in many city centres, creates a 'street canyon', which reduces the dispersion of the pollutants emitted from traffic sources and can lead to significantly higher concentrations locally.
The monitoring data reported by the countries (Air Quality e-Reporting Database (http://www.eea.europa.eu/data-and-maps/data/aqereporting)) provide the basis for estimating exposure of the urban European population to exceedances of the most stringent European air quality standards and WHO guidelines. Exposure is estimated based on concentrations measured at all urban and suburban background monitoring stations for most of the urban population, and at traffic stations for populations living within 100 m of major roads. The methodology is described by the EEA indicator, Exceedance of air quality limit values in urban areas (Indicator CSI 004).
This indicator compares concentrations of pollutants at background stations to those at traffic stations. This comparison provides an estimate of the increased levels of air pollution to which the population is exposed in areas with increased road traffic. It also provides a measure of the impact of the technical and non-technical measures adopted to reduce the road transport sector's contribution to observed concentrations.
The indicator makes use of the data submitted to Airbase. Data permitting, pan-European coverage is attempted and the indicator focuses on selected station pairs (traffic and urban background stations) from capital cities across Europe. Where data in capital cities are not available, the next largest city is chosen.
The units used in this indicator are the average yearly, daily and weekly variations of the concentrations at traffic and urban background stations, measured in micrograms per cubic metre (mg/m3).
This indicator provides information relevant for current European air quality legislation related to the setting of national emission targets (National Emission Ceiling Directive 2001/81/EC), the reduction of transport related emissions (discussed in detail in TERM 34) and the protection of human health from harmful air pollutant levels (Directives 1999/30/EC for sulphur dioxide, nitrogen dioxide and particulate matter and 2002/3/EC for ozone, both discussed in detail in CSI 004). The Directive on ambient air quality and cleaner air for Europe (Directive 2008/50/EC) also sets target and limit values for PM2.5 (particulate matter that passes through a size-selective inlet with a 50 % efficiency cut-off at 2.5 micrometres aerodynamic diameter), since 2010.
EU limit values for concentrations of nitrogen dioxide in ambient air
Both limit values had to be met by 1 January 2010:
EU limit values for concentrations of PM10 in ambient air
Both limit values had to be met by 1 January 2005:
EU limit values for concentrations of other pollutants:
- sulphur dioxide
Two limit values have been set for the protection of human health. Both limit values had to be met by 1 January 2005
- ozone
A combined ozone and acidification abatement strategy has been developed by the European Commission, resulting in a new Ozone Daughter Directive (2002/3/EC) and a National Emission Ceiling Directive (2001/81/EC). In this legislation, target values for ozone levels and for precursor emissions have been set.
Concentrations
Data submitted to Airbase have been used. The average diurnal variation was obtained by averaging each hour of the hourly data available at the selected measurement station. Average weekly variation was obtained by averaging the daily average for each day of the week (hourly or average daily data were used, depending on data availability) at the selected measurement station. Average yearly data were obtained from average hourly or average daily data, whichever were available at the selected measurement station (see data availability table for details). For all of the above, data gaps were not filled in.
No gap-filling is applied for this indicator, however, the databases and spreadsheets used for the production of the indicator contain gap-filled values.
No methodology references available.
Air quality data are officially submitted. It is assumed that data have been validated by the national data supplier. Station characteristics and representativeness are often insufficiently documented. The data are thought to be representative for the urban population in each city. Locally, (at the city level) the indicator is subject to year-on-year variations due to meteorological variability.
No uncertainty has been specified
For references, please go to https://www.eea.europa.eu/data-and-maps/indicators/exceedances-of-air-quality-objectives/exceedances-of-air-quality-objectives-9 or scan the QR code.
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