Exceedances of air quality objectives due to traffic

Indicator definition

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.

Units

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).

Policy context and targets

Context description

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 PM_2.5 (particulate matter that passes through a size-selective inlet with a 50 % efficiency cut-off at 2.5 micrometres aerodynamic diameter), since 2010.

Targets

EU limit values for concentrations of nitrogen dioxide in ambient air

Both limit values had to be met by 1 January 2010:

• In the Council Directive 1999/30/EC (section 1 of Annex II), an annual mean limit value for nitrogen dioxide of 40 mg NO₂/m³ has been set for the protection of human health.
• An hourly limit value of 200 mg NO₂/m³, not to be exceeded more than 18 times per calendar year, has also been set.

EU limit values for concentrations of PM₁₀ in ambient air

Both limit values had to be met by 1 January 2005:

• a limit value for PM₁₀ of 50 mg/m³ (24 hour average, i.e. daily), not to be exceeded more than 35 times per calendar year, has been set for the protection of human health in Council Directive 1999/30/EC (Annex III).
• an annual average limit value of 40 mg/m³ has also been set.

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

• a limit value of 125 mg SO₂/m³, as a daily average not to be exceeded more than three times per calendar year, has been set for the protection of human health in the adopted Daughter Directive 1999/30/EC, Section I of Annex I.

• an hourly limit value for the protection of human health has been set at 350 mg.

- 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.

• The Ozone Daughter Directive sets a target value for the protection of human health of 120 mg O₃/m³, as a maximum daily 8 hour mean, not to be exceeded on more than 25 days per calendar year, averaged over three years. This target should be met in 2010.
• The Ozone Daughter Directive has also set a long-term objective of 120 mg O₃/m³, as a maximum daily 8 hour average not to be exceeded on any day within a calendar year.

Related policy documents

• COM(2001) 245 final. The Clean Air for Europe (CAFE).
  The Clean Air for Europe (CAFE) Programme: Towards a Thematic Strategy for Air Quality COM(2001) 245 final
• Council Directive 96/62/EC of 27 September 1996
  Council Directive 96/62/EC of 27 September 1996 on ambient air quality assessment and management.
• Council Directive 1999/30/EC of 22 April 1999
  Council Directive 1999/30/EC of 22 April 1999 Relating to limit values for sulphur dioxide, nitrogen dioxide and oxides of nitrogen, particulate matter and lead in ambient air
• Directive 2001/81/EC, national emission ceilings
  Directive 2001/81/EC, on nation al emissions ceilings (NECD) for certain atmospheric pollutants. Emission reduction targets for the new EU10 Member States have been specified in the Treaty of Accession to the European Union 2003  [The Treaty of Accession 2003 of the Czech Republic, Estonia, Cyprus, Latvia, Lithuania, Hungary, Malta, Poland, Slovenia and Slovakia. AA2003/ACT/Annex II/en 2072] in order that they can comply with the NECD.
• Directive 2002/3/ EC...ozone in ambient air
  Directive 2002/3/ EC of the European Parliament and of the Council of 12 February 2002 relating to ozone 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

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.

Methodology for gap filling

No gap-filling is applied for this indicator, however, the databases and spreadsheets used for the production of the indicator contain gap-filled values.

Methodology references

No methodology references available.

Uncertainties

Methodology uncertainty

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.

Data sets uncertainty

• Strengths and weaknesses (at data level): data officially reported by the countries to Airbase are used, however, the data reported across countries vary in quantity. Also, the station characterisation (urban background or traffic) is difficult to compare across countries. 
• Reliability, accuracy, robustness, uncertainty (at data level): Uncertainties are discussed separately for each graph. The data quality cannot be commented upon, since the data are reported by the individual countries, but data availability is sometimes low and does not allow for robust conclusions/intercomparisons (see data availability table for details). The main problem is the lack of data and not the actual quality of the data available.

Rationale uncertainty

No uncertainty has been specified