Exceedances of air quality objectives due to traffic (TERM 004) - Assessment published Jan 2011

Indicator definition

The indicator compares concentrations at background stations to those at traffic stations. This comparison provides an estimate of the increased levels of air pollution that the population is exposed to when accessing areas with increased road traffic, as well as a measure of the impact of the technical and non-technical measures adopted to reduce the contribution of the road transport sector to the observed concentrations. 

The indicator makes use of the data submitted to Airbase. Data permitting, a pan-European coverage is attempted and the indicator focuses on selected station pairs (traffic and urban background stations) from capital cities across and where data in capital cities is not available the next largest city is chosen.

Values are presented for single monitoring stations that provide reliable time series data for the period 2000 to 2010.
Selected cities have at least one background and one traffic station that provide such reliability and can therefore be compared for analysis. Therefore, this figure does not represent air quality results citywide, but rather serves as a snapshot of the different trends in background and traffic stations wherever comparable long-term time-series data are available.
Because the different lines represent individual measurement points, there can be a significant effect from local changes in traffic flows.

The annual average difference between concentrations at specific traffic and urban background stations for cities across Europe over a number of years is highlighted and the relevant contribution of traffic is discussed.

Units

Average yearly, average daily and average weekly variations of the concentrations at traffic and urban background stations (in micro g/m³).

Policy context and targets

Context description

This indicator is relevant information for the 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 for Europe (Directive 2008/50/EC) also sets target and limit values for PM_2.5 (particulate matter which passes through s size-selective inlet with a 50% efficiency cut-off at 2.5 um aerodynamic diameter), since 2010.

Targets

EU limit values on concentrations of nitrogen dioxide in ambient air

Both limit values have 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 a calendar year has also been set.

EU limit values on 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 a calendar year is set for the protection of human health has been set in Council Directive 1999/30/EC (Annex III)
• a limit value of 40 mg/m³ as annual average has also been set.

EU limit values on 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 an daily average, not to be exceeded more than three times a calendar year, has been set for the protection of human health in the adopted Daughter 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 maximum daily 8 hour mean, not to be exceeded 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 within a calendar year (not to be exceeded any day).

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 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 has 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 where used, depending on data availability) at the selected measurement station. Average yearly data was obtained from average hourly or average daily data, whichever was available at the selected measurement station (see data availability table for details). For all of the above, data gaps were not filled in.
The graphs related to the interannual variation of NO₂ and PM₁₀ concentrations separately for traffic and urban background stations across Europe, have been prepared using station pairs from capital cities and when not available the next largest city for which data was available was chosen. Since the available data (stations) vary from year to year (see tables of yearly average values for details), in order to ensure a consistent dataset only stations with complete data (all years) were chosen. Meteorological data is not available, so meteorologically induced changes cannot be analysed. All stations for this analysis were selected according to their yearly data availability and their completeness as regards hourly data availability. For certain years and stations the data availability is low, however these are used as no alternative are available (see data availability table for details).

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

• Buijsman E, PR van Hooydonk, WJA Mol, L Cernikovsky (ETC/ACC) 2004, European exchange of air quality monitoring meta information in 2002, ETC/ACC Technical Paper 2004/1
• Adams M and J Goodwin (AEA Technology Environment, uk), B Gugele (UBA-Vienna, AT) 2004, EEA/ETC-ACC technical report describing the gap-filling methodologies used for the 2004 EEA/ETC-ACC LRTAP Convention and GHG (CRF) air emissions spreadsheet, ETC/ACC Technical Paper 2004/3

Uncertainties

Methodology uncertainty

The air quality data is officially submitted data. It is assumed that data has been validated by the national data supplier. Station characteristics and representativeness is often insufficiently documented. The data is thought to be representative for the urban population in each city. Locally (at the city level) the indicator is subject to year-to-year variations due to meteorological variability.

Data sets uncertainty

Strengths and weaknesses (at data level): officially reported data by the countries to Airbase is used, however the data reported across countries varies in quantity. Also the station characterisation (urban background or traffic) is difficult to compare across countries. Reliability, accuracy, robustness, uncertainty (at data level): The uncertainties are discussed separately for each graph. The data quality cannot be commented upon, since it data 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). Main problem is the lack of data and not the actual quality of the data available.

Rationale uncertainty

No uncertainty has been specified