Indicator Specification

Transport emissions of air pollutants

Indicator Specification
  Indicator codes: TERM 003
Published 23 Dec 2008 Last modified 25 Aug 2017
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The indicator is based on the emission trend assessment of CO, CH 4 , NH 3 , NO x , NMVOCs, SO x and primary particulates. These substances are grouped into acidifying substances (NO x , SO x and NH 3 ), particulates (primary: PM 10, PM 2.5 , secondary: NO x , SO x and NH 3 ) and ozone precursors (CH 4 , CO, NMVOC and NO x ). The assessment is made for the total transport sector.

Assessment versions

Published (reviewed and quality assured)
  • No published assessments


Justification for indicator selection

This indicator analyses the transport emissions of CO, CH4, NH3, NOx, NMVOCs, PM10, PM2.5 and SOx from 1990 to 2008. The pollutants are grouped into acidifying substances, particulates (primary and secondary) and ozone precursors. Transport contributes significantly to emissions of NOx, NMVOC, PM and CO. NOx contributes to acidification, formation of ground level ozone and particulate formation.

Acidifying substances: Acidification of soils and waters is caused by emissions of nitrogen oxides (NOx), sulphur oxides (SOx) and ammonia (NH3) into the atmosphere, and their subsequent chemical reactions and deposition on ecosystems and materials. Deposition of acidifying substances causes damages to ecosystems, buildings and materials (corrosion).

Particulate Formation: Airborne particulate matter (PM) has adverse effects on human health and can be responsible and/or contribute to a number of respiratory problems. In this assessment, ‘particulate formation’ refers to primary emissions of PM10, PM 2.5 and emissions of precursors (NOx, SOx and NH3) leading to the secondary physico-chemical production of inorganic particulate matter in the atmosphere (secondary PM). A large fraction of the urban population is exposed to levels of fine particulate matter in excess of air quality limit values set for the protection of human health.

Ozone precursors: Emissions of non-methane volatile organic compounds (NMVOC), nitrogen oxides (NOx), carbon monoxide (CO) and methane (CH4) contribute to the formation of ground-level (tropospheric) ozone which has adverse effects on human health and ecosystems.


Scientific references

  • No rationale references available

Indicator definition

The indicator is based on the emission trend assessment of CO, CH4, NH3, NOx, NMVOCs, SOx and primary particulates. These substances are grouped into acidifying substances (NOx, SOx and NH3), particulates (primary: PM10, PM2.5, secondary: NOx, SOx and NH3) and ozone precursors (CH4, CO, NMVOC and NOx). The assessment is made for the total transport sector.


The conversion factors used are the following:

  • Acidifying substances: NH3: 0.0588, NOx: 0.0217; SOx: 0.0313
  • Ozone precursors: CH4: 0.0140, CO: 0.1100, NMVOC: 1, NOx: 1.2200
  • Particulate matter: NH3: 0.6400, NOx: 0.8800, PM10: 1, SOx: 0.5400

Policy context and targets

Context description

No specific emission reduction target or objective exists for transport-related emissions of acidifying substances, ozone precursors or particulates. However, emission ceiling targets for total NOx, SOx, NMVOC and NH3 emissions are specified in both the EU National Emission Ceilings Directive (NECD) and the Gothenburg protocol under the United Nations Convention on Long-Range Transboundary Air Pollution (LRTAP Convention) (UNECE 1999). Following the Directive on ambient air quality and cleaner air for Europe (2008/50/EC), a number of limit values (e.g. hourly limit values) have been set for the atmospheric concentrations of main pollutants, including SOx, NOx, air borne particulate matter (PM10, PM2.5), lead, CO, benzene and ozone. Limits have been set at levels that should prevent or reduce harmful effects on health and ecosystems. Although aiming at the reduction of greenhouse gas emissions the EU climate and energy package will also influence the emissions of air pollutants from the transport sector. In some countries national standards also apply.


Both the NECD and Gothenburg protocol set reductions targets for sulphur dioxide, nitrogen oxides and non-methane volatile organic compounds and ammonia for the 32 EEA member countries. There are substantial differences in emission ceilings, and hence emission reduction percentages for different countries, due to the different sensitivities of the affected ecosystems and technical feasibility for reductions.

Related policy documents

  • 1999 Protocol to Abate Acidification, Eutrophication and Ground-level Ozone
    Convention on Long-range Transboundary Air Pollution 1999 Protocol to Abate Acidification, Eutrophication and Ground-level Ozone, amended on 4 May 2012.
  • Council Directive 96/61/EC (IPPC)
    Council Directive 96/61/EC of 24 September 1996 concerning Integrated Pollution Prevention and Control (IPPC). Official Journal L 257.
  • Directive 98/70/EC, quality of petrol and diesel fuels
    Directive 98/70/EC of the European Parliament and of the Council of 13 October 1998 relating to the quality of petrol and diesel fuels and amending Directive 93/12/EEC
  • Directive 2001/80/EC, large combustion plants
    Directive 2001/80/EC of the European Parliament and of the Council of 23 October 2001 on the limitation of emissions of certain pollutants into the air from large combustion plants
  • 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.


Methodology for indicator calculation

Data sources: For CH4 data from the country reports submitted in 2010 under the EU Monitoring Mechanism and to UNFCCC has been used. For air pollutants officially reported data to EMEP/LRTAP by 07 May 2010 has been used.

Methodology for gap filling

Where a complete time series of emissions data has not been reported, data has been gap-filled according to EEA ETC/ACC methodologies. Details of the gap-filling procedure for the air pollutant data set are described in the European Union emission inventory report 1990–2008 under the UNECE Convention on Long-range Transboundary Air Pollution (LRTAP) (EEA Technical Report No 7/2010).

Methodology references

No methodology references available.


Data specifications

EEA data references

Data sources in latest figures



Methodology uncertainty

No uncertainty has been specified

Data sets uncertainty

For greenhouse gases the results of the tier 1 level uncertainty estimate suggest that uncertainties at EU-15 level were between 4.8 % and 10.2 % for total EU-15 GHG emissions in 2008. Transport related GHG emissions are estimated to have an uncertainty of 6 % in 2008 (see EEA, 2010). For the new Member States and some other EEA countries, uncertainties are assumed to be higher than for the EU-15 Member States because of data gaps. A quantification of uncertainty in the European Union LRTAP emission inventory requires the provision of detailed underpinning information on emission uncertainties from Member States. An evaluation of uncertainty at the EuropeanUnion level (including all EU-27 Member States) has not been performed, because insufficient information has been reported by Member States.

Rationale uncertainty

No uncertainty has been specified

Further work

Short term work

Work specified here requires to be completed within 1 year from now.

Long term work

Work specified here will require more than 1 year (from now) to be completed.

General metadata

Responsibility and ownership

EEA Contact Info

Cinzia Pastorello


European Environment Agency (EEA)


Indicator code
TERM 003
Version id: 1
Primary theme: Transport Transport


DPSIR: Pressure
Typology: Descriptive indicator (Type A - What is happening to the environment and to humans?)



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