Indicator Specification

Emissions of air pollutants from transport

Indicator Specification
  Indicator codes: TERM 003
Published 12 Jan 2011 Last modified 04 Sep 2019
6 min read
This indicator is based on the assessment of emissions trends of CO, NO x , NMVOCs, SO x and primary particulates. 

Assessment versions

Published (reviewed and quality assured)
  • No published assessments


Justification for indicator selection

This indicator analyses the emissions from transport of CO, NOx, NMVOCs, PM10, PM2.5 and SOx over time. These pollutants can be grouped into acidifying substances, particulate matters and ozone precursors. Transport contributes significantly to emissions of NOx, NMVOCs, PM and CO. NOx contributes to acidification, the formation of ground-level ozone and particulate formation.

Acidifying substances: the acidification of soils and waters is caused by emissions of NOx, SOx and NH3 into the atmosphere, and their subsequent chemical reactions and depositions in ecosystems and on materials. The deposition of acidifying substances causes damage to ecosystems, buildings and other materials (corrosion).

Particulate formation: airborne PM has adverse effects on human health and can be responsible for and/or contribute to a number of respiratory problems. In this assessment, 'particulate formation' refers to primary emissions of PM10 and PM2.5 and emissions of precursors (NOx, SOx and NH3), which lead to the secondary physico-chemical production of inorganic PM in the atmosphere (secondary PM). A large fraction of the urban population is exposed to levels of fine PM in excess of air quality limit values set for the protection of human health.

Ozone precursors: emissions of NMVOCs, NOx, 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

This indicator is based on the assessment of emissions trends of CO, NOx, NMVOCs, SOx and primary particulates. 


Emissions are expressed as a percentage of 1990 levels (except for PM emissions, which are expressed as a percentage of 2000 levels).


Policy context and targets

Context description

Directive 2008/50/EC (EC, 2008) sets limit values for the atmospheric concentrations of the main pollutants, including sulphur dioxide (SO2), nitrogen dioxide (NO2), airborne PM (PM10 and PM2.5), lead, CO, benzene and ozone (O3) for EU Member States. These limits are related to transport implicitly, but the introduction of progressively stricter Euro emissions standards and fuel quality standards has led to substantial reductions in air pollutant emissions. Policies aimed at reducing fuel consumption in the transport sector, to cut greenhouse gas emissions, may also help to further reduce air pollutant emissions.

Iceland, Liechtenstein, Norway, Switzerland and Turkey are not members of the EU and hence have no emission ceilings set under the revised National Emission Ceilings Directive (NECD), Directive (EU) 2016/2284. As well as most of the EU Member States, Norway and Switzerland have ratified the 1999 United Nations Economic Commission for Europe (UNECE) Convention on Long-Range Transboundary Air Pollution (LRTAP) Gothenburg Protocol, which required them to reduce their emissions to the agreed ceiling, specified in the protocol, by 2010. Liechtenstein has also signed, but has not ratified, the protocol.


Both the NECD and the Gothenburg Protocol set reduction targets for SO2, NOx, NMVOCs and NH3 for the EEA-33 member countries. There are substantial differences in emission ceilings and, hence, emission reduction percentages for different countries, due to the different sensitivities of the ecosystems affected and the technical feasibility of making reductions.

Related policy documents

Key policy question

Are the emissions of acidifying substances, particulates and ozone precursors from transport decreasing?



Methodology for indicator calculation

For air pollutants, data officially reported to the European Monitoring and Evaluation Programme (EMEP)/LRTAP Convention have been used. According to reporting requirements, emission figures for all pollutants are available from 1990, and for PM2.5, PM10 and total suspended particles (TSP) from 2000.

Methodology for gap filling

Where a complete time series of emission data has not been reported, data have been gap filled according to the methodologies of the European Environment Agency's (EEA's) European Topic Centre on Air and Climate Change (ETC/ACC). Details of the gap-filling procedure for the air pollutant data set are described in the EU emission inventory report 1990-2017 under the UNECE's Convention on LRTAP (EEA Technical Report No 8/2019).

Methodology references

  • EU emission inventory report European Union emission inventory report 1990-2017 under the UNECE Convention on Long-range Transboundary Air Pollution (LRTAP) , EEA Technical report No 8/2019.

Data specifications

EEA data references

Data sources in latest figures



Methodology uncertainty

Interpolation/extrapolation procedures are used to gap fill the underlying emission data set.

Data sets uncertainty

For the quantification of uncertainty, the EU LRTAP emissions inventory requires that Member States provide detailed information on uncertainties related to reported emissions data.

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

Federico Antognazza


European Environment Agency (EEA)


Indicator code
TERM 003
Version id: 2
Primary theme: Transport Transport

Frequency of updates

Updates are scheduled once per year


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



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