Indicator Assessment

Nitrogen oxides (NOx) emissions

Indicator Assessment
Prod-ID: IND-166-en
  Also known as: APE 002
Published 15 Oct 2010 Last modified 11 May 2021
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  • EEA-32 emissions of nitrogen oxides (NOX) have decreased by 34% between 1990 and 2008. In 2008, the most significant sources of NOX emissions were the road transport sector (39%), combustion processes from within the energy industries sector (21%), the commercial, institutional and households sector (15%) and from industrial energy use (14%).
  • The largest reduction of emissions since 1990 has occurred in the road transport sector.  These reductions have been achieved despite the general increase in activity within this sector since the early 1990s and have primarily been achieved as a result of fitting three-way catalysts to petrol fuelled vehicles. In the electricity/energy production sector reductions have also occurred, in these instances as a result of measures such as the introduction of combustion modification technologies (such as use of low NOX burners), implementation of flue-gas abatement techniques (e.g. NOX scrubbers and selective (SCR) and non-selective (SNCR) catalytic reduction techniques) and fuel-switching from coal to gas.
  • The National Emission Ceilings Directive (NECD) specifies NOX emission ceilings for Member States that must be met by 2010. In general, the newer EU Member States have made substantially better progress towards meeting their respective NOX ceilings than the older Member States of the EU-15.  Ten of the twelve post-2004 Member States have already reduced emissions beyond what is required under the NECD, and one (Slovenia) reported NOX emissions just 5% above the NECD target in 2008. In contrast, only one EU-15 Member State (Finland) had 2008 emissions within its respective national ceiling.  Many Member States though require a significant reduction of NOX emissions to have been made in 2009 and 2010 if they are to meet their obligations under the NECD.  Of the three non-EU countries having emission ceilings set under the UNECE/CLRTAP Gothenburg protocol (Liechtenstein, Norway and Switzerland) only for Switzerland were emissions in 2008  below the level of the respective 2010 ceilings
  • Environmental context: NOX contributes to acid deposition and eutrophication. The subsequent impacts of acid deposition can be significant, including adverse effects on aquatic ecosystems in rivers and lakes and damage to forests, crops and other vegetation. Eutrophication can lead to severe reductions in water quality with subsequent impacts including decreased biodiversity, changes in species composition and dominance, and toxicity effects. It is NO2 that is associated with adverse affects on human health, as at high concentrations it can cause inflammation of the airways. NO2 also contributes to the formation of secondary particulate aerosols and tropospheric ozone in the atmosphere - both are important air pollutants due to their adverse impacts on human health.
This indicator is discontinued. No more assessments will be produced.

Change in emissions of nitrogen oxides compared with the 2010 NECD and Gothenburg protocol targets (EEA member countries)

Note: The reported change in nitrogen oxide emissions (NOx) for each country, 1990-2008, in comparison with the 2010 NECD and Gothenburg protocol targets.

Nitrogen oxide (NOx) distance-to-target for EEA member countries

Note: The distance-to-target indicator shows how current emissions compare to a linear emission reduction 'target-path' between 1990 emission levels and the 2010 emission ceiling for each country. Negative percentage values indicate the current emissions in a country are below the linear target path; positive values show that current emission lie above a linear target path to 2010.

EEA-32 NOX emissions have decreased by 34% between 1990 and 2008. The majority of EEA-32 countries have reported lower emissions of NOX in 2008 compared to 1990. The exceptions to this are Austria (+6% increase between 1990 and 2008), Cyprus (+27%), Greece (+19%), Malta (+50%), Portugal (+7%) and Turkey (+100%). The global recession that commenced mid-2008 played a key role in the emission reduction of NOx emissions between 2007 and 2008. Total emissions reduced by 8% between these two years, compared to a 4 % reduction between 2006 and 2007.

In general, the newer Member States of the European Union have made substantially better progress towards meeting their respective NOX ceilings than the older EU-15 Member States.  Ten of the twelve post-2004 Member States have already reduced emissions beyond what is required under the NECD, and one (Slovenia) is very close to doing so. In contrast, only one EU-15 Member State (Finland) has emissions within its respective national ceiling.

Emissions reported in 2008 indicate that many Member States are not considered to be on track towards meeting their obligations under the NECD. In particular Austria, Malta, Ireland, Luxembourg, Spain and France require significant reductions in NOX emissions to have been made in 2009 and 2010 if they are to meet their obligations under the NECD. As noted above, emissions have actually increased in six countries during the period 1990 to 2008, despite all countries having obligations to reduce emissions under the NECD and Gothenburg Protocol. Since 2005 however emissions have fallen in all these countries, indicating that by 2008 some progress had been made towards moving towards their NECD ceiling directive limits.

Iceland, Lichtenstein, Norway, Switzerland and Turkey are not members of the European Union and hence have no emission ceilings set under the NECD. However, Norway and Switzerland have ratified the UNECE LRTAP Convention’s Gothenburg Protocol, requiring them to reduce their emissions to the agreed ceiling specified in the protocol by 2010. Liechtenstein has also signed, but not ratified the protocol. Switzerland has reported emissions in 2008 that were lower than its respective ceiling, but both Liechtenstein and Norway, both of whom have not yet met their national ceilings, still must make significant reductions in order to ensure compliance.

The NECD and Gothenburg protocol are currently being reviewed. The revision of the NECD is part of the implementation of the Thematic Strategy on Air Pollution, but a proposal for a revised directive is presently on hold until 2013. A proposal to amend the Gothenburg protocol  is presently under preparation and is expected to propose emission ceilings to be met by 2020 for the four already regulated substances (NOx, NMVOCs, SO2 and NH3) and in addition for primary emissions of PM2.5.


Contribution to total change in nitrogen oxides emissions for each sector (EEA member countries)

Note: The contribution made by each sector to the total change in nitrogen oxide (NOx) emissions between 1990 and 2008.

Emissions by sector of nitrogen oxides - 2008 (EEA member countries)

Note: The contribution made by different sectors to emissions of nitrogen oxides.

Change in nitrogen oxides emissions for each sector between 1990 and 2008 (EEA member countries)

Note: Percentage change in nitrogen oxide (NOx) emissions for each sector between 1990 and 2008.

Reductions of NOX have occurred in all economic sectors apart from the ‘Non-road transport’ and ‘Commercial, institutional and households’ sectors, where emissions have increased by 1.1% and 0.8% respectively during this period. Emissions have also increased in the ‘Solvent and product use’ sector (by 269%), but in absolute terms this sector makes an insignificant contribution to the total NOX emissions. The three sectors responsible for the vast majority of the decline in NOX emissions are 'Road transport' (contributing 43% of the total reduction in NOX emissions reported by countries), 'Energy production and distribution' (contributing 26%), and 'Energy use in industry' (contributing 21%).

Significant reductions have occurred in the 'road transport' sector since the early 1990s, with an overall 36 % decline in emissions between 1990 and 2008. This has been achieved despite the general increase in activity within this sector over the period. The emission reductions have primarily been achieved as a result of fitting catalysts to vehicles (driven by the legislative 'Euro' standards). However, across Europe there is also an increasing awareness of the contribution made to NOX pollutant emissions by national and international ship traffic (a more detailed discussion of this issue is contained in the TERM indicator fact sheet TERM03 - Transport emissions of air pollutants).

Emissions of NOX have also declined in the 'Energy production and distribution' sector (39% reduction between 1990 and 2008). In the electricity/energy production sector this has been achieved through the implementation of measures such as combustion modification, introduction of flue-gas abatement techniques and a fuel-switching from coal to gas.  One of the most common forms of combustion modification is to use low NOX burners, which typically can reduce NOX emissions by up to 40%. Flue gas treatment techniques (e.g. NOX scrubbers and selective (SCR) and non-selective (SNCR) catalytic reduction techniques) can also be used to remove NOX from the flue gases. Emissions of NOX are higher from coal-fired power plants than from gas-fired plants as a result of coal containing significant amounts of nitrogen (unlike gas) and their less efficient combustion processes.

The newer Member States of the European Union have in a number of cases also undergone significant economic structural changes since the early 1990s which has led to a general decline in certain activities which previously contributed to high levels of NOX emissions e.g. heavy industry and the closure of older inefficient power plants.

Supporting information

Indicator definition

  • This indicator tracks trends since 1990 in anthropogenic emissions of nitrogen oxides.
  • The indicator also provides information on emissions by sectors: energy production and distribution; energy use in industry; industrial processes; road transport; non-road transport; commercial, institutional and households; solvent and product use; agriculture; waste; other.
  • Geographical coverage: EEA-32. The EEA-32 country grouping includes countries of the EU-27 (Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Netherlands, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden and the United Kingdom) EFTA-4 (Iceland, Liechtenstein, Switzerland and Norway) and Turkey.
  • Temporal coverage: 1990-2010


kilotonnes (1000 tonnes)


Policy context and targets

Context description

  • A number of policies have been implemented that directly or indirectly reduce the emissions of nitrogen oxides. These include: The National Emission Ceilings Directive 2001/81/EC (NECD), which entered into force in the European Community in 2001. The NECD sets emission ceilings for four important air pollutants (NOx, sulphur dioxide (SO2), ammonia (NH3) and non-methane volatile organic compounds (NMVOCs)) to be achieved from 2010 onwards for each Member State. The ceilings are designed to improve the protection in the Community of the environment and human health against risks of adverse effects arising from acidification, eutrophication and ground level ozone. The NECD is presently under review, the European Commission may adopt a proposal for a revised Directive during 2010.
  • The Gothenburg Protocol (1999) to the United Nations Economic Commission for Europe's (UNECE) Convention on Long-Range Transboundary Air Pollution (LRTAP Convention) to abate acidification, eutrophication and ground-level ozone. A key objective of the protocol is to regulate emissions on a regional basis within Europe and to protect ecosystems from transboundary pollution by setting emission reduction ceilings to be reached by 2010 for the same four pollutants as addressed in the NECD (i.e. SO2, NOx, NH3 and NMVOCs). Overall, for the EU Member States, the ceilings set within the Gothenburg protocol are generally either slightly less strict or the same as the emission ceilings specified in the NECD.
  • The Large Combustion Plant Directive (2001/80/EC) is important in reducing emissions of NOx, SO2 and dust from combustion plants having a thermal capacity equal to or greater than 50 MW. Installations within the scope of this Directive include power stations, petroleum refineries, steelworks and other industrial processes running on solid, liquid and gaseous fuels. "New" plant must meet the emission limit values (ELVs) given in the LCPD. However, Member States can choose to meet obligations for existing plant (i.e. those in operation pre-1987) by either complying with the ELVs or operating within a national emission reduction plan (NERP) that sets a ceiling for each pollutant. The interaction of the LCPD and the IPPC Directive (see below) is currently being examined as part of a review of the IPPC Directive.   
  • The Directive on Integrated Pollution Prevention and Control (96/61/EC) entered into force in 1999. It aims to prevent or minimise pollution to air, water or land from various industrial sources throughout the European Union. Those installations covered by Annex I of the IPPC Directive are required to obtain authorisation from the authorities to operate. New and existing installations, which are subject to 'substantial changes', have been required to meet the requirements of the IPPC Directive since 30 October 1999. Other existing installations must have been brought into compliance by 30 October 2007. The emission limit values outlined in the permit conditions must be based on the best available techniques (BAT). The Commission has been undertaking a review of the IPPC Directive and related legislation on industrial emissions, and on 21 December 2007 adopted a proposal for a Directive on industrial emissions. The proposal recasts seven existing Directives relating to industrial emissions (including IPCC and the LCPD) into a single legislative instrument.
  • The aim of the Directive 96/62/EC on ambient air quality assessment and management (the 'Air Quality Framework Directive') is to maintain and improve air quality within the European Community by establishing objectives for ambient air, drawing up common methods and criteria for assessing air quality and obtaining and disseminating information. The first "Daughter" Directive 99/30/EC entered into force in 1999 and set limit values for hourly and annual average nitrogen dioxide concentrations to be achieved throughout the community by 1 January 2010.
  • Since the early 1990s, standards on NOx emissions from new cars sold in Europe have been in place. This first came about with EU Directive 91/441/EC, which effectively mandated the fitting of three-way catalysts to all new petrol cars to significantly reduce emissions of CO, hydrocarbons and NOx. Standards for this Directive, frequently referred to as Euro 1, were followed by Euro 2 standards implemented by Directive 94/12/EC during the mid 1990s. Yet more stringent EU Directives have been put in place to reduce NOx emissions further, the most recent being (98/69/EC) setting emission limits for petrol cars sold after 2000 and then after 2005 (Euro 3 and 4 standards respectively).
  • NOx emissions from diesel vehicles have also been regulated since the early 1990s (since 1988 for heavy duty vehicles) with a succession of more stringent EU Directives. The legislation currently in force for heavy duty vehicles is 2005/55/EC and 2005/78/EC (implementing provisions), which define the emission standards currently in force, Euro IV, as well as the next stage (Euro V) which entered into force in October 2008.
  • In parallel with vehicle technology developments, improvements in the quality of petrol and diesel fuels have been made as a result of the EU Directive on fuel quality (98/70/EC as amended by 2003/17/EC). Fuel quality has little effect on NOx emissions directly, but improvements in fuel quality have allowed the fitting of exhaust after-treatment technologies and provided better catalyst performance, hence helping to reduce NOx emissions further. 


  • Directive 97/68/EC on the emissions of pollutants from internal combustion engines installed in non-road mobile machinery sets emission standards and type approval procedures for engines fitted to non-road mobile machinery.


Emissions of NOX are covered by the EU National Emission Ceilings Directive (NECD) (2001/81/EC) and the Gothenburg protocol under the United Nations Convention on Long-Range Transboundary Air Pollution (LRTAP Convention) (UNECE 1999). The NECD generally involves slightly stricter emission reduction targets than the Gothenburg Protocol for EU-15 countries for the period 1990-2010. The Gothenburg Protocol entered into force on 17 May 2005, after ratification by 16 countries early in 2005. The 2012 revision to the Gothenburg protocol proposed emission reduction targets for 2020 relative to 2005 reported emissions for all EU-27 Member States and some EEA-32 non-EU member states.

Table: 2010 NOX ceilings under the NEC Directive and the Gothenburg Protocol (kt)


2010 NECD

2010 CLRTAP Gothenburg Protocol ceilings

2020 CLRTAP Gothenburg Protocol ceilings

Austria 103 107 149
Belgium 176 181 172
Bulgaria 247 266 91
Cyprus 23 N/A 12
Czech Republic 286 286 181
Denmark 127 127 80
Estonia 60 N/A 30
Finland 170 170 110
France 810 860 715
Germany 1051 1081 963
Greece 344 344 289
Hungary 198 198 134
Iceland* N/A N/A N/A
Ireland 65 65 65
Italy 990 1000 727
Latvia 61 84 25
Liechtenstein N/A 0.37 N/A
Lithuania 110 110 29
Luxembourg 11 11 35
Malta 8 N/A 5
Netherlands 260 266 190
Norway N/A 156 154
Poland 879 879 606
Portugal 250 260 167
Romania 437 437 170
Slovakia 130 130 65
Slovenia 45 45 28
Spain 847 847 827
Switzerland N/A 79 55
Sweden 148 148 111
Turkey* N/A N/A N/A
United Kingdom 1167 1181 711

* Iceland and Turkey do not have a ceiling under the NEC Directive or the Gothenburg protocol.

Related policy documents



Methodology for indicator calculation

This indicator is based on officially reported national total and sectoral emissions to the EEA and the UNECE/EMEP (United Nations Economic Commission for Europe/Co-operative programme for monitoring and evaluation of the long-range transmission of air pollutants in Europe) Convention on Long-range Transboundary Air Pollution (LRTAP Convention), submission 2011. For the EU-27 Member States, the data used is consistent with the emissions data reported by the EU in its annual submission to the LRTAP Convention.

Recommended methodologies for emission inventory estimation are compiled in the EMEP/EEA Air Pollutant Emission Inventory Guidebook, (EMEP/EEA, 2009). Base data are available from the EEA Data Service ( and the EMEP web site ( Where necessary, gaps in reported data are filled by European Topic Centre/EEA using simple interpolation techniques (see below). The final gap-filled data used in this indicator are available from the EEA Data Service (

Base data, reported in the UNECE/EMEP Nomenclature for Reporting (NFR) sector format are aggregated into the following EEA sector codes to obtain a consistent reporting format across all countries and pollutants:

  • Energy production and distribution: emissions from public heat and electricity generation, oil refining, production of solid fuels, extraction and distribution of solid fossil fuels and geothermal energy;
  • Energy use in industry: emissions from combustion processes used in the manufacturing industry including boilers, gas turbines and stationary engines;
  • Industrial processes: emissions derived from non-combustion related processes such as the production of minerals, chemicals and metals;
  • Road transport: light and heavy duty vehicles, passenger cars and motorcycles;
  • Non-road transport: railways, domestic shipping, certain aircraft movements, and non-road mobile machinery used in agriculture and forestry;
  • Commercial, institutional and households: emissions principally occurring from fuel combustion in the services and household sectors;
  • Solvent and product use: non-combustion related emissions mainly in the services and households sectors including activities such as paint application, dry-cleaning and other use of solvents;
  • Agriculture: manure management, fertiliser application, field-burning of agricultural wastes
  • Waste: incineration, waste-water management;
  • Other: emissions included in national total for entire territory not allocated to any other sector.


The following table shows the conversion of Nomenclature for Reporting (NFR) sector codes used for reporting by countries into EEA sector codes:

EEA classification

Non-GHGs (NFR)


National totals

National total


Energy production and distribution

1A1, 1A3e, 1B


Energy use in industry



Road Transport



Non-road transport (non-road mobile machinery)

1A3 (excl. 1A3b)


Industrial processes



Solvent and product use









Commercial, institutional and households

1A4ai, 1A4aii, 1A4bi, 1A4bii, 1A4ci, 1A4cii, 1A5a, 1A5b





Methodology for gap filling

An improved gap-filling methodology was implemented in 2010 that enables a complete time series trend for the main air pollutants (eg NOX, SOX, NMVOC, NH3 and CO) to be compiled. In cases where countries did not report emissions for any year, it meant that gap-filling could not be applied. For these pollutants, therefore, the aggregated data is not yet complete and is likely to underestimate true emissions. Further methodological details of the gap-filling procedure are provided in section 1.4.2 'Data gaps and gap-filling' of the European Union emission inventory report 1990–2009 under the UNECE Convention on Long-range Transboundary Air Pollution (LRTAP).

Methodology references

No methodology references available.



Methodology uncertainty

The use of gap-filling when countries have not reported emissions for one of more years can potentially lead to artificial trends, but it is considered unavoidable if a comprehensive and comparable set of emissions data for European countries is required for policy analysis purposes.

Data sets uncertainty

NOX emissions estimates in Europe are thought to have an uncertainty of about ±20% (EMEP, 2010), as the NOX emitted comes from both the fuel burnt and the combustion air and so cannot be estimated accurately from fuel nitrogen alone. However, because of the need for interpolation to account for missing data, the complete dataset used will have higher uncertainty. The trend is likely to be more accurate than the individual absolute annual values - the annual values are not independent of each other.

Overall scoring: (1-3, 1 = no major problems, 3 = major reservations)

  • Relevancy: 1
  • Accuracy: 2
  • Comparability over time: 2
  • Comparability over space: 2


Rationale uncertainty

This indicator is regularly updated by the EEA and is used in state of the environment assessments. The uncertainties related to methodology and datasets are therefore of importance. Any uncertainties involved in the calculation and in the datasets need to be accurately communicated in the assessment to prevent erroneous messages influencing policy actions or processes.

Data sources

Other info

DPSIR: Pressure
Typology: Performance indicator (Type B - Does it matter?)
Indicator codes
  • APE 002
Frequency of updates
This indicator is discontinued. No more assessments will be produced.
EEA Contact Info


Geographic coverage

Temporal coverage