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Nitrogen oxides (NOx) emissions (APE 002) - Assessment published Dec 2012

Indicator Assessment Created 26 Sep 2012 Published 20 Dec 2012 Last modified 04 Dec 2013, 04:57 PM

Generic metadata


Air pollution Air pollution (Primary topic)

Environment and health Environment and health

Industry Industry

air quality | csi | nox | air emissions | nitrogen | air pollution indicators | pollution
DPSIR: Pressure
Typology: Performance indicator (Type B - Does it matter?)
Indicator codes
  • APE 002
Temporal coverage:
1990-2010, 2020
Geographic coverage:
EEA Member Countries (EEA32), Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Liechtenstein, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey, United Kingdom

Key policy question: What progress is being made in reducing emissions of NOx?

Key messages

    • EEA-32 emissions of nitrogen oxides (NOX) decreased by 42% between 1990 and 2010. In 2010, the most significant sources of NOX emissions were the 'Road transport' (41%), 'Energy production and distribution' (22%) and the 'Commercial, institutional and households' and 'Energy use in industry' (both 13%) sectors.
    • The largest reduction of emissions in absolute terms 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. However, ambient urban concentrations of NO2 in EU-27 countries in recent years have not fallen by as much as reported emissions. From 2001 to 2010, NO2 annual mean concentrations at urban background sites fell by just 10.6% on average (CSI004 - Fig 5) during which time the reported NOX emissions for the EU-27 decreased by 24.9%. The disparity between trends in NOX emissions and ambient NO2 concentration is due in part to increased penetration of diesel vehicles, and the ‘real-world’ emission performance of modern diesel vehicles not showing the improvements that were indicated by the test cycle emission factors used for emission inventories. It is also due to the increased proportion of NOX emitted directly as NO2 from the exhaust of more modern diesel vehicles which use catalyst systems for controlling emissions of other pollutants. As a result of this difference, a number of member states' NOX emissions could be significantly higher than currently calculated.
    • In the electricity/energy production sector reductions have also occurred 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 catalytic and non-catalytic reduction techniques, i.e. SCR and SNCR) and fuel-switching from coal to gas.
    • The National Emission Ceilings Directive (NECD) specifies NOX emission ceilings for Member States that must have been 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. Eleven of the twelve post-2004 Member States had reduced their 2010 emissions beyond what is required under the NECD[1], with the remaining one reporting NOX emissions just 2% above the NECD target. In contrast, only four of the EU-15 Member States reported emissions for 2010 within their respective national ceilings. Of the three non-EU countries having emission ceilings set under the UNECE/CLRTAP Gothenburg protocol (Liechtenstein, Norway and Switzerland), only Switzerland reported 2010 emissions below the level of their 2010 ceiling.
    • Environmental context: NOX contributes to acid deposition and eutrophication of soil and water. 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. NO2 is associated with adverse effects on human health, as at high concentrations it can cause inflammation of the airways and reduced lung function, increasing susceptibility to respiratory infection. It also contributes to the formation of secondary particulate aerosols and tropospheric ozone in the atmosphere, both of which are important air pollutants due to their adverse impacts on human health and other climate effects.

[1] Emissions data reported by EU member states under NECD is used for comparison with NECD ceilings, and data reported under CLRTAP is used for all other calculations unless otherwise stated.

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, 1990-2010, in comparison with the 2010 NECD and Gothenburg protocol targets.

Data source:
Downloads and more info

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 2010 emission levels and 2020 Gothenburg emission ceilings 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 2020.

Data source:
Downloads and more info

Key assessment

EEA-32 NOX emissions have decreased by 42% between 1990 and 2010. The majority of EEA-32 countries have reported lower emissions of NOX in 2010 compared to 1990. The exceptions to this are Hungary (whose emissions were 20 times higher in 2010 than 1990), Turkey (69% higher), Luxembourg (19%), Malta (7%) and Cyprus (7%).

The national total reported by Hungary has increased greatly from 1990 to 2010 due to the inclusion of sectors for which emissions were not reported in 1990; 'Industrial processes' emissions reported in CRF data represent over 99% of NOX in Hungary in 1990, whilst in 2009 LRTAP submissions they represent just 1%, showing that the 1990 national total for Hungary is significantly underestimated and thus falsifying the trend.

The recession, and subsequent economic slow-down, that commenced mid-2008 played a key role in the reduction of NOX emissions between 2007 and 2010, primarily by reducing the level of industrial and transport activities across Europe. Total emissions were reduced by 16% between these years, compared to a 6% reduction between 2004 and 2007.

In general, the newer Member States of the European Union have made better progress towards meeting their respective 2010 NOX ceilings than the older EU-15 Member States. Eleven of the twelve post-2004 Member States have reduced emissions beyond what is required under the NECD, and the remaining one reported NOX emissions less than 2% above the NECD target in 2010. In contrast, only four EU-15 Member States had 2010 emissions within their respective national ceilings. As can be seen in Fig 2, although Finland reported emissions under CLRTAP which were lower than their NECD ceiling, emissions reported in 2010 under NECD were above their ceiling.

Despite this difference both EU-15 and New EU-12 groups have achieved broadly similar reductions in NOX emissions since 1990, of 47% and 44% respectively. However NECD ceilings for the groups are markedly different, representing reductions from 1990 emissions of 52% and 28% respectively. This difference is not reflected in the revised Gothenburg Protocol, under which both groups are expected to achieve reductions of approximately 60% from 2005 levels of emissions.

As noted above, emissions have actually increased in five EEA-32 countries during the period 1990 to 2010, despite all countries having obligations to reduce emissions under the NECD and Gothenburg Protocol. Since 2005 however emissions have fallen in all but one of these countries, indicating that by 2010 some progress had been made in 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. Whilst Switzerland has reported emissions in 2010 that were lower than their ceiling, neither Liechtenstein nor Norway has yet met their national ceilings, and thus must still make significant reductions if they are to ensure compliance.

The NECD protocol is currently being reviewed, as 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 revision of the Gothenburg protocol was published in June 2012, and proposed percentage emission reductions from 2005 levels to be met by 2020 for the four already regulated substances (NOX, NMVOC, SO2 and NH3) and in addition for primary emissions of PM2.5. Existing emission ceilings for 2010 have been extended to 2020 such that all countries have additional obligations to maintain emission levels below their 2010 ceilings, or to further reduce emissions if they have not yet met these ceilings.

Emissions reported for 2010 indicate that the majority of Member States are on track towards meeting their proposed 2020 emission reduction targets under the revised Gothenburg protocol. Nine countries reported 2010 emissions higher than the linear path to their 2020 targets, however for six of these the difference was less than 10% of 2005 emissions.

Specific policy question: How do different sectors and processes contribute to emissions of NOx?

Sector share of nitrogen oxides emissions (EEA member countries)

Note: The contribution made by different sectors to emissions of nitrogen oxides in 2010.

Data source:
Downloads and more info

Change in nitrogen oxides (NOx) emissions for each sector between 1990 and 2010 (EEA member countries)

Note: Percentage change in nitrogen oxide (NOx) emissions for each sector between 1990 and 2010.

Data source:
Downloads and more info

Contribution to total change in nitrogen oxides (NOx) emissions for each sector between 1990 and 2010 (EEA member countries)

Note: The contribution made by each sector to the total change in nitrogen oxide (NOx) emissions between 1990 and 2010.

Data source:
Downloads and more info

Specific assessment

Reductions of NOX have occurred in all economic sectors apart from the 'Waste' sector, where emissions have increased by 32% during this period, however in absolute terms this sector makes an insignificant contribution to the total NOX emissions. The sectors responsible for the vast majority of the decline in NOX emissions are 'Road transport' (contributing 41% of the total reduction in NOX emissions reported by countries) and 'Energy production and distribution' (contributing 21%).

Significant reductions have occurred in the 'Road transport' sector since the early 1990s, with an overall 43% decline in reported emissions between 1990 and 2010. This has been achieved despite the general increase in transport 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 (by 40% between 1990 and 2010). 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 (such as NOX scrubbers, selective catalytic or non-catalytic reduction techniques, i.e. SCR and SNCR) 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 the coal contains significant amounts of nitrogen (unlike gas) and is burnt in 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, replacement of old vehicle fleet with new vehicles that meet Euro standards.

Data sources

More information about this indicator

See this indicator specification for more details.

Contacts and ownership

EEA Contact Info

Martin Adams


EEA Management Plan

2012 1.1.2 (note: EEA internal system)


Frequency of updates

Updates are scheduled once per year in October-December (Q4)
European Environment Agency (EEA)
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