Nitrogen oxides (NOx) emissions (APE 002) - Assessment published Jan 2014
Air pollution (Primary topic)
Environment and health
Typology: Performance indicator (Type B - Does it matter?)
- APE 002
Key policy question: What progress is being made in reducing emissions of NOx?
- EEA-33 emissions of nitrogen oxides (NOX) decreased by 44% between 1990 and 2011. In 2011, the most significant sources of NOX emissions were 'Road transport' (41%), 'Energy production and distribution' (23%) and the 'Commercial, institutional and households' (13%) sectors.
- The largest reduction of emissions in absolute terms since 1990 has occurred in the road transport sector, from which emissions in the EEA-33 have fallen 48% since 1990; in all years since 1990, emissions in this sector have fallen compared with the previous year, by an average of 3% per year. This reduction has been achieved despite the general increase in activity within this sector since the early 1990s and has primarily been achieved as a result of fitting three-way catalysts to petrol fuelled vehicles. However, ambient urban concentrations of NO2 in EU-28 countries in recent years have not fallen by as much as reported emissions and a number of Member States' NOX emissions could therefore be systematically higher than currently calculated.
- In the electricity/energy production sector, reductions have occurred as a result of measures such as the introduction of combustion modification technologies (e.g. the use of low NOX burners, which reduce formation of NOX in combustion), the implementation of flue-gas abatement techniques (e.g. NOX scrubbers and selective catalytic and non-catalytic reduction techniques - SCR and SNCR) and fuel-switching from coal to gas (which has significantly lower NOX emissions per unit energy).
- 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 against their respective NOX ceilings than the older Member States of the EU-15. Twelve of the EU-13 Member States had reduced their emissions beyond what is required under the NECD by 2010, and by 2011 all had met their targets. In contrast, only five EU-15 Member States reported 2010 emissions within their respective national ceilings and by 2011 this had increased to just eight. Of the three non-EU countries having emission ceilings set under the UNECE/CLRTAP Gothenburg protocol, only Switzerland reported 2011 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.
 Emissions data reported by EU member states under NECD is used for comparison with NECD ceilings, while data reported under CLRTAP is used for all other calculations unless otherwise stated.
EEA-33 NOX emissions have decreased by 44% between 1990 and 2011. The majority of EEA-33 countries reported lower emissions of NOX in 2011 compared to 1990. The exceptions to this are Turkey (whose emissions were two times higher in 2011 than in 1990), Cyprus (24% higher), Luxembourg (24%) and Malta (4%).
The recession, and subsequent economic slow-down, that commenced mid-2008 was a key driver in the reduction of NOX emissions between 2007 and 2011, primarily due to reductions in the level of industrial and transport activities across Europe. Total emissions were reduced by 17% between these years, compared to a 7% reduction between 2003 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. All of the EU-13 Member States, which joined between 2004 and 2013, have reduced emissions beyond what is required under the NECD. In contrast, only eight EU-15 Member States had 2011 emissions below their respective national ceilings.
Despite this difference both EU-15 and New EU-13 groups have achieved broadly similar reductions in NOX emissions since 1990, of 49.1% and 48.7% respectively. However NECD ceilings for the groups are markedly different, representing reductions from 1990 emissions of 52% and 31% respectively. This difference is reflected less in the revised Gothenburg Protocol, under which the EU-15 and EU-13 groups are expected to achieve reductions of 44% and 35% respectively from 2005 levels of emissions.
As noted above, emissions have actually increased in four EEA-33 countries during the period 1990-2011, 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 2011 some progress had been made in moving towards their NECD ceiling directive limits.
Iceland, Liechtenstein, 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. While Switzerland has reported emissions in 2011 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 revision of the National Emission Ceilings Directive 2001/81/EC (NECD) is part of the implementation of the Thematic Strategy on Air Pollution. The proposal to amend the NECD is still under preparation and should set emission ceilings to be respected by 2020 for the four already regulated substances (NOX, NMVOC, SOX and NH3), as well as for the primary emissions of PM2.5. 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 and 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 2011 indicate that the majority of Member States are on track towards meeting their proposed 2020 emission reduction targets under the revised Gothenburg protocol. Eight countries reported 2011 emissions higher than the linear path to their 2020 targets, however, for five 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?
Reductions of NOX emissions have occurred in all economic sectors during this period. The sectors responsible for the vast majority of the decline in NOX emissions are 'Road transport' (contributing 47% of the total reduction in NOX emissions reported by countries) and 'Energy production and distribution' (contributing 27%).
Significant reductions have occurred in the 'Road transport' sector since the early 1990s, with a 48% overall decline in reported emissions between 1990 and 2011. 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).
Although the largest reduction of emissions in absolute terms since 1990 has occurred in the road transport sector, ambient urban concentrations of NO2 in EU-28 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-28 decreased by 29.5%. The disparity between trends in NOX emissions and ambient NO2 concentrations 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. The disparity is also due to the increased proportion of NOX emitted directly as NO2 from the exhausts of more modern diesel vehicles, which use catalyst systems for controlling emissions of other pollutants.
Emissions of NOX have also declined in the 'Energy production and distribution' sector (by 48% between 1990 and 2011). This has been achieved through the implementation of measures such as combustion modification, introduction of flue-gas abatement techniques and 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 - 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 that previously contributed to high levels of NOX emissions e.g. heavy industry and the closure of older, less efficient, power plants, and replacement of old vehicles with newer vehicles that meet Euro standards.
National emissions reported to the Convention on Long-range Transboundary Air Pollution (LRTAP Convention)
provided by United Nations Economic Commission for Europe (Environment and Human Settlements Division, UNECE)
National Emission Ceilings (NEC) Directive Inventory
provided by Directorate-General for Environment (DG ENV)
More information about this indicator
See this indicator specification for more details.
Contacts and ownership
EEA Contact InfoMartin Adams
EEA Management Plan2013 1.1.2 (note: EEA internal system)
Frequency of updates
- 20 Dec 2012 - Nitrogen oxides (NOx) emissions (APE 002) - Assessment published Dec 2012
- 21 Dec 2011 - Nitrogen oxides (NOx) emissions (APE 002) - Assessment published Dec 2011
- 15 Oct 2010 - Nitrogen oxides (NOx) emissions (APE 002) - Assessment published Oct 2010
- 15 Feb 2010 - EEA-32 Nitrogen oxides (NOx) emissions (APE 002) - Assessment published Feb 2010
- 07 Aug 2008 - Emission trends of nitrogen oxides NOx
- 20 Oct 2004 - EEA31 NOx emissions
For references, please go to www.eea.europa.eu/soer or scan the QR code.
This briefing is part of the EEA's report The European Environment - State and Outlook 2015. The EEA is an official agency of the EU, tasked with providing information on Europe’s environment.
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