Emissions of ozone precursors (CSI 002/APE 008) - Assessment published Jun 2014
Air pollution (Primary topic)
Environment and health
Typology: Performance indicator (Type B - Does it matter?)
- CSI 002
- APE 008
Key policy question: What progress is being made in reducing emissions of ozone precursors across Europe?
- Emissions of the main ground-level ozone precursor pollutants have decreased across the EEA-33 region between 1990 and 2011; nitrogen oxides (NOX) by 44%, non-methane volatile organic compounds (NMVOC) by 57%, carbon monoxide (CO) by 61%, and methane (CH4) by 29%.
- This decrease has been achieved mainly as a result of the introduction of catalytic converters for vehicles, which has significantly reduced emissions of NOX and CO from the road transport sector, the main source of ozone precursor emissions.
- The EU-28 as a whole reported 2011 emissions at 4% below the 2010 NECD ceiling for NOX, one of the two ozone precursors (NOX and NMVOC) for which emission limits exist under the EU's NEC Directive (NECD). Total NMVOC emissions in the EU-28 were 22% below the 2010 NECD limit in 2011, however, seven of individual Member States did not meet their ceilings for one or both of these two pollutants.
- Of the three non-EU countries having emission ceilings for 2010 set under the UNECE/CLRTAP Gothenburg protocol (Liechtenstein, Norway and Switzerland), all reported NMVOC emissions in 2011 that were lower than their respective ceilings, however Liechtenstein and Norway reported 2011 NOX emissions higher than their ceiling for 2010.
Emissions of the main tropospheric (ground-level) ozone precursors reduced across the EEA-33 region between 1990 and 2011 (Figure 1). The different precursor species contribute to ground-level ozone formation to differing extents, but in general NOX and NMVOC are considered the most important precursor species.
In most countries, reductions in emissions have occurred since 1990 for both of the two ozone precursors for which emission limits exist under the NEC Directive and UNECE Gothenburg Protocol, NOX and NMVOC (Figures 2 and 3). Detailed breakdowns of sectoral and national emissions of NOX and NMVOC are given in the pollutant specific factsheets for these pollutants, together with assessments of the compliance of countries with their respective 2010 emissions ceiling limits, and progress being made meeting 2020 emission ceiling limits.
Emissions of CO in 2011 were 27.1 Mt in the EEA-33 group of countries compared to 70.3 Mt in 1990, a reduction of 61%. Methane and NMVOC emissions also significantly reduced between 1990 and 2011, by 29% and 57% respectively. Emissions of nitrogen oxides have fallen from 18.3 Mt in 1990 to 10.2 Mt in 2011 (a 44% reduction), mainly due to the introduction of three way catalytic converters for cars. The introduction of other European legislative measures has also contributed to the reduction of ozone precursors, such as reductions of NMVOC as a result of the implementation of the Solvent Emissions Directive in industrial processes. Further reasons for the observed reductions in emissions are provided in the 'Specific assessment' section of this indicator factsheet below.
The global recession that commenced mid-2008 has contributed to the overall reduction of ozone precursor emissions in recent years. For example, emissions of NOX in the EEA-33 fell by 7% per year on average in 2008 and 2009, in contrast to a 2% decrease per year in 2006 and 2007.
The National Emission Ceilings Directive (NECD) and Gothenburg Protocol set ceilings (i.e. limits) for each of the EU-28 Member States for the two main ozone precursors, NOX and NMVOC, that must have been met by 2010. The reported data shows that seven of the 28 Member States reported 2011 emissions higher than their 2010 targets for NOX (APE001 - Figure 3), whilst only two Member States reported 2011 emissions higher than their 2010 ceiling for NMVOC (APE004 - Figure 3). Several of the non-EU countries (i.e. Liechtenstein, Norway and Switzerland) also have 2010 emissions ceilings defined under the Gothenburg protocol of the UNECE Convention on Long-range Transboundary Air Pollution. Of these countries, Liechtenstein and Norway have both reported 2011 emissions above their 2010 NOX ceilings, however all three countries' 2011 emissions were below their respective NMVOC ceilings.
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.
Further details concerning emissions of the main ozone precursor pollutants may be found in the following indicator fact sheets:
- Emission trends of nitrogen oxides (NOX)
- Emission trends of non-methane volatile organic compounds (NMVOC)
 The NECD and Gothenburg protocol also set emission ceilings for two other pollutants ammonia (NH3) and sulphur dioxide (SO2) that contribute to acidification and particulate matter formation.
 Liechtenstein has signed, but not yet ratified, the Gothenburg protocol.
Specific policy question: How do different sectors and processes contribute to emissions of ozone precursors?
In 2011, the most significant sources of ozone precursor pollutants in the EEA-33 region were the 'Agriculture' (48% of CH4 emissions), 'Solvent and product use' (43% of NMVOC emissions), and 'Road Transport' sources (40% of NOX and 26% of CO emissions) (Figure 6). Emissions of the various ozone-precursor pollutants have decreased across most sectors since 1990 (Figures 7 to 10).
Within the EEA-33, transport sectors are the dominant source of several ozone precursor pollutants. Combined, emissions from 'Road Transport' and 'Non-road Transport' contribute 29% of the total CO emissions in the EEA-33, 48% of NOX, and 17% of NMVOC.
Since 1990, the vast majority of the reduction of ozone precursor pollutants has occurred in the road transport sector, despite the general increase in transport activity within this sector over the period. This sector alone has contributed 75% of the total reduction of CO emissions, 47% of NOX reduction (Figure 11) and 52% of NMVOC reduction (Figure 12). The emission reductions have primarily been achieved as a result of fitting three way catalytic converters for petrol-fuelled cars (driven by the legislative Euro standards).
Emissions of NOX from the fuel-combustion related sectors 'Energy production and distribution' and 'Energy use in Industry' have also decreased significantly, together contributing 41% of the total reduction of NOX emissions since 1990. In this instance the reduction has been achieved as a result of measures including 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 (which has led to, for example, increases in energy efficiency and lower rates of NOX emissions).
National Emission Ceilings (NEC) Directive Inventory
provided by Directorate-General for Environment (DG ENV)
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 emissions reported to the UNFCCC and to the EU Greenhouse Gas Monitoring Mechanism
provided by Directorate-General for Environment (DG ENV) , United Nations Framework Convention on Climate Change (UNFCCC)
More information about this indicator
See this indicator specification for more details.
Contacts and ownership
EEA Contact Info
User not found: adamsma1
EEA Management Plan2013 1.1.2 (note: EEA internal system)
Frequency of updates
- 20 Dec 2012 - Emissions of ozone precursors (CSI 002/APE 008) - Assessment published Dec 2012
- 21 Dec 2011 - Emissions of ozone precursors (CSI 002/APE 008) - Assessment published Dec 2011
- 25 Oct 2010 - Emissions of ozone precursors (CSI 002/APE 008) - Assessment published Oct 2010
- 26 Jan 2010 - Emissions of ozone precursors (CSI 002) - Assessment published Jan 2010
- 19 Dec 2008 - Emissions of ozone precursors (CSI 002) - Assessment published Dec 2008
- 07 Mar 2008 - Emissions of ozone precursors (version 1) (CSI 002) - Assessment published Mar 2008
- 22 Dec 2006 - Emissions of ozone precursors (version 1) (CSI 002) - Assessment published Dec 2006
- 21 Oct 2005 - Emissions of ozone precursors (version 1) (CSI 002) - Assessment published Oct 2005
- 04 Oct 2004 - Emission of ozone precursors
- 01 Jun 2001 - Emission of ozone precursors
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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