Air pollution statistics - air emissions accounts

Data from December 2023

Next update of the article: December 2024

Highlights

Between 2008 and 2021, emissions of acidifying gases (ammonia, nitrogen oxides and sulphur dioxide) in the EU decreased by 38 %.

Between 2008 and 2021, emissions of ozone precursors (nitrogen oxides, non-methane volatile organic compounds, carbon monoxide and methane) in the EU decreased by 30 %.

Ozone precursor emissions by chemical compound, EU, 2008-2021

This article is about emissions of acidifying gases and ozone precursor substances classified by emitting economic activities. Eurostat records and publishes those in annual air emissions accounts (AEA), one of the modules in the European environmental economic accounts (for which the legal basis is Regulation (EU) No 691/2011). AEA are suited for integrated environmental economic analyses such as calculating emission intensities or 'footprints'.

In addition, Eurostat disseminates emissions of air pollutants classified by technical processes. These are recorded in emission inventories for air pollutants and form the official data for international policies on transboundary air pollution. Furthermore, Eurostat estimates and disseminates 'footprints' which are emissions of air pollutants classified by final products that are demanded by households or government, or that are invested in or exported.

Full article

Editorial note: Throughout this article, which deals with time periods when the United Kingdom was a Member State of the European Union, the acronym EU refers to the post-Brexit composition of the European Union as of 1 February 2020.

General overview

The EU emissions of acidifying gases (sulphur dioxide (SO₂), nitrogen oxides (NO_x) and ammonia (NH₃)) have been continuously decreasing over the past years. In 2021, emissions of NH₃ and NO_x contributed 44 % and 43 %, respectively, while sulphur dioxide contributed 13 % to the total acidifying potential.

The EU emissions of ozone precursors (nitrogen oxides (NO_x), methane (CH₄), carbon monoxide (CO) and non-methane volatile organic compounds (NMVOC) have also been falling over the past years. In 2021, the main contributors to the tropospheric ozone formation potential were NO_x and NMVOC with 54 % and 34 %, respectively.

Acidifying gases

Several air pollutants contribute to the acidification of the environment. The most important ones are sulphur dioxide (SO₂), nitrogen oxides (NO_x) and ammonia (NH₃). The impact of SO₂, NO_x and NH₃ can be observed in the progressive degradation of soils, water and forests. They also contribute to the formation of fine particles in the air that cause respiratory diseases. The acidifying potential of SO₂, NO_x and NH₃ is commonly measured in SO₂ equivalents (SO₂ eq.).

Emissions of acidifying gases have been on a continuous decrease

The acidifying potential associated with EU residents' emissions has been continuously decreasing over the past decade (Figure 1). Between 2008 and 2021 emissions of the three main acidifying gases decreased by approximately 9 million tonnes of SO₂ eq. to reach 14.4 million tonnes of SO₂ eq. (-38 %). SO₂ emissions decreased by 73 % and contributed 13 % to the total acidifying potential. NO_x emissions decreased by 34 % and contributed 43 % to the total acidifying potential. Emissions of ammonia (NH₃), quantitatively the most significant acidifying gas decreased by 10 % and contributed 44 % to the total acidifying potential.

Figure 1: Acidifying gas emissions by chemical compound, EU, 2008-2021
(thousand tonnes of SO₂ equivalents)
Source: Eurostat (env_ac_ainah_r2)

Acidifying gas emissions by economic activity

Agriculture, forestry and fishing emits the most acidifying gases. In 2021, it contributed 47 % of the acidifying gases emitted by EU industries and households (Figure 2). Ammonia (NH₃) is the most significant acidifying substance emitted by agriculture, forestry and fishing (Figure 3). In 2021, transportation and storage was the production activity with the second largest share (22 %) in total acidifying emissions (Figure 2). In this case, NO_x was the dominant acidifying gas (Figure 3).

Figure 2: Acidifying gas emissions by economic activity, EU, 2008 and 2021
(thousand tonnes of SO₂ equivalents)
Source: Eurostat (env_ac_ainah_r2)

Most activities recorded significant drops in acidifying gas emissions. The largest decrease was observed in electricity, gas, steam and air conditioning supply industry, which dropped from 1.1 million tonnes of SO₂ eq. in 2008 to 1.0 million tonnes of SO₂ eq. in 2021 (-76 %). A more systematic use of end-of-pipe pollution filters and the use of more efficient combustion technologies in electricity and heat production are the main contributors to this development.

Figure 3: Acidifying gas emissions by economic activity and chemical compound, EU, 2021
(thousand tonnes of SO₂ equivalents)
Source: Eurostat (env_ac_ainah_r2)

Comparing acidifying gas emissions with gross value added

Figure 4 compares acidifying gas emissions (AGE) with the gross value added (GVA) of 64 production activities (NACE classification) in the EU in 2021. This breakdown into 64 production activities is the same that is used in economic statistics (national accounts), therefore enabling integrated analyses. In Figure 4 the production activities are in descending order of their acidifying gas emissions. Both bars (AGE and GVA) of each production activity show the cumulated percentage, in other words, the percentage of all the activities, which are to the left of the activity and the activity itself.

Figure 4: Acidifying gas emissions and gross value added by 64 production activities (NACE), EU, 2021
(cumulated %)
Source: Eurostat (env_ac_ainah_r2) and (naio_10_cp1610)

Figure 4 shows that the top five emitters account for 84 % of the total acidifying gas emissions of the 64 production activities, while these five production activities only contribute approximately 7 % to the gross domestic product (GDP) of the EU economy. These five production activities are crop and animal production, hunting and related service activities (NACE A01), water transport (NACE H50), electricity, gas, steam and air conditioning supply (NACE D), land transport and transport via pipelines (NACE H49) and manufacture of other non-metallic mineral products (NACE C23). The GDP is the sum of gross value added of the 64 production activities plus net taxes on products. In Figure 4 only the NACE codes of the production activities are given due to space restrictions. Their names and descriptions are available here.

Ozone precursors

Tropospheric ozone occurs when ozone precursor substances (i.e., non-methane volatile organic compounds (NMVOC), nitrogen oxides (NO_x), carbon monoxide (CO) and methane (CH₄)) react in the lower atmosphere in the presence of sunlight. High ozone levels occur during the warmer summer months as the sun makes, for example, exhaust fumes from vehicles react in the lower atmosphere. High ozone levels are known to damage human tissue and are a health risk, especially for people with respiratory problems. Through the National Emissions Ceilings Directive (NECD) and the Gothenburg Protocol under UNECE-CLRTAP (United Nations Economic Commission for Europe Convention on Long-range Transboundary Air Pollution), the EU focuses on the emissions of NO_x and NMVOC as they are the most relevant of the four pollutants.

Emissions of ozone precursors have been on a continuous decrease, NO_x is the most significant ozone precursor

From 2008 to 2021, the tropospheric ozone formation potential associated with EU residents' emissions of ozone precursors continuously decreased by 8.5 million tonnes of NMVOC equivalents (NMVOC eq.), to reach 19.8 million tonnes of NMVOC eq. (-30 %). The most significant ozone precursor NO_x, decreased the most throughout the last twelve years (-5.6 million tonnes). NMVOC emissions decreased by 1.9 million tonnes and CO emissions decreased by 0.9 million tonnes NMVOC eq. (Figure 5).

Figure 5: Ozone precursor emissions by chemical compound, EU, 2008-2021
(thousand tonnes of NMVOC equivalents)
Source: Eurostat (env_ac_ainah_r2)

Ozone precursor emissions by economic activity

With 26 % each, private households and the transport industry contributed the most to total emissions of ozone precursors in 2021. Agriculture, forestry and fishing industry was the third largest emitter with 17 % (Figure 6).

Between 2008 and 2021, the largest absolute drop occurred in households (2.3 million tonnes of NMVOC eq. or -31 %). For the same period, the largest relative drop was observed in electricity, gas, steam and air conditioning supply with -52 %.

Figure 6: Ozone precursor emissions by economic activity, EU, 2008 and 2021
(thousand tonnes of NMVOC equivalents)
Source: Eurostat (env_ac_ainah_r2)

In 2021, NMVOC was the most significant ozone precursor emitted by households, manufacturing and agriculture. NO_x was the most significant ozone precursor emitted by the transportation industry and the electricity, gas, steam and air conditioning industry (Figure 7).

Figure 7: Ozone precursor emissions by economic activity and chemical compound, EU, 2021
(thousand tonnes of NMVOC equivalents)
Source: Eurostat (env_ac_ainah_r2)

Comparing ozone precursor emissions with gross value added

Figure 8 compares ozone precursor emissions (O3PR) with the gross value added (GVA) for 64 production activities (NACE classification) in the EU in 2021. This breakdown into 64 production activities is used for economic statistics (national accounts), therefore enabling integrated analyses. In Figure 8 the production activities are in descending order of their ozone precursor emissions. Both bars (O3PR and GVA) of each production activity show the cumulated percentage, in other words the percentage of all the activities, which are to the left of the activity and the activity itself.

Figure 8: Ozone precursor emissions and gross value added by 64 production activities (NACE), EU, 2021
(cumulated %)
Source: Eurostat (env_ac_ainah_r2) and (naio_10_cp1610)

Figure 8 shows that top five emitters account for nearly 64 % of ozone precursor emissions of the 64 production activities, while these top five production activities only contribute to 12 % of the gross domestic product (GDP). These five production activities are water transport (NACE H50), crop and animal production, hunting and related service activities (NACE A01), electricity, gas, steam and air conditioning supply (NACE D), land transport and transport via pipelines (NACE H49) and construction (NACE F). The GDP is the sum of gross value added of the 64 production activities plus net taxes on products. In Figure 8 only the NACE codes of the production activities are given due to space restrictions. Their names and descriptions are available here.

Source data for tables and graphs

Air pollution statistics - air emissions accounts: tables and figures

Data sources

The basis for Eurostat's air emissions accounts is Regulation (EU) No 691/2011 on European environmental economic accounts.

Annual data are transmitted by the EU Member States, as well as the European Free Trade Association (EFTA) countries and some candidate countries.

Emissions of individual acidifying gases and ozone precursor substances are converted and aggregated to provide information for the environmental pressures 'acidifying potential' and 'tropospheric ozone formation potential'. They use common units (SO₂ equivalent and NMVOC equivalent) to allow comparison and combination of the relative effect of different gases. For calculating SO₂ equivalents the following conversion factors are used: nitrogen oxides 0.7, sulphur dioxide 1.0 and ammonia 1.9. For calculating NMVOC equivalents the following conversion factors are used: nitrogen oxides 1.22, non-methane volatile organic compounds 1.0, carbon monoxide 0.11 and methane 0.014.

In air emissions accounts, emission data are organised by economic activity, using NACE. This makes it possible to have an integrated environmental-economic analysis to supplement national accounts. Economic activities encompass production by all businesses resident in a country, including those operating ships, aircraft and other transportation equipment in other countries.

Air emissions accounts also include households as consumers. Their emissions are accounted for whenever household consumption is directly responsible for environmental pressures. For example, emissions from a privately owned car are counted under households, whereas cars owned by transport businesses (such as taxis) are counted under transport services.

The following activity groupings are used in this article:

agriculture, forestry and fishing — NACE Rev. 2 Section A;
mining and quarrying — NACE Rev. 2 Section B;
manufacturing — NACE Rev. 2 Section C;
electricity, gas, steam and air conditioning supply — NACE Rev. 2 Section D;
transportation and storage — NACE Rev. 2 Section H;
other services, water supply and construction — NACE Rev. 2 Sections E to G and I to U, in other words all remaining economic activities as defined in NACE;
households — households as consumers.

Three perspectives of emission statistics for air pollutants

Eurostat presents three perspectives of emission statistics for air pollutants:

Perspective	Statistical framework	Purpose	Related data set	Related SE article
1. Emissions of air pollutants classified by economic activities	Air Emissions Accounts (AEA) by Eurostat	tailored for integrated environmental-economic analyses	env_air_aa	this article
2. Emissions of air pollutants classified by technical processes	Emission inventories for air pollutants by UNECE (United Nations Economic Commission for Europe)	official international reporting framework for CLRTAP (Convention on Long-range Transboundary Air Pollution)	env_air_emis	link
3. 'footprints' = Greenhouse gas (GHG) emissions classified by final use of products	Modelling results published by Eurostat	one particular analytical application of AEA	env_ac_io10	not available

Emissions accounts versus emission inventories

The main differences between air emissions accounts (AEA) and emission inventories for air pollutants are:

Air emissions accounts – air pollutants (residence principle)	Emission inventories for air pollutants (territory principle)
Emissions are assigned to the country where the economic operator causing the emission is resident.	Emissions are assigned to the country where the emission takes place
Emissions are classified by economic activity, following the NACE classification of the system of national accounts.	Emissions are assigned to processes classified according to their technical nature (e.g. combustion in power plants, solvent use).
Emissions from international navigation and aviation are assigned to the countries where the operator of the ship/aircraft is resident, regardless of where the emission takes place.	Emissions from international navigation and aviation are assigned to the countries where the associated fuel is bunkered, irrespective of the operator's place of residence.

Note: National and EU totals differ between the two approaches, as different boundaries apply. GHG inventories include international aviation and maritime transport (international bunker fuels) as memorandum items, which means that they are excluded from national totals reported. However, they are included in air emissions accounts totals. Therefore total emissions reported in GHG inventory databases can differ significantly from the total reported in air emissions accounts for countries with a large international aircraft and/or shipping fleet. AEA reconciles totals with emission inventories through 'bridging items'.

Context

The need to supplement information on the economy with environmental indicators has been recognised in a European Commission Communication titled 'GDP and beyond' (COM(2009) 433). Furthermore, similar recommendations have been made within the Report by the Commission on the Measurement of Economic Performance and Social Progress,the so-called Stiglitz report. The recommendations support the expansion of the statistical understanding of human well-being by supplementing economic indicators such as GDP with additional information, including physical indicators related to the environment.

Air emissions accounts measure the interplay between the economy and the environment with respect to air emissions, in order to assess whether current production and consumption activities are on a sustainable path of development. Measuring sustainable development is a complex undertaking as it has to incorporate economic, social and environmental indicators. The data obtained from air emissions accounts may subsequently feed into political decision-making, underpinning policies that target both continued economic growth and sustainable development, for example, the European Commission's latest initiative, the European Green Deal.