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The average exposure indicator (AEI) for PM2.5 assesses the general population’s long-term exposure to fine particles in urban areas and is based on a 3-year average measured at urban background stations. For instance, the AEI in year 2023 is the average of years 2023, 2022 and 2021.

There are two standards linked to the AEI in AAQD 2008/50/EC, that apply to the EU-27, Iceland and Norway:

  • The exposure concentration obligation (ECO) of 20µg/m3, set as a 2015 target. All countries met the ECO in 2023.
  • The national exposure reduction target (NERT), set for 2020. It uses as a reference, base AEI, the AEI in 2010 (defined either as the average 2008-2010 or 2009-2010) or, alternative, the AEI in 2011 (average 2009-2011). The exception is Croatia, which joined the EU in 2013 and has 2015 as the base year for AEI. In 2023, all countries met the NERT.

From 2020 on, to fulfil with the NERT, the AEI of the corresponding year must be (1) below a percentage of that base AEI and this percentage depends on the base AEI and ranges from 0 to 20%; or (2) at maximum 18μg/m3 when the initial concentration was above 22µg/m3.

Since the NERT compares the situation in the most recent years with that in the base years, it can be used as a proxy indicator of the improvement at national level of the urban concentrations of fine particles (PM2.5).

Achievement of the ECO and the NERT does not imply that there are no significant health impacts. The data here are presented only as an indicator of improvement over time.

Figure 6. Reduction in AEI 2023 in relation to the base AEI and distance to the NERT

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A comparison of the orange and blue bars in Figure 6 indicates reductions in the urban concentrations as presented in Table 3.

Table 3. Base AEI value, 2023 AEI value and percentage of reduction between those values

COUNTRY

BASE AEI, µg/m3 (years)

2023 AEI, µg/m3

Reduction (%) in urban concentrations

Austria

17.8 (2009-2011)

9.9

44.4

Belgium

19.0 (2009-2011)

9.8

48.4

Bulgaria

36.0 (2008-2010)

15.6

56.7

Croatia

20.6 (2013-2015)

14.4

30

Cyprus

21.5 (2009-2011)

14.4

33

Czechia

26.6 (2009-2011)

12.2

54.1

Denmark

14.0 (2008-2010)

7

50

Estonia

5.9 (2009-2011)

4.6

22

Finland

8.3 (2009-2011)

5.3

36.1

France

17.3 (2009-2011)

9.3

46.2

Germany

16.0 (2008-2010)

9.5

40.6

Greece

17.0 (2008-2010)

13.3

21.8

Hungary

21.0 (2009-2010)

13.9

33.8

Iceland

10.8 (2008-2010)

4.4

59.6

Ireland

10.2 (2009-2011)

1

90.2

Italy

19.9 (2009-2011)

13.9

30.1

Latvia

18.0 (2008-2010)

9.9

45

Lithuania

12.3 (2009-2011)

7.3

40.7

Luxembourg

17.4 (2009-2010)

6.7

61.5

Malta

13.2 (2009-2011)

10.9

17.4

Netherlands

17.0 (2009-2011)

8.7

48.8

Norway

10.0 (2009-2011)

6.3

37

Poland

26.9 (2010-2011)

16

40.5

Portugal

9.7 (2008-2010)

7.5

23.1

Romania

18.4 (2009-2011)

14

23.9

Slovakia

24.4 (2009-2011)

15.2

37.7

Slovenia

21.7 (2009-2011)

14.0

35.5

Spain

14.1 (2009-2011)

11.1

21.3

Sweden

6.6 (2009-2011)

5.1

22.7

Notes: Third column indicates the AEI reported by countries corresponding to the average 2021-2023. It is below 20µg/m3 in all cases, indicating fulfilment of the ECO. The fourth column expresses the reduction of the AEI between the base year and 2023. It is below the corresponding reduction target for each country, indicating fulfilment of the NERT.

Source: Air Quality e-Reporting database (EEA, 2025a).

In 2020, the first year the NERT should have been met, 22 Member States already met the reduction target. All EU-27 Member States met the NERT in 2022 and 2023. Furthermore, all countries included in the table have reduced exposure of their urban population to fine particles by at least 17% at a national level. Six countries have at least halved levels of exposure.

These reductions are in line with the decreases in annual mean PM2.5 concentrations at station level between 2008 and 2021(ETC HE, 2023). All (decreasing) trends are significant and reach 51% at all urban sites considered. Furthermore, for urban sites, the PM2.5 relative change between 2008 and 2021 is -37% and the decreasing trend in PM2.5 concentrations is seen in all European countries. Notwithstanding these improvements, 94% of the EU urban population remains exposed to PM2.5 concentrations above the WHO guideline values, highlighting the need for additional measures.

Box 1. New methodologies in the revised directive

The revised directive (EU, 2024) has introduced methodological changes in the average exposure reduction (AEI) obligations:

  • Inclusion of NO2 in addition to PM2.5.
  • Modified calculation of the AEI: all sampling points in urban background locations to be used for the calculation. Instead of assessments at a national level, the calculation will be done using average exposure territorial units.
  • Exposure concentration obligation (ECO) is now the average exposure concentration objective, in line with the WHO annual guidance value (WHO, 2021) but for which no attainment deadline has been established.
  • The NERT has been replaced by the average exposure reduction obligation, defined as a percentage of the reduction to be achieved from 2030, when comparing the annual AEI with the AEI 10 years before. This change in the calculation implies that Member States must keep reducing their levels as the reference concentration is not a fixed year.

Concentrations have improved across all Member States over the years, as shown in the main text. Yet only three countries in Table 3, Ireland, Iceland and Estonia, had in 2023 average exposure indicator levels below the annual WHO guideline value for PM2.5, 5µg/m3. This has now been set as the average exposure concentration objective from 2030 onwards.