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The main source of nitrogen dioxide (NO2) is road transport (EEA, 2024b), which emits NO2 close to the ground, mostly in densely populated areas. Other important sources are combustion processes in industry and energy supply.
Concentrations above the annual limit value were found in many Turkish cities and some other urban agglomerations with a high volume of traffic (Map 4 and Figure 10).
Map 4. Concentrations of NO2 in 2023 and 2024 in relation to the EU annual limit value and the WHO annual guideline level
Table 5. Summary country status for NO2 in 2023 and 2024
2023 | 2024 | |
|---|---|---|
Number of reporting Member States/other countries | 27/11(a) | 27/7(c) |
Number of Member States/other countries with at least one station > EU annual limit value (40µg/m3) | 8/1 | 6/1 |
Number of Member States/other countries with at least one station > EU hourly limit value (200µg/m3) | 0/1 | 1/0 |
Number of Member States/other countries with at least one station > WHO annual guideline level (10µg/m3) | 27/10(b) | 27/7 |
Number of Member States/other countries with at least one station > WHO daily guideline level (25µg/m3) | 27/10 | 27/6 |
Notes: (a) except for Kosovo under UNSCR 1244/99 for the WHO daily level, for which stations did not fulfil the requirement for minimum data coverage. (b) All reporting countries except Kosovo. (c) Except for Serbia for the WHO daily level, for which stations did not fulfil the requirement for minimum data coverage.
Source: Air Quality e-Reporting database (EEA, 2025a).
Figure 9. Percentage of reporting monitoring stations registering NO2 concentrations above EU limit values and WHO guideline levels
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In 2023, 2% of monitoring stations registered concentrations of NO2 above the EU annual limit value (Figure 9), 66% of which were traffic stations. Concentrations above the WHO annual guideline level for NO2 were registered at 70% of all monitoring stations, 47% of which were traffic stations.
In addition to data collected from monitoring stations, countries can also use modelling applications to assess compliance with the standards. Italy and Poland reported exceedances of the NO2 annual limit value for two and four air quality zones, respectively, based on assessment models.
Figure 10. NO2 concentrations in 2023 by country and in relation to EU annual limit values and WHO annual guideline level
In 2024, 1% of monitoring stations registered concentrations of NO2 above the annual limit value, all of which were traffic stations. 65% of monitoring stations registered concentrations above the WHO annual guideline level, 44% of which were traffic stations.