Aarhus Universitets segl

No. 533: Air quality 2021. NOVANA

Ellermann, T., Nordstrøm, C,, Brandt, J., Christensen, J., Ketzel, M., Massling, A., Bossi, R., Frohn, L.M., Geels, C., Jensen, S.S., Nielsen, O.K., Winther, M., Poulsen, M.B., Monies, C., Sørensen, M.B., Andersen, M.S. og Sigsgaard, T. 2023. Luftkvalitet 2021. Status for den nationale luftkvalitetsovervågning. Aarhus Universitet, DCE – Nationalt Center for Miljø og Energi, 219 s. - Videnskabelig rapport nr. 533. http://dce2.au.dk/pub/SR533.pdf


This report presents results for 2021 from the Danish monitoring of air quality with focus on the health related effects of air pollution. The air quality monitoring program covers the entire Denmark. However, the monitoring program has special focus on cities, where air pollution and population density are highest. DCE – the Danish Center for Environment and Energy at Aarhus University carries out the monitoring program on behalf of the Danish Ministry of Environment in cooperation with the municipalities of Copenhagen, Odense, Aarhus and Aalborg.

The aim of the monitoring program is to:

  • document the state of the air quality in relation to EU’s air quality limit and target values,
  • determine the long-term trends for the air quality in order to evaluate the impact of the Danish and international measures taken to reduce air pollution,
  • warn the Danish public when EU’s warning thresholds are exceeded. In Danish context this is only relevant for ozone, and
  • determine the health effects and external costs of air pollution in Denmark and perform detailed model calculations of the emission sources leading to air quality related health effects and external costs (additionally financed by the Danish Ministry for the Environment).

The monitoring of air quality is based on an integration of measurements and model calculations. The measurements are carried out at nine monitoring stations in the four largest cities in Denmark, one suburban monitoring station in Hvidovre and four regional background monitoring stations placed on the countryside. The model calculations are carried out using DCE’s suite of internationally recognised air quality models.

The monitoring program covers the most relevant air pollutants that have impact on human health and those that are covered by the EU air quality directives (EU, 2004; EU, 2008). The program includes measurements of sulphur dioxide (SO2), nitrogen oxides (NOx/NO2), particles with diameters less than 10 and 2.5 micrometers respectively (PM10 and PM2.5), particle number, elementary carbon (EC), organic carbon (OC), benzene (C6H6), toluene (C7H8), carbon monoxide (CO), ozone (O3), polycyclic aromatic hydrocarbons (PAH), a number of heavy metals including lead (Pb), arsenic (As), cadmium (Cd), mercury (Hg), nickel (Ni), and finally a number of volatile organic compounds (VOCs) that are precursors to formation of ozone.

Emission inventories

This report presents an overview of the emissions of air pollutants from Danish and European sources. This overview includes 2020 emissions, which is the most recent reporting year. An overview of the long-term trends of the emissions is likewise covered. The aim of this overview is to facilitate the interpretation of monitoring results, i.e. explaining the spatial variability and long-term trends of the different air pollutants.

Data on emissions from Danish sources are obtained from the official national emission inventories prepared by DCE for the Danish Ministry of Environment (Nielsen et al., 2021). Emission data from the remaining EU member states are obtained from the European emission database (EMEP) (CEIP, 2023).

The sources of emissions of air pollutants vary considerably among pollutants. Figure 1 and 2 present the contributions from the different main categories of emission sources for different air pollutants. The emission inventories only cover the directly emitted particles and not particles formed via chemical reactions in the atmosphere.

Since 1990, there have been significant reductions in the Danish emissions for most air pollutants. The largest reductions are for the emissions of lead and sulphur dioxide that have been reduced with about 90%. Carbon monoxide, arsenic, nickel and chromium emissions have been reduced with 70-86%. Nitrogen oxides and black carbon emissions have been reduced with 65-70%, while emissions of fine particles (PM2.5), benzo[a]pyrene, non-methane volatile organic compounds and cadmium have been reduced with 45-50%. Emissions of larger particles (particles between 2.5 and 10 µm) and zinc have only been reduced slightly and for copper there has been an increase of about 30% in the emissions from 1990 to 2019 followed by a reduction of about 10% from 2019 to 2020 mainly due to covid 19 restrictions. The long-term trends reflect the measures that have been taken to reduce the various emissions as well as changes in the activities that are responsible for the emissions.