Aarhus Universitets segl

No. 410: Air quality 2019

Thomas Ellermann, Claus Nordstrøm, Jørgen Brandt, Jesper Christensen, Matthias Ketzel, Andreas Massling, Rossana Bossi, Lise Marie Frohn, Camilla Geels, Steen Solvang Jensen, Ole-Kenneth Nielsen, Morten Winther, Maria Bech Poulsen, Jesper Nygaard og Jacob Klenø Nøjgaard. 2020. Luftkvalitet 2019. Status for den nationale luftkvalitetsovervågning. Aarhus Universitet, DCE – Nationalt Center for Miljø og Energi, 128 s. - Videnskabelig rapport nr. 410. http://dce2.au.dk/pub/SR410.pdf



This report presents results for 2019 from the Danish monitoring of air quality with focus on the health related effects of air pollution. The air quality monitoring program covers entire Denmark. However, the monitoring program has special focus on the cities, where the air pollution and population density is highest. DCE – the Danish Center for Environment and Energy (DCE) at Aarhus University carries out the monitoring program on behalf of the Danish Ministry for the Environment in cooperation with the municipalities of Copenhagen, Odense, Aarhus and Aalborg.

The aim of the monitoring program is to:

  • ocument actual 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 be able 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 and external economic effects of air pollution in Denmark. This year, this includes detailed model calculations of the sources of the health and external economic effects (additionally financed by the Danish Ministry for the Environment).

The monitoring of the 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 outside the cities. 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 (PAHs), 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

As a new feature, this report includes an overview of the emissions of air pollutant from Danish and European sources. This overview presents a status for the emissions in 2018 that is the most recent reporting year. It includes also an overview of the long-term trends of the emissions. The aim of this overview is to facilitate the interpretation of monitoring results i.e. the reasons for the spatial variability and long-term trends of the different air pollutants.

Data on the emissions from the Danish sources are from the official national emission inventories prepared by DCE for the Ministry of the Environment (Nielsen et al., 2020) and the European emission database covering the emissions from all EU member states (CEIP, 2020).

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

Since 1990, there have been significant reductions in the Danish emissions for most of the air pollutants. The largest reductions are for the emissions of lead, sulphur dioxide and arsenic that have been reduced with about 90%. Nickel and chrome have been reduced with 70-80%. Nitrogen oxides, black carbon and carbon monoxide have been reduced with about 60% while the fine particles (PM2.5), benzo[a]pyrene, non-methane volatile organic compounds and cadmium have been reduced with 40-50%. The larger particles (particles between 2.5 and 10 µm) and zinc have only been reduced slightly and for cobber there has been an increase of about 30%. The long term trends reflects the measures that have been taken in order to reduce the various emissions and  changes in the activities that are responsible for the emissions.

Actual state and long term trends for the air quality

The permitted number of exceedances in a year of the diurnal limit value of 50 µg/m3 for PM10 was not exceeded at any monitoring station in the monitoring network. Likewise, there were no exceedances of the annual limit values for PM10 (40 µg/m3) and PM2.5 (25 µg/m3). The Average Exposure Indicator (AEI) determined as a running three-year average of the average urban background concentration of PM2.5 has decreased with about 30 % since 2010 and hence the target (15 % reduction) has been reached.   The annual average concentrations of PM2.5 and PM10 has decreased with 20-40% since 2007/2008 and 35-45% since 2001, respectively.

Due to continued technical difficulties with two new instruments, it has not been possible to measure the number of particles between 11 and 41 nm in 2017-2019. Therefore, the particle number represents the particle range from 41 to 478/559 nm (dependent on instrument version but the difference is negligible). The particle number in ambient air was about 3,400 particles per cm3 as an annual average at the street monitoring station at H.C. Andersens Boulevard. This is roughly a factor of two higher than in suburban areas and in urban and rural background. Since 2002, a significant reduction of about 65 % in particle numbers has been observed. This reduction has mainly been attained by reduction of traffic emissions (cleaner fuel, particle filters etc.).

The limit values for nitrogen dioxide was not exceeded at any of the monitoring stations in Denmark. Model calculations at 98 selected street segments in Copenhagen and 26 selected street segments in Aalborg in 2019 showed likewise no exceedances of the long-term limit value based on the annual average concentration. The annual average concentrations of nitrogen dioxide at the street monitoring stations has been reduced with about 50% since 2005.

In 2019, the annual average ozone concentrations were at the same level as in the previous years. No clear trend is observed for the average ozone concentration during the last years. The target value states that the maximum daily 8-hours mean ozone concentration must not exceed 120 µg/m3 more than 25 times annually as average for three years. The target value was not exceeded at any of the monitoring station, but the long-term objective for this parameter was exceeded at all Danish stations (maximum daily 8-hours mean ozone concentration must not exceed 120 µg/m3). The target value entered into force in 2010 while the long-term objective has not entered into force and the date for this has not yet been decided. The information threshold of 180 µg/m3 was exceeded once at monitoring stations on Zealand and Funen.

Measurements of volatile organic compounds at the urban background monitoring station in Copenhagen showed concentration levels between 0.02 µg/m3 and 0.7 µg/m3 for the selected 17 different compounds. Volatile organic compounds can act as precursors for the formation of ozone, and the aim of these measurements is to improve the general understanding of the ozone formation at a European level. The formation of ozone in Denmark is in general small due to moderate solar radiation. Ozone pollution in Denmark is mainly the result of long-range transport of pollutants from other European countries south of Denmark. The annual average concentrations for most of the measured volatile organic compounds have been reduced significantly since 2010.

Measurements of the concentrations of particle bound polycyclic aromatic hydrocarbons were performed at H.C. Andersens Boulevard, Copenhagen and at the suburban monitoring station at Hvidovre. The annual average concentrations of benzo[a]pyrene were 0.25 ng/m3 and 0.28 ng/m3 at H. C. Andersens Boulevard and Hvidovre, respectively. The target value for benzo[a]pyrene (1 ng/m3) was not exceeded in 2019. The annual average concentrations have been reduced with about 40% at H.C. Andersens Boulevard since 2008.

The levels of sulphur dioxide, heavy metals have decreased for more than two decades and the concentrations are now far below the limit values. The limit values for benzene and carbon monoxide are not exceeded and the levels have been decreasing for the last decades.

Figure 3 gives an overview of the air quality in Denmark in relation to the EU limit and target values.

As a new feature, this report presents results from a detailed analysis of the chemical content of PM2.5 in regional backgrund at Risø/Roskilde, urban background in Copenhagen and at the most polluted street monitoring station in Denmark (H.C. Andersens Boulevard, Copenhagen). This analysis shows that only about 25% of PM2.5 at H.C. Andersens Boulevard originates from sources in Copenhagen, while about 75% of PM2.5 originates from sources in foreign countries and sources in the remaining part of Denmark.

Health effect and external economic cost of air pollution in Denmark

Model calculations show that air pollution causes about 4,600 premature deaths in Denmark in 2019 and a large number of other negative health effects. This is about 10% more compared to the reporting for 2018. This higher number of premature deaths are due to updates in the emission inventories, meteorological data and an improved method for calibration of the model calculations. The higher number is therefore not due to higher air pollution. Recalculations of the entire data series back to 1990 shows a decrease in the health effects due to air pollution. In 1990, about 8,200 premature deaths were due to air pollution in Denmark and this number has decreased with about 43% to 4,600 premature deaths in 2019.

The total health related external costs for Denmark have been calculated to 85 billion DKK for 2019 (in 2016-prices). The cost was about 115 billion DKK in 1990 and hence the cost has decreased with about 25% since 1990.

A detailed analysis of the source of the health effects and external costs in Denmark have been carried out in connection to this reporting. This analysis shows that about 1,100 premature deaths are due to emission of air pollution in Denmark. This corresponds to about 24% of the total number of premature deaths. The remaining 76% are due to emissions outside Denmark. The same pattern is seen for the external costs. The model calculations shows also that Danish sources are responsible for about 2,000 premature deaths in foreign countries.

Figure 4 shows the contributions from the main source categories to the number of premature deaths in Demark. The most important Danish source are non-industrial combustion (mainly household warming based on wood burning) that are responsible for about 440 premature deaths in Denmark corresponding to 39% of the total number of premature deaths due to Danish sources.

The contribution from Danish sources accounts for a much lower share when the number of premature deaths are seen relative to the entire air pollution in Denmark. This is because the Danish sources only account for about 24% of the number of premature deaths due to the entire air pollution in Denmark. Table 1 presents the relative contributions from Danish sources calculated relative to both the number of premature deaths from Danish sources and relative to the number of premature deaths from the entire air pollution in Denmark.

The health effects and external costs from cruise ship emissions in Copenhagen and Aarhus has been calculated. These calculations show that cruise ship emissions are responsible for three premature deaths annually and external costs of around 50 million DKK.

The uncertainties on the calculations of health effects and external costs are significant. Leading international researchers have estimated that the uncertainties on their calculations are about ±50% (Lelieveld et al., 2019). DCE estimates that the uncertainties on the model calculations of health effects and external costs presented in this report are on the same level.

As a final remark, it is noticed that the Danish Energy Agency on 9 December 2020 has published their status on energy consumption in Denmark in 2019 (https://ens.dk/service/statistik-data-noegletal-og-kort/maanedlig-og-aarlig-energistatistik). Here, the Danish Energy Agency has revised the statistics for wood combustion. The revised data shows that the annual wood combustion decreases with 35% from 2016 to 2019, which is a much larger decrease than previously. It has not been possible to include these new data in this report since the model calculations was carried out before December 2020. As a consequence, the presented results for the emissions and health impacts from wood combustion is most likely overestimated. The changes in the use of wood combustion will be included in the calculations for the coming reporting for 2020.