To be able to model air quality in 2030 for the Nordic countries as well as the contribution of emission sectors to air quality, Aarhus University has setup and applied the regional scale air quality model (DEHM) and the local scale urban air quality model (UBM) for the selected cities in the Nordic countries. Further, to address health impacts and related external costs we set up and applied the integrated modelling system – EVA (Economic Valuation of Air Pollution). Aarhus University has developed all these models.
Emissions for Europe and the rest of the Northern Hemisphere are based on emission data from the EMEP database with 0.1 x 0.1 degrees resolution and the ECLIPSE v6b database with 0.5 x 0.5 degrees resolution. Furthermore, global ships emissions are based on the STEAM model with 0.1x0.1 degrees spatial resolution and monthly time resolution.
Projected emissions for 2030 are drawn from existing international emission databases. For EU countries, emissions reflect national projections if targets are met in the NEC directive (National Emission Ceilings), otherwise they reflect reduction targets set out in the NEC directive for 2030 for the country. For non-EU-countries, the national projections are used.
Emissions for the Nordic countries are based on the emission dataset from the research project NordicWelfAir (funded by NordForsk) that for the first time established a high-resolution geographically distributed emission inventory of 1 km x 1 km for the Nordic countries for selected years from 1990 to 2014. The emission inventory for 2014 has been scaled to 2019 and 2030 based on the total of the country specific emission sectors and assuming a geographic distribution as in 2014.
The year 2019 serves as a reference year where model results are compared with measurements from monitoring stations in the selected cities to evaluate the performance of the air quality models.
Meteorological data are obtained from the Weather Research and Forecasting model (WRF), operated at Aarhus University.
1.3 Main conclusions and results
1.3.1 Evaluation of air quality monitoring in 2021
WHO AQ guidelines and the EU AQ Directive
WHO has tightened their air quality guidelines from 2005 to 2021 for the three pollutants that pose the largest health burden (PM2.5, NO2 and O3). The WHO Air Quality Guidelines (AQG) are much lower than in the present EU Air Quality Directive, and also lower than the proposed revised EU Air Quality Directive from October 2022. However, the proposed EU Air Quality Directive will eventually align with WHO guidelines for annual PM2.5 (5 µg/m3) and annual NO2 (10 µg/m3) for the average exposure concentration measured at urban background stations. This is to be achieved with continuous requirement for reduction in concentrations until the target is met. In 2030, a 25% reduction has to be met over a ten-year period, and the same the following years until the target is met.
Present air quality in Nordic countries and WHO guidelines
A comparison between measurement data from 2021 (extracted from the EEA database European Air Quality Portal) and the former and new WHO AQG, has been carried out for each of the Nordic countries where the maximum value at any measurement station within the country is compared with the WHO guidelines. This provides an overview of exceedances of the new WHO guidelines in the Nordic countries. Furthermore, it also describes how the exceedances have changed between the former and new WHO guidelines.
The health impacts of air pollution are by far the largest for long-term exposure to PM2.5 then followed by NO2, both as annual means, and then exposure to elevated levels of ozone. All five Nordic countries exceed the 2021 WHO AQG for annual means of PM2.5 and NO2, and also ozone (8h peak season) based on the highest measured values in 2021 (except Iceland for peak ozone as data is not available). More exceedances were observed in 2021 compared with 2005 as the WHO guidelines were tightened from 2005 to 2021.
Present air quality in selected cities
An analysis was carried out based on available measurements of NO2 and PM2.5 in 2021 from rural, urban background and street stations in the selected cities and the new WHO guidelines and the proposed EU Air Quality Directive. This analysis gives an indication of the concentration contribution of the cities (difference between urban background and rural concentrations) and further the contributions of hotspots (difference between street concentrations and urban background concentrations). For each of the selected cities the one station with the highest concentration measured, is representing that particular city.
In general, the measurements of NO2 and PM2.5 in 2021 are following the expected concentration pattern with the highest values represented by the traffic stations and the lowest seen at rural background stations with suburban/urban background in-between.
In all the selected cities in the five Nordic countries, annual NO2 and PM2.5 in 2021 are well below the annual limit values (40 μg/m3 and 25 μg/m3, respectively) of the current EU Air Quality Directive. In relation to the newly proposed EU Air Quality Directive limits of 20 μg/m3 and 10 μg/m3 for NO2 and PM2.5, respectively, 9 out of 13 traffic stations are exceeding the proposed annual limit value for NO2 and only one for PM2.5. None of the urban or rural background stations are exceeding the annual limit values of NO2 and PM2.5 of the newly proposed directive.
When it comes to the new 2021 WHO guidelines for annual NO2 (10 μg/m3), all the traffic stations show higher concentrations than the guideline levels. The same applies to annual PM2.5 (5 μg/m3). For the urban background stations, 6 out of 12 are exceeding the NO2 guideline levels. For PM2.5, 8 out of the 10 are exceeding the guideline levels. For NO2 measured in the rural background, all the stations with measurements are well below the guideline levels. For PM2.5, however, for the rural background stations 3 out of 9 with measurements are exceeding the guideline levels.
General implications of proposed AQ Directive
The overall implications for the Nordic countries of the proposed new EU Air Quality Directive have been analysed.
Measurements
In relation to the present EU Air Quality Directive and the general improvements in the air quality in the Nordic countries over the past 10 years, a comprehensive reorganization would be expected to take place of the air monitoring programmes with cheaper methods and fewer measuring points. However, the new proposal for the EU Air Quality Directive radically changes this possibility, since the tightening of the limit values is accompanied by more stringent assessment thresholds used to determine the number of measuring points and the requirements for the measurement methods.
It is further a requirement to measure ultrafine particles (UFP) and the size distribution of UFP.
There are also increased requirements for documentation of spatial representativeness of measurements and design of the measurement program.
Establishment of supersites
The new proposal for the EU Air Quality Directive requires the establishment of supersites with the aim to increase knowledge about particle pollution at EU level. Supersites require the measurement of a large number of new particle components, of which a requirement to measure the oxidative potential of PM is something completely new in the context of air quality monitoring.
New requirements for average exposure concentrations
The proposed new EU Air Quality Directive introduces a strengthening of the requirements for reducing the average exposure concentration for PM2.5 based on measured urban background concentrations and introduces similar requirements for NO2 that gradually will align with the WHO AQG.
Requirement for air quality modelling
The new proposal for the EU Air Quality Directive includes model calculations as an obligatory element where concentrations of pollutants exceed limit values, or target values. Furthermore, short-term air quality forecasts shall be carried out. Additionally, designated reference model institutions have to be appointed and participate in periodical model reviews and international model intercomparison exercises.
Public information on actual air quality and an Air Quality Index
The proposal for a new air quality directive imposes significantly stricter requirements on information on current air quality including obligatory hourly updates. It is also a requirement to establish an air quality index, and provide short-term air quality forecasts based on modelling.
1.3.2 Regional concentrations compared with the WHO AQG
Nordic emissions in 2019 and 2030
SNAP7 (road transport) contributes the most to NOx emissions in 2019 but decreases towards 2030 where other sectors also contribute significantly. SNAP2 (residential combustion=wood stoves) is an important contributor to PM2.5 emissions, except for Iceland. The combined sectors of SNAP1 (energy), 3 (industrial combustion) and 4 (industrial processes) are the emission sectors that contribute the most to SOx, except for Iceland where it is the combined sector of SNAP5 (extraction etc.), 6 (solvents) and 9 (waste) where SOx from geothermal energy and power production contributes by far the most allocated to SNAP5. The majority of SOx in Iceland is hydrogen sulfide (H2S).
There is a downward trend for emissions for all countries and pollutants from 2019 to 2030.
Regional concentrations in 2019 and 2030
The DEHM model was used to model regional background concentrations in 2019 and 2030 in the model domain of the Nordic countries in order to compare with the WHO AQG from 2021.
For annual NO2, there is a gradient from south to north with higher concentrations in Denmark and Southern Sweden. It is clear that the concentrations in most areas of the domain are lower than the WHO guideline (10 µg/m3), except for a few big cities. Ship emissions are also shown to cause elevated concentrations along ship lines, and at big harbors. There is a general decrease in NO2 concentrations from 2019 to 2030. Five of the selected cities are exceeding the WHO guideline in 2019: København, Trondheim, Stockholm, Oslo and Reykjavík, and only Reykjavík in 2030.