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No. 225: Health effects and related external costs of air pollution in Aarhus Municipality

Jensen, S.S., Brandt, J., Christensen, J.H., Ketzel, M. (2017): Helbredseffekter og relaterede eksterne omkostninger af luftforurening i Aarhus Kommune. Aarhus Universitet, DCE – Nationalt Center for Miljø og Energi, 76 s. - Videnskabelig rapport fra DCE - Nationalt Center for Miljø og Energi nr. 225. http://dce2.au.dk/pub/SR225.pdf

Summary

Background and Purpose

Air pollution has significant negative effects on human health and well-being with significant socio-economic consequences. The aim of the project is to calculate the health impacts and external costs related to air pollution in the Municipality of Aarhus with the integrated model system EVA (Economic Valuation of Air pollution), and quantify how much is due to the different sources of air pollution.

The study

Air Quality Assessment

An air quality assessment is carried out that describes the spatial distribution of background concentrations with a resolution of 1 km x 1 km, as well as street concentrations at address level in the Municipality of Aarhus. This description is based on data from a national data set, which is called Air Quality at Your Street (http://luftenpaadinvej.au.dk). Furthermore, a summary of the results from the two fixed measuring stations in Aarhus city shows the trends in concentrations for an urban background station (Botanical Garden) and a street station (Banegårdsgade).

Health impacts and related external costs

Health impacts and related external costs due to all air pollution are calculated for the entire municipality and separately for Aarhus city. All air pollution is due to sources from the Municipality of Aarhus and all other sources in Denmark and abroad. 

Moreover, calculations are carried out for each type of emission source in the Municipality of Aarhus to quantify the contribution of the different sources. In principle, the Municipality of Aarhus is able to regulate these sources. The calculations are carried out with the integrated assessment model system EVA (Economic Valuation of Air pollution (Brandt et al., 2011a,b; 2013a,b), which is based on the so-called impact-pathway method. The EVA-system calculates the health impacts and related external costs based on information about the sources of pollution and their location, the dispersion of air pollution as well as exposure of the population, the dose-response relationship between exposure and health effects, and the valuation of health effects, also referred to as external costs related to health effects from air pollution. 

Modelling of air quality is based on the regional air pollution model DEHM and the urban background model UBM resulting in calculations performed on a 1 km x 1 km grid resolution. Urban background concentrations are the general air pollution in the city and reflect the concentrations in a park, a backyard or at the roof of buildings. Urban background concentrations differ from street concentrations, which represent the concentrations in the height of 2 m at the facade of buildings. The year of calculation is 2014, which is the most recent year with updated emissions for Denmark on 1 km x 1 km resolution.

The EVA-system includes population data from 2008 with a spatial resolution of 1 km x 1 km. The rate of increase from the main statistical areas of the Municipality of Aarhus has been used to scale population data from 2008 to 2 014 in each grid cell using GIS analyses. For other grid cells outside the Municipality of Aarhus population data is projected from 2008 to 2014 using a single factor based on information from national statistics.

Main Findings

Air Quality Assessment for urban background concentrations

The highest urban background concentrations of NO2 are in Aarhus city with decreasing concentrations out into the suburbs. The major transport corridors have elevated concentrations. 

The Studstrup stations also contribute to the background concentrations in the surroundings where the background concentrations are comparable to that of Aarhus city, but street concentrations in the areas are much lower than in Aarhus due to modest local traffic.

The spatial distribution of urban background concentrations of PM2.5 and PM10 generally follows each other with high concentrations in Aarhus city, and around the Studstrup power station, but also in the southern part of the municipality with contributions from wood stoves. The contribution from local emission sources is less compared to NO2, since the range between mini-mum and maximum concentrations for particle concentrations are considerably smaller than for NO2, since the regional contribution of PM2.5 and PM10 is high. The contribution from the motorway E45 is not as evident as for NO2. 

Levels of all three substances are significantly below the limit values.

Air Quality Assessment for street concentrations

The limit value of annual mean concentrations is 40 µg/m3 for NO2. Calculations performed as part of Air Quality at Your Street may give an indication of whether or not the limit value is exceeded. Therefore, calculated exceedances are called indicative exceedances. The official announcement of exceedances of limit values is carried out as part of the annual reporting under the National Air Quality Monitoring Program, which is based on measurements from the Danish fixed monitoring stations (Ellermann et al., 2016).

29 indicative exceedances are calculated in Aarhus city of street concentrations for NO2 in 2012 with a maximum concentration of 48.4 µg/m3. Almost all the exceedances are along a single street section at the harbor area. One exceedance is at Ring Road 1 and Skanderborgvej where the limit value is barely exceeded (calculated value of 41 µg/m3). This indicates that exceedances may occur on few streets in Aarhus city, but it will require further studies to qualify this. 

Measurements of NO2 at Banegårdsgade in Aarhus city show a downward trend, where concentrations have decreased about 4 µg/m3 from 2012 to 2015 due to the ongoing renewal of the car fleet. Therefore, calculations from 2012 presented above are higher than levels in 2015 if re-calculated.

The geographical distribution of street concentrations for PM2.5 and PM10 as annual means in 2012 in the Municipality of Aarhus is very similar to each other because PM2.5 is part of PM10. As for NO2 the highest concentrations are in Aarhus city along the major roads. The limit value of annual mean concentrations of PM2.5 is 25 µg/m3 and 40 µg/m3 for PM10. The highest concentration of PM2.5 is 12.5 µg/m3 which is significantly below the limit value. PM10 with a maximum of 19.2 µg/m3 is also below the limit value.

Although the calculated street concentrations of PM2.5 and PM10 are underestimated compared with measurements from the 5 street stations in Denmark with -23% to-7% for PM2.5 and -36%-22% for PM10 (Jensen et al., 2017) no exceedances of the limit values for PM2.5 and PM10 are expected.

Emission inventory and source apportionment

The largest source of NOx emissions in the Municipality of Aarhus is road transport (SNAP07), while for particles it is wood stoves (SNAP0202). This is based on the national emission inventory which is geographically distributed in 1 km x 1 km grid cells. 

Source apportionment is the contribution of emission sources to the average urban background concentration in the Municipality of Aarhus. It is how many micrograms per cubic meter that the individual emission sources con-tribute to concentrations.

All emission sources in the Municipality of Aarhus contribute to 33% of the urban background NO2 concentration and the neighbouring municipalities contribute with 19%. This means that local sources contribute with 51%, while the other half is the contribution from regional air pollution (DEHM) and international maritime transport in the Bay of Aarhus. The largest source of emissions in the Municipality of Aarhus is road transport. 

The regional contribution represents 88% and 90%, respectively of urban background PM10 and PM2.5 concentrations, and all emission sources in the Municipality of Aarhus contribute with 12% and 10%, respectively. Wood stoves are the largest local contributor to particulate air pollution.

Premature deaths and morbidity

The total annual number of cases of premature deaths in 2014 is 206 in the Municipality of Aarhus due to all air pollution based on Danish and foreign emission sources. For Aarhus city it is 80. Premature deaths are due almost exclusively to so-called chronic deaths caused by long-term exposure to particulate pollution in contrast to so-called acute deaths due to shorter time periods with elevated concentrations (episodes) primarily due to ozone.

The people who die prematurely due to air pollution are especially elderly and vulnerable persons, as well as persons who already suffer from cardio-vascular and respiratory diseases. Deaths among infants represent a very small share. 

The number of premature deaths is calculated based on the number of years of life lost, where one premature death corresponds to 10.6 years of life lost. In addition to premature deaths, there are many cases of morbidity. It includes chronic bronchitis and discomfort for children and adults with asthma (use of bronchodilator, cough, and respiratory symptoms), hospital admissions related to respiratory disorders and blood clot in the brain, cases of heart failure, lung cancer, as well as many with reduced activity (sick days).

Health effects in the Municipality of Aarhus distributed on local emission sources

It is estimated how much the local emission sources in the Municipality of Aarhus contribute to health effects in the municipality. The purpose of these calculations is to quantify how much the local emission sources in the Municipality of Aarhus influence health effects in the municipality. The local emission sources in the Municipality of Aarhus contributes to about 16 premature deaths in the municipality, while all air pollution in the Municipality of Aarhus (from Danish and foreign sources) contributes to about 206 premature deaths. In other words, local emission sources in the Municipality of Aarhus contribute to about 8% of the total premature deaths in the Municipality of Aarhus, and about 92% of premature deaths in the Municipality of Aarhus are due to emissions outside the municipality. The main local sources causing the 16 premature deaths in the Municipality of Aarhus are wood stoves (about 8 premature deaths) and road transport (around 4 premature deaths). The same pattern can be observed for morbidity.

External costs due to all air pollution

The total external costs in the Municipality of Aarhus in 2014 due to all air pollution from Danish and foreign emission sources is about DKK 1.7 billion annually, of which about DKK 0.7 billion in Aarhus city. 

The external costs are almost entirely related to particles (DKK 1.6 billion), which here include primarily emitted particles, secondary inorganic particles (nitrate, sulphate, ammonium), and sea salt. A contribution has also been added based on measurements for secondary organic particles (SOA) and "unknown mass". Unknown mass is assumed, among other things, to be water bound to the particles. The external costs as a result of local sources in the Municipality of Aarhus are only from primarily emitted PM2.5, since secondary particles are not formed within the short transport distances within the Municipality of Aarhus.

The external costs related to ozone are about DKK 88 million in the Municipality of Aarhus of which DKK 36 million are attributed to Aarhus city. Ozone is not emitted directly but is formed in the atmosphere from emissions of NOx, hydrocarbons and CO. Ozone is harmful to health, and is therefore associated with external costs. Contribution from CO to the external costs is insignificant in comparison to the other substances. CO only contributes about DKK 0.5 million in the Municipality of Aarhus and about DKK 0.2 million in Aarhus city. The major part of the external costs is caused by premature deaths since the economic valuation of premature death is high compared to e.g. morbidity and sick days.

External costs due to local emission sources

The total external costs are about DKK 127 million in the Municipality of Aarhus due to emission sources in the municipality in 2014. The total external costs in the Municipality of Aarhus due to all air pollution from Danish and foreign emission sources were about DKK 1.7 billion. This means that local emissions in the Municipality of Aarhus contribute with about 8%. Conversely, about 92% of all external costs related to air pollution in the Municipality of Aarhus are due to emissions outside of the municipality.

Uncertainties

Impact pathway method

The EVA-system is based on the impact pathway approach covering emissions from sources, the dispersion and chemical transformation in the atmosphere, exposure of the population, health effects, and economic valuation of these health effects. There are uncertainties associated to all these elements further discussed in Chapter 9.