Sweden is one of the countries in Europe which experiences the lowest concentrations of air pollutants in urban areas. However, the health impact of exposure to ambient air pollution is still an important issue in the country and the concentration levels, especially of nitrogen dioxide (NO 2) and particles (PM10,) exceed the air quality standards and health effects of exposure to air pollutants in many areas.
IVL Swedish Environmental Research Institute and the Department of Public Health and Clinical Medicine at Umeå University have, on behalf of the Swedish EPA and the health-related environmental monitoring programme, performed a health impact assessment (HIA) for the year 2005. The population exposure to NO 2 in ambient air has been quantified (annual and daily mean concentrations) and the health and associated economical consequences have been calculated based on these results.
The results from the urban modelling show that in 2005 most of the country had low NO 2 urban background concentrations compared to the environmental standard for the annual mean (40 μg/m3). In most of the small to medium sized cities the NO2 concentration was less than 15 μg/m3 in the city centre. In the larger cities and along the Skåne west coast the concentrations were higher, up to 20-25 μg/m3, which is of the same magnitude as the long-term environmental objective (20 μg/m3 as an annual mean).
Almost 50% of the population were exposed to annual mean NO 2 concentrations of less than 5 μg/m3. A further 30% were exposed to concentration levels between 5-10 μg NO2/m3, and only about 5% of the Swedish inhabitants experienced exposure levels above 15 NO2 μg/m3.
The health impact calculation has four components: a relevant effect estimate from epidemiologic data, a baseline rate for the health effect, the affected number of persons and their estimated "exposure" (here pollutant concentration). We have used 10 μg/m 3 as a lower cut off in our impact assessment scenarios for long-term exposure and mortality as well as in the assessment of short-term effects on hospital admissions. Exposure above 10 μg/m3 is therefore defined as excess exposure resulting in "excess cases".
For our mortality assessment we have chosen to use the same estimate as in our previous similar HIA. The estimate came from a study in Auckland, and was 13% (95% CI: 11–15%) increase in non-external mortality per 10 μg/m
3 increase in annual average NO2. This estimate is similar to what has been reported in some other referenced studies.
For respiratory hospital admissions we have used the risk estimates from a Norwegian study reporting a relative risk of 2.9% per 10 μg/m3. For cardiovascular hospital admissions we have used a meta-analysis presented by an expert group in UK, assuming a relative risk of 1.0 % per 10 μg/m3 in the health impact assessment.
Altogether we estimate that concentations of NO2 in urban air resulted in more than 3200 excess deaths per year. Almost 600 of these could have been avoided if annual mean concentrations above the environmental goal 20 μg/m3 did not exist. Most excess deaths are estimated to occur due to annual levels in the range of 10-15 μg/m3. We have crudely estimated the average years of life lost per excess death to be just over 11 years. In addition we estimated more than 300 excess hospital admissions for all respiratory disease and almost 300 excess hospital admissions for cardiovascular disease due to the short-term effect of levels above 10 μg/m3.
The health effects related to high concentrations of NO 2 in ambient air are related to socio-economic costs, as are the costs for abating these high concentrations. It is important for decision 2 Quantification of population exposure to nitrogen dioxide IVL report B 1749 makers to use their economic resources in an efficient manner, which furthermore induces the need for assessments of what can be considered as an efficient use of resources. The socio-economic costs related to high levels of NO 2 in air are derived from the cost estimates of resources required for treatment of affected persons, productivity losses from work absence and most prominently from studies on the social Willingness To Pay for the prevention of health effects related to these high levels of NO2.
In our study we have applied results from international socio-economic valuation studies to our calculated results on increased occurrences of hospital admissions and fatalities. The values from the studies have been adapted to Swedish conditions. The application of international results favours comparison with other estimates on economic valuation of health effects related to high levels of NO 2.
The results suggest that the health effects related to annual mean levels of NO 2 higher than 10 μg / m3 can be valued to annual socio-economic costs of 18.5 billion Swedish crowns. These 18.5 billion Swedish crowns are to be considered as welfare losses. However, only 18 % of these costs are related to exceedance of the Swedish long term environmental objectives for NO2. The other 82 % of the costs are taken by the larger part of the Swedish population that are exposed to medium levels of NO2. This displacement in the distribution of the social costs indicates that the most cost effective abatement strategy for Sweden might be to reduce medium annual levels of NO2 rather than only focusing on abatement measures directed towards the highest annual mean levels.
The trend analysis between 1990 and 2005 clearly shows an increasing number of people exposed to lower NO 2 concentration levels. Comparing 2005 with 1990, about 15% less people were exposed to annual mean NO2 levels above 15 μg/m3, while almost 20% more people were exposed to annual mean NO2 levels in the lowest concentration class, 0-5 μg/m3.
In general, the improved URBAN model shows good performance. When using the actual weather instead of the normal weather the variability in air pollution concentrations governed by the meteorology is captured when applying the rather fine scaled meteorology. The difference between measurements and the calculated concentrations is less than 10%. It was determined that the use of normal year meteorology lead to much greater uncertainties and this method was therefore rejected.
The comparison between the URBAN model and detailed calculations on a regional scale shows a good agreement as regards the annual mean concentrations. For concentrations above the cut off level used in the exposure studies (10 μg/m 3) the agreement between the two calculation methods lies within 5%. On the local scale the population weighted annual means correlate very well with the URBAN model calculations in Göteborg and Uppsala. For Umeå there are larger differences. The comparison of the number of people exposed to different concentration levels corresponds quite well (within 15%) in Göteborg, but the differences are larger in the two other cities (up to 45%). This may be due to uncertainties in the concentration distribution pattern.
There are still a number of issues that can further improve the certainty of the calculations, i.e. the selection of population data to be used as well as application of relevant geographical areas and best degree of resolution to fit with the most valid epidemiological ER-functions. By increasing the asseessment frequency it is possible to minimize the uncertainties due to meteorological variations. Furthermore, the differences in exposure on the local level could be reduced if existing local dispersion concentration calculations were applied into the model.
2007. , 72 p.