Quantification of population exposure to NO2, PM2.5 and PM10 and estimated health impacts
Air pollution concentrations in Swedish cities are among the lowest in Europe. Despite this, health impacts due to exposure to ambient air pollution is still an important issue and the concentration levels, especially of nitrogen dioxide (NO2) and particles (PM10 and PM2.5), occasionally exceed the air quality standards at street level in many urban areas. In this report presents a health impact assessment (HIA) for the year 2015. Den här rapporten finns endast på engelska. Svensk sammanfattning finns i rapporten.
IVL and the Department of Public Health and Clinical Medicine at Umeå University have, on behalf of the Swedish EPA, performed a health impact assessment (HIA) for the year 2015. The population exposure to annual mean concentrations of NO2, PM10 and PM2.5 in ambient air has been quantified, and the health and associated economic consequences have been calculated based on these results.
To allow application of known exposure-response functions for assessment of health effects this study exclusively focus on regional and urban background concentrations. Roadside concentrations are not addressed here. The results from this study show that background concentrations of the examined pollutants in 2015 were overall low, well below the environmental standards in most parts of the country. The background concentrations were also below the environmental objective for all examined pollutants, with the exception of a small stretch along the Swedish west coast and Skåne, where the particle concentrations were of the same magnitude as the environmental objective. It should be noted that a slight over-estimation of PM2.5 may occur in coastal regions due to the presence of sea salt which may affect the PM2.5/PM10 ratio used to calculate PM2.5 in this study.
Nearly the entire Swedish population was exposed to concentrations below the environmental standards, and 97%, 78% and 77% was exposed to concentrations below the respective specifications of the environmental objective for NO2, PM10 and PM2.5. Exposure to the highest concentrations was found in the most polluted central parts of our largest cities.
Comparing the results from this study to the 2010 assessment shows a slight increase in mean population exposure to NO2 and PM. For NO2, we also find a slight increase in the percentage of the population exposed to concentrations above the environmental objective. For PM, exposure to concentrations above the environmental objective was instead found to have decreased with up to 5%. Particle concentrations show a decreasing trend in Sweden, resulting in reduced exposure to the highest PM concentrations and an increased exposure to concentrations just below the environmental objectives. The slight increase in mean population exposure to PM can be explained by a growing population and ongoing urbanization, resulting in more people exposed to relatively high PM concentrations in the urban centres. While the contribution of local sources is minor for the smallest PM, it makes up the major part of NO2 concentrations in urban areas. The slight increase indicated for NO2 exposure is thus primarily connected to increased local emissions of NO2, due to, for example, increasing traffic and use of diesel vehicles. This, in combination with the ongoing urbanization, results in a growing number of people living in areas with higher concentrations.
Excess mortality is usually the main health indicator. We estimate approximately 3600 deaths per year associated with exposure to regional background (long-distance transported) concentrations of PM2.5. On average each premature death represents over 11 years of life lost. The total exposure to PM2.5 was recently in an EU report estimated to cause just over 3700 deaths per year in Sweden when no differences between sources and no threshold for effects were assumed. We assume that locally emitted particles (road dust, wood smoke and exhaust particles) have different effects on mortality, but face problems to find specific exposure-response functions. This is even more striking regarding effects on morbidity. Acknowledging the uncertainty, we estimate particles from local wood burning to cause more than 900 deaths per year, but here the exposure estimate is very uncertain. For road dust we calculate 215 deaths per year based on the exposure-response function from a Swedish study. We believe that the impact on mortality from locally emitted vehicle exhaust including particles is best indicated by exposure-response functions for within city gradients in NO2, which also could include effects of NO2 itself. We estimate approximately 2850 deaths per year from vehicle exhaust, but using alternative risk functions would result in 15-30% reduced estimates.
The total number of excess deaths due to air pollution exposure was estimated up to 7600 in 2015. The increase in comparison to the 2010 estimate is not due to changes in estimated exposure, but resulting from a revision of assumed exposure-response relations. If we for 2010 had assumed the urban NO2 contribution to increase mortality without any cutoff, we would have estimated almost the same impact on mortality associated with NO2 as in 2015. Finally, the health impacts from exposure to NO2 and PM2.5 can be conservatively estimated to cause socio-economic costs of ~56 billion Krona in 2015. Just absence from work and studies can be estimated to cause socio-economic costs of ~0.4% of GDP in Sweden.