Abstract. Air pollution concentrations have been decreasing in many cities in the
developed countries. We have estimated time trends and health effects
associated with exposure to NOx, NO2,
O3, and PM10 (particulate matter) in the Swedish cities Stockholm, Gothenburg, and
Malmö from the 1990s to 2015. Trend analyses of concentrations have been
performed by using the Mann–Kendall test and the Theil–Sen method. Measured
concentrations are from central monitoring stations representing urban
background levels, and they are assumed to indicate changes in long-term
exposure to the population. However, corrections for population exposure have
been performed for NOx, O3, and PM10 in
Stockholm, and for NOx in Gothenburg. For
NOx and PM10, the concentrations at the central
monitoring stations are shown to overestimate exposure when compared to
dispersion model calculations of spatially resolved, population-weighted
exposure concentrations, while the reverse applies to O3. The
trends are very different for the pollutants that are studied;
NOx and NO2 have been decreasing in all cities,
O3 exhibits an increasing trend in all cities, and for PM10,
there is a slowly decreasing trend in Stockholm, a slowly increasing trend in
Gothenburg, and no significant trend in Malmö. Trends associated with
NOxand NO2 are mainly attributed to local emission
reductions from traffic. Long-range transport and local emissions from road
traffic (non-exhaust PM emissions) and residential wood combustion are the
main sources of PM10. For O3, the trends are affected by
long-range transport, and there is a net removal of O3 in the
cities. The increasing trends are attributed to decreased net removal, as
NOx emissions have been reduced. Health effects in terms of changes in life expectancy are calculated based
on the trends in exposure to NOx, NO2, O3, and PM10 and
the relative risks associated with exposure to these pollutants. The
decreased levels of NOx are estimated to increase the life expectancy
by up to 11 months for Stockholm and 12 months for Gothenburg. This
corresponds to up to one-fifth of the total increase in life expectancy
(54–70 months) in the cities during the period of 1990–2015. Since the
increased concentrations in O3 have a relatively small impact on the
changes in life expectancy, the overall net effect is increased life
expectancies in the cities that have been studied.