Years of Life Lost Due to Air Pollution in Switzerland: A Dynamic Exposure-Response Model
There is debate on how the effect of air pollution should be assessed. The dynamic exposure-response model integrates data from long-term epidemiological studies and studies of interventions to reduce pollution to estimate the impact of air pollution on adult and infant mortality. Based on this method years of life lost (YLL) attributable to air pollution during 1 year in Switzerland were calculated.
A dynamic exposure-response model was implemented, which uses an exponential function (exp−kt) to model the change in mortality after cessation of air pollution. The model was populated with relative risk estimates and estimates of decay constant k from the literature. Air pollution exposure in Switzerland was modeled using data from emission inventories. YLL attributable to air pollution were calculated by taking the difference between observed survival probabilities in Switzerland in 2005 and modified survival probabilities, assuming a low PM10 level of 7.5 μg/m3 during the year 2005.
Meta-analyses of three studies of adult mortality and five studies of infant mortality gave relative risks of 1.059 (95% confidence interval (CI): 1.031–1.088) and 1.056 (95% CI 1.026–1.088) per 10 μg/m3 increase in PM10 concentration. Decay constants k derived from two studies of the effects of closing down a steel mill in the Utah Valley and of the coal ban in Dublin were 0.88 and 0.11 per year. Assuming a decay constant k of 0.5 per year resulted in 48,200 (95% CI 25,600–72,000) YLL, with 3.6% being ascribed to infant deaths. Thirty-nine percent of the effect occurred in the same year and 78% within 3 years.
In contrast to traditional steady-state models the dynamic model allows changes in mortality following short-term increases or decreases in air pollution levels to be quantified. This type of information is of obvious interest to policy makers.
KeywordsInfant Mortality Health Impact Assessment Excess Relative Risk Black Smoke PM10 Exposure
List of Abbreviations:
change in mortality in percent years
excess relative risk (=RR-1)
Particulate matter with an aerodynamic diameter of <10 μm
time (in years)
total suspended particles
years of life lost
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