The short-term effect of 24-h average and peak air pollution on mortality in Oslo, Norway

Numerous epidemiological studies have shown associations between increases in outdoor air pollution and all-cause mortality as well as cardiovascular and respiratory related mortality. The majority of studies has used the routine monitoring network and thus has not been able to characterize the small-scale variation in daily averages and peak concentrations within urban settings. To address possible short term impact on mortally by air pollution we used a time-stratified case-crossover design to estimate associations of traffic-related air pollution and wood burning and daily mortality during a period of 10 years among residents above 50 years of age in Oslo, Norway. A dispersion model was used to assess short-term air pollution for daily (24-h) averages and peak concentrations of nitrogen dioxide (NO(2)) from exhaust and particulate matter with a diameter of 2.5 μm or less (PM(2.5)) from exhaust and wood-burning at residential neighbourhood level for each individual. We found an overall increased risk from exposure at the lag of 0-5 days before the day of death for both pollutants. The excess risk was highest for PM(2.5) with a 2.8 % (95 % confidence interval: 1.2-4.4) increase per 10 μg per cubic meter change in daily exposure. Short-term traffic-related air pollution was associated with increased risk for mortality among individuals above 50 years of age, especially for circulatory outcomes.