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 (NO₂) 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.