ISEE/ISEA 2006 Conference Abstracts Supplement: Symposium Abstracts: Abstracts
The effects of ambient ozone were studied in 90 U.S. cities (50 with year-round daily measurements and 88 with at least summer-only measurements), with population from 250,000 to 9 million; 22 European cities (with daily measurements), population from 200,000 to 7 million); and 12 Canadian cities (with daily measurements), population from 200,000 to 20 million. The daily numbers of total, respiratory, and cardiovascular deaths was studied as the outcome for all ages and among those >75 years of age. The analysis was done in 2 stages. The first stage concerns city-specific datasets and involves extensive exploratory and sensitivity analyses. The second stage involves combining the effect estimates and attempting to explain heterogeneity by predefined potential effect modifiers. Results from core models and sensitivity analysis are presented.
The sensitivity analysis includes various methods for smoothing seasonality and different choices of degrees of freedom. Thus, for example, the daily increase of all nonaccidental deaths associated with 10-μg/m3 increase in ozone concentration using 8 degrees of freedom per year and natural splines, in cities with year-round measurements, was 0.16% (95% confidence interval: 0.02–0.30) for European cities and 0.20% (0.11–0.28) for U.S. cities. The effects estimated for Canadian cities were generally higher. Effect modification patterns between the 2 continents showed differences with environmental and climatic variables, but consistency with socioeconomic status indicators.