ISEE/ISEA 2006 Conference Abstracts Supplement: Symposium Abstracts: Abstracts
APHENA is a collaborative effort joining the multicity European APHEA and the U.S. NMMAPS projects as well as independent Canadian investigators. The effects of ambient particulate matter (PM10) were studied in 90 U.S. cities (16 with daily measurements and 74 with one of 6 day measurements) with a 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 one of 6 day measurements), population from 200,000 to 20 million. The daily number of total, respiratory, and cardiovascular deaths was studied for all ages and among those above and under 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 using Poisson regression models. To control for several time-varying confounders, we used both natural and penalized splines as smoothers. We also applied models using varying degrees of freedom for seasonality control. The second stage involves combining the effect estimates obtained from the first stage and attempting to explain heterogeneity by predefined potential effect modifiers.
Results for all studied outcomes and from models using varying methods for seasonality control are presented. Thus, for example, the daily increase of cardiovascular deaths associated with 10-μg/m3 increase in PM10 concentrations using 8 degrees of freedom per year and natural splines, in cities with daily measurements, was 0.31% (95% confidence interval: 0.04 to 0.59) for European cities and 0.30% (−0.18 to 0.78) for U.S. cities. The effects estimated for Canadian cities were generally higher.
In summary, we found an increase in mortality (in most cases statistically significant) with increasing PM10 concentrations. Although the estimates in Europe and the United States were similar, in Canada, they were considerably higher. The effects were higher in the elderly compared with those under 75 years of age. Higher effects were observed in cardiovascular mortality. Effect modification patterns between the 2 continents showed differences with environmental and climatic variables but consistency with socioeconomic status indicators.