Academic journal article Environmental Health Perspectives

Acute Effects of Ambient Particulate Matter on Mortality in Europe and North America: Results from the APHENA Study

Academic journal article Environmental Health Perspectives

Acute Effects of Ambient Particulate Matter on Mortality in Europe and North America: Results from the APHENA Study

Article excerpt

BACKGROUND: The APHENA (Air Pollution and Health: A Combined European and North American Approach) study is a collaborative analysis of multicity time-series data on the effect of air pollution on population health, bringing together data from the European APHEA (Air Pollution and Health: A European Approach) and U.S. NMMAPS (National Morbidity, Mortality and Air Pollution Study) projects, along with Canadian data.

OBJECTIVES: The main objective of APHENA was to assess the coherence of the findings of the multicity studies carried out in Europe and North America, when analyzed with a common protocol, and to explore sources of possible heterogeneity. We present APHENA results on the effects of particulate matter (PM) [less than or equal to] 10 [micro]m in aerodynamic diameter ([PM.sub.10]) on the daily number of deaths for all ages and for those < 75 and [greater than or equal to] 75 years of age. We explored the impact of potential environmental and socioeconomic factors that may modify this association.

METHODS: In the first stage of a two-stage analysis, we used Poisson regression models, with natural and penalized splines, to adjust for seasonality, with various degrees of freedom. In the second stage, we used meta-regression approaches to combine time-series results across cites and to assess effect modification by selected ecologic covariates.

RESULTS: Air pollution risk estimates were relatively robust to different modeling approaches. Risk estimates from Europe and United States were similar, but those from Canada were substantially higher. The combined effect of [PM.sub.10] on all-cause mortality across all ages for cities with daily air pollution data ranged from 0.2% to 0.6% for a 10-[micro]g/[m.sup.3] increase in ambient [PM.sub.10] concentration. Effect modification by other pollutants and climatic variables differed in Europe and the United States. In both of these regions, a higher proportion of older people and higher unemployment were associated with increased air pollution risk.

CONCLUSIONS: Estimates of the increased mortality associated with PM air pollution based on the APHENA study were generally comparable with results of previous reports. Overall, risk estimates were similar in Europe and in the United States but higher in Canada. However, [PM.sub.10] effect modification patterns were somewhat different in Europe and the United States.

KEY WORDS: air pollution, effect modification, heterogeneity, meta-regression, mortality, natural splines, particulate matter, penalized splines, time-series analysis. Environ Health Perspect 116:1480-1486 (2008). doi:10.1289/ehp.11345 available via http://dx.doi.org/ [Online 26 June 2008]

Hundreds of time-series studies worldwide provide compelling evidence of the health effects of short-term exposure to air pollution. These studies also pose problems of interpretation due to variation in analytic methods and reporting, and the possibility of publication and analytic bias. Meta-analyses of published results can provide information about patterns in the relative rates of mortality and morbidity and evidence as to the causes of their spatial variation, but they inherit many of the same limitations of the individual studies. Coordinated multicity studies, designed partly to address these issues, have now been conducted in Europe and North America (Atkinson et al. 2001; Bell et al. 2004; Burnett and Goldberg 2003; Burnett et al. 1998, 2000; Gryparis et al. 2004; Katsouyanni et al. 1997, 2001; Samet et al. 2000a, 2000b, 2000c) and currently provide the most valid epidemiologic evidence of the effects of short-term exposure. The results of these studies appear broadly similar, but their methods and data characteristics differ, precluding definitive conclusions about their quantitative consistency and about the extent of and reasons for differences in the magnitude of the effects of short-term exposure among regions of the world. …

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