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Activity Number: 546
Type: Invited
Date/Time: Wednesday, August 1, 2012 : 2:00 PM to 3:50 PM
Sponsor: Section on Risk Analysis
Abstract - #303766
Title: A Closer Look at Air Pollution-Mortality Relationships for California Members of the American Cancer Society Cohort
Author(s): Frederick W. Lipfert*+ and S. Stanley Young
Companies: Environmental Consultant and National Institute of Statistical Sciences
Address: 23 Carll Court, Northport, NY, 11768,
Keywords: meta-analysis ; significance levels ; collinearity ; air pollution
Abstract:

Estimates of public health benefits attributed to cleaner air are largely based on studies of spatial differences in long-term mortality rates. However, such studies tend to suffer from lack of specificity, such as uncertain exposures and neglected confounders and co-pollutants. Here we use meta-analyses to re-examine the results of Jerrett et al. (2011), comprising 992 estimates of long-term mortality-air pollution relationships among California members of a national cohort, with follow-up from 1982 to 2000. These risk estimates include strong and significant positive (harmful) spatial relationships for heart disease and strong and significant negative (beneficial) relationships for other causes including cancer, thus raising questions of causality and credibility. Excess risk estimates for all-cause deaths were essentially randomly distributed around zero. Relative model fits were not compared by Jerrett et al., thus precluding identification of the "best" models on this basis. However, only a selected few of these 992 estimates are emphasized in the Jerrett report. By considering the results as a whole, we find major differences among these relationships according to the regression model selected and methods of estimating exposures, none of which specifically considered latency periods. Strong correlations among the various pollutants considered make it difficult to define any "true" relationships; we found no significant differences among their risk estimates. Relation-ships with deaths from all causes should be the basis for air pollution control policies and, in a study of this regulatory importance, it is important to discuss both positive and negative findings and to consider the entire suite of results rather than a few that happen to conform to a priori regulatory objectives and were apparently selected for that reason.


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