Researchers from The Johns Hopkins University say they have confirmed the results of previous studies which found an association between particulate air pollution, as represented by a measure called "total suspended particles" (TSP), and mortality in Philadelphia. But have they?
- A statistically significant increase in total mortality was identified only among those older than 75 years of age. That increase was only 2 percent. And we all know that increases in risk of less than 100 percent are highly suspect.
- No investigation was undertaken to ensure the deaths among those 75 and over could be attributed to particulate air pollution. The researchers based their analysis on all deaths that were not caused by external causes (e.g., accidental deaths). So, for example, all deaths due to heart attack were included in the analysis without regard for the actual cause of the heart attack. This assumption undoubtedly biased the results toward showing an association.
I think all this study confirms is that The Johns Hopkins University School of Hygiene and Public Health (my alma mater) needs to clean up its act.
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