Airing it Out
April 28, 2003
America's air quality has vastly improved in recent decades due to progressive emission reductions from industrial facilities and motor vehicles. Nonetheless, both the Bush Administration and congressional Democrats have proposed sweeping new measures to further crack down on power plant emissions.
The administration's Clear Skies Initiative and a more stringent Democratic alternative are based on claims that current levels of particulate matter (PM) pose a serious public health threat. Supporters of these bills promise substantial benefits from additional PM reductions.
The Competitive Enterprise Institute, however, points out that an American Cancer Society (ACS) study that reports an association between PM and mortality shows some odd features in its results. For example:
- According to the ACS study, PM increased mortality in men, but not women; in those with no more than a high school degree, but not those with at least some college education; in former-smokers, but not current- or never-smokers; and in those who said they were moderately active, but not those who said they were very active or sedentary.
- These odd variations in the relationship between PM of 2.5 microns or less in diameter and mortality seem biologically implausible, says the CEI.
- Even more surprising, the ACS study reported that higher PM2.5 levels were not associated with an increased risk of mortality due to respiratory disease; a surprising finding, given that PM would be expected to exert its effects through the respiratory system.
The evidence suggests that exposure to PM at current levels likely has little or no effect on mortality in most of the United States. Additional near-term reductions in PM could probably best achieved by dealing with the stock of high-polluting older vehicles that account for a substantial portion of ambient PM levels in metropolitan areas, explains the CEI.
Source: Joel Schwartz, "Particulate Air Pollution: Weighing the Risks," April 21, 2003, Competitive Enterprise Institute.
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