Study Challenges Air Pollution Alarmism

by William Yeatman on April 29, 2003

in Science

A study by Joel Schwartz challenges the scientific basis of both the Bush Administrations Clear Skies Initiative and Senator Jim Jeffordss (I-Vt.) Clean Power Act. The analysis has implications for climate policy because Jeffordss legislation includes regulation of carbon dioxide emissions and Bushs plan could serve as a proxy climate policy by forcing utilities to close coal-fired power plants in order to reach the limits on mercury emissions.

Clear Skies and Clean Power would impose tough new controls on power plants to reduce levels of fine particle (PM2.5) pollution, which both sides claim kills tens of thousands of people per year. Supporters of these bills promise substantial benefits from additional PM reductions.

Schwartzs new study, published by the Competitive Enterprise Institute, argues that Clear Skies and Clean Power rest on a weak scientific foundation. The U.S. Environmental Protection Agency (EPA) based its new annual fine PM (PM2.5) standard on a study known as the American Cancer Society (ACS) study of PM and mortality, which assessed the association between the risk of death between 1982 and 1998 with PM2.5 levels in dozens of American cities.

Although the ACS study reported an association between PM and mortality, some odd features of the ACS results suggest that PM is not the culprit. For example, higher PM levels 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; 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 PM2.5 and mortality seem biologically implausible. 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.

EPA also ignored the results of another epidemiological study that found no effect of PM2.5 on mortality in a cohort of veterans with high blood pressure, even though this relatively unhealthy cohort should have been more susceptible to the effects of pollution than the general population. The evidence therefore suggests that EPAs annual standard for PM2.5 is unnecessarily stringent. Attaining the standard will be expensive, but is unlikely to improve public health.

Air pollution has declined dramatically over the past 30 years, and will continue to decline, both because more recent vehicle models start out cleaner and stay cleaner as they age than earlier ones, and also because already-adopted standards for new vehicles and existing power plants will come into effect in the next few years.

If policymakers feel they must do something to speed up PM reductions, Schwartz advises they offer people tax incentives to scrap high-polluting older vehicles that account for a substantial portion of ambient PM levels in metropolitan areas. This flexible, cost-effective approach is more likely to result in net public health benefits than either Clear Skies or Clean Power.

The study is available at,03452.cfm.


The Cooler Heads Coalition and the George C. Marshall Institute will host a congressional staff and media briefing on Friday, May 16, from Noon to 1:30 PM in Room G-50 of the Senate Dirksen Office Building. Dr. Willie Soon, a research physicist with the Harvard-Smithsonian Center for Astrophysics, will speak on, “Was the Twentieth Century Climate Unusual? Exploring the Lessons and Limits of Climate History.”

Lunch will be provided, and reservations are required. To register, please telephone the Marshall Institute at (202) 296-9655 or e-mail them at

Soons talk will be based on a recent major review article of which he was the lead author. See the April 16 issue for more details. The article has been posted on the web at A less technical version is available on the Marshall Institutes web site at

Comments on this entry are closed.

Previous post:

Next post: