Short-term exposure to smog, or ozone, is clearly linked to premature deaths that should be taken into account when measuring the health benefits of reducing air pollution, a National Academy of Sciences report concluded Tuesday.

The findings contradict arguments made by some White House officials that the connection between smog and premature death has not been shown sufficiently, and that the number of saved lives should not be calculated in determining clean air benefits.

The report by a panel of the academy's National Research Council says government agencies "should give little or no weight" to such arguments.

"The committee has concluded from its review of health-based evidence that short-term exposure to ambient ozone is likely to contribute to premature deaths," the 13-member panel said.

It added that "studies have yielded strong evidence that short-term exposure to ozone can exacerbate lung conditions, causing illness and hospitalization and can potentially lead to death."

The White House Office of Management and Budget, which in its review of air quality regulations has raised questions about the certainty of the pollution and mortality link, did not immediately return a phone call seeking comment.

"The report is a rebuke of the Bush administration which has consistently tried to downplay the connection between smog and premature death," said Frank O'Donnell, president of Clean Air Watch, a Washington-based advocacy organization.

Report refutes White House's position

Vickie Patton, deputy general counsel for the Environmental Defense Fund, said the academy's finding "refutes the White House skepticism and denial" of a proven link between acute ozone exposure and premature deaths. Such arguments have been used to diminish the health benefits of reducing air pollution, she said.

The academy panel examined short-term exposure — up to 24 hours — to high levels of ozone, but said more studies also were needed on long-term chronic exposure where the risk of premature death "may be larger than those observed in acute effects studies alone."

Ground-level ozone is formed from nitrogen oxide and organic compounds created by burning fossil fuels and is often seen as a yellow haze, or smog, that lingers in the air. Ozone exposure is a leading cause of respiratory illnesses and especially affects the elderly, those with respiratory problems and children.

While premature death from ozone exposure is greater among individuals with lung and heart disease, the report said such deaths are not restricted to people who are at a high risk of death within a few days.

The scientists said they could not determine, based on a review of health studies, whether there is a threshold below which no fatalities can be assured from ozone exposure. If there is such a point, it is below the ozone levels allowed for public health.

Disputes over smog-deaths connection

Environmentalists and health advocates have argued that a string of health studies and surveys show that exposure to smoggy air not only aggravates respiratory problems, but causes thousands of deaths a year.

But in a number of instances the EPA and the White House's OMB, which reviews regulations, have been at odds over the certainty of a link between smog levels and deaths.

Patton said the OMB in a number of air pollution regulations has sought to minimize the relationship of pollution and premature deaths, resulting in a lower calculation of health benefits from pollution reductions.

"This has been used by industry to try to attack health standards by minimizing the societal benefits," said Patton.

One such case involves the EPA's decision last month to toughen the ozone health standard, reducing the allowable concentration in the air.

When the cost-benefit analysis was being prepared in connection with the rule-making, the OMB argued there is "considerable uncertainty" in the association between ozone levels and deaths.

As a result, the EPA issued a wide cost-benefit range, from an annual net societal cost of $20 billion US to a savings of $23 billion US, depending largely on whether one takes into account lives saved from ozone-related premature deaths.

OMB officials also have objected to the EPA quantifying ozone-related mortality benefits in new emissions standards for lawn mowers and other small engines that release large amounts of ozone-forming pollution.

In response, the EPA removed "all references to quantified ozone benefits" in the proposed rule, according to an e-mail sent by EPA to the OMB. The small engine regulation is awaiting final action.