EPA science review confirms ozone/disease link

Posted: Feb 18, 2013

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A U.S. EPA science review has reaffirmed that exposure to ozone -- a precursor to smog -- is associated with respiratory and cardiovascular disease and death.

The 1,200-page integrated science assessment, released Friday, is the first update to EPA's ozone review since 2006 and is meant to guide the writing of national air quality standards. The document reflects evidence from studies released since the 2006 review.

The new report cites greater evidence to back up conclusions linking ozone exposure and respiratory inflammation, shortness of breath and heart disease. "A very large amount of evidence spanning several decades" shows a relationship between short-term smog exposure and a variety of respiratory effects, the report says.

While the 2006 review said studies were "highly suggestive" of a relationship between short-term ozone exposure and rising mortality, the latest study found even more evidence of a link and concludes that there is "likely to be a casual relationship."

Evidence linking long-term exposure to mortality was less conclusive, although EPA said it is "suggestive" of a relationship.

Evidence also suggests a link between ozone and cardiovascular problems, although the agency warned that there are still a limited number of studies available. The agency said research was "highly suggestive" that ozone contributes to heart-related morbidity, but said more research is needed to back up that conclusion.

Frank O'Donnell, president of Clean Air Watch, said the study shows ozone is "a bigger health threat than commonly recognized even a half-dozen years ago" and should offer "strong evidence" that EPA needs to tighten the standard.

In 2008, EPA set the current ozone standard at 75 parts per billion over an eight-hour average. President Obama in 2011 rejected an EPA proposal to lower it to 60 to 70 parts per billion.

The report also examines the existing literature on ozone's link to climate change and confirms the agency's previous conclusion that increased smog levels are likely tied to rising global temperatures.

The review also identifies a relationship between ozone and reduced plant growth, as well as a reduction in carbon storage by plants. Ozone exposure could also weaken crop yields or reduce the quality of crops.

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