Deadly haze.
Ozone can lead to premature death, especially among the sick and elderly.
Credit: Jupiter Images
The U.S. Environmental Protection Agency (EPA) should consider deaths caused by ozone when it sets air-quality standards, according to a report released today by the National Academies' National Research Council (NRC). "This is an important result," because it will justify a tighter standard, says George Thurston, an environmental scientist at New York University in New York City.
A major component of smog, ozone is a byproduct of chemical reactions involving nitrogen oxides and other pollutants. It oxidizes lung tissue, causing inflammation. This exacerbates asthma and leads to other respiratory problems. Short-term exposure may also be a cause of premature death, perhaps by worsening existing lung diseases, but epidemiological studies have been inconclusive.
The issue matters because EPA is required by law to review its air-quality standard for ozone every 5 years. In 2006, while its staff was reviewing the science on ozone, EPA asked NRC to evaluate the strength of the evidence regarding premature mortality.
After reviewing the literature, the panel concluded that exposure to ozone for less than 24 hours is probably a cause of premature mortality. The outcome is most likely in elderly people who are already sick and near death. "The bottom line is clear: There is a mortality effect," says John Bailar III, an epidemiologist retired from the University of Chicago, who chaired the panel. Bailar estimates that in total several hundred to a few thousand people die prematurely each year due to ozone. Healthy people may also be at risk, but more research is needed to clarify that danger. More studies are also needed to determine whether long-term exposure to ozone, over weeks to years, is also lethal.
Last month, the agency tightened the ozone standard but not as much as public health advocacy groups wished (Science, 21 March, p. 1602). Observers predict that EPA will now give more weight to premature mortality when revising the ozone standard, perhaps leading to tighter regulations.
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