Study Finds No Safe Level of Ozone

A study sponsored by the U.S. Environmental Protection Agency (EPA) and the Centers for Disease Control and Prevention has found no safe level of ground-level ozone, a component of smog linked to respiratory problems. The study, carried out by researchers at Yale and Johns Hopkins universities and published by

Environmental Health Perspectives, found that an increase of ten parts per billion in day-to-day ozone concentrations causes a 0.3% increase in mortality—about 2,000 additional deaths per year in a city the size of New York, according to Yale’s Michelle Bell, Ph.D., lead author. “We found strong evidence that if there is any safe level for ozone’s impact on mortality, it is at very low concentrations, nearing natural background levels,” she says. EPA is currently reviewing its acceptable level of ozone; 100 million Americans live in areas exceeding that level. Along with motivating stricter regulations on outdoor emissions of ozone, this new information increases the importance of eliminating indoor ozone-generating equipment—including, most obviously, ozone generators, which continue to be marketed as air purification devices (see

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Vol. 12, No. 10). The study is online at www.ehponline.org/docs/2006/8816/abstract.html.