Yale Study Finds No Safe Level For Ozone

Even at very low levels, ozone -- an ingredient in smog -- increases the risk of premature death, according to a nationwide study announced on Feb. 16.

The study, sponsored by EPA and the Centers for Disease Control, found that if a safe level for ozone exists, it is only at very low or natural levels and far below current U.S. and international regulations. A 10 part-per-billion (ppb) increase in the average of the two previous days' ozone levels is associated with a 0.30 percent increase in mortality, according to the researchers.

The current study builds on research published in Nov. 17 2004 in theJournal of the American Medical Association ("Ozone and Short-term Mortality in 95 US Urban Communities, 1987-2000"), which was the first national study of ozone and mortality, the researchers said.

"This study investigates whether there is a threshold level below which ozone does not affect mortality. Our findings show that even if all 98 counties in our study met the current ozone standard every day, there would still be a significant link between ozone and premature mortality," said Michelle Bell, lead investigator on the study and assistant professor of environmental health at the Yale School of Forestry & Environmental Studies. "This indicates that further reductions in ozone pollution would benefit public health, even in areas that meet regulatory requirements."

Researchers found that even for days that currently meet the EPA limit for an acceptable level of ozone -- 80 ppb for an eight-hour period -- there was still an increased risk of death from the pollutant.

An effort is now under way by EPA to consider whether more stringent standards for ozone are needed.

"More than 100 million people in the United States live in areas that exceed the National Ambient Air Quality Standard for ozone. Elevated concentrations of ozone are also a growing concern for rapidly developing nations with rising levels of ozone from expanding transportation networks," said Francesca Dominici, co-author of the study and associate professor of biostatistics at Johns Hopkins.

The study is online at http://ehp.niehs.nih.gov/docs/2006/8816/abstract.html.

Michelle Bell: http://www.yale.edu/forestry/bios/bell.html

Yale School of Forestry & Environmental Studies: http://www.yale.edu/forestry

This article originally appeared in the 02/01/2006 issue of Environmental Protection.

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