Study finds long-term ozone exposure raises the risk of dying from lung disease

http://www.eurekalert.org/pub_releases/2009-03/nlmc-sfl030609.php

NEW YORK, March 11, 2009 – Long-term exposure to elevated levels of ground ozone—a major constituent of smog—significantly raises the risk of dying from lung disease, according to a new nationwide study of cities that evaluated the impact of ozone on respiratory health over an 18-year period.

The study found that the risk of dying from respiratory disease is more than 30 percent greater in metropolitan areas with the highest ozone concentrations than in those with the lowest ozone concentrations.

Over the last decade, several nationwide studies have shown that long-term exposure to tiny particles of dust and soot in air pollution is a risk factor for death from heart and lung disease. However, it was unclear whether long-term exposure to ozone, a widespread pollutant in summertime haze, was linked to a higher risk of dying from lung disease itself.

The new study, published in the March 12 issue of the New England Journal of Medicine, is the first nationwide population study on the long-term impact of ozone on human health, and the first to separate ozone's effects from those of fine particulate matter, the tiny particles of pollutants emitted by factories, cars, and power plants.

"Many studies have shown that a high-ozone day leads to an increase in risk of acute health effects the next day, for example, asthma attacks and heart attacks," says George D. Thurston, Sc.D. who directed the air pollution exposure assessment part of the study. "What this study says is that to protect the public's health, we can't just reduce the peaks, we must also reduce long-term, cumulative exposure." Dr. Thurston is a professor in the Department of Environmental Medicine at NYU School of Medicine, a part of NYU Langone Medical Center.

Ozone in the upper atmosphere protects against harmful ultraviolet (UV) radiation. At ground level, ozone, or O3, forms when nitrogen dioxide from tailpipes, coal-fired power plants and other industries collides with oxygen in the presence of sunlight. Considered a secondary pollutant because it takes time to form, ozone tends to be higher in concentration in suburbs and rural areas downwind of cities. Fine particulate matter, a primary pollutant, is more prevalent at its source, in the inner city, along roadways and in industrial areas.

In concert with rising death rates from respiratory disease, "background levels of ozone have at least doubled since pre-industrial-revolution times," says Michael Jerrett, Ph.D., associate professor, Division of Environmental Health Sciences, at the University of California, Berkeley, and the lead author of the new study.
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The EPA provides a list of counties in the United States, their present ozone concentrations, and their compliance status with regard to the current short-term ozone standard at the following URL: http://epa.gov/air/ozonepollution/pdfs/2008_03_design_values_2004_2006.pdf.

The present EPA air quality standards do not protect against the long-term cumulative effects of ozone exposures, but only address the health effects of short-term daily peaks in ozone exposure, says Dr. Thurston. Currently, the Environmental Protection Agency's standard for short-term (8-hour) ozone exposure is 75 parts per billion, which exceeds the 60 ppb recommended by the EPA's own scientific advisory group, the American Lung Association and more than a dozen other public health organizations. The EPA will be reviewing its ozone standard in the coming year.