'Safe' Ozone Levels Can Worsen Asthma
Pollutant attacks lining of lungs, study finds

HealthDayNews
TUESDAY, Oct. 7, 2005
By Ed Edelson

A new study finds that air pollution at levels listed as safe by the federal government can cause breathing problems for children with asthma -- and, researchers say, maybe for a lot of other people.

"We looked at particularly vulnerable members of society and the effect daily levels of ozone had on their respiratory system," says study leader Janneane F. Gent, an associate research scientist at Yale University School of Medicine. "But the ozone blanketing our region is affecting all of us. Not everyone has asthma, but we are all breathing the same air."

Gent and her colleagues studied 271 children under the age of 12 with active asthma, measuring their response to two air pollutants, ozone and very small particulate matter. A one-hour exposure to air containing 50 parts per billion caused a significant increase in wheezing and chest tightness in those children, and increased their use of symptom-relieving drugs, says a report in the Oct. 8 issue of the Journal of the American Medical Association .

The U.S. Environmental Protection Agency (EPA) air quality standard for ozone is set at 120 parts per billion.

The eight-hour EPA exposure standard is 80 parts per billion. The study found significant effects on respiratory symptoms and medication use for an eight-hour exposure at 51 parts per billion.

"This is one of a growing number of studies that point to adverse effects of ozone levels below those currently regarded as safe," Gent says.

No ill effects of such exposure was seen in a control group of children who were not taking asthma medication, the researchers say.

But that doesn't necessarily mean that normal lungs are not being hurt by that level of ozone exposure, says George D. Thurston, an associate professor of environmental medicine at the New York University School of medicine and co-author of an accompanying editorial.

He compares the children with asthma to the canaries once carried into mines to serve as early detectors of air problems.

Ozone is an unusually reactive form of oxygen, Thurston notes. One early test of the effects of ozone was to see how much damage it caused to a rubber band, he says.

"If it can damage the elasticity of rubber, you can imagine what it does to the lining of the lungs," he says. "It certainly has some effect on the lining of the lungs of a healthy person, but the effect is much stronger for a child with asthma."

Atmospheric ozone is produced by the burning of fossil fuels such as coal and oil and in chemical production. The EPA tightened its ozone standards five years ago, and is now studying health data to see if the standards should be tightened further, Thurston says.

"Probably some time next year a draft of the proposed standards should come out," he says.

More information

An overview of ozone as an air pollutant can be found at the U.S. Environmental Protection Agency or the American Lung Association . You can also try the American Academy of Allergy, Asthma and Immunology for information on asthma.

SOURCES: Janneane F. Gent, Ph.D., associate research scientist, Yale University School of Medicine, New Haven, Conn.; George D. Thurston, Sc.D., associate professor, environmental medicine, New York University School of Medicine, Tuxedo, N.Y.; Oct. 8, 2003, Journal of the American Medical Association

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