Scientists Tie High Ozone Levels to Early Death

Nov. 17—After reviewing more than a decade of air quality reports and medical records, a team of scientists says it has linked ozone to premature death.

High levels of ozone — a colorless, odorless gas that forms smog — have long been tied to asthma, increased hospitalizations, heart problems and, more recently, an increase in some kinds of infections.

But the new study, hailed by some environmental health researchers and advocacy groups as "landmark," fingers ozone as a direct cause of death, causing perhaps as many as several thousand deaths a year in the United States.

"Now we can say that ozone has been linked to mortality in addition to other health concerns," said Michelle Bell, assistant professor of environmental health at Yale University.

Bell led the study, published in today's issue of the Journal of the American Medical Association.

The new research comes a day after the release of a large European study that found similar effects in 19 of 23 European cities. Those results were published in the American Journal of Respiratory and Critical Care Medicine.

Bell's study may be especially resonant in Houston, which periodically has the worst ozone levels in the country. This year, Houston had more days of unhealthy smog levels than Los Angeles for the first time since 2000.

"I think this research is something we really have to look at and be worried about," said Winifred Hamilton, an assistant professor of environmental health at Baylor College of Medicine. "I would hope that this would help bring more urgency to beginning to make some changes to lower ozone now rather than later. High ozone isn't good for the health of citizens, it isn't good for the city's reputation."

The scientists reviewed 95 cities' ozone data and mortality records between 1987 and 2000. They also adjusted their data to wash out influence from extraneous contributing factors, including other environmental hazards and weather-related causes of death such as heat waves.

They found that, nationwide, when the 24-hour average for ozone in the lower atmosphere was 10 parts per billion higher than in the previous week, there was a 0.52 percent increase in the number of deaths. The effect is cumulative, so if the increase is more than 10 parts per billion, lives lost should also increase, the researchers said.

For Houston, the effect the researchers found was slightly higher than the national average, an 0.8 percent increase in the number of deaths on bad ozone days.

Hamilton said the city has about 40 days a year on which ozone is 10 parts per billion above the previous week's level.

Rick Hagar, a spokesman for the East Harris County Manufacturers Association, a nonprofit professional association of approximately 125 chemical manufacturers and refiners, said his organization had not seen the study. However, he did say Houston's air quality has improved in recent years.

"EHCMA has a tradition of working with our communities to improve our environmental performance," he said.

Left unanswered by the study is how ozone could be killing people. Bell said the data suggested an increase in cardiovascular and lung-related deaths on high-ozone days, and both heart and lung problems could be triggered by ozone.

The notion that high ozone, on its own, can cause premature death has been gaining acceptance in the last four or five years, scientists say.

Although earlier studies have suggested a link, the new research provides the most compelling evidence yet, said Dr. Philip Landrigan, director of the Center for Children's Health and the Environment at the Mount Sinai School of Medicine in New York City.

"This is a very significant study," he said. "It argues for stronger enforcement of air pollution standards and for stricter standards."

Houston already cannot meet federal clean air standards and has a deadline of 2007 to do so. But activists and officials agree the city is unlikely to meet this date and may receive an extension.

If Houston does not meet the deadline and does not receive an extension, it could face federal sanctions, including the loss of road-construction funding.

© 2004, Houston Chronicle. Distributed by Knight Ridder/Tribune Business News.