March 11 (HealthDay News) -- Thousands of Americans are dying each year from lung disease caused by atmospheric ozone, a new study finds.
The greatest risk may for those living be in hot, dry cities such as Los Angeles, which has one of the highest concentrations of ozone. Residents of Los Angeles may face a 25 percent to 30 percent higher annual risk of dying from a respiratory ailment versus people in low-ozone areas such as the Great Plains, the researchers said.
The report, published in the March 12 issue of the New England Journal of Medicine, also found that that tiny components of smog called "fine particulate matter" had a clear link to cardiovascular deaths.
"This is one of the first studies where we've been able to report separate independent effect from both particulate matter and ozone," said lead researcher Michael Jerrett, an associate professor of environmental health sciences at the School of Public Health, University of California, Berkeley. "With particulate matter, we see effects very strongly for cardiovascular mortality such as heart attack and stroke and, for ozone, we see them in respiratory deaths."
"That suggests that we can't just regulate particulate matter or ozone," Jerrett continued. "We have to look at dealing with both pollutants because they're both exerting major impacts, but on different mortality outcomes."
An estimated 240,000 people in the United States and 7.7 million people worldwide die of respiratory disease each year, according to data from the World Health Organization.
Efforts to reduce ground-level ozone have stalled in recent years, Jarrett said, and now one in three Americans lives in an area that exceeds the national standard for ozone levels.
A year ago, the U.S. Environmental Protection Agency did issue stricter air quality standards for ground-level ozone, but many scientists advocate still lower levels.
When hovering seven miles above the earth, ozone is actually beneficial because it blocks ultraviolet radiation from the sun. However, closer to the ground it infiltrates the lungs and may cause damage. A number of studies have tried to link ozone exposure with mortality but they have been inconclusive, the researchers noted.
In their study, Jerrett and his colleagues cross-referenced American Cancer Society data with pollution data from 96 metropolitan areas in the United States. In all, the study included information on almost 449,000 people and included 118,777 deaths occurring over nearly two decades of follow-up.
The results: each additional 10 parts per billion (ppb) of ozone concentration was linked to a 4 percent increase risk of dying from respiratory causes, most notably pneumonia and chronic obstructive pulmonary disease (COPD).
The findings carry the knowledge of air pollution and its effect on health a notch deeper, one expert said.
"This is something we've seen before with high levels of pollution, though we had not identified ozone as something causing respiratory diseases," said Dr. Len Horovitz, a pulmonary specialist with Lenox Hill Hospital in New York City. "We know it's air pollution, but what in air pollution?
Ozone is also a powerful greenhouse gas, Jerrett said, so measures to improve health might have the added benefit of slowing climate change.
"Everybody knows we need to go greener. It's just a question of how we do that," Horovitz stated.
SOURCES: Michael Jerrett, Ph.D., associate professor, environmental health sciences, School of Public Health, University of California, Berkeley; Len Horovitz, M.D., pulmonary specialist, Lenox Hill Hospital, New York City; March 12, 2009, New England Journal of Medicine