BEIJING, March 12 (Chinese medianet) -- A new researchfound that people living in cities exposed tounhealthy levels of ground-level ozone -- the major component of smog -- are 30 percent more likely to die from respiratory diseases than those living in least smoggy areas.
The nationwide study of 450,000 adults published in the New England Journal of Medicine is the first to document the long-term impact of ozone on human health.
It's estimated that 100 million Americans-- or 1 in 3-- live in cities with unhealthy levels of ground-level ozone. Ground-level ozone forms when tailpipe emissions combine with sun and hot air. Smog season runs from April through October in Southern California, and is slightly shorter in cooler regions of the country, such as the Mid-Atlantic and Northeastern states.
The new study provides the first evidence that long-term, chronic exposure to elevated levels of ozone significantly increases the risk of death from respiratory diseases.
"The study points to the fact that there may be a three-fold increased risk of dying from respiratory disease in the smoggiest areas of the country," says Dr. John Balmes of the University of California, San Francisco.
The adults in the study, originally recruited by the American Cancer Society, were tracked for 18 years. During this time, about 118,000 people died. Michael Jerrett, a researcher at the University of California, Berkeley and his colleagues then teased out the causes of death. They documented that people living in the smoggiest cities were more likely to have died from lung diseases such as chronic bronchitis, emphysema and pneumonia.
Jerrett and his team controlled for 44 individual factors that may have influenced the results, such as smoking, alcohol consumption, occupational exposures, unemployment status and income. But even after that, he says, "We still see a very strong and clear signal that people in high-ozone areas are at higher risk of death."
(Agencies)
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