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Pollution
Linked To Heart Attacks
DALLAS
(AP) - High levels of air pollution can trigger heart attacks
in at-risk people exposed for even a short time, a study has found.
Researchers
who interviewed 772 Boston-area patients about four days after
their attacks found that the onset of symptoms correlated with
times of high daily air pollution.
Tiny, invisible
particles long have been thought to cause long-term cardiovascular
diseases. The new study is the first to examine short-term effects
on the heart, said senior author Dr. Murray Mittleman, director
of cardiovascular epidemiology at Boston's Beth Israel Deaconess
Medical Center.
The study
of 489 men and 283 women, conducted from January 1995 to May 1996,
defined at-risk people as obese, inactive or those with a history
of heart problems.
The results
appear in Tuesday's edition of Circulation, a journal of the American
Heart Association.
The pollution
particles are called PM-2.5, for particulate matter less than
2.5 micrometers in diameter. They're emitted by cars, power plants
and industry, as well as fireplaces and wood-burning stoves.
Studies in
the past five years have linked deaths and hospital admissions
to a spike in PM-2.5 levels. In the study, risk for heart attack
peaked two hours and 24 hours after patients were exposed to increased
levels of the particles.
After two
hours, risk increased 48 percent in the hours when pollution was
the worst, compared to the best hours; after 24 hours, risk increased
62 percent.
The study
also examined health risks caused by ozone, a chief ingredient
of smog that's created when air pollutants mix. Ozone has been
linked to lung and breathing problems, but researchers in this
study found no data linking it to heart attacks, Mittleman said.
The study
did not address how the particles trigger heart attacks. Other
studies have shown that the particles, small enough to bypass
the body's defenses and get into the lungs and other tissue, cause
inflammation and blood clotting. These symptoms may contribute
to heart attacks by blocking flow of blood through the heart,
some researchers say.
Still other
studies have shown that the particles may create electrical reactions
that affect the nervous system.
PM-25 particles
are light enough to travel long distances and infest air that's
typically clean. Air conditioning helps to filter it out of the
indoors.
``The best
advice is to avoid outdoor activity on hot, hazy days,'' said
study co-author Douglas Dockery, professor of environmental epidemiology
at Harvard.
Researchers
noted that Boston does not have excessive pollution and meets
federal air quality standards, so the risk could be even worse
in high-pollution cities such as Houston and Los Angeles.
The Environmental
Protection Agency's air quality standards, last updated in 1997,
have been challenged in court in part because no one has pinpointed
why pollution particles pose a health risk.
The study
could be used to encourage the EPA to consider stricter air standards,
said Dr. Jonathan Samet, chairman of the department of epidemiology
at Johns Hopkins University, who was not involved in the study.
On
the Net:
http://www.epa.gov
Reference
Source 102
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