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Air pollution may
trigger sudden deaths
particles alters heart rate, studies find
By MARLA CONE, Los
Angeles Times * June 4, 2000
- Even moderate air pollution routinely found in many
U.S. cities may trigger sudden deaths by changing heart
rhythms in people with existing cardiac problems,
according to extensive new scientific research.
- More than a dozen studies on humans and animals
suggests that heart attacks, not lung disease, may be the
most serious medical threat posed by air pollution.
- The culprits appear to be tiny pieces of soot called
particulates. Scientists caution that the link between
heart problems and air pollution remains a strong
likelihood -- not a certainty. More research is under
- Severe particulate pollution exists in many urban and
desert areas, including Los Angeles, Philadelphia,
Chicago, New York City, Salt Lake City and Phoenix, which
in 1998 surpassed Riverside, Calif., with the nation's
highest particulate levels.
- Levels of particulate matter in Houston's air do not
exceed the limit set in the current national health
standard for that air pollutant.
- Environmental experts, however, expect Houston to
violate a new and stricter particulate standard if it
goes into effect. The new standard was adopted by the
Clinton administration but its implementation was halted
by a federal appeals court order, which the
administration is appealing to the Supreme Court.
- Houston now violates the national health standard for
only one major air pollutant -- ground-level ozone, a
respiratory irritant and smog's main ingredient.
- Research continues to indicate that air pollution can
cause serious lung problems. But as an overall threat to
public health, the danger to the heart appears to be more
weighty because of the sheer numbers of people with heart
disease. Cardiovascular disease is the No. 1 killer in
the United States, responsible for nearly half of all
- Changes in heart rhythm that occur after breathing
particle pollution are subtle on an electrocardiogram,
and a healthy person is unaffected. But for someone with
a compromised or diseased heart -- especially a senior
citizen -- the impact could have deadly consequences,
- "When particulate pollution increases, the heart rate
seems to go up a little bit and the variability in the
heart rate seems to go down. Those are things classically
seen (in people) with heart failure," said Dr. Timothy
Denton, a cardiologist at Cedars-Sinai Medical Center in
- Experts have estimated that particulate pollution may
cause 1 percent of heart disease fatalities in the United
States. That fraction is small but would amount to 10,000
deaths a year.
- "If you believe the calculations, particulate-related
death is a serious public health problem -- more serious
than any other pollutant like ozone or sulfur dioxide or
carbon monoxide," said Dr. Henry Gong, a University of
Southern California medical professor who is a leading
expert on the health effects of air pollution.
- Epidemiologists in 70 cities around the world
consistently have found that more people die and are
hospitalized when particulate pollution rises even a
- Rarely does such a clear pattern emerge in
epidemiology, and most experts are now convinced that it
is not a coincidence.
- "For air pollution to have such a substantial impact
on public health, and have it show up so consistently, is
remarkable," said Daniel Costa, chief of the U.S.
Environmental Protection Agency's pulmonary toxicology
- The sudden-death phenomenon has been reported for
nearly a decade. Only during the last year have
scientists begun to figure out why.
- Tiny, ubiquitous particles of soot -- from diesel
trucks, cars, industrial plants and perhaps even
windblown dust -- seem to alter the normal pulsing of the
heart, the research indicated.
- At pollution levels commonly found in U.S. cities,
inhaling particles appears to disrupt the body's ability
to regulate the pumping of blood.
- As particulate counts rise on any given day, a vital
indicator, called heart rate variability, decreases in
some people, disturbing the beat-to-beat variations that
are designed to meet the demands of activities ranging
from sleep to exercise.
- The threat seems acute for senior citizens who have
arrhythmia -- a life-threatening condition of skipped or
premature beats -- or the combination of a weak heart and
lung disease such as asthma.
- One of the most frightening aspects of heart rhythm
irregularities is that they can kill quickly, without
- "Studies suggest that people are dying relatively
rapidly after you see an increase in particles. Sometimes
it's within 24 hours," said Robert Devlin, chief of human
studies at the clinical research branch of the EPA.
- In the last year, about a dozen major scientific
studies have turned up heart pattern changes in animals
exposed in laboratories and in senior citizens tested in
nursing homes. Several more studies are about to be
- According to one groundbreaking study of 100 patients
in Boston, conducted by the Harvard School of Public
Health, when particle pollution increased, senior
citizens with pacemakers suffered more arrhythmia.
- In another study, 26 senior citizens at a Baltimore
nursing home wore heart monitors for three weeks. Their
heart rate variability decreased on and around days when
particulate levels were higher, according to a study by
the University of North Carolina and the EPA.
- Some environmental health researchers and doctors say
cardiologists should advise patients who are at risk to
avoid exertion on days with high particulate counts.
- But Denton, one of the few cardiologists to study the
link between heart rhythm and particulates, said the
findings are too preliminary to base medical
recommendations on them.
- "Based upon the data we have, there's no need (at
this time) for us to change a patient's behavior or
treatment," said Denton.
- An as yet unpublished EPA study offers some of the
most compelling evidence so far that particles can affect
- Older volunteers were tested in special pollution
chambers using air collected in North Carolina. Even when
they were exposed to a dose found in many urban areas,
their heart rate variability was worse than when they
were exposed to clean air. Younger volunteers indicated
no heart changes.
- Although the changes detected in beat variability
"were not huge," some persisted for at least a day after
exposure and they are "very significant" for human health
because low heart rate variability often occurs in people
who are about to suffer heart attacks, said Devlin, who
directed the study.
- Researchers are trying to understand how particles
could affect the heart.
- The most popular theory is that when particles enter
the lungs, some part of the nervous system reflexively
sends an impulse to the nerve center in the heart that
controls contractions. This reflex raises the pulse rate
and lowers the variability of the heart rate.
- Also, inhaled particles cause lung inflammation,
which can release agents into the blood that are carried
into the heart. Blood also seems to thicken and clot
differently upon exposure, according to some
- Chronicle environmental writer Bill Dawson
contributed to this story.
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