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No Apparent Increase in Cancer Deaths Among Three Mile Island Residents
No Apparent Increase in Cancer Deaths Among Three Mile Island
Residents,Report University of Pittsburgh Researchers
PITTSBURGH, April 28 /PRNewswire/ -- Radioactivity released
during the Three Mile Island (TMI) accident in 1979 does not appear
to have caused an increase in cancer mortality among people living
within a five-mile radius of the nuclear accident, according to
researchers at the University of Pittsburgh's Graduate School of
Public Health (GSPH). The findings were published Friday, April
28, on the website of Environmental Health Perspectives, a journal
of the National Institutes of Health's National Institute of
Environmental Health Sciences. The paper will also appear in the
June issue of the journal.
While several previous follow-up studies on the TMI population have
been conducted in the past, this one is the most extensive due to
its longer, 13-year time-frame and the use of information about
residents' lifestyles (such as smoking habits and education levels)
and everyday background radiation exposure beyond what was
caused by the TMI incident.
"This study helps put to rest the lingering question of whether the
residents of Three Mile Island are experiencing an increase in
cancer deaths as a result of the nuclear accident," said Evelyn
Talbott, Dr. P.H., associate professor, department of epidemiology
and principal investigator on the study.
The TMI incident occurred at a nuclear power plant near Harrisburg,
Pa., on March 29, 1979, when a reactor leaked small amounts of
radioactive gases. It is often referred to as the worst nuclear
accident in American history. Scientists have calculated that the
average person present in the area during the 10 days after the
incident was exposed to considerably less radiation than the
annual dose an individual receives from the everyday environment in
the United States.
The University of Pittsburgh study covered the years 1979-1992.
For demographic and lifestyle data on the individuals living in the
TMI area, researchers used information collected by the
Pennsylvania Department of Health in interviews conducted with
TMI residents within two months of the accident. Information
collected on these 32,135 individuals included education,
occupation, smoking status, residential history, medical history,
previous radiation exposure and daily travel in and out of the area
during the 10 days following the accident.
Investigators from the University of Pittsburgh determined these
individuals' maximum and likely gamma radiation exposure during
the 10 days after the accident and combined the results with the
interview data as well as mortality data from the Pennsylvania
Department of Health. In analyzing the information they used
standard calculations such as statistical modeling and standard
mortality ratios -- direct comparisons of the number of observed
deaths with the expected number of deaths in a general population.
Mortality indicators examined in the study included all heart
disease, all malignancies as well as specific cancers that are
known to be sensitive to radioactivity: bronchus, trachea and lung;
breast (women only); lymphatic and hematopoietic tissue (blood-
forming organs), excluding chronic lymphocytic leukemia and
Hodgkin's disease; and the central nervous system. Thyroid
cancer was considered, but no deaths were reported during the
study period.
Initial results indicated a significantly higher mortality from all
causes among the TMI population as compared with residents of
the surrounding three- county area. The largest contributor to that
mortality was heart disease. However, after adjusting for smoking
and education, the increases were no longer apparent.
"The effects of smoking and education levels on the incidence of
heart disease are well known," said Dr. Talbott. "When we
controlled for these risk factors, along with background radiation
factors, we found that the elevations in mortality were not note-
worthy."
Likewise, elevations in mortality from cancers of the bronchus,
trachea and lung were observed in women, as well as an increase
in lymphatic and hematopoietic tissue cancers in men, even after
controlling for background radiation exposure, education and
smoking. However, neither showed a significant dose-response
trend.
Investigators noted an increasing pattern of relative risk for breast
cancer in relation to increasing levels of likely exposure to gamma
radiation, suggesting a possible link between dose of radiation and
increased risk. However, they concluded that overall there was no
significant relationship between likely exposure to gamma radiation
and breast cancer mortality.
"A relationship between gamma radiation and breast cancer has
been noted in other investigations, but emissions from the TMI
incident were significantly lower than in other documented studies,"
said Dr. Talbott. "Therefore, it is unlikely that this observed dose
trend is related to radiation exposure on the day of the accident."
To fully explore the relationship between low-level radiation and
breast cancer, an in-depth case- control study would be
necessary, she said.
While the authors found no consistent evidence suggesting that the
low- dose radiation released during the TMI accident had a
measurable impact on the mortality of those living in the area for 13
years after the event, they acknowledge that further study is
warranted.
"Because the latency period for many cancers is 20 years or more,
continued follow-up on the TMI residents will provide a more
comprehensive look at their mortality, as well as morbidity, from
various cancers," said Dr. Talbott. The University of Pittsburgh
research team is currently analyzing data collected through 1999
on the same population.
Established in 1948, the GSPH at the University of Pittsburgh is
world- renowned for contributions that have influenced public health
practices and medical care for millions of people. It is the only fully
accredited school of public health in the Commonwealth of
Pennsylvania and is one of the top- ranked schools of public health
in the United States.
For more information about the GSPH at the University of
Pittsburgh, access the school's website at
http://www.pitt.edu/~gsphhome.
This research was supported by a grant from the Three Mile Island
Public Health Fund.
CONTACT: Kathryn Duda or Lauren Ward of UPMC, 412-624-
2607, or fax, 412-624-3184, or e-mail, dudak@msx.upmc.edu or
wardle@msx.upmc.edu.
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