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HTDS Guide > Hanford
History > Why the HTDS Was Conducted
HTDS Guide
Why the HTDS Was Conducted
The main reason why the HTDS was conducted is that the public, health
officials and scientists were concerned about the possible health
effects of Hanford's radiation.
Thyroid disease was a particular concern because iodine concentrates
in the thyroid gland and the DOE documents showed that large amounts of
iodine-131 were released from Hanford. In response to public concerns,
Congress directed CDC to conduct a study of the effects of Hanford's
iodine-131 on thyroid disease.
Many people ask, "Didn't we already know that Hanford radiation
causes thyroid disease?" Over the years, many studies of other
populations have provided compelling reasons to suspect that the risk of
thyroid disease might have increased in people who were exposed to
Hanford's iodine-131.
Nevertheless, the published literature left room for doubt, since
none of the studies examined circumstances quite like those of the
Hanford experience. The following are ways other radiation studies are
different from the Hanford situation:
Type of radiation exposure – External irradiation by gamma
rays (such as the atomic bombings in World War II) or x-rays used in
medical treatments may have different effects than iodine-131.
The people who were exposed – People who received iodine-131
for treatment or diagnosis already had, or were likely to have, thyroid
diseases, while people exposed to Hanford's iodine-131 were a general
population, including some people with good health and some with poor
health.
How big the doses were – Doses of iodine-131 used for medical
treatments are much higher than anyone is likely to have received from
Hanford's iodine-131. Doses from Chernobyl's fallout were higher as
well.
How long people were exposed – External irradiation typically
occurs within a few seconds or minutes. Medical exposures of iodine-131
typically occur over days to weeks. Exposure to Chernobyl's fallout
occurred from weeks to months. In contrast, many of those exposed to
Hanford's iodine-131 were exposed over a period of several years.
Because other studies have addressed situations different from
Hanford in important ways, it was necessary to study people who were
actually exposed to Hanford's iodine-131 in order to get the most
reliable answer to the question of whether thyroid disease had been
increased by Hanford's iodine-131.
No study can determine the cause of an individual case of thyroid
disease. However, an epidemiological study, such as the HTDS, provides
the best way to determine whether disease has increased in a population
exposed to a potentially harmful agent such as radiation.
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Purpose |
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Estimate type and amount of radioactive
materials released from Hanford. |
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Model how radioactive materials moved through
the environment and food chain. |
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Develop computer software for estimating
individual doses. |
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Estimate radiation doses to representative
individuals in the Hanford region. |
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Purpose |
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Study the risk of thyroid disease among persons
exposed to radioactive iodine-131 from Hanford. |
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Conduct of the Study |
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Began in 1987; final report issued in 1994. |
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The study was directed by an independent
technical steering panel selected by deans of research
universities in Washington and Oregon. |
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The study was conducted by Battelle Pacific
Northwest Laboratories originally under contract with the U.S.
Department of Energy (DOE). Management responsibility was
transferred to CDC in 1993. |
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Conduct of the Study |
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Began in 1989; final report issued in 2002. |
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Scientific and technical work were performed by
the Fred Hutchinson Cancer Research Center under contract with
CDC. |
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The research team used HEDR computer software
together with information provided by HTDS participants to
estimate individual radiation doses to the thyroid. |
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