Health Risks of Ionizing Radiation: - Clark University

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MEDICAL EXPOSURES
3.1 Introduction
Approximately fifteen percent of the public’s total
ionizing radiation exposure is artificial and much of
this comes from routine diagnostic or therapeutic
medical procedures (Ron 2003). In the early
years of nuclear medicine, radiation was used at
dangerously high doses putting patients and medical
workers at risk. Radiation protection has improved
dramatically over the past century, and medical
professionals still find many useful applications for
radiation. Gamma radiation, applied at doses of 450
to 500 Sv in the 1940s and 50s, is still used today
at more conservative doses to identify and target
malignant growths. Iodine-131, the most common
beta emitter used for nuclear medicine, has been
used with doses of up to 1,000 Gy in the past. It is
still used to diagnose and treat thyroid cancers and
hyperthyroidism. X-rays are also, of course, a very
common diagnostic tool.
John Gofman was the first director of the
Biomedical Research Division at the Atomic Energy
Commission’s (now DOE) Lawrence Livermore
National Laboratory. Gofman (1996) stirred up a lot
of controversy when he conducted a review of all
major sources, mostly medical sources, of women’s
exposure to ionizing radiation in the US and related
them to breast cancer risk. Based on his analysis
of the atomic bomb survivor data he estimated that
approximately 75% of all breast cancers in the US
were caused by medical exposure. Gofman is a strong
advocate of the position that there is no such thing as
a “safe dose” and that the doses routinely received
by patients confer some cancer risk. Clearly it is this
type of concern that has led to changing medical
practice (for example more judicious and sparing
use of x-rays). On the other side of the coin, many
authors say that emphasizing the potential harmful
effects of therapeutic radiation is counter-productive.
For example, Schaefer et al. (2002) question this
type of inquiry noting that many patients would die
without the treatment that might eventually lead
to cancer later in life. Skolnick (1995) asserts that
any claims of carcinogenic effects of x-rays might
discourage women from getting mammograms, and
ultimately lead to higher mortality rates. Regardless
of any controversy we are still in the possession of
a large body of research that can help the decisionmaking
process.
Medical exposures can be divided into
characteristically different groups. Diagnostic
exposures are generally much lower than therapeutic
exposures. Exposures received by patients are
also different than exposures received by medical
professionals. Radiologists were one of the earliest
occupational groups to be exposed to ionizing
radiation. Their particular type of exposure is
characterized by cumulative, fractionated 1 , and
external low doses. Patients, on the other hand,
receive a wider range of doses depending on the
procedure, are exposed both internally and externally,
and receive exposures over a shorter time period
(including one-time doses). Another categorization
involves age at exposure; childhood exposures are
likely to carry a higher risk than adult exposures.
While precautions in the use of radiation for
medical purposes are becoming increasingly strict,
the possible long-term effects of any exposure are
a topic of intense debate and concern. The studies
reviewed here vary from those that focus on a few
1 A fractionated dose is one that is received as a series of small doses rather than one large dose.
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