Pregnant Worker.p65

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					                                                 Your link with current trends in radiation dosimetry

                                                 RADIATION PROTECTION FOR THE
                                                 PREGNANT WORKER
A candid interview with Stewart C. Bushong, Sc.D., Professor of Radiologic Science, Baylor University, College of Medicine
Editor’s Note: Since the publication of this article, regulations have been enacted requiring that dose to the embryo/fetus of declared pregnant
workers not exceed 500 mrem over the entire pregnancy. See Title 10 Part 20 of the Code of Federal Regulations or Landauer’s Nexus on the
new 10CFR20 for details.

Nexus: It is reported to us from                 mately 2 Gy (200 rads) no one will                Dr. Bushong: There are basically
time to time that a pregnant                     die; therefore, 2 Gy is said to be                two. Radiation-induced malignant
radiation worker was furloughed                  the threshold dose for radiation-                 disease,
or dismissed from her job because                induced acute lethality.                          leukemia and
the employer became concerned                                                                      cancer, and
                                                 Radiation-induced leukemia
over possible radiation injury to                                                                  genetic change.
                                                 responds in a nonthreshold fash-
the unborn child. Is this proper
                                                 ion. If a large population were to                Nexus: What about congenital
procedure?
                                                 receive a 2 Gy dose, a small per-                 abnormalities?
Dr. Bushong: Absolutely not.                     centage of that population, less
                                                                                                   Dr. Bushong: That type of re-
There are a number of protective
                                                                                                   sponse to radiation is a threshold
devices and administrative proce-
                                                                                                   type effect and certainly does not
dures to ensure that no harm will
                                                                                                   occur at doses in the range of the
come to the unborn.
                                                                                                   MPD.
Nexus: Is there a safe dose to
                                                                                                   Nexus: Then, for example, what
which a pregnant worker can be
                                                                                                   is the risk of a newborn develop-
exposed?
                                                                                                   ing a childhood malignancy follow-
Dr. Bushong: There is an easy                    than 5%, would develop leukemia                   ing exposure to the MPD?
response to that question, but the               several years later. Following 1
                                                                                                   Dr. Bushong: To the best of our
true situation is much more                      Gy, approximately half of that
                                                                                                   knowledge, the absolute risk of
complicated. The easy response is                percentage would develop leuke-
                                                                                                   radiation-induced cancer and
that the maximum permissible                     mia. Following even lower doses, a
                                                                                                   leukemia in adults is approxi-
dose (MPD)—5 mSv (500 mrads)                     proportionately lower percentage
                                                                                                   mately 30 cases in a population of
during pregnancy—is safe.                        would be expected to develop
                                                                                                   1 million, each of whom has re-
                                                 leukemia. At doses in the occupa-
Nexus: Is this radiation level, 5                                                                  ceived a dose of 1 cGy (1 rad);
                                                 tional exposure range, there is a
mSv for nine months, considered an                                                                 therefore, following 5 mGy (500
                                                 statistically predictable level of
absolutely safe level of radiation?                                                                mrad) to 1 million persons, one
                                                 radiation-induced leukemia.
                                                                                                   would expect 15 cases or 1.5 cases
Dr. Bushong: Simplistically, yes.                However, it is so small that it is
                                                                                                   per 100,000. That estimate is for
But since we know that some                      not measurable.
                                                                                                   adults receiving an abrupt expo-
possible radiation effects on the
                                                 Nexus: So even radiation doses                    sure, not one that is extended over
fetus are nonthreshold, there is
                                                 less than the MPD have a prob-                    time such as that which we re-
theoretically a vanishingly small
                                                 ability of producing an effect?                   ceive occupationally. It is, there-
probability of response following
                                                                                                   fore, a worst case estimate. To
even lower radiation levels.                     Dr. Bushong: Yes, but the prob-
                                                                                                   worsen the estimate further, let’s
                                                 ability is so very, very small that
Nexus: What do you mean by a                                                                       assume that the entire MPD was
                                                 even if all pregnant workers
nonthreshold type of effect?                                                                       received during the first trimester
                                                 received the MPD, no injury to
                                                                                                   of pregnancy when the risk is
Dr. Bushong: Let’s first consider                any unborn child would be ex-
                                                                                                   approximately ten times higher.
a threshold type effect. Death,                  pected.
                                                                                                   Therefore, one might expect as
following a single high exposure to
                                                 Nexus: Can you be more specific?                  many as 15 cases in 100,000. The
radiation, is a threshold type
                                                 First, tell us what radiation re-                 total number of active radiologic
effect. At doses less than approxi-
                                                 sponses are we talking about?                     technologists is approximately
                                          Dr. Bushong: The principal                absolutely necessary, especially if
                          Page 2          protective device is one that is          temporary help would have to be
                          Concluded       routinely used anyway, the lead           employed to accommodate such a
                                          apron. A radiologic technologist          move.
                                          receives nearly all occupational
100,000, certainly less than 1% of                                                  Nexus: Anything else?
                                          exposure during fluoroscopy and
whom would be pregnant at any
                                          portable radiography where                Dr. Bushong: Yes. You can
time, so that the excess risk of
                                          protective aprons are used. These         provide the pregnant employee
such a harmful effect is only about
                                          aprons do just what they are              with an additional radiation
1/10th of a case.
                                          designed to do—reduce the radia-          monitor and instruct her to wear
Nexus: You mentioned genetic              tion dose to near zero.                   it at waist level under the protec-
effects.                                                                            tive apron. This monitor should be
                                          Nexus: Can you be more specific?
                                                                                    identified as “baby badge” or “fetal
Dr. Bushong: The probability of a
                                          Dr. Bushong: Very few radio-              badge.” This is not specifically a
harmful genetic effect is only
                                          logic technologists will exceed an        dose reduction measure, but
about 1/10th that for malignant
                                          occupational exposure of 1 cSv (1         rather to define more clearly the
disease and, therefore, it is of even
                                          rem) in a nine-month period as            fetal dose that is actually received.
less concern.
                                          recorded by a radiation monitor
                                                                                    Nexus: So do we understand that
Nexus: So if you consider the             positioned at collar level above
                                                                                    there are no circumstances under
MPD to be a safe dose, what dose
                                                                                    which a pregnant employee should
is considered to be dangerous?
                                                                                    be terminated because of concern
Dr. Bushong: Let’s use the                                                          over her radiation exposure?
example of a patient who has been
                                                                                    Dr. Bushong: None. Furthermore,
exposed to diagnostic x-rays
                                                                                    there is no situation in which the
during pregnancy. If the exposure
                                                                                    pregnant employee should feel
occurred during the first trimes-
                                                                                    that she is placed at undue risk.
ter, we would not recommend an
                                          the protective apron. Most will get       That situation simply doesn’t
alteration in the pregnancy at
                                          less than half of that, but for           exist. With proper attention to
doses less than about 10 cGy (10
                                          simplicity let’s assume 1 cSv (1          routine radiation protection
rads). Late in pregnancy, the safe
                                          rem). The dose to the abdomen             practices, the pregnant worker
dose rises to approximately 25
                                          under the protective apron will be        should not feel any more concern
cGy (25 rads).
                                          approximately 5% of the collar            for her unborn than she does
Nexus: Okay, you indicate that            dose, or 500 µSv (50 mrem). Be-           following the normal experiences
the MPD is a safe dose so there-          cause of overlying maternal tis-          and exposures of everyday life.
fore protective measures are not          sues, the dose to the fetus will be       Stewart C. Bushong, Sc.D., received
necessary. Right?                         only about 1/4th of the abdominal         his B.S. in physics from the
Dr. Bushong: Wrong. Because               entrance dose, or approximately           University of Maryland. He went on
some responses of the fetus to            125 µSv(12.5 mrem). This is a             to spend four years as a nuclear
radiation are nonthreshold in             vanishingly small exposure and            reactor physicist for the U.S. Public
                                          certainly absolutely nothing to be        Health Service and at Westinghouse
nature, it is important that we
                                          concerned about.                          Atomic Power Laboratory.
reduce the fetal dose as low as
possible.                                 Nexus: Can anything else be done?         In 1966, he earned his Sc.D. at the
                                                                                    University of Pittsburgh and joined
Nexus: How do we do this?                 Dr. Bushong: Yes. There are               the staff at Baylor University, College
Through the use of the devices            perhaps two other procedures              of Medicine. Currently, he holds the
and administrative procedures             that should be followed. If staffing      position of Professor of Radiologic
you mentioned earlier?                    permits, one could shift the preg-        Science in the school’s Department of
                                          nant employee from her normal             Radiology.
Dr. Bushong: Yes. And, perhaps
we could consider the largest             position to a job with potentially        Bushong has authored more than 100
                                          lower exposure. For instance, the         scientific papers and has written 10
population of potentially pregnant                                                  books. One of his books, “Radiologic
radiation workers, radiologic             radiologic technologist could be
                                          assigned to radiography only, and         Science for Technologists,” is the
technologists, as an example.                                                       popular standard in x-ray technology
                                          removed from the fluoroscopy
Nexus: What protective devices                                                      training.
                                          schedule and portable work.
can be employed?                          However, such a move is not
    Landauer, Inc., 2 Science Road, Glenwood, Illinois 60425-1586 Telephone: (800) 323-8830 Facsimile: (708) 755-7016

				
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posted:12/21/2011
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