STANDARD FORM NO, 64
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Office Memorandum ¢
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UNITED STATES GOVERNMENT
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C. L. Dunhan, M. D., Director
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p> October 15, 1958
Division of Biology and Mdicine
FROM
‘ Gordon M. Dunning, Chief, Radiation Effects of Weapons Branch
Division of Biology and Medicine
XX
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SUBJECT: IODINE~131 MEASUREMENTS OFFSITE DURING OPERATION HARDTACK PHASE I
SYMBOL : DBM:REWB :GMD
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The USPHS offsite radiological monitoring during Operation Hardtack
Phase I on the islands of Rongelap, Wotho, Utirik and Ujelang is
the first time they attempted to make measurements of iodine~131
by drawing air through a cartridge filled with activated charcoal.
In a draft of their preliminary report it is stated, "These results
indicate that a significant internal exposure might occur to popu=
lations in off-site areas subject to fallout as a result of the
inhalation of I~-131. They further indicate that an off-site sampling
program may not be complete unless it does include a method for
determining I-131 levels in the air."
Since this will be a public document I can foresee the above statements causing undue concern by some readers. The first sentence
is not fully evaluative and could leave a scare in the minds of readers.
The second sentence might open the AEC to the criticism of why had
we not done this during past operations. I called Mr. Ernest Anderson
(who compiled the report) and discussed the problem with him. He
agreed to rewrite the paragraph.
For your information the collecting point showing the highest
iodine-131 air concentrations, outside of the Proving Ground, was
Rongelap.
The highest sample collected was 125.5 micromicrocuries
per cubic meter of icdine-]131 averaged over the 2) hours that it
was collected.
The total exposure to the thyroid from iodine-131l,
based upon the USPHS measurements, over the period of time of collection
(~3 months) that encompassed most of the fallout amounted to about
20 millirads.
This may be compared with the external gamma exposure
for the same period of time of about 285 millirads.
ce: Dr. Shilling
Dr. Western
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