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Upton Long island, NewYork 11973

(516) 282.

FTS 666°

Safety & Enwronmental Protection Divisicn


May 2, 1983
Mr. Charles B. Meinhold, Head
Safety & Environmental Protection Division
Brookhaven National Laboratory
Upton, New York 11973
Dear Charlie:

This is in response to your request to review portions of a report of Task
Group 7 of Scientific Committee 5/7 entitled, "“Thyroidal Carcinogenesis Following
Exposure to Ionizing Radiation".
I am familiar with background material related
to estimates of thyroid absorbed dose to Rongelap and Utirik Atoll residents who
were exposed as a result of the U.S. Pacific Weapons Testing Program. Specifically, my colleagues and I have reassessed thyroid ahsorbed dose.
Details of
the methods for the reassessment are in draft form and are going through initial
Rasults of the study, which are tentative, are given in Table One.
I have consulted with the Marshal! Islands Medical Program Director, William
Adams, M.0. in order to determine the total number of people and the total thyroid
effects since the time of exposure, March 1954. These data are given also in
Table One. The data include the most recent thyroid nodules detected in the
exposed population.
Or, Adams and I estimated the excess cases of nodules and thyroid cancer
based on Robert Conard's twenty-six year report (Co80). However, thyroid cancer
and nodule data from the Marshallese comparison populations are being thoroughly
re-examined by us due to possible low-level exposure of some of these people from

the testing program.

The average time at risk per irradiated subject was assumed

to be the time from radiation expasure on March 1-3, 1954 to time of surgery. OQne
person in the Utirik exposed population was assumed not to be an excess thyroid
Debate continues and a clear distinction of either carcinoma or adenoma
for this individual may never be resolved.
One implication of the dose reassessment was that the thyroid dose to each
population (see Table One) was from different relative amounts of external and
internal radiation.
Also, the internal radiation dose rete was different for

each atoll population due to differences in nuclide composition as a function of
fallout age. The greatest portion of thyroid ahsorbed dose was reassessed to be
from the shorter lived iodine isotopes [-133 and I-135 and not from I-131.

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