bate
Moore, EPA, referenced in your letter contains results of this effort along
with the additional radiation measurements made during cleanup.
An additional
independent estimate of exposure due to external radiation was made by Smith
and-Moore for a child born on Bikini Atoll in 1970.
The 5, 30, and 70 year
values may be compared with Gustafson's estimates for the same times for
"External" exposure.
Part of the difference between the two sets of values,
for instance 3.33 rads in 30 years by Gustafson versus 5.3 rads for Smith
and Moore (5,275 mrads is 5.3 rads), comes from a correction made for external
radiation contribution from cosmic ray exposures in the reported data used
by Gustafson,
Note that the reported radiation levels in the Smith and
Moore report include natural sources.
report.
See footnote on page three of that
The cosmic ray measurements at Bikini made by the AEC Health and
Safety Laboratory (HASL) indicated a dose rate of about 3.4 wR/hr (microroentgens
per hour).
The 30 year exposure from this source would be 3.4 uR/hr x 24
hr/day x 365 day/yr x 30.
This would be about 0.9 R/30 years.
A proper
comparison of the two values, including natural background for each, would
be about 4,2 versus 5.3 rads.
It should be noted that these estimates do
not include any credit for reduction of exposure that may come from use of
coral gravel in the village area or from the shielding provided by housing.
Conversely,
the Smith and Moore estimates do not include any contribution
from internal radioactivity.
Since internal radioactivity comes through
the food chain the contribution to the total dose from that source will
change with time as locally produced foods become available.
We plan to
continue to make periodic surveys and to update dose estimates as new
information is obtained.
—_—
Such estimates will,
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of course,
include internal