3
{
{i
percent resulted from U.S.S.R. tests. This total energy release
is of use in estimating the amount of carbon 14 produced,
Incidentally, it is assumed that the carbon 14 is distributed
more or less uniformly around the worl.
te
Tabic 2 alee shows that of the 1938 million tons enery equiva-
tribute a much less biologically significant exposure to the aki)
Of the radionuclides that coatribute to external radiatio!
the moat important single one is cesium IS7. Its radioactiy
half-life is approximately 4 years. Thus, it is pussible ff
lent releasing fission products, about 161 milhon wns were
scattered globally.» Approximately two-thirds of this amount
originated from U.S.S.R. tests but will account tor about three.
cesium 137 to remain in our environment tu: ivig periods 4
of meteorological factors, This is because there will be morc
deposition in the North Temperate Zone from a nuclear detonation in the lower atmosphere at a northerly latitude than from
enough life so that most of the radiations are released with
of long-lived radioisotopes but at times have been thesource of
to estimate their contéibution to external exposures, The
quarters of the long-term fallout in the United States because
the same shot at an equatorial site. Atmospheric tests at the
Nevada Test Site have contributed very little to the deposition
relatively high amountsof short-lived radioactive materials including iodine 181 in the local environment.
foe
At the time of a nuclear detonation something like 200 differ-
time without losing much of its activity, althouph there can }
loas or reduction in availability of the material through norm
weathering processes. Still cesium 137 does have a sh
the lifetime of » man.
:
Al] radionctive materials in fallout, except cesium 137, whi
remain outside the body may be conveniently limped togeth
usually are called “short-lived” even though some do have ha
lives of upwards of one year. In spite of the fact that neat
all “of the radiation exposure received from these short-liy
radionuclides is completed within a year after the radion
ent radioactive substances are formed by fission. Additional
Ones are created by induced activity. Although these mnaterials emit only radiations with which we are already famil-
clides are created the total amount of exposure during ¢€
to be almost an impossible task to consider them individually
and in the aggregate for an appraisal of their health hazard.
Fortunately, for an analysis of the problem, most of the radio-
Cesium 137 also ia one of the iwo (carbon 14 is the othy
principal radionuclides deposited internally that irradi
nuclides are of little health consequences because of their
short radivactive nalf-lives or other characteristics such as
being highly insoluble. In fact, it is possible te estimate the
radiation doses to various organs of the body by considering
only five principal radionuclides in fallout that are deposite:!
internally, i.e., iodine 131, strontium 90, strontium 89, cesium
137 and carbon 14. To these interna! doses there must be
added those to the whole body due to the radiations from fallout material outside the bedy. The problem of estimating
these latter radiation doses is again simplified by considering
first cesium 137 and then lumping all of the remaining radia
nuclides togetherin the caleulations.
8. WHOLE BODY EXPOSURES
Background Information
Fallout particles consisting of inert materinin together with
the associated radionctive materials settle ty the earth’s sur:
face Where most of them remain and thus never Ket ingide ou
bodies. These -xternal, man made radonuchid. s, however,
will iriatiate the whole hedy by ther penetrating ganas
yearmaybe greater than that received from cesium 137 with
30 years.
the™whole body.
7
[t is not a major source of the total wh
radiation dose except in such cases as that of {’skimos wh
diet is largely caribou or reindeer meat.
The food oH
(lichen-ceribou-Eskime) reflects the relatively bigh surfy
contamination of cesium $47 on the Jichens.
3
The ‘Dote
ae ky,
lar—gamma rays and beta particles - it appears at first glance
4
{
radiations while their ahorter range betu parcicles will cor
The highest whule body exposures from nuclear wenpy
tests ever reported by the (United States were nbuut 173 ro
gene to 64 Marshailese following the March |, 1944 surf
nuclear test detonation at the Pacifie Proving Ground! F
situation resulted from u shifting of the winds so that the I¢
heavy fallout from this large yield surface List occurred
part, acrosa the islands instend of the open sea.
The Marshallese were evacuated, given coedival treaty
and returned to their home island of Rongelyp un dune 2f, 0
after radiation levels had subsided to acceptil le levels * (fig
From 1056 to 1962 about 24 children have been borne
normal -and four persona have died from natural caus
(One of these had been on another isiand and received G0 pa:
gens exposure.) Four deaths have occurred iti the compar
population of dike size. There were, of course, notice,
effects inmmediately after the lrradiation such as nauseg