-13._
C.
Direct Measurement of the Stratospheric
Fallout Content.
Direct measurement by means of high-flying
balloons has shown that the stratosphere does indeed have
about the fallout anticipated in it.
In addition, it has been found in these meas-
surements that the radiocesium, Csl37, occurs at about
the same level as Sr90 in millicurie units indicating
there has been no serious fractionation of the two
fission products by the fallout mechanism.
It further
points out that the sampling of the stratosphere is
a practical matter and that measurements can be made
of the stratospheric content of radioactive fallout.
Such data should greatly assist the whole study of
fallout.
D.
Radiocesium Assays for the, Biosphere. ..
Recently a technique for measuring Cs137 in
biosphere samples, weerticularly in human bodies, has
been developed by Mr. L. D. Marinelli of the Argonne
National Laboratory//.
It has been found that about
four-millionths of one millicurie is present in an
average adult. This corresponds rather well to the
expected amount considering the short residence time
of radiocesium in the body, which is about 3 months,
and the expected precipitation rate, which is taken
to be equal as a first approximation, to that of
radiostrontium. The radiocesium, of course, constitutes no hazard, amounting in radiation dosage to a
small fraction of the amount present in the blood in
the form of that received from the ordinary potassium
present in the body.
active.
Potassium is naturally radio-
It is interesting further evidence, however,
6/ "General Mills High Altitude Balloon Filter Samples,®
7/
Memorandum by A. P. Hardy and S. Tarras, New York
Operations Office, July 2, 1956.
"Gamma—Ray Activity of Contemporary Man," Science,
124, 122, July 20, 1956.
.
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