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Pot
pb
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1953
1955
1957)
1959-1961
«1963
1954
1956
«1958
=—:19601962-1964
YEAR
Fig. 2—Annual deposition and accumulation of 13’Cs at Argonne.
137Cs in milk. In 1963 the highest level was not reached until the Novem-
ber sampling and was due to a general elevation of the '*’Cs levels in
all foodstuffs sampled. The sampling in 1964 has shown a gradual gen-
eral decrease in '’Cs activity through July, and preliminary results
from the October sampling indicates a continuation of the trend. The
highest ‘8’Cs level in the Chicago diet was reached in January 1964,
amounting to 240 pc/day, an increase of approximately 5 over the values
of 55 and 53 pce/day for April and July 1961, respectively.
The average '*"Cs body burden in 8 to10 adult Chicago residents is
also plotted in Fig. 4. These measurements were made by C. E. Miller
in the Argonne National Laboratory whole-body counter. °:’ The body
burdens are expressed in picocuries of '"Cs per gram of potassium.
The biological half-life of ‘Cs in the human body (approximately 100
days in adults) causes a lag between body burden anddietary level.
Hence the lowest body burden actually occurred after the resumption of
nuclear testing in 1961. Likewise the body burden is still increasing
into 1964, although the dietary level has begun to decrease. The whole-