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and that investigators have reported halftimes, for adult groups, of about one day for a
small fraction of the cesium--137 intake (about
10 percent) and values between about 60 ans
180 days for the major portion of the intay
While part of the difference in yalues from
various investigators may lie in the realm of
factors of instrumentation, calibration, laboratory technique, etc., the measured values
generally appear to represent real difference:
among individuals. The range of values
obtained by a single investigator for a ero:
of subjects must involve many biological and.
environmental factors for which there is litt
information. No attempt will be made t-

identify these factors except for the possible

influence of age on the biological half-time of _

cesium-187 in man (age may be an indirect
factor).
The data are meager, but figure 1 suggest.

"that the value of T, for those groups und
about 20 to 25 years of age decreases with 1:
_and that T, may be as low as 6 to 7 da:
for infants a few daysold. For the four infan'in figure 1, the average value is about 15 day:

which agrees with Pendleton’s average of 1°

days for five infants.

One additional feaiure in the data is po.sib) °
significant. For the age groups reported, |
investigator (from the available reports) hv —
reported a value of T, greater than 70 days‘
groups under 25 years of age or a valuc
than about 50 to 60 days for groups aver
years of age.

Radiolog;cal Health

4

f Rh.

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