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TABLE 4.—ESTIMATED RELATIVE INITIAL AVERAGE Bopy CoNTENT
(Compared to Body Content of I~-131)
Radioisotope
|
Monitored group of natives
J-131*........ 1
Sr-89. ee 0.04
Ba-140........| 0,006
Ca-46........ ' 0.0034
Ru~103, 106...) 0.0005
Americans
unit of activity. .| 1
unit of activity.
| 0.023
0.015
| 0.0023
: 0.0009
[*From the data on the relative yields of short-lived radicisetopcs
of iodine, it was estimated by LASL that the initial body dose rate,
.
“-
It is reasonable to expect human intake of I-131 to be largely through milk. Data obtained
by Brody at the U. of Missouri indicate 10% iodine transmission into cows’ milk. Experiments
at Hanford on sheep suggest that approximately 20% of the iodine ingested by these animals
was transmitted to their milk.
G. Radiological effects of various isotopes inside body:
1. S7-89 and Sr-90:
The currently available experimental data on the toxicity of Sr-89 and Sr—90 are tabulated
in Appendix D. Skeletal dose rate has been caiculated under the arbitrary assumptions of
skeletal weight equals 144, body weight and retained dose equals 50% of injected dose (unless
further data on retention available).
Considerable information is available on the acute effects
oi these isotopes, but only a very little on the chronic effects.
The best present estimate for chronic Sr—90 toxicity in humans is based on human Ra
data converted to Sr-90 by comparisons of Ra and Sr—89 or Sr-90 in animals. Brues hasestimated, both from the large experiment on mice in Appendix D and from other small scale
experiments on rats, rabbits, and dogs, that Sr-90 would be 1;, as hazardous to humans as Ra
(microcurie basis).
Human data on chronic Ra toxicity are now available ** for 50 individuals who were given
Ra salts either orally or intravenously for medical purposes, and 28 luminous dial workers who
ingested Ra salts and salts of MsTh and RaTh. The groups include individuals with current
Ra burdens of 0.01 to 22 uc. None of the 13 cases of 0.4 wc or less (including 7 between 0.2 and
0.4 »c) shows any symptoms after 18-30 years. Skeletal changes have been shown radioeraphically in several cases of body content between 0.5 and 1 pc, and in almost all cases of
greater body burden. Hight of the 28 luminous dial workers and 5 of the 50 medically “treated”
individuals developed malignancies, the lowest associated burden being 0.5 yc, and the next
two lowest, 0.8 »c. Several patients have carried a body burden of greater than 10 »e for over
20 years andarestill alive.
Since 15 individuals in each group, dial painters and medically “treated” patients, were
discovered as a result of symptoms, conclusions deduced from these series are perhaps somewhat biased in the direction of excessive hazard.
Using the Ra to Sr--90 conversion factor of 10, one would estimate from these data that
1 ze Sr-90 adult body burden at 20 years after exposure would be safe, 5 uc would begin to produce radiographically demonstrable skeletal changes, and 50-200 »c might correspond to the
LD 50 in 20 years.
Footnote references on pp. 42-43.
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computed on an energy basis, from such isotopes would be greater
than that from I-131 by a factor of 100, and that the integrated dose
from such short-lived isotopes of iodine would be greater than that
from I-131 by a factor of 2.]