4
= Oe ERB JovGvoassgi
*
7
x.
aye
spats
rats
3
wie
.
j
5
A
x
t
|
wes
tat
oN
Be
‘
4
54
RADIATION STANDARDS, INCLUDING FALLOUT
39
Sr? in milk and man has a large component related to uptake in
plants of accumulated Sr® in the soil. This is evident from the fact
that milk values which peaked in the early summer of 1959 had fallen
by no more than a factor of about three by the summer of 1961.
It now appears that the overall ratio of Sr®° to calcium in the infant
bones in this country to the Sr® to calcium ratio in their diet is about
0.5. Studies on 1- to 2-month-old infants suggest the ratio may be
as high as 1.0, insofar as milk is concerned. By early childhood it
has fallen to 0.25. Whether this change reflects change in diet habits
or it is related to the changes in the physiology of absorption of Sr®°
from the gastrointestinal tract, or merely reflects less demand for
calcium-like elements, is not certain.
The most recently available data from human bones in the United
States indicate an average of about 3 strontium units in infants in
1961 and 1 in adults. A strontium unit is one micro-microcurie of
strontium 90 per gram of calcium.
Values ranged up to 5.1 in infants.
These data are consistent with
UK mean values of about 3 and 0.3 for 1960.
Most of the data on
bones and diets of Eskimos in Alaska run about 25 percent higher than
for the United States as a whole. Further, a few samples of adult
Eskimo bone are about four times these figures suggesting that certain individuals are eating food, presumably caribou meat, which is
exceptionally high in Sr®. No bone data are available from a known
THETACRCREipCBESTAR” eRUREGE
OSE
caribou-eating tribe, but Sr®° in urine from adult persons in such tribe
fe
1A ts,
New York City milk. Milk seems clearly to have been the principal
catoil clanann
e
wath Le nin
e
dle ee Seple ee aae
suggests that bone deposition is four times that in persons on a cariboufree diet. Samples of caribou meat have shown as much as 190
strontium units. Meats are relatively low in calcium compared to
milk. Swedish data on Cs’ in reindeer meat have shown exceptionally high Cs#"/K ratios. In fact, some individuals are at or shghtly
above the generally accepted permissible levels for the population.
It was expected that Cs"? and Sr® in the diet would begin another
rise this spring. In fact, the most. recent data from the Argonne
National Laboratory showsa rise in Csair concentration though not
at an alarming rate.
By 1957, data had accumulated indicating that tropospheric fallout resulted in sufficient 1* in food that it could be measured in
human urine, and human and animal thyroid glands.
The 1959 hearings brought out the importance of I?" in cows’ milk
as a source of I*™ in the thyroid gland of infants. Available data on
I** in milk supplies indicated that the average U.S. infant received
0.1 to 0.2 rad exposure to the thyroid gland in the period May—September 1958. No more radioiodine resulting from weaponstests was
observed in milk supplies until October 1961 following the resumption of nuclear weapons testing by the U.S.S.R. Actual measurements of Iin New York City infants, October-December 1961, 1ndicate an average exposure of about 40 millirad. Infants in certain
other cities such as Omaha, Nebr., presumably had higher exposures
in view of the fact that I*** values in milk were 2 to 3 times those for
See
cD NP ane oe
source of the [12,
As far as our knowledge of the biological effects of fallout is concerned, the newer observations al} indicate that the hypothesis of
straight proportionality of effect irrespective of dose and dose rate
ON tats