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of 0.2 rep (March to May 1956).
sion March 1956 was an accumulated exposure
Fg
3%
8
During this period the maximum activ-
SgRe
Sak
Ss
2
day.
The average radiation to all range-fed
:
.
soe
2
SAS
sad d
Ze g
s g<
S36
2é é
garithmic scale as a
The dashed horizontal line, A~B, i
um and other long-lived radioact:
§
g
<2
<*
3
g3
.&
cattle
is close to 0.01 repep P per day
.
ad for this entire
.
period, Thus the maximum exposure of bovine
thyroid was (June 6, 1956 to October 11, 1956)
s
>
2
5
=
a
°
38
Siig 33
:.
& i
gyi
BBRE
Tp
:
we
_
bee
Fane
“"
ee
|
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‘|
bh
aresots evs vis scdomnm
.
ae
3
gx
B.&s
east
= &
Be
2:
3 = pESE ce
$.2 Bs 33 g
ose 3 32 5 =
sisex 2? >
& E g z3 & 2s
S Zz
oo
S8
1
|
|
day
mucigm
6235
267
BBR
aneigtt
aamapte
BT 4em
lehiole
thyroid
OT am
43 emo...
concentration}.
Median lowof thyroid 15 content in range-fed animals
182
-.. . -..
1181 6.409 4.3 —¢m
27 em
Average
tremensela
“ATage
pale
Median JeveLof thyraid 1!) content in feed lot-fed animals
52 2... 2...
289 0,008 43 em
27 gm
"nianificant)
Number
68 initial count .. .
68 recount --.
ait
6.214083 4.3 em
5. 18:40. 76
_
103 Lig taitt
(O81
16 em
Hrerence no
t
half-lives of radioiodine (lapse of at least 28
days). Even though any one of the human
thyroids contained too little 1! to be detected,
it was possible to make a finer estimate of the
TI content in human thyroids, by combining
Samples were counted an average of 3.8 days
after death, therefore if human thyroids had
1.03 counts of 1 per sample the average IM
burden of human thyroids would be 0.0006
millimicrocuries per gram.
Radiciodine levels in human thyroids either
individually or as a group-measure were not
significantly established in the same time
period whencattle [ content in thyroid tissue
ranged up to 2.7 millimicrocuries per gram
thyroid.
time periods: One of low cattle I" content
(January 1956 to March 4, 1956) and the other
of the period (June to October) when range
cattle thyroids were measurable as having 2to3
thousand counts per minute per total countable
thyroid had appreciable [' content comparable
with beef thyroid. It measured 0.025 millimicrocuries per gram, which is about 1/20th
of the bovine I™ concentration, during this
time period. This man, upon investigalion
thyroids and establishes that the average
human thyroid concentration of !is probably
half-lives of I! earlier. Thus the observed
Jevel is entirely within the expected value for
all the human measurements according to 2
gos 2
gs .
&8 ae
es 5
Res 3
= Me
Bs 3 3
s .2
g&s y BSis
counts
somple per
beef or human contained similar levels of
Humanand beef thyroid were measured for
radioactivity both initially and after 4 or more
3s
Nuraber
1 (highest
measured .
Humanthyroids—
natural radioactivity. Additional beef thyroid
radioactivity was identified as ]™ byfollowing
the decay of radioactivity which uniformly
gave an 8-day half-life to the radioactivity
above the natural background.
=
June to October 1956
.
ue
—
Bovine thyroids
*
|
7
7
ge
.
Thyroids -having more than 1 myge/gm:
Acerage
Average
mera
approximately 1.9 7.
Human thyroids at all times of collection
were in the range of 1/1000ththe level of range-
fed beef thyroid I content. During times
when Icontent was not detectable in either
humansor cattle, the thyroid gland tissue from
163
.
Be
An integral dose for the Bikini tests is estimated as including e time from May
5 to October
1956.
s
;
Ef
2%
&e
ities corresponded to 0.010 to 0.028 rep per
s
‘
1
lapse of time between last range feeding and
.
.
Thus, much of the variance in
:
ye
.
range-fed animals may be iodine decay during
.
t
"
the pre-slaughter holding in stockyards. The
cattle thyroid irradiation for the Kussian exploslaughter.
=
S28
remem
BE
38
2
8 3
& 3
ose
ae ss
= 3
g& g
ges
2 &
I
we
'y include the radioactivity of the glass vial
‘ground has been subtracted.
on en rere i
.
UPTAKE OF IODINE-131 IN HUMAN AND BOVINE THYROIDS
THE SHORTER-TERM BIOLOGICAL HAZARDS OF A FALLOUT FIELD
Thus all radioactivity in cattle thyrotds above line
162
sample. By counting the human thyroid
specimens initially and after decay, the following comparison fails to detect Iin human
less than 1/1000th the maximum level observed
in thyroids from range-fed cattle.
It is interesting to note that one human
through the attending physician, was found to
have boen given a tracer dose (2.5 ye I) 67
days preceding death, or approximately 8
this length of decay of I".
Tt is possible that human thyroids do not