EFFECTS OF IONIZING RADIATION
ings measured in air from the planar fission
product field. From the preceding paragraph
it is seen that an additional 50 to 100 rof laboratory radiation on an average of 75 r, probably would have resulted in some mortality.
Correcting this average value for geometry,”
it follows that the minimal lethal dose for man
exposed in a fission product. field is approximately 225 r measured in air.
It is possible also to estimate the added inerement of dose that would have resulted in
some mortality among the Group I people from
consideration of the minimumplatelet counts
observed, the platelet levels in dogs exposed in
the high sublethal range (20), and the estimated rate of decrease of platelet level with increasing dose in this dosage range. Such an
analysis leads to the same conclusions as those
derived from neutrophile data.
showed essentially identical degrees of depression. The lymphocyte counts of Groups I and
II were constantly depressed at a level of approximately 2000cells. Thus, while sensitive at
very low doses, this endpoint may be a poor
index of the degree of exposure at highercloses.
100
4 77
sol.
Z
:
80
The relative value of the several hematological determinations in estimating the degree of
exposure, as well as the approximate dose
ranges over which maximun. sensitivity for
each determination exists, can be estimated by
comparing the degree of hematological change
among the several exposure groups. The relative degree of change in neutrophiles, lymphocytes and platelets can be seen in Tables 4.2 to
4.5 and Figures 4.9 to4.12. Lymphocyte counts
were (lepressed appreciably even in the lowexposure Group IV. In the higher dose groups,
however, with widely different physical estimates of exposure the lymphocyte counts
*From geometric and depth dose considerations set
forth in Section T, 1 roentgen measured in air in a
fission product field would be expected to be equivalent
in its effect on man to approximately 1.5 roentgens of
penetrating x- or gamma radiation under geometric
conditions usually used for large animals in the lab-
oratory. Thus, the minimal lethal dose for man exposed to penetrating radiation under the usual laboratury conditions would be approximately 335 r. The
degree to which energy differences between the two
radiations may alter this ratio of effects cannot be
evaluated af present.
J
s
o
eo
a
t
= 50
KCONTROL GROUP A (91)
1
+
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i
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7
,
20
NEUTROPHILES
Cumulative- Age>5
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f
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py?:
© 60
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loo 9
o
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2
3
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4
5
6
7
_
6
9
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Il
12
13
14
NEUTROPHILES x10
FicureE 4.9.—Cumulative nettrophile counts for Groups
I (Rongetap) and I (.Ailinginae) and control Group
A at the time of marimnum depression.
100
390+
CUMULATIVE PER CENT
Peripheral Counts as an Index of Severity
of Exposure
‘
ee
oo .
)0CU
=
°
4.46
¢
3 70r crournusyy
3
3
=2=0.
GROUP I as oe é
G
nop|
ies
P
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T
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ge
TOR
60
mY
50}-
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f
a
fi
f
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wed ynie Tr (15)
80
30h
T
CONTROL GROUP A (91)
=
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a
60
i
LYMPHOCYTES
|] Curnulative Age>S
”
Pp
Py
L1
can
!
L
poi oy: |
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12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 72 76 80
LYMPHOCYTES x 10°
Figure 4.10.—Cumulative lymphocyte counts for
Groups I (Rongelap) and If (Ailinginac) and cortrol Group A at the time of marimunt depression,
The total neutrophile count of Group I was
consistently more depressed than was that of
Group II and the difference was of the orderof
500 to 1000 cells. However, day to day wide
fluctuations in the neutrophile counts occurred.
Accordingly, this endpoint appeared to beof
limited usefulness as an index of relative expo-