EFFECTS OF IONIZING RADIATION
ings measured in air from the planar fission
product tield, From the preceding paragraph
it is seen that an additional 50 to 100 r of Jaboratory 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 increment of dose that would have resulted in
some mortality among the Group I people from
consideration of the minimum platelet 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 close in this dosnge range. Such an
analysis leads to the same conclusions as those
showed essentially identical degrees of depression. The lymphocyte counts of Groups I and
II were constantly depressed at a level of approximately 2000 cells. Thus, while sensitive ut
very low doses, this endpoint may be a poor
index of the degree of exposure at higher doses.
CUMULATIVE PER CENT
60
derived from neutrophile data.
i
10h
Ale
Lee.
t
Peripheral Counts as an Index of Severity
of Exposure
NEUTROPHLES 110°
Ficvre 4.9.—Cumulative neutrophile counts for Grou ps
1 (Rongelap) and {1 (Qilinginar) and control Group
The relative value of the several hematologi-
The rel-
ative degree of change in neutrophiles, lymphocytes and platelets can be seen in Tubles 4.2 to
+.5 and Figures 4.9 to 4.12. Lymphocyte counts
were depressed appreciably even in the low‘exposure (rroup TV. In the higherdose groups,
however, with widely different physical estimates of exposure the lymphocyte counts
*Fram geometric and depth dose considerations set
forth in Section {. lL roentgen ensured in air in a
fission product fletd would be expected to be equivalent
in its effect on man to approximately 1.5 roentgens of
penetrating x- or gamma radiation under geametric
conditions usually used for lirge animals in the laboratory,
Thus, the minimal lethal dose for man exposed fo penetruting radiation under che usual laboratary conditions would be approximately 335 r.
The
flegree to which energy differences between the twe
radiations imay alter this ratio of effeers cannot be
evnlauted at present.
cLat the time of metrinten depregsion.
CUMULATIVE PER CENT
“ul determinations in estimating the degree of
exposure, as well as the approximate dose
ranges over which maximum sensitivity for
each determination exists, can be estimated by
comparing the degree of hematological change
among the several exposure groups.
2
88 3 3 8 8
4.46
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12 16 20 24 28 32 36 40 44 46 52 56 60 6&4 6B 72 76 40
LYMPHOCYTES 2 10
Fietee
4£.1Q0—Cumalative
i
lymphocyte
eons
for
Crowne 1 (Rongelapy and TE liliaginaey and cone
trol Group Aoat the time of netrinieie depression,
The total neutrophile count of Croup DL was
consistently more depressed than was that of
‘Group [Landthe difference was of the order of
500 to L000 cells. Tlowever, day fo day wide
fluctuations in the neutrophile counts occurred,
Accordingly, this endpoint appeared to be of
lonited usefulness as an index of relative expo-