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Chaj?ter IV
THE CRITERIA OF RADIATION EMPLOYED
IN THE STUDY
THE present chapter will be devoted to an ex-
amination of the available and practical criteria
for evaluating the amount of radiation received
by individuals exposed in Hiroshima and Naga-
saki to the effects of the atomic bombs.
4.1 The complicated nature of the injuries
sustained by some s~ruivo~; "diluter e Sect" vs.
"radiation; eJect." The detonation of an
atomic bomb may be harmful to persons in its
vicinity for a variety of reasons. The air blast
may inflict injury directly or secondarily, from
flying debris and falling walls and roofs. The
thermal radiation produces severe burns, and,
in addition, further burns may be sustained as a
result of fires kindled by the explosion. Under
the conditions prevailing in Hiroshima and
Nagasaki, serious secondary infection of these
burns was the rule rather than the exception.
Finally, the explosion is accompanied by the
release of a variety of deleterious high energy
radiations, particularly X-rays, gamma rays, and
fast and slow neutrons. The complex manner in
which these various noxious agents affect per-
sons exposed to the explosion of an atomic
bomb is well depicted in the Report of the Joint
Commission for the Investigation of the Effects
of the Atomic Bomb in Japan (Oughterson
et al., 1951~.
Moreover, in the wake of such a cataclysmic
event as the detonation of an atomic bomb
over a city, come certain well recognized ac-
companiments of any large-scale disaster, not-
ably, disturbed nutrition and increased mor-
bidity from disease. These "disaster effects" are
here so complexly intertwined with the primary
event that it will be difficult, if not in fact
impossible, in any analysis of atomic bomb
sequelae, to effect a realistic and completely
satisfactory separation of the relative importance
of what transpired at the time of the bombing
33
and what transpired in the next several months.
In this particular instance, the general prob-
lem of disentangling primary and secondary
effects upon the manner in which pregnancies
are terminating is still further complicated by
the fact that certain delayed somatic effects of
irradiation have been shown to occur in the
population under study. The "late" effects in-
clude leukemia (Folley, gorges, and Yamawaki,
1952; Lange, Moloney, and Yamawaki, 1954;
Moloney and Lange, 1954) and cataracts (Co-
gan, Martin, and Kimura, 1949; Sinsky, 1955~.
Although both of these conditions affect only
small numbers of the more heavily irradiated
survivors, they do occur in the group most
critical to this study. It seems entirely possible
that there are other late sequelae, still unde-
fined, which may influence reproductive be-
havior.
In subsequent chapters an attempt will be
made to correlate exposure history with a variety
of possible indicators of genetic damage. How-
euer, it mall be clearly understood that if a sig-
rtiicant association can be shown to exist, this
demonstration' of itself does not enable one to
conclude that exposure to the bomb has genetic
consequences; the latter conclusion is justified
only if an ef ect remans after the various other
favors associated with the irradiation have beer
Aligned their proper role.
4.2 The question of residual radiation fol-
lowing art atomic bombing. The ionizing
radiation of an atomic bomb explosion is re-
leased over a relatively brief period, of approxi-
mately 100 seconds. However, as a result of
the contamination of the area due to the fall-out
of radioactive by-products of the explosion, as
well as secondarily induced radioactivity, there
is a certain amount of residual radioactivity in
an area over which a bomb has been detonated.
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34 Genetic Efects of Atomic Bombs Chapter IV
The estimation of the amount of residual radia-
tion at Hiroshima and Nagasaki presents many
difficulties. The distribution of residual radiation
around the hypocenter in the two cities was
asymmetric, the exact pattern depending on
local meterological details (Warren, 1945;
Warren, 1946~. Based on the observed residual
radioactivity at intervals following the bombing,
Warren (1945) has estimated that the maxi-
mum irradiation due to residual radioactivity
was in Hiroshima during the first 60 days fol-
lowing the bombing the equivalent of 4.2r, and
in Nagasaki during the first 47 days, the equiva-
lent of 14.2r. Wilson ( 195 1 ), using similar
data, has suggested that in Hiroshima the maxi-
m~m cumulative dose of residual radiation at
distances greater than 1,000 feet (300 meters)
was not more than for, with somewhat higher
doses prevailing in Nagasaki, especially in a
fall-out area extending eastward from the
hypocenter, where the cumulative dose from
radioactivity might have amounted to 100r.
Irradiation of this latter degree would only be
experienced by individuals establishing continu-
ous residence near ground zero immediately
after the bombing, a situation which rarely, if
ever, obtained, although persons coming into
the area later or intermittently might of course
receive lesser amounts. On the other hand, there
are persistent Japanese reports of members of
rescue parties and others not actually in the two
cities at the time of the bombing later develop-
ing symptoms of radiation sickness, or leuco-
penia (Japan Science Council, 1951; Appendix
18, ABCC Semi-Annual Report, 1 January
1952-30 June 1952~; this would suggest a
dose of 200r (cf. Sec. 4.8~. This apparent con-
flict of evidence remains unresolved at present;
we shall adhere for the time being to the more
conservative view concerning residual radioac-
tivity. By and large, individuals exposed to the
effects of the atomic bombs tended to leave the
area as rapidly as possible. Accordingly, for the
purposes of this study it has been felt that
although exposed individuals and also those
entering the city immediately after the bombings
may have been subjected to some residual radia-
tion, by comparison with the amount absorbed
by those present at the moment of the explosion,
this was on the average small and could be dis-
regarded. Moreover, it might be pointed out that
in the case of an individual engaged, e.g., in
rescue work in Hiroshima or Nagasaki during
the first few days following the bombing, it
appears impossible to reconstruct his behavior
during those several days in a fashion which
would permit a realistic estimation of the total
radiation dose which he absorbed during this
period.
4.3 Factors determining the nature of the
radiation data collected ir; this study. At the
time this study was being planned, in 1947, no
data of any sort concerning the types of radia-
tion emitted by an atomic bomb and the dis-
tance-dosage relationship were available to any
of those closely connected with the program.
In retrospect, in view of the many revisions the
physical estimates have undergone, this is per-
haps fortunate. Be that as it may, under the
circumstances extensive recourse was had to
the Endings of the Joint Commission, then
available in preliminary form. These findings,
as later published (1951), established the fol-
lowing facts of importance in the design of
the present observations:
4.3.~1 The syndrome of radiation sickness
due to whole-body irradiation. Although the
therapeutic uses of radiation had long since
laid the groundwork for an appreciation of the
signs and symptoms of "radiation sickness," it
remained for the observations of the Joint Com-
mission to provide the definitive description of
this entity. The Endings, of course, vary accord-
ing to the radiation dose. We are not here con-
cerned with the early effects of lethal doses of
whole-body irradiation, since persons receiving
such doses can scarcely provide the parentage
for a study of this nature. The Joint Commis-
sion observed that individuals receiving rela-
tively large but yet sublethal doses of irradiation
(as judged by proximity to the hypocenter in
the absence of marked shielding) may or may
not develop nausea and vomiting within a few
hours of their exposure. There follows a rela-
lively asymptomatic period of approximately
two weeks, after which characteristic signs and
symptoms appear. Some of these, such as fever,
malaise, anorexia, nausea, and vomiting, have
a low degree of specificity, being present in a
wide variety of diseases. Other findings were
much more specific. The chief among these are
summarized in Table 4.1. These are figures for
all survivors, irrespective of the amount of
shielding which protected them. Let us restrict
ourselves, for the moment, to a consideration
of the findings in persons reporting themselves
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Representative terms from entire chapter:
joint commission
The Criteria of Radiation; Employed in the Study 35
it:
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36 Genetic Effects of Atomic Bombs Chapter IV
within 1,000 meters of the hypocenter. From
the standpoint of distinctiveness, two symptoms
epilation and purpura are outstanding.
Oropharyogeal lesions also were frequently en-
countered. Diarrhea, while reported by large
numbers of persons, could, at 20 days after the
bombing, in any individual case be as well at-
tributed to the poor hygienic conditions follow-
ing the bombing as to the bomb itself, and does
not seem to be a satisfactory symptom on which
to base a study. Bloody diarrhea is a somewhat
more reliable symptom, but still, from the find-
ings of the Joint Commission, less useful than
the other three symptoms already discussed.
Further evidence as to the relative validity of
the findings listed in Table 4.1 as indicators of
radiation exposure comes from an analysis of the
manner in which the various findings tended to
be associated. Epilation and petechiae were more
highly associated than any other pair of symp-
toms in both cities. The next highest associations
observed were, in both cities, epilation with
oropharyugeal lesions, and petechiae with
oropharyngeal lesions.
On the basis of these findings, it was felt
that the appearance of epilation, petechiae, or
oropharyngeal lesions, singly or in combination,
within three months of the bombing, provided
a relatively specific and objective yardstick of
the absorption of a certain amount of radiation,
such as could be employed in the present study
(see also, inter alla, Warren and Bowers, 1950;
Los Alamos Scientific Laboratory, 1950; vor der
Bruegge, 1952; Hempelmann, Lisco, and Hoff-
man, 1952~. Although exact data are lacking,
it seems likely, on the basis of animal data, that
there is considerable individual variation in
susceptibility to these symptoms, a point which
must of course be borne in mind when we come
later to the problem of estimating radiation
dosages. It will be noted that there are signi6-
cant differences between Hiroshima and Naga-
saki in the percentages of persons exhibiting
certain symptoms subsequent to exposure within
1,500 meters of the hypocenter. These dider-
ences are customarily attributed primarily to
local differences in shielding factors (see be-
low), but may also be due in part to actual
dose differences.
4.3.2 The relation between; distance from
the hypocer~ter arid radiation; dosage. A1-
though the intensity of radiation obviously must
decrease with distance from the hypocenter, the
exact form of the distance-dosage relationship
in Hiroshima and Nagasaki remains to this day
uncertain. In part this is due to inadequate in-
formation concerning certain physical properties
of these atomic explosions, in part to lack of
detailed information concerning atmospheric
moisture content at the time of the explosion.
Furthermore, there is the possibility that the
distance-dosage relationship is not the same in
all radii from the hypocenter. Be this as it may,
at the time this study was planned it was clear
from such data as are given in Table 4.1, con-
cerning the relationship between the occurrence
of certain of the symptoms described above and
distance from the hypocenter, that it would be
important to record position at the time of the
bombing as accurately as possible.
4.3.3 The role of shielding ire de~erm~r~ing
radiation dose. The third type of information
thought to be especially valuable in estimating
radiation dosage concerned the amount of
shielding protecting the individual from the
eRects of the explosion. Table 4.2 illustrates
some of the findings of the Joint Commission
in this respect. For the sake of brevity, only
the Hiroshima data are reproduced; the findings
in Nagasaki were essentially similar. An obvious
question which had to be disposed of early in
the design of the program concerned the elabo-
rateness of the shielding data to be collected.
Obtaining a complete shielding history can be
quite time consuming. Theoretically, knowing
the distance-dosage relationship and the precise
shielding, one can arrive at a relatively accurate
estimate of the amount of irradiation received
by an individual. We have already mentioned
the uncertainties surrounding the distance-
dosage relationship. These uncertainties are par-
ticularly acute as regards the neutron component
of the radiation spectrum, a component which
in animal experiments has been shown to have
a high relative biological effectiveness with re-
spect to genetic effects. Furthermore, in the
authors' opinion there is no realistic approach
to the problem of radiation scatter and second-
ary radiation as a factor in the exact dosage re-
ceived by any individual. Finally, there is room
for reasonable doubt as to most individuals'
abilities to reconstruct their exact positions at
the time of so traumatic an event as this, and
yet nothing less than such a reconstruction will
suffice for a precise evaluation of shielding.
With all these considerations in mind, it was
The Criteria of Radiation Employed ir; the Study 37
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38
concluded that while the experience of the Joint
Commission left no doubt as to the desirability
of collecting shielding data, this should be sim-
ple in nature.
4.4 The type of radiation aorta collected ire
this study. In addition to the biological con-
siderations which we have just discussed, certain
Ger~eiic Ejects of Atomic Bombs Chapter IV
Finally, since the history taking was to extend
over an indefinite number of years, much was
to be said for concentrating on certain salient
features of the individual's experience, which
could be as readily recalled relatively late as
relatively early.
With all these considerations in mind, the
TABLE 4.3 DISTRIBUTION BY DISTANCE AND SHIELDING OF HUSBANDS OF WIVES REGISTERING
PREGNANCIES WITH THE GENETICS PROGRAM (HIROSHIMA)
(For a definition of the classes see Sec. 4.5.)
Distance
( hundreds
of meters)
In open
00-04 1
05-09 IS
10-14 53
15-19 44
20-24 29
25-29 11
30--
No. persons
symptomatic p a G a E a PG PE GE PGE
1 6 1
4 3 22
5 6 23 2
4 6 12 1
4 - 4
1 7 5
No.
persons
asymp
tomatic
- 1 2
2 5 12
3 9 12 102
3 3 2 287
2 4 - - 409
1 2 ~213
2 2 868
Total no.
Total no. symptoms
persons experl
exposed enced Ratio
(a) (b) (b/a)
27
155
331
438
224
885
1,893 2,063
28 1.04
89 .57
56 .17
36 .08
14 .06
21 .02
In Japanese building
00 - 04 2 ~21 3 6 -
05-09 39 1 1 8 4 9 1613 52 84 1.62
10-14 127 11 8 29 10 16 14 39387 514 245 .48
15-19 54 20 11 10 3 4 4 2695 749 69 .09
20-24 27 9 6 5 - 2 3 2634 661 36 .05
25-29 11 2 1 2 1 2 2 1444 455 18 .04
30~- 24 5 3 10 - 1 4 11,636 1,660 31 .02
3,810 4,094
In other shelter
00 - 04 - ~2 2
05-09 14 2 5 1 3 3 17 31 24 .77
10-14 17 6 4 1 1 1 2 2 33 50 25 .50
15-19 6 1 3 - 2 - 61 67 8 .12
20-24 2 1 1 - - 46 48 2 .04
25-29 2 1 - 1 51 53 4 .08
301 2 1 - 1 - - 200 202 2 .01
, ............
a p _ Petechiae; G = Gingivitis; E = Epilation.
"practical" considerations entered into the de-
termination of the type of data to be collected.
The histories were to be obtained by clerks with
the equivalent of a high school education. These
clerks, although they could be carefully drilled
in their duties, could not be expected to exercise
a great deal of judgment if the approach to the
problem involved the compilation of an elabo-
rate history. It could be anticipated that the
turn-over among clerks would be rather high.
4~0 453
following information was obtained concerning
each pregnant woman and her spouse included
in this study:
1. Presence in Hiroshima or Nagasaki at the
time of the bombing.
2. Location in city at time of bombing.
3. Distance from the hypocenter [calculated
from (2 ) ].
4. Indoors or outdoors.
5. Type of building.
The Criteria of Radiation; Employed in the Study 39
6. Occurrence of subcutaneous bleeding (pe
techiae) .
7. Occurrence of gingivitis.
8. Occurrence of bloody diarrhea.
9. Occurrence of epilation (partial or com
plete) .
10. Occurrence of burns.
11. Occurrence of external injuries.
Of calculation, meters are rounded to decameters,
and decameters further rounded to hectometers,
so that the coded interval in hectometers de-
notes (x-55) to (x+44) meters.
Items 4 and 5 on the above list represent an
attempt, however rough, to accumulate certain
data relative to the evaluation of shielding.
Item 4 was to be answered simply as indoors or
TABLE 4.4 DISTRIBUTION BY DISTANCE AND SHIE! DING OF WIVES REG~TERING ~EGNANCIES WITH THE
GENETICS PROGRAM ~ HIROSHIMA
Distance
(hundreds
of meters)
In open
00-04
05-09 14
10-14 75
15-19 85
20-24 53
25-29 18
30+ 24
9
10
7
2
No. persons
symptomatic p a G a E a PG PE GE PGE
4
24
50
26
4
11 - 1
1 6 3
1 8 13 18
3 4 3 6
1 - 8 5
2 2
4 -
No. Total no.
persons persons
asymp- exposed
somatic (a)
8
156
489
560
311
1,020
22
231
574
613
329
1,044
2,545 2,814
Total no.
symptoms
experi
enced, Ratio
(b) (b/a)
27 1.23
133 .58
107 .19
72 .12
24 .07
29 .03
In Japanese building
00-04 2 - - 2 1 36
05-09 52 1 1 7 2 15 6 20 23 75115 1.53
10-14 254 41 17 66 8 38 23 61 881 1,135 445 .39
15-19 116 36 24 36 1 8 4 7 1,668 1,784 143 .08
20-24 65 18 13 22 1 6 1 4 1,398 1,463 81 .06
25-29 28 13 4 6 2 2 1 - 1,205 1,233 33 .03
300 31 9 11 8 - 2 1 3,369 3,400 34 .01
8,545 9,093
In other shelter
00-04 3 1 - - 2 3 5
05-09 35 3 5 1 8 6 12 75110 74 .67
10-14 13 3 2 1 2 1 2 2 102115 22 .19
15-19 11 3 - 6 1 1 181192 13 .07
20-24 8 5 1 2 - 117125 8 .06
25-29 1 1 - - - 148149 1 .01
300 3 1 1 1 188191 4 .02
a p-Petechiae; G _ Gingivitis; E = Epilation.
In locating the position of an individual at
the time of the bombing an effort was made to
pinpoint position as accurately as possible. The
distance from the hypocenter was then deter-
mined by actual measurement on a large-scale
map of the city. The method of measurement
has varied from time to time, involving vari-
ously the use of plastic and metal tapes, co-
ordinates, and concentric circles. In the process
sii ~85
outdoors. Item 5 pursued the point somewhat
further, admitting of ten alternatives, namely,
if indoors, then
1. Inside concrete building,
2. Inside brick building,
3. Inside wooden Japanese or other type build
~ng,
4. Inside cave or "bunker,"
40
and if outdoors, then
5. In open,
6. Behind (within two meters) wall,
7. In trench,
8. Behind post or tree,
9. In tram, train, or car, and
10. Under eaves of house (i.e., shielded by
house) .
Genetic Effects of Atomic Bombs Chapter IV
In the original design of the study, no symp-
tom among those listed was to be recognized
unless it developed prior to December 15, 1945.
Some instances have come to light where the
alleged onset of symptoms after that date have
been recorded. This cannot be attributed to
exposure to the bomb. There is a good reason to
believe that the erroneous inclusion of such re
TABLE 4.5 DISTRIBUTION BY DISTANCE AND SHIELDING OF HUSBANDS OF WIVES REGISTERING
PREGNANCIES WITH THE GENETICS PROGRAM (NAGASAKI)
Distance
(hundreds
of meters)
In open
00-04....
05-09. ·
10-14 20
15-19 11
20-24 4
25-29 7
30+ 8
NO. persons
symptomatic p n G a E a PG PE GE PGE
No. Total no.
persons persons
asymp- exposed
somatic (a)
1 1
611
5171
7283
9498
165172
1,1511,159
1,5401,595
Total no.
symptoms
experi
enced Ratio
(b) (b/a)
9 .82
27 .38
17 .20
4 .04
7 .04
10 .01
In Japanese building
00 - 04 - - - - -11 -
05-09 6 - 1 1 2 21016 13 .81
10-14 45 6 6 9 3 7 2 12186231 81 .35
15-19 23 2 5 9 1 2 2 2216239 32 .13
20-24 2 2 -220222 2 .01
25-29 2 1 - 1 - - - 387 389 2 .005
30+ 11 4 2 3 2 - 2,714 2,725 13 .005
3,734 3,823
In other shelter
00-0411 - -
05-09 10 1 1 3 2 - 3 34 44 18 .41
10-14 43 5 4 10 5 4 6 9 188 231 76 .33
15-19 14 3 4 1 2 1 3 171 185 24 .13
20-24 2 - 1 1 103 105 2 .02
25-29 2 - 1 - 1 - 101 103 3 .03
30+ 4 2 1 1 - - 1,560 1,564 4 .003
a p = Petechiae; G = Gingivitis; E = Epilation.
Items 649, bearing on radiation sickness, were
to be answered simply as "yes" or "no," after
a brief explanation of the symptom by the clerk,
if necessary. Limiting answers to "yes" or "no"
obviously required the clerk to exercise her
judgment in some cases. For the more vague
term "oropharyngeal lesions" we have substi-
tuted gingivitis, since a necrotic-type of gingivi-
tis with gingival bleeding was one of the more
prominent and specific of the oropharyngeal
lesions.
2,158 2,233
ports of "delayed effects" occurred very rarely.
Items 10 and 11 were induded as one of
several approaches to the problem of disen-
tangling the possible radiation effects of the
bombs from other effects and also the general
disaster effect. Thus, it was anticipated that in
the event of a positive correlation between some
aspect of pregnancy termination and radiation
history, an attempt could be made to determine
if the correlation still held up after the elimina
The Criteria of Radiation Employed ir; the Study 41
tion of those recording burns or external in-
juries of any type.
Those familiar with the problem of evaluat-
ing radiation exposure will be quick to recognize
the very simple nature of the data collected in
this study. The adequacy of these data as a
basis for quantitative estimates of irradiation
has been the subject of considerable discussion.
4.6 summarize the findings of the present study
as regards the relationship between certain types
of shielding, certain symptoms, and distance
from the hypocenter. Based on items of the
questionnaire (see preceding section), two de-
grees of shielding have been recognized, namely,
that provided by being inside a Japanese-type
home at the time of the explosion, and that
TABLE 4.6 DISTRIBUTION BY DISTANCE AND SHIET DING OF WIVES REGISTERING PREGNANCIES WITH THE
GENETICS PROGRAM ~ NAGASAKI )
Distance
~ hundreds
of meters)
In open
00-04
05-09 5
10-14 24
15-19 18
20-24
25-29
30+
No.
persons
No. persons asymp
symptomatic pa Ga Ea PG PE GE PGE somatic
.. 9 1 1
.. 10 2 3
2
2 7
2 9
5
5
4
1 2
2
2
2 1
3 6
1 2
2
1
Total no.
persons
exposed
(a)
7 12
60 84
108 126
173 180
274 283
1,674 1,684
2,297 2,369
Total no.
symptoms
experi
enced Ratio
(b) (b/a)
9 .75
42 .50
25 .20
9 .05
11 .04
11 .01
In Japanese building
0~04
05-09 4 - 1 1 27119 .82
10-14 129 11 7 35 7 15 22 32292421237 .56
15-19 55 12 6 19 1 6 6 545951478 .15
20-24 26 5 9 9 1 1 1 84286829 .03
25-29 6 2 3 - 1 1,1061,1127 .006
30+ 19 7 5 6 1 7,1627,18120 .003
9,86810,107
In other shelter
00-04 - 5_
05_09 19 1 2 9 1 1 4 17493 27 .29
10-14 56 3 6 24 4 5 7 7185241 86 .36
15-19 25 6 1 11 - - 1 6109134 38 .28
20-24 9 2 3 3 1145154 11 .07
25-29 5 1 2 1 - 1 - 154 159 6 .04
30+ 7 1 3 2 1 - - - 2,005 2,012 8 .004
a p Petechiae; G = Gingivitis; E = Epilation.
Specifically, the possible desirability of a much
more elaborate history was repeatedly discussed.
It is our contention, admittedly subjective but
documented in part by the internal consistency
of the data presented in the following sections,
the recall factor in these situations being what
it is, and in view of the radiation variables, that
this represents the most practical approach to
this problem which could be adopted.
4.5 The relation between distance, shielding,
and symptoms ire these data.- Tables 4.3 to
2,677 2,793
provided by being inside any other type of
structure concrete or brick building, cave or
bunker-type air raid shelter. Figures 4.1 and 4.2
present these same findings in graphic form.
For ease of presentation, a "symptom ratio"
has been used, consisting of the total number
of symptoms depilation, petechiae, or gingivi-
tis) recorded by the survivors at a particular dis-
tance, divided by the number of survivors giving
information. Data are not plotted for the 00-04
distances because of the few individuals in
42
Genetic Ejects of Atomic Bombs Chapter IV
valved. Several important conclusions emerge 3,000 meters may also be somewhat "diluted"
from a consideration of these data:
4.5.1 For all three groups, the symptom
ratio falls off rapidly with distance. In the light
of these findings, as well as the distance-dosage
relationship estimated on physical grounds (see
''41
al
·.o .
.~. .
SYMPTOM
RATIO
;
.6- ~
,4e .
.2- .
by false reporting.
4.5.2 There is evidence that shielding in
"other style" buildings substantially reduced
the proportion of persons with symptoms at
distances within 1,500 meters.
LEGEND
IN OPEN
-- IN JAPANESE-STYLE BUlLDINC
_ ___ IN OtHER-STYLE BUILDING
\
20
DISTANCE IN 100 S Of METERS
FIGURE 4.1 Symptom ratio in relation to distance from hypocenter for Hiroshima (husbands and wives
combined). Explanation in text.
below), it seems unlikely that there was signifi-
cant radiation beyond 3,000 meters from the
hypocenter. The few individuals reporting epila-
tion, petechiae, and/or gingivitis beyond that
distance are, with possible rare exceptions, al-
most certainly in error in attributing their
symptoms to irradiation. Taking this i-2 per
cent as a baseline for "false reporting," it
follows that the symptomatic 'group within
4.5.3 In what appears at first sight to be
a paradox, in the 500-900 meter ring a sub-
stantially higher proportion of persons in Japa-
nese homes developed symptoms than did
persons in the open. The reason for this seems
clear. At this distance, persons reporting them-
selves in the open must actually have been
shielded by one or more buildings from the
bomb burst, otherwise they almost certainly
The Criteria of Radiation Employed ire the Study
43
would have sustained fatal burns. The biologi- and the consequent variation in the angle of
cat evidence suggests that the total average incidence of the radiation. However, for radia
shielding of such persons actually exceeded that lion incident at right angles, the average tile
of persons in Japanese homes. roof has an absorptive value in the neighbor
4.5.4 In the 1,000-1,900 meter ring, there hood of 45 mm. of aluminum. Beyond 1,000
is a suggestion that in Hiroshima, although not
so clearly in Nagasaki, presence in a Japanese
style home conferred some protection against
the development of symptoms, the basis for
comparison being persons reporting themselves
..o
.8
SYMPTOM
RATIO
.4
.2
meters, persons in Japanese-type buildings in
Hiroshima at the time of the explosion probably
averaged several such walls or roofs between
themselves and the exploding bomb. This is a
significant degree of shielding. In very round
LEGEND
to
IN OPEN
\ ~- IN JAPANESE - STYLE BUILDING
IN OTHER- STYLE BUILDING
' \
a\
:
~\
"",`~W
, _ ~_
. ~.
20 25 30
DISTANCE IN 100 S OF METERS
FIGURE 4.2- Symptom ratio in relation to distance from hypocenter for Nagasaki (husbands and wives
combined). Explanation in text.
"outdoors." The average amount of shielding
by which a person "in the open" was protected
is very difficult to estimate. It is somewhat
easier to quantitate the shielding of the persons
in Japanese-style buildings. Woodbury (1953
and unpublished) reports that X-ray photo-
graphs taken at 62-kv indicate that the absorp-
tion of the bamboo-lattice and mud walls of
the average Japanese house is equal to about
33 mm. of aluminum in the densest portion, and
15 mm. in the lightest. The absorptive value
of the tile roofs which are standard construction
in Japanese houses is undoubtedly more variable,
depending on the distance from the hypocenter
terms, such shielding would screen out in the
neighborhood of 50 per cent of the dosage at
a level of lOOr of the high-energy X-ray and
gamma radiation released by the bomb.
It seems worth pointing out that the amount
of shielding implied in the statement, "in a
Japanese-style home," varies directly with dis-
tance from hypocenter, since at greater distances,
because of the angle of incidence of the radia-
tion, more walls and roofs would usually inter-
vene between the source of radiation than at
lesser distances. Persons in Nagasaki in Japanese
homes at the time of the explosion on the
average were probably less shielded than in
44
Hiroshima, because of the difference in terrain
and the extension of homes up the sides of the
valley.
4.6 Factors contributing to the validity of the
radiation; histories. The value of several dif-
ferent persons obtaining a history from a given
individual is well known in clinical medicine.
The changes in emphasis and the new material
introduced, as the patient passes from one inter-
viewer to the next, are sometimes remarkable.
From the standpoint of verifying information,
the Genetics Program has been fortunate for the
following reasons:
4.6.1 Over the 6-year span covered by this
program, many women registered two or more
times (cf. Sec. 5.6~. At each registration, a
history was obtained without reference to any
previous history.
4.6.2 In 1950 a Radiation Census was
carried out in both Hiroshima and Nagasaki.
This census obtained brief data on each survivor
of the bombings then living in Hiroshima and
Nagasaki, induding position at the time of the
bombing.
4.6.3 Some of the parents falling within
the scope of the Genetics Program-especially
the more heavily irradiated also came under
scrutiny in connection with other special studies
of the ABCC, such as the Adult Medical Pro-
gram, the Ophthalmology Program, etc. Each
of these latter programs obtained a very detailed
radiation history.
All of the information available on any given
person was correlated through a Master File.
Particular attention was directed towards a
comparison of the radiation histories obtained
from a given person on different occasions. In
the event of a discrepancy, an effort was made
to query the individual concerned, in an attempt
to resolve it. On the basis of the information
obtained on the query, a single uniform entry
was made on all the forms involved. As might
be expected, changes on the Genetics Short
Form were not infrequent, although the data
have not been kept in such a fashion as to per-
mit a precise analysis. However, it is our im-
pression that important changes were not
common.
4.7 Definition of radiation categories. We
are now in a position to define certain "radiation
categories" which will be basic to the analysis
which follows. This is done in Table 4.7.
"Heavy" shielding denotes presence in concrete
or brick building or air raid shelter at the time
Genetic Effects of Atomic Bombs Chapter IV
of the explosion. "Moderate" shielding includes
being within a street car, train, or car, behind
a wall or under the eaves of a house, i.e., on
the side of the house away from the hypocenter.
Finally, "light" shielding includes those giving
their location as in a Japanese-style building or
in a trench or behind a post or tree. Trench-type
shielding is classified as "light" because of the
difficulty in establishing how well an individual
was protected by a trench.
TABLE 4.7 THE DEFINITION OF EXPOSURE
CATEGORIES TO BE EMPLOYED IN
THIS ANALYSIS
Groups
Urlexposed
Over 3,000 meters, with
or without alleged
symptoms -
2,000-2,900 meters
Heavy shielding
Moderate shielding
Light shielding
No shielding -
1,500-1,900 meters
Heavy shielding -
Moderate shielding -
Light shielding -
No shielding -
1,000-1,400 meters
Heavy shielding +
Moderate shielding -
Light shielding -
No shielding -
Under 1,000 meters
Heavy shielding
Moderate shielding -
Light shielding -
No shielding -
Symptoms depilation, pete
chiae, gingivitis), un
der 3,000 meters -
+
+
+
+
+
+
+
+
+
+
Inspection of Table 4.7 in the light of the
preceding discussion suggests that this is a some-
what "conservative" classification, in terms of
correction for shielding. Thus, individuals re-
porting "heavy" shielding but asymptomatic
have all been relegated to group 2, despite the
fact that the symptom ratio in heavily shielded
persons within 1,000 meters is approximately
0.7. Since relatively few persons were "heavily"
shielded (see below), the net effect of this will
be to increase slightly the average radiation
dosage of group 2. On the other hand, this re-
moves from categories 3 and 4, which received
intermediate amounts of radiation, a group of
The Criteria of Radiation Employed in the Study 45
individuals whose average radiation dose would
be extremely difficult to evaluate.
The distribution of all the parents of regis-
tered terminations included in this study in
terms of their radiation category is given in
Table 4.8. Approximately 78.3 per cent of all
the fathers who were registered, and 57.0 per
cent of all the mothers, were not in the cities
at all at the time of the explosion. Of those
present in the cities, a substantial majority was
beyond 3,000 meters from the hypocenter. Only
1.2 per cent of fathers, and 2.4 per cent of
mothers, reported symptoms characteristic of
radiation sickness.
In a preliminary report on this study (Neel
et al., 1953), a system of radiation categories
was employed which failed to take into account
shielding. Thus, in this treatment group 4 was
defined simply as: "In one of the two cities,
categories 1 and 5, any estimate is at best an
exceedingly rough approximation. For categories
2, 3, and 4, we will do well if we establish the
range within which the true average is likely
to be found. A particular difficulty in estimating
radiation dosage, already alluded to, is the fact
that a wide spectrum of radiant energy is in-
volved, with the consequent complications in
expressing tissue dosage in simple terms, a
difficulty only partially circumvented by ex-
pressing dosage in terms of the "roentgen
equivalent physical" (`rep) unit. This latter may
be defined as that amount of any ionizing radia-
tion (beta rays, neutrons, etc.) which dissipates
the same amount of energy per gram of water
as one roentgen of X-rays or gamma rays. All
estimates refer to surface dose. The actual
amount of irradiation delivered to the gonad
will be less, although because of the high energy
TABLE 4.8 DISTRIBUTION OF REGISTERED BIRTHS BY PARENTAL EXPOSURE
Hiroshima Nagasaki
~ ~ , -
Mother's exposure Mother's exposure
, ,
123 45Total 1234 5Total
r1 18,723 5,721 2,320 417 791 27,97216,338 10,141 823 116 48027,898
^= it' 12 1,611 1,993 451 90 127 4,2722,420 4,483 298 38 917,330
o. 1 3 648 416 545 49 67 1,725258 301 109 14 21703
4 147 119 81 28 26 40142 55 14 5 1117
5 275 145 80 19 54 573107 133 25 3 21289
Total 21,404 8,394 3,477 603 1,065 34,94319,165 15,113 1,269 176 614 36,337
and less than 1,845 meters from the hypocenter,
but asymptomatic. Most of these individuals
were shielded to a greater or lesser extent from
the full effects of the bombs." In this prelimi-
nary treatment, for some purposes the offspring
of parents both of whom were group 4 or 5
were considered. In the case of the malformation
analysis, for example, there were available 596
infants born to parents meeting these restric-
tions. But with the radiation categories which
have just been defined, there are in the mal-
formation analysis (Table 8.4) only 145 in-
fants born to parents both in categories 4 or 5.
The difference in numbers is due almost entirely
to the attempt to correct for shielding.
4.fS Consideratior;s in the estimation of the
average amount of radiation received by persor;s
in each of lye five radiation; categories. We
come now to an attempt to estimate the average
amount of radiation represented by each of the
five radiation categories. It should at once be
made clear that with the possible exceptions of
content of atomic bomb irradiation, the gonad
dose will actually be rather close to the skin
dose.
Category 1 individuals, outside the cities at
the time of the bombing, of course have received
no radiation from the atomic bomb (ignoring,
of course, the possibility of residual radiation).
Category 5 individuals, symptomatic and within
3,000 meters, are considered to have received
as a minimum the equivalent of 200 roentgens
of gamma rays (Los Alamos Scientific Labora-
tory, 1950~. The maximum dose received by a
category 5 individual is in the neighborhood of
the equivalent of 600 roentgens of gamma rays.
The latter figure is based on the premise that
the LD50 in man for whole-body radiation is
about 400 roentgens of gamma rays, but that a
few individuals may survive doses amounting to
600r of gamma rays (lIempelmann, Lisco, and
Hoffman, 1952~. The average dose received by
category 5 individuals can probably be placed
at the equivalent of 300-400 roentgens of
46 Genetic Ejects of Atomic Bombs Chapter IV
gamma rays. We will return shortly to the im-
portant question of the magnitude of the neu-
tron component of this estimated dosage. Suffice
it to say at this point that category 5 persons as
a group received a relatively larger amount of
neutron radiation than any other group, and
because of the relatively greater biological ef-
fectiveness of neutrons as contrasted to gamma
rays, generally speaking, the dose in rep units
received by category 5 persons may be substan-
tially below the dose as expressed in roentgens.
104
105
1O
O 1500 3000 4500 6000 7500 · 9000
DISTANC E FROM EX PLOSION (tt.)
FIGURE 4.3 Total dosage of initial gamma
radiation as a function of distance from the hypo-
center of the explosion of a "nominal" atomic bomb,
from "The Effects of Atomic Weapons."
In arriving at our estimate of the amount of
radiation received by category 2, 3, and 4 indi-
viduals, three considerations are outstanding:
4.f8.1 The estimated dlistar~ce-dosage carve.
Figures 4.3 and 4.4 are the distance-dosage
curves in terms of neutron and gamma radiation
for the explosion of a "nominal" atomic bomb,
roughly comparable to what was detonated over
Hiroshima and Nagasaki, as published in "The
Effects of Atomic Weapons." In the absence of
other unclassified data, this must of necessity
serve as the only guide available. Note that the
abscissa in both figures is scaled in terms of feet
rather than the meted in which we have ex
pressed distance. Figure 4.3, if taken at face
value, indicates that beyond approximately 1,600
meters the amount of gamma radiation received
was less than 100r. Our own observations, in-
volving the reported appearance of symptoms
in, e.g., significant numbers of persons in the
2,000-2,400 meter ring, lead us to feel this
estimate is somewhat conservative. Also, un-
published calculations of Wilson (1951) sug-
gest that, at least for Hiroshima, the neutron
curve given in Figure 4.4 is on the conservative
poop ,_ ___ _ _ = 1 1
~ ~ =
~__r_ V _:rr ~S-- _
~10 = ~-FA AT N' :UTR ~N5 \~ =__ _
0~ ___ _ r_ r_r~___
== =
_ _ _ = - _
1500 IB00 2100 2400 2700 3000
DISTANCE FROM EXPLOSION (at.}
FIGURE 4.4- Fast and slow neutrons delivered
per square centimeter as a function of distance from
the hypocenter of the explosion of a "nominal"
atomic bomb, from "The Effects of Atomic Weap-
ons."
side. On the other hand, both from these two
curves and on the basis of our own observations
regarding the shape of the distance-dosage cube,
it seems likely that persons at distances in excess
of 3,000 meters received little if any radiation.
4.68.2 The observations of the Joint Com-
mission regarding le~copenia. One of the
well recognized effects of whole-body irradiation
in amounts compatible with survival is a tem-
porary leucopenia. Information concerning the
proportion of individuals in the radiation cate-
gories defined above who developed leucopenia
following their exposure would therefore be of
value in any attempt to estimate radiation
The Criteria of Radiation
dosage. Certain of the published observations of
the Joint Commission are quite useful in this
respect. The more pertinent portion of their
published data is summarized in Table 4.9 (see
also LeRoy, 1950~. Leucopenia is here defined
as a total leucocyte count per mm.3 of less than
3,000 at some time during the second through
the fifth weeks following the bombing. Some
of the individuals on whom the percent-
ages in Table 4.9 are based had repeated
leucocyte determinations during a hospitaliza-
tion, others had but a single count, at any time
TABLE 4.9 THE FINDINGS OF THE JOINT COMMIS-
SION IN HIROSHIMA WITH REGARD TO THE OC-
CURRENCE OF EPILATION, PETECHIAE, AND LEU-
COPENIA IN PERSONS FALLING INTO VARIOUS
EXPOSURE CATEGORIES
Epilation
No. examined ..
No. epilated ...
% epilated .....
Petechiae
No. examined ..
No. with pete-
chiae .......
% with petechiae.
Leucopenia
No. examined ..
No with leucope-
nla ..........
NO with leucope-
nia ..........
(Further explanation in text. ~
Exposure category
AB C D
5701,119 1,817
434400 172
76.135.7 9.5
5701,119
1,817
310262
54.423.4 5.9
195211
146121
08
156
31
74.9 57.3 19.9
between the second and fifth weeks.
figures are thus at best estimates of the per-
centage which on careful studies would be
found to develop leucopenia. The exposure cate-
gories utilized by the Joint Commission and
reproduced in Table 4.9 are somewhat different
from our own, the four most severe, the ones
with which we are concerned, being defined as
shown in Table 4.10.
It will be noted that the figures regarding
leucopenia are based on fewer individuals than
those with respect to epilation and petechiae.
This is understandable in view of the difficulties
in obtaining leucocyte determinations imposed
by the conditions prevailing following the
bombing. As the Commission report points out,
these figures must be accepted with some reser-
vations in view of the unfavorable circumstances
under which they were obtained; on the other
Employed ir' the Study 47
hand, the manner in which the findings regard-
ing leucopenia parallel those on petechiae and
epilation gives indirect confirmation of their
validity. Since the Commission worked with a
selected sample, composed largely of injured
and, in the majority of cases, hospitalized sur-
vivors, caution must be exercised in extrapolat-
ing to our own, total sample. It will be noted,
however, that with the exception of exposure
category A, more of the persons examined de
TABLE 4.10 THE EXPOSURE CATEGORIES DEFINED
BY THE JOINT COMMISSION, TO BE APPLIED
TO THE INTERPRETATION OF TAB! E 4.9
Exposure group
Description A B C D E F
0-1,000 meters
Outdoors or in Japanese
buildings + -
In heavy buildings.... - +
In bomb shelters -
1,100-1,500 meters
Outdoors or in Japanese
1,604 buildings + -
74 In heavy buildings _
4.6 In bomb shelters -
1,60~2,000 meters
1,604 Outdoors or in Japanese
buildings - +
31 In heavy buildings -
1 9 In bomb shelters
2,100-2,500 meters
111 Outdoors or in Japanese
buildings - - +
10 In heavy buildings -
In bomb shelters
9 0 2,600-3,000 meters
Outdoors or in Japanese
buildings - - - +
The In heavy buildings -
In bomb shelters......
_ + _
+
veloped leucopenia than either epilation or
petechiae.
Through the courtesy of The Armed Forces
Institute of Pathology, it has been possible to
obtain certain very useful additional tabulations
of the material collected by the Joint Commis-
sion. Among exposed Japanese in Hiroshima
who received one or more leucocyte determina-
tions sometime between the second and four-
teenth weeks, who failed to develop epilation,
petechiae, or gingivitis, and who are riot known
to have died within the fourteen' weeks follow-
ing the bombings, the distribution of lowest
observed leucocyte counts by distance is as shown
in Table 4.11. More intensive studies would
have shown a higher proportion with leucopenia.
48
Genetic Effects of Atomic Bombs Chapter IV
TABLE 4.11 THE DISTRIBUTION OF LEUCOCYTE VALUES IN [ITROSHIMA JAPANESE WHO FAILED TO
DEVELOP EPILATION, PETECHIAE, OR GINGIVITIS FOLLOWING THE BOMBING, IN RE
LATION TO DISTANCE FROM HYPOCENTER AND TYPE OF SHIELDING
(Data of Joint Commission, as tabulated by the Armed Forces Institute of Pathology)
Distance from hypocenter less than 1,500 meters
Indoors, heavy bldg.
Outdoors, unshielded Outdoors, shielded Indoors,Jap.bldg. shelter
LeUCOCYteS/mm.3 NO. Cum. DO NO. CUm. % NO. Cum. % NO. CUm. NO
0- 500 1 1.4 O O O O O O
600-1,000 1 2.9 1 2.7 1 .5 O O
1,100-1,500 1 4.3 1 5.4 2 1.6 1 1.0
1,600-2,000 O 4.3 1 8.1 6 4.9 3 4.1
2,100-2,500 1 5.7 2 13.5 6 8.2 1 5.2
2,600-3,000 1 7.1 1 16.2 9 13.0 1 6.2
3,100-3,500 3 11.4 1 18.9 16 21.7 3 9.3
3,600-4,000 5 18.6 2 24.3 22 33.7 7 16.5
4,100-4,500 7 28.6 6 40.5 11 39.7 O 16.5
4,600-5,000 5 35.7 3 48.6 14 47.3 1 17.5
5,100-5,500 3 40.0 3 56.8 16 56.0 18 36.1
5,600-6,000 6 48.6 9 81.1 9 60.9 7 43.3
6,100-6,500 8 60.0 3 89.2 16 69.6 11 54.6
6,600-7,000 7 70.0 O 89.2 15 77.7 8 62.9
7,100-7,500 2 72.9 O 89.2 8 82.1 4 67.0
7,600-8,000 4 78.6 2 94.6 7 85.9 8 75.3
8,100-8,500 2 81.4 O 94.6 9 90.8 3 78.4
8,600-9,000 5 88.6 1 97.3 3 92.4 7 85.6
9,100-9,500 1 90.0 1 100.0 2 93.5 2 87.6
9,600- ......... 7 100.0 O 100.0 12 100.0 12 100.0
70 37 184
Distance from hypocenter 1,600-2,000 meters
Indoors, heavy bldg.
Outdoors unshielded Outdoors shielded Indoors,Jap.bldg. shelter
. ~
Leucocytes/mm.3 No. Cum.% No. Cum. To No. Cum. To NO. CUm. %
0- 500 O O O O 1 .4 O O
600-1,000 O O O O O .4 O O
1,100-1,500 3 1.1 1 1.7 O .4 1 1.9
1,600-2,000 1 1.5 O 1.7 2 1.1 O 1.9
2,100-2,500 3 2.6 O 1.7 5 3.0 1 3.7
2,600-3,000 5 4.5 1 3.4 4 4.5 O 3.7
3,100-3,500 11 8.6 4 10.2 10 8.2 1 5.6
3,600-4,000 16 14.7 2 13.6 16 14.1 2 9.3
4,100-4,500 17 21.1 6 23.7 26 23.8 6 20.4
4,600-5,000 10 24.8 1 25.4 17 30.1 1 22.2
5,100-5,500 30 36.1 8 39.0 23 38.7 6 33.3
5,600-6,000 18 42.9 11 57.6 27 48.7 8 48.1
6,100-6,500 22 51.1 5 66.1 17 55.0 4 55.6
6,600-7,000 26 60.9 2 69.5 27 65.1 2 59.3
7,100-7,500 14 66.2 3 74.6 21 72.9 3 64.8
7,600-8,000 21 74.1 3 79.7 14 78.1 3 70.4
8,100-8,500 9 77.4 3 84.7 16 84.0 4 77.8
8,600-9,000 21 85.3 3 89.8 11 88.1 8 92.6
9,100-9,500 9 88.7 2 93.2 8 91.1 1 94.4
9,600- 30 100.0 4 100.0 24 100.0 3 100.0
266 59 269 54
The Criteria of Radiation Employed ire the Study
TABLE 4.11 Continued
Distance from hypocenter 2,100-3,000 meters
49
Indoors, heavy bldg.
Outdoors, unshielded Outdoors, shielded Indoors,Jap. bldg. shelter
, ~, ' ~_
Leucocytes/mm.3 No. Cum. NO No. Cum. °70 No. Cum. % No. Cum. %
0- 500 ......... 0 0 0 0 0 0 0 0
600-1,000 ......... 0 0 0 0 0 0 0 0
1,100-1,500 ......... 0 0 0 0 1 .2 0 0
1,600-2,000 ......... 0 0 0 0 2 .6 0 0
2,100-2,500 ......... 5 1.9 0 0 3 1.3 0 0
2,600-3,000 ......... 3 3.1 1 2.6 9 3.2 1 9.1
3,100-3,500 ......... 8 6.1 1 5.3 16 6.6 0 9.1
3,600~,000 ......... 12 10.7 1 7.9 16 10.0 0 9.1
4,100-4,500 ......... 14 16.0 0 7.9 28 16.0 2 27.3
4,600-5,000 ......... 20 23.7 1 10.5 29 22.2 0 27.3
5,100-5,500 ......... 19 30.9 5 23.7 50 32.9 3 54.5
5,600-6,000 ......... 27 41.2 2 28.9 43 42.1 0 54.5
6,100-6,500 ......... 27 51.5 4 39.5 47 52.1 1 63.6
6,600-7,000 ......... 23 60.3 4 50.0 34 59.4 1 72.7
7,100-7,500 ......... 15 66.0 2 55.3 34 66.7 0 72.7
7,600-8,000 ......... 14 71.4 2 60.5 25 72.0 1 81.8
8,100-8,500 ......... 18 78.2 2 65.8 34 79.3 0 81.8
8,600-9,000 ......... 17 84.7 4 76.3 26 84.8 1 90.9
9,100-9,500 ......... 6 87.0 1 78.9 10 87.0 0 90.9
9,600- ......... 34 100.0 8 100.0 61 100.0 1 100.0
262 38 468 11
The concentration of values in the "9,600
and above" class would seem to indicate a
grouping of values which would vitiate attempts
to calculate a mean. However, generally speak-
ing, these observations suggest that a significant
number of persons in our radiation categories
3 and 4 probably developed leucopenia as that
term is here defined. An exact estimate of the
proportion is difficult because of the difference
between the way the Joint Commission's and
our own data are broken down, but in round
figures, based in part on the data in Table 4.11,
it can be estimated that some 5-10 per cent of
group 4 parents and 2-4 per cent of group 3
parents developed leucopenia.
The average amount of whole-body irradia-
tion which, when delivered over a period of a
day or two, will produce in man leucopenia of
this degree is not known with certainty. For
obvious reasons, there are not many pertinent
observations. Thus, studies of patients with
leukemia or multiple myeloma (e.g., Collins
and Loeffler, 1956), while valuable for thera-
peutic reasons, obviously do not permit extrap-
olation to normal persons. Of the more recent
investigations, the most valuable for present
purposes- although still, because of the nature
of the subjects, to be interpreted with caution-
are those of Nickson (1951), who found that
in three patients with carcinoma with metastases,
1 20r of whole-body irradiation with 400-kv
X-rays produced no significant leucopenia. Two
of these patients had a moderate leucocytosis
at the time of treatment, amounting to
14,700/mm.3 and 13,900/mm.3, respectively. A
fourth patient, also with carcinomatosis, who
was treated with 107r of 200-kv whole-body
X-rays on two successive days likewise failed
to develop significant leucopenia. The impro-
priety of extrapolating from such patients to
normal individuals is apparent. Furthermore, it
does not appear that these patients were fol-
lowed long enough for the detection of late
leucopenic effects. The studies of Hempelmann,
Lisco, and Hoffman (1952) on the few persons
who have been involved in industrial radiation
accidents are also especially pertinent. In one
-case, an individual was exposed to an amount
of irradiation estimated as the equivalent of
186 roentgens of 80-kv X-rays and 10.7 roent-
gens of Trays' and in another case, to the esti-
mated equivalent of 140r of 80-kv X-rays and
8.7r of y-rays. In neither case did leucopenia
as here defined develop.
In March of 1954 certain natives of the
Marshall Islands and a lesser number of Ameri
50 Genetic EJects of Atomic Bombs Chapter IV
can military personnel were accidentally exposed
to the fall-out of radioactive materials subse-
quent to the explosion of an experimental
thermonuclear device. Detailed hematological
studies were carried out on these individuals
(Cronkite, Bond, and Dunham, in manuscript).
Through the courtesy of Dr. E. P. Cronkite and
Mr. Hyman Hechter, the original data on the
Marshall Islanders regarding total leucocyte
counts during a 10 to 70-day period following
the exposure have been made available to us.
There were two groups of Marshall Islanders
involved, one group of 64 estimated to have
received an average dose of 175r of whole-body,
gamma radiation as measured in air, and a sec-
ond group of 18 estimated to have received an
average dose of 69r of gamma radiation as
measured in air. The actual dose received by the
Marshallese has been the subject of lively dis-
cussion. The observed maximum depression in
the total leucocyte count occurred between days
39 and 51 following the exposure (counts were
made every four days). On day 39, 3.1 per cent
of the Group I Marshallese were found to have
a leucopenia of 3,000 WBC/mm.3 or less; on
day 43, 6.5 per cent; on day 47, 3.1 per cent;
and on day 51, 0.0 per cent. None of the
Group II natives showed a leucopenia of this
degree during this period.
A comparison of these figures with the Japa-
nese figures cited above is biased by the fact
that the Marshall Island figures refer to the
period of peak depression, whereas the Japa-
nese data include a longer period of time.
Nevertheless, the important fact emerges that
in a group of healthy persons known with some
accuracy to have received a dose of whole-body
gamma irradiation of approximately 175r, the
frequency of leucopenia was probably no greater
than (if as great as) that occurring in the
category 4 parents of this study. The obvious
inference is that the average radiation dose
experienced by category 4 parents is at least
the equivalent of 200r of whole-body gamma
radiation, with category 3 parents receiving a
smaller average dose, but very likely one in
the neighborhood of the equivalent of 100r of
whole-body gamma radiation.
4.~.3 The proportion of ir~dividnals pro-
tected by various types of shielding. The final
consideration to be introduced into this attempt
to approximate the average radiation exposure
in the various categories is the proportion of
individuals experiencing various types of shield-
ing. Data are not available for the whole sam-
ple. However, in a special study carried out in
1953 on all parents falling in the 1,800-2,500
meter ring, a group especially critical to this
study, the breakdown shown in Table 4.12 was
observed for 4,515 Hiroshima parents and
2,083 Nagasaki parents. The important point
which emerges is the relatively small proportion
of persons classified as receiving heavy or
moderate shielding. It will be recalled that in
the radiation classification adopted here, the
report of "heavy" or "moderate" shielding re-
sulted in an individual being placed in a lower
radiation category. The contribution of such
individuals-whose shielding is especially
difficult to evaluate to the composition of
any radiation category is small.
TABLE 4.12 PROPORTIONS OF PARENTS EXPOSED IN
THE 1,800 - 2,500 METER RING WHO REPORTED
VARIOUS TYPES OF SHIELDING
Degree of shielding Hiroshima
Heavy 4.9
Moderate 2.5
Light 68.0
None 24.6
100.0
Nagasaki
15.9
3.0
67.0
14.1
00.0
4.9 Estimates of the average amount of ir-
ro~diortior' received by individuals ir; the various
exposure categories. We are now in a posi-
tion to approximate the average amount of
whole-body irradiation received by individuals
in categories 2 through 5. Category 2 individ-
uals, on the basis of the distance-dosage curve,
probably received on the average no more than
5-10 roentgens equivalent physical (rep's).
Category 3 survivors, on the same basis, as well
as the known incidence of leucopenia and the
shielding data, may be estimated on the average
to have received 50-100 rep's. The estimation of
the dosage in rep's for groups 4 and 5 is more
difficult because, in contrast to groups 2 and 3,
there is, on the basis of the distance-dosage
curves and the occurrence of radiation cataracts
in appreciable numbers of these survivors, a
significant neutron component in the irradiation
experienced by these persons. To make approxi-
mate allowance for this, we will express "the
equivalent of 300~00 roentgens of gamma
rays" suggested earlier as the average dose in
category 5, as 200-300 rep's, and on the same
grounds estimate the average dosage for cate
The Criteria of Padzation Employed in the Study
gory 4 individuals as 100-150 rep's. The arbi-
trary nature of these estimates will be apparent
to all students of radiobiology. Any one might
well be off by a factor of 2. We feel that any
attempt to be more specific cannot be justified.
In arriving at what some will term overly con-
servative estimates, we have been influenced by
the fact that traumatic and thermal injuries may
in a significant proportion of persons have
HIROSHIMA
05
5
do4
s
103
s
DOSE
(REP)
1o2
5
10
s
\> GAMMAS
NEUTRONS
GZ
~ 1 1 1 1
boo 1000 1500 2000 2s00 3000
105
s
104
5
103
5
DOSE
(REP)
1o2
s
10
s
51
neutrons in inducing genetic change (summary
in Symposium: Some Biological Effects of Ra-
diation from Nuclear Detonation, 1954~. How-
ever, it is important to recognize that the average
dosages estimated above indude, in the case of
category 4 and 5 persons, a component of high
effectiveness in producing genetic change.
Even should the upper rather than the lower
estimates of the average amount of radiation
NAGASAKI
NEUTRONS\
GAMMAS
\
\ \
1 ~
500 1000 1500 2000 2500 3000
SLANT DISTAI\1CE ( YDS)
SLANT DISTANCE (YDS)
FIGURE 4.5- Neutron and gamma radiation distance-dosage curves for the atomic bomb explosions at
Hiroshima and Nagasaki.
combined with ordinarily sublethal radiation
effects in causing death, thus lowering the mean
radiation dose expected in the various categories
on radiological grounds alone. On the other
hand, any allowance for residual irradiation
would revise the dose upward.
There are at present no published data which
permit making a realistic estimate of the con-
tribution of fast and slow neutrons to the total
radiation spectrum. This is unfortunate in view
of the relatively high biological efficiency of
received by survivors prove correct, the fact is
clear that in the terms of the radiation geneti-
cist, these are small doses indeed. This was
recognized from the outset. But despite the im-
probability of being able to detect induced
genetic effects in this material, there was no
doubt in the minds of those who considered the
problem initially, at all echelons, that "this
unique possibility for demonstrating genetic
effects caused by atomic radiation should not
be lost" (cf. p. 2~.
52 Genetic Efects of Atomic Bombs Chapter IV
Note added ire proof. At the time this chap-
ter was written, only the distance-dosage curves
for a "nominal" atomic bomb had been pub-
l~shed. However, since this manuscript went to
press, distance-dosage curves, in terms of neutron
and gamma radiation, have been declassified for
both Hiroshima and Nagasaki. These are pre-
sented in Fig. 4.5. The gamma curves for the two
cities are quite comparable, and correspond satis-
factorily with those published earlier for the ex-
plosion of a "nominal" atomic bomb. How-
ever, it will be noted that the neutron curves for
the two cities appear to differ significantly,
with, at a given distance, rather more radiation
of this type in Hiroshima than in Nagasaki.
The curve for the latter city approximates that
published earlier for the explosion of a "nomi
nal" bomb. In view of the many uncertainties
that enter into assigning mean dosages to our
radiation exposure categories, it is not felt that
these new data warrant a revision of the esti-
mates given in this chapter. On the other hankl,
it is clear that there is a very strong neutron
component in the radiation experienced by cate-
gory 4 and 5 parents in Hiroshima, and in this
connection, it will be recalled that approxi-
mately 68 per cent of all category 4 or 5 parents
were from Hiroshima. In view of the high rela-
tive effectiveness of neutrons in inducing ge-
netic change, the publication of these new
curves has the effect of increasing the genetic
significance to be attached to the observations
herein to be reported.
