THE SHORTER-TERM BIOLOGICAL HAZARDS OF A FALLOUT FIELD
becomes very small compared to the entrance
air or ontrancetissue doses, and the depth-dose
curve is far from flat. This type of “energy
dependence” and the resultant biological effect.
has been studied [18, 19], and is diseussed below.
lt should be noted that while fallout gamma
radiation has been termed ‘soft,’ only a very
small percentage of the primary beamis below
100 to 200 kev under most. practical cireumstances [1], This is equivalent. in penetrating
power in tissue to # highly filtered X-ray machine of 250 or higher peak voltage, or KVP.
Thus the fallout gamma radiation must be
considered quite penetrating in terms of
biological effectiveness.
Correlation of depth-dose patterns with bioluytcal effect.—-From the depth-dose considerations
from the literature are collected, shows this
to be true, The LDvalues for dogs and
swine are given in the tables in terms of entrance air dose, as well as in terms of the entrance, midline and exit tissue doses.
A better correlation between dose and effect
would be expected if tissue dose is used unless
(a) an energy dependence of biological effect
is present, (6) marked differences in the shape
of the depth-dose pattern exist, or (¢) strain
differences in the degree of biological effect.
exist.
“Energy dependence” of biological effect as
commonly used has inclided usually two
separate phenomena to varying degrees, i. e.,
(a) a “true” or intrinsic energy dependence
outlined above, wide variations in the dose
in which dose deposition through the irradiated
objects compared is well known and uniform,
as air dose, would be expected with different
same dose reflect different properties of the
required for a given biological effect, expressed
exposure conditions. A glance at Tables 1
and TJ, in which large animal mortality data
"ih
fate
tak
tt ty
GEOMETRICAL, ENERGY FACTORS---EFFECT OF RADIATIONS ON MAN
and quantitative differences in effect for the
radiations, related to linear ion transfer (LET),
or specific ionization; and (6) an “apparent”
Taste I—LD» DOSES FOR DOGS EXPOSED UNDER DIFFERENT GEOMETRY CONDITIONS
Radiation factors
Method of
expontire
Radiation used
Filter (mm >]
HV
(mm.)
TSD (em,)
Unilateral
280 KVP X-ray
14.2 Al Par-
‘Unilateral
(from
1,000 KVP Xray (G. E,
12.7 Pb... S$. Pb ...] Wa... -
throm
above).
(Plekerl.
above),
transmitied
beam).
abolic 0.6
Cu,
LDa dose
Dose rate
(r/min.)
wneef
2.18 Cu....[ 102......-.
1...
0.
En-
En
Mid-
Exit
Reference
ma
trance
ale
trance
tissue
line
tissue
tissue
16
480:
562
382
160
Michaelson,»
3
450
405
360
202
Michaelson,*
Unilateral... .)
2,0u0 KVP X-
ray (GE,
68 Fe dn
None...
Bitateral... .
Cnherent
1,000 KVP X-
ray (0. E.,
radial heamst.
100Q KVP Xray (G. E.,
:
radial heam)
Bilateral... ...{ 20KVP XBilateral...
Multti-Gouren
Field.
energy
ray (G. E.,
cadiat beam).
only).
pum
TSO {em.)
4a Ph... ./ 200.
herent).
radial beam).
Unilateral ....{ Bomb gamma .{
7
HVE
¢(mni.}
|.
oe
200
16
-|
BS
aaa
270
242
279
‘Tullis, NMRI
Aboutaio}.
ag}
....|
30
.
| 462.41. .| Varinble
dependence secondary to differences
These effects are considered
Low energy radiation can be considered first,
and beta radiation provides the absurd case
because it penetrates only a few mm. in
tissue. Thus “total body” beta radiation
in reality resulis in a type of partial body
radiation of one organ, (he skin. Energyis not
deposited at depths sufficient to produce the
“total body” irradiation syndrome of penetrating gamma radiation. Very low energy
X or gammaradiation, e. g., 50 KVP X-rays,
result in virtually the same picture as beta
radiation when applied to the entire body surface, and the acule LDy here is of the order
of several thousand r or rep to the skin, as
opposed to a few hundred r for penetrating
312
265
266
268
Cronkite, NMRI
@),
262
282
262
Gleiser, NMRI
@2,
Boohe + Bishop
Rochester (23).
384 |... 8 Shiveley « et al.
In mice, with essentially bilateral (uniform)
wradiation [18], the transition occurs at somewhere between 80 and 135 KVP; at shout
wwe
fw we[e ween cefeweenee
reys. This would be expected with
type of partial body radiation.
any
with body size and the geometry of exposure.
80 KVP the LD, expressed as tissue dose or
air dose, begins to rise rapidly.
448029 0O—-bs——6
qm).
43 Pb...
herent).
316
«8. Michaelson, J. N. Shiveley and J. Howland, personel communteation.
* Calculated or estimated; value not given in references cited.
(24.
63FotIne
Lb
Bilateral. ...| Oo gamma... None...,..--' 10.8 Ph...JH8...... - Powe nae
ay).
Bond, NRDL
(25).
LB
Not gefvanin report
Tullis, NMR
3n2
As the beam energy increases, the effects of
penetrating whole body radiation do appear,
and the energy level where this occurs varies
1,000 KVP... ...
145
BBs
Bond, USNRDL
an.
Bilateral.......{
Ta
402
260
vee af
225
425
256
.
aah
%
230
200... .
-
.
uy
44 Ph...| 200.. .-..
Tallis, NMRI
m7.
3
6.8 Fe. ...-.) 4.8 Ph...
130
He
Man weneeenee
4a Fe (nherent),
at
20 Fb. 2
110... --..
radial beam),
5a0
Tullis, NMRI
252
-| 3000 KVP.....
S00
367
252
Baateral.......| 2.000 KVP Xray (G. E.,
Ls
252
282
Bhatersl..
Exit
tissue
357
281
ray (@. E.,
Tadial beam),
Midline
Sig
G
(Inherent) ..] 2.0 pb...
tissue
a
WG... fb
Bilateral......- 1,000 KVP X-
tissue
alr}
eo
100. ....
beam).
Entrance
=| 3.
High veria- |... ...
ble.
1S
Argonne(20).
Bond, USNRDL
17).
ble.
Entrance
100
100...
Prosser et at.
High varia-
Reference
ma
Cnheront:
onty),
Cot gamma. .| None...
in penetration.
below.
LDdone
weep
Dose rate
(ymin)
15...
2... .| 1,000 yds .|
L000 yds.
|} 880 |...
(4).
7
Filter (rman.)
None .......]..-.-....-.-]
|.--..-.-.---
210
Radiatlon factors
Hadiatien used
05 Cu.
O8Cul0
AL
256
eqporure
.| Bomb gamma...)
{G. E.)
271
Rochester,
{
Methud of
-] MOK VE Xray
Milateral.......| @O KVP Kany
{@. E., radial
nl
Rochester.
75
Tarve [IY -LDg DOSES FOR SWINE EXPOSED UNDER DIFFERENT GEOMETRYCONDITIONS
In the rabbit,
(at).
Rast, et a, Oak
Ridge (25).
the change oceurs at a higher KVP, probably
near 150 KVP. With dogs, the LD,» for 100
KVP X-rays (midline tissue dose) is 1.4 times
that for 250 KVP, thus the transition occurs
somewhere between these energies.
From
Table II, it is seen that above 250 KVP, the
LD, for dogs (bilateral X-irradiation, midline
tissue dose) is independent of energy. No such
data are available on larger animals the size
of man; however, it appears likely from depth-
dose curves that the transition would occur
at 250 KVP or somewhat higher.
The above “energy dependence” thusis seen
to bein reality a pseudo energy dependence—if
the radiation dose cannot be delivered te the
vital tissues, “energy dependence” of effect cannot exist. This effect has nothing to do with
relative biological effectiveness (RBE) in the
strictuse of the term, although RBE frequently
is used loosely to include it.
As stated above,
many of the radiations of concern in hazard
evaluation are sufficiently energetic such that
this factor is not large. The chief exceptions
are bomb neutrons and beta radiation. With
these radiations, however, the effect exceeds by
far in magnilude the effect resulting from
intrinsic RBE.
A possible “true” energy dependence of biological effect on energy over the ranges of in-