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-

Select target paragraph3