876 GENETIC AND BIOLOGICAL EFFECTS OF RADIATION 
Table I. — Thirty-Day Mortality of Swine after Exposure to Ionizing Radiations under Various Experimental 
Conditions 
LDeo/ao 
Method of 
Midline, 
Age 
Av. Wt. 
Ref. 
Source 
exposure 
Dose Rate 
In air. 
rads 
(Months) 
(kg) 
No. 
X-ray, 2000 Kvp 
. . Unilateral 
15 R/min 
600 R 
300* 
4.5-6.5 
62 
3 
X-ray, 2000 Kvp 
-- Bilateral 
15 R/min 
350-400 R 
223* 
4.5-6.5 
62 
3 
X-ray, 1000 Kvp 
— Bilateral 
30 R/min... 
510 R 
242* 

50-104 
3 
Bomb, 7 
... Unilateral 
230 R 
185* 
4.6 
30 
8 
X-ray, 1 Mvp 
... Bilateral 
9-10 R/min 
399 R 
262* 
8-9 
110 
2 
""Co, 7 
.... 4 It field 
18-29 R/min 
335 R 
211* 
34 
6 
""Co, 7-. 
... 4 TT field- 
18-29 R/min 
393 R 
221* 
68 
6 
«»Co, 7.. 
.... Multisource** 
0.85 R/min 
618 R 
359* 
6 
75 
1 
«°Co, 7 
.. . Multisource" 
1 rad/min 
710 rads 
369 
8 
114 
3 
«<>Co, 7 
.... Multisource** 
10 rads/min 
435 rads 
226 
8 
114 
9 
""Co, 7 
.... Multisource** 
50 rads/min 
360 rads 
187 
8 
114 
9 
Bomb, n-T- 
. .. Unilateral 
486 rads 
4 
38 
4 
Fission Neutrons 
... Unilateral _ 
16-20 rads/mins ... 
869 rads 
370 
9-12 
160 
6 
Fission Neutrons 
... Bilateral 
16-20 rads/mins .. 
820 rads 
350 
9-12 
150 
6 
14 Mev Neutrons 
.... Bilateral 
-. . 10 rads-min 
585 rads 
525 
8 
90 
7 
•Calculated from 
data contained in the 
respective reports as 
referenced. 
**Predominately bilateral. 
Table II. — Calculated LDsono Doses for '"Co Gamma Rays, Fission Neutron and H-MeV Neutrons and Estimated 
RBE's for Neutrons. Dose Rates Were Approximately 10 Rads/Minute for Gamma Rays and H-MeV Neutrons 
and 18 Rads/Minute for Fission Neutrons* 
RBE 
60Co/ 80Co/ 
eoCo, Fission 14 MeV Fission 14MeV 
Gamma Neutrons Neutrons Neutrons Neutrons 
820 585 .5 .7 
263 457 .9 .5 
370 415 .7 .6 
385 415 .7 .7 
Tissue dose in air (rads) 435 
Midline tissue dose (rads)..... _ 225 
Av. tissue dose (rads)** 265 
Av. bone marrow dose (rads)_ 281 
*Brown and Haywood.' 
* Average dose across the abdomen. 
and water. The degree of change was greatest 
in the swine irradiated with 14-MeV neutrons. 
Constipation was common in the swine ir- 
radiated with 14-MeV neutrons, but was not 
evident in the swine irradiated with either fis- 
sion neutrons or gamma rays. These differences 
were indicative of the degree of damage to the 
gastrointestinal tract. Pathologic alterations in 
the skin were severe only in the swine irradiated 
with fission neutrons. 
Exposure Aspect 
Nonuniform radiation doses cause variation 
in the dose-mortality response of swine. This 
has been demonstrated by bilateral and uni- 
lateral irradiation with X-rays ^ and neutrons.^ 
Such variations contribute to the enigma of ex- 
pression of radiation dose relative to effects on 
animals. Various dose parameters (average tis- 
sue dose, midline tissue dose, etc.) have been 
used, but none have proven completely satis- 
factory in comparative analyses. A method has 
been proposed for evaluating nonuniform ex- 
posures on the basis of dose to the bone mar- 
row.^**. Dose-survival curve for stem cells in 
swine must be established, however, before this 
method will have merit over average tissue dose 
in this species.^ 
Dose Rate 
Another variable affecting an animal's re- 
sponse to a dose of photon radiation is the time 
over which the dose is delivered. Early mortal- 
ity was enhanced by an increase in dose rate in 
small laboratory animals."-^^ This phenomenon 
has been tested on swine. Duroc swine, approxi- 
mately 8 months old having an average weight 
of 114 kg, were exposed to •'^Co gamma radia- 
tion at dose rates of 1, 10, and 50 rads per min- 
ute (tissue dose in air).^ The LD50/30 values 
