138
THE SHORTER-TEERM BPROLOGICAL HAZARDS OF A FALLOUT FIELD
Parker has advocated the use of beta detecting
imstruments with ehamber walls corresponding
in milhgrams per square centimeter to the
thickness of the relatively inert epidermal
layer {20}. Thus in expressing skin dosage it
is probably more informative to use the depth
dose at the depth of the epidermal layer of the
skin.
The above table also indicates the species
difference in skin sensitivity to beta radiation.
Rabbits and sheep required larger doses than
mice to produce the same effect with roughly
the same energy beta.
Porcine skin, which is
rabbit or sheep skin.
Some of these differ-
reputedly more Hike human skin than other
aniinals, apperently is more sensitive than the
ences, nside from apectes differences, may be
die to variation in thickness of the skin of
different species and diflecences: in techniques
used,
Table 2 shows beta dosage data from some
human experiments and accidents found to
produce various effects on the skin.
These
datw must be interpreted with great caution
due to differences in experimental techniques
and dosimetry, The severity of the skin
reactions iso represented by degrees. A first
degree renetion implies erythemn and/or dry
desquamiation;s a second degree, transepidermal
necrosis with ulecration: and third degree,
further breakdown of the skin with the development oof chromic radiation dermatitis, Tt ean
be seen that Chere ia a considerable variation in
dose reported to produce the various renetions,
In the Marshallese the skin dose could not be
estimated with any degree of accuracy due to
the complicated smear of beta spectra varying
with time and the uneven distribution of the
material on the skin.
The beta component of the falout was found
to have two major peaks of energy, one at 100
kev which accounted for 50-80 percent of the
activity and one at 600 key which accounted
for 20-50 percent of the activity Fifty
percent attenuation of the 100 kev component
occurs at about 80 microns, nbout the depth of
the epidermis. Fifty percent attenuation of the
600 kev component occurs at about 800 microns,
fairly deep in the dermis; deep enough to
irradiate many of the hair follicles. The
relatively soft nature of the radiation was borne
ont hy the superficinl nature of most of tie
lesions that. developed,
A very rough biological estimate of the dose
to the sealp of the Rongelap people might be
made by using the index of epilation. It ig
known that with 200 kvp N-ray a dose of about
400 fr is necessary to produce epilation, and
doses above about 700 r produce permanent.
epilation.
Since regrowth of hair took place
in the epilated Marshallese the dose to the
hair follicles must have been in the above range.
This dose must linve been largely from the 600
kev cemponent. Therefore tho surfaee dose
from this component must tiave been 4 to 5
times higher or in the range of £600 4,500 rep,
The surface dose from the more abundant lOO
kev component must fave been much higher, by
Tanne 2.—~ HUMAN EXPOSURE TO BETA RADIATION
we
Investigator
-
|
=
Radlotion
Wirth and Raper... 2.22222 eee a
Dol. 8.
Se ee eee
Low-Heer.. 22 8 eee
Tp
Robbins ef af. 220.0 _- .--- ...|
P30 ee eee
PM eee.
PM eee eee
Gathode rays (1,200 kv)......--}
Fist. dose (rep}
635
1,180
*143
7, 000-17, OOO
1,000- 2,000
Knowlton efal_ oo ee Fission products._...---.------ 4, 000- 4,000
Pol ee ee (tL Mev, ave. energy)... -.----] 5, 000-10, 000
Dol. eee eee do... - ee eee eee 5, 000-10, 000
ee
Heaction
|
sarting
ee.
lst degree (threshold).
2nd degree (threshold).
Ist degree (threshold).
2nd degree.
3rd degree.
2nd degree.
3rd degree.
3rd degree,
No... eee eee | . do. 2 ee ee eee eee 8, 000-16, 000 3rd degree.
*Estimnated dose in Ist min. layer.
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