epithelial
REPAIR ASSOCIATED WITH EROSIVE EFFECTS OF FALLOUT IN INDIVIDUALS, GROUPS
THE SHORTER-TERM BIOLOGICAL HAZARDS OF A FALLOUT FIELD
sloughing
in
the
months; and (4) that the acute reaction of
degeneration and repair (Phase I) is followed
bya long period of apparent normality (Phase
11) and, in turn, by a terminal period (Phase
TII)--which, aside from infections and accidents, involves degencrative diseascs and neoplasia mainly, Inherent, but not made evident
gastrointestinal
tract, hemorrhage, bloodclotting failure, epilation, sterility, cataract, etc. It is of practical,
and also some scientific, significance to deal
with the net effects of radiation in individuals
and in population groups, as a means of gaining
a. Reserve energy-—ability to do a 10-mile
march.
&. Normal work—-ability to perform a regular
day’s work.
ec. Lassitude and easyfatigue.
d. Milnes (sickness, discomfort, anxiety) but
capable ofself care.
Phaseis foreshortened by exposure to radiation,
and that the Terminal Phase involves the same
kinds of features as are present irrespective of
radiation.
of people can do followingirradiation.
Implications of Figure 1 are: (1) That the
growing tissues
work capacityorillness as follows:
bythe figure, is the fact that the Intermediate
impressions of what individuals and groupings
necrosis in
were chosen to represent different levels of
e. Illness, but with need of nursing care.
These terms or expressions were then ar-
Dealing with short duration exposures (minutes, seconds, or less), Figure 2 pictures performance ability during the Acute Phase—
(bone marrow,
lymph nodes, spleen, gastrointestinal epithelium, germinal epithelium of the testis, and
skin) is precipitous following near lethal irradiation exposures; (2) that if the necrosis is
ranged on a scale in order from 6 downward,
respectively, as shown in the figure, and, on
the basis of clinical, hematological and histo-
the phaseof tissue necrosis and replenishment
(especially in the gastrointestinal tract and
hemopoietic organs). The scale for performance
ability—work capacity as it is labeled—is some-
excessive, death will result; (3) thatif it is not
too extreme, repair by means of mitosis and
pathological information, choices were made
as to the level at which the majority of people
exposed would be expected to exist at different
times after different acute exposures.
what arbitrary, but, as will be seen, is never-
theless useful. It was developed in the following manner. Deacriptive terms or expressions
tissue replenishment will take place, reaching
the normal range in a matter of weeks or
}
‘This
gave the curves as shown. Since some interpolation was necessary to obtain smooth
curves and since the descriptive terms did not
haveprecisely uniform quantitativesignificance,
the values on the scale cannot be said to repre~
sent the descriptive terms concretely or vice
versa. The development as a whole, however,
gives a consistent picture, and one that has
meaning.
In terms of integrated effects of near lethal
dose of radiation of short duration on the body
as a whole, the following can be said: (1) That
there is an immediate condition of sickness or
shock; (2) that the degree of illness varies
10% SURVIVING
WORK CAPACITY
directly with dose; (3) that the iliness may be
DAYS
Fiaurx 2,—Work capactty—Acute exposure.
a
200
400-60
1000
any dramatic effects at the beginning, but
work capacity falls with accumulation of the
integrated effects. Tmplications of the curves
are: (1) That for doses of 20 r per day, work
capacity becomes noticeably reduced in 2 to 3
weeks with death occurring as an end result
at about 2 months; (2) that for doses of 5 r
per day, reduction in work capacity is barely
gradually with death occurring in 3 to 4 years;
and (3) that for doses of 1 r per daythere is no
noticeable reduction in work capacity in 3
years time.
Of importance in connection with protracted
radiation is the fact that damage and repair—
moreparticularly, cell destruction and replacement-—go along togetherin the growingtissues,
and also the fact that defects in the organism
begin to show only when the rate of destruction
exceeds the rate of repair. From Figure 3,
there is indication that the threshold of injury
to the organism, so far as work capacity is con-
cerned, is about 1 r per day, and from this it
follows that the resiliency of the growing tissues
in general—that is, their maximum capacity to
regenerate—must be offset or counteracted
effectively by radiation doses in the neighborhood of 1 r per day.
How great the resiliency of tissues may be
and how much reserve capacity exists in at
least some of the organs, are indicated by the
following facts (developed from animal experi-
ments mainly): Three-fourths of a liver can be
removed by surgery and a whole liver will regenerate; one and a half kidneys can be extirpated without reducing normal excretory effi~
(5) that during the fourth week, recovery sets
drawn off every two and a half weeks (i. e.,
in (in survivors), which then for certain organs
ovennetbneerelvarleandac
40
60 BD 100
plan as employed in connection with Figure 2.
Here a shock response is totally absent due to
less during the second to fourth or fifth days;
(4) that during the second and third weeks
there is a precipitous fall in fitness which coin-
cides with the cascade of tissue necrosis; and
nm
8&9
noticeable in 3 months but that it does fall
f. Death.
oe ee
88
which probably would be typical for most or
all mammelian forms. The figure gives orientation also with respect to the integrated effects
of key reactions, such as the blood dyscrasias,
(gastrointestinal and hemopoietic which in
particular are of vital importance) reaches the
normal range in 2 to 4 months.
Turning to protracted or intermittent exposures, Figure 3 shows performance ability
at different times in connection with daily
treatments of different amounts, using the same
ciency ; and a full body content of blood can be
blood being removed at intervals during such
periods) without distortion or reduction of the
peripheral blood picture. On the basis of such
information, it would seem that the subthreshold or subliminal effects of protracted irradiation may bequite large in terms ofcell destruction and replacement—that is, beyond that
which takes place during the normal course of