the model's analysis are consistent with available data at comparatively low
doses, including the convex upward life-shortening responses.
It predicts
enhancement of effects after fractionated exposure to 605, gamma rays and an
approximately linear response in most cases of acute exposure to low-LET radiation.
The model also provides a means of extrapolating between mouse
strains or age groups, an extrapolation which can be achieved by changing a
single parameter [S48].
D.
1.
35.
LIFE-SHORTENING AND AGING
Specific and non-specific life-shortening
There is considerable discussion in many of the papers reviewed about
the specificity or non-specificity of the life-shortening observed in a variety of experimental situations.
Semantic considerations as well as impor-
tant reasons of substance have complicated this issue.
It should first be
recognized that speculations about specificity often conceal the lack of good
pathological analysis.
some specific cause.
Life-shortening must be due, if properly assessed, to
However, the word specific has been taken to mean that
the irradiated animals die earlier than their controls with a spectrum of
diseases or causes of death different from the spectrum seen in the non-irradiated controls.
36.
Since it is well known that not all diseases are readily induced by ra-
diation, to expect that radiation acts non-specifically in shortening the
average life of an animal population would be equivalent to reject all radiobiological experience.
Recently the discussion has been more reasonably cen-
tered on whether or not radiation may produce life-shortening by induction of
tumours and how much of the observed shortening could be accounted for by
neoplastic diseases.
Even though never stated quite clearly, the words spe-
cific and non-specific have therefore been taken to indicate neoplastic and
non-neoplastic contributions to life-shortening.
Under these conditions, the
question of specificity of the life-shortening action is quite legitimate and
of great practical significance.
37.
Mole
In discussing the problem of specificity, ICRP Publication 14
‘I1] and
'M2, M3] point out that in order to detect a general non-specific