383.
What may safely be concluded from the data on occupationally—exposed
people is that of neoplastic diseases, particularly leukaemia and skin cancer,
are real effects, particularly in old radiologists.
Some life-span reduction
may also have been present in old radiologists who were presumably exposed to
very high doses;
however, this effect was reported unanimously to have dis-
appeared in more recent years in radiology specialists entering their profession
after the radiation protection rules have been in operation.
If this conclu-
Sion is true, it should logically follow that within the range of doses recommended since that time
(that is for exposure rates lower than 1
R/week as a
maximum) no reduction of life-span can be expected and any residual prevalence
of leukaemia and tumour induction would be insufficient to cause an appreciable
shortening of life in the human species.
384.
In principle, radiotherapy patients have a number of favourable charac-—
teristics of epidemiological studies (knowledge of the dose, good standard of
medical follow-up) which might counterbalance some negative aspects (small
samples, death associated with the primary disease).
In practice, the three
small series available on women surviving radiotherapy for uterine cancer [S40,
N11, Z1] have yielded negative answers in respect to life-shortening.
The size
of these surveys is certainly inadequate for any firm conclusion, but a negative
finding would not be unexpected under conditions where only a small fraction of
the body was irradiated.
It is known from animal experimentation that life-
shortening is less likely to be observed after partial-body exposure (see
paragraphs 314-32).
385.
The experience on the ankylosing spondylitis patients [C28] does show
at a first sight a small but significant prevalence of unspecific mortality.
However, a more thorough analysis of the causes of death, discussion of the
epidemiological evidence and consideration of the time-course of the excess
mortality raise some doubt on the reality of this observation.
On these
grounds a dependence of the excess non-specific mortality on the spondylitis
itself cannot be rejected and thus the survey seems inadequate to validate the
existence of a radiation-induced non-specific shortening of life.
386.
On the whole, therefore, the evidence coming from radiotherapy patients
is negative for the presence of the life-shortening effect under discussion.
Naturally, the weight to be attached to these data is relatively smaller than