time, since the pathological response is saturated in this
experiment, it is inappropriate to draw any inference about
the magnitude of the response at smalier burdens.
burden
(at death)
The smallest
in a dog showing lung cancer was 0.2 uCi.
Presumably this would correspond to a particle burden of
about 107 particles.
Burdens which are smaller by orders cf
magnitude may still induce a substantial incidence of cancer.
Indeed,
the cancers risk may,
as
for skin and soft tissues,
,
correspond to a risk per particle in the neighborhood of
1/1000
Critical Particle Activity
Be
i:
te le
14
ete he ee
24
st ek
-
4
VI
to 1/10,000.
icles would be expected to result in these
re
hich cancer probabilities.
As the particle size or specific
activity per particle is reduced so is the dosage to the
Surrounding tissue.
Indeed, at sufficientiy smail carticle
Size or specific activity, one would expect the radiation
insult to behave similar to uniform irradiation.
The study
of Albert on induction of cancer in rat skin indicates a
precipitous change
in the dose response curve as the dosage
exceeds 1,000 rem”.
(See Figure 2).
This suggests that a
particular level of tissue damage must occur before this
unique carcinogenic response occurs.
95/
Albert,
R.E.,
et al,
The experiments of
Radiation Res.
30, Op.
cit.,
pp.
515-5
Figure 7; reproduced in Geesaman, UCRL-50387 Addendum, Op. cit.,
p.
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