- 27 -
at low dose rates.
By ccntrast, structural changes resulting from
alpha interactions are directly proportional to the number of inter-
‘actions and are independent of alpha interaction rates,"
The proper interpretation or expression of the content of the quoted
statement under comment and the quoted statements in the comments, is
that for alpha radiation the incidence of induced chromosomal
structural changes increases linearly (proportionally) with increasing
dose, and also with dose rate under realistic conditions for internal
alpha emitters where dose rate and dose are dependent upon amounts of
alpha emitter present.
On this linear relationship basis the effective-
ness of the alpha radiation per unit dose (efficiency) is independent
of dose rate, as contrasted with the dose-squared dose-effect relationship for x- or y-rays and the dependence of effectiveness and efficiency
on dose size and dose rate.
However, it should be pointed out that either
the linear or the dose-squared dose-effect relationship pertains only
to the point of saturation of effect, with no further increase in the
specified effect with further increase in dose.
Furthermore, at very
low doses of alpha radiation, if there were any reduction in efficiency
of production of any particular type of chromosomal effect or other
effect, which could be possible, this would indicate the possibility
of an effect-reducing influence of reduced dose-rate,
Page 13, lines 19-22 - "However, the cumulative effects of
internal alpha emitters gives rise to an increase in the populations
of mutated cells (cells with viable structural changes in their
chromosomes) and in the health consequences of such changes."
Comments:
This is true insofar as it means that the increasing dose with