y
=
100 (1 -
e709 9379 Ay
(17)
and in the case of neutron irradiation
y
=
~0.374
100 (1-e 0.3748 A)
(18)
By inspection, the above relationships interpolate the low-LET data quite adequately, but fail to pruperly follow the fairly high effect seen at the very
low doses of neutrons and the tendency to merge of the x-ray and neutron data
in the high-dose region of the graph.
y
=
The relationship
100 (1 - e& VA)
(19)
which fits the neutron data with the following values
y
=
100 (1 - 970-4883 VA)
seemed more adequate for that purpose.
(20)
But an even better interpolation was
obtained by least-square fitting the data with the relationship
y
=
100 (1 -
-0.4883 A* )
(21)
5-0-4863 gels )
(22)
e
solved as
y
=
100 (1 -
It should be noted that even in the case of chronic radiation exposure the low
doses of neutrons appear somewhat more effective than the high doses in bringing about life-shortening damage (see paragraphs 211 - 213).
143. Another type of analysis is one where the percentage life-shortening is
plotted versus the dose accumulated at the various dose rates under duration-
of-life exposure.
Data obtained in the same experimental series shown in
Figure IX are plotted in Figure X, separately for the x- and gamma-ray and
for the neutron series.
At increasing doses the life-shortening effect of
low-LET radiation also increases in an apparently linear fashion at the low
doses and then with a progressively accentuated upper concavity up to doses
of about 6000 rad administered for the duration of life at dose rates of about
20 rad/day.