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.