Discussion of the Biological Factor: As longer periods of time are involved in the delivery of a given radiation dose, lesser biological effects my be expected, Fron the time of fallout ontil the time of evacuation probably will be a matter of howrs wiich has been oonsidered essentially an instantan- @ous dose, 1,0e., the biological dose factor ie 1/1. From the tine evacuation eoulé te accomplished to time of return probably would be a matter of days, @o the biological factor has been estimated at 3/4. Fron 15 days after fallout until one year later is essentially a@ duration of one year, so the biological factor has been estimated at a/z. It will be noted there 1s no caleviation after one year, because it is expected under actual conditions of radiological and weathering that protably no significant dose will be delivered after a years tine. It is recognized that t:e precise quantities sugrested for the biolor- ical factor cannot be supported by conclusive evidence, It is reasonable to expect tiat tie delivery of a given radiation dose over @ period of many days will have less biolorical effectiveness than an instantaneous one (nerlecting genetic effects) and that the extension ef the period to essentially ow year miould yield a still lower biological factor, One piece of supportive evidence is the work of Stranicvist* where I-ray doses to the skin rere fractionated into equal daily amounts, and the biolerical effects compared to a one treat- ment dose. a-ideaes plot ef total doses versus days after initial treatment yielded straight lines, For example, the curve for skin necrosis indicated a ratio of 3000/6700 reentgens for a one treatment versus 15 daily equally “Sievert, Falf H, "The “olerance Tose and the Prevention of Injuries Caused by Ionizing Radiations*. (Py tish Jovres/ 9+ Roda Lay Vol. IX,Ho.236,Arg. 197 - A+ c- rors SR : ‘