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
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