-13-
UCRL-3644
the life-span loss,if attributed to radiation, is
_£ aay 365days/yr = - 7 to - 4 days per r of whole-body exposure .
Such a number is still subject to considerable possible revision; but many
different estimates give values of 1 to 30 days lost per roentgen of radiation
exposure, and the probable value for humans is in the range of 5 to 10 days
lost per roentgen.
A question exists whether we can justifiably extrapolate effects such
as life-span lost per roentgen from measures that are mostly determined in
the range of 100 to1000 r. The evidence is that, over the range that can be
tested, the effect is linearly proportional to the radiation exposure; and the
information fits an extrapolation to zero shortening of life span at zero artificial radiation exposure. There is additional evidence in the effects of radiation upon cells (as distinguished from entire organisms), in which lethal
damage to cells per roentgen also appears to be proportional to total radiation
exposure.
Such estimates agree for cells in the mouse, the rat, the rabbit,
the guinea pig, and man. This experimental evidence that effect of radiation
on cells is in linear proportion to radiation exposure of from 15 to several
thousand roentgens provides a reasonable basis for understanding the lifeshortening effects of radiation.
Furthermore, the life-shortening effects are consistent in order of
magnitude with the genetic effects of radiation upon cells (2 to 3 cells affected
per 1000 cells per roentgen). The genetic effect of radiation has been shown
to be acceptably proportional to radiation exposure from 25 r to 8,000 r.
The sum of systematic evaluations of such effects of radiation as
mutation induction, cell destruction, and life-span shortening indicates that
these effects are permanent and represent the quantum interactions of radiation
randomly affecting body cellular structure. The concept of quantum interactions with matter justifies extrapolation to the probability that a single
quantum of radiation reacts with an individual molecule.
Although all recent evidence suggests that radiation effect is proportional
to radiation exposure, such effects must be viewed together with other common
environmental factors that modify health. A scheme is used here in which the
effect upon health is expressed as an induction of aging (this is expressed as
loss in physiologic lifetime, or minus time, written ''-n years'') or as a postponement of aging (expressed conversely as lifetime gained, or plus time,
"+n years"). These factors all appear to have a general action upon disease
“This estimation of life span lost or gained is in terms of relative physiologic
age change. Change in life expectancy may be estimated by determining life
expectancy at a given age in terms of a given age + n years' change in apparent
age. Thus, a person of age 40 has a normal life expectancy of 31.1 years. If
his physiologic age is 50 (because of a sum of factors predicting -10 years age
over the average), his life expectancy (from life tables) is 22.8 years, or an
average loss of life span of 8.3 years. Thus the life expectancy lost is somewhat less than physiologic time lost.