be about five-fold larger. Added to these would
be a smaller number caused by chromosomal
defects and recessive diseases. (c) Risk Relative
to Current Prevalence of Serious Disabilities.
In addition to those in (b) caused bysingle-gene
defects and chromosome aberrations are congenital abnormalities and constitutional diseases which are partly genetic. It is estimated
that the total incidence from a}] these including
those in (b) above, would be between 1100 and
27,000 per year at equilibrium (again, based on
3.6 million births). This would be about 0.75%
at equilibrium, or 0.1% in thefirst generation.
(d) The Risk in Terms of Overal] I]-Health. The
most tangible measure of total] genetic damage
is probably “ill-health” which includes but is
not limited to the above categories. It is
thought that between 5% and 50% ofill-health
is proportional to the mutation rate. Using a
value of 20% and a doubling dose of 20 rem, we
can calculate that 5 rem per generation would
eventually lead to an increase of 5% in theill-
health of the population. Using estimates of
the financial costsofill-health, such effects can
be measured in dollarsif this is needed for cost-
benefit analysis.
Until recently, it has been taken for granted
that genetic risks from exposure of populations to ionizing radiation near background
levels were of much greater import than were
somatic risks. However, this assumption can no
longer be madeif linear non-threshold relation-
ships are accepted as a basis for estimating
cancer risks. Based on knowledge of mecha-
nisms (admittedly incomplete) it must be stated
that tumor induction as a result of radiation
injury to one or a fewcells of the body cannot
be excluded. Risk estimates have been made
based on this premise and using linear extrapolation from the data from the A-bomb survivors of Hiroshima and Nagasaki, from certain
groups of patients irradiated therapeutically,
and from groups occupationally exposed. Such
calculations based on these data from irradiat-
ed humanslead to the prediction that addition-
a] exposure of the U. S. population of 5 rem per
380 years could cauze from roughly 3,000 to
15,000 cancer deaths annua!ly, depending on
the assumptions used in the calculations. The
Committee considers the most likely estimate
to be approximately 6,000 cancer deaths annually, an increase of about 2% in the spontaneous cancer death rate which is an increase of
about 0.3% in the overall death rate from a!
causes.
Given the estimates for genetic and somatic
risk, the question arises as to howthis infor-
mation can be used as a basis for radiation.
protection guidance. Logically the guidance or
standards should be related to risk. Whethe:
we regard a risk as acceptable or not depends
on howavoidable it is, and, to the extent not
avoidable, how it compares with the risks of
alternative options and those normally accepted by society.
There is reason to expect that over the next
few decades, the dose commitmentsfor al] manmade sources of radiation except medica!
should not exceed more than a few millirems
average annual dose to the entire U. S. population. The present guides of 170 mrem/yr grew
out of an effort to balance societal needs
against genetic risks. It appears that these
needs can be met with far lower average exposures and lower genetic and somatic risk than
permitted by the current Radiation Protection
Guide. To this extent, the current Guide is unnecessarily high.
The exposures from medical] and dental uses
should be subject to the same rationale. To the
extent that such exposures can be reduced
without impairing benefits, they are also unnecessarilyhigh.
It is not within the scope of this Committee to
propose numerical limits of radiation exposure.
It is apparent that sound decisions require
technical, economic and sociological considerations of a complex nature. However, we can
state some general principles, many of which
are well-recognized and in use, and some of
which may represent a departure from present
practice.
a) No exposureto ionizing radiation should
be permitted without the expectation of a
commensuratebenefit.
b) The public must be protected from radia-
tion but not to the extent that the degree
of protection provided results in the sub-
stitution of a worse hazard for the radia-
tion avoided. Additionally there should
not be attempted the reduction of small
risks even further at the cost of large
sums of money that spent otherwise,
would clearly produce greater benefit.
DOE ARCHIVES