formation, the relationship of these morphologic changes to potential leukemogenesis or
other abnormalities which might occur later
remains highly speculative.*7 “*
Other somatic effects. Opacities of the
optic lens occur after acute exposure of the
lens to doses greater than 200 rads of mixed
gamma and neutron radiation,’® 7 although
the minimum effective x-ray dose for the
production of clinically significant cataract
the ABCC investigated 4,781 births to related parents with varying degrees of radiation exposure®! and reported: “No demonstrable, consistent effect of parental exposure
on the frequency of malformed infants or
perinatal deaths was found.”
The massive data from the ABCC survey
of pregnancy termination in nonrelated parents®® have been reanalyzed independently,
and, on the basis of this separate analysis, a
significant total genetic effect has been reinterpretations of the reanalysis have been
seriously questioned by Neel and Schull.*’
rays.'® The sensitivity of lenses to radiation
than man have shown that the frequency of
local gonadal doses of 500 rads or higher."®
lowest doses investigated, and that the majority of induced hereditary changes had
detrimental consequences.’* Although direct
to be more cataractogenic than x- or gamma
seems to be greatest in infants under 1 year
of age.'* Prolonged temporary or permanent
sterility has been reported following single
HEREDITARY EFFECTS—
HIGH DOSE
In the studies of atomic bomb survivors
at Hiroshima and Nagasaki by the ABCC,
**) ©% 81 it was concluded that the data could
demonstrate “no significant and consistent
effect of parental radiation exposure on the
numberof infants with major defects, among
the 76,626 children examined” and failed
“to reveal an increase in stillbirths or infant
deaths clearly attributable to parental irradiation.” The Japanese study, however, has
indicated a change in sex ratio among offspring of irradiated parents. Such a shift
would be consistent with the occurrence of
sex-linked mutations affecting prenatal survival.** Schull** has examined the genetic
interpretation of the data, emphasizing the
reality of the effect but indicating that a
number of genetic alternatives may account
for the change. A slight increase, however, in
the number of miscarriages, stillbirths, and
neonatal deaths has been reported in the
Marshallese women exposed to fallout radia-
tion.8*
Based on the assumption that children of
consanguineous Marriages, owing to their
increased homozygosity, are “a more sensitive
index of radiation induced genetic damage,”
,
F
‘
ported.®* 8° However, the methodology and
In chronic exposures, neutrons are considered
has been estimated to be 600 to 1,000 rads.17
ET Sie a= RTOET
these chromosomal aberrations has not been
established; in the absence of sufficient in-
ra
October 1965.
Sutow and Conard
Experimental studies in organisms other
mutations was dose dependent, even at the
information is lacking, it appears reasonably
certain that similar effects occur in the human being.*® Thus, known exposure to high
doses of ionizing radiation requires the disquieting acceptance of genetic hazards, the
true magnitude of which may be assessed
only with the perspective of time stretching
over generations.
SOMATIC AND GENETIC EFFECTS
OF LOW-LEVEL RADIATION
The term “low-level” radiation, regardless of source, requires definition. The United
Nations Scientific Committee on the Effects
of
Atomic
Radiation
(UNSCEAR)
has
agreed that doses of less than 50 rad shortterm exposure and 100 to 1,000 mrad cumulative weekly doses should be considered as
“low.”*? Two other frames of reference will
be useful in this discussion, one being the
amount of radiation from natural sources to
which man is constantly exposed and the
other being the levels accepted by several
advisory and regulatory bodies as protection
standards for the general population.
According to UNSCEAR calculations of
dose rates from natural radiation sources,®*°°
cosmic rays and terrestrial sources each de- liver about 50 mrem per year to the gonads,
bones, and blood-forming cells. The inges-
we dere Pee AY
G62