b. Genetic Mutations in Future Generations. Radiation can have two major
genetic effects on humans. First, a gene mutation may occur (a permanent,
transmissible change in the gene function). Many of these gene mutations are
recessive and only show up when two people with the same recessive gene pair.
Second, radiation can result in chromosome breakage. Chromosome breakage involves
multiple genes and may lead to fetal death. Chromosome breakage does not have a
long-range hidden hazard. When radiation exposure takes place over an extended
period, rather than all at one time, fewer gene mutations occur. Based on current
knowledge, gene mutations are not regarded by scientists as a serious problem.
c. Effects on Developing Embryo or Fetus. The damage done by radiation
depends on the gestation stage at which the radiation occurs.
(1) Preimplantation period. (Conception through the 9th day.) During this
period, the fertilized egg is embedded in the wall of the uterus where it divides rapidly.
Radiation during this period can cause the death of the embryo. However, if the embryo
survives, it will develop normally.
(2) Organogenesis period. (From the 10th to the 49th day.) The
individualized, specialized organs begin to form during this period. Radiation at this
time can result in temporary growth- retardation. The principal and more serious effects
are gross abnormalities and structural deformities. There may be a cleft palate, stunted
arms or legs, or an abnormally developed brain. These abnormalities are
indistinguishable from the same abnormalities that occur in about four percent of all
(3) Fetal period. (After the 49th day.) If the radiation has occurred early in
the fetal period, there is growth-retardation which is permanent and lasts into adulthood.
Additionally, the diameter of the head is smaller and there is mental retardation.
d. Acute Total Body Irradiation. There is a characteristic pattern of injury if the
person's entire body is exposed to penetrating ionizing radiation. Effects of radiation on
the body can be categorized according to rems (the measure of quantity of radiation)
the person is exposed to.
(1) Cases of people receiving 10,000 rem in accidents. The result was
usually cerebrovascular death. Within an hour after exposure, a person experiences
vomiting and diarrhea. Next, there are mental changes and fall of blood pressure, then
convulsions and unconsciousness. Within one to three days, the person will die from
(2) Cases of people receiving 2,000 rem. Gastrointestinal failure was the
cause of death. Within a few hours of exposure, the person suffers nausea, vomiting,
and diarrhea--all of which become progressively worse. Then, there is fever, loss of
fluids, and loss of soluble salts. Finally, gross infections lead to death.