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|  DOE-HDBK-1130-98
Module 2 Biological Effects
Instructor's Notes
However, it should be noted that this is a conservative
assumption made in the absence of more conclusive evidence.
Health effects (primarily cancer) have been observed in
humans only at doses in excess of 10 rem delivered at high
dose rates. Below this dose, estimation of adverse health
effects is speculative. Risk estimates that are used to predict
health effects in exposed individuals or populations are based
on epidemiological studies of well-defined populations (e.g.,
the Japanese survivors of the atomic bombings in 1945 and
medical patients) exposed to relatively high doses delivered at
high dose rates. It is generally accepted that studies have not
demonstrated adverse health effects in individuals exposed to
small doses (less than 10 rem) delivered over a period of
many years.
1.
Risk from exposures to ionizing radiation
a.
No increases in cancer have been observed in
individuals who receive a dose of ionizing radiation at
occupational levels. The possibility of cancer
induction cannot be dismissed even though an
increase in cancers has not been observed. Risk
estimates have been derived from studies of
individuals who have been exposed to high levels of
radiation.
b.
Review: There are many other
can be put into perspective. This can be done by
causes of cancer, not just
comparing it to the normal rate of cancer death in
radiation.
today's society. The current rate of cancer death
among Americans is about 20 percent. Taken from
a personal perspective, each of us has about 20
chances in 100 of dying of cancer. A radiological
worker who receives 25,000 mrem over a working
life increases his/her risk of cancer by 1 percent, or
has about 21 chances in 100 of dying of cancer. A
25,000 mrem dose is a fairly large dose over the
course of a working lifetime. The average annual
dose to DOE workers is less than 100 mrem, which
leads to a working lifetime dose (40 years assumed)
of no more than approximately 4,000 mrem.
32
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