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|  DOE-HDBK-1130-98
Module 2 Biological Effects
Instructor's Notes
b.
Sources in earth's crust (terrestrial) (total
average dose ~ 28 mrem/yr)
There are natural sources of radiation in the
ground (i.e., rocks and soil).
1)
Some of the contributors to terrestrial
sources are the natural radioactive elements
radium, uranium, and thorium.
2)
Many areas have elevated levels of
terrestrial radiation due to increased
concentrations of uranium or thorium in the
soil.
c.
Internal (total average dose ~40 mrem/yr)
1)
The food we eat and the water we
drink contain trace amounts of natural
2)
These naturally occurring radioactive
materials deposit in our bodies and
cause internal exposure to radiation.
3)
Some naturally occurring radioactive
isotopes include Sodium-24 (Na-24),
Carbon-14 (C-14), Argon-41 (Ar-41),
and Potassium-40 (K-40). Most of our
internal exposure comes from K-40.
d.
Radon (total average dose ~ 200 mrem/yr)
1)
Radon comes from the radioactive decay of
uranium, which is naturally present in the
soil.
2)
Radon is a gas. It can travel through the
soil and enter through building foundation
cracks. The greatest concentrations of
indoor radon are found in basements.
3)
Radon emits alpha radiation. It presents a
Review characteristics of
hazard only when taken into the body (e.g.,
alpha radiation.
when inhaled).
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