Module 2 Biological Effects
1) Some of the contributors to terrestrial sources are the
natural radioactive elements radium, uranium, and
2) Many areas have elevated levels of terrestrial radiation
due to increased concentrations of uranium or thorium in
c. Internal (total average dose ~40 mrem/yr)
1) The food we eat and the water we drink contain trace
amounts of natural radioactive materials.
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.
Radon (total average dose ~ 200 mrem/yr)
Radon comes from the radioactive decay of uranium,
which is naturally present in the soil.
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 hazard only
Review characteristics of
when taken into the body (e.g., when inhaled).
E01 Identify the major
The difference between manmade sources of radiation
sources of natural
and naturally occurring sources is the origin of the
background and manmade
source, i.e., where the radiation is either produced or
enhanced by human activities.
The top sources of manmade radiation exposures are: