a. It is useful to begin any discussion of radiation sources with an understanding of the exposure from natural sources of radiation. You must realize that you are exposed to natural radiation all the time. That is the radiation that comes from space, the radiation that comes from the crust of the earth, and some radioisotopes that we all have inside our bodies. Actually, there is little we can do to reduce this exposure; it is part of living.

b. On the average, we receive approximately 100 mrems/year from natura background radiation. This dose varies depending on where you live. The point here is that we are all exposed to this radiation naturally.

X-ray Schools | X-ray and Radiation Safety
For Informational Purposes Only - Based On US Army Radiation Safety Training