5.2 HUMAN SOURCES
The difference between man-made sources of radiation and naturally occurring sources is the place from
which the radiation originates. The following information briefly describes some examples of human-made radiation sources.
Medical radiation sources
X rays are identical to gamma rays; however, they are produced by a different mechanism. X rays
are an ionizing radiation hazard. A typical radiation dose from a chest x ray is about 10 mrem. The
total average dose from medical x rays is 40 mrem in a year. In addition to x rays, radioactive
isotopes are used in medicine for diagnosis and therapy. The total average dose is 14 mrem in a
Examples include TV's, older luminous dial watches, some smoke detectors, and lantern mantles. This
dose is relatively small as compared to other naturally occurring sources of radiation and averages 10
mrem in a year.
Atmospheric testing of nuclear weapons
Another man-made source of radiation includes residual fallout from atmospheric nuclear weapons
testing in the 1950's and early 1960's. Atmospheric testing is now banned by most nations. The
average dose from residual fallout is about 2 mrem in a year.
Industrial uses of radiation include x-ray machines and radioactive sources (radiography) used to test
pipe welds, bore-holes, etc. Most people receive little if any dose from these sources.
As a whole, these sources of natural and human-made radiation are referred to as background.
The average annual radiation dose to a member of the general population from ALL background
sources is about 360 millirem.
AVERAGE ANNUAL DOSE TO THE GENERAL POPULATION
We will discuss specific sources of radiation at TJNAF later in the course.
ANSWERS TO UNIT 5 REVIEW QUESTIONS