(b) X-ray fluoroscopy for shoe fitting. At one time in the United States,
it was common for a person (particularly a child) to try on a new pair of shoes in a shoe
store and step into a machine which would x-ray the feet showing whether or not the
shoes fit. The machine (the x-ray fluoroscope) has been prohibited in several countries
because it caused unnecessary radiation exposure.
(c) Television sets. A small amount of radiation is released by
television sets. More radiation is released by a color television set than a black-and-
white set. The plastic or glass covering on the sets reduces the radiation dosage
considerably. Additional shielding is necessary for color television sets.
CHARACTERISTICS OF IONIZING/NONIONIZING RADIATION
a. The speed of this type of radiation approaches, or equals, the speed of light.
b. Ionizing radiation travels in straight lines although some radiation scatter is
c. The range of penetration into the human body for ionizing radiation varies.
(1) Alpha particles. An alpha particle does damage for only a short distance
and penetrates the human body less than one-thousandth of a centimeter.
(2) Beta particles. Beta particles can travel a little longer in the air and
penetrate human tissue a little deeper (0.2 inches).
(3) Gamma rays and x-rays. These rays, from natural radiation outside the
body, can penetrate deeply and do the body more injury than either alpha particles or
d. Air can absorb alpha particles, beta particles, and neutrons very well.
Gamma rays are not well-absorbed by air.
a. Effects on Somatic (Body) Cells. Radiation can produce cancer in humans.
Sometimes cells in an area of the body go out of control and duplicate in an unusually
large number. The result is an excess of tissue which is called a growth or tumor. If the
growth is cancerous (malignant), the cells--still out of control--will spread to other parts
of the body, sometimes very quickly. These cancerous cells, lacking a quality called
contact inhibition, can invade and kill healthy tissues. Along with substances in the air
we breathe, the water we drink, and the food we eat, radiation is one of the
environmental factors that can cause cancerous cells. Skin cancer, for example, may
be caused by ultraviolet light from the sun.