http://www.epa.gov/
Ionizing Radiation
Higher
frequency ultraviolet radiation begins to have enough energy to break
chemical bonds. X-ray and gamma ray radiation, which are at the upper end of
magnetic radiation have very high frequency --in the range of 100 billion
billion Hertz--and very short wavelengths--1 million millionth of a meter.
Radiation in this range has extremely high energy. It has enough energy to
strip off electrons or, in the case of very high-energy radiation, break up
the nucleus of atoms.
Ionization is the process in which a charged portion of a molecule (usually
an electron) is given enough energy to break away from the atom. This
process results in the formation of two charged particles or ions: the
molecule with a net positive charge, and the free electron with a negative
charge.
Each
ionization releases approximately 33 electron volts (eV) of energy. Material
surrounding the atom absorbs the energy. Compared to other types of
radiation that may be absorbed, ionizing radiation deposits a large amount
of energy into a small area. In fact, the 33 eV from one ionization is more
than enough energy to disrupt the chemical bond between two carbon atoms.
All ionizing radiation is capable, directly or indirectly, of removing
electrons from most molecules.
Health Effects
The
health effects of alpha particles depend heavily upon how exposure takes
place. External exposure (external to the body) is of far less concern than
internal exposure, because alpha particles lack the energy to penetrate the
outer dead layer of skin.
However,
if alpha emitters have been inhaled, ingested (swallowed), or absorbed into
the blood stream, sensitive living tissue can be exposed to alpha radiation.
The resulting biological damage increases the risk of cancer; in particular,
alpha radiation is known to cause lung cancer in humans when alpha emitters
are inhaled.
The
greatest exposures to alpha radiation for average citizens comes from the
inhalation of radon and
its decay products, several of which also emit potent alpha radiation.
Protecting
from
external exposure to alpha radiation is easy, since alpha particles are
unable to penetrate the outer dead layers of skin or clothing. However,
tissue that is not protected by the outer layer of dead cells, such as eyes
or open wounds, must be carefully protected.
The
exposure pathways of concern are inhalation or ingestion of alpha emitters,
which continue to emit alpha particles. Alpha emitting radionuclide's taken
into the body release alpha particles directly to sensitive living tissues.
As their high energy transfers directly to tissue, it causes damage that may
lead to cancer.
The most
significant way people come in contact with alpha emitters is in their home,
school, or place of business. Radon, is a heavy gas and tends to collect in
low-lying areas such as basements. Testing for radon in your home and taking
any corrective action necessary is the most effective way to protect you and
your family from alpha emitters.
americium-241
plutonium-236
uranium-238
thorium-232
radium-226
radon-222
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