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"There is no safe
level of exposure and there is no dose of (ionizing) radiation so
low that the risk of a malignancy is zero" --Dr. Karl
Morgan, the father of Health Physics
WHAT IS RADIATION?
Radiation is energy that
travels in waves. It includes visible light, ultraviolet light,
radio waves and other forms, including particles. Each type of
radiation has different properties. Non-ionizing radiation
can shake or move molecules. Ionizing radiation can break
molecular bonds, causing unpredictable chemical reactions.
Ionizing radiation includes not only energy waves but particles
as well. Humans cannot see, feel, taste, smell or hear ionizing
radiation. Unavoidable exposure to ionizing radiation comes from
cosmic rays and some natural material. Human exposure to natural
radiation is responsible for a certain number of mutations and
cancers. Additional exposure above natural background radiation
is cause for concern since it may result in otherwise preventable
disease.
WHERE DOES IONIZING RADIATION
COME FROM?
Ionizing radiation is
matter or energy that is given off by the nucleus of an unstable
atom in the process of decaying and reaching a stable (ground)
state. This energy is released in the form of subatomic particles
(alpha and beta) or waves (gamma and x rays). Most elements and
their atoms are not radioactive. A few radioactive elements, like
uranium, radium, and thorium, occur in nature.
Humans, through nuclear
power, bomb production and testing, have created and released man-made
radioactive elements (radionuclides) that were previously unknown
in the environment. Through mining and industrial processing naturally
radioactive elements like uranium and thorium have been
released to flow through the natural systems on which life
depends. These substances were, with few exceptions, geologically
isolated from the environment under layers of shale and quartz
before human beings dug them up by the ton and contaminated the
biosphere. Because of poorly conceived and implemented nuclear
technologies, such as atomic energy, bomb production and
reprocessing, we and our descendants are left with a legacy of
radioactive waste with no proven isolation method.
FROM A TO X
Alpha particles are high
energy, large subatomic structures. They can’t travel very
far and can be stopped by a piece of paper or skin. However,
alpha particles hit hard and can do a great deal of damage to the
cells they rip through. Once inhaled, ingested or otherwise taken
inside the body (as through a cut in the skin), they have the
power to tear through cells in organs or blood, releasing their
energy to surrounding tissue and leaving extensive damage in
their wake. A single track of a single alpha particle can deliver
a large dose of radiation to a cell. Plutonium is an alpha
emitter. Other alpha emitters include radon gas, uranium, and
americium.
Beta particles are
electrons. They are a fraction of the size of alpha particles,
can travel farther and are more penetrating. Betas pose a risk
both outside and inside the body, depending on their energy
level. External exposure can result in beta penetration through
the surface to the most sensitive layers of skin. Inhalation or
ingestion of a beta-emitting radionuclide poses the greatest
risk. Externally, a half-inch of Plexiglas or
water shielding can generally stop a beta.
Strontium-90 and tritium are two beta-emitting radionuclides
routinely released from nuclear power reactors during normal
operation. Our bodies often mistake strontium-90 for calcium,
collecting it in our bones that make our new blood cells. Once
there, it increases our risk of bone and blood cancers like
leukemia. Every one of us has strontium-90 in our bodies as a
result of nuclear bomb testing. Tritium is
radioactive hydrogen, which binds where normal hydrogen does.
Hydrogen is the most abundant element on the earth, and is a
component of water, which cushions our genetic material (DNA).
Tritium can bond in this water, irradiating our DNA at very close
range.
Gamma rays are the most
penetrating type of radiation and can be stopped only by thick
lead blocking their path. Cesium-137 is a gamma emitter often
released from nuclear reactors. It mimics potassium, collecting
in muscle. Iodine-131and Iodine-129 are also gamma-emitters
released through bomb testing and at atomic reactors. Radioactive
iodines collect in the thyroid gland emitting both beta and gamma
ionizing radiation to the surrounding tissue.
X-rays are much like gamma
rays except they are most often generated electrically by a
machine (rather than a radionuclide), usually for medical
diagnostic procedures. X-rays also require lead shielding. When
generated by medical equipment, their production does not create
nuclear waste.
HALF-LIVES AND DECAY CHAINS
Different radionuclides
have different half-lives. Half-life is the time it takes
for one-half of a radioactive element to decay the next step
toward stability. Some radionuclides decay to a stable element in
a single step. For others, like uranium, the movement toward
stability may be a long, complex process. Uranium-238 has a
half-life of 4.5 billion years, about the age of the Earth. All
told, it has 17 decay steps before reaching a final, stable form
of lead. Half-lives can range from fractions of seconds
(Polonium-214, .00016 seconds), to days (Iodine-131, 8.04 days)
to billions of years (Uranium-238, above). A radionuclide may
also decay to another radioactive element that has a longer
half-life and is more biologically active than the original
radionuclide. For instance, xenon-135 (9-hour half-life) decays
to cesium-135 with a half-life of 3 million years. Cesium mimics
potassium and collects in muscle in the body. Xenon-135 is
released regularly by nuclear reactors. Hazardous life is
defined as 10-20 times the half-life. This is how long it will
take for a given quantity of the radioactive element to decay to
undetectable levels.
Some radioactive atoms
give off more than one type of radiation. For instance radium,
which humans collect and concentrate from an ore called
pitchblende, gives off gamma and alpha radiation. Shortly after
the Curies (research physicists in France) discovered radium,
when its harmful effects were not known or believed, it was
widely used, especially among the wealthy. Exposure to radium,
ingested in water, painted on watch faces and carried in pockets,
caused many debilitating illnesses and excruciating deaths. Marie
Curie died of aplastic anemia (leukemia) most likely caused from
her exposure to radium through the extraction process she used to
concentrate it. To this day, her notebooks are
dangerously radioactive.
BIOACCUMULATION
With man’s increased
uses of radioactive material, more radionuclides have been and
continue to be released to the environment. Once released, they
can circulate through the biosphere, ending up in drinking water,
vegetables, grass, meat, etc. The higher an animal eats on the
food chain, the higher the concentration of radionuclides. This
is bioaccumulation. The process of bioaccumulating radionuclides
can be especially harmful to humans since many of us eat at the
top of the food chain.
"MADMAN IN A
LIBRARY…"
Ionizing radiation travels
through our living tissue with much more energy than either
natural chemical, or biological functions. This extra energy
tears mercilessly at the very fabric of what makes us
recognizably human—our genetic material. Elderly and people
with immune disorders are more susceptible to ionizing radiation.
Children and the unborn are especially susceptible because of
their rapid and abundant cell division during growth.
Cancers linked to ionizing
radiation exposure include most blood cancers (leukemia,
lymphoma), lung cancer, and many solid tumors of various organs.
Birth defects can include downs syndrome, cleft palate or lip, congenital malformations, spinal
defects, kidney, liver damage and more.
Evidence exists that
radiation is permanently and unpredictably mutating the gene pool
and contributing to its gradual weakening. The New Scientist
quotes a report that calls genetic or chromosomal instabilities
caused by radiation exposure a "plausible mechanism"
for explaining illnesses other than cancer, including
"developmental deficiencies in the fetus, hereditary
disease, accelerated aging and such non-specific effects as loss
of immune competence."
A living being’s
genetic material is the library that houses the instructions for
many important aspects of that being and his/her offspring,
including the ability to defend against diseases. If we allow
ionizing radiation to tamper with our genes, it could cause
irreversible damage, not just to this generation through cancer,
but to future generations through gene mutations and ensuing
disease.
Prepared 8/99 by Cindy Folkers, Nuclear
Information and Resource Service, 1424 16th
Street, NW, #404, Washington, DC 20036. Phone: 202-328-0002. Fax:
202-462-2183. E-mail: nirsnet@nirs.org. Web: www.nirs.org
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