Basic Radiation Information
What is Radiation?
Matter is composed of atoms. Some atoms are unstable. As these atoms change
to become more stable, they give off invisible energy waves or particles
called radiation. There are different types of radiation, some more energetic
than others. One type of radiation, non-ionizing radiation, has enough
energy to move atoms but not enough to alter them chemically. The most
energetic form, known as ionizing radiation, will here on be referred
to simply as radiation. We measure radiation dose in units called rem.
Scientists estimate that the average person in the United States receives
a dose of about 360 millirem of radiation per year. Eighty percent of
that exposure comes from natural sources: radon gas, the human body, outer
space, and rocks and soil. The remaining 20 percent comes from man-made
radiation sources, primarily medical x-rays.
Risks from Exposure to Radiation
Radiation is a carcinogen. In this respect, it is similar to many hazardous
chemicals found in the environment that can cause cancer. It may also
cause other adverse health effects, including genetic defects in the children
of exposed parents or mental retardation in the children of mothers exposed
during pregnancy. However, the risk of developing cancer due to radiation
exposure is much higher than the risk of these other effects. Much of
our knowledge about the risks from radiation is based on studies of over
100,000 survivors of the atomic bombs at Hiroshima and Nagasaki. In these
studies, which have continued over the last 40 years, scientists have
been able to observe the effects of a wide range of radiation doses, including
doses comparable to an average person's lifetime dose from naturally-occurring
background radiation (about 20,000 millirem). We have learned many things
from these studies. The most important are:
The more radiation dose a person receives, the greater the chance of
It is the chance of cancer occurring, not the kind or severity of
cancer, that increases as the radiation dose increases.
Most cancers do not appear until many years after the radiation dose
is received (typically 10 to 40 years).
Current evidence suggests that any exposure to radiation poses some risk,
i.e., there is no level below which we can say an exposure poses no risk.
For the entire dose of radiation we accumulate over a lifetime from natural
background radiation, the risk of developing cancer is estimated to be
about one in one hundred. Based on this estimate, several percent of all
fatal cancers in the U.S. are caused by background radiation. The additional
contribution from all man-made sources of radiation is much smaller. (U.S.
EPA Radiation: Risks and Realities)
Radioactive Contamination and Radiation Exposure
Radioactive contamination and radiation exposure could occur if radioactive
materials are released into the environment as the result of an accident,
an event in nature, or an act of terrorism. Such a release could expose
people and contaminate their surroundings and personal property.
What Radioactive Contamination Is
Radioactive contamination occurs when radioactive material is deposited
on or in an object or a person. Radioactive materials released into the
environment can cause air, water, surfaces, soil, plants, buildings, people,
or animals to become contaminated. A contaminated person has radioactive
materials on or inside their body.
What External Contamination Is
External contamination occurs when radioactive material, in the form of
dust, powder, or liquid, comes into contact with a person's skin, hair,
or clothing. In other words, the contact is external to a person's body.
People who are externally contaminated can become internally contaminated
if radioactive material gets into their bodies.
What Internal Contamination Is
Internal contamination occurs when people swallow or breathe in radioactive
materials, or when radioactive materials enter the body through an open
wound or are absorbed through the skin. Some types of radioactive materials
stay in the body and are deposited in different body organs. Other types
are eliminated from the body in blood, sweat, urine, and feces.
What Radiation Exposure Is
Radioactive materials give off a form of energy that travels in waves
or particles. This energy is called radiation. When a person is exposed
to radiation, the energy penetrates the body. For example, when a person
has an x-ray, he or she is exposed to radiation.
How Contamination Differs From Exposure
A person exposed to radiation is not necessarily contaminated with radioactive
material. A person who has been exposed to radiation has had radioactive
waves or particles penetrate the body, like having an x-ray. For a person
to be contaminated, radioactive material must be on or inside of his or
her body. A contaminated person is exposed to radiation released by the
radioactive material on or inside the body. An uncontaminated person can
be exposed by being too close to radioactive material or a contaminated
person, place, or thing.
How Exposure or Contamination Can Happen
Radioactive materials could be released into the environment in the following
- A nuclear power plant accident
- An atomic bomb explosion
- An accidental release from a medical or industrial device
- Nuclear weapons testing
- An intentional release of radioactive material as an act of terrorism
How Radioactive Contamination Is Spread
People who are externally contaminated with radioactive material can contaminate
other people or surfaces that they touch. For example, people who have
radioactive dust on their clothing may spread the radioactive dust when
they sit in chairs or hug other people. People who are internally contaminated
can expose people near them to radiation from the radioactive material
inside their bodies. The body fluids (blood, sweat, urine) of an internally
contaminated person can contain radioactive materials. Coming in contact
with these body fluids can result in contamination and/or exposure.
How Your Home Could Become Contaminated
People who are externally contaminated can spread the contamination by
touching surfaces, sitting in a chair, or even walking through a house.
Contaminants can easily fall from clothing and contaminate other surfaces.
Homes can also become contaminated with radioactive materials in body
fluids from internally contaminated people. Making sure that others do
not come in contact with body fluids from a contaminated person will help
prevent contamination of other people in the household.
How You Can Limit Contamination
Since radiation cannot be seen, smelled, felt, or tasted, people at the
site of an incident will not know whether radioactive materials were involved.
You can take the following steps to limit your contamination:
- Get out of the immediate area quickly. Go inside
the nearest safe building or to an area to which you are directed by
law enforcement or health officials.
- Remove the outer layer of your clothing. If radioactive
material is on your clothes, getting it away from you will reduce the
external contamination and decrease the risk of internal contamination.
It will also reduce the length of time that you are exposed to radiation.
- If possible, place the clothing in a plastic bag or leave
it in an out-of-the-way area, such as the corner of a room.
Keep people away from it to reduce their exposure to radiation. Keep
cuts and abrasions covered when handling contaminated items to avoid
getting radioactive material in them.
- Wash all of the exposed parts of your body using lots of
soap and lukewarm water to remove contamination. This process
is called decontamination. Try to avoid spreading contamination
to parts of the body that may not be contaminated, such as areas that
- After authorities determine that internal contamination may
have occurred, you may be able to take medication to reduce
the radioactive material in your body.
(From the CDC Radiation Emergency Preparedness and Response)
Here are Some Typical Sources and Amounts of Radiation:
Background Radiation (Millirems
|Building Materials - Living in a Brick House
|Living in a Stone House
|Living in a Wood House
Man-Made Radiation (Millirems
|Dental X-Rays - Bitewing Series
|Coast to Coast Airline Flight
|Living within One Mile of a Nuclear Power Plant