Radiation and Us
Radiation all around us
Humans have been exposed to radiation from natural sources since the dawn of
time. The sources include the ground we walk on, the air we breath, the food we
eat and the solar system on the whole. Everything in our world contains small
amounts of radioactive atoms like Potassium 40, Radium 226 and Radon 222. These
are either left over from the creation of the world (like Uranium and Radium) or
made by interactions with cosmic radiation (like Carbon 14 and Tritium). The
Earth is constantly receiving cosmic radiation from outer space. These natural
sources of radiation make up approximately 82 percent of the average annual dose
to the US public.
The following was developed by the National Council on Radiation Protection
and Measurement (NCRP 93) and is a breakdown of the sources of radiation for the
population of the United States. These numbers are averages and were obtained by
estimating the total dose for the US, and dividing by the number of people in
the US.
Annual Effective Dose Equivalent
| SOURCE |
DOSE
(mrem/yr) |
DOSE
(mSv/yr) |
PERCENT OF TOTAL |
|
Natural |
|
|
|
| Radon |
200 |
2.0 |
55% |
| Cosmic |
27 |
0.27 |
8% |
| Terrestrial |
28 |
0.28 |
8% |
| Internal |
39 |
0.39 |
11% |
| Total Natural |
300 |
3 |
82% |
|
Artificial |
|
|
|
| Medical X ray |
39 |
0.39 |
11% |
| Nuclear medicine |
14 |
0.14 |
4% |
| Consumer products |
10 |
0.1 |
3% |
|
Other |
|
|
|
| Occupational |
0.9 |
<0.01 |
<0.3 |
| Nuclear Fuel Cycle |
<1 |
<0.01 |
<0.03 |
| Fallout |
<1 |
<0.01 |
<0.03 |
| Miscellaneous |
<1 |
<0.01 |
<0.03 |
| Total Artificial |
63 |
0.63 |
18% |
Total Artificial and
Natural |
360 |
3.6 |
100% |
Or, this can perhaps be more easily
seen with a
graph (6K)
Further more, we also have a list of
doses from
other sources for comparison.
Natural Radiation
Everyone by now has probably heard of radon. Radon comes from the decay
(change) of Uranium, a natural element. Uranium decays through a long chain of
radionuclides that includes radon. Radon is a noble gas, not chemically active
so it migrates through porous materials like the ground and your house's
foundation. The radon itself has a small chance of decay as you breath it in and
out. Most of our actual dose comes from the decay products of radon, sometimes
called radon daughters or radon progeny. These radon progeny are particles not
gases, and can be deposited in your lungs as you breath. There they have some
chance of decaying before your body can get rid of them, resulting in a
radioactive dose.
There are several other naturally occurring radioactive nuclides. Most
notable are Carbon-14 (C-14) and Potassium 40 (K-40). They are made by cosmic
ray interactions and eventually make there way into our food chain. Once
ingested, they can decay and give us an internal dose. All living organic
material has a constant ratio of carbon 14 to non-radioactive carbon 12. Once
dead, the organic material stops taking in carbon. Therefore, by measuring that
ratio of C-14 to C-12 found in organic archeological items, the appropriate time
since death can be determined. This is what is known as carbon dating.
For more on Natural Radioactivity, see the
Radioactivity
in Nature page.
Here's just a sampling of radioactive materials...and the many ways they
improve lives.
Radiation in the home
There are some small sources of radiation in the home. Your television set
accelerates electrons to make the picture on the screen, and produces a few low
energy x-rays. Smoke detectors contain small sources in them. These sources emit
radiation that are easily stopped even by smoke, and that way detect the
presence of smoke. The sources of radiation around the home, not counting
natural sources like radon, tend to make up a small fraction of the background
dose.
Radiation in the work place
Persons in many occupations encounter radiation above normal background as a
natural part of their jobs. Some of these occupations include doctors, nurses,
radiographers, astronauts, dental hygienists, researchers, pharmacists, welders,
airplane and jet crews.. The doses received can be up to several rem of exposure
over the course of a year.
Medical uses of radiation
Medical uses of radiation are roughly broken into therapy and diagnosis.
Therapy is primarily used for tumor killing of cancer, but in the past has been
used for other treatments. Most of the dose is received in a small area of the
body. Diagnosis runs from fairly routine x rays to injections of radioactive
material and imaging. These doses can be several hundred mrem for diagnosis and
up to several hundred rem locally for treatments. The physician who prescribes
radiation treatments and diagnosis weighs the risk of the radiation with the
benefit of the treatment.
Who is in charge
Ultimately, you are. All of the sources of radiation, other than natural, are
regulated by laws passed by Congress. Like any other law, you have your right to
voice your views and opinions about it. The regulations that control the use of
radioactivity in our country are based on recommendations of science
organizations like the International Commission on Radiological Protection (ICRP),
the National Council on Radiation Protection (NCRP), the International Atomic
Energy Agency (IAEA), the United Nations (UN), and the Health Physics Society (HPS).
Governing bodies like the Environmental Protection Agency (EPA), the Nuclear
Regulatory Commission (NRC), the Department of Energy (DOE), and the Food and
Drug Administration (FDA) review these recommendations and propose the
regulations that industry and government must follow. These are then passed by
Congress, if found to be acceptable, and published in the Code of Federal
Regulations (CFRs).
To see some of the regulations, look at our
Law, Orders and
Directives page or our
Federal agency
page.
Additional Information
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