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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


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%


Medical X ray 39 0.39 11%
Nuclear medicine 14 0.14 4%
Consumer products 10 0.1 3%


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
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.


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


ELF/EMF Papers (David Hafemeister - Cal Poly)
Radiation and Risk (UofM)
Health Physics Society Position Statement on Risk from Ionizing Radiation
For more information on specific radiation sources like radon, UV, EMF,etc.
try our Radiation and Radioactive Material Specific Information Section





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