Posted by Vishva News Reporter on July 27, 2007


Is it true that people are
slightly radioactive?


Boston Globe: July 9, 2007: Dr. Knowledge

People are indeed a little bit radioactive, but this isn't something you can do anything about, so it's also something you shouldn't worry about.

Radioactivity is the name for processes whereby an atomic nucleus, which is made of protons and neutrons, breaks apart, emitting energetic particles. These particles can damage cells and cause their death, or change their genes causing mutations or cancer.

In your body, most of the radioactivity comes from the decay of atoms of potassium-40. (see PVAF FOOTNOTE AT THE END OF RIGHT COLUMN FOR EXPLANTION)

Most potassium is potassium-39 and has 19 protons in its nucleus accompanied by 20 neutrons. A very small fraction, about 1.2 percent, has an extra neutron and is called potassium-40.

On average, if you start off with some potassium-40, it takes about 1.3 billion years for half of it to decay, so it's not really very radioactive and in any case you haven't got much in your body.



Ingestion of naturally occurring radionuclides in food (such as potassium-40 in bananas) 40 millirem/year. People  are  radioactive as carbon-14 and potassium-40 are naturally present in human-beings.

Potassium-40 contributes about the same dose that you get from cosmic rays from space that make it through the Earth's atmosphere to sea level. Most of the radiation doesn't make it out of your body, so there's no reason to avoid crowds or worry about how much you might be affecting the people around you. Your dose from the environment can be much, much higher depending on where you live.

Where does this potassium-40 come from?

Well, according to current theory, it comes from supernovas, where it's made in a phenomenal explosion when a star dies. It, as well as all sorts of other elements, got to Earth from many such explosions. A lot of your body is literally stardust.

You may find it interesting that there is a controversial idea called hormesis that holds that some stresses to organisms actually help them to be healthier, and that some radioactivity may be good for you.

I know a nuclear physicist who is close to 80 and looks and behaves like a 40-year-old and he says (perhaps with tongue in cheek) that his constant exposure to radioactivity is the reason.

(Dr. Knowledge is written by physicists Stephen Reucroft and John Swain, both of Northeastern University. E-mail questions to or write Dr. Knowledge, c/o The Boston Globe, PO Box 55819, Boston, MA 02205-5819. © Copyright 2007 Globe Newspaper Company.)



Gamma ray spectroscopy is used to detect the minute amount of radioactive potassium-40 present in the human body. Using a NaI(Tl) scintillation detector in conjunction with a multichannel pulse-height analyzer (PHA), 1.46 MeV gammas originating from the human body are detected. The source of these gammas is K-40 which has a half-life of 1.26 billion years, and is the main source of radioactivity inside the body. The second most active radionuclide in the body, carbon-14 (5,730 yr half-life), can not be detected with this apparatus because it is a beta emitter.

Small traces of many naturally occurring radioactive materials are present in the human body. These come mainly from naturally radioactive isotopes present in the food we eat and in the air we breathe. Smoking tobacco gives your body the largest single does of radiation of 280 millirem/year compared to a total of 360 millirem/year of radiation you recieve from your environment.

These isotopes include tritium (H-3), carbon-14 (C-14), and potassium-40 (K-40). For more information on Natural Radioactivity in the Body click

For more knowledge on RADIOACTIVE HOMOIS mentioned in the above news story and its pros and cons on your health please click on the next line to learn from Wikipedia......



Radiation hormesis
From Wikipedia, the free encyclopedia

Radiation hormesis is the theory that ionizing radiation is benign at low levels of exposure, and that doses at the level of natural background radiation can be beneficial. This is in contrast to the linear no threshold model which posits that the negative health effects of ionizing radiation are proportional to the dose. The scientific consensus is not to accept radiation hormesis, despite a few papers to the contrary. The disagreement arises partly because very low doses of radiation have relatively small impacts on individual health outcomes. It is therefore difficult to detect the 'signal' of decreased or increased morbidity and mortality due to low-level radiation exposure in the 'noise' of other effects.

Radiation hormesis has been rejected by both the United States National Research Council (part of the National Academy of Sciences)[1] and the National Council on Radiation Protection and Measurements (a body commissioned by the U.S. Congress).[2] In addition, the United Nations Scientific Committee on the Effects of Ionizing Radiation (UNSCEAR) wrote in its most recent report [3]

Until the [...] uncertainties on low-dose response are resolved, the Committee believes that an increase in the risk of tumour induction proportionate to the radiation dose is consistent with developing knowledge and that it remains, accordingly, the most scientifically defensible approximation of low-dose response. However, a strictly linear dose response should not be expected in all circumstances.



[edit] Rationale

The theory is explained by the hypothesis that genes that repair damage due to radiation are activated and reduce damage from other causes, which would otherwise be imperfectly repaired. There is some evidence that radiation levels of 100 mSv/year may actually be positive or at least neutral to health. Indeed there have been claims that humans live in a subclinical deficiency of ionising radiation.[4]

[edit] Evidence for and against

The neutrality of this section is disputed.
Please see the discussion on the talk page.

[edit] Evidence for

One claim that many studies have focused on is that pre-exposure to low levels of radiation will protect one from a future dose including the following:

  • A study has suggested that pre-exposure to radiation exerts a protective effect upon cells.[5]
  • One study found that a 200 mGy X-ray dose protects mice against both further X-ray exposure and ozone gas.[6]
  • One study found that preexposure to radiation (50 to 100 mGy for four hours) results in a small reduction of the ability of an 8 Gy dose to damage DNA in intact cells due to a shift in the cell cycle.[7]
  • One study found that moderate internal exposure to plutonium results in a reduction of the risk of cancer.[8]
  • An article in the "Townsend Letter: The Examiner of Alternative Medicine" suggested that a small dose of radiation may be beneficial.[9]

However, none showed this benefit to last for more than 24 hours, making the usefulness questionable.

Another question is the effect of prolonged exposure to radiation on one's health. The vast preponderance of studies have upheld the linear no threshold theory, but epidemiological studies are very difficult, as an example, people with longer life-spans are more likely to get cancer, so those who are occupationally exposed have better health on average because they had a job--they are thus more likely to get cancer regardless of their exposure. As another example:

  • Ramsar has naturally very high radiation (with an observed maximum of 260 mSv/year) due to its geology [10] but is found to have no increased cancer risk.[citation needed]

But the above example could be due to a lower economic status of the occupants of Ramsar.

[edit] Evidence against

  • Pilots are more prone to brain, rectal and prostate cancers whilst flight crews are twice as susceptible to breast cancer, but are healthier overall than the general public (possibly because they are healthier when selected for the job due to health screening).[11] However there is a contrary suggestion and evidence that breast cancer in flight crews may be caused by jet lag.[12]

[edit] Rejecting radiation hormesis

The notion of radiation hormesis has been rejected by the National Research Council's (part of the National Academy of Sciences) 16 year long study on the Biological Effects of Ionizing Radiation. "The scientific research base shows that there is no threshold of exposure below which low levels of ionizing radiation can be demonstrated to be harmless or beneficial. The health risks – particularly the development of solid cancers in organs – rise proportionally with exposure" says Richard R. Monson, associate dean for professional education and professor of epidemiology, Harvard School of Public Health, Boston [4]. See the National Acadamies Press book Health Risks from Exposure to Low Levels of Ionizing Radiation: BEIR VII Phase 2.

The possibility that low doses of radiation may have beneficial effects (a phenomenon often referred to as “hormesis”) has been the subject of considerable debate. Evidence for hormetic effects was reviewed, with emphasis on material published since the 1990 BEIR V study on the health effects of exposure to low levels of ionizing radiation. Although examples of apparent stimulatory or protective effects can be found in cellular and animal biology, the preponderance of available experimental information does not support the contention that low levels of ionizing radiation have a beneficial effect. The mechanism of any such possible effect remains obscure. At this time, the assumption that any stimulatory hormetic effects from low doses of ionizing radiation will have a significant health benefit to humans that exceeds potential detrimental effects from radiation exposure at the same dose is unwarranted [5].
In chronic low-dose experiments with dogs (75 mGy/d for the duration of life), vital hematopoietic progenitors showed increased radioresistance along with renewed proliferative capacity (Seed and Kaspar 1992). Under the same conditions, a subset of animals showed an increased repair capacity as judged by the unscheduled DNA synthesis assay (Seed and Meyers 1993). Although one might interpret these observations as an adaptive effect at the cellular level, the exposed animal population experienced a high incidence of myeloid leukemia and related myeloproliferative disorders. The authors concluded that “the acquisition of radioresistance and associated repair functions under the strong selective and mutagenic pressure of chronic radiation is tied temporally and causally to leukemogenic transformation by the radiation exposure” (Seed and Kaspar 1992) [6]. See also Hormesis under "Non-acceptance".

[edit] Cadmium poisoning as a model

It is known that many toxic metals can induce oxidative stress in tissue which may result in free radical induced damage. Also it is known that prior exposure to a small dose of cadmium can mitigate the effects of a second larger dose, this suggests that the first lower dose of the poison stimulates the DNA repair processes in the exposed tissue. [13][14][15][16]

[edit] See also

[edit] External links

[edit] References

  1. ^ Health Risks from Exposure to Low Levels of Ionizing Radiation: BEIR VII Phase 2
  2. ^
  3. ^ UNSCEAR 2000 REPORT Vol. II: Sources and Effects of Ionizing Radiation: Annex G: Biological effects at low radiation doses. page 160, paragraph 541. Available online at [1].
  4. ^ Luckey T (1999). "Nurture with ionizing radiation: a provocative hypothesis.". Nutr Cancer 34 (1): 1-11. PMID 10453435. 
  5. ^ Azzam, E. I.: Radiation Research, 1994, 138(1), S28-S31
  6. ^ Miyachi, Y.: The British Journal of Radiology, 2000, 73, 298-304
  7. ^ Cramers, P.; Atanasova, P.; Vrolijk, H.; Darroudi, F.; van Zeeland, A. A.; Huiskamp, R.; Mullenders, L. H.; Kleinjans, J.C.: [2])
  8. ^ Kendall, G.M. et al.: Mortality and occupational exposure to radiation; First analysis of the National Registry for Radiation Workers. British Medical Journal, 1992; 304: 220.
  9. ^ [3]
  10. ^
  11. ^
  12. ^
  13. ^ Wahba, Z. Z.; Hernandez, L.; Issaq, H. J.; Waalkes, M. P. (1990): Involvement of sulfhydryl metabolism in tolerance to cadmium in testicular cells. Toxicology and Applied Pharmacology, 104:157-166.
  14. ^ Waalkes, M. P.; Perantoni, A. (1986): Isolation of a novel metal-binding protein from rat testes: characterization and distinction from metallothionein. Journal of Biological Chemistry, 261:13079-13103.
  15. ^ Waalkes, M. P.; Rehm, S.; Riggs, C.W.; et al. (1988): Cadmium carcinogenesis in male Wistar (Crl:(WI)BR) rats: dose-response analysis of tumor induction in the prostate and testes, and at the injection site. Cancer Research, 48:4656-4663.
  16. ^ Rugstad, H. E.; Norseth, T. (1975): Cadmium resistance and content of cadmium-binding protein in cultured human cells. Nature, 257:136-137.


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