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Hormesis: Is some Radiation good for you?

  1. Dec 20, 2006 #1

    Andrew Mason

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    I have always encouraged my kids to play in the dirt to build up their immune systems (all four have had remarkably few health problems in 13-24 years). But I never really thought it would be a good idea for them to play around in a nuclear waste dump. Apparently, there may be a health benefit of exposure to some radiation. This phenomenon is recognized scientifically, apparently, and has a name: "hormesis", which is latin for "that which does not kill you makes you stronger".

    See, for example:

    RADIATION HORMESIS Biopositive Effect of Radiations, T.D. Luckey

    Is Radiation Good For You, W. Hively, Discover December 2002
    Afraid of Radiation? Low Doses are Good for You, by Donald W. Miller, Jr., MD
    An Introduction to Radiation Hormesis, S. M. Javad Mortazavi

    Underexposed. What If Radiation Is Actually Good for You? by Ed Hiserodt

    Low Level Radioactivity and Cancer, Myth and Reality; by Robert Holloway

    Some, apparently have a different approach to latin translation, and think it means "bunk". For example, there is Dr. Helen Caldicott who wrote this article in 1997, this one in 2005 and this article in June of this year. She says that one pound of plutonium dispersed in the atmosphere could give everyone in the world cancer (no reference). She remarks (again, without reference to the source) that "In Berarus, near Chernobyl, over 2,000 children since the reactor melted down in 1989 have had their thyroids removed because of cancer, a situation unheard of in medical history."

    Joy Mitchell of the Australian Broadcasting Corp. in this article on radiation standards, supports Caldicott (without citing sources). This was part of a couple of shows on this subject in 1997.: part I and Part II

    Dr Caldicott has many followers, it appears. Consider this reaction to hormesis from Russell Hoffman, Concerned Citizen
    Carlsbad, CA


    So from all this I gather that:

    1. ionizing radiation can destroy cells and that can be bad, as it can lead to loss of tissue and cause loss of biological function leading to cancer or death.

    2. ionizing radiation's biological effects depend on the dose. While radiation in large doses causes damage, small doses may not. But no one knows what these doses are.

    3. One cannot simply extrapolate on the basis of a constant ratio of damage to dose. There is very little hard data on what is and what is not a damaging dose and there is very little hard data on the long term damage that can be caused by high radiation exposure.

    4. There is radiation everywhere: cosmic rays and radioactive elements in the earth, water and air. Humans have adapted to that radiation. Some radioactive elements are in our bodies by our bodies: eg. potassium 40, carbon 14, uranium 238 and 235. Some are required by our bodies:eg. potassium 40, ultra-violet light. No body seems to know how our bodies use, need or adapt to radiation.

    5. Cells seem to be able to naturally repair the damage caused by low levels of radiation. There is some evidence to suggest that low levels of radiation stimulate the cellular mechanisms which repair damage and that this has some beneficial effect, not yet well understood, in causing cells to prevent certain cancers.

    As far as I can tell, biological effects of radiation are not well understood and there are strong voices on both sides that like to yell at each other and make claims that are not well supported by scientific data.

    I would be interested in knowing how wrong or right the above statement is.

    AM
     
    Last edited: Dec 20, 2006
  2. jcsd
  3. Dec 20, 2006 #2
    Biological effects of radiation are not well understood or easily predictable at low doses (at the diagnostic imaging or natural background levels), either from intermittent or chronic exposures. At higher doses the effects are fairly well understood. There is a considerable amount of data when it comes to high radiation exposures. Just about everything people think they know about risks of low dose radiation exposure comes from extrapolating the high dose data to the low dose region.

    The HPS (Health Physics Society) has a lot of information on their website regarding radiation exposures. If you're interested, the BEIR V and BEIR VII reports have a great deal of information on the effects of low dose radiation exposure. Both can be read online for free.

    Personally I think Caldicott and the like are all quacks. They fall into the camp of 'All radiation, no matter how small the exposure, is bad'. If that really were the case, life would never have developed on this planet.
     
  4. Dec 21, 2006 #3

    Astronuc

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    One would have to quantify 'some' radiation.

    Background radiation, IIRC, is on the order of picocuries, which would be less than 1 count (event) per tens of second.

    This might be useful to the discussion.
    http://hps.org/publicinformation/ate/cat10.html

    and
    http://www.rerf.or.jp/eigo/glossary/backgrou.htm

    I was a grad student in nuclear engineering. The offices where I worked had radiation monitors near the entrances in order to survey the general background. They had audio and well as scale indicators, and one could hear an occasional click which meant a stray particle.

    The effect of radiation is stochastic, and below a certain level (threshold) very little will happen, i.e. there is not adverse effect. Cells naturally age and die, and are replaced, and there are mechanisms to repair cells with some damage. Radiation effects must be determined with good epidemiological studies.

    On the other hand, there is no minimum recommended daily allowance of radiation, and I don't imagine any responsible individual (or organization) would recommend one.

    In the nuclear industry, we keep it "As low as reasonably achievable" (ALARA), and actually as low as possible.
     
  5. Dec 21, 2006 #4

    jim mcnamara

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    In short the answer is no.

    The "Hormesis" you are referring to is developing resistance to fungi and pathogens by exposure to a non-virile variety of a pathogen, which may convey immunity to the virile ones. This happens frequently by working with domestic animals e.g., cowpox and smallpox. Or polio from playing in mud puddles - See Hans Zinnser 'Rats, Lice, and History'. Or the idea of the "bored immune system".

    It also refers to things like the fact that plague fleas do not like the smell of horses, so stable workers steeped in horse manure and horse dander seemed to be immune to the black plague in the 1600's England.

    Exposure to radiation just damages or kills cells. You cannot have your immune system kick in and become resistant to alpha particles. Immunity works on a moleular level, not a sub-atomic one.
     
  6. Dec 21, 2006 #5

    Andrew Mason

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    Assuming that we carry around about 500 micrograms of uranium (about 2 micromoles or about 10^18 atoms), uranium (half life: 4.5 billion years) in our bodies provides about one decay per second. Then we carry around all that carbon 14 which has a half life of about 6000 years.

    Our own bodies produce about 7,000 nuclear decay events per second (7000 becquerels), apparently. see this chart.

    Not at this point, I agree. But it may turn out that there is such a level.

    Apparently, the radiation from living near a nuclear power plant is orders of magnitude smaller than the radiation one receives from flying in an airplane for 1000 km (due to increased cosmic radiation).

    AM
     
  7. Dec 21, 2006 #6

    Andrew Mason

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    It has to do with DNA repair machinery within the cell, not immunity (which is a system of cells attacking other cells). Your view would seem to be at odds with the remarkable phenomenon documented in this article:
    AM
     
  8. Dec 21, 2006 #7
    Your observations are indeed correct for the most part, with imabug's comments taken to heart. Any decent self-respecting health physicist (we're the ones who actually study this kind of thing) would present a person with the evidence for both and let the person make up their own minds. Most health physicists believe that hormesis is a valid mechanism since most of the evidence supports it rather than contradicts it. The problem is that its mechanisms aren't understood well enough to make a full blown theory.
    As for Dr. Caldicott (a medical doctor, not a health physicist), here's a brief analysis of some of the most recent article you provided (and yes, her lack of references is severaly lacking).

    If cellular repair mechanisms work, this is patently false. It is only true if there is lasting damage that is passed on to daughter cells and subsequent generations of cells.

    There is no documented case of genetic effects in humans. Not one! Additionally, she knows nothing of risk. Radiation doesn't "build up" over a person's lifetime. Once the cellular reparir mechanisms repair the damage, it's as if the damage never happened. Each dose merely exposes a person to the risk again. It doesn't add to the risk

    Again, patently false.
    Maybe in other countries (can't really find all the regulations for all countries that employ nuclear power). It the US, there's a very small limit to the dose a member of the public can receive due to all licensed activites.

    Again, patently wrong. Nothing causes cancer. It only increases risk for cancer. Also, (assuming she means Pu-239), the specific activity is 61.5 mCi/g, so she's talking about 61.5 nanocuries. The ALI for Pu-239 is 800 nanocuries for ingestion and 6 nanocuries for inhalation, so if she's referring to airborne plutonium, she is at least right (that it increases risk) in that regard.

    All power plants on some way are toxic to the environment. Nuclear creates waste which is gone (from decay) after time. Solar power creates toxic cadmium and other chemicals (from the manufacture of solar cells) that never go away. http://www.nrel.gov/ncpv/thin_film/docs/summary_esh_from_bnl_all_techs_draft.doc Wind energy is extremely expensive at startup, but overall is pretty clean (other than the initial manufacture of the blades and turbines). Coal is the dirtiest by far, polluting both land, sea and sky both during construction and operation.
    So, basically, Dr. Caldicott is only presenting and misrepresenting some of the facts in support of her agenda that nuclear power never become an option. When it comes right down to it, all power generation has its negatives.
     
  9. Dec 21, 2006 #8

    Monique

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  10. Dec 21, 2006 #9

    jim mcnamara

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    Well.

    Zapponi GA, Marcello I.,
    Ann N Y Acad Sci. 2006 Sep;1076:839-57.

    Analyzes data from other studies - and the abstract indicates that :
    <snip> Therefore, the hormesis theory-based criticism of current radiation protection criteria, assumed to be excessively conservative, is not justified.<snip>

    In other words, radiation hormesis hypothesis reported by some other studies was not confirmed. Kinda what both Astronuc and I were trying to say.
     
  11. Dec 21, 2006 #10

    Andrew Mason

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    Thanks very much for the references to the very helpful HPS site and the BEIR V and VII reports. I skimmed parts of both reports. While they contain alot of information, the conclusions are rather, well.. inconclusive. The recent report recommends further research on the hormetic effects, though.
    I will reserve judgment on Caldicott for the time being. She has had a considerable impact on regulators - perhaps because of the lack of good scientific information. Always better to be conservative on such things where the risk to human life is unclear. There is a problem with her tone and language, however, which makes rational exchanges with her and her supporters more difficult.

    AM
     
  12. Dec 21, 2006 #11

    Andrew Mason

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    Then again, there is this article published last month (abstract not yet available) whose title would suggest that Hormesis is alive and well: Environ Sci Technol. 2006 Nov 1;40(21):6525-6, Hormesis gets massive data support; Rebecca Renner

    But your point is well taken. From the public health perspective, there is insufficient evidence to justify increasing the safety levels for radiation. As I have said, I agree with that.

    AM
     
  13. Dec 21, 2006 #12
    This is exactly the basis regulators use when formulating regulatory limits for doses to occupational workers and members of the public (well, in realtiy they pretty much go by ICRP recommendations). The linear no-threshold model of radiation risk assumes that any radiation dose is harmful. However, as Astronuc pointed out, it uses the concept of ALARA. It is reasonable to set limits of doses rather than not allow any doses to members of the public. Otherwise, if you regulate that any radiation dose (other than natural) is harmful, you have to eliminate the following:
    All nuclear medicine procedures - pray you don't get cancer, since radiotherapy is a great benefit in eliminating cancers.
    Almost all power generation plants. Coal fired plants throw tons of uranium (a trace element in coal) and other radioactive elements into the atmosphere.
    Say goodbye to all those salt substitutes. Potassium iodide has about .01% radioactive potassium-40, so those who need salt substitutes are out of luck.
    No more xrays for anyone.

    My point is, that regulations (in the US at least) are written so that the relative increase in risk of death per million people is so minimal that it cannot be distinguished from normal death rates.
     
  14. Dec 21, 2006 #13

    Andrew Mason

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    Not only is it not cumulative, it seems that radiation can have the opposite to cumlative effect: pre-radiation can lower the mortality of a potentially fatal dose:
    In uranium mining country not too far from here the stories of two-headed moose and jelly-babies abound, but there is no documented evidence of anything of the sort.

    I am with you on coal. If nuclear power caused a millionth of all coal related deaths you would be hearing about it to no end. China had 6027 coal mining deaths in 2004 (US had 28). It is estimated that 15,000 premature deaths occur each year in the US due to atmospheric pollution from coal burning.

    AM
     
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