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LNT Model May Not Be True

  1. Oct 26, 2011 #1
    http://www.umass.edu/newsoffice/newsreleases/articles/136706.php" [Broken]

    This would be interesting if true, though there is still evidence for both sides of the aisle.
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Nov 1, 2011 #2


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    The only way to get reliable enough statistics to determine whether low radiation dose is indeed harmful would be to implant a dosimeter into every baby born and wait for all of them to live out their lives. In ~60-80 years you might have good enough statistics to make a valid conclusion.
  4. Nov 1, 2011 #3


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    The question is whether a small change in radiation dose causes injury, not whether a low dose of radiation is harmful. Radiation is all around us and part of us. The studies of populations in areas with different background radiation levels can already provide a lifetime difference. These studies have not concluded harm that can be tied to the background radiation differences. So then would aclimatization be a factor? That could be evaluated by studying people who have moved to areas of higher or lower radiation levels.

    What you are really interested in is whether a small change in acute dose from a specific source (over a period of hours or months) is enough to upset the biological defenses and cause prompt injury or latent cancers. Injury is ruled out for doses less that a value around 250 mSv where minor blood changes can be observed. Latent cancers have been studied and have not been able to statistically prove harm at very low doses on the order of background radiation levels, That does not prove the negative - that there is no harm. Nuclear regulations are based on LNT as a conservative measure. ALARA is a recognition that zero dose is not an achievable standard if we want to have nuclear power. It simply works to minimize any change in exposure to employees or to the public to levels where risk is not distinguishable from background.

    So we don't need to start implanting dosimeters in babies to study radiation.

    OTOH It is interesting to continue to see how people get so wrapped up over LNT and seem to ignore risks that have much larger, proven impact on health and safety. Where is the concern over atmospheric releases from fossil fuels? Where is the demand to close all plants manufacturing automobiles and trucks? High risk ocupations like farming and commercial fishing are tolerated because we need the benefits they provide. Risk is risk. If the world was really motivated by risk, nuclear power would be well down the list.

    So the bottom line, is LNT valid or not? I do not care. It is the basis of the current regulations we work with, so if it is correct we are doing what we need to do. If it is wrong and there is a threshold, we aren't hurting anyone.
  5. Nov 1, 2011 #4
    LNT can't be true, otherwise places with radiation x3 times more than average would see x3 cancers. In Ramsar, there should be x100 more cancers than average (i.e. every single person there should have cancer).
    This is clearly not the case.
  6. Nov 1, 2011 #5


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    This is my point. I never claimed there was no harm. My claim is that the harm is so small that, if it does exist, it is impossible to distinguish. I bet you are more likely to get cancer from the stress induced by worrying about radiation than the radiation itself.

    Problem is there are countless other factors involved. Maybe there are fewer cancers because fewer people get diagnosed with cancer for lack of modern medical technology. Or maybe because of their diet. Or because they spend more time outdoors. No one knows, and there is no way to find out without a truly massive experiment.
  7. Nov 2, 2011 #6
    I don't think so. In developed countries, cancer detection is pretty reliable, and people in these countries do statistical analyses.

    It would be pretty easy to detect that people living in regions with abundant granite etc have cancer rates elevated corresponding to elevated levels of background radiation.

    IIRC today about every third person dies from cancer (thanks to improved health care which reduced incidence of deaths from other causes). So on average, we see ~30% deaths being caused by cancer. Or, roughly, in ~70 years of life average person has 30% chance of getting cancer.

    In Ramsar and a few other such spots where background is about a hundred times higher than average, if LNT is correct, the 30% chance of getting cancer should be reached not after 70 years, but after 0.7 years. Well, I guess there are tons of effects (maybe young children are less susceptible to cancer, I don't know), but clearly, even if I'm off by *an order of magnitude*, almost no one there would survive till their 25th birthday. I bet even in Iran (not very advanced country) people would certainly notice that people are dying like flies there! In reality, people in Ramsar not only survive past 25 years - they don't even show any notable increase of cancer rate!

    LNT can't be correct. But I guess these days it's not a politically correct thing to say: I am going to be labeled a "nuclear industry stooge" or something and accused of wanting people to be poisoned, if I would try to say that in a printed article.
  8. Nov 2, 2011 #7
    You're assuming radiation is the only cause of cancer, which is clearly not the case.
  9. Nov 2, 2011 #8


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    Based on the fact that children are growing, their cell reproduction rate is higher than adults. Theoretically that would make them more susceptible to reproduction of damaged cells leading to cancer. You are not a stooge to defend your opinion. There are academics arguing the same point.

    The study of effects of acute doses started with survivors of Hiroshima and Nagasaki. Based on the studies there was a linear relationship for cancer versus dose, but there was data that could distinguish rates of cancer from low doses compared to rates in unexposed populations. The result was a conservative assumption of the LNT theory. It remains unproven today. There have been attempts to apply LNT in evaluating the risks of chronic exposure to radiation. And that fails miserably when anomalies like Ramsar are included. That leads me to question LNT, but again, every engineering problem I have worked has been based on ALARA and assumes that LNT is valid.
  10. Nov 2, 2011 #9
    Surely LNT is to simplistic?

    Internal exposure to man made isotopes may have vastly different pathologies than exposure to atmospheric radon.

    Radon has always been in our environment, likewise cosmic rays.

    We have evolved with natural sources all around us.

    What hasn't been in our evolution is Strontium 89-90 embedded in bone marrow.
  11. Nov 3, 2011 #10
    One typical natural source, Radium, is chemically similar to Sr.
    Another, K-40, is chemically similar to Cs.

    So, no, we in fact had some natural sources around us for milennia, whose characteristics are not very different from artificial ones from fission.
  12. Nov 3, 2011 #11
    C'mon folks you all surely must know that there's a world of difference between exposure to radiation and ingestion or inhalation of radionuclides . Cornish spinach is safe because, granite is not easily absorbed and no one bothered to atomise it and sprinkle a liberal dusting over everything edible
  13. Nov 4, 2011 #12
    Spinach is a plant. All plants contain elevated levels of potassium (compared to meat and other animal-based food). All potassium contains K-40. K-40 undergoes 1.3 MeV beta decay 90% of the time and 1.5 MeV gamma the other 10% (IOW: K-40's decay energies are not low, they are stronger than Cs-137!). Eating any plant, you are getting yourself exposed to internal radiation from K-40.

    Radium is an alkaline earth element. Those are pretty mobile. Radon is a noble gas - much more mobile than radium. Both will escape from fractured rocks which contain elevated levels of uranuim; or places with significant geothermal activity. Radium in water you drink will be deposited in the bones, since it is chemical analog of Calcium.

    So, sorry to burst your bubble, but we do experience *internal* exposure to radiation from natural sources our whole lives.
  14. Nov 4, 2011 #13
    Typical background radiation in the U.S. is around 3.5 mrem, roughly 3.5x10^-5 Sv. Cancer risk as a function of radiation exposure, according to current models, is about 5% per Sv per year whole body. Even if a person was exposed to levels of radiation 100x what we have in the US, they would still only be receiving about 3.5 mSv annually. A linear model does not indicate that tripling background exposure triples cancer incidence, but it may triple your risk of developing cancer from background radiation. There is a big difference.

    See the following:

    UNSCEAR (2000): Sources and Effects of Ionizing Radiation, Vol. II: Effects
    ICRP 60 (1990): Recommendations of the International Commission on Radiological Protection
    NCRP 116 (1993): Limitation of Exposure to Ionizing Radiation
    BEIR V (1990): Health Effects of Exposure to Low Levels of Ionizing Radiation
  15. Nov 4, 2011 #14
    Pop :rofl:
  16. Nov 4, 2011 #15


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    Good point. But the next question follows:

    If you compare an area with triple background radiation and cannot detect a change in cancer incidence rates or types or longevity, what conclusions or hypotheses can be made? If you find an area with higher background radiation where people have longer average life expectancy, what does that mean? If you study nuclear power plant radiation workers and find they have a lower risk of death from cancer than people in the surrounding area, please explain what that means.

    There are studies that have made those exact findings, but in general they have not been able to draw any conclusions from those results. In fact it may mean that the effects of radiation are swamped by other social, genetic, and environmental risks.

    Compare that to "studies" like the Tooth Fairy Project. If they find one case of chidhood thyroid cancer or leukemia on record and have baby teeth in the same state as a nuclear power plant with detectable radiactive isotopes it must mean the nuclear plant is to blame.

    Tobacco use (Lung, mouth and throat), chemical toxins (liver, kidney), UV radiation (skin) are clear carcinogenic causes. But those cancers also strike non-smokers, and others without major risk factors. While high acute radiation doses have been linked to cancer, radiation at low levels has no statistically valid link to cancer.

    Buying a lottery ticket causes a huge increase in your chances of winning. Buying a second ticket makes an insignificant difference in your odds. Background radiation and all the other carcinogens is like the first ticket. Small chronic doses of radiation are like the second.

    Bottom line, if a difference can't be measured, does it matter? Please understand that I am not saying there is a threshold. If the regulation and our practices are based on LNT we are being responsible. If you really want to make a measurable change in health risk, eliminate tobacco.

    If that isn't enough eliminate automodiles, trucks and other motor vehicles and end use of fossil fuels. (Of course the resulting starvation and breakdown of society might be an unintended consequence of those actions.)
  17. Nov 22, 2011 #16
    I thought about incorporating radiation hormesis into a class project when I was a sophomore.

    When I asked one of my nuclear engineering professors about the idea, he admonished me and vehemently proclaimed that "radiation hormesis is... it's... it's [freaking bullcrap]!"

    The above statement has been modified to be PG-13, but I'm sure you can figure out what his exact words were. That also seems to be the opinion of most of my professors until they see solid evidence otherwise.
  18. Nov 22, 2011 #17


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    I'm sorry but I just had a huge flair of disgust.

    This is another wonderful example of "settled science." We have made up our minds don't confuse us with facts. You don't need curiousity or skepticism to be a successful academic "scientist."

    If he had provided you with references or reading to support his statement, then he would have at least been contributing to education. He may be right, but he should never discourage or belittle somebody questioning whether basic assumptions are masquerading as truth. Einstein isn't remembered for assuming that classical physics was the limit of truth.
  19. Nov 22, 2011 #18
    He explained, but still destroyed hormesis in my impressionable sophomore mind (lol). Looking back, I have the same feelings about it that you do.
  20. Apr 18, 2013 #19
    Civilian Cancer Deaths Expected to Skyrocket Following Radiological Incidents

    I've been trying to pin down what safe levels would be, but end up finding papers that seem to show benefits from some radiation, and the ability of living organisms, including humans, to tolerate much higher levels than are presently accepted. This Cobalt-60 study seems very comprehensive, and suggests benefits for hormesis.
    Effects of Cobalt-60 Exposure on Health of Taiwan Residents Suggest New Approach Needed in Radiation Protection
    As has been mentioned on PF previously, there have also been studies of residents of Ramsar, Iran.
    Very high background radiation areas of Ramsar, Iran: preliminary biological studies.
    What I can not find however are results for long term experiments on the effects of various levels of ionising radiation, perticularly gamma, on lab animals, that show any detrimental effects at levels that anyone is ever likely to receive without indulging in some very silly behaviour. The only test I did find was determined to be inconclusive, as the control group (rats and Caesium-137) got cancer at the same rate as the test group. Yes, there are lethal levels, around 7.5 Gy, but also tests that show that a caffiene based compound can protect against even such high exposures:
    Caffeine protects mice against whole-body lethal dose of gamma-irradiation.
    So is our fear of radiation, even at much higher levels than presently accepted, actually based on any sound science? Could it be that our evolution on a planet that was much more radioactive in the past have provided us with the ability to withstand and adapt to, and even benefit from some radiation? Looks that way to me so far.
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