1. ” How do x-rays and nuclear radiation affect organisms? About 100 (or fewer) measurable DNA changes occur per centigray (cGy) of radiation per cell. If we compare the amount of natural (endogenous) DNA damage that occurs in one year, which is ~ 8766 h/y x 10,000 = 90 million changes per cell, with the damage caused per cell by natural background radiation, which is about 0.24 cGy/year x 100 = 24 changes, we can see that the cell damage from background radiation is relatively negligible.”
    As explained that the LNT model does not fall with this data?

    1. @jhon

      I’m not sure I understand your question, but I’ll try. Ionizing radiation deposits energy into human tissue depending on its intensity. That energy affects the tissues in various ways, and the initial effect is proportional to the dose.

      What the “no safe dose” hypothesis does is to stop at that point and ignore the fact that living itself deposits energy into tissue and affects cellular chemistry in similar ways. It ignores the response and repair mechanisms that tissues have developed that turn what seems to be damage in the immediate aftermath of the interaction into something beneficial and useful to the body. Of course, there is a limit to how much the response and repair mechanism can handle before it gets overwhelmed. That is the point at which unrepaired damage begins to accumulate. If the radiation source goes away, it is possible for the response and repair mechanism to work off the backlog and heal the organism. If the dose continues, the damage can overwhelm the organism and result in permanent injury or death.

      Does that help to explain why the overall health effect does not follow a linear model and why there is a threshold below which there is some benefit given by the stimulation caused from low doses of radiation?

      1. @Rod Adams and Jhon

        Do we have evidence that DNA repair mechanisms are always perfect?

        This appears to be an “unproven” assumption of a threshold dose response model (something where caution rather than hubris should be a guide).

        Again, the position on LNT as stated by most nuclear advocates appears to be overstated (and a straw man). There is much deliberation about the concept in the scientific community (and in the summary reports reviewing the model). Typically, it is described in the following way (not as a uniform principle and a bunch of paid for hire lab scientists measuring health impacts down to the single atom and single electron track).


        Most radiation biologists recognize that the complex biological events needed for a cancer to develop cannot be described by a simple LNT model. However, an alternative model would be impractical for the purposes of radiation protection. The data available from epidemiological studies are associated with enough uncertainty that use of more complicated dose response models cannot be justified (p. 396)

        I don’t think anybody here is really saying much that matters to how most people think about LNT (scientific review panels, and such). Do you think that matters, or is it only relevant that nuclear advocates speak to their own views (and not engage with the scientific community over what is being discussed here)?

        1. Do we have evidence that DNA repair mechanisms are always perfect?

          EL – No. In fact, anyone advancing the position that a hormetic response curve deserves more attention (as Rod does) would argue that DNA repair mechanisms absolutely are not always perfect. In fact, it would be impossible for hormmesis to work if such repair mechanisms were perfect.

          Since your background, training, and experience is more rhetorical than scientific (as should be obvious to anybody reading your comments), please let me explain further. This is a simplified explanation of something that is much more complex, but considering your background, it should suffice.

          DNA damage occurs from many sources, with the vast, vast majority of them having nothing at all to do with ionizing radiation. The cells are able to repair such damage; otherwise, none of us would be here to discuss this. Nevertheless, such repair mechanisms are not perfect. So precursors that can eventually lead to cancer are able to form. When and how they form and how many eventually cause the disease depends on chance, which is why cancer is a stochastic disease.

          The proposed mechanism behind hormesis postulates that low exposures to stressors (e.g., ionizing radiation) stimulate these repair mechanisms and make them more effective, much in the way that exposure to viruses stimulates the body’s immune system to protect against the virus, which is how immunization works. Therefore, in addition to being able to repair the damage caused by the stressor itself, the cell is better able to repair damage by ubiquitous causes such as metabolism.

          Perfection is never part of the equation. It is only your strawman.

          1. Jhon – Thank you for the question. I don’t think that there is enough evidence, at this time, to state conclusively that a hormetic response is the correct dose response curve. However, I do believe that there is more than enough evidence at this time to seriously question whether the Linear No-Threshold (LNT) model has anything to do with reality and whether it is still an appropriate model to use for radioprotection.

            The situation is more complicated than a simple “yes/no” question. One thing that everybody acknowledges is that the dose response to radiation for leukemia is different than the dose response for solid tumors. In fact, the leukemia dose response curve is undoubtedly nonlinear and is an exception to the LNT orthodoxy, even among LNT fanatics. If one could somehow achieve “perfect” scientific knowledge of how these things work, I strongly suspect that the dose response curve for each particular type of cancer is different from the others, but in the real world we have to work with what is the average risk for all cancers, which is why drawing general conclusions from studies that investigate only one type of cancer is a serious mistake.

            I consider myself to be a pragmatist. Therefore, I can accept the reasoning that the sheer simplicity of the LNT model can be useful for some regulatory applications, and so, convenience is a strong argument in its favor. That doesn’t mean, however, that the model should be mistaken for how nature actually works; neither should it be misapplied for such applications as calculating (phantom?) deaths from exposures to low doses of radiation by large populations.

            My opinion is hardly radical. In fact, it is shared by the US Health Physics Society, the US American Nuclear Society, and the French Academy of Sciences.

            The adults in the room recognize the convenience of the simple LNT model for certain applications, but realize that it almost certainly is not a true reflection of how nature works. The rest are still fixated on childish notions such as positing that even one ionizing particle can cause a DNA strand break that leads to cancer and wondering whether DNA repair mechanism are “always perfect.” It can be difficult to argue with such simpleminded fools.

          2. @Brian Mays

            Minus the ad hominem knuckle dragging, I don’t disagree with anything you have said here. But you left open a gaping hole in your reply (two of them)?

            “more than enough evidence … to seriously question … whether [LNT] it is still an appropriate model to use for radioprotection”


            “I can accept the reasoning that the sheer simplicity of the LNT model can be useful for some regulatory applications.”

            You are not making any sense here.

            And it seems you might actually agree with the “no safe dose” mantra. If repair processes are imperfect (even when stimulated as part of a stress response), and cancer is a stochastic disease (meaning it is non-deterministic at very low doses), where does the notion of a “threshold” come from? Hormesis may be protective, but perfection is not a part of its definition (according to you). Unless repair processes are perfect, there is no threshold. Am I missing something here?

            The document above summarizing BEIR VII makes the same point (p. 396).

          3. EL – Why don’t you take it up with the HPS instead of me? What I’ve put forward here is essentially their position (cf. “Radiation Risk in Perspective,” Position Statement of the Health Physics Society, 2004).

            Personally, my hypothesis is that either (1) you simply lack the training in quantitative analysis to understand what I and the HPS are talking about or (2) you’re paid to be deliberately obtuse on this website so as to waste everyone’s time.

            If anyone else reading this here, who is not an obvious shill, has questions about my take on this matter then I’m fully willing to explain my position further. I will not, however, waste my time on you, EL, because I’m no longer stupid enough to play your game. You’re here solely to waste people’s time. I don’t even care whether you’re paid or not. That’s between you and your employer, whoever that is. It’s just that my time is worth more than that, and I no longer care what you think or what you claim that you’re too stupid to understand.

            Please go pester someone more gullible than me.

          4. @Brian Mays

            If you think I have mischaracterized the position of review bodies on LNT, it would be terrific to point it out (because you have not done so). The same regarding contradictions in your own replies to my comments (a conversation that you started). Your bluster does little to cover up these rather obvious and straightforward points. And no, nobody is paying me to contribute or otherwise participate in the site (it diminishes the quality of your reply, along with all of your bluster, to suggest as much).

            In particular, the source you provided from HPS (“Radiation Risk in Perspective“) says nothing about scientifically measured or proven thresholds, but does include the following: “The possibility that health effects might occur at small doses should not be entirely discounted.” They define zero health effect not as the absence of health impacts, but as “the inability to detect any increased health detriment.” They also state biological mechanisms associated with repair mechanisms and hormesis are “not well understood,” and LNT does not fully account for biological mechanisms that are “not well understood” (but is rather a simplified framework, acknowledged as such by review bodies and most radiation biologists, as indicated upthread).

            It’s clear you’re good at deflection, but very poor at answering specific questions (or resolving contradictions in your own replies).

          5. Jhon – At this time, the majority of the evidence points to an overestimation of risk by the LNT model.

            For example, as I have pointed out elsewhere, it is widely accepted in the scientific community that the dose response for leukemia is not linear and in fact curves upward, which means that a linear extrapolation from high doses to low doses would overestimate the risk.

            Perhaps some future research will indicate that the linear model underestimates risk at low doses in certain situations. I can’t say, because I don’t claim to be a fortune teller. But the information that we have today strongly suggests that the real dose response curve for the vast majority of health risks falls under the estimates provided by the very simple LNT extrapolation from high doses. How much it falls under remains the main subject of debate.

        2. The establishment argue that everyone must agree with the LNT model because the real situation is too complex and multi-faceted to model? A pathetic argument that shows the contempt they hold for science.

    2. As x-rays make no difference, they would also harm the repair mechanism in the cell.
      So more bad repairs and more cancer.

      Why would radiation not damage the repair mechanism?

  2. “…Drosophila (fruit fly) experiments. Those experiments did not test any levels below about 50 rad…”
    So that would be 500 millisieverts? Am I right in thinking radiation therapy doses of up to 10 sieverts over 40 days is not uncommon? ie 20 treatments of 500 millisieverts with an 48 hr delay between each treatment. I’m fuzzy on the exact numbers and would appreciate correction. According to LNT such a treatment should kill 10% of the recipients, I assume that is not the case.

    1. Therapy dose can reach even 60 Gy in some cases. Howeve this is not a full body exposure, and even at organ level, most of the dose is received by the cancerous tissues, so it´s very far of being equivalent of 60 Sv this would represent if the whole body received it. Taking into account that, the result are quite supportive of the LNT, ie a very large % of the patients will develop years later a radio-induced cancer of the irradiated organ. The aim is to give them a chance not to die within a short timeframe of their current cancer, so the risk they will die years later of the induced cancer, if they are still alived in the 10 to 15 years it will take for it to occur, is then accepted.

  3. The LNT has been inconsistantly applied. Aircraft passangers and crew are exposed to relatively high levels of radiation that increases with altitude. Yet no one is worried about the danger, and no one is warned. People who live in Denver and other high altitude cities receive higher levels of radiation No one is concerned and no one worries. In some areas radioactive elements like radon travel from rocks and the soil Some of these areas people are exposed to significant levels of radiation, yet no one is worried and no one is warned. Only ion medicine and nuclear technology, is there any concern about radiation. It would appear that source has aq lot to do with whether the no threshold for harm counts for anything.

    1. @Charles Barton

      I remain a cynic. Starting with the first BEAR report in 1956, the establishment science panels have always focused on what they called controllable or optional sources of radiation exposure and virtually ignored all “natural sources,” taking those as a given, unavoidable part of our environment.

      At the time of the report, there were four sources of concern – open air bomb testing, industrial applications, medical applications and nuclear energy.

      Bomb testing was the one that most worried the public. Many scientists, often feeling guilty over their role in developing The Bomb, willingly exaggerated the risk of radiation in order to increase public concerns about testing. Those increased concerns resulted in strong political movements and pressure to halt the testing.

      However, the risk exaggerations did not stop after the test ban was implemented.

      It is no surprise to me that the places where “human-made” radiation are applied happen to be lucrative industries with competitors who market products or services that are often less effective and more expensive than those that can be developed using radioactivity.

      There are often strong motives behind the campaigns to increase fear and to impose additional regulations or layers of protection that would react to that fear.

      Unfortunately, most nukes cannot understand that all of the extra money they spend building additional backups and containment domes simply increase the fear. The public’s logical reaction is “it must be really dangerous” if you are willing to spend all that time, effort and money to reduce exposures.

  4. Rod, despite the fact that I grew up in a community that saw at one time or another a zozen operating reactors, I received far more radiation in my life time from medical and dental environments, yet no one ever warned me that my dental exray could cause ny head to fall off my neck. Now why is that?

    1. @Charles Barton

      Perhaps because the effort to increase fear of radiation in medical treatments is relatively less obvious than in nuclear energy.

      However, there were numerous effective treatments that were abandoned over the years because they involve what some people considered to be an excessive amount of radiation compared to the nature of the ailment.

      There is a large scale campaign underway today aimed at discouraging people from using computed tomography (CT) scans and to use the lowest possible radiation dose for x-rays. It’s called “Image Gently.”

      Charles Ferguson and his friends at FAS are working hard to convince hospitals to replace their low cost, low energy demand Cs-137 blood irradiators and replace them with less reliable, more energy intensive, more costly and somewhat less effective x-ray machines.

      In many hospitals, nuclear medicine departments are disappearing because of the excessive overhead that they require.

  5. I believe and agree, “Science has … the “no safe dose” hypothesis about radiation.” Rod Adams and Professor Calabrese have called out the scientists and the established science. [applause] – This is the scientific method. Get on with the deliberate scientific work ahead. I want to know!

  6. The main thing which never sits well with me with LNT is the accumulated dose hypothesis. i.e. 1 Sievert in a second is equivalent to 1 Sievert in a lifetime. This has known to be incorrect since its inception but is integral to the whole model. if you receive 1 Sievert in a second you are likely to die from detrimental effects but one Sievert in a lifetime will have no measurable effect on you what so ever.

    Remove this and a threshold must exist as it has to be a rate response effect which implies some sort of repair mechanism.

  7. I am a bit late to getting around to reading this, but that next to last paragraph (pasted below) sparked a thought.

    How much of the Japanese fertility decline, within the whole Japanese society, can be attributed to the group of geneticists? That is a potentially staggering affect of this whole issue.

    “In what was most likely an unintended consequence of the report, its findings probably intensified the ill-treatment and ostracizing of the Japanese hibakusha, the people exposed to radiation as a result of the atomic bombs dropped on Hiroshima and Nagasaki. After all, it asserted that radiation exposure did unrepairable harm to genetic material and increased the probability of defects and mutations in future generations. Who would want to fall in love with someone who scientists have asserted would produce mutant children, especially in a society where generational responsibility is so strong?”

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