tag:blogger.com,1999:blog-3033288879708780106.post6479863460433004100..comments2024-04-20T07:34:46.696-04:00Comments on Yes Vermont Yankee: Will a Little Bit of Radiation Hurt You? Berkeley Scientists Break the Hold of Linear Non Threshold Reasoning.Meredith Angwinhttp://www.blogger.com/profile/02737538041807740424noreply@blogger.comBlogger16125tag:blogger.com,1999:blog-3033288879708780106.post-7785141034236449992011-12-25T13:48:28.285-05:002011-12-25T13:48:28.285-05:00I agree with the posters who come to the conclusio...I agree with the posters who come to the conclusion that the naming is misleading/confusing. I'm wondering if next it will be called the "Maybe-Sorta-CouldBe-If-We-Pretext-That-There-Is-No-Threshold-LNT". Of course, we are taught in logic class that in cases like this it is probably best just to whip out Occam's Razor and say the simplest explanation is best: we can make it linear if we recognize there is a threshold for harmful effects. That sure beats thrashing around with linear-quadratic and DDREF fudge factors simply to justify an initial assumption (LNT).Anonymousnoreply@blogger.comtag:blogger.com,1999:blog-3033288879708780106.post-47597786975635809272011-12-25T13:02:09.289-05:002011-12-25T13:02:09.289-05:00Thank you all for your recent comments.
Bill: yes...Thank you all for your recent comments.<br /><br />Bill: yes, I noticed the BEIR statement was missing a comma. In my post, I did a cut and paste from the official summary document, and included (sic) showing that I knew there was a problem with the language or punctuation or something. This LNT area is very controversial, and I was concerned that if I ADDED anything, even a comma, someone would say I had misquoted BEIR!<br /><br />Bob. The standard definition, learned in high school of mathematical terms is that a LINEAR function has no higher terms...it is in the form y =a +bx. QUADRATIC functions have square terms for the variables. For example y= a +bx+cx^2. There is no such thing as a linear-quadratic equation in mathematics or standard statistics. The equation either has or does not have terms in x^2.<br /><br />I discovered that in one area, and one area only, the term linear-quadratic is used. That is in dose/oncology calculations. Now, I don't see any reason why this area has to have unique mathematical constructs. Radiation dose response is a statistical area, and mathematicians and statisticians derive tables for life expectancies, LD 50 calculations, crop yields, gene cross-over probabilities, tax revenues and stock market volatility without <i>linear-quadratic</i>. This term is simply is some kind of obfuscation of the term <i>quadratic</i>. The functions either have x^2 terms, or they don't. <br /><br />At any rate, Bob, I am NOT going to continue this conversation unless you are willing to acknowledge that there are standard descriptions of mathematical functions and equations. That linear and quadratic are separate standard descriptions, depending upon the power of X in the equation.<br /> <br />If you insist that there is some entirely new type of equation, used only in your specialty, called "linear quadratic"...well, there is really no arguing with that sort of obfuscation of standard mathematics. <br /><br />No matter what the equation is about, x squared makes it a quadratic equation. This isn't about doses or responses. It is about mathematics. <br /><br />Huw Jones. Yes. We are spending way too much time on this debate. It reminds me of when people thought high-voltage lines might cause leukemia. Huge numbers of studies were done, looking for some subtle effect, which was never found.Meredith Angwinhttps://www.blogger.com/profile/02737538041807740424noreply@blogger.comtag:blogger.com,1999:blog-3033288879708780106.post-80094664856388475632011-12-25T01:25:17.737-05:002011-12-25T01:25:17.737-05:00"The other hypothesis suggests that risks are..."The other hypothesis suggests that risks are smaller than predicted by the linear no-threshold model are nonexistent (sic), or that low doses of radiation may even be beneficial."<br /><br />The quoted sentence is missing a comma after "model":<br />'The other hypothesis suggests that risks are smaller than predicted by the linear no-threshold model<b>,</b> are nonexistent, or that low doses of radiation may even be beneficial.'<br /><br />Or more clearly,<br />'The other hypothesis suggests that risks (A) are smaller than predicted by the linear no-threshold model, (B) are nonexistent, or (C) that low doses of radiation may even be beneficial.'Billhttps://www.blogger.com/profile/08749459207189576328noreply@blogger.comtag:blogger.com,1999:blog-3033288879708780106.post-2079993258127107312011-12-24T21:14:36.007-05:002011-12-24T21:14:36.007-05:00Perhaps the risk at low dose/dose rates in non-zer...Perhaps the risk at low dose/dose rates in non-zero. Or perhaps it's not. Perhaps we'll never truly know. From what I've read studying the topic for my degree, finding credible evidence on the topic is incredibly difficult. A more important question is, does it really matter? If biological effects are this hard to detect at low doses/dose rates, then they are obviously not worth worrying about in relative terms. Money spent on zealous radiological protection would be better spent on anti-smoking campaigns, safer driving schemes etc - which cost many millions of lives per year.<br /><br />As nuclear advocates, we are spending far too much time on this debate. Specifically, in my opinion we are too interested in the 'NT' in LNT, and not enough in the 'L' - Linear. When I first read about DDREF I faced a similar confusion to what Meredith describes above - with this factor included, the 'Linear' Non-Threshold becomes more like the 'Geometric-proportional' Non-Threshold.Huw Joneshttp://fissionenvironmentalists.wordpress.com/noreply@blogger.comtag:blogger.com,1999:blog-3033288879708780106.post-83377314442187357122011-12-24T20:18:18.598-05:002011-12-24T20:18:18.598-05:00Anyone (including Finrod) is free to look at the d...Anyone (including Finrod) is free to look at the data-generated dose response curve which I provided earlier. I don't see anything mystical. I see a line, more or less.<br /><br />What's mystical is why someone thinks it's mystical. Actually that's not mystical. There's a set of psychological phenomenon known as anchoring, confirmation bias, and motivated reasoning. In light of evidence contrary to emotionally held "beliefs" cognitive dissonance results. <br /><br />And so, climatologists are referred to as a "priesthood" by global warming denialists, biologists are referred to similarly by evolution denialists, doctors are the "priesthood" according to folks who wanted to link vaccines to autism even though there was zero evidence.<br /><br />And so, like all the denialists each has no doubt that at some point there "beliefs" will be confirmed. And yet, as decades pass, that time never comes. Sort of like messiahs.TheHealthPhysicisthttps://www.blogger.com/profile/05060756659263075467noreply@blogger.comtag:blogger.com,1999:blog-3033288879708780106.post-41190407803994926952011-12-24T17:41:47.921-05:002011-12-24T17:41:47.921-05:00I expect that at some point hormetic effects will ...I expect that at some point hormetic effects will be confirmed beyond any reasonable doubt. I guess the LNT priesthood will then set out to convince the rest of us that the resulting dose-response curve is still nonetheless mystically linear, confounding the ignorant assumptions of us non-theologians.Finrodhttps://www.blogger.com/profile/02447747229391757964noreply@blogger.comtag:blogger.com,1999:blog-3033288879708780106.post-11536733199331498002011-12-24T17:38:29.715-05:002011-12-24T17:38:29.715-05:00Joffan doesn't seem to understand the DDREF or...Joffan doesn't seem to understand the DDREF or threshold. DDREF is introduced because of observations. The observed cancer risk is less when the total dose is less or when the dose rate is less. If the cancer rate were the same regardless of dose or dose rate, that's what we would observe, and the current risk estimates would be much higher.<br /><br />There is a radiation threshold. It is an energy threshold. Below the lower energy range of UV there is no cancer induction. Above it, the photons possess the energy to cause changes which contribute to cancer. Above the x-ray energy range, each photon has a non-zero possibity (ie, risk) of contributing to cancer. Therefore, at those energies and above, there is no threshold.TheHealthPhysicisthttps://www.blogger.com/profile/05060756659263075467noreply@blogger.comtag:blogger.com,1999:blog-3033288879708780106.post-11164457396725062382011-12-24T17:16:20.687-05:002011-12-24T17:16:20.687-05:00LNT doesn't include DDREF; it has been tacked ...LNT doesn't include DDREF; it has been tacked on as an alteration to avoid the embarrassment of being disproved.<br /><br />ICRP pub'n #99 http://www.icrp.org/publication.asp?id=ICRP%20Publication%2099 gives the game away: "Unless the existence of a threshold is assumed to be virtually certain, the effect of introducing the uncertain possibility of a threshold is equivalent to that of an uncertain increase in the value of DDREF, i.e. merely a variation on the result obtained by ignoring the possibility of a threshold."<br /><br />As I interpret it - admitting a threshold can be avoided by introducing DDREF. But of course that model is no longer linear with high doses, so has no experimental justification for assuming other than zero effect.<br /><br />Bob Applebaum seems to have recovered from his initial dismay at my pointing this out to him and has now embraced DDREF, ignoring all attempts to point out its ill-foundedness.Joffanhttps://www.blogger.com/profile/18025437863119781181noreply@blogger.comtag:blogger.com,1999:blog-3033288879708780106.post-38682543178140459842011-12-24T16:49:42.917-05:002011-12-24T16:49:42.917-05:00No the term is not misleading. It's just that ...No the term is not misleading. It's just that many people don't understand the context. It reminds me of people who ask, "if evolution is true, why are there still monkeys?". Those people don't understand evolution.<br /><br />See the figure in this link:<br /><br />http://www.nap.edu/openbook.php?record_id=11340&page=16<br /><br />Overall, the dose response is L-Q. Below 1.5 Sv, the linear curve and L-Q curve can be drawn through the same data points. They are very similar (linear) through the region labeled "Low Dose Range", which is the region of typical occupational and public exposures.<br /><br />I hope that helps.TheHealthPhysicisthttps://www.blogger.com/profile/05060756659263075467noreply@blogger.comtag:blogger.com,1999:blog-3033288879708780106.post-17546486903609998422011-12-24T15:05:14.690-05:002011-12-24T15:05:14.690-05:00Huh? In other words, Linear Non Threshold means &q...Huh? In other words, Linear Non Threshold means "this function includes various terms of higher orders, such as exp2". <br /><br />With all due respect, I don't think I am not "getting" the epidemiology. I am very familiar with all sorts of functions. I am familiar with least-squares fitting of functions. However....Functions with higher-power terms are not linear functions. <br /><br />I am beginning to think the name is quite misleading.Meredith Angwinhttps://www.blogger.com/profile/02737538041807740424noreply@blogger.comtag:blogger.com,1999:blog-3033288879708780106.post-84111456827855942222011-12-24T14:43:31.914-05:002011-12-24T14:43:31.914-05:00Meredith:
You don't seem to understand the ep...Meredith:<br /><br />You don't seem to understand the epidemiology. One observes cancer incidence as a function of dose. There are error bars in fitting the data. Overall, the best fit is linear-quadratic. However, in the low dose range, there is no statistical difference between linear modeling and linear-quadratic modeling. This is because the quadratic term decreases as the square of the dose reduction (ie, reduce the dose by 2, the quadratic term significance decreases by 4). So, parsimonously, we just say LNT in the low dose range. Linear is linear...but with error bars one can draw lines of different slopes within the error bars. In the "big picture" the response is still LNT.TheHealthPhysicisthttps://www.blogger.com/profile/05060756659263075467noreply@blogger.comtag:blogger.com,1999:blog-3033288879708780106.post-23202190743755338822011-12-24T14:35:09.733-05:002011-12-24T14:35:09.733-05:00Bob. Thank you for the comment. I think we are t...Bob. Thank you for the comment. I think we are talking about different LNTs.<br /><br />My view of LNT is that it means Linear Non Threshold, even at low doses. That's what Linear means. I am a chemist, and a linear function has one slope over the range of the function. I mean, that's the definition.<br /><br />You say that your understanding of LNT is that there are DDREFs that acknowledge that DNA damage is better repaired at low doses. That would mean there is a different slope at low doses. Which means the function is not LINEAR down to zero. Now, the function may still be called Linear Non Threshold in the vernacular, but you are saying it isn't really linear at low doses because the DDREFs change the slope. <br /><br />If that is the case, I DO think they should rename it. However, I am not good at getting functions renamed! My husband is a mathematician, and he once threw one of my chemistry books across the room because "The Dirac Delta Function is NOT a function!" They never renamed it though ;-)<br /><br />I guess we are stuck with the name LINEAR Non-Threshold!Meredith Angwinhttps://www.blogger.com/profile/02737538041807740424noreply@blogger.comtag:blogger.com,1999:blog-3033288879708780106.post-69003799847173321592011-12-24T13:59:01.281-05:002011-12-24T13:59:01.281-05:00This study doesn't refute LNT, it supports it....This study doesn't refute LNT, it supports it. LNT includes a DDREF (Dose & Dose Rate Effectiveness Factor). This study shows that DNA damage is better repaired at low doses, which is what the DDREF accounts for.TheHealthPhysicisthttps://www.blogger.com/profile/05060756659263075467noreply@blogger.comtag:blogger.com,1999:blog-3033288879708780106.post-19527544426713323152011-12-23T11:07:51.779-05:002011-12-23T11:07:51.779-05:00Meredith:
Thank you for producing a well reasoned...Meredith:<br /><br />Thank you for producing a well reasoned post questioning our continued acceptance of the Linear No Threshold dose response ASSUMPTION and for pointing out the damage that gets done due to the resulting statement that there is "no safe dose of radiation".<br /><br />I have a stalwart member of the radiation protection guild who regularly comments on my blog in defense of the LNT. He acknowledges that the risk at low doses is small and that the risk at very low doses is very small, but he believes that it is irresponsible to tell people that there is NO risk. His science cannot measure the risk, but he and his colleagues assumes that it is PRUDENT to acknowledge the possibility that some risk exists.<br /><br />I strongly disagree. If I can tell someone that it is safe to take an automobile trip with me, I should be able to just as honestly say that it is safe to live in an area with background radiation doses of 20 mSv (2 Rem) per year. There is no need to confuse the issue or the target audience with details about how safe it is. It is safe enough.<br /><br />As you pointed out, the LNT is based on an assumption. Calabrese recently told the story of how Muller ignored evidence of a threshold dose that came from one of his own students because he had an agenda of trying to stop nuclear weapons testing. <br /><br />http://www.sciencedaily.com/releases/2011/09/110920163320.htm<br /><br />I believe that Shaw, Shadis, Lovins, Katz, Lyman, Bradford, Caldicott and dozens of others will also ignore the evidence because it conflicts with their agenda. However, their agenda is much less moral than Muller's; I can agree on the need to use whatever techniques are needed to halt atmospheric nuclear weapons testing; I cannot agree with those who apply those same techniques to halt nuclear energy development.<br /><br />The primary beneficiaries of excessive radiation fear are the people who sell coal, oil and natural gas. There are also beneficiaries in the radiation protection guild and among the corporations that build the exceedingly expensive structures that are designed to reduce radiation levels to absurdly low levels, even under worst case accident conditions.Rod Adamshttps://www.blogger.com/profile/03652375336090790205noreply@blogger.comtag:blogger.com,1999:blog-3033288879708780106.post-33348247233346672572011-12-23T09:47:36.364-05:002011-12-23T09:47:36.364-05:00Hi Howard. As you and I well know, nothing will c...Hi Howard. As you and I well know, nothing will convince Shaw, or Shadis, or Katz, or...<br /><br />They are not my target audience! I hope to inform people of these new research results...people who are not terrified of radiation. People who make a career of fearing radiation will continue with their career path, no doubt.<br /><br />Fourteen elderly Japanese died during the evacuation, as a direct result of their bus trips, problems with IVs and hydration, etc. The Japanese government should think about that, also.Meredith Angwinhttps://www.blogger.com/profile/02737538041807740424noreply@blogger.comtag:blogger.com,1999:blog-3033288879708780106.post-71971269246702650272011-12-23T09:30:34.372-05:002011-12-23T09:30:34.372-05:00Great Blog. But will Sally Shaw be reassured?
In...Great Blog. But will Sally Shaw be reassured?<br /><br />In addition to "any amount of radiation is dangerous" opponents of nuclear power act as though radiation comes only from man-made sources. Thus we have two wrong ideas to correct.<br /><br />The Japanese government is supposedly wrestling with how much radiation exposure to allow citizens each year when they move back to the homes evacuated. There is a competing health effect. It is the stress of living as an evacuee. Medical science knows that stress has real detrimental health effects.<br /><br />I've seen the figure a 20 msv per year as the amount of exposure discussed. I have received more than twice that this year for medical purposes (2 CT scans and operating table fluoroscope). The highest exposure per year from the environment is in Ramsar, Iran at 300 msv.<br /><br />Scientifically, for the Japanese government to allow 20 msv per year is straight forward and safe. Politically it will be difficult.Howard Shaffernoreply@blogger.com