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Old 03-13-2010, 11:46 AM
JoelUpchurch is offline
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Is exposure to small amounts of radiation beneficial?


http://www.straightdope.com/columns/...ion-beneficial

I'm skeptical of radiation hormesis myself, but there are pretty strong indications that the Linear No Threshold (LNT) hypothesis for radiation exposure is invalid.

The strongest case is the town of Ramsar in Iran.
http://www.angelfire.com/mo/radioadaptive/ramsar.html

The exposure levels there can be as much as 200 times normal background radiation.
http://en.wikipedia.org/wiki/Ramsar,...#Radioactivity

It is important to make a distinction between external radiation exposure and inhaled radioactive particles. Alpha Particle have very low penetration and will be stopped by the skin, but the risk is much greater if the radioactive particles are lodged in your lungs.
http://en.wikipedia.org/wiki/Alpha_p...ogical_effects
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Old 03-13-2010, 12:06 PM
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[URL="http://www.straightdope.com/columns/read/2926/is-exposure-to-small-amounts-of-radiation-beneficial"]
I'm skeptical of radiation hormesis myself, but there are pretty strong indications that the Linear No Threshold (LNT) hypothesis for radiation exposure is invalid.
...

People who maintain that there is no threshold below which radiation is safe, ignore the fact that it is virtually impossible to find a place where there is no background radiation. [or maybe they are speaking to the fact that life itself is hazardous and can't be considered safe in any dose...but I'm probably giving them too much credit].

To speak to Cecil's topic, I attended a conference where one of the speakers gave a paper on (working from memory here) Nuclear Waste as a Nutritional Supplement. I wasn't able to attend that session and I can't find the proceedings online but on Monday I will see if I can find the conference CD in my office.
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Old 03-14-2010, 12:48 PM
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There has never been any evidence for the Linear No-Threshold theory - it was simply a bureaucratic decision because it was easy to measure & caculate which has become politically indispensible to technophobes. Since there is no evidence it is not a testable theory & thus, by definition, not part of science.

While hormesis is difficult to prove absolutely there are quite a number of unrelated pieces of evidence sdupporting it. Perhaps the strongest being the negative correlation between radon in homes & lung cancer. Note that this is a form of radiation which is not kept out by skin because it is breathed in in the air.
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Old 03-15-2010, 08:00 AM
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There has never been any evidence for the Linear No-Threshold theory - it was simply a bureaucratic decision because it was easy to measure & caculate which has become politically indispensible to technophobes. Since there is no evidence it is not a testable theory & thus, by definition, not part of science.
That's a bit strong. It's true that the Linear No-Threshold model is easy to measure and calculate, but it's also plausible based on our current theory of carcinogenesis. And since we don't have evidence for picking which more complex model to use, using the linear model is in fact best scientific practice.

And it's no less testable than any other scientific model -- like almost any other scientific theory, we can never say it's always true in all times and places, but we can say it's been upheld when it's been tested.

P.S. Message to Donald "removing my eyeball to look into the other eye" Carr -- If you really want to know what it's like to look into one of your eyes, before major optical surgery you might want to try this piece of technology called a mirror (you could even use two if you don't want a reversed image).

Last edited by TubaDiva; 03-15-2010 at 12:35 PM. Reason: Added message to the eye guy/TubaDiva fixed quote
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Old 03-15-2010, 12:17 PM
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Has anyone ever studied lab animals in an ultra-LOW radiation environment, such as the deep underground neutrino detecting sites?
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Old 03-15-2010, 07:39 PM
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Radiation exposure


It would be interesting-but impossible to find out- what would happen to a person if he or she were never exposed to radioactivity of any sort.
We have developed as a species over the last few billion years exposed to significant (but doubtless slowly decreasing) levels of radioactivity. Who knows?- it may have been beneficial. Presumably it has caused endless random genetic mutations, some of which must have made a positive contribution to evolution.
I suspect- but of course have no proof- that we worry far too much about minor increases in background radiation. (I'm thinking of Three Mile Island- but not Chernobyl!)
A result of this needless concern is that we have failed to develop a new generation of nuclear power stations, thus needlessly contributing to global warming. Roll on ITER!
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Old 03-16-2010, 08:07 AM
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That's a bit strong. It's true that the Linear No-Threshold model is easy to measure and calculate, but it's also plausible based on our current theory of carcinogenesis. And since we don't have evidence for picking which more complex model to use, using the linear model is in fact best scientific practice.

And it's no less testable than any other scientific model -- like almost any other scientific theory, we can never say it's always true in all times and places, but we can say it's been upheld when it's been tested
So if it is testable Quercus perhaps you could answer the question of when it has been tested & proven?

The fact is there has never been any actual evidence to support it whereas there is a lot, from the better survival rates of numerous groups of nuclear workers, lower cancers in high radioactivity states, lower lung cancer in high radon houses to the contaminated Taiwanese apartments & repeated experiments on plants & animals which prove hormesis. The LNT supporters all say these don't count & thereby say that there are no possible results which could, in their minds, disprove or prove their theory. Saying that is not science is, I think, being kind.
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Old 03-16-2010, 08:51 AM
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...I attended a conference where one of the speakers gave a paper on (working from memory here) Nuclear Waste as a Nutritional Supplement. I wasn't able to attend that session and I can't find the proceedings online but on Monday I will see if I can find the conference CD in my office.
Didn't make it into the office yesterday but I found it today.
T.D. Luckey, A Novel Application for Radioactive Waste-as a Nutritional Supplement, Proceeding of the International Conference on Future Nuclear Systems (1999). The abstract reads:
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Originally Posted by T.D. Luckey
During the past century, 3,000 references show chronic whole body exposures to low dose irradiation improve health in living organisms. Low doses are defined as being any dose between background radiation and the threshold, 10 Gy/y (Rad/y). Excepting suicides and abortions from fear of radiation (e. g. Chernobyl), no deaths are known from low doses of ionizing radiation. Cancer mortality rates in humans, the most meaningful parameter, were recently reviewed. This paper summarizes that study.
I will not judge myself qualified to judge the thesis of the paper (which he states as: [W]e live in a partial deficiency of ionizing radiation. One remedy is to increase the our [sic] internal supply of radionuclides") other than to say that generally, I feel that the danger of low level radiation is vastly overstated in the public and mainstream media.

The delivery of this paper is, in a word, flakey. It is almost exclusively self-referenced poorly formatted and doesn't present a broad view of the topic. In short, while he makes some interesting claims, he doesn't come across as the most credible messenger.

Looking around the web I see that (what I presume is) the same author has written other books on the topic.

Possibly more useful (and, at least, a lot more expensive) would be this book.

Last edited by Threadkiller; 03-16-2010 at 08:52 AM.
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Old 03-16-2010, 05:32 PM
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Originally Posted by Neilcraig View Post
There has never been any evidence for the Linear No-Threshold theory - it was simply a bureaucratic decision because it was easy to measure & caculate which has become politically indispensible to technophobes. Since there is no evidence it is not a testable theory & thus, by definition, not part of science.

While hormesis is difficult to prove absolutely there are quite a number of unrelated pieces of evidence sdupporting it. Perhaps the strongest being the negative correlation between radon in homes & lung cancer. Note that this is a form of radiation which is not kept out by skin because it is breathed in in the air.
This appears a garbled version of Popperian demarcation.
In practice, the linear model is subject to exactly the same tests as the threshold model.* Testing one is effectively testing the other. By any sensible standards, neither is more unscientific.
Whether the data supports one or the other is another matter entirely.

* Strictly, the threshold model is open to an arbitrary reduction in the size of the threshold, hence making it unfalsifiable according to a naive Popperian. The linear model is, by contrast, effectively far more specific and hence, by this standard, more scientific.
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Old 03-17-2010, 11:40 AM
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This appears a garbled version of Popperian demarcation.
In practice, the linear model is subject to exactly the same tests as the threshold model.* Testing one is effectively testing the other. By any sensible standards, neither is more unscientific.
Whether the data supports one or the other is another matter entirely.

* Strictly, the threshold model is open to an arbitrary reduction in the size of the threshold, hence making it unfalsifiable according to a naive Popperian. The linear model is, by contrast, effectively far more specific and hence, by this standard, more scientific.
The point is that the hormesis theory has had evidence which its supporters say is good evidence to prove it. They accept it as falsifiable but not falsified.

On the other hand LNT supporters say that all evidence is statistically inconclusive & generally refuse to look at it. Since even they can produce no evidence to prove LNT they are not only taking it on trust but effectively saying no real world evidence will be sufficient to falsify their theory. Thatb is clearly not science.

eg "11 - The Committee recognised that epidemiological data relating to low levels of exposure are compatible with a range of curves describing the variation of the underlying risk with the level of exposure, including a curve that is steeper than the LNT relationship (a ‘supralinear’ curve), no risk below a certain level (‘threshold’), or even a protective effect (‘radiation hormesis’). The Committee was divided as to which type of dose–response was considered to be the most convincing description of the available scientific evidence. The member of the Committee who believed most strongly in the existence of a threshold and/or hormesis based his conclusion upon mechanistic arguments and his interpretation of the results obtained from several epidemiological studies (Rowland, 1994; Thomas, 1994; Voelz et al, 1997; Ghiassi-nejad et al, 2002; Calabrese and Baldwin, 2003; Cameron, 2003). However, most of the Committee considered that the epidemiological evidence for radiation hormesis or a threshold as the preferred risk model was not persuasive"
http://a-place-to-stand.blogspot.com...r-cameron.html
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Old 03-17-2010, 07:27 PM
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The point is that the hormesis theory has had evidence which its supporters say is good evidence to prove it. They accept it as falsifiable but not falsified.

On the other hand LNT supporters say that all evidence is statistically inconclusive & generally refuse to look at it. Since even they can produce no evidence to prove LNT they are not only taking it on trust but effectively saying no real world evidence will be sufficient to falsify their theory. Thatb is clearly not science.
Still nonsense. For instance, one can legitimately regard the existing evidence as statistically inconclusive, without remotely thinking that it is impossible that future evidence will settle the matter.
You continue to fall into the overly seductive position that just because something has no current evidence in its favour - and note that I have expressed no opinion one way or the other about whether this is the case in this instance - it is therefore somehow automatically not scientific.
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Old 03-17-2010, 08:03 PM
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How exactly did the human body adapt to background radiation? Tougher cell membranes or something?
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Old 03-18-2010, 06:09 AM
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Still nonsense. For instance, one can legitimately regard the existing evidence as statistically inconclusive, without remotely thinking that it is impossible that future evidence will settle the matter.
You continue to fall into the overly seductive position that just because something has no current evidence in its favour - and note that I have expressed no opinion one way or the other about whether this is the case in this instance - it is therefore somehow automatically not scientific.
This would only be the case if those supporting the theory had suggested some credible test which could prove or falsify their theory. Just saying I do not say there is no possibility of ever testing it but there is no possible current way of testing my theory doesn't make it actual science. Otherwise creationism, atrology & catastrophic warming, all untestable but for which proponents say there will someday be evidence, would be science.

The LNT theorists have had 65 years to come up with some testable way of supporting their claims & not only have not done so but have deliberately destroyed at least 1 experiment pointing the opposite way. In 1964 the decision was made to quietly euthanase a herd of cows exposed to a bomb test in 1946 having achieved extreme longevity (they normally live 7 years). Even the creationists don't normally destroy evidence.
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Old 03-18-2010, 07:16 AM
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How exactly did the human body adapt to background radiation? Tougher cell membranes or something?
Who says it did?

What I don't get about assertions that natural background radiation "proves" that low levels of radiation won't cause cancer is that people get cancer all the time anyway -- maybe a given individual got his from cellular damage caused by the background radiation for all we know. As far as saying that areas with more radiation not correlating to more cancers...well, we know that lots of radiation will cause cancers very reliably. Asserting that there's no correlation between increasing the dose and carcinogenesis flies in the face of that knowledge. Asserting that low levels cause some cancers, high levels cause lots of cancers, but some level in between is good for you seems....weird.
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Old 03-18-2010, 07:58 AM
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Who says it did?

What I don't get about assertions that natural background radiation "proves" that low levels of radiation won't cause cancer is that people get cancer all the time anyway ---- As far as saying that areas with more radiation not correlating to more cancers...well, we know that lots of radiation will cause cancers very reliably. Asserting that there's no correlation between increasing the dose and carcinogenesis flies in the face of that knowledge. Asserting that low levels cause some cancers, high levels cause lots of cancers, but some level in between is good for you seems....weird.
Well you answer yourself here. That areas with high background radiation have lower cancers is evidence that it doesn't cause higher cancers. Of course if there were some countervailing evidence for the LNT theory that would be worth loking at too - but the point is that there isn't.

As for your point about a very high dose killing - nobody disputes that & the LNT theory is simply extrapolating that. However there is no reason in the real world to do so. Does the fact that an elephant falling on your head will kill you "prove" the "Linear No-Threshold Theory of Headgear" that wearing a 1 pound hat has a 1/2000 chance of killing you?
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Old 03-18-2010, 09:16 AM
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As for your point about a very high dose killing - nobody disputes that & the LNT theory is simply extrapolating that. However there is no reason in the real world to do so. Does the fact that an elephant falling on your head will kill you "prove" the "Linear No-Threshold Theory of Headgear" that wearing a 1 pound hat has a 1/2000 chance of killing you?
Well, that's a misleading analogy. The one-pound hat is interacting with your body differently than the falling elephant; whereas a gamma ray from Colorado's soil is not fundamentally different from a gamma ray coming out of Chernobyl with a lot of its fellows.

A better analogy would be saying that although a minigun firing thousands of bullets per minute is certain to kill you if it hits you, a single-shot derringer can also kill you.
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Old 03-18-2010, 10:00 AM
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How exactly did the human body adapt to background radiation? Tougher cell membranes or something?
Better DNA repair mechanisms.*

A lot of the damage that radiation does to living tissue is through DNA damage. Ionizing radiation can break DNA strands or chemically alter the basis that form our genetic code. There are whole hosts of proteins that monitor DNA for various signs of damage, and then upregulate and recruit repair proteins to fix it.

On a cellular level, that's one of the potential explanations of hormesis. Basically a small amount of radiation will cause small amounts of damage. One double strand break is easy to repair -- just find the ends and stick 'em back together. Too many breaks, on the other hand, is a lot more harmful since the DNA repair mechanisms can't easily determine which broken ends belong together. After detecting this sort of damage, the cell "turns on" a whole host of DNA and cell repair responses, enough to repair the original damage and additionally repair all of the other damage (which is an inevitable byproduct of our metabolism). Potentially, at just the right dose, this can result in a positive effect through better cell maintenance without too much irreversible damage.

There are some other mechanisms that might be at play as well. Apoptosis is the process of programmed cell death, basically a self-destruct sequence. It's triggered by DNA damage as well, and suppresses cancerous cells by killing them before they go too far out of control. In some tissues, it may be beneficial to knock off the cells that are dodgy and on the edge of being apoptotic. A small dose of radation would kill off those unhealthy cells, while (perhaps) not causing too much damage to the others.

There's a lot of good evidence for these mechanisms of radiation hormesis from experiments on various lab animals and tissue cultures. Low-dose gamma radiation will extend the life span of fruit flies and round worms without causing any obvious harmful effects. It also extends life span in mice, but while causing a mix of helpful and harmful effects. Of course, you can't just take this data and assume it'll hold for humans as well. We have big bodies that last for decades with lots of dividing cells -- which means we have to deal with cancers and diseases that simple organisms rarely have. The final answer on whether radiation hormesis is beneficial in humans is going to be a lot more complicated than anything we'll see in simple lab animals.

* Although DNA repair mechanisms are present in all life forms to varying degrees, and aren't a specifically human adaptation.

Last edited by lazybratsche; 03-18-2010 at 10:01 AM.
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Old 03-18-2010, 10:12 AM
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Has anyone ever studied lab animals in an ultra-LOW radiation environment, such as the deep underground neutrino detecting sites?
This would be interesting. But I'm not sure these sites have lower total radiation; they just have less radiation from cosmic rays. There's plenty of background coming from most rocks, though perhaps some rock types and formations will have fewer radioisotopes.

An easier experiment would be to just stick the mice in a lead box. If you really wanted to go crazy, you might be able to give them food and water with lower than naturally occurring amounts of radioisotopes. But I bet that would cost obscene amounts of money, if it's possible at all.
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Old 03-18-2010, 11:01 AM
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Thanks Lazybratsche you have explained exactly why Sailboat's "analogy" which is simply to assert that the damage is indeed linear, would only be valid if there were some actual evidence that this is how it works. My point is that there isn't & the refusal of LNT supporters to even attempt to produce some shows there isn't & that it is therefore not part of science.

You are also correct about deep underground not being low radiation, quite the opposite. This is where the radon in homes comes from - natural uranium atoms spread throughout the Earth fissioning & producing radon. The presence of natural uranium & thorium is the reason why coal power plants release about 50 times as much radioactivity per kwh as nuclear ones.
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Old 03-18-2010, 11:44 AM
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Thanks Lazybratsche you have explained exactly why Sailboat's "analogy" which is simply to assert that the damage is indeed linear, would only be valid if there were some actual evidence that this is how it works. My point is that there isn't & the refusal of LNT supporters to even attempt to produce some shows there isn't & that it is therefore not part of science.
Well, the cell biology experiments that I've seen show that the damage itself is pretty linear. You can count the number of double strand DNA breaks in a cell, and they increase fairly linearly with the radiation dosage. The damage response, on the other hand, is distinctly nonlinear. So you can probably make a solid argument for a threshold at the level of individual cells. I'm not convinced, however, that this threshold will scale up to populations of humans. But I wouldn't be surprised by more epidemiological evidence to support the idea of radiation hormesis.

For the record, I think the linear-no-threshold model is probably overly simplistic as well. But it's a conservative and safe working hypothesis, so we might as well go with it for now. I'd rather we limit radiation exposure as much as practical instead of potentially allowing higher exposure. We know for certain that at some point radiation exposure is unequivocally bad.
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Old 03-18-2010, 01:45 PM
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The hormesis theory is that within limits the radiation, by stressing the cells, makes the bodies defences work (ie the damage response). This obviously only applies up to the level where the radiation is more than the body can easily repair. There is no particular reason why hormesisi should not work as well in humans as animals & plants (where it has been proven experimentally for up to a century & is not disputed). Whatever creationists & LNT supporters say we are very similar at the cellular level.

It seems likely from the history of Kerala & similar natural radioactive sites that the optimum radiation level is considerably higher than we, or indeed the people of Chernobyl, experience.
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Old 03-18-2010, 03:59 PM
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Perhaps an analogy might be a place like fictional Mayberry which gets no real crime at all, vs. someplace that gets just enough managable crime to have an experienced police force. Mayberry will not deal with a biker meth gang coming to town as well as someplace more practiced at dealing with real trouble.
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Old 03-18-2010, 06:13 PM
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Perhaps an analogy might be a place like fictional Mayberry which gets no real crime at all, vs. someplace that gets just enough managable crime to have an experienced police force. Mayberry will not deal with a biker meth gang coming to town as well as someplace more practiced at dealing with real trouble.
I dunno.

Floyd the Barber, he pack a gun.



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Old 03-23-2010, 04:17 PM
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Questionable Statistics?


For example, a 2004 study claimed more than 10,000 Taiwanese accidentally exposed for a decade or more to radioactive recycled steel used in building construction showed much lower than expected rates of cancer and congenital heart defects. The cancer rate, for example, was 3.5 cases per 100,000, compared to a normal 116

If 10,000 Taiwanese were the sample population, how was the cancer rate 3.5 per 100,000? That would mean 1/3 of one person got cancer, right? Am I math impaired or is this a totally bogus statistic?
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Old 03-23-2010, 05:59 PM
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Well I'm not sure who you are quoting but the actual case lasted for more than 20 years before it was discovered so at 3.5 per 100,000 annually that would be above 7 cases, as against above 2,320.
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Old 03-23-2010, 07:02 PM
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Well I'm not sure who you are quoting but the actual case lasted for more than 20 years before it was discovered so at 3.5 per 100,000 annually that would be above 7 cases, as against above 2,320.
I was quoting Cecil's column, which didn't say anything about the 3.5 figure being per annum. Assuming it was, though, that would be 3.5 * 10 years in the study = total of 35 cases per 100,000. Since the actual population cited was 10,000, divide that by 10 and we have 3.5 cases of cancer. Still got partial people there unless Cecil was really rounding his figures pretty wildly, no? Your figure of 7 assumes a population of 20,000 which is double what he cited.
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Old 03-24-2010, 05:37 AM
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I was quoting Cecil's column, which didn't say anything about the 3.5 figure being per annum. Assuming it was, though, that would be 3.5 * 10 years in the study = total of 35 cases per 100,000. Since the actual population cited was 10,000, divide that by 10 and we have 3.5 cases of cancer. Still got partial people there unless Cecil was really rounding his figures pretty wildly, no? Your figure of 7 assumes a population of 20,000 which is double what he cited.
As I said the actual period was over 20 years which produces the figures I gave.

Here is the actual source material for what you are discussing. http://www.jpands.org/vol9no1/chen.pdf

For an overview of the very extensive evidence for hormesis & the total acknowledgement that there is no actual evidence for the scare theory see http://a-place-to-stand.blogspot.com...hat-it-is.html
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Old 03-25-2010, 01:40 PM
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There is no particular reason why hormesisi should not work as well in humans as animals & plants (where it has been proven experimentally for up to a century & is not disputed).
Well, actually, it does seem to be disputed:
These are the first three actual articles that came up in a search for 'radiation hormesis plants' on Google.
http://www.sciencedirect.com/science...a7019e8e5098a2 ("radiation hormesis has been frequently documented, but remains in question because it is difficult to reproduce.... clearly great care must be taken when attributing such responses to radiation.")
http://jnm.snmjournals.org/cgi/reprint/32/2/350.pdf ("We findthe data in supportof most of the hormesis postulates intriguing but inconclusive.")
http://www.ncbi.nlm.nih.gov/pubmed/3553080 ("The magnitude of the effect(s) is usually small, being about 10% of control values; and the effects often are not reproducible. None has been independently confirmed.")

And I think the scientists are right to be skeptical
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The hormesis theory is that within limits the radiation, by stressing the cells, makes the bodies defences work (ie the damage response). This obviously only applies up to the level where the radiation is more than the body can easily repair. There is no particular reason why hormesisi should not work as well in humans as animals & plants...It seems likely from the history of Kerala & similar natural radioactive sites that the optimum radiation level is considerably higher than we, or indeed the people of Chernobyl, experience.
And basic evolutionary theory says this is unlikely -- Not impossible, but unlikely, meaning it's rational to require a bit more positive evidence to be convincing.
The argument, in short words, is that if a more active 'damage response' is more healthy for an organism, why haven't organisms evolved to have a higher response even before they're zapped with excess radiation?
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Old 03-25-2010, 02:26 PM
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Different articles in my neighbourhood so thanks - I will keep them to hand. However it is clear from all 3 that though they find hormesis politically inconvenient & thus wish to temporise they are aware of clear & repeated evidence.

1 - "Frequently documented" by scientific experiment & "difficult to reproduce" are clearly mutually incompatible.

2 - Quite clearly accepts the data exists eg "The High Background
Radiation Research Group has investigated thyroid
nodularity and cancer rates in the Guangdong Province
in China, an area with a natural radiation level ‘@‘3
times normal (54). For the years 1975—1978t,he high
background area had a cancer mortality rate of 36.53
per 10(5) person-years, compared to 52.85 per iO@
person-years for the control area (4). In the U.S., the
states with the three highest mean radon levels (Cob
rado, North Dakota, and Iowa) show a lung cancer
death rate of 41 per i0@,as compared to a rate of 66
per i0@in the 3 lowest radon level states (Delaware,
Louisiana, and California)" (I wasn't previously aware of the Guandong stuff)

3 - "Usually small being under 10%" is certainly an acknowledgement that it has been proven to exist. In any other field a 10% reduction in mortality would not be considered small. Lung cancer kills 1.3 million annually so clearly smoking has a much less than 10% effect on mortality which is not generally taken to mean that there is reasonable doubt of the connection.

All your links prove is the extreme disincentive among scientists to discuss a subject politicians have already decreed on when the scientists clearly know the politicians are not telling the truth.

However your last question is an interesting one - though irrelevent to the fact that radiation hormesis has been repeatedly experimentally observed it is relevent to the mechanism. If asked to guess & it is clearly only that, I would suggest that an evolutionary path that lowered the barrier to stimulation would have more than matching side effects - possibly making the immune system less effective in other areas, or likely to turn on itself or possibly making the body less able to detect other mutations. It is certainly a field in which far more research should have been done long ago. Indeed researching the not fuully understood is what scintists are supposed to do. 10% across the board for an unprocessed medicine is a lot.
  #30  
Old 03-25-2010, 06:08 PM
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I want state again that I'm skeptical of radiation hormesis myself, but there are pretty strong indications that the Linear No Threshold (LNT) hypothesis for radiation exposure is invalid.

I wonder if we have situation similar to the failure of the medical profession to recognize that most ulcers were caused by bacteria and could be cured by antibiotics. It is common for people to fail to recognize facts when there is a financial incentive not to recognize them. There was a industry that revolved around treating ulcers rather than curing them.

There is currently an industry that revolves around protecting people for low level radiation and disposing of low level radioactive waste. If those risks are in fact non-existent, then some people's Ox is going to be gored big time.
  #31  
Old 03-26-2010, 06:07 AM
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Can't argue with that Joel. Anybody respecting science must be sceptical. I think the case for hormesis to be much stronger than many things that are treated as fact though that (eg passsive smoking) is not a high standard. We absolutely should be doing, indeed should for decades have been doing, more research on it.

The LNT theory appears to have no evidential basis whatsoever, except for being another "scientific consensus", but has deprived the human race of decades of cheap power & probably of a spacegoing civilisation by now, on top of the medical costs.
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Old 03-29-2010, 03:53 PM
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By what mechanism does a small amount of radiation cause less damage than would be expected by proportion to a large amount of radiation?


Powers &8^]
  #33  
Old 03-29-2010, 08:44 PM
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Going back to the beginning of the thread, the main hypothesis is that minor damage activates a repair mechanism, but major damage overwhelms it.
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  #34  
Old 03-30-2010, 04:41 AM
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The heavily official LNT theory depends on there being no repair mechanism & thus the number of cancers is directly proportional to the number of interactions of radiation & cells. This theory predicts that large multicellular creatures with big ears & trunks will be particularly susceptible to radiation & will drop like flies. Flies won't.
  #35  
Old 03-31-2010, 05:05 PM
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Quote:
Originally Posted by Threadkiller View Post
....Nuclear Waste as a Nutritional Supplement....
That brings up comic I read years ago. "It's a proven fact that people will eat hot dogs, no matter what you put in them. This suggests an excellent method for disposing of nuclear waste."
  #36  
Old 03-31-2010, 05:56 PM
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And basic evolutionary theory says this is unlikely -- Not impossible, but unlikely, meaning it's rational to require a bit more positive evidence to be convincing.
The argument, in short words, is that if a more active 'damage response' is more healthy for an organism, why haven't organisms evolved to have a higher response even before they're zapped with excess radiation?
Not quite. Hormesis actually fits quite well with evolutionary theory. First you must realize that evolution does not select for long lifespan, but reproductive success. There's only a slight fitness advantage to living longer in order to reproduce more often. The basic argument (supported by quantitative genetic modeling) is that genes that allow an individual to age a bit slower and reproduce successfully for an extra season or two don't confer much of an advantage since that individual is likely to be killed off through a multitude of other causes (disease, predation, competition, etc). Furthermore, there's a strong link between reproductive timing and longevity. Experiments have shown that if you take a population and select for earlier reproduction, you also get shorter lifespans. The converse is also true -- select for delayed reproduction, and you get animals with longer lifespans.

How does this connect with hormesis? Well, that hits another fundamental evolutionary trade off: should I spend the resources to reproduce now, or grow and maintain my body so I can better reproduce later? In times of plenty, with good conditions and availability of food, a successful individual will reproduce as much as possible. But in harder times, that individual will have greater success by conserving resources to survive until better conditions arrive again. Hormesis is thought to be part of the mechanisms involved in sensing conditions, and allocating resources in the body accordingly.

Dietary restriction is probably the most obvious sort of example -- it's not exactly the same as hormesis, but it has a lot of shared underlying genetics. When there isn't much food around, reproduction is clearly a foolish choice, since neither the parent nor the offspring are likely to survive. So under those conditions, animals activate genetic pathways that allocate resources away from reproduction and instead to maintenance and longevity. Similar results occur from other types of stress that are known to cause hormesis.

(FWIW, I study the genetics of longevity and hormesis, using aforementioned worms.)

Quote:
Originally Posted by nielcraig
There is no particular reason why hormesisi should not work as well in humans as animals & plants (where it has been proven experimentally for up to a century & is not disputed). Whatever creationists & LNT supporters say we are very similar at the cellular level.
There are actually plenty of reasons. While all plants and animals obviously do share many cellular mechanisms, they are not the same. Even though radiation hormesis clearly extends the lifespan of worms, flies, and possibly mice, there are still plenty of reasons why this may not apply to humans. The most obvious is that worms and flies do not get cancer of any sort! Mice do get cancers, but they're not the same kinds that humans get. The underlying genetics is different enough that mice are susceptible to different sorts of cancer, and they will never live long enough to develop many of the slow growing cancers that are a major health concern for humans.

Finally, I'm not sure I understand the hostility you show towards the LNT model. We know that at some moderate radiation level, people have an elevated risk of cancer and increased mortality. Higher levels than that only increase the risk -- this is well supported by all sorts of evidence. And with background radiation, there's a certain "background" level of all sorts of health problems. It's a fairly natural assumption to interpolate between those points and say that low levels of radiation probably cause a small risk increase.

Definitive human experiments would be grossly unethical, so all we can do for now is try to look for epidemiological evidence. Which is coming along (and you've cited many good studies!), but IMO there's not evidence to state that low doses of radiation would provide a clear health benefit.
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Old 04-01-2010, 05:12 AM
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Inmteligently argued Lazybratsche. Firstly in my defence my objection is not to LNT being accepted post Hiroshima. Little information was available & it was an instance where the precautionary principle was valid. The problem is that that is 65 years ago & it has become a very official "consensus" despite a vast amount of evidence to the contrary. I came to this not through medicine but because I support nuclear power & the entire anti-nuclear scare depends on miniscule amounts of radiation being a real problem. Without this false scare we would have an enormously more developed nuclear industry. The "to cheap to meter" line is widely ridiculed by those who do not know its origin but it would not be impossible. Beyond that there is no doubt that if we had had nuclear space launches 45 years ago, as was possible, we would have a spacegoing civilisation now. It may just be my presbyterian heritage but such wasted opportunities offend me.

I am intrigued by the suggestion that the hormesis effect particularly extends life. That fits with the example of 75 cattle which were exposed to 150 rads during the Trinity A-bomb test in 1964 & kept for study. In 1964 they, or as many as remained, were put to sleep to avoid embarrassment. That would make them between 18 & 25 years old - the maximum recorded age of cattle is about 22. I regard destroying such evidence as a crime against science & humanity.

I didn't realise flies never get cancer. I guess that makes elephants somewhat more susceptible. ;-)
  #38  
Old 04-01-2010, 11:30 AM
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Thinking over Lazybratsche's words it strikes me that his definition of a moderate amount, above which radiation is dangerous is, from his experience, going to be something significantly above a normal X-Ray whereas the sort of moderate exposure I think of, in terms of nuclear, is something above 1.5 mSv a year, common natural background radiation & orders of magnitude less. Thus we have a broad agreement concealed by a common language.

Against my case it strikes me that there is evolutionary evidence that humans live much longer than would be expected of mammals like us (being able to engage in complex learning. longevity would be much more useful than for ordinary animals). If the mechanisms of longevity are already stretched by evolution it could be that humans will not benefit so much from radiation as animals do. This could perhaps be checked experimentally by comparing hormesis with lifespan in plants & animals, particularly related species with different lifespans.

Nonetheless a reduced benefit from hormesis is still a benefit & there is considerable evidence of hormesis in humans as I have linked previously.
  #39  
Old 04-02-2010, 03:00 PM
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Quote:
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I am intrigued by the suggestion that the hormesis effect particularly extends life. That fits with the example of 75 cattle which were exposed to 150 rads during the Trinity A-bomb test in 1964 & kept for study. In 1964 they, or as many as remained, were put to sleep to avoid embarrassment. That would make them between 18 & 25 years old - the maximum recorded age of cattle is about 22. I regard destroying such evidence as a crime against science & humanity.
So you're arguing that
a) the U.S. Government -- which had just invested millions in developing nuclear weapons and then millions more in researching and promoting nuclear power -- was by 1964 so set on demonizing nuclear power that it would destroy evidence of nuclear power's safety and cover it up; and
b) the U.S. Government -- the largest and most unwieldy organization on Earth -- was able to come to a single attitude about nuclear power, create a cover-up plan, and pull off the nefarious destruction of evidence (Presumably without audibly cackling, twirling its mustache on national TV, and bragging about it)?


Quote:
Originally Posted by Neilcraig View Post
I came to this not through medicine but because I support nuclear power & the entire anti-nuclear scare depends on miniscule amounts of radiation being a real problem. Without this false scare we would have an enormously more developed nuclear industry.
But then, maybe you should consider whether you're letting yourself perhaps a little bit see what you want to see. It's easy to do, and very difficult to avoid -- most of the hard work of science is figuring out how to make sure we're not finding what we're expecting and/or wanting.


lazybratsche -- thanks for your insight from someone actually in the field.
  #40  
Old 04-03-2010, 03:36 AM
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A) Government likes scare stories it keeps them in charge & remeber that the US government had all these scary nukes under their control

B) If you need moustachjes to make the scenario look silly then perhaps it isn't. Occasionally governments, even the US one, don't tell the truth.

Of course there is the risk of bias. That is why I have repeatedly said there should be research & criticised the failure to do so over the last 65 years. Thatr argument cuts both ways & where is your call for the LNT theory not being enforced until there is some evidence.
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