Is exposure to small amounts of radiation beneficial?

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.

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,_Mazandaran#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_particle#Biological_effects

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.

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.

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).

Has anyone ever studied lab animals in an ultra-LOW radiation environment, such as the deep underground neutrino detecting sites?

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!

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.

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:

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.

This appears a garbled version of Popperian demarcation.
In practice, the linear model is subject to exactly the same tests as the threshold model.[sup]*[/sup] 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.

  • [sub]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.[/sub]

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/2010/03/in-memorium-priofessor-john-r-cameron.html

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.

How exactly did the human body adapt to background radiation? Tougher cell membranes or something?

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.

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.

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?

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.

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.

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.

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.

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.