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Dmytry comments on How to use human history as a nutritional prior? - Less Wrong Discussion
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Before cell can regulate it's DNA repair due to radiation, it has to detect the radiation, which at low levels in question (say, up to ~10x natural background, that's ~ 1..5 microsievert/hour, 2 000 .. 10 000 times less than centigray of gamma per hour) means detecting the probability before anything happens.
The issue with radiation is that people don't understand the units. You read the study you linked, you see, 1 centigray of x-rays, that's a 'low dose' they say, in god knows what context (Radiation therapy? Sure it's a low dose there). That's a 10 milliSieverts, okay? The average background dose a human receives per year, is , or 1/4 of that. Nobody's been proposing that 4 years worth of normal dose in a hour are going to still be linear.
edit: or actually, we do. We interpolate the low dose effects from the doses of somewhere around 0.1 Sv and up, based on various real world human data. Meaning that, if the effect outlined in your link is real, and there are some defence mechanisms activating at 0.01 Sv which prevent some of the DNA damage (at some other expense) - then we are underestimating the carcinogenicity of radiation at the low (near background) level, at which those defence mechanisms are not active. That is kind of scary to think about, in terms of potential extra cancer deaths.
Okay, I was misunderstanding what you were saying, and it makes sense now.
To paraphrase: Cancer risk in response to radiation levels can only be non-linear when the cell sees past radiation damage signaling it to mount a response. At low doses a given cell is unlikely to see any DNA ionization events, and therefore the risk must be linear.
That's a great point about the potential problem with extrapolating low doses from high dose data. That should really be investigated more carefully... if true "minor" radiation exposures could be a lot more risky than existing estimates suggest.
Yes. Instead what is happening, the nuclear lobby is citing studies like the one you linked as evidence of "radiation hormesis" i.e. generally beneficial effects of "low doses" of radiation (in your study the cells and the controls have to be irradiated with high dose afterwards to show any benefit; i'm very dubious that there exist any benefit versus the background), and lobbies for removal of strict EPA limits.
It gets even worse than this; the definition of Sievert and the procedures for calculating exposures of people rely on linear model - if the effects are linear then the average dose is all you need - and what the lobby wants is to use linear-model justified average doses together with threshold model, which just doesn't make sense. There literally can not be any consistent non-linear response to doses in Sieverts because the concept of dose and concept of Sievert presume linearity when it does not matter how the dose is distributed in space and time (well, up to organ scaling factors).
I've certainly seen several politicians argue that "radiation is actually good for you," but I've yet to hear any actual radiation health physicists argue that point...
Well, one doesn't usually see any actual radiation health physicists argue anything. I sure seen various engineering type people argue its good, and there are entire countries (Japan) where the linear-no-threshold model is evidently not adhered to.
Plus there is something weird going on with wikipedia articles on the subject all trying to present the pre-LNT views as something new that's challenging the LNT, complete with editing out of highly relevant historical references. Then there is "radiation hormesis", a hypothesis, that the radiation is good for you. Not "because of such and such specific response, radiation is good for you" - just a hypothesis that it is (which incidentally is the first "hypothesis" that comes up when a new exotic poison is found: someone hypothesises it to sell it in small amounts as a cure). Except that its presented as something new. Complete with a laundry list of rationalizations of how it might be so. That's terrible, and misleads people a fair lot.
I dunno if I should go ahead and write article on the topic.
Is this a fair description of the history and science behind hormesis?
See for yourself:
Is it more like some new outcome like 'ohh, there's new method by which the cell would know the radiation doses at low near background level, even for alpha particles a single of which does giant damage! Some new exciting physics discovered - the quantum probability can be measured before event happens!. That got to be useful for something, maybe for defence response. Ohh, there is the defence response, and its so strong.... I wonder if low doses of radiation are good for you?'
Or is it more like like 'okay, suppose the radiation is good for you, let's think and come up with justifications, okay, the untapped powers of organism that will be'.
The former is the process of scientific enquiry, the latter is the process of pseudoscience - start with desired effect, make up vague cause, later on perhaps think up a zillion specific causes, good luck proving them all wrong. I wonder why we even take obvious products of entirely backwards reasoning at face value as if they were not fundamentally different from products of forward reasoning?
Also try calculate how many people are required to find LNT-predicted dose effects at 10x the background. There aren't going to be direct evidence. There will be very strong indirect evidence, such as difficulty for the cell to measure doses near background, and generally low prior probability for some magical untapped powers of organism.
I have seen for myself. And I've also read about all the other hormesis effects like cold, caloric restriction intermittent fasting, exercise etc, which make a potential hormetic effect from radiation quite plausible (regardless of your sarcasm about 'magical untapped powers').
I don't think it's backwards at all.
You're a very dismissive person, I think. I give you a link with all sorts of modern results and mechanisms, and all you do is speculate wildly about ulterior motives.
It is entirely implausible that there would be a potential hormetic effect from 'radiation', because there isn't single such thing.
There's the beta radiation. There's the gamma radiation that mostly knocks off electrons (works a lot like beta, but wavelength-dependent in how the damage is delivered at cellular scale). There's the alpha radiation, that is massive, stops very quickly, and generates immense damage in a short path. That's like a hypothesis that 'fruits' are good for you, right here. Under the linear no threshold, you can bin all radiation types into one box (after you apply scaling factors). Under hormesis you can't.
You give me a link to wikipedia article with a non labelled 'graph' near top. Is it logarithmic scale? Is it linear scale? What are proposed dose values, even approximately? What is the proposed type of radiation, is it all types, is it one type, what energy range? [note that those are only abstracted out, after applying scaling factors, under linear model]
A hypothesis follows from a theory regarding the mechanism, not other way around. When different theories generate same conclusion, that's still different hypotheses, because the explanations differ. When an observation is made, it's called fact. A fact can generate multiple theories, that may generate other testable hypotheses, that would allow to discern between theories.
When a hypothesis is generated from the argument about all the other hormesis effects (never mind all the other non-hormesis effects!), which is the only explanation as of why this hypothesis would be so broad as to include all radiation types, and then multiple independent ostensibly 'mechanisms' aka theories are generated, that's called pseudoscience. Especially if unlabelled graphs are produced. A hypothesis has to be testable, i.e. possible to be shown wrong, that means the hypothesis has to specify some particular dose range, where if it is not found, the hypothesis (along with theory that produced this hypothesis) is put to rest as false. And note, the pseudoscience is not just cranks who are obviously wrong. They are non-science. Pseudo-science is something that looks like science, to anyone who lacks domain knowledge, and often, even to those who do have domain knowledge.
The key that distinguishes scientific propositions, from pseudo-scientific ones, is testability. The hormesis is pseudo-testable - you have to search over giant combinatorial space of 3 radiation types, different energies, and many orders of magnitude of doses, before you can falsify it.
It's perfectly plausible; why are you making some assumption like 'all forms of radiation in all tissues have the same hormetic effects?' Such strawmanning does you no favors.
...Which the article prominently discusses as part of the French review. Not trying very hard, are you.
So it's just as much a point against the simple linear model as it is against hormesis.
That graph is explicitly labeled as hypothetical and a visualization! Holy cow. Do you never visit Wikipedia? They use diagrams all the time to explain stuff (and not as primary source material & proof...)
You want numbers for particular setups with particular organisms, that's what the studies section is for!
/ignores naive philosophy of science and name-calling