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I recently noticed that dying of old age is similar to a death by radiation - hair loss, weakened immune system etc. and I was wondering - Does background radiation limit our lifespan, or that of any other living creature?

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closed as off-topic by John Rennie, garyp, Ali, Qmechanic May 15 '15 at 20:28

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If this question can be reworded to fit the rules in the help center, please edit the question.

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    $\begingroup$ This is not a physics question, it's a biology question (as it is about the lifespan of human due to extraneous factors). $\endgroup$ – Kyle Kanos May 15 '15 at 16:56
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    $\begingroup$ I have no idea, and this question (and this comment) probably doesn't belong here, but a nuclear physicist once suggested to me that humans may have adapted to background radiation, and that the absence of radiation would shorten life span. $\endgroup$ – garyp May 15 '15 at 16:57
  • $\begingroup$ To quote John Muir, "When we try to pick out anything by itself, we find it hitched to everything else in the Universe." Eliminating the types of radiation which typically cause humans problems would have all sorts of unintended effects. One good example is that humans might never have evolved into existence without the genetic mutations created by ionizing radiation. $\endgroup$ – Chris Mueller May 15 '15 at 17:02
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    $\begingroup$ I'm voting to close this question as off-topic because it's about biology not physics $\endgroup$ – John Rennie May 15 '15 at 17:05
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There is some interesting data on the subject. People looked at the relationship between the prevalence of radon in counties in the US with the mortality due to lung cancer, and found a surprising relationship. Instead of the "more radon kills more people" correlation that was expected, there was an initial "dip" in the curve - as though "a little bit of radiation is good for you". This is phenomenological, so there is no guarantee of causality - but it does give food for thought. "What doesn't kill you makes you stronger." - could it be true in this case?

I refer you to this paper from which I will extract one quote:

enter image description here

and one plot:

enter image description here

Negative correlation. A little bit of radiation is good for you? Strange conclusion - but the data seems fairly persuasive.

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  • $\begingroup$ That is a very weak paper from any angle, scientific, physical and especially epidemiological. I find especially this passage laughable: "We have studied correlations between radon levels and a large number of factors, and these correlations are always too small to matter. Radon levels depend principally on geology and it is difficult to imagine how the amount of smoking can correlate with geology on a nationwide basis. Many possibilities have been considered but none can have nearly the required effect.". The paper basically ends there without ANY supporting data and no citations. LOL $\endgroup$ – CuriousOne May 16 '15 at 6:37
  • $\begingroup$ I can see that negative correlation, and that data does seem to prove it - but it's only measuring radon, right? What about other radioactive sources? (Also, if most of our radiation comes from space as cosmic rays, then I think this would be only a small insight into the idea.) $\endgroup$ – Hyperlogical May 16 '15 at 21:21
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Oh, I love this subject. The term here is radiation hormesis, and it's basically off-limits for nuclear regulators (If it's true, it horribly complicates the risk analysis for the use of any radiation source). The classic study comes from Taiwan http://www.jpands.org/vol9no1/chen.pdf where a number of apartment buildings were built using rebar that had been contaminated with cobalt-60 (accidental recycling). Figure 1 shows a quite remarkable decrease in cancer rates, with greater total dose and greater dose levels producing less cancer, with the effect lasting 20 years.

It's to be noted that the exposure in this case was external, rather than (for instance) ingestion of strontium-90 and caesium-137, which get concentrated in the thyroid and clearly increase the cancer risk.

As a matter of fact, I'm not at all sure I believe the results. They are too clean and the prophylactic response is both too prompt and too durable for me to accept easily. But they are certainly food for thought.

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  • $\begingroup$ You can put this to a test easily. Send this study to the FDA as evidence that your slightly radioactive steel bars should be considered a preventative measure against cancer and be approved as a medical device. Please don't hesitate to publish the letter you will get from the FDA in return. I am sure it will be a very fun read. $\endgroup$ – CuriousOne May 16 '15 at 6:42
  • $\begingroup$ Probably not a fun read - something along the lines of "the FDA adheres to the Linear No-Threshold model, and the supplied paper is incompatible with this." See the Wiki articles en.wikipedia.org/wiki/Linear_no-threshold_model, en.wikipedia.org/wiki/Linear_no-threshold_model for an introductory look at the issue. $\endgroup$ – WhatRoughBeast May 16 '15 at 23:17
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What Floris points to is not all that strange.

Living organisms exist in a state that is extremely far removed from thermal equilibrium, a lot of work is constantly being performed to maintain itself. So, even without any radiation, the body would fall apart on quite short time scales, were it not for the processes at work that do all the self repair work. Now, the capacity of the body to repair itself exceeds the minimum requirement to stay alive by quite some margin, so a little more or less radiation should not matter. However, when the damage that needs to be repaired is very low then the repair mechanisms may not work well. If the trigger for some mechanism to become active mis problem A but once it is at work it may also deal with problem B, then removing problem A may lead to problem B not being dealt with anymore.

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