Thursday, April 14, 2011

A useful analogy: Radiation and Temperature

In an attempt to explain the dangers - real and merely perceived - of radiation, I propose the following analogy: radiation and temperature*.

1. Radiation, like temperature, can cause immediate damage to a living being, but only if it is sufficiently "hot."

2. Some places on Earth are warmer than others, and some colder. But that temperature difference doesn't create differences in cancer rates (you're not more likely to get a tumor in Fort Lauderdale than you are in Omaha, Tacoma or Duluth). Similarly, some places on Earth have more natural radiation, and some less, but this difference isn't significant enough to affect us.

3. A small rise in temperature, even when sustained, isn't likely to cause us any damage. In fact, we hardly notice it. Same goes for radiation; if we're exposed to 300 mrem in a year or 400 mrem in a year, we won't notice, and the change isn't likely to hurt us.

4. There are natural "sources" of temperature, and man-made sources. We can locally raise the temperature (by lighting a fire or turning on the heater), but when taken in the context of the universe, it's hardly a blip on the screen. Similarly, we can create local sources of radiation (nuclear weapon, nuclear accident), but they too are minuscule in the grander scheme of things.

5. Temperature is not dangerous when it is understood and controlled. Neither is radiation.

*Microwave and infrared EM radiation, which are direct causes of temperature increases from the vibration of molecular bonds, are, in fact, radiation. So the analogy obviously has some weakness to it, just like all analogy and metaphor - they can only go so far. But I'm trying to convey information about what people think of when they hear the term "radiation," mainly, ionizing radiation, or, incorrectly, radioactivity. If the terminology is bothersome, substitute your own: "radiation" could be replaced with "release of radioactive materials" or similar. For the purposes of the analogy, decouple any effect which certain forms of radiation have on temperature, and pretend they're independent.


  1. Radiation is dangerous, unless you subscribe to some kind of homeopathic theory about the beneficial effect of low doses. For instance, environmental exposure to radon causes a lot of lung cancer. We are surrounded by radiation, and we have built-in mechanisms to mitigate the risk (DNA repair), but that doesn't make it OK, even at low doses.

  2. We don't know how dangerous radiation is at low doses. The linear no-threshold (LNT) model is highly conservative in this respect, which is why it's used for safety standards. However, it's important to note that we, as examples of life on Earth, evolved in a bath of radiation - in fact, when life first appeared, the natural background radiation was much higher than today. So we've evolved to be able to handle background radiation, which can vary widely... meaning we've probably evolved to withstand the highest possible background.

    As for radon, yes, it can be dangerous, but this relates to my point #5. Radon is dangerous because it's a gas, and we inhale it, thus getting the radiation damage internally (to soft tissue). But if you take steps to mitigate radon exposure (just like you'd wear sunscreen or a hat), then it's not so dangerous.

  3. Hi, Kelly-

    Yes, it is an interesting topic, that low doses might be protective if they stimulate more error-correction gene induction than the extent of the damage. I am aware of that kind of low- dose nonlinearity theory.

    But on basic principle, the fact that we evolved in a radiation atmosphere and "deal" with it biologically doesn't alter its damage.. that radiation, along with many other chemical insults, cause mutations which give us evolution in the first place.

    The question is whether we want to put up with more mutations or not. Generally, -not- is the prudent choice. The way of dealing with radon, for instance, is to remove it... by ventilating the basement, etc.

    So, I don't want to make a capital case out of it, but just say that while hysteria is unwarranted, so is a blase attitude of .. ionizing radiation and radioactive materials in the environment are OK and not so bad.

  4. It doesn't seem like Kelly said that there was no danger to radiation - just that the risks become small and manageable at low levels; that's why heat is an appropriate analogy. Heat has benefits, but it can also be fatally dangerous. The point is, we don't get up-in-arms over temperature, and act like school children who hear the rumour that one of them as got the lurgy, every time it is mentioned.

    Kelly's analogy with temperature (while self-acknowledged to be limited in scope) does communicate some extremely important points:

    1) That radiation is occurring naturally everywhere, and is something to be understood as an intrinsic part of life, the universe and everything (the idea that we can somehow eliminate radiation exposure is not even worthy of discussion). The public do generally have a perception (despite what concepts they're told) that man-made radiation is the dominant source, and thus radiation (and nuclear power) has the connotation of science gone wrong (or a-step-to-far). [It would be interesting to know what the public attitude to radiation would be if no nuclear weapons had ever been detonated. I suspect for many people there's a subconscious association between all radiation and the image of a mushroom cloud, as they have no other available percept for it.]

    2) The contribution to the level of radiation by human activity must be seen in the light of this - as a percentage change to the natural level in a particular area.

    3) Like heat, radiation is a useful tool. One can list a few obvious examples immediately: medical diagnoses, medical therapy, energy production, airport security, materials analysis, carbon dating, etc. Of course, there are associated dangers, as there are with building a fire (but the benefits to our lives from warmth and cooking is worth it!). In the case of radiation, energy production, improving our health, our safety, inspiring a deeper understanding of the world, or the spiritual benefit of living somewhere beautiful (like Cornwall or Colorado, which have higher naturally occurring radon) - far outweigh the risk of burning one's hand occasionally.

    4) That by understanding radiation, it can be "handled", quite routinely, in such a way as to minimise the risk to an acceptable (even negligible) level. A pair of tongs are developed to make fire-use safer; the list for radiation is almost endless.

    The point about the acceptability of the effect of radiation on the human body is sufficiently complex, and couched in personal and societal perceptions of the world at the most fundamental level, that I will leave it to an independent comment.

  5. Burk, I do not wish to be blase... I want people to have a healthy respect for something that could possibly harm them but in all likelihood won't. People generally exhibit the appropriate response to things like heat or cars or other, more familiar things... radiation isn't so scary that it warrants a phobic response. It has been generally observed, on the scientific side, that (with regard to cancer and mutations), radiation is a much weaker carcinogen than previously thought. So in "putting up with" a slight increase in background radiation, you're not also putting up with a definite increase in mutations.

    On a personal note, I don't subscribe to either the LNT model (though I approve its use as a basis for safety measures, since it's the most conservative) or the hormesis model (that low-dose radiation is really beneficial). I stand somewhere in the middle with the threshold model, which roughly states that the biologic response to ionizing radiation is no longer linear below a certain level, but instead that the effect is, in fact, lessened. There is lots of experimental evidence for this model out there (see for example), but like I said before, there's still not enough data to decide definitively.

    To the Evil Doctor, your side note about weapons touches on the reason we refer to "atomic bombs" and "nuclear power." It was known that referring to both with similar terminology would be damaging to the peaceful uses. It would appear that the differentiation in terms didn't help much, though.

    I'd like to make a quick point using personal anecdote, so bear with me. My house sits in between an old weapons plant (full of uranium contamination) and a coal-fired power plant, near a lake. I worry far more about fly ash from the coal plant or chemical spills into the lake from the train that services it than I worry about fission or decay products from the high levels of uranium. Why? Because I know that the fly ash and the chemicals are far more dangerous. Even so, none of these dangers warrant constant, mind-warping worry that characterizes the public's response to radiation.

  6. Hi, Call me a nincompoop but can you answer a slightly OCD type question? Can an item from the Chernobyl region at the time of the disaster for example be radioactive enough to cause adjacent items to become radioactive and for that radioactivity to pass to other items? Or am I right in thinking that the neutron activation would need much higher energy to do this.

    1. It is possible for something to be activated by incident radiation - this is why the interior components of a reactor vessel could still be radioactive when the reactor itself is shut down. A high flux of neutrons, gamma rays or even charged particles can induce radioactivity in something that would otherwise be completely stable. But you're right, it takes a lot of energy and a lot of intensity in order for this to happen. And the things that are the most likely to become activated are the things least likely to get out of a reactor (even with an explosion, like Chernobyl, heavy fragments of activated material are not going to travel far; it was the release of material that could become airborne that was the real problem).
      So to go back to the analogy, yes, it's possible for things to get "hot" by being near other things which are "hot," but they have to be in close proximity, which means they're also going to be contained. I hope this helps!


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