How does radiation damage work?

By Ted Rockwell

A typical description of what happens when you’re “exposed to radiation” sounds scary—a gamma ray slams into a cell! Sounds like something you wouldn’t want to have happen very often.

But we are, in fact, exposed to natural radiation all the time, and about 1 percent of our body’s 100 million million cells are damaged by natural radiation and repaired every day. Any virginal, undamaged cells in our bodies don’t stay that way very long.

Radiation is the least of a cell’s problems, however. The process of metabolism—breathing in oxygen to digest our food—causes each cell to be damaged and repaired a million times a day.

Damage by a gamma ray is somewhat different than metabolic damage, but the nature of that difference is understood. Even after accounting for that difference, there is about a million times more damage from the metabolic process than from natural radiation.

A lethal amount of radiation does its job, not so much by directly damaging the cells, but by inhibiting the body’s defenses—its damage prevention, repair, and removal processes. But an important implication of this radiobiological phenomenon is that when an organism receives a small gamma dose—e.g., 1 mSv—its damage-control processes are stimulated, not only to repair or remove most of the radiation-damaged cells, but also to repair/remove the much greater number of cells that were altered by metabolism and other causes (including cancer metastases). This is the source of hormesis, the process whereby small amounts of a stressor—whether it is radiation, sunshine, exercise, heat, vaccination, or poison—actually cause beneficial effects.

There is a lot more that could be said about radiation damage. You are invited to contribute your thoughts and concerns on the subject.

For additional information on radiation and uses of radiation, see:



Ted Rockwell wrote his first published article on nuclear technology, “Frontier Life Among the Atom Splitters,” for the December 1, 1945, Saturday Evening Post. He was Adm. Rickover’s technical director during the first 15 years of the naval propulsion program, while Rickover served as director of President Eisenhower’s Atoms for Peace program.  Rockwell then co-founded the international engineering firm, MPR Associates, and the public interest organization, Radiation, Science and Health. He was the first recipient of ANS’s Lifetime Achievement Award, subsequently called The Rockwell Award. He is a member of the National Academy of Engineering and the author and/or editor of several books, papers, and patents, including the “Reactor Shielding Design Manual” in 1956,  which is still used as a standard textbook. Rockwell is a guest contributor to the ANS Nuclear Cafe.

7 thoughts on “How does radiation damage work?

  1. Brian Mays

    Oh no, David, I think that I understood you perfectly. I think that it’s clear to everyone reading these comments that you came here with the specific purpose of lobbing attacks against particular individuals (including the author of this blog post) whom you have encountered on the Internet and against whom you have harbored some sort of ongoing grudge. What’s more, you decided to do it in a rather childish way.

    The “authority that I cite” happens to be the owner of this blog, and I did not point you to the ANS’s position statement in order to contradict you. On the contrary, I was trying to help you in your quest to “get the party line.”

    Well, you got it, but given the childish attacks that you have now launched against me — a simple “thank you” would have been much more polite, by the way — I can only suppose that you didn’t like it.

    David, please grow up.

  2. David Lewis

    You’ve missed my point entirely. I said that National Academy can’t find general agreement among the relevant scientists that hormesis best explains the data that is available on what happens when humans are exposed to low levels of radiation.

    The authority you cite, the ANS, does not contradict what I said. Perhaps you should re read them and my initial comment. Your quotes, i.e. “Does not agree 100% with the National Academy”, and radiation “may tend at low levels to stimulate the body’s defences and prove beneficial” don’t show that the ANS supports hormesis as the best interpretation of all the data that exists for what happens to humans when exposed to low doses of radiation. The ANS is careful to avoid stating exactly that.

    By the way it seems odd you would refer to an authority. Judging by the way you attack independent expert panel reviews prepared by organizations such as the IPCC and the NAS, and the venom you direct at myself for pointing out at times and on differing issues what reviews such as these have found, anyone might think you insist on doing all your own science. Perhaps you should fill us all in on what authorities are not corrupt and stupid, so we’ll all know which authorities we can safely refer to without drawing you out to attack our mental health and ability to reason.

  3. Brian Mays


    You obviously have issues that are interfering with your ability to rationally discuss this particular topic with which you seem to have become singularly obsessed. If you are ever to overcome these difficulties and regain some credibility, I strongly suggest that you do not take disagreements so personally. Your comment is focused more on attacking specific people than any particular idea or concept.

    Since you have asked about the position of the ANS on the matter of the health effects of low-level radiation, I suppose that I should point you to the ANS’s Position Statement (PDF) on this topic (although, one would think that a simple Google search would have sufficed). The ANS’s Position Statement agrees with the position of the Health Physics Society that “there is insufficient scientific evidence to support the use of the Linear No Threshold Hypothesis (LNTH) in the projection of the health effects of low-level radiation.” In particular, both societies note that “below 10 rem (which includes occupational and environmental exposures) risks of health effects are either too small to be observed or are non-existent.”

    This position does not agree 100% with the National Academy of Science’s BEIR VII report, which continues to endorse the LNTH. Science is about evidence, however, not authority or consensus, which is why arguments that everyone simply fall in line don’t go very far with those who have been properly trained in how science works.

    The Background Information (PDF) that accompanies the ANS Position Statement suggests that the Society has not ruled out the possibility of a hormetic response from low levels of radiation. On the contrary, the ANS has recommended that funding be allocated to further research on low-level radiation, which should be directed at the “development of a scientifically based model that may be applied to determine the presence or absence of positive or adverse health effects due to low-level radiation exposure” (emphasis mine).

    The ANS’s Technical Brief (PDF) on the health effects of low-level radiation discusses the possibility that radiation “may tend at low levels to stimulate the body’s defenses and prove beneficial,” and it cites numerous documents from the scientific literature that support this position.

  4. David Lewis

    Advocates of hormesis who can’t understand why the National Academy of Sciences did not agree with them in any of their independent expert studies of the scientific literature who attack the NAS as corrupt or stupid should read what Bernard Cohen has to say about how likely it is that the NAS is corrupt or stupid.

    Cohen’s remarks on the NAS and the scientific literature are online in his book, the Nuclear Option, about a bit more than half way down this page

    I pointed this part of Cohen’s book out to Rod Adams, who informed me that “things have changed”.

    Now, apparently, the NAS is corrupt and stupid. I wondered how they weeded all the reputable scientists out, and especially, why they didn’t complain in letters in the scientific literature as the NAS was corrupted and only stupid morons were named as fellows.

    I wonder why Rod or anyone else who blithely tells us that scientists who disagree with them about hormesis are corrupt and/or stupid do not supply evidence of the corruption and stupidity, other than the fact that the particular scientist or scientists disagree with them on a specific issue, in this case whether hormesis is the best explanation that fits all available data about what happens at low doses of radiation exposure.

    Perhaps Ted can tell me why Bernard Cohen wrote that “most” of the information in his book came from the scientific literature and from “sources generally accepted in the scientific community”, and types like Rod say Cohen is one of his “heroes”. Whereas if I write that it really doesn’t look like hormesis is generally accepted, because the NAS, repeatedly, over many decades and many reports, has not found this acceptance in the scientific literature or among scientists, I am condemned by pro nuclear types such as DV82XL, as an “anti nuclear zealot” for the crime of believing that the NAS and the scientific literature are about exactly what Cohen wrote that it is.

    Its hard to sort things out – so I thought I’d come here to headquarters and get the party line I could parrot it everywhere I go.

  5. Bobby Scott

    Those who are unaware of the abundant data showing hormetic effects of low doses and dose rates of sparsely ionizing radiation (called low-LET radiation) may find my presentation titled “Radiation hormesis and life—mild radiation stress makes you stronger” to be of interest. Both the video and pdf of slides presented are available at the following website: .

  6. Jerry Cuttler

    Of course, you may believe whatever you like. We know that it’s very difficult to “prove” anything; however, it takes only one “ugly” fact to disprove a beautiful hypothesis. And there there are hundreds of measured facts that disprove the LNT hypothesis of radiation carcinogenesis and suggest hormesis. You could start by reading my commentary on LNT, available at

  7. Joffan

    I regard radiation hormesis as plausible but not proven. The effects, if any, are subtle and fall under the same difficulty as demonstrating an adverse effect from low-level radiation. The default position, in the absence of across-the-board evidence one way or the other, is that low-level radiation has no effect. Unfortunately, the world’s radiation health community disagrees with me on the correctness of requiring evidence to assert an effect, and so protection measures down to foolishly low levels of radiation continue to be applied, including the outrageous proposal to continue the displacement of thousands of Japanese people on the basis of this lack of evidence, even after the immediate threat of further significant fallout from the reactors has passed – as it almost has now.

    The warning bells on the status of the linear no-threshold (LNT) model ring loudly when an adjustment factor appears (DDREF) which only takes a variable effect at low levels. By adjusting this number the no-longer-linear model can be protected from being disproved – although anyone paying attention to the actual results, or to this piece of mathematical wriggling, knows it has already fallen, and that zero is a satisfactory fit to the amount of harm below 100mSv.