1. Unfortunately many inexperienced individuals are heavily influenced by ex-medical professional Helen Caldicott who is a world famous anti-nuclear activist – and a very successful one too!

    Helen firmly believes and often states that “no dose of radiation is safe, however small”.

    If you accept this, then yes CT scans and x-rays are inherently unsafe. If there were accepted epidemiological studies that showed that CT scans did more harm than good then we would have been forced to abandon them decades ago.

    I find it bitterly disappointing that someone with Helen’s education could not see the falsehood in her propaganda. But I suspect the hole she has dug for herself is too deep to climb out of now.

    1. Yes, Helen fell into a trap. She started to believe her own propaganda and became even more self-sure, shrill and dogmatic. After decades constructing this facade, it is impossible to walk it back without a total loss of face and credibility, so the only option is to double down on her nonsense.

      I think there is a valuable less here for all of us. Stay humble and always make your ego and opinion subordinate to the data. Temptation is great to believe the narrative of one’s Greatness ordained by Providence, except that it is usually self-delusion propelled by arrogance. Humility and a hard-nosed dedication to the facts are vital if one is to be taken seriously and make a difference over the long haul.

      If the facts point in a new direction, you must be able to admit it and change course. Al Gore and his position on nuclear power is another example of this phenomena…

      1. Fully agree. This counts for pro-nuke activists too. Speaking for myself, I am regularly called a ‘true believer’ by my opponents because I push the pro-nuke case (too?) hard. While I am careful to always remain within the limits of what I sincerely believe to be supported by scientific fact, I have found myself uncomfortably close to the edge a few times. This happened due to a combination of not having enough knowledge (there is always more to learn, especially for someone like me who came in late to nuclear science and technolog) and due to being the often outraged witness of the complete lack of dedication to facts displayed by most if not all anti-nukes, which makes it tempting to get sucked onto the deceptively easy highway of fact-free, gut-feeling advocacy.

  2. It will be interesting to hear what my doctor has to say, next time I see him, when I ask if I can get a dose of whole body gamma radiation as a ‘tonic’, keep the old imune system in top form. Wonder if he might know the optimal exposure values?

  3. In Wade Allison’s highly readable book “Radiation and Reason” there is a relevant part on the health impacts of radiotherapy with beam radiation. It is shown that cells’ reaction to such radiation exhibits a strong threshold response, whereby cells close to the tumor which receive up to 70% of the radiation dose survive intact, which the cells in the tumor receiving 100% of the radiation are all killed. That part of the book really illustrated for me how large the difference between dangerous and safe radiation doses really appear to be, at least concerning deterministic effects. Of course, it is the more complex (and thus easier to misrepresent) stochastic effects which anti-nukes mostly latch onto to bolster their FUD production…

  4. Modern equipment is routinely able to keep doses down to the 1 mSv range in cardiac and pediatric scans, and below 10 mSv on average.


    It seems the medical community (and health care providers) have responded correctly to some of these issues concerning dose and elevated risk, and attempted to minimize unnecessary scans, perhaps costs as well, and improve health outcomes at the same time. As suggested in a widely cited review article here:

    There is a considerable literature questioning the use of CT, or the use of multiple CT scans, in a variety of contexts, including management of blunt trauma, seizures, and chronic headaches, and particularly questioning its use as a primary diagnostic tool for acute appendicitis in children. But beyond these clinical issues, a problem arises when CT scans are requested in the practice of defensive medicine, or when a CT scan, justified in itself, is repeated as the patient passes through the medical system, often simply because of a lack of communication. Tellingly, a straw poll of pediatric radiologists suggested that perhaps one third of CT studies could be replaced by alternative approaches or not performed at all.

    For those who are need of such scans, I see no health basis to suggest they should not be given one. But to give such scans on a general basis, simply to pay off the equipment, protect the doctor, or rack up costs … there appears to be little benefit to improving health outcomes, and pretty consistent evidence from other contexts (as suggested from above) that health risks would be elevated in such instances (particularly in cases where older equipment is being used, and doses range in the 30 – 90 mSv range for just two or three scans).

    We seem to be trending in the right direction on this one (towards lower doses) and not towards higher doses (and uncertain scientific evidence to suggest and give cover for unnecessary scans, higher costs, and perhaps even worse health outcomes than equally effective alternatives).

  5. There is also the World Health Organization’s World Cancer Report 2014 in the news today. It says that radiation from medical scans is a major source of cancer.


    I have not read the report but I would guess its conclusions are based on estimates generated by Linear No-Threshold models.

    1. Radiation (both from the sun and medical scans) is 5th on a list of 8 major sources of preventable cancer. The top 4 are Smoking, Infections, Alcohol and Obesity and inactivity.

      A news report like this might scare some away from medical scans. A challenge for the medical profession no doubt.

  6. They selectively cite two recent studies of children who received CT scans, both of which claim to observe increased cancer rates, which the authors claim is due to radiation from the scans.

    I wouldn’t mind getting a reference for the two studies they are citing here.

    The first one appears to be this:


    Authors suggest the case control study is forthcoming (here).

    The second appears to be this one:


    Which does include comparison with a control population (those who did not receive CT scans). In addition, age based groupings for dose estimates were as follows: “newborn; 1, 5, 10, 15 years; adult” (p. 2). They also utilized a scaling factor in some instances. Might they be talking about a different study?

  7. “They selectively cite two recent studies of children who received CT scans, both of which claim to observe increased cancer rates, which the authors claim is due to radiation from the scans.”

    Maybe x-rays aren’t the choise for beneficial radiation then? Numerous studies on those exposed to gamma radiation (from Cobalt 60) show less cancer and less chronic illness, and the numbers are well above any chance of statistical errors. The numbers for the excess cnacers from x-rays seem to be so small as to possibly be statistical error though. If I were seriously looking at getting irradiated for health reasons, I think I’d try and reproduce the type and levels or radiation experienced by those who live in regions with the longest-lived residents.

    1. You don’t give a head CT scan to a kid without a serious reason. This means that given that the excess is really small in absolute, some correlation between medical conditions that require a CT scan and cancer is a likely explanation (more than just statistical error).
      In the Australian study, they tried to avoid that, but it’s very hard. The study would be much enhanced by including what was the initial condition requiring the CT scan. They say they eliminated cancers occurring shortly after the examination, but I fail to see why radiations would be the only factor that has a long latency period (given what we know today about DNA, radiation cancer are most likely caused by defective DSB repair, but most other carcinogenic factors are also linked to defective DSB repair). They also say they found a link with the number of CT scan, but again more serious conditions also probably mean repeated CT scan.

      It would be more convincing if they could find a reduction after the hospital switched to a more modern machine with lower exposure. Especially if it still can be shown for two comparable hospital that didn’t receive the newer equipment at the same time.
      This kind of correlation and control has already been used to show a negative link between high speed Internet access and the number of rapes (more Internet results in less rapes).

  8. Stress is a cause of cancer and disease (and depression and substance abuse and an unhealthy lifestyle) all by itself.

    Tell patients who get CT scans that they risk getting cancer often enough, and I’d think it’s quite possible that their stress levels increase by just the right amount for anti-nukes to be able to document the resulting increase in cancer and other disease that they like to see.

    It would be interesting to see a study where a control group of patient is told they’ve recieved a CT scan which increases their risk of cancer, while in fact they received no such scan. I wonder if that control group would also show (barely statistically significant) increases in cancer or other diseases. Going further: have another group get actual CT-scans but tell them that their chances of getting cancer may now well be reduced due to hormesis effects, and see how that group does afterwards compared to the group who is told they run an increased risk of contracting cancer due to the scans they recieved. I wonder.

    At the very low radiation doses and expected health effect of CT-scans, stress is a powerful confounding factor, I would expect.

    1. @Joris van Dorp

      I wonder if similar effects can be induced into a population of 94,000 people who were near an atomic bomb blast and have been told repeatedly during a period of more than 60 years that their experience has increased their risk of contracting cancer?

  9. The NY Times Op-Ed “We are giving ourselves cancer” does not represent current state of knowledge in this field, and makes many misleading statements. I have presented a line-by-line criticism of the article in my blog which is available at:


    CT scans are safe, and the present concerns regarding radiation dose from CT scans are not justified by any evidence.

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