One thing I did not see mentioned in the article, and which seems to never make it into most articles about the risks (or hypothetical benefits) of radiation exposure, is the massive amount of information we have about the effects of radiation from radiation oncology. Six times as many people as were exposed at Hiroshima are irradiated on purpose in the USA alone every year. And the radiation is actually measured and planned. So Hiroshima is so far from our largest or best data set it is funny. I don't have numbers, but I'm willing to bet that more patients have had radiation treatment for non-cancerous diseases than exist in the Hiroshima cohort.
Epidemiology isn't one of my specialties, but radon and radiation measurement actually are. I'm skeptical about the radon baths, simply because that is NOT a low level of radon, in the sense of a statistically uncertain long-term hazard level. A typical radon bath is in the thousands of pCi/L, which is about a thousand times higher than the level at which mitigation would be required for health reasons for a dwelling. However, the amount of time spent there is low. So, it is like having a non-smoker smoke a thousand cigarettes all at once, instead of over the course of a year. Might that kick-start something in their body? Certainly, but it does not fall under the normal hormesis rubric. And alpha particle damage tends to be high and localized.
Paracelsus said the dose makes the poison, which is true. But in addition, time makes the dose. I have no problem drinking 100 liters of water over a few months, but that would be a fatal dose in an hour. More attention needs to be paid to the time component of radiation dosing and threshold effects.
Radiation oncology treatments usually focus a high dose on a single small area during a series of short time periods. So I think it would be difficult to draw any conclusions from that about the likely effects of low-dose whole body exposure over longer periods.
Radiation therapy treatments are almost always fractionated, meaning the total dose prescribed by the radiation oncologist is spread fairly evenly across multiple days, typically 25-38 treatments for most disease sites. And since patients are rarely treated on the weekend, it usually takes 1 to 2 months for a patient to complete treatment. I don't know that I would consider 1 to 2 months a short time. There are some exceptions, such as gamma knife for brain cancer, in which the entire prescribed dose is delivered all in one session.
Also, radiation therapy is often used to treat not-so-small areas (volumes). For example, mesothelioma cases often require irradiation of the entire thoracic cavity. And if that isn't a big enough target for you, well, total body irradiation is actually a pretty common modality for certain, less localized, cancers originating in the blood and bone marrow. Both external beam irradiation (for mesothelioma) and total body irradiation treatments are always fractionated, generally delivering no more than 2 Gy to a patient in a single day, to give healthy tissue time to recover between fractions. Having said all that, you are right that this is still quite unlike the conditions presented in the article. Perhaps you would prefer studies analyzing the increased exposure of long-haul international airline flight crews.
You cannot focus the radiation field perfectly. The whole body will be subjected to (non uniformly distributed) dose of maybe a permille of the reference dose in the irradiation center: there is both leakage from the treatment machine and scattered radiation from within the patients body.
Given that a typical treatment will be about 50Gy (distributed over many fractions), my estimate is for a few ten mGy (mSv) in total to almost every part of the body outside of the direct beam.
(I'm building dosimeters in my day job and work on medical accelerators all the time.)
Chest x-rays for example dose lots of tissue. CT scans are significantly 100-1000x higher than that and well above whole body average annual radiation exposure. https://en.m.wikipedia.org/wiki/CT_scan
Chest X-rays are a minuscule dose. They are in a similar realm to the dose you get from a long distance flight or 2 - especially if you eat bananas while you fly.
Cardiac CT, chest/abdo/pelvis and PET scans are dose order of magnitude greater though.
I'm not so sure about that. As a general rule, we don't expose healthy people to large amounts of radiation; so it's hard to separate the effects of the radiation from the effects of whatever caused them to be irradiated.
That depends. Flight crew (pilots and cabin crew) do receive significant radiation. They are a great set to study as they are generally much younger and healthier than the average medical imaging and/or oncology patient.
Indeed, they're a very interesting exception to the general rule about healthy people not getting significant irradiation. Pilots in particular could be a useful group to study given that they have mandatory medical checks; however, I'm not sure that the sample would be large enough to yield any statistically significant results, even if the privacy issues could be circumvented.
(Also, you run into socioeconomic confounders: Can you find another population which has both the same irregular schedules and the wage scales of pilots?)
You're right, mostly. Considerably more data has been obtained from the fields of radiation oncology and medical physics about the effects of radiation on the body in the time since WWII. The main difference, I would argue, is that the article (as you also mention) is talking about alpha particle radiation. Most radiation oncology data comes from x-ray, gamma ray, and electron modalities. Heavy ions, including alpha particles, affect tissue rather differently. There is, however, a growing amount of data available from proton therapy and carbon therapy modalities.
Epidemiology isn't one of my specialties, but radon and radiation measurement actually are. I'm skeptical about the radon baths, simply because that is NOT a low level of radon, in the sense of a statistically uncertain long-term hazard level. A typical radon bath is in the thousands of pCi/L, which is about a thousand times higher than the level at which mitigation would be required for health reasons for a dwelling. However, the amount of time spent there is low. So, it is like having a non-smoker smoke a thousand cigarettes all at once, instead of over the course of a year. Might that kick-start something in their body? Certainly, but it does not fall under the normal hormesis rubric. And alpha particle damage tends to be high and localized.
Paracelsus said the dose makes the poison, which is true. But in addition, time makes the dose. I have no problem drinking 100 liters of water over a few months, but that would be a fatal dose in an hour. More attention needs to be paid to the time component of radiation dosing and threshold effects.