I keep hearing that no amount of radiation is safe. Now this document says that some of it is. Which is it?
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I keep hearing that no amount of radiation is safe. Now this document says that some of it is. Which is it?
Low levels of radiation exposure are safe. The exposure does carry some risk, and the level of risk is the same or less than other day-to-day activities we consider safe or acceptable.
Whether something is truly safe is based on how each individual sees it. Every day we face risks of various sorts without much consideration. The reason? The risk is so very low that we just don’t think about it or the risk is something we are willing to take because of benefits we see (like driving your car or walking across a busy street). It is the same with a dose of radiation. When the calculated risk from radiation exposure is the same as risks we routinely take and consider acceptable, we then say that amount of radiation exposure is also acceptable.
It surely depends on the amount or strength of the radiation. It is analogous to poisons. Any substance can be taken safely if it is sufficiently dilute.
Please identify the document.
The linear, no-threshold (LNT) model for protection from ionizing radiation is a simple, unconfirmed model. As a model it admits to harm at any amount. The claimed risk is low dose and low dose rate caused cancer. This is the only risk modeled by the LNT. There are no data that support this model. It is assumed as a basis to formulate radiation protection.
Nothing ever is 100% safe. In this sense, you may say (following LNT model) that any amount of radiation causes a risk. In practice, you should always relate this risk to other risks to judge whether it is acceptable. Or to the risk you can not avoid by any means. Your body itself radiates (mainly C-14 and K-40). Strictly, you may consider this as a (very low) risk, but what can be the consequence?
Erik Strub
The LNT purports to be a risk model for cancer induction from human dose from ionizing radiation at low doses. It is not an actual model of dose effect. Claims are made that it could be true, because the data do not refute it. The data certainly do not support it. Risk is claimed, because it can be calculated. A risk of 1 over Avagadro's number can be calculated. That could mean it is not 100% safe. Even if the LNT were true, there is a point where the risk is so trivial that 'safe' is the answer. Compare a risk of 1 in 1000 to 1 in 4.
What is "safe"? This concept is not defined in my scientific textbooks! There is no scientific answer to the question if the meaning of "safe" is not defined.
"Safe" cannot mean 0% risk. Does it mean "much less risk than other accepted risks", or "comparable to other accepted risks" ?
The risk of radiation itself is accepted at a level that is far from negligible. We do not worry about natural radiation (except radon) at a level of ~1 mSv/y. We take airplanes, we go to the mountains, and we do not choose systematically sandy soils for our home. We also accept medical radiation at a comparable level on the average, just trying to avoid useless expositions.
According to your own definition of "safe", you could set the safety limit at 0.1 mSv/y or 1 mSv/y. Less than 0.1 mSv/y would be difficult to justify.
There are good reasons to establish a better protection to the fetus, also to the babies, and to accept higher expositions for old people. People exposed to other carcinogens (smokers ...) would also have good reasons to avoid ionizing radiation.
It mainly rely on the strength of the radiation, also keep in mind different organ of the body responds differently to the radiation!
François Tondeur
You stated,
"The risk of radiation itself is accepted at a level that is far from negligible."
What level is this?
While the health effects of moderate and large doses of radiation of any type are easy to observe, the effects of low and micro-doses are not immediately obvious. Statistical extrapolation into unmeasurable consequences are often a blind trip into the unknown... after all there are background radiation levels we are all exposed to that cannot be controlled for.
Dear Joseph Alvarez
I mentioned 1mSv/y natural + 1 mSv/y medical as a level of effective dose against which no action is undertaken (the actions undertaken in the medical field try to stop the continuous increase of the mean medical dose, not to go back under this value).
To translate this into a cancer risk cannot be done in a reliable way, for the reasons you mentioned in your contributions to this discussion. The LNT hypothesis can however give a possible order of magnitude , although the absence of effect cannot be totally excluded. 2 mSv/y means 150 mSv per lifetime, which leads, with the usual risk factors used with LNT, to a lifetime risk of cancer death between 0.5% and 1%. This order of magnitude is not negligible. It can be compared, for example, to the death risk associated with the traffic on the roads. The difference is of course that the risk of the traffic is well documented.
It should be noted that , for indoor radon, the existence of the cancer risk is established for yearly doses that are not much higher, maybe a factor 2 or 3 (the conversion of the exposition to radon into effective dose is itself controversial), certainly for smokers.
François Tondeur
The lifetime cancer risk is 20 +/- 5 in cancers in 100 (variously reported). The 150 mSv (LNT) risk is 1 +/- 2 cancer in 100. A risk increasing from 20% to 21% appears worrisome (5% increase.) Nevertheless, 1 +/- 2 is a useless number. The actual uncertainty is much larger.
The cancer risk for radon at current action levels has not been established.
Joseph Alvarez:
Does your calculation mean, you would accept any (calculated) risk up to the point when it is significantly measurable? Taking your numbers, about 1500 mSv (lifetime) would maybe yield a quantifiable enhancement of risk, increasing cancer risk to maybe 30 +/-5. This corresponds to a dose limit of 20 mSv/a. Would that be acceptable in your view?
Joseph Alvarez,
I do not think that it is correct to write that the cancer risk for indoor radon at current action levels has not been established. Depending on the country, the action level can vary from 150 Bq/m3 to 800 Bq/m3. The EU level is presently 300 Bq/m3.
The European pooled study of lung cancer due to residential radon by Darby et al. (2005) was summarized in the WHO radon handbook, as follows:
" In the European pooling study, the exposure-response relationship appeared to be approximately linear with no evidence for a threshold below which there was no risk.In particular, the results were incompatible with a threshold above 150 Bq/m3 (i.e.150 Bq/m3 was the 95% upper confidence limit for any threshold). Furthermore, the investigators found a statistically significant association between radon concentration and lung cancer, even when the analysis was restricted to people in homes with measured radon concentrations below 200 Bq/m3. The risk of lung cancer was 20% higher (95% confidence interval 3-30%) for those individuals with measured radon concentrations 100-199 Bq/m3 (mean: 136 Bq/m3) when compared to those with measured radon concentrations under 100 Bq/m3 (mean: 52 Bq/m3)."
François Tondeur
Here are the conclusions from Darby
"We were able to assess directly the risks from residential radon because our study involved large numbers of individuals with lung cancer and large numbers of unaffected individuals, all with detailed smoking histories. People with higher residential radon concentrations tended to smoke less, so that assessment of the magnitude of the risk associated with radon required detailed stratification for smoking history including amount smoked and age for current smokers, and years since stopping smoking and amount smoked for ex-smokers. Such detailed stratification has not previously been possible. Correction for the bias introduced by random uncertainties in the estimation of individual residential radon concentrations was also important.
After stratification for smoking there was strong evidence of an association between residential radon and lung cancer. The dose-response relation seemed linear with no evidence of a threshold, and a significant relation remained even among those whose measured radon concentrations were below 200 Bq/m3."
There were claims of statistical significance in some of the modeling, but no claims statistical significance in the risk. As you see, 'strong evidence of association' is asserted and the dose response 'seemed' linear.
I stand by my statement.
Note: No actual dose response relationship was established in the miner studies. The dose data were insufficient to assign dose to individuals or groups. Doses were assumed based on few measurements. The largest group of miners had only one measurement.
I do not claim there is no risk from radon. I claim we have no basis for calculating risk.
As we live in a world where elimination of radiation from the ground and from space is impossible and the amount varies depending on type of soil/rock and altitude it would seem inevitable that exposure to low doses is acceptable. In the UK the average dose from natural sources is about 2.7 mSv but higher doses, due to radon can be a factor of about 3, depending on lifestyle and geography, with no significant effects noted.
In the rest of world the variation is even greater.
The highest dose recorded is in Ramsar in Iran at 131 mSv. Epidemiological studies are underway to identify health effects associated with the high radiation levels in Ramsar but it is much too early to draw unambiguous statistically significant conclusions. However, the recent statistical analyses showed that there is no correlation between the risk of negative health effects and elevated level of natural background radiation. While so far support for beneficial effects of chronic radiation (like longer lifespan) has been observed in few places only, a protective and adaptive effect is suggested by at least one study whose authors nonetheless caution that data from Ramsar are not yet sufficiently strong to relax existing regulatory dose limits.
So negative effects of low levels of radiation are more or less discounted, positive effects, known as hormesis may suggest exposure to low levels is beneficial.
Sleep easy!
Erik
I assume your 30 +/- 5 is 20 + 10 and a propagated uncertainty of 5 from +/-5 and +/-2. If so, the uncertainty of the 10 is +/- 20 so you should propagate +/- 5 and +/- 20. The relative risk models presented for radiation risk show the uncertainty to be proportional all the way to zero. This is grossly incorrect. The uncertainty increases with distance from the mean on a regression model.
I do not understand "Does your calculation mean, you would accept any (calculated) risk up to the point when it is significantly measurable?"
The original question concerned (my understanding) extrapolating to zero risk. I was responding to an answer that said 1% lifetime risk was important. Adding 1% to 20% might be important if you are certain of both quantities. When a quantity is more than 100% uncertain it should not be added to another and definitely not propagate the uncertainty if you did.
Joseph
The starting point was the question "is there a safe radiation level". I think we both agree that there is a factual safe level, i.e. a level of radiation that is acceptable because we can assume that the risk can be assumed as small compared to other risks. My question is, which would be this level (in mSv) in your opinion?
Erik,
the average natural effective dose, because we all live and stand it since eternities.
A H Korner,
I know very little about radiation, and understand even less.
However, so far, the discussion seems to have centred around the carcinogenic potential of ionsing radiation. In fact ionising radiation is part of a spectrum of electromagnetic radiation, ranging from gamma rays to radio waves.
The potential for harm depends on the amount of radiation, type of radiation, duration of exposure, and which part of the body is impacted.
I always get the difference between stochastic and non-stochastic effects mixed up. Some of the harmful effects of ionising radiation, such as burns, do have a threshold, whereas others, such as carcinogenic effects may not have such a threshold, but the chances of developing a malignancy diminishes with the dose.
On the other hand, non-ionising radiation, such as ultravolet light, can also cause both skin burns and cancers, such as melanomas, and basal cell carcinomas.
Bw
Chris Ide
Erik Strub
You asked for my opinion of a safe level in mSv. I have no opinion in terms of Sv. Sv is for stochastic effects at low doses (undefined) and low dose rates (undefined.) It is this lack of definition that leads to 'no amount of radiation is safe.'
The question of safe must include dose and dose rate. Lifetime dose at a low dose rate (within an order or two of background rate) likely has no meaning. The nuclear worker levels are conservatively safe.
Joseph Alvarez
That is an interesting position. I understand many of your arguments. However, it is always little unsatisfying to critisize the "no amount of radiation is safe" position while at tje same time refusing to give numbers. In dialogue with law-makers (and we can not avoid that dialogue) exactly such ambivalence will automatically lead the authorities to ever more (conservative) regulations that are ever more difficult and expensive to follow. I think when we want to maintain a space for reasoning we should try to give the law-makers numbers. Otherwise it is partly our own fault when they stick to the "no amount is safe" mantra.
ALARA
Acronym for "As Low As Reasonably Achievable." It means making every reasonable effort to maintain exposures to ionizing radiation as far below the dose limits as practical. Be consistent with the purpose for which the licensed activity is undertaken, taking into account the state of technology, the economics of improvements in relation to state of technology, the economics of improvements in relation to benefits to the public health and safety, and other societal and socioeconomic considerations. These means are in relation to utilization of nuclear energy and licensed materials in the public interest.
The question of risk from ionizing radiation is highly relevant yet it remains unresolved. There are a few issues that other posters have touched on. One is the fact that the linear no-threshold assumption is just that - an assumption. There is nothing wrong with using LNT within reasonable bounds - it is a perfectly serviceable model that generates testable predictions and is simple enough to be practical. In reality risk is not linear at low doses - the adaptive response can be expected to modify risk at low levels of exposure (most likely reducing it). It also means that it is scientifically invalid to sum low dose rate exposures over time and compare to a high dose rate exposure. An interesting question is whether the risk might actually be negative in the very low dose range (i.e. a little radiation reduces risk).
Ionizing radiations arise from both natural and manmade sources and can affect the various organs and tissues of the body. Late health effects depend on the physical characteristics of the radiation as well as biological factors. Well demonstrated late effects include the induction of cancer, genetically determined ill-health, developmental abnormalities, and some degenerative diseases (e.g., cataracts). Recent concern has centered on the risks of these effects following low-dose exposure, in part because of the presence of elevated levels of radon progeny at certain geographical sites and fallout from the nuclear reactor accidents at Three Mile Island in Pennsylvania in 1979 and Chernobyl in the USSR in 1986. In addition, there is concern about radioactivity in the environment around nuclear facilities and a need to set standards for cleanup and disposal of nuclear waste materials.
Since the completion of the 1980 BEIR III report, there have been significant developments in our knowledge of the extent of radiation exposures from natural sources and medical uses as well as new data on the late health effects of radiation in humans, primarily the induction of cancer and developmental abnormalities. Furthermore, advanced computational techniques and models for analysis have become available for radiation risk assessment. The largest part of the committee's report deals with radiation carcinogenesis in humans, primarily because: (1) there is extended followup in major epidemiological studies, particularly those of the Japanese A-bomb survivors and radiotherapy patients treated for benign and malignant conditions, and (2) the revision by a binational group of experts of the dosimetric system for A-bomb survivors in Hiroshima and Nagasaki allows improved analyses of the Japanese data. The report also addresses radiation-induced genetic injury and health effects associated with prenatal irradiation. While only limited application of the advances in our understanding of the molecular mechanisms of cancer induction and genetic disease is possible, these have been examined with the aim of narrowing the range of uncertainties and assumptions inherent in the risk estimation process.
Erik Strub
There is a problem with estimating a safe level in Sv. Sv implies low dose and dose rate, both undefined. Sv is for levels below deterministic, about 0.5 Gy.
Use of Sv assumes stochastic mutation that leads to cancer. The assumption that the mutation of a single cell leads to cancer is not supported, although widely accepted and taught. There is increasing resistance to the one-cell model. Other models are proposed, including that cancer is a tissue-level disease.
Assuming that cancer derives from stochastic mutation, there is no study that shows that mutation is linear with dose and dose rate. The only data extensive enough to measure mutation rate is the mega-mouse study. Mega-mouse does not support the LNT.
Cancer studies have not shown quantitative results below 0.5 Gy. Should this be a threshold for cancer induction it would suggest that cancer is a tissue level disease and deterministic. Is this a safe dose? There are no quantitative results below 0.5 Gy, only claims of statistical significance. The studies have not released their data, so there is no way of confirming claims and total error.
Safe is likely somewhere between 0.1.and 0.5 Gy.
@joseph, do you have some paper or another source for the „cancer as tissue reaction“.
Hanno
Several good ones are
Soto AM, Sonnenschein C, 2011, The tissue organization field theory of cancer: a testable replacement for the somatic mutation theory, Bioessays, vol. 33, pag. 332-340.
Soto and Sonnenschein have book tissue/cancer.
Baker SG, 2017, The questionable premises underlying the search for cancer driver mutations and cancer susceptibility
genes, Organisms. Journal of Biological Sciences, vol. 1, no. 1, pp. 3 - 9.
Brücher and Jamall BMC Cancer 2014, 14:331
Bjorn Brucher has several articles available on RG.
You're right, it can be confusing! The truth about radiation safety lies somewhere in between. Here's a breakdown:
No amount of radiation is entirely safe: Any exposure carries a very small risk of health effects, mainly an increased chance of cancer. This risk increases with the dose of radiation received.
However, some doses are considered very low-risk: We're naturally exposed to some radiation every day from sources like cosmic rays and the earth itself. This background level is quite low, and the risk of harm from it is negligible.
The key message is about managing risk: We aim to keep exposure to radiation as low as reasonably achievable (ALARA principle) while still enjoying the benefits of its uses in medicine, food preservation, and other areas.
Here are some helpful points to remember:
Dose matters: The risk of harm from radiation depends heavily on the amount you're exposed to. High doses, like those received during an X-ray scan or radiation therapy, can be risky, while low doses like from flying or background radiation pose minimal risk.
Time matters: Short bursts of exposure are less risky than ongoing exposure.
Type of radiation matters: Some types of radiation, like alpha particles, are more damaging than others like gamma rays.
Individual factors matter: Some people are more susceptible to the effects of radiation than others.
So, to answer your question directly: neither extreme statement is entirely accurate. While no radiation is inherently safe, low doses carry such a minimal risk that we don't consider them unsafe in a practical sense. However, higher doses can be significantly more risky, and minimizing unnecessary exposure is always advisable.
Not sure about some people being more susceptible. Is there evidence for this?
Also "short bursts" can be worse than chronic - it all depends on how large they are. If the "bursts" are of similar size to the total of chronic exposure in terms of Sv/year say, then this comment is right.
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