Ionizing radiation is a known, studied and understood phenomenon to which the Precautionary Principle no longer applies. It is time to shift the paradigm that governs radiation exposure limits to a sensible standard of “As High As Relatively Safe” (AHARS).
Aside: I’m crediting Dr. Wade Allison with the etymology of the term – AHARS. I will also credit him as my initial source for the specific numerical recommendation – 100 mSv/month – to be applied in the case of chronic doses. Please read his document titled Man’s Fear of Nuclear Technology is Mistaken: Better and Safer than Fire for an explanation of why that is a conservative recommendation with historic and scientific basis. End Aside.
Conventional wisdom about atomic radiation is that all doses carry some risk and that the risks from each exposure can be added to each other in a cumulative fashion, both for individuals and for large exposed populations. That conventional wisdom logically leads to a presumption about radiation exposure and a standard that has no numerical limits and can only be qualitatively described as “As Low As Reasonably Achievable” (ALARA).
In our ALARA-based radiation exposure paradigm, the word “reasonable” is undefined. That leaves politicians, activists, lawyers, and regulators free to choose to define it to serve their own purposes. Often, those purposes include making it as difficult and expensive as possible to comply with regulations. Many powerful interests are served by burdening nuclear energy and nuclear medicine. Competitors benefit from slowing market penetration of measurably superior products by adding cost, fear and uncertainty.
The conventional wisdom based on the Linear No Threshold (LNT) assumption is wrong, as proven by many decades worth of research and study on the health effects of low level radiation. Here is an excerpt from the Health Physics Society position statement titled Radiation Risk in Perspective that provides some sense of the basis for stating that the LNT assumption is wrong; it does not resemble reality.
In part because of the insurmountable intrinsic and methodological difficulties in determining if the health effects that are demonstrated at high radiation doses are also present at low doses, current radiation protection standards and practices are based on the premise that any radiation dose, no matter how small, may result in detrimental health effects, such as cancer and hereditary genetic damage. Further, it is assumed that these effects are produced in direct proportion to the dose received, that is, doubling the radiation dose results in a doubling of the effect. These two assumptions lead to a dose-response relationship, often referred to as the linear, no-threshold model, for estimating health effects at radiation dose levels of interest. There is, however, substantial scientific evidence that this model is an oversimplification. It can be rejected for a number of specific cancers, such as bone cancer and chronic lymphocytic leukemia, and heritable genetic damage has not been observed in human studies. However, the effect of biological mechanisms such as DNA repair, bystander effect, and adaptive response on the induction of cancers and genetic mutations are not well understood and are not accounted for by the linear, no-threshold model.
Using an incorrect dose response assumption as the basis for regulations and clean up standards is not only costly, it is harmful to human health and safety.
Aside: I’ve been making the case for radiation standards based on AHARS in several different comment threads over the past few days, but those discussions have taken place in an almost hidden location in threads posted in response to posts that are not obviously about low level radiation or radiation standards. I’ll be borrowing from those threads here to try to bring the important discussion points together in a more understandable progression. End Aside.
This quote from another commenter embodies the basis for many people’s resistance to accepting a paradigm shift for radiation regulations from ALARA to AHARS.
We have a scientific, policy, and regulatory consensus about health risks and radiation doses. I’m not sure why this isn’t enough (and why the industry can’t work within these regulatory and scientifically supported exposure limits)? Why highly speculative dose rates (or cumulative collective doses), and scientifically unsupported positions should be the response of advocates (with a defense that there is plenty out there that is much worse). Well, the public doesn’t see things this way, and those who have these projects (or accident sites) in their back yards don’t see it this way either. We always need to be doing better, and lowering standards to increase risk is unlikely to win very many new supporters.
Though the thread takes a few detours and there are some intervening comments, the following response was designed to concisely respond to the challenge to AHARS and to the accusations that is is “high speculative” and “scientifically unsupported.”
You continue to misunderstand my position regarding a recommendation to shift clean up standards from our conventional “As Low As Reasonably Achievable” (ALARA) to a more comprehensively risk-aware standard that Wade Allison describes as “As High As Relatively Safe”.
Studies have not been able to prove conclusively exactly what the risk model numbers should be for chronic doses that are accumulated slowly enough so that biological mechanisms have time to work their evolutionary magic. For performance standards associated with building, operating, maintaining or decommissioning of nuclear facilities, there are some side benefits to setting standards that are tight enough to keep people focused on improvements in design and work products.
Studies have suggested that there might be a risk above certain accumulated lifetime doses and the authors of those studies have often made statements to the effect that the risk is “not inconsistent” with the LNT. Further analysis of the data used often reveals that the statistical fit at low exposure is a stretch, to put it mildly. The more honest answer is that the effect is only visible if you look really, really hard and you are highly motivated to discern “signal” amongst a lot of “noise”. Even the linear model acknowledges that small doses impose small risks. BEIR acknowledges that dose rate matters.
Allison uses the radiation dose understanding that has been developed from the use of dose fractionation in cancer treatments. As he explains more completely than I will here, cancer treatments often use doses that are several times as high as a fatal dose if given all at once. However, by spreading the treatments over days or weeks, doctors give their human patients time to recover and the healthy cells time to exhibit their normal response to stress, which is to become stronger and more resilient.
Allison’s accessible summary of his academic work explains how his 100 mSv/month recommendation is a conservative number that is 1/200th of the dose rate that healthy tissue survives during cancer treatments. His recommendation is essentially the same limit as was established as the tolerance dose in 1934, after several decades worth of study and experience with using radiation in medicine and industry. That tolerance dose was based on sound science and understanding developed before the atomic bomb-inspired propaganda campaign to induce fear of all things radioactive. The factor that Allison does not mention, but which is at least as important as a propaganda campaign motivator, is that excessive fear of radiation provides a service worth hundreds of billions of dollars per year to the competitive interests of the combustion (hydrocarbon) industry.
The overly restrictive radiation standards for evacuation and relocation are the only basis for the continued claim that Fukushima was a disaster. Because of the way that society has reacted, the event was a very real disaster for a large number of people. However, if we had sensible radiation standards in place, the event would have been about as consequential as the recent explosions and conflagrations that have affected the oil-by-rail industry. The disaster label would simply not apply if radiation tolerance standards of 1934 were applied rather than the ever tighter standards developed in the 66 years since Muller gave his fateful Nobel Prize speech asserting a linear model, thus initiating the ALARA age.
Here is the way I concluded my comment response justifying my support for a radiation exposure standard paradigm shift from ALARA to AHARS.
When establishing standards for evacuation or abandonment of widespread areas that have intrinsic value (after some kind of event has already occurred), standards should balance the assumed risk of radiation doses against the known risks of stress, displacement, victimization, depression, poverty, alcoholism, malnutrition, etc.
That is when “as high as relatively safe” standards make sense. If society does not ban smoking, diesel engines, fatty foods, alcohol, dropping out of school, driving cars, walking on busy streets, or working on roofs to install solar panels, why should it establish standards for radiation exposure that are orders of magnitude less risky than those activities – even if you use the math of the questionable LNT assumption?
The health effects of low level radiation have been studied long enough. Even though we are not precisely sure what they are and even if we realize they are not the same for all populations (some people are apparently more vulnerable than others), we are pretty sure that the risk is low and the effect, if any, is something that happens many decades into the future.
At a certain age, people are essentially immune to low level radiation-induced cancer that takes decades to develop. That is one of the reasons why I have stated that I would resort to civil disobedience if anyone told me I had to abandon my home in the event of radioactive material releases that might expose me to something less than 100 mSv/month. The possibility of that dose having any negative effect on me or my wife is incredibly small and not worth worrying about. It is certainly not worth losing my home.
Please note that this recommendation would not primarily benefit the nuclear energy industry. It is aimed at providing a utilitarian benefit to society as a whole because it reduces the “terror” value of a radiation dispersal device as well as enabling a more sensible use of many other beneficial medical capabilities of radiation. It would lower nuclear medicine costs, possibly by more than it would lower the liability costs associated with operating nuclear power plants.
The Guardian (Jan 11, 2014) What scientific idea is ready for retirement?. Scroll down or search for Stewart Brand The Linear, No Threshold Radiation Dose Hypothesis
Note: I came across Brand’s suggestion to eliminate the LNT by chance within hours after I published the above post.