Radiation Exposure Standards By AHANE
Radiation Exposure Standards By AHANE*
(*As High As Naturally Existing)
This page was originally posted as a Fukushima Commentary on January 2,2014
The limits for public exposure to radiation vary from country to country. The standards are usually predicated on the concept of ALARA – As Low As Reasonably Achievable. The rationale behind ALARA is two-fold. First, we have the long-held assumption known as the Linear/No Threshold risk model (LNT) which was formulated after WWII by extrapolating down from the actual data. Its evolution began with Herman Muller who used laboratory fruit flies exposed to varying degrees, to see what the responses were. The lowest exposures were 2,750 millisieverts, and he increased the doses up to in excess of 10,000 mSv. He found that there were few fatalities at the low end of the exposure spectrum, and total mortality at the high end. When depicted on a logarithmic graph, the data suggested a linear relationship between exposure and mortality. He extrapolated down to zero exposure without any mortality data below 2,750 mSv. Muller's extrapolation suggested there was no threshold of absolute safety. Muller received the Nobel Prize for the assumption in 1946, and LNT became widely accepted.
But, the assumption from fruit fly data needed to be verified, and the sudden end to WWII in the Pacific produced just what was needed. Specifically, the statistics on fallout fatalities due to cancer within the some 90,000 survivors of the Hiroshima/Nagasaki bombings in August, 1945. Although the exposure versus fatality data virtually vanished below exposures of 500 mSv, when the data points were placed on a logarithmic graph a best-fit line could be superimposed from about 10,000 mSv sievert exposure (with 99% fatality) down to about 500 mSv, below which the bomb-survivor data was indistinguishable from the cancer death rate with unexposed populations. However, the best-fit line pointed directly to the zero-dose/zero-fatality conjunction at the lower left-hand corner of the graph, similar to Muller’s extrapolation. For all intents and purposes, a ruler connected the dots, extending the actual best-fit line down to the lower left-hand corner of the graph.
This is where the second part of the LNT assumption comes in. The model suggests that even the most miniscule exposure to radiation has a miniscule risk of causing fatal cancer. It is from this risk assumption that the no-safe-level concept evolved. LNT-itself gives no credit to naturally-occurring cellular and DNA repair mechanisms. However, these mechanisms exist in all of us, and standard-setting bodies around the world know it. Thus, in the very-low-exposure region (generally stated as being below 100 millisieverts), LNT necessarily over-estimates risk to a very great degree. However, these standard-setting groups rationalize that it is better to over-estimate risk than under-estimate, thus LNT is widely used to establish limits for public exposure. The concept of ALARA came into the picture following the accident at Three Mile Island in 1979. Exposure limits have been subsequently set based on what is considered “reasonable” and “achievable”. In other words, the many of the world’s limits are determined subjectively. Since standard-setting bodies are necessarily governmental, political expediency has also had its impact.
Unfortunately, ALARA has created controversy because of studies on the wide variety of natural background exposure levels around the world. Most public exposure limits are set more than 10 times below exposures experienced continually by hundreds of thousands of people on on our planet. Populations living in these regions have life expectancies, cancer incidence, and cancer death rates roughly the same as their fellow countrymen exposed to much lower radiation fields. In fact, the statistics show a small increase in life expectancy and somewhat lower rates of cancer incidence and cancer deaths in every group. In the face of this evidence, standard-setting bodies have ruthlessly clung to LNT. Thus, the controversy.
In addition, the fact that ALARA-based standards greatly over-state actual risk makes little difference in the mind of the general public. The public, in general, wants to know what the actual risk of low level exposure is. If there is actually no completely safe level of radiation exposure, then no-one is really safe regardless of radiation dose. ALARA and LNT frighten people. They cause unnecessary psychological distress. ALARA and LNT are the foundation of the psychological condition known as radiophobia – mortal fear of radiation. The situation has gotten out of control in Japan because of the Fukushima accident. Japan has set its exposure limit at one mSv per year, twenty times below post-accident standard recommended by the International Atomic Energy Agency. Because the Tokyo government in 2011 believed it “reasonable” and “achievable”, the 1 mSv annual limit was invoked to quell the tsunami of political criticisms concerning use of the 20 mSv limit for decontamination and evacuee repopulation.
For decades there has been a call for a more-appropriate, evidence-based methodology for setting exposure standards. Eminent radiation experts such as Drs. Jerry Cuttler, Edward Calabrese, T.D. Luckey, and Thormond Henriksen have been trying to get LNT expunged from the standard-setting arena, without success. Their published research on the matter is voluminous. Their credentials are impeccable. However, their public notoriety and political impact have been minimal. Thus their important work is largely unknown.
Recently, however, a relatively well-known person has entered the fray and called for LNT to be eliminated: Stewart Brand, founder of the Whole Earth Catalog and former opponent to nuclear energy. In his 2009 book, Whole Earth Discipline: An Ecopragmatist Manifesto, Brand said nuclear energy is a green technology, which caught the antinuclear community off-guard. Greenpeace spokesperson Jim Riccio calling Brand’s shift “nonsensical”. Now, Brand has joined the “get rid of LNT” voices. (1) Brand says LNT is an idea ready for retirement. Brand states, “At stake is the hundreds of billions spent on meaningless levels of "safety" around nuclear power plants and waste storage, the projected costs of next-generation nuclear plant designs to reduce greenhouse gases worldwide, and the extremely harmful episodes of public panic that accompany rare radiation-release events like Fukushima and Chernobyl.” He adds that below 100 mSv per year of exposure there have been no cancers detected “either because it doesn't exist or because the numbers are so low that any signal gets lost in the epidemiological noise.” Brand concludes, “Once the LNT is explicitly discarded, we can move on to regulations that reflect only discernible, measurable medical effects.”
Another call for the end of LNT comes from the Health Physics Society, perhaps the most informed organization in the world concerning the biological effects of radiation exposure. (Aside - I worked as an HP for 21 years, in the US Navy and civilian nuclear industry. - end aside) The Society says in its position statement entitled Radiation Risk in Perspective, “There is, however, substantial scientific evidence that this model [LNT] 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 notaccounted for by the linear, no-threshold model.”
If the use of ALARA and LNT is inappropriate and can no longer be rationally tolerated, what conception should we use instead? Blogging colleague Rod Adams of Atomic Insights.com says we should consider replacing ALARA with another acronym – AHARS (As High As Relatively Safe). (2) Adams correctly doesn’t take credit for the concept since it was first proposed by Oxford Physics Professor, and leading advocate for rational radiation standards, Wade Allison. (3) While it might seem over-the-top to many people, Adams calls for a limit of 100 mSv per month! This would be for what we call “chronic” (somatic) exposures which take place over relatively long periods and account for the effect of our natural biological repair mechanisms. The limits based on LNT/ALARA are predicated on huge exposures over a very short period of time, measured in hours and cannot give natural cellular and DNA repair mechanisms time to fix the induced damage. Adams points out that “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?” He also postulates that embracing AHARS would provide “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.”
While I do not disagree with Rod Adams and Wade Allison in actua, I must differ with them in esse. When we accept that political expediency is unavoidable with any official standard’s revision, their postulations must be put aside and a less-alraming alternative should be proposed. One possibility might be that suggested by Robert Hargraves in his recently published Radiation: The Facts. Hargraves says there is virtual unanimity in the safety of an annual limit of 100 mSv per year. He has a valid point. Even the largely-antinuclear Japanese Press routinely reports a scientific consensus on 100 mSv/yr being a threshold for cancer induction. While Hargraves’ notion is orders of magnitude easier to facilitate than Adam’s AHARS proposal, it remains a major leap above existing standards across the world, and a factor of 100 jump above Japan’s standard. Besides, it is based on a scientific consensus steeped in LNT-based relative risk rationality. The public is not looking for relative safety with radiation exposure. They want absolute safety.
None of the above proposals embrace the most powerful and unmistakable evidence on our planet: Mother Nature! I propose that radiation exposure standards be based on AHANE – As High As Naturally Existent. That is, the highest naturally occurring radiation exposures in the world experienced by a large number of people without discernable negative health effects. The highest population background on our plant is Ramsar, Iran, with an annual background level of 250 mSv per year. Although nearly 32,000 people live in the area, only about 2,000 receive the 250 mSv/year dose. It should be noted that some Ramsar residents experience as much as 900 mSv/year without adverse effects. (5) While this evidence suggests a 250 mSv/year standard should be embraced around the world, a statistical cohort of ~2,000 individuals might be politically dismissed as a statistical aberration.
However, there are three other relatively high natural background regions with large-enough populations to demonstrate absolute safety. They are Guarapari, Brazil (pop. 73,000), Kerala, India (pop. 100,000), and Yangjiang, China (pop. 80,000). The average exposure in Guarapari is about 50 mSv/year, with Kerala not far behind at 38 mSv/year and Yangjiang at 35 mSv/year. In all cases, the residents have life expectancies at least as long as their national peers, and cancer rates slightly lower than fellow countrymen. (6)
I would like to add that 50 mSv/year was the upper limit for nuclear worker exposure before ALARA came into political vogue. It was the limit during my nuclear Naval experience from 1968-1974. Numerous studies on nuclear shipyard workers during the period when a 50 mSv/yr limit was in vogue revealed no discernable negative health effects. Thus, we not only have natural background studies to show the absolute safety of my 50 mSv/year AHANE proposal, but US Navy shipyard worker studies as well.
Thus, I propose the utter rejection of LNT and ALARA, the world-wide embrace of AHANE, and an international guideline for public exposure of 50 mSv per annum. The supporting evidence comes from Mother Nature. I would further set emergency exposure limits at 100 mSv/year, in line with Hargrave.
There’s no doubt a world-wide shift away from LNT/ALARA to AHANE would produce considerable antinuclear bombast, negative Press coverage, and political debate ad nauseum. However, with a concerted international educational effort, patience, and persistence, I firmly believe AHANE could be accepted by the world’s public at-large in the not-too-distant future. Subsequently, if I might paraphrase Stewart Brand, crucial decisions about nuclear energy would no longer be determined by assumptions of imaginary cancers per millisievert.
1 - Brand, Stewart; The Linear No-Threshold (LNT) Dose Hypothesis; from “What scientific idea is ready for retirement?” http://www.edge.org/responses/what-scientific-idea-is-ready-for-retirement
2 - Adams, Rod; As High As Relatively Safe (AHARS) – Sensible radiation standards; Atomic Insights.com http://atomicinsights.com/high-reasonably-safe-ahars-sensible-radiation-standards/#more-13836
3 - Allison, Wade; Man’s Fear of Nuclear technology is Mistaken: Better and Safer Than Fire; http://www.radiationandreason.com/uploads//enc_BetterThanFire.pdf
4 - Hargraves, Robert; Radiation the Facts; 2014. https://sites.google.com/site/radiationsafetylimits/
5 – Karam, Andrew P.; The High Background Radiation Area in Ramsar, Iran…; February, 2002. http://www.wmsym.org/archives/2002/Proceedings/10/434.pdf
6 – Mortazavi, S.M. Javad; High Background Radiation Areas of Ramsar, India; Kyoto University Biology Division. http://www.angelfire.com/mo/radioadaptive/ramsar.html