The Linear No Threshold concept assumes that the risk from radiation exposure varies linearly with total dose with no threshold
Recently, Edward Calabrese, an environmental toxicologist at the University of Amherst found out that Dr Hermann J. Muller, famous radiation geneticist knowingly lied in his Nobel Prize lecture when he claimed that there was “no escape from the conclusion that there is no threshold.” Calabrese described his discovery in September in Archives of Toxicology and Environmental and Molecular Mutagenesis
In 1927, Muller discovered that x-ray irradiation produces mutations in male fruit-fly germ cells. For this, he received the Nobel Prize in Physiology or Medicine in 1946. Many believe that Muller's assertion became a corner stone of radiation protection. This is the Linear No Threshold (LNT) concept which assumes that the risk from radiation exposure varies linearly with total dose with no threshold and any dose however small has an adverse effect.
Expert bodies accepted this model because of its simplicity in the management of radiation protection programmes.
“However, it has done much damage to speak of ‘no safe level of radiation' in scaring not only the public, but also those professionally involved in peacetime health physics who have not been involved in high levels and emergency situations,” Allen Brodsky, Adjunct Professor of Radiation Science, Georgetown University responded to an e-mail query.
In response to an e-mail query Calabrese disclosed that a reviewer of his article on the history of dose-response argued that he had not done a good job on the Muller section and key early radiation mutation studies. Calabrese found that a paper from the University of Rochester by Curt Stern and Casper on fruit-fly irradiation and germ cell mutation was published in 1948 but it was actually completed in August of 1946.
“This study was very important because it did not support a linear dose response and because it was the strongest study to date...using the lowest dose rate etc. I knew that Muller gave his Nobel Prize lecture on Dec. 12, 1946. So the question was whether Muller was aware of the new findings before his major speech,” Calabrese replied
By reviewing Stern's correspondence with Muller, Calabrese established that Muller knew of the findings which contradicted his theory a month prior to the Nobel Lecture.
Calabrese asserts that Muller's passionate beliefs influenced the way government and society viewed the risks of low doses of radiation. The 1956 recommendations of the US National Academy of Sciences (NAS) BEAR (Biological Effects of Atomic Radiation) I Committee reflected these views. Regulating ionizing radiation as if there was no safe dose began!
James Schwartz, a biographer of Muller, Kenneth Muller, Hermann Muller's grandson and Elof Axel Carlson, Muller's former student do not agree with Calabrese. Some feel that Calabrese, a supporter of radiation hormesis (beneficial effect) has conflict of interest. The balance of evidence shows that the edifice of radiation protection is not built on a lie.
Dr Evan B. Douple, Associate Chief of Research at the Radiation Effects Research Foundation, Hiroshima, does not think that the LNT hypothesis would have lost its applicability if Professor Muller would not have made the passionate statement in his speech.
“……. by the time the BEIR (Biological Effects of Ionizing Radiation) committees of the National Academy of Sciences began updating the risk estimates, the mutation risk was superseded by the risk of cancer. Having been intimately involved with the BEIR VI and BEIR VII studies, I can assure you that the voluminous data reviewed by the committee members that related to supporting or refuting LNT, was not swayed or overly influenced by the shape of a dose-response curve in the mutation work of Muller,” Douple responded. (Dr Douple was Director, Board on Radiation Effects Research, National Research Council)
He is not even sure that Calabrese's interpretation and assessment that Muller was deceptive in his presentation is necessarily accurate or fair.
“Although somatic mutations became a dogma for radiation carcinogenesis, the LNT for carcinogenesis was based on (a) analyses of cancer induction in rodent models, (b) biophysical characteristics of energy deposition, ionizations, and DNA damage in cells, and (c) the early epidemiological studies of cancer in the Japan A-bomb survivors,” he clarified in an e-mail.
He does not think that the conjecture and personal interpretation of an untestable accusation will have significant impact among the radiation protection community.
Prof Ludwig E. Feinendegen, Heinrich-Heine University, Germany thought that “the new revelations on low-dose effects in the realm of biological responses are making an impact on the radiation protection community — as it appears currently from the defensive manner of their arguments for keeping the LNT model, at least for the time being. Calabrese has done us a great favour by his new paper on Mueller's mistake.”
That there is no safe level of radiation continues to be a useful assumption in radiation protection. It is yet to be proved as a scientific fact.
Douple believes that the exhaustive efforts of those who claim that demonstrating hormesis (beneficial effect) or the presence of thresholds will revolutionize the radiation protection field are misguided.
“We need to educate the public regarding the importance of ‘acceptable levels of risk'—levels that are believed to include risks, but risks for adverse effects that are so small that one would not be able to observe and measure an excess of the effects with a realistic study. Only then will the fear and paranoia associated with radiation effects gradually become less and less and sources for energy production can be fairly and objectively be evaluated,” Douple proposed as a realistic way forward.
Regulators want dose limits for enforcing radiation protection. What is the threshold dose value they will accept for enforcement? Calabrese and his followers have not yet responded to my query.
The French Academy of Sciences, the only scholarly body which has views closer to those of Calabrese on hormesis conceded that on the basis of present knowledge, it is not possible to define the threshold level (between 5 and 50 mSv) or to provide the evidence for it. The dose limit for workers recommended by the International Commission on Radiological Protection (ICRP) is 20 mSv per year averaged over five years with no year exceeding 50 mSv. The dose levels to radiation workers achievable are so low that the risk from them is negligible. Negligible risk is no risk at all. That we cannot rule out beneficial effects of radiation is also a comforting thought.
K.S. Parthasarathy
Raja Ramanna Fellow, Department of Atomic Energy (ksparth@yahoo.co.uk)
Keywords: radiation exposure
Comments:
This is all propaganda by the Nuclear Industry to get a go ahead signal for planting deadly and dangerous radiation emitting nuclear power plants all over our dear country which politicians have bled in their greed through siphoning off black money which has to be laundered and brought back as nuclear power plants. I'd like to advise the readers of the Hindu that this is just an advertisement such as other ads which falsely claim that aspirin is good for you, chocolate is good for you and black tea imbibed thrice a day reduces blood pressure! Tall claims to promote products. What future do we leave our kids with huge decommissioning costs, nuclear wastes?In the event of an accident from Human Error (it has been proved that despite safety measures all major nuclear accidents have occurred from Human Error)we will leave large Isolation Zones in a country where so many people have no land and no roof over their heads This country can leave them a bright / sunny future with Renewables only
This must be very comforting news to the thousands of Japanese now forced to be evacuated. And raises the question - are all the world's most reputable scientific bodies, and governments just fools - taken n by tree-huggers' nonsense? But more likely - it raises the question of who is behind this quack science of "radiation hormesis". The answer is not hard to find. Just about all of the research on this benign low level radiation is funded by USA's Department of Energy.The one and only Academy of Science that slightly supports this quack theory is the French. Imagine the pressure they'd be under, with France caught up in its boondoggle of aging nuclear reactors - now unable to fund the security measures required by the EU, following the Fukushima nuclear catastrophe.
It may not be linear, but could be a sigmoid curve, like the growth curve of a bacterial culture or the behaviour of many "allosteric" enzymes. Yet, that does not necessarily mean there is a threshold, below which radiation is harmless or even beneficial -- the so-called "hormesis". It possible that "hormesis" manifests itself when very low levels of radiation destroy some inhibitory or detrimental factor.
The fellow may study critically 2003 Recommendations of the ECRR: The Health Effects of Ionising Radiation Exposure at Low Doses for Radiation Protection Purposes:Regulators' Edition. Edited by Chris Busby with Rosalie Bertell,Inge Schmitze-Feuerhake,Molly Scott Cato and Alexei Yablokov. Published on behalf of the European Committee on Radiation Risk,Green Audit 2003. Thereafter he may give his opinion. Till then his article will be regarded by geniune scientists like Mueller and believers in truth like Mahatma Gandhi as nothing short of witchcraft. The International Commission on Radiological Protection radiation risk model based on external radiation effects is not scientifically applicable to internal radiation effects. The scientific model applicable to internal irradiation is described in the above reference.
The left lobby is out with a vengence to stifle any debate about scientific facts related to nuclear energy. Arguments like "nuclear power plants are ploy to launder politician's black maoney" are all they can offer in opposition to an excellent article by a nuclear scientist.Time for the nuclear scientist community to come out in a big way to educate the "real" public about the reality.
There is unnecessary fear psychosis created amongst the public by vested interests. Their action is coming in the way of establishing new projects in the world. Consider this: Does anyone reject the doctor's suggestion of getting a whole body CT scan done for investigating a particular disease? They do not even know the quantum of radiation (large one) that the patient gets. Yet, there is not even a whimper, rightly so, because it is likely to benefit the patient. That being the case, if any installation involving radiation is to be set up, innumerable safety aspects are considered before the project sees the light. Delay becomes inevitable due to various factors including protests by the so called civil rights organisations, who in several instances seem to make mountain out of molehill.The author on the target when he says, "The dose levels to radiation workers achievable are so low that the risk from them is negligible". Being a radiation worker, I have experienced this.
The photograph published along with the article seems to be that of an MRI machine. It is irrelevant to the topic of the article, and could be quite misleading to the lay public.
Ram K and Anand are doing a grievious disservice to all life when they lie about nuclear energy. Anand must know that CT scan is voluntary and damage done by radiation from nukes is involuntary. As far as benefit goes they are ignorant of the fact that nuclear energy programmes consume all the electricity they produce leaving none for society. All that nukes give is to pose the greatest danger to all life for millions of years by radionuclides criminally lodged inside the living beings without their consent, let alone of future generations. These citizens must learn from the reference I have cited and stop supporting perfect mass murders forthwith. Nuclear supporters have one job given by the people which is to slave for thousands of years to keep the nuclear poisons from the biosphere. And let them work on this.
I would like to clarify on what R Kumar has written on 27 Jan: There seems to be a terrible misunderstanding about the usage of nuclear energy. While I fully support the usage of Nuclear Energy for peaceful purposes, I will never support WsMD. If the nuclear energy programs were to consume all the energy they produce, how are we getting electricity from the reactors?
There are terms known as Biological Half Life and Effective Half Life of a given radionuclide within the human body. Barring those who reside in certain tissues for a longer duration, all others are excreted. True, they remain within the earth but they were there earlier also!
He says CT is voluntary. How many patients are told before a CT is done about the dose & biological effects of radiation that he is going to receive? I rue the woefully inadequate knowledge of most of the radiologists about the effects of radiation. Fortunately, I am not one of them, having been in Nuclear Medicine as well as Radiology!
The question Anand puts is understandable because such questions are put even by nuke specialists or vested interest scientists! When one is ignorant of the energy balance sheet, one leads directly to perfect mass murders on the scale of extinction! The deaths from nuclear fuel cycles even during normal operations are discussed in detail by a former Chair of the USNRC Dr John Gofman. I have discuseed these in Health Effects of Nuclear Power. A perfect mass murder occurs when deaths cannot be pinpointed to a certain cause like :"The nuclear rectors caused this death"! That is why with impunity did the governments conduct atmospheric nuclear tests and analogously the nuclear fuel cycles of the world during normal operations are also being operated(criminal). See Andrei Sakharov's Memoirs dealt with in my study of India Population. And nuclear fission produces radionuclides new to nature of vintage prior to the nuke era. Click on Ramaswami Ashok Kumar on Google Search and get the story!