Friday, May 20, 2011
LOW LEVEL RADIATION - IS IT DANGEROUS? A debate over the Linera No Threshold and Hormesis theories.
Recently I mentioned how "one of those eco-fascist blogs that pretend to scientific standards" ,Respectful Insolence, a site hosted by Scienceblogs, had launched a vitriolic attack on Ann Coulter for mentioning the hormesis effect in radiation and asked the host to produce some evidence that she was wrong and the official LNT theory correct. Obviously he didn't and became the target of numerous ad hominem along the lines that i must be a "crank" to disagree with LNT and therefore no debate was required. With 1 exception # 91
However in due course 1 LNT supporter with "30 years experience" in the field did engage in a serious discussion and I think that worth extracting and preserving since I know of no other public debate on the subject. There was some movement. You will have to judge the result for yourselves.
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106 Here's a whole book full of evidence that the LNT hypothesis is flawed, in the opposite direction to that claimed by Neil Craig. If anyone can point me to a refutation of Gofman I would be grateful. I find his arguments very convincing. Neil Craig simply dismisses any evidence he doesn't like as propaganda from the anti-nuclear lobby.
Posted by: Krebiozen
April 30, 2011 5:18 PM
109 Kebriozin you clearly don't know that Gohman, your further than LNT scare teller, is actually the man who invented the LNT theory, without the inconvenience of first looking for evidence.
He also predicted, on the basis of it, half a million deaths and half a million non-fatal cancers as a result of Chernobyl. The total death toll is actually 56 which is strong evidence his theory is wrong.
110 Neil, I do know that it was Gofman who proposed the LNT. I don't see why that means he was wrong. He based it on experimental evidence and on epidemiological evidence. The National Academy of Sciences agreed with him.
Here's an article published by the National Academy of Sciences about the LNT that explains why I think Coulter's and your arguments are nonsense. It concludes:
In summary, given our current state of knowledge, the most reasonable assumption is that the cancer risks from low doses of x- or γ-rays decrease linearly with decreasing dose. In light of the evidence for downwardly curving dose responses, this linear assumption is not necessarily the most conservative approach, as sometimes has been suggested, and it is likely that it will result in an underestimate of some radiation risks and an overestimate of others. Given that it is supported by experimentally grounded, quantifiable, biophysical arguments, a linear extrapolation of cancer risks from intermediate to very low doses currently appears to be the most appropriate methodology.
Please note the reference to, "experimentally grounded, quantifiable, biophysical arguments".
As for your claim that only 56 people died as a result of Chernobyl, even the IAEA estimates that "several thousand" people are likely to die. Other estimates are considerably higher. Given changes in the former USSR, and the background noise of deaths due to other causes, it is difficult to know which estimates are more accurate. --------Posted by: Krebiozen
111 Neither they, you, nor Gohman have produced this alleged experimental evidence, which is not how one does science. Extrapolating from high dosages is ridiculous and would lead you to say that because there is a 100% chance of dying if a falling elephant lands on your head there is a 0.1% chance of death every time you put a hat on. Science doesn't work on such assumptions either.
The 4,000 predicted (not actually happening) is predicted from the LNT theory (as indeed was Gohmans 1 million which obviously didn't happen). Justifying a prediction by saying the predictor predicted it and predicts that he is right is silly for reasons which will be obvious to anybody capable of logical thought. The failure of the 1 million prediction to be realised in real life, or even a tiny measurable fraction thereof, is, on the other hand, proof positive that LNT is wrong. ---------Neil
112 - Neil, have you actually read any of the material I have linked to? The National Academy of Sciences paper has 64 references, most of them to primary research papers. Gofman has copious references to primary research that supports his arguments. Just because you refuse to acknowledge or respond to this evidence doesn't mean it doesn't exist. The Hiroshima and Nagasaki data cited in the NAS paper seems very convincing to me.
Your elephant analogy demonstrates how little you understand this subject. The minimum possible dose of radiation is a single electron track, which can potentially hit and damage DNA, thus causing cancer. This has been demonstrated in laboratory experiments. The more electron tracks, the higher the chances that one of them will damage DNA. As DNA repair mechanisms are not 100% effective even a single electron track can induce cancer.
A better analogy might be someone firing a shotgun at you with a varying number of pellets in the cartridge. A single piece of shot is unlikely to hit and kill you, but it is possible it might. The more shot in the cartridge, the higher the chances of death.
Just because it is difficult or impossible to demonstrate with statistical significance how many people have died or will die as a result of Chernobyl does not mean that no one has died. Even a million excess deaths over 25 years in the whole of Europe would be very difficult to measure against background mortality from other causes. To suggest that it is certain there have not been 4000 excess deaths is ridiculous.
Scientists from the former USSR have published several papers suggesting that the death toll from Chernobyl is much higher than WHO and IAEA estimates. See 'Chernobyl: 20 Years On - Health Effects of the Chernobyl Accident' published by the European Committee on Radiation Risk and A. Yablokov's 'Chernobyl: Consequences of the Catastrophe for People and the Environment' published by the New York Academy of Sciences.
Incidentally, the European Committee on Radiation Risk has just released a report using two different methods that estimates between 489,500 and 2.45 million excess cancers caused by Chernobyl over 50 years.
http://euradcom.org/2011/chernhealthrept3.pdf
I don't pretend to know for sure which of the many estimates is correct, but until we do know, it is sensible to apply the precautionary principle. I think you are suffering from premature certainty. -------Krebiozin
113 At the very least you are acknowledging that you are not relying on scientific evidence but on the "precautionary principle".
In which case Ann Coulter has at least as much right to rely on the science.
And Orac & supporters owes her a public apology for accusing her of opposing "physics". An apology which would obviously have been given days ago by Orac & supporters had any of them not been corrupt eco-fascists merely pretending to have a respect for the rules of science. QED.
If you don't like my elephant example here is another. The LNT theory says that risk is wholly proportional to exposure. Therefore the risk is proportional to both the amount of "shots" (ie radiation) and the number of targets (cells). Thus multicellular animals like elephants are, if the theory is not crap, a billion times more susceptible than small ones and elephants drop like flies, from cancer whereas flies don't.
Obviously this is not how the real world works hence the theory is crap QED. As I have pointed out there is a vast amount of other evidence and it is clear that, had science been involved rather than politics, LNT would have been dumped generations ago.--- Neil
115 @Scottynuke
I'm aware that the NYAS only published Yablokov's book and doesn't stand behind his findings. I wasn't meaning to suggest the NYAS endorse his work (it is available free through a link on the llrc.org website BTW). I still wonder a bit when Gofman's estimates seem to supported by the findings of Soviet scientists. I'm a bit uneasy about dismissing all their work too easily. I wonder if the dangers of low dose radiation might be greater than the LNT suggests.
In essence the radiation dose response curve disappears at the low end into a mush of noise and confounding factors sufficient to hide a very large number of deaths. We don't know if the curve is linear or if it curves up or down for any or all types of exposure to any or all types of isotopes. Any population big enough to calculate a statistically significant increase in deaths suffers from a lack of a suitable control group.
The increases in mortality from various causes documented in the former USSR may or may not be due to Chernobyl. Several of the studies I looked at found a greater increase in mortality where dose was greater. I don't know what other evidence we might hope to find.
Neil - what you seem to be referring to about cancer in different sized animals is known as Peto's paradox.
It's an interesting point, but I don't think it's a good argument against the LNT. We have no idea how many cancerous cells arise in elephants but fail to develop into observable tumors, as compared to those in smaller animals. Less external radiation would get through an elephant's thick skin to damage vulnerable dividing cells than in a mouse, for example. External and internal radiation have different effects. It's not as simple as you suggest.
I'm intrigued by the "vast amount of evidence" you mention that the LNT is wrong. All the evidence I have seen for radiation hormesis in humans has been effectively debunked, in the same way that Orac has demonstrated that Coulter's claims are nonsense, above. Can you point out where he is incorrect in his analysis? Or where this article is wrong
It seems to me it is the pro-nuclear lobby that has the money and power to manipulate public opinion and policy in this area, not the "eco-fascists", whoever they are.----Krebiozen
116 Krebiozen if you haven't seen the "vast amount of evidence" you haven't looked at the link I put in my first post. http://a-place-to-stand.blogspot.com/2010/03/low-level-radiation-evidence-that-it-is.html ...
Your defence to the elephant example is to say that there is a mechanism whereby the body can fight radiation in the same way that there is a mechanism whereby the body can fight low doses of poison or infection. This is the medical explanation for the hormetic effect in everything else, or as traditionally stated "the dose makes the poison". Thus your "defence" of LNT is to acknowledge it is likely to be entirely wrong.
In any case your claim that "Orac has demonstrated that Coulter's claims are nonsense" is clearly totally untrue. The very worst that anybody could honestly say is that Coulter's position can be described, if you ignore the proof, as having no more proof than the LNT theory, which has no positive proof (ignoring the vast amount to the contrary). The more honest alarmists here have acknowleged that there is no actual proof for LNT but defended it on the "Precautionary Principle", which is not the same as scientific evidence. Orac, of course, never reaches or even aspires to the heights of "more honest".
If the balance of lobbying power were, as you state, then with the Fukishima earthquake/tsunami having caused 25,000 deaths and the reactor damage zero the balance of media coverage would be 25,000 hours of TV time on the real tragedy and zero, or less, on the reactors. --- Neil
117 Neil, I have looked at most of the links and studies you refer to on your (horribly laid out) blog many times. This has been a subject I have studied over the past 30 years since I first worked with radioactive materials. I first came across your blog a couple of years ago, but I have learned nothing new from it. ---Kreboizen
(some stuff omitted here - there was a dispute about what was on my blog and some loss of tempers-Kreboizen repeats the relevant stuff later)
128 Kreboizen I have no intention of giving up ....I have actively been looking for somebody willing to debate the LNT/hormesis cases without dropping the subject and changing to ad homs and, unless you object, expect to put up a summary of any sensible discussion on my own blog. On those grounds I would like to acknowledge that you have not been involved in ad homs - that was going on long before you got here.
On the particular points you raise I think you are wrong to say that Professor Cohen's work and that of Professor Chen (Taiwan) are "known to be wrong". They have both been disputed. It would be astonishing if they hadn't since they go against the official paradigm. But that is not the same as being disproven. Professor Cohen has, in turn, vigorously criticised the criticism. I do not know if Chen has done the same but have seen no evidence that he has acknowledged being wrong.
I don't know if you are right about Coulter exaggerating mammogram evidence but it is a minor point and certainly does not justify Orac's "versus science" allegation. If we required that popularisations of science were always 100% accurate I doubt that any of them would pass muster.
On the paper you cite http://www.pnas.org/content/100/24/13761.full - I have read it (well the abstract) and it does not disprove, indeed barely touches on hormesis. It says there is evidence to support LNT down to 50-100 mSv (a remarkably unspecific amount for science), for non-instant exposures, but nothing below this, allegedly because of the difficulty of finding a large enough statistical population to be affected by lower levels). This conflicts with evidence from areas, such as south India where there is a background radiation of up to 200 mSv with no visible damage. It is also not entirely compatible with the radium paint experience where, as Professor Wade Allison has pointed out, there appears to be a cut off point at 10 gray (100,000 mSv) for a whole life exposure, causing no damage. Nonetheless it is irrelevant for any case of a hormetic effect under 50 mSv - 3 times the official danger level and one most hormesis supporters are willing to accept as a first approximation.
In fact the paper is clearly wrong about it being impossible to find larger populations exposed to lower levels. The entire world is exposed to levels of natural radiation, varying in easily measurable ways by region and the much higher exposure of people in Colorado than Mississippi is undisputable. This is the basis of Professor Cohen's work and that of the Swedish oncologist mentioned. Why the paper should make such an untrue assertion we can only speculate on.
I look forward, Kreboizen, to your assessment of the various links to evidence I have provided. I realise it may take some time since the evidence for hormesis is so extensive.-----Neil
130 Neil, here's what I found when I looked at the first 23 links on your blog. I hope it's clear which are my comments and which is the material linked to. I'm sorry I repeat myself in places. I have found some interesting bits of information that I think have been misinterpreted to mean hormesis, which I will write about separately.
1. http://www.alamut.com/proj/98/nuclearGarden/bookTexts/Rad_hormesis.html
An article dated 1988 "scavenged from the net" that proposes a conspiracy theory among health physicists and seems to be based on the work of Marshall Brucer who was employed by the United States Atomic Energy Commission. Has 4 links, 3 of which go nowhere, and one links to the article written by Javad Mortazavi mentioned below. There are no useful references and some very dubious claims.
2. http://www.angelfire.com/mo/radioadaptive/inthorm.html
An article written by an Iranian scientist, S. M. Javad Mortazavi arguing that "the existence of radiation hormesis and adaptive response are not deniable".
Experiments with mice found that if they were exposed to 2 Gy 60Co gamma-rays 46% of them developed thymic lymphoma, but if they were repeatedly given doses of radiation, lower rates of cancer were observed (17%). What were the cancer rates in mice that were not irradiated at all
Another study found that low dose pre-irradiation of mice before a mid-lethal dose improved survival (from 486 to 578 days), but mice not irradiated at all lived much longer (727 days).
http://www.wmsym.org/archives/2001/2/2-2.pdf
The rest of the article talks of atom bomb survivors, background radiation studies and nuclear power workers. I have mentioned all these areas before, noting that there is no agreement about what they prove or don't prove. Javad Mortazavi does not appear to have published anything in peer-reviewed journals - nothing on Pubmed I can find anyway.
3. http://www.jpands.org/vol9no1/chen.pdf
A 2004 article about the Taiwan apartment contamination with cobalt 60.
The article states that, "the age distribution of the exposed population has not yet been determined, and it was assumed that the age distribution of the exposed population is the same as that of the general Taiwan population" which was an erroneous assumption. In a more recent study, "cancer risks were compared with those populations with the same temporal and geographic characteristics in Taiwan by standardized incidence ratios (SIR), adjusted for age and gender." and concluded, "all solid cancers combined were shown to exhibit significant exposure-dependent increased risks" in those exposed before the age of 30.
http://informahealthcare.com/doi/abs/10.1080/09553000601085980
4. http://radiationhormesis.vpinf.com/index.html
Vinny Pinto's website. Pinto is a mystic and healer with some very peculiar beliefs. Interesting, but not what I would call a reliable source. His site links to a site selling "healing" radioactive stones. http://www.vinnypinto.us/
5. http://www.lewrockwell.com/miller/miller12.html
An article by a Dr Donald W. Miller who trots out the same old "evidence" as other sites. Miller has some unusual ideas, judging by his website: http://www.donaldmiller.com/
6. http://enochthered.wordpress.com/category/radiation-hormesis/
A blog post about radon and lung cancer. An interesting blog generally, worth a read. More recent larger studies show that radon undoubtedly is a major cause of lung cancer. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2853156
7. Dead link. Is supposed to link to an article by Prof. John Cameron, who was a proponent of radiation hormesis, that discusses how British radiologists live longer than other doctors, but doesn't. The longevity of British radiologists disappears when they are compared to other medical specialists. "We conclude that the low mortality of British radiologists who were registered in the period 1955–1997, in comparison with that for all medical practitioners, is attributable to the factors that cause a relatively low mortality in doctors in all medical specialties. There is no reason to attribute it to a specific benefit from exposure to low doses of ionizing radiation." http://bjr.birjournals.org/cgi/content/full/78/935/1057
An American study concluded:
"Radiologists had an excess in all-cause mortality rates compared to the other specialists for all cohorts who entered the Radiological Society of North America before 1940; the excess remained even when the cancer deaths were removed from the rates. These data are consistent with the concept of accelerated aging due to radiation. The cancer mortality rates for radiologists were higher than those of other specialists for an additional decade through 1949. The 1950-1959 cohort had not aged sufficiently to demonstrate the expected peak cancer mortality in the 60-64 year age group".
http://aje.oxfordjournals.org/content/101/3/188.full.pdf+html .............
9. http://www.world-nuclear.org/sym/1998/cohen.htm
An interesting article by Bernard Cohen, but somewhat undermined by more recent and better data on radon and lung cancer.
10. http://www.alamut.com/proj/98/nuclearGarden/bookTexts/Rad_hormesis.html
The same as the first link above. The claim that cows were euthanized to cover up the positive effects of radiation because they refused to die from radiation poisoning is hilarious (sorry Neil). There is no primary source for the existence of these cows, the dose they got, if or when they were euthanized. I have spent a long time searching but failed. Neil still manages to squeeze a conspiracy theory out of this. Even if a few cows did survive, we don't know how many other cows succumbed to radiation poisoning or cancer.
http://a-place-to-stand.blogspot.com/2010/03/radiation-hormesis-they-worlds-oldest.html
11. http://www.angelfire.com/mo/radioadaptive/
The same S. M. Javad Mortazavi website linked to above. He seems to be affiliated with the nuclear industry through the Iranian Nuclear Regulatory Authority and the IAEA.
12. http://www.docstoc.com/docs/24368147/Introduction-to-Low-Level-Radiation-Effects-for-15PBNC
A document that requires a paid membership to docstoc.com to access it, and that I cannot find elsewhere.
13. http://www.ncbi.nlm.nih.gov/pubmed/3570800?dopt=Abstract
Cohen's 1987 paper on radon and lung cancer, refuted by more recent, better designed and much larger studies. For example: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2853156/?tool=pubmed
14. http://pinnacle.allenpress.com/doi/abs/10.1667/RR1199.1
A study on HeLa cells that found a small dose of radiation (.4-4 mGy/day) given before a larger dose (3-Gy) reduced neoplastic changes in the cells induced by the larger dose. Claiming this adaptive response as evidence of hormesis seems ridiculous to me.
15. http://interactive.snm.org/docs/SNM_ANMC_Comment_Letter_to_NRC_Feb_2010.pdf
A letter from the American College of Nuclear Medicine (which promotes the use of nuclear medicine) and the Society of Nuclear Medicine to the U.S. Nuclear Regulatory Commission objecting to proposals to lower the annual limit of radiation exposure for workers from 50 mSv to 20 mSv. The ICRP (which is an independent non-governmental organization) explains the reasons for the proposed changes here: http://www.nrc.gov/about-nrc/regulatory/rulemaking/potential-rulemaking/opt-revise/icrp-pub-103-free-extract.pdf
16. http://www.arps.org.au/?q=content/sa-branch-seminar-march-2010
An advert for a seminar titled 'Low Dose Radiation Effects: A Biological Reality Check'. I found a transcript of what I think is the whole talk here: http://www.wmsym.org/archives/2001/2/2-2.pdf
Cell culture studies seem to show hormesis, but studies on mice found that mice exposed to 1.0 Gy dose lived 486 days, but of they were exposed to 0.1 Gy 24 hours before the 1.0 Gy dose, they lived for 578 days. However, mice not exposed to radiation at all lived for 727 days. If I was a mouse, I would stick with getting no radiation at all.
17. http://gulfnews.com/life-style/health/radiation-exposure-benefits-of-a-risk-1.590944
A newspaper article about a particle physicist who thinks that low dose radiation does no harm, but also talks to three other scientists, Professor Gillies McKenna of Oxford University, Cancer Research UK's expert on radiation oncology, Richard Wakeford, an epidemiologist specializing in the health effects of radiation at the University of Manchester who disagree with him, and think the LNT is the best approach.
18. http://www-formal.stan/
ford.edu/jmc/progress/linear.html
A short piece on the LNT by Professor John McCarthy of Stanford that claims there no direct evidence for the LNT and a lot of evidence against it. It is at least 10 years old (page last modified in 2000), and is out of date - most of the links on the page are dead. The evidence against the LNT mentioned is:
Hiroshima and Nagasaki survivors - others interpret the data differently, pointing out that those who survived the initial radiation may be more resistant to disease, and not be a representative population. Gofman has pointed out several changes in the data sets made retrospectively which is problematic with a prospective study.
Natural background radiation and high radon in some areas does not lead to increased cancer, it claims. More recent studies suggest this is incorrect (sorry to keep repeating myself).
http://iopscience.iop.org/0952-4746/29/2A/S03/pdf/0952-4746_29_2A_S03.pdf
19. http://www.environmental-expert.com/books/radiation-hormesis-and-the-linear-no-threshold-assumption-30922
A link to a book 'Radiation Hormesis and the Linear-No-Threshold Assumption' by Charles L. Sanders which costs over $200. "The author shows how proponents of the LNT assumption consistently reject, manipulate, and deliberately ignore an overwhelming abundance of published data and falsely claim that no reliable data are available at doses of less than 100 mSv" Most of the abundant data I have seen doesn't seem to support this, and I have no inclination to cough up $200 for this book.
20. http://ehp.niehs.nih.gov/members/1998/Suppl-1/363-368pollycove/full.html
A 13 year old article by Myron Pollygrove who worked for the U.S. Nuclear Regulatory Commission. Based on a 1996 presentation at a BELLE conference. BELLE is a government and industry based group formed to promote the safety of low level radiation
21. http://en.wikipedia.org/wiki/Ramsar,_Mazandaran#Radioactivity
A Wikipedia article about Ramsar which has a very high background radiation in some areas. Only about 1000 people live in the high background radiation areas which is not enough to estimate whether cancer risk is increased. Mean annual dose in Ramsar is 6 mSv which would only lead to an expected 0.06% increase in cancer, or less than 1 additional cancer in 1000 people. In fact small increases in cancer have been observed in Ramsar.
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/CancerRisk.html
http://iopscience.iop.org/0952-4746/29/2A/S03/pdf/0952-4746_29_2A_S03.pdf
http://tinyurl.com/6c45qar
22. http://www.numberwatch.co.uk/vocabulary.htm
A humorous redefinition of some words.
23. http://www.ecolo.org/documents/documents_in_english/taiwan-cobalt-60-apartmt-04.htm
A letter written to New Scientist magazine by Neil Craig. It is about the Taiwan cobalt 60 incident, again. I have explained above why this is wrong. Neil concludes, "there can no longer be any intellectual doubt whatsoever. Radioactivity in low doses is good for us". I'm sure he has changed his mind based on the better information now available i.e. "all solid cancers combined were shown to exhibit significant exposure-dependent increased risks". http://informahealthcare.com/doi/abs/10.1080/09553000601085980 ----Kreboizen
132 An extensive piece of work Kreboizen. Lets go through it.
1 - intended to be an overview and that is what it is.
2 - That he is Iranian may be less important, in scientific terms, than the extensive evidence given. The link you introduce shows that even at 2 Gy (200,000 mSv) living organisms can be acclimatised to radiation. It is irrelevant to whether there is a hormesis effect at under 50 mSv
3 - Your article disputing the Taiwan results looks rather like a data dredge. The quote you ge extended says "all solid cancers combined were shown to exhibit significant exposure-dependent increased risks in individuals with the initial exposure before the age of 30, but not beyond this age". Not only is this confirming no LNT effect above 30 but if you divide a population into a large number of small groups (e.g. those under 30 in an initial population of 10,000) you are statistically certain to get more than one showing an above average effect. As I have said I would like to see Professor Chen's response to this or the results being verified by somebody without a preconceived view.
4 - Indeed. Such stuff is anecdotal and I would never rely on it alone. On the other hand the fact that, for several thousand years, people have been "taking the waters", usually fairly radioactive waters from springs deep underground, is as strong as anecdotal gets.
5 - Orac won't like his ideas. I do. He is certainly well qualified to have medical opinions.
6 - I agree that the evidence given is "interesting". Your link "disproving" hormesis doesn't actually produce any research of its own it merely refers to other published claims. A major problem with meta studies is that the studies aggregated are selected both by the new author and by the original ones - scientific studies which produce "anomalous" results are more likely to be done again than published.
7 - I will correct that link thanks. Your counter links disputing this effect is normal scientific discussion. I note that the British dispute is based on saying that all British doctors are more than averagely healthy while the American one says that most American ones are below average.
8 - If I can't find it I will delete.
9 - As I said Cohen has vigorously disputed his disputants. I think the evidence is clear.
10 - I don't know what you mean about there being no primary source. My post you give links to both that the cattle were irradiated by the trinity A-Bomb test in 1946 and that they were put to sleep in 1964. That means that statistically some of them must have reached or exceeded the maximum age of cattle, 22 years. Killing this evidence was clearly a scientific crime.
11 - As above.
12 - No comment needed
13 - The alleged refutation is the same link discussed in #6.
14 - 3 Gy is as previously discussed, far higher than hormesis is claimed at. What this does do, however, is disprove that there is a consistent Linear No Threshold effect even at such high levels.
15 - No comment needed.
16 - As you acknowledge "Cell culture studies seem to show hormesis". If I were a mouse I would not want a Gy scale exposure either.
17 - Of course the newspaper will cover itself by asking for a soundbite of the official view. How is this unexpected or more important than what the article is about.
18 - If 10 years ago is to long to listen to Professor McCarthy (I don't think it is) then LNT, as a 60 year old theory adopted without evidence at the time is surely further away. Your link does not mention "hormesis" and is simply about the difficulties of research. "Nevertheless, the risk of exposure to radon
indoors in the domestic environment has long been questioned. About 20 ecological studies
have been performed since the 1980s, but due to methodological limitations these studies
proved unable to answer the question." (by which they mean they keep coming up with the wrong answer) is typical of the "there is no evidence so trust us" line of thought.
19 - So no further comment required.
20 - So " " " "
21 - Your first link says "In some houses in Ramsar, Iran, the inhabitants are exposed to an annual dose of background radiation of as much as 130 mSv per year — over 70 times that in Colorado. Nevertheless, the inhabitants of Ramsar are just as healthy as — or even healthier than — control populations exposed to far lower levels of radiation." The 2nd has already been dealt with in 18. The 3rd link isn't working.
22 - No further comment.
23 - Your link has already been dealt with in #4
What seems undeniably clear is that there is no actual evidence for the LNT theory and indeed that its supporters rely on it being allegedly impossible to prove it at the low end, because of the large size of population needed. You will be aware that a key requirement of any scientific theory is that it be "falsifiable" i.e. proven wrong. Personally I think most unfalsifiable theories (LNT, catastrophic warming, withcraft, creationism, flat earth are indeed falsifiable it just thaty their supporters are to stubborn to look). However, if the LNT supporters are correct then LNT cannot be counted as science
I would welcome any suggestion of what would provide falsifiability for LNT.
Hormesis supporters do not claim unfalsifiability and point to the natural background radiation, which can be determined and show Colorado not to have a higher cancer rate than Mississippi. The experimental statistical evidence for it in plants & cultures seems undisputed.----Neil
133 I want to answer an earlier comment from Neil. To be honest, I have read so much about radiation exposure over the past few days it's starting to drive me crazy. I'll post a summary of what I think I have learned about this in the next day or two, as it may be of use to someone.
I think you are wrong to say that Professor Cohen's work and that of Professor Chen (Taiwan) are "known to be wrong". They have both been disputed. It would be astonishing if they hadn't since they go against the official paradigm. But that is not the same as being disproven. Professor Cohen has, in turn, vigorously criticised the criticism. I do not know if Chen has done the same but have seen no evidence that he has acknowledged being wrong.
Well I think Professor Cohen has fallen foul of the ecological fallacy, averaging cancer rates and radon exposure in US counties and expecting to find a meaningful result. This is not how epidemiology should be done and the negative correlation he found between radon exposure and cigarette smoking both demonstrates this and explains his findings.
As for Chen, I don't see how you can continue to defend a study of cancer rates that failed to take age demographics into account, when a study that used matched controls is available.
I don't know if you are right about Coulter exaggerating mammogram evidence but it is a minor point and certainly does not justify Orac's "versus science" allegation. If we required that popularisations of science were always 100% accurate I doubt that any of them would pass muster.
It wasn't mammogram evidence, it was high dose chest x-rays of patients with TB that did not cause as much cancer as you would expect from such high doses. The original paper concluded, "the risk of breast cancer associated with radiation decreases sharply with increasing age at exposure and that even a small benefit to women of screening mammography would outweigh any possible risk of radiation-induced breast cancer." In other words if you dose older women with x-rays, the increased risk of cancer is outweighed by the benefits of early detection of breast cancer. The article by Kolata that Coulter gives as a source of the information says, "the tuberculosis patients, some analyses said, had fewer cases of breast cancer than would be expected." Coulter misinterprets this, writing, "tuberculosis patients subjected to multiple chest X-rays had much lower rates of breast cancer than the general population". This is not a minor point. Coulter has not bothered to track down the original source and has written something that is opposite to the truth. At a minimum this is sloppy and irresponsible journalism.
On the paper you cite http://www.pnas.org/content/100/24/13761.full - I have read it (well the abstract) and it does not disprove, indeed barely touches on hormesis. It says there is evidence to support LNT down to 50-100 mSv (a remarkably unspecific amount for science), for non-instant exposures, but nothing below this, allegedly because of the difficulty of finding a large enough statistical population to be affected by lower levels).
The article is not about hormesis, I never said it was. It is about why the LNT is accepted as the safest assumption to make about low level exposure.
This conflicts with evidence from areas, such as south India where there is a background radiation of up to 200 mSv with no visible damage.
How do you know how much damage there is there? What control population do you use to establish this? Where is the matched control study of this exposed population? The one case control study I could find found that lung cancer was 2.3 times more common where the external dose was greater than 10 mGy per year, though this was not statistically significant. The study, which I can't find on-line, is this: Binu VS, Gangadharan P, Jayalekshmi P, Nair RRK, Nair MK, Rajan B and Akiba S 2005 The risk of lung cancer in HBR area in India—a case–control study High Levels of Natural Radiation and Radon Areas: Radiation Dose and Health Effects ed T Sugahara and Y Sasaki. It is cited in this study.
It is also not entirely compatible with the radium paint experience where, as Professor Wade Allison has pointed out, there appears to be a cut off point at 10 gray (100,000 mSv) for a whole life exposure, causing no damage. Nonetheless it is irrelevant for any case of a hormetic effect under 50 mSv - 3 times the official danger level and one most hormesis supporters are willing to accept as a first approximation.
Even assuming this is correct, and the data collected several decades ago is reliable, exposure to radium may not be typical of other exposures to radiation. The number of exposed workers examined (less than 3000) may be too small to find a statistically significant effect consistent with the LNT against a background of normal cancer rates. The cut-off below which there is no measurable effect is between 4 and 11 microcuries radium according to this paper. I'm not sure how that translates into mSv. By the way, I can't find any information about "the 30 year followup of 1155 low dose radium dial painters who had fewer cancers than the general population and lived longer".
If you look at the Hiroshima and Nagasaki survivors, >50% of them had a dose of less than 50 mSv. Even those with a dose of 34 mSv showed a statistically significant increase in cancer risk.
http://www.pnas.org/content/100/24/13761/F2.expansion.html
In fact the paper is clearly wrong about it being impossible to find larger populations exposed to lower levels. The entire world is exposed to levels of natural radiation, varying in easily measurable ways by region and the much higher exposure of people in Colorado than Mississippi is undisputable. This is the basis of Professor Cohen's work and that of the Swedish oncologist mentioned. Why the paper should make such an untrue assertion we can only speculate on.
The problem with that approach is that there are confounding factors. There may be many reasons why cancer rates in Colorado and Mississippi are different. You have to take age, smoking and socioeconomic status into account for a start. You need a control group matched for all those factors. That's where it gets messy, and small changes in corrections for age, or other factors can have major effects on the results.
I still maintain that the evidence for hormesis or a threshold dose of radiation in humans is far from overwhelming. ------ Kreboizen
134 The difficulty of assessing statistics, "ecological fallacy" or otherwise cuts both ways and is inherently as likely to lead to an underestimate of hormesis. For example your 2nd link says:
"Population density is strongly positively associated with lung cancer. It follows that aggregate residential radon and lung cancer rates should be negatively associated for reasons having nothing to do with the possibility of radon being carcinogenic to the lung."
It is not inherently likely that population density would cause lung cancer. A more likely reason would be that areas where high populations develop tend to be flat fertile soil rather than mountains but mountains contain more radioactive rock. This does not seem to have been noticed.
As your paper accepts there is no real evidence for LNT below 50 mSv it is simply an assumption.
On the evidence for south India that is why I said there is "no VISIBLE damage". Since 200 mSv is 10 or more times above "official" danger levels if that is justified one would expect some noticeable effect.
Exposure to radium being seriously different from all other sorts of radiation is an assumption without evidence. Moreover if it were the case there would be a 50:50 chance that it underestimated the hormetic effect rather than overestimated it. A lot of countering of hormesis seems to rely on the possibility of there being unknown confounding factors which (A) becomes increasingly statistically less credible the more times it is invoked and (B) is not evidence for the counter theory, but for more research.
I would welcome more research on the subject & I think we would agree on that. Scientific questions can be opened by debate but are closed by enough good research. More good research would find if there are enough confounding factors or not. It would either raise the level of evidence for hormesis to "overwhelming" or reduce it.
I believe that the acceptance of LNT, on grounds of bureaucratic convenience, the general failure to do the research and particular instances such as killing the exposed cattle when they embarrassed the LNT theory indicates that the science has been driven by political conclusions rather than the other way round.---- Neil
135 As promised, here's a summary of what I think I have learned about low dose radiation, hormesis and the linear no threshold theory. I'm no expert, but the links supporting my conclusions are above. Any new links I have included below.
Evidence for and against hormesis and the LNT
Theoretical evidence
There are arguments for both that seem equally persuasive to me. It seems self-evident that DNA repair mechanisms cannot be 100% effective as otherwise radiation even in high doses would not cause cancer, but it does (Gofman). However, if protective mechanisms induced by radiation repair more damage from other sources than is caused by the radiation, then hormesis may occur (Pollycove and Feinendegen).
Experimental evidence
Plants, trees algae etc
Some evidence show that low level radiation stimulates the growth of plants, fungi, algae, protozoans, insects, and nonmammalian vertebrates. It is not clear if that is true at all levels of exposure, all types of exposure and with all isotopes. Anyway, this does not mean that the same is true for humans.
Cell cultures - human and animal
Some studies show a protective effect of a small dose of radiation before a larger one is given, the radioadaptive response. Some studies show that cells have fewer cancerous changes with low doses of radiation than those with no radiation. Other studies find that even small doses of radiation cause damage in line with the LNT. Low-dose hypersensitivity has also been demonstrated.
As Dr. Luckey states:
"Except for cytology and cells in culture, artificial systems which lack participation from whole body faculties (particularly the immune system), there is no reasonable or scientific proof of LNT at low doses of ionizing radiation." http://www.radpro.com/641luckey.pdf
In other words Luckey is saying that there is reasonable scientific proof of the LNT at low doses of ionizing radiation in cytology and cells in culture. As he says, whether this translates to humans is not known.
So the evidence in cell culture is equivocal. The important thing is whether it translates into real effects in humans.
Animal studies
Some animal studies show short term health benefits from low dose radiation, especially in infected animals, but later a higher risk of cancer. Radioadaptive responses occur in mice, but mice not dosed with radiation at all live longer. Very low dose studies require too many animals to get statistically significant results. Data are equivocal.
Luckey http://www.radpro.com/641luckey.pdfgives several examples of radiation hormesis in animals, but these are all animals with diptheria, vesicular stomatitis virus or other infections.
To quote Luckey: "This graph exposes the misinterpretation to conclude that control mice have longer average life-spans than the exposed mice when the median value was used instead of mean or average. The disbelief spread when major laboratories were misled by repeating the Lorenz protocols with specific pathogen-free (SPF) animals. Since SPF animals have no pathogens to cause infection, controls lived as long as irradiated mice and no hormesis was found."
In these sorts of experiments the median (middle value of values arranged in order) is often used as it is not distorted by an abnormal distribution, In a normal distribution (bell-shaped curve) the median and the mean are the same. If the mean and the median are very different, there is not a normal distribution. Median survival is a very fair way of expressing results, as half the animals lived for fewer days, and half lived for more days.
Notice that Luckey states that in normal uninfected mice, "controls lived as long as irradiated mice and no hormesis was found". This is what the LNT would predict, as you would have to irradiate many thousands of mice to see the small increase in mortality predicted after such a small dose (1.1mGy/d or 40 rad per year about 100 times average background).
However, another experiment does show a significant increase in lifespan in mice exposed to 7 or 14 cGy/year (7-14 rad) which is around 20 times background radiation. This is the only experiment I can find that shows an increase in animal lifespan with low dose radiation.
http://www.blogger.com/goog_804070127
Which of these studies is right? Can they both be right? Maybe 20 times background is beneficial, but 100 times background is not. Anyway, humans are not mice, and we cannot extrapolate directly from mice to humans.
Another study using mice that are hypersensitive to whole body x-rays found a very low dose (1 micro Gy or 0.0001 Rad or 0.1 mRad) that caused damage, a higher dose that was hormetic, and a higher dose than that which caused damage. This may explain some of the conflicting evidence. By the way, some humans are also hypersensitive to radiation.
http://www.jstor.org/pss/3581207
High background radiation studies
These are plagued by confounding factors, limited populations and difficulties matching exposed and control populations. The data are equivocal apart from radon, which recent studies strongly suggest is a major cause of lung cancer in line with LNT predictions. Combined figures from the whole of Europe, the USA and China give a large population which generates considerable statistical power.
Occupational exposure to low dose radiation
These studies are plagued by confounding factors, limited populations and difficulties matching exposed and control populations. The data are equivocal.
Atomic bomb survivors
Except for higher dose studies, these are plagued by confounding factors, limited populations and difficulties matching exposed and control populations. The data are equivocal, though statistically significant increased risk of cancer has been found at levels as low as 34 mSv.
There are eminent scientists who are convinced that radiation is good for us. There are equally eminent scientists who believe that radiation in low doses is harmless. There are equally eminent scientists who believe we have the safety regulations about right (the majority, apparently). There are equally eminent scientists who believe that low dose radiation is far more dangerous than we currently think. This disagreement suggests that the data are equivocal, and that there is a considerable degree of uncertainty.
I tend to agree with the National Academy of Science study which suggests that in the face of such uncertainty we should be cautious. Though we know that low levels of radiation must have a very small (if any) positive or negative effect on individuals, when large populations are exposed large numbers of people may be affected. The costs of maintaining current safety regulations must be balanced against the possibility of thousands of excess cancers if they are relaxed.
There are scientists who think that hardly anyone has died as a result of Chernobyl, and those who believe that hundreds of thousands have died.
A word on epidemiological studies
There are populations that have been exposed to relatively large doses of radiation. For example the survivors of Hiroshima and Nagasaki. Following these survivors should give us a good idea of the long term effects of radiation, you might think. For large doses it does, and this is part of the data used to construct the LNT curve. However, there are potential problems with the data. Firstly, these are survivors. It is not unreasonable to suggest that more of those vulnerable to radiation would have died shortly after the bombs were dropped. The survivor population may or may not be comparable to the control population. Which brings me to the next problem - what control population do you use? The Japanese population not within range of the atom bombs is usually used, but is this a fair control group? Was the population of Japan exposed to radioactive fallout? Are we comparing one exposed population to another? I don't know the answer to that question. Sternglass claims that leukemia rates in Japan increased by a factor of 5 after 1945, but I can't find the primary data, and Sternglass is not considered a reliable source by many.
Parts of Ramsar in Iran have very high background radiation (55-200 times average background), and 10,000 people live in the high radiation area so it should be simple to determine if there is an increased cancer (or other disease) rate in this area. In practice it doesn't seem so straightforward. If you go to http://www.sciencedirect.com/ and type "Ramsar" into the search box, you will get several studies, some of which find lower cancer rates, some that find no effect and one that finds an increased rate. Who do you believe?------ Krebiozen
136 OK I am glad you accept the experimental evidence of hormesis in plants, cultures and animals. Once it is accepted an effect exists the rest is measurement of degree and where, if anywhere, the effect stops both in radiation level and complexity of the organism (I realise how much of a simplification that is). If it is found in one in one part of the living world the default assumption is that we would expect it elsewhere, unless there is evidence to the contrary.
My reading of Luckey is not yours. I suggest that what that phrase means is that he had not searched for hormesis in cells which "lack participation from whole body faculties" ie lack an immune system, because it an immune system is essential for the hormesis theory rather than that he had investigated and found it missing. If he, or anybody else, had investigated I submit it would have been published properly not as an arguable implication in a throw away line.
I think it reasonable to believe 20 times (app 40 mSv) background is hormetic but 100 times (app 200 mSv) not. That latter figure is about 50% above the Ramsar background. Both are above official danger levels from which we are assured government regulation is "protecting" us.
You are exaggerating in describing the possibility of "thousands" of extra cancers if regulations are relaxed. Nobody is suggesting a relaxation that would allow nuclear plants to normally emit even 1/10th as much as coal plants currently do (50 times more than nuclear ones http://a-place-to-stand.blogspot.com/2009/05/menace-of-radioactivity-released-by.html) , let alone TMI or Fukushima, both of which have killed nobody. So, even were LNT true, a relaxation would be unlikely to kill as many as a handful (in fact if it replaced coal plants it would, assuming the LNT theory, be directly beneficial). Of course if it provides heat for people through the winter it would save millions worldwide.
I cannot agree with your assertion that radon has unequivocally been proven harmful. There have been many studies on this precisely because they kept coming up with the "wrong" answers. It is unsurprising that somebody has managed to come up with the "right" answer but Cohen's, which found a hormetic effect half of the damaging effect of smoking seems to have been professionally conducted. This is another on radon http://enochthered.wordpress.com/category/radiation-hormesis/ "described by their own authors as “surprising” and “stunning”: Clear evidence of radiation hormesis"
On your surprise that some studies show hormesis and some are consistent with LNT may I suggest this answer from Richard Feynman's speech on cargo cult science.
"Millikan measured the charge on an electron by an experiment with falling oil drops, and got an answer which we now know not to be quite right. It's a little bit off, because he had the incorrect value for the
viscosity of air. It's interesting to look at the history of measurements of the charge of the electron, after Millikan. If you plot them as a function of time, you find that one is a little bigger than Millikan's, and the next one's a little bit bigger than that, and the next one's a little bit bigger than that, until finally they settle down to a number which is higher.
Why didn't they discover that the new number was higher right away? It's a thing that scientists are ashamed of--this history--because it's apparent that people did things like this: When they got a number that was too high above Millikan's, they thought something must be wrong--and they would look for and find a reason why
something might be wrong. When they got a number closer to Millikan's value they didn't look so hard. And so they eliminated the numbers that were too far off, and did other things like that."
http://www.lhup.edu/~DSIMANEK/cargocul.htm
The entire speech should be read by anybody interested in scientific integrity.
In this case LNT is, like Millikan's case but very very much stronger because it is so heavily politically backed, the official theory which any experiment must conform to. It is to their considerable credit that such a significant number of scientists have found - and published - the evidence for the non-official theory. --- Neil
However in due course 1 LNT supporter with "30 years experience" in the field did engage in a serious discussion and I think that worth extracting and preserving since I know of no other public debate on the subject. There was some movement. You will have to judge the result for yourselves.
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106 Here's a whole book full of evidence that the LNT hypothesis is flawed, in the opposite direction to that claimed by Neil Craig. If anyone can point me to a refutation of Gofman I would be grateful. I find his arguments very convincing. Neil Craig simply dismisses any evidence he doesn't like as propaganda from the anti-nuclear lobby.
Posted by: Krebiozen
April 30, 2011 5:18 PM
109 Kebriozin you clearly don't know that Gohman, your further than LNT scare teller, is actually the man who invented the LNT theory, without the inconvenience of first looking for evidence.
He also predicted, on the basis of it, half a million deaths and half a million non-fatal cancers as a result of Chernobyl. The total death toll is actually 56 which is strong evidence his theory is wrong.
110 Neil, I do know that it was Gofman who proposed the LNT. I don't see why that means he was wrong. He based it on experimental evidence and on epidemiological evidence. The National Academy of Sciences agreed with him.
Here's an article published by the National Academy of Sciences about the LNT that explains why I think Coulter's and your arguments are nonsense. It concludes:
In summary, given our current state of knowledge, the most reasonable assumption is that the cancer risks from low doses of x- or γ-rays decrease linearly with decreasing dose. In light of the evidence for downwardly curving dose responses, this linear assumption is not necessarily the most conservative approach, as sometimes has been suggested, and it is likely that it will result in an underestimate of some radiation risks and an overestimate of others. Given that it is supported by experimentally grounded, quantifiable, biophysical arguments, a linear extrapolation of cancer risks from intermediate to very low doses currently appears to be the most appropriate methodology.
Please note the reference to, "experimentally grounded, quantifiable, biophysical arguments".
As for your claim that only 56 people died as a result of Chernobyl, even the IAEA estimates that "several thousand" people are likely to die. Other estimates are considerably higher. Given changes in the former USSR, and the background noise of deaths due to other causes, it is difficult to know which estimates are more accurate. --------Posted by: Krebiozen
111 Neither they, you, nor Gohman have produced this alleged experimental evidence, which is not how one does science. Extrapolating from high dosages is ridiculous and would lead you to say that because there is a 100% chance of dying if a falling elephant lands on your head there is a 0.1% chance of death every time you put a hat on. Science doesn't work on such assumptions either.
The 4,000 predicted (not actually happening) is predicted from the LNT theory (as indeed was Gohmans 1 million which obviously didn't happen). Justifying a prediction by saying the predictor predicted it and predicts that he is right is silly for reasons which will be obvious to anybody capable of logical thought. The failure of the 1 million prediction to be realised in real life, or even a tiny measurable fraction thereof, is, on the other hand, proof positive that LNT is wrong. ---------Neil
112 - Neil, have you actually read any of the material I have linked to? The National Academy of Sciences paper has 64 references, most of them to primary research papers. Gofman has copious references to primary research that supports his arguments. Just because you refuse to acknowledge or respond to this evidence doesn't mean it doesn't exist. The Hiroshima and Nagasaki data cited in the NAS paper seems very convincing to me.
Your elephant analogy demonstrates how little you understand this subject. The minimum possible dose of radiation is a single electron track, which can potentially hit and damage DNA, thus causing cancer. This has been demonstrated in laboratory experiments. The more electron tracks, the higher the chances that one of them will damage DNA. As DNA repair mechanisms are not 100% effective even a single electron track can induce cancer.
A better analogy might be someone firing a shotgun at you with a varying number of pellets in the cartridge. A single piece of shot is unlikely to hit and kill you, but it is possible it might. The more shot in the cartridge, the higher the chances of death.
Just because it is difficult or impossible to demonstrate with statistical significance how many people have died or will die as a result of Chernobyl does not mean that no one has died. Even a million excess deaths over 25 years in the whole of Europe would be very difficult to measure against background mortality from other causes. To suggest that it is certain there have not been 4000 excess deaths is ridiculous.
Scientists from the former USSR have published several papers suggesting that the death toll from Chernobyl is much higher than WHO and IAEA estimates. See 'Chernobyl: 20 Years On - Health Effects of the Chernobyl Accident' published by the European Committee on Radiation Risk and A. Yablokov's 'Chernobyl: Consequences of the Catastrophe for People and the Environment' published by the New York Academy of Sciences.
Incidentally, the European Committee on Radiation Risk has just released a report using two different methods that estimates between 489,500 and 2.45 million excess cancers caused by Chernobyl over 50 years.
http://euradcom.org/2011/chernhealthrept3.pdf
I don't pretend to know for sure which of the many estimates is correct, but until we do know, it is sensible to apply the precautionary principle. I think you are suffering from premature certainty. -------Krebiozin
113 At the very least you are acknowledging that you are not relying on scientific evidence but on the "precautionary principle".
In which case Ann Coulter has at least as much right to rely on the science.
And Orac & supporters owes her a public apology for accusing her of opposing "physics". An apology which would obviously have been given days ago by Orac & supporters had any of them not been corrupt eco-fascists merely pretending to have a respect for the rules of science. QED.
If you don't like my elephant example here is another. The LNT theory says that risk is wholly proportional to exposure. Therefore the risk is proportional to both the amount of "shots" (ie radiation) and the number of targets (cells). Thus multicellular animals like elephants are, if the theory is not crap, a billion times more susceptible than small ones and elephants drop like flies, from cancer whereas flies don't.
Obviously this is not how the real world works hence the theory is crap QED. As I have pointed out there is a vast amount of other evidence and it is clear that, had science been involved rather than politics, LNT would have been dumped generations ago.--- Neil
115 @Scottynuke
I'm aware that the NYAS only published Yablokov's book and doesn't stand behind his findings. I wasn't meaning to suggest the NYAS endorse his work (it is available free through a link on the llrc.org website BTW). I still wonder a bit when Gofman's estimates seem to supported by the findings of Soviet scientists. I'm a bit uneasy about dismissing all their work too easily. I wonder if the dangers of low dose radiation might be greater than the LNT suggests.
In essence the radiation dose response curve disappears at the low end into a mush of noise and confounding factors sufficient to hide a very large number of deaths. We don't know if the curve is linear or if it curves up or down for any or all types of exposure to any or all types of isotopes. Any population big enough to calculate a statistically significant increase in deaths suffers from a lack of a suitable control group.
The increases in mortality from various causes documented in the former USSR may or may not be due to Chernobyl. Several of the studies I looked at found a greater increase in mortality where dose was greater. I don't know what other evidence we might hope to find.
Neil - what you seem to be referring to about cancer in different sized animals is known as Peto's paradox.
It's an interesting point, but I don't think it's a good argument against the LNT. We have no idea how many cancerous cells arise in elephants but fail to develop into observable tumors, as compared to those in smaller animals. Less external radiation would get through an elephant's thick skin to damage vulnerable dividing cells than in a mouse, for example. External and internal radiation have different effects. It's not as simple as you suggest.
I'm intrigued by the "vast amount of evidence" you mention that the LNT is wrong. All the evidence I have seen for radiation hormesis in humans has been effectively debunked, in the same way that Orac has demonstrated that Coulter's claims are nonsense, above. Can you point out where he is incorrect in his analysis? Or where this article is wrong
It seems to me it is the pro-nuclear lobby that has the money and power to manipulate public opinion and policy in this area, not the "eco-fascists", whoever they are.----Krebiozen
116 Krebiozen if you haven't seen the "vast amount of evidence" you haven't looked at the link I put in my first post. http://a-place-to-stand.blogspot.com/2010/03/low-level-radiation-evidence-that-it-is.html ...
Your defence to the elephant example is to say that there is a mechanism whereby the body can fight radiation in the same way that there is a mechanism whereby the body can fight low doses of poison or infection. This is the medical explanation for the hormetic effect in everything else, or as traditionally stated "the dose makes the poison". Thus your "defence" of LNT is to acknowledge it is likely to be entirely wrong.
In any case your claim that "Orac has demonstrated that Coulter's claims are nonsense" is clearly totally untrue. The very worst that anybody could honestly say is that Coulter's position can be described, if you ignore the proof, as having no more proof than the LNT theory, which has no positive proof (ignoring the vast amount to the contrary). The more honest alarmists here have acknowleged that there is no actual proof for LNT but defended it on the "Precautionary Principle", which is not the same as scientific evidence. Orac, of course, never reaches or even aspires to the heights of "more honest".
If the balance of lobbying power were, as you state, then with the Fukishima earthquake/tsunami having caused 25,000 deaths and the reactor damage zero the balance of media coverage would be 25,000 hours of TV time on the real tragedy and zero, or less, on the reactors. --- Neil
117 Neil, I have looked at most of the links and studies you refer to on your (horribly laid out) blog many times. This has been a subject I have studied over the past 30 years since I first worked with radioactive materials. I first came across your blog a couple of years ago, but I have learned nothing new from it. ---Kreboizen
(some stuff omitted here - there was a dispute about what was on my blog and some loss of tempers-Kreboizen repeats the relevant stuff later)
128 Kreboizen I have no intention of giving up ....I have actively been looking for somebody willing to debate the LNT/hormesis cases without dropping the subject and changing to ad homs and, unless you object, expect to put up a summary of any sensible discussion on my own blog. On those grounds I would like to acknowledge that you have not been involved in ad homs - that was going on long before you got here.
On the particular points you raise I think you are wrong to say that Professor Cohen's work and that of Professor Chen (Taiwan) are "known to be wrong". They have both been disputed. It would be astonishing if they hadn't since they go against the official paradigm. But that is not the same as being disproven. Professor Cohen has, in turn, vigorously criticised the criticism. I do not know if Chen has done the same but have seen no evidence that he has acknowledged being wrong.
I don't know if you are right about Coulter exaggerating mammogram evidence but it is a minor point and certainly does not justify Orac's "versus science" allegation. If we required that popularisations of science were always 100% accurate I doubt that any of them would pass muster.
On the paper you cite http://www.pnas.org/content/100/24/13761.full - I have read it (well the abstract) and it does not disprove, indeed barely touches on hormesis. It says there is evidence to support LNT down to 50-100 mSv (a remarkably unspecific amount for science), for non-instant exposures, but nothing below this, allegedly because of the difficulty of finding a large enough statistical population to be affected by lower levels). This conflicts with evidence from areas, such as south India where there is a background radiation of up to 200 mSv with no visible damage. It is also not entirely compatible with the radium paint experience where, as Professor Wade Allison has pointed out, there appears to be a cut off point at 10 gray (100,000 mSv) for a whole life exposure, causing no damage. Nonetheless it is irrelevant for any case of a hormetic effect under 50 mSv - 3 times the official danger level and one most hormesis supporters are willing to accept as a first approximation.
In fact the paper is clearly wrong about it being impossible to find larger populations exposed to lower levels. The entire world is exposed to levels of natural radiation, varying in easily measurable ways by region and the much higher exposure of people in Colorado than Mississippi is undisputable. This is the basis of Professor Cohen's work and that of the Swedish oncologist mentioned. Why the paper should make such an untrue assertion we can only speculate on.
I look forward, Kreboizen, to your assessment of the various links to evidence I have provided. I realise it may take some time since the evidence for hormesis is so extensive.-----Neil
130 Neil, here's what I found when I looked at the first 23 links on your blog. I hope it's clear which are my comments and which is the material linked to. I'm sorry I repeat myself in places. I have found some interesting bits of information that I think have been misinterpreted to mean hormesis, which I will write about separately.
1. http://www.alamut.com/proj/98/nuclearGarden/bookTexts/Rad_hormesis.html
An article dated 1988 "scavenged from the net" that proposes a conspiracy theory among health physicists and seems to be based on the work of Marshall Brucer who was employed by the United States Atomic Energy Commission. Has 4 links, 3 of which go nowhere, and one links to the article written by Javad Mortazavi mentioned below. There are no useful references and some very dubious claims.
2. http://www.angelfire.com/mo/radioadaptive/inthorm.html
An article written by an Iranian scientist, S. M. Javad Mortazavi arguing that "the existence of radiation hormesis and adaptive response are not deniable".
Experiments with mice found that if they were exposed to 2 Gy 60Co gamma-rays 46% of them developed thymic lymphoma, but if they were repeatedly given doses of radiation, lower rates of cancer were observed (17%). What were the cancer rates in mice that were not irradiated at all
Another study found that low dose pre-irradiation of mice before a mid-lethal dose improved survival (from 486 to 578 days), but mice not irradiated at all lived much longer (727 days).
http://www.wmsym.org/archives/2001/2/2-2.pdf
The rest of the article talks of atom bomb survivors, background radiation studies and nuclear power workers. I have mentioned all these areas before, noting that there is no agreement about what they prove or don't prove. Javad Mortazavi does not appear to have published anything in peer-reviewed journals - nothing on Pubmed I can find anyway.
3. http://www.jpands.org/vol9no1/chen.pdf
A 2004 article about the Taiwan apartment contamination with cobalt 60.
The article states that, "the age distribution of the exposed population has not yet been determined, and it was assumed that the age distribution of the exposed population is the same as that of the general Taiwan population" which was an erroneous assumption. In a more recent study, "cancer risks were compared with those populations with the same temporal and geographic characteristics in Taiwan by standardized incidence ratios (SIR), adjusted for age and gender." and concluded, "all solid cancers combined were shown to exhibit significant exposure-dependent increased risks" in those exposed before the age of 30.
http://informahealthcare.com/doi/abs/10.1080/09553000601085980
4. http://radiationhormesis.vpinf.com/index.html
Vinny Pinto's website. Pinto is a mystic and healer with some very peculiar beliefs. Interesting, but not what I would call a reliable source. His site links to a site selling "healing" radioactive stones. http://www.vinnypinto.us/
5. http://www.lewrockwell.com/miller/miller12.html
An article by a Dr Donald W. Miller who trots out the same old "evidence" as other sites. Miller has some unusual ideas, judging by his website: http://www.donaldmiller.com/
6. http://enochthered.wordpress.com/category/radiation-hormesis/
A blog post about radon and lung cancer. An interesting blog generally, worth a read. More recent larger studies show that radon undoubtedly is a major cause of lung cancer. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2853156
7. Dead link. Is supposed to link to an article by Prof. John Cameron, who was a proponent of radiation hormesis, that discusses how British radiologists live longer than other doctors, but doesn't. The longevity of British radiologists disappears when they are compared to other medical specialists. "We conclude that the low mortality of British radiologists who were registered in the period 1955–1997, in comparison with that for all medical practitioners, is attributable to the factors that cause a relatively low mortality in doctors in all medical specialties. There is no reason to attribute it to a specific benefit from exposure to low doses of ionizing radiation." http://bjr.birjournals.org/cgi/content/full/78/935/1057
An American study concluded:
"Radiologists had an excess in all-cause mortality rates compared to the other specialists for all cohorts who entered the Radiological Society of North America before 1940; the excess remained even when the cancer deaths were removed from the rates. These data are consistent with the concept of accelerated aging due to radiation. The cancer mortality rates for radiologists were higher than those of other specialists for an additional decade through 1949. The 1950-1959 cohort had not aged sufficiently to demonstrate the expected peak cancer mortality in the 60-64 year age group".
http://aje.oxfordjournals.org/content/101/3/188.full.pdf+html .............
9. http://www.world-nuclear.org/sym/1998/cohen.htm
An interesting article by Bernard Cohen, but somewhat undermined by more recent and better data on radon and lung cancer.
10. http://www.alamut.com/proj/98/nuclearGarden/bookTexts/Rad_hormesis.html
The same as the first link above. The claim that cows were euthanized to cover up the positive effects of radiation because they refused to die from radiation poisoning is hilarious (sorry Neil). There is no primary source for the existence of these cows, the dose they got, if or when they were euthanized. I have spent a long time searching but failed. Neil still manages to squeeze a conspiracy theory out of this. Even if a few cows did survive, we don't know how many other cows succumbed to radiation poisoning or cancer.
http://a-place-to-stand.blogspot.com/2010/03/radiation-hormesis-they-worlds-oldest.html
11. http://www.angelfire.com/mo/radioadaptive/
The same S. M. Javad Mortazavi website linked to above. He seems to be affiliated with the nuclear industry through the Iranian Nuclear Regulatory Authority and the IAEA.
12. http://www.docstoc.com/docs/24368147/Introduction-to-Low-Level-Radiation-Effects-for-15PBNC
A document that requires a paid membership to docstoc.com to access it, and that I cannot find elsewhere.
13. http://www.ncbi.nlm.nih.gov/pubmed/3570800?dopt=Abstract
Cohen's 1987 paper on radon and lung cancer, refuted by more recent, better designed and much larger studies. For example: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2853156/?tool=pubmed
14. http://pinnacle.allenpress.com/doi/abs/10.1667/RR1199.1
A study on HeLa cells that found a small dose of radiation (.4-4 mGy/day) given before a larger dose (3-Gy) reduced neoplastic changes in the cells induced by the larger dose. Claiming this adaptive response as evidence of hormesis seems ridiculous to me.
15. http://interactive.snm.org/docs/SNM_ANMC_Comment_Letter_to_NRC_Feb_2010.pdf
A letter from the American College of Nuclear Medicine (which promotes the use of nuclear medicine) and the Society of Nuclear Medicine to the U.S. Nuclear Regulatory Commission objecting to proposals to lower the annual limit of radiation exposure for workers from 50 mSv to 20 mSv. The ICRP (which is an independent non-governmental organization) explains the reasons for the proposed changes here: http://www.nrc.gov/about-nrc/regulatory/rulemaking/potential-rulemaking/opt-revise/icrp-pub-103-free-extract.pdf
16. http://www.arps.org.au/?q=content/sa-branch-seminar-march-2010
An advert for a seminar titled 'Low Dose Radiation Effects: A Biological Reality Check'. I found a transcript of what I think is the whole talk here: http://www.wmsym.org/archives/2001/2/2-2.pdf
Cell culture studies seem to show hormesis, but studies on mice found that mice exposed to 1.0 Gy dose lived 486 days, but of they were exposed to 0.1 Gy 24 hours before the 1.0 Gy dose, they lived for 578 days. However, mice not exposed to radiation at all lived for 727 days. If I was a mouse, I would stick with getting no radiation at all.
17. http://gulfnews.com/life-style/health/radiation-exposure-benefits-of-a-risk-1.590944
A newspaper article about a particle physicist who thinks that low dose radiation does no harm, but also talks to three other scientists, Professor Gillies McKenna of Oxford University, Cancer Research UK's expert on radiation oncology, Richard Wakeford, an epidemiologist specializing in the health effects of radiation at the University of Manchester who disagree with him, and think the LNT is the best approach.
18. http://www-formal.stan/
ford.edu/jmc/progress/linear.html
A short piece on the LNT by Professor John McCarthy of Stanford that claims there no direct evidence for the LNT and a lot of evidence against it. It is at least 10 years old (page last modified in 2000), and is out of date - most of the links on the page are dead. The evidence against the LNT mentioned is:
Hiroshima and Nagasaki survivors - others interpret the data differently, pointing out that those who survived the initial radiation may be more resistant to disease, and not be a representative population. Gofman has pointed out several changes in the data sets made retrospectively which is problematic with a prospective study.
Natural background radiation and high radon in some areas does not lead to increased cancer, it claims. More recent studies suggest this is incorrect (sorry to keep repeating myself).
http://iopscience.iop.org/0952-4746/29/2A/S03/pdf/0952-4746_29_2A_S03.pdf
19. http://www.environmental-expert.com/books/radiation-hormesis-and-the-linear-no-threshold-assumption-30922
A link to a book 'Radiation Hormesis and the Linear-No-Threshold Assumption' by Charles L. Sanders which costs over $200. "The author shows how proponents of the LNT assumption consistently reject, manipulate, and deliberately ignore an overwhelming abundance of published data and falsely claim that no reliable data are available at doses of less than 100 mSv" Most of the abundant data I have seen doesn't seem to support this, and I have no inclination to cough up $200 for this book.
20. http://ehp.niehs.nih.gov/members/1998/Suppl-1/363-368pollycove/full.html
A 13 year old article by Myron Pollygrove who worked for the U.S. Nuclear Regulatory Commission. Based on a 1996 presentation at a BELLE conference. BELLE is a government and industry based group formed to promote the safety of low level radiation
21. http://en.wikipedia.org/wiki/Ramsar,_Mazandaran#Radioactivity
A Wikipedia article about Ramsar which has a very high background radiation in some areas. Only about 1000 people live in the high background radiation areas which is not enough to estimate whether cancer risk is increased. Mean annual dose in Ramsar is 6 mSv which would only lead to an expected 0.06% increase in cancer, or less than 1 additional cancer in 1000 people. In fact small increases in cancer have been observed in Ramsar.
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/CancerRisk.html
http://iopscience.iop.org/0952-4746/29/2A/S03/pdf/0952-4746_29_2A_S03.pdf
http://tinyurl.com/6c45qar
22. http://www.numberwatch.co.uk/vocabulary.htm
A humorous redefinition of some words.
23. http://www.ecolo.org/documents/documents_in_english/taiwan-cobalt-60-apartmt-04.htm
A letter written to New Scientist magazine by Neil Craig. It is about the Taiwan cobalt 60 incident, again. I have explained above why this is wrong. Neil concludes, "there can no longer be any intellectual doubt whatsoever. Radioactivity in low doses is good for us". I'm sure he has changed his mind based on the better information now available i.e. "all solid cancers combined were shown to exhibit significant exposure-dependent increased risks". http://informahealthcare.com/doi/abs/10.1080/09553000601085980 ----Kreboizen
132 An extensive piece of work Kreboizen. Lets go through it.
1 - intended to be an overview and that is what it is.
2 - That he is Iranian may be less important, in scientific terms, than the extensive evidence given. The link you introduce shows that even at 2 Gy (200,000 mSv) living organisms can be acclimatised to radiation. It is irrelevant to whether there is a hormesis effect at under 50 mSv
3 - Your article disputing the Taiwan results looks rather like a data dredge. The quote you ge extended says "all solid cancers combined were shown to exhibit significant exposure-dependent increased risks in individuals with the initial exposure before the age of 30, but not beyond this age". Not only is this confirming no LNT effect above 30 but if you divide a population into a large number of small groups (e.g. those under 30 in an initial population of 10,000) you are statistically certain to get more than one showing an above average effect. As I have said I would like to see Professor Chen's response to this or the results being verified by somebody without a preconceived view.
4 - Indeed. Such stuff is anecdotal and I would never rely on it alone. On the other hand the fact that, for several thousand years, people have been "taking the waters", usually fairly radioactive waters from springs deep underground, is as strong as anecdotal gets.
5 - Orac won't like his ideas. I do. He is certainly well qualified to have medical opinions.
6 - I agree that the evidence given is "interesting". Your link "disproving" hormesis doesn't actually produce any research of its own it merely refers to other published claims. A major problem with meta studies is that the studies aggregated are selected both by the new author and by the original ones - scientific studies which produce "anomalous" results are more likely to be done again than published.
7 - I will correct that link thanks. Your counter links disputing this effect is normal scientific discussion. I note that the British dispute is based on saying that all British doctors are more than averagely healthy while the American one says that most American ones are below average.
8 - If I can't find it I will delete.
9 - As I said Cohen has vigorously disputed his disputants. I think the evidence is clear.
10 - I don't know what you mean about there being no primary source. My post you give links to both that the cattle were irradiated by the trinity A-Bomb test in 1946 and that they were put to sleep in 1964. That means that statistically some of them must have reached or exceeded the maximum age of cattle, 22 years. Killing this evidence was clearly a scientific crime.
11 - As above.
12 - No comment needed
13 - The alleged refutation is the same link discussed in #6.
14 - 3 Gy is as previously discussed, far higher than hormesis is claimed at. What this does do, however, is disprove that there is a consistent Linear No Threshold effect even at such high levels.
15 - No comment needed.
16 - As you acknowledge "Cell culture studies seem to show hormesis". If I were a mouse I would not want a Gy scale exposure either.
17 - Of course the newspaper will cover itself by asking for a soundbite of the official view. How is this unexpected or more important than what the article is about.
18 - If 10 years ago is to long to listen to Professor McCarthy (I don't think it is) then LNT, as a 60 year old theory adopted without evidence at the time is surely further away. Your link does not mention "hormesis" and is simply about the difficulties of research. "Nevertheless, the risk of exposure to radon
indoors in the domestic environment has long been questioned. About 20 ecological studies
have been performed since the 1980s, but due to methodological limitations these studies
proved unable to answer the question." (by which they mean they keep coming up with the wrong answer) is typical of the "there is no evidence so trust us" line of thought.
19 - So no further comment required.
20 - So " " " "
21 - Your first link says "In some houses in Ramsar, Iran, the inhabitants are exposed to an annual dose of background radiation of as much as 130 mSv per year — over 70 times that in Colorado. Nevertheless, the inhabitants of Ramsar are just as healthy as — or even healthier than — control populations exposed to far lower levels of radiation." The 2nd has already been dealt with in 18. The 3rd link isn't working.
22 - No further comment.
23 - Your link has already been dealt with in #4
What seems undeniably clear is that there is no actual evidence for the LNT theory and indeed that its supporters rely on it being allegedly impossible to prove it at the low end, because of the large size of population needed. You will be aware that a key requirement of any scientific theory is that it be "falsifiable" i.e. proven wrong. Personally I think most unfalsifiable theories (LNT, catastrophic warming, withcraft, creationism, flat earth are indeed falsifiable it just thaty their supporters are to stubborn to look). However, if the LNT supporters are correct then LNT cannot be counted as science
I would welcome any suggestion of what would provide falsifiability for LNT.
Hormesis supporters do not claim unfalsifiability and point to the natural background radiation, which can be determined and show Colorado not to have a higher cancer rate than Mississippi. The experimental statistical evidence for it in plants & cultures seems undisputed.----Neil
133 I want to answer an earlier comment from Neil. To be honest, I have read so much about radiation exposure over the past few days it's starting to drive me crazy. I'll post a summary of what I think I have learned about this in the next day or two, as it may be of use to someone.
I think you are wrong to say that Professor Cohen's work and that of Professor Chen (Taiwan) are "known to be wrong". They have both been disputed. It would be astonishing if they hadn't since they go against the official paradigm. But that is not the same as being disproven. Professor Cohen has, in turn, vigorously criticised the criticism. I do not know if Chen has done the same but have seen no evidence that he has acknowledged being wrong.
Well I think Professor Cohen has fallen foul of the ecological fallacy, averaging cancer rates and radon exposure in US counties and expecting to find a meaningful result. This is not how epidemiology should be done and the negative correlation he found between radon exposure and cigarette smoking both demonstrates this and explains his findings.
As for Chen, I don't see how you can continue to defend a study of cancer rates that failed to take age demographics into account, when a study that used matched controls is available.
I don't know if you are right about Coulter exaggerating mammogram evidence but it is a minor point and certainly does not justify Orac's "versus science" allegation. If we required that popularisations of science were always 100% accurate I doubt that any of them would pass muster.
It wasn't mammogram evidence, it was high dose chest x-rays of patients with TB that did not cause as much cancer as you would expect from such high doses. The original paper concluded, "the risk of breast cancer associated with radiation decreases sharply with increasing age at exposure and that even a small benefit to women of screening mammography would outweigh any possible risk of radiation-induced breast cancer." In other words if you dose older women with x-rays, the increased risk of cancer is outweighed by the benefits of early detection of breast cancer. The article by Kolata that Coulter gives as a source of the information says, "the tuberculosis patients, some analyses said, had fewer cases of breast cancer than would be expected." Coulter misinterprets this, writing, "tuberculosis patients subjected to multiple chest X-rays had much lower rates of breast cancer than the general population". This is not a minor point. Coulter has not bothered to track down the original source and has written something that is opposite to the truth. At a minimum this is sloppy and irresponsible journalism.
On the paper you cite http://www.pnas.org/content/100/24/13761.full - I have read it (well the abstract) and it does not disprove, indeed barely touches on hormesis. It says there is evidence to support LNT down to 50-100 mSv (a remarkably unspecific amount for science), for non-instant exposures, but nothing below this, allegedly because of the difficulty of finding a large enough statistical population to be affected by lower levels).
The article is not about hormesis, I never said it was. It is about why the LNT is accepted as the safest assumption to make about low level exposure.
This conflicts with evidence from areas, such as south India where there is a background radiation of up to 200 mSv with no visible damage.
How do you know how much damage there is there? What control population do you use to establish this? Where is the matched control study of this exposed population? The one case control study I could find found that lung cancer was 2.3 times more common where the external dose was greater than 10 mGy per year, though this was not statistically significant. The study, which I can't find on-line, is this: Binu VS, Gangadharan P, Jayalekshmi P, Nair RRK, Nair MK, Rajan B and Akiba S 2005 The risk of lung cancer in HBR area in India—a case–control study High Levels of Natural Radiation and Radon Areas: Radiation Dose and Health Effects ed T Sugahara and Y Sasaki. It is cited in this study.
It is also not entirely compatible with the radium paint experience where, as Professor Wade Allison has pointed out, there appears to be a cut off point at 10 gray (100,000 mSv) for a whole life exposure, causing no damage. Nonetheless it is irrelevant for any case of a hormetic effect under 50 mSv - 3 times the official danger level and one most hormesis supporters are willing to accept as a first approximation.
Even assuming this is correct, and the data collected several decades ago is reliable, exposure to radium may not be typical of other exposures to radiation. The number of exposed workers examined (less than 3000) may be too small to find a statistically significant effect consistent with the LNT against a background of normal cancer rates. The cut-off below which there is no measurable effect is between 4 and 11 microcuries radium according to this paper. I'm not sure how that translates into mSv. By the way, I can't find any information about "the 30 year followup of 1155 low dose radium dial painters who had fewer cancers than the general population and lived longer".
If you look at the Hiroshima and Nagasaki survivors, >50% of them had a dose of less than 50 mSv. Even those with a dose of 34 mSv showed a statistically significant increase in cancer risk.
http://www.pnas.org/content/100/24/13761/F2.expansion.html
In fact the paper is clearly wrong about it being impossible to find larger populations exposed to lower levels. The entire world is exposed to levels of natural radiation, varying in easily measurable ways by region and the much higher exposure of people in Colorado than Mississippi is undisputable. This is the basis of Professor Cohen's work and that of the Swedish oncologist mentioned. Why the paper should make such an untrue assertion we can only speculate on.
The problem with that approach is that there are confounding factors. There may be many reasons why cancer rates in Colorado and Mississippi are different. You have to take age, smoking and socioeconomic status into account for a start. You need a control group matched for all those factors. That's where it gets messy, and small changes in corrections for age, or other factors can have major effects on the results.
I still maintain that the evidence for hormesis or a threshold dose of radiation in humans is far from overwhelming. ------ Kreboizen
134 The difficulty of assessing statistics, "ecological fallacy" or otherwise cuts both ways and is inherently as likely to lead to an underestimate of hormesis. For example your 2nd link says:
"Population density is strongly positively associated with lung cancer. It follows that aggregate residential radon and lung cancer rates should be negatively associated for reasons having nothing to do with the possibility of radon being carcinogenic to the lung."
It is not inherently likely that population density would cause lung cancer. A more likely reason would be that areas where high populations develop tend to be flat fertile soil rather than mountains but mountains contain more radioactive rock. This does not seem to have been noticed.
As your paper accepts there is no real evidence for LNT below 50 mSv it is simply an assumption.
On the evidence for south India that is why I said there is "no VISIBLE damage". Since 200 mSv is 10 or more times above "official" danger levels if that is justified one would expect some noticeable effect.
Exposure to radium being seriously different from all other sorts of radiation is an assumption without evidence. Moreover if it were the case there would be a 50:50 chance that it underestimated the hormetic effect rather than overestimated it. A lot of countering of hormesis seems to rely on the possibility of there being unknown confounding factors which (A) becomes increasingly statistically less credible the more times it is invoked and (B) is not evidence for the counter theory, but for more research.
I would welcome more research on the subject & I think we would agree on that. Scientific questions can be opened by debate but are closed by enough good research. More good research would find if there are enough confounding factors or not. It would either raise the level of evidence for hormesis to "overwhelming" or reduce it.
I believe that the acceptance of LNT, on grounds of bureaucratic convenience, the general failure to do the research and particular instances such as killing the exposed cattle when they embarrassed the LNT theory indicates that the science has been driven by political conclusions rather than the other way round.---- Neil
135 As promised, here's a summary of what I think I have learned about low dose radiation, hormesis and the linear no threshold theory. I'm no expert, but the links supporting my conclusions are above. Any new links I have included below.
Evidence for and against hormesis and the LNT
Theoretical evidence
There are arguments for both that seem equally persuasive to me. It seems self-evident that DNA repair mechanisms cannot be 100% effective as otherwise radiation even in high doses would not cause cancer, but it does (Gofman). However, if protective mechanisms induced by radiation repair more damage from other sources than is caused by the radiation, then hormesis may occur (Pollycove and Feinendegen).
Experimental evidence
Plants, trees algae etc
Some evidence show that low level radiation stimulates the growth of plants, fungi, algae, protozoans, insects, and nonmammalian vertebrates. It is not clear if that is true at all levels of exposure, all types of exposure and with all isotopes. Anyway, this does not mean that the same is true for humans.
Cell cultures - human and animal
Some studies show a protective effect of a small dose of radiation before a larger one is given, the radioadaptive response. Some studies show that cells have fewer cancerous changes with low doses of radiation than those with no radiation. Other studies find that even small doses of radiation cause damage in line with the LNT. Low-dose hypersensitivity has also been demonstrated.
As Dr. Luckey states:
"Except for cytology and cells in culture, artificial systems which lack participation from whole body faculties (particularly the immune system), there is no reasonable or scientific proof of LNT at low doses of ionizing radiation." http://www.radpro.com/641luckey.pdf
In other words Luckey is saying that there is reasonable scientific proof of the LNT at low doses of ionizing radiation in cytology and cells in culture. As he says, whether this translates to humans is not known.
So the evidence in cell culture is equivocal. The important thing is whether it translates into real effects in humans.
Animal studies
Some animal studies show short term health benefits from low dose radiation, especially in infected animals, but later a higher risk of cancer. Radioadaptive responses occur in mice, but mice not dosed with radiation at all live longer. Very low dose studies require too many animals to get statistically significant results. Data are equivocal.
Luckey http://www.radpro.com/641luckey.pdfgives several examples of radiation hormesis in animals, but these are all animals with diptheria, vesicular stomatitis virus or other infections.
To quote Luckey: "This graph exposes the misinterpretation to conclude that control mice have longer average life-spans than the exposed mice when the median value was used instead of mean or average. The disbelief spread when major laboratories were misled by repeating the Lorenz protocols with specific pathogen-free (SPF) animals. Since SPF animals have no pathogens to cause infection, controls lived as long as irradiated mice and no hormesis was found."
In these sorts of experiments the median (middle value of values arranged in order) is often used as it is not distorted by an abnormal distribution, In a normal distribution (bell-shaped curve) the median and the mean are the same. If the mean and the median are very different, there is not a normal distribution. Median survival is a very fair way of expressing results, as half the animals lived for fewer days, and half lived for more days.
Notice that Luckey states that in normal uninfected mice, "controls lived as long as irradiated mice and no hormesis was found". This is what the LNT would predict, as you would have to irradiate many thousands of mice to see the small increase in mortality predicted after such a small dose (1.1mGy/d or 40 rad per year about 100 times average background).
However, another experiment does show a significant increase in lifespan in mice exposed to 7 or 14 cGy/year (7-14 rad) which is around 20 times background radiation. This is the only experiment I can find that shows an increase in animal lifespan with low dose radiation.
http://www.blogger.com/goog_804070127
Which of these studies is right? Can they both be right? Maybe 20 times background is beneficial, but 100 times background is not. Anyway, humans are not mice, and we cannot extrapolate directly from mice to humans.
Another study using mice that are hypersensitive to whole body x-rays found a very low dose (1 micro Gy or 0.0001 Rad or 0.1 mRad) that caused damage, a higher dose that was hormetic, and a higher dose than that which caused damage. This may explain some of the conflicting evidence. By the way, some humans are also hypersensitive to radiation.
http://www.jstor.org/pss/3581207
High background radiation studies
These are plagued by confounding factors, limited populations and difficulties matching exposed and control populations. The data are equivocal apart from radon, which recent studies strongly suggest is a major cause of lung cancer in line with LNT predictions. Combined figures from the whole of Europe, the USA and China give a large population which generates considerable statistical power.
Occupational exposure to low dose radiation
These studies are plagued by confounding factors, limited populations and difficulties matching exposed and control populations. The data are equivocal.
Atomic bomb survivors
Except for higher dose studies, these are plagued by confounding factors, limited populations and difficulties matching exposed and control populations. The data are equivocal, though statistically significant increased risk of cancer has been found at levels as low as 34 mSv.
There are eminent scientists who are convinced that radiation is good for us. There are equally eminent scientists who believe that radiation in low doses is harmless. There are equally eminent scientists who believe we have the safety regulations about right (the majority, apparently). There are equally eminent scientists who believe that low dose radiation is far more dangerous than we currently think. This disagreement suggests that the data are equivocal, and that there is a considerable degree of uncertainty.
I tend to agree with the National Academy of Science study which suggests that in the face of such uncertainty we should be cautious. Though we know that low levels of radiation must have a very small (if any) positive or negative effect on individuals, when large populations are exposed large numbers of people may be affected. The costs of maintaining current safety regulations must be balanced against the possibility of thousands of excess cancers if they are relaxed.
There are scientists who think that hardly anyone has died as a result of Chernobyl, and those who believe that hundreds of thousands have died.
A word on epidemiological studies
There are populations that have been exposed to relatively large doses of radiation. For example the survivors of Hiroshima and Nagasaki. Following these survivors should give us a good idea of the long term effects of radiation, you might think. For large doses it does, and this is part of the data used to construct the LNT curve. However, there are potential problems with the data. Firstly, these are survivors. It is not unreasonable to suggest that more of those vulnerable to radiation would have died shortly after the bombs were dropped. The survivor population may or may not be comparable to the control population. Which brings me to the next problem - what control population do you use? The Japanese population not within range of the atom bombs is usually used, but is this a fair control group? Was the population of Japan exposed to radioactive fallout? Are we comparing one exposed population to another? I don't know the answer to that question. Sternglass claims that leukemia rates in Japan increased by a factor of 5 after 1945, but I can't find the primary data, and Sternglass is not considered a reliable source by many.
Parts of Ramsar in Iran have very high background radiation (55-200 times average background), and 10,000 people live in the high radiation area so it should be simple to determine if there is an increased cancer (or other disease) rate in this area. In practice it doesn't seem so straightforward. If you go to http://www.sciencedirect.com/ and type "Ramsar" into the search box, you will get several studies, some of which find lower cancer rates, some that find no effect and one that finds an increased rate. Who do you believe?------ Krebiozen
136 OK I am glad you accept the experimental evidence of hormesis in plants, cultures and animals. Once it is accepted an effect exists the rest is measurement of degree and where, if anywhere, the effect stops both in radiation level and complexity of the organism (I realise how much of a simplification that is). If it is found in one in one part of the living world the default assumption is that we would expect it elsewhere, unless there is evidence to the contrary.
My reading of Luckey is not yours. I suggest that what that phrase means is that he had not searched for hormesis in cells which "lack participation from whole body faculties" ie lack an immune system, because it an immune system is essential for the hormesis theory rather than that he had investigated and found it missing. If he, or anybody else, had investigated I submit it would have been published properly not as an arguable implication in a throw away line.
I think it reasonable to believe 20 times (app 40 mSv) background is hormetic but 100 times (app 200 mSv) not. That latter figure is about 50% above the Ramsar background. Both are above official danger levels from which we are assured government regulation is "protecting" us.
You are exaggerating in describing the possibility of "thousands" of extra cancers if regulations are relaxed. Nobody is suggesting a relaxation that would allow nuclear plants to normally emit even 1/10th as much as coal plants currently do (50 times more than nuclear ones http://a-place-to-stand.blogspot.com/2009/05/menace-of-radioactivity-released-by.html) , let alone TMI or Fukushima, both of which have killed nobody. So, even were LNT true, a relaxation would be unlikely to kill as many as a handful (in fact if it replaced coal plants it would, assuming the LNT theory, be directly beneficial). Of course if it provides heat for people through the winter it would save millions worldwide.
I cannot agree with your assertion that radon has unequivocally been proven harmful. There have been many studies on this precisely because they kept coming up with the "wrong" answers. It is unsurprising that somebody has managed to come up with the "right" answer but Cohen's, which found a hormetic effect half of the damaging effect of smoking seems to have been professionally conducted. This is another on radon http://enochthered.wordpress.com/category/radiation-hormesis/ "described by their own authors as “surprising” and “stunning”: Clear evidence of radiation hormesis"
On your surprise that some studies show hormesis and some are consistent with LNT may I suggest this answer from Richard Feynman's speech on cargo cult science.
"Millikan measured the charge on an electron by an experiment with falling oil drops, and got an answer which we now know not to be quite right. It's a little bit off, because he had the incorrect value for the
viscosity of air. It's interesting to look at the history of measurements of the charge of the electron, after Millikan. If you plot them as a function of time, you find that one is a little bigger than Millikan's, and the next one's a little bit bigger than that, and the next one's a little bit bigger than that, until finally they settle down to a number which is higher.
Why didn't they discover that the new number was higher right away? It's a thing that scientists are ashamed of--this history--because it's apparent that people did things like this: When they got a number that was too high above Millikan's, they thought something must be wrong--and they would look for and find a reason why
something might be wrong. When they got a number closer to Millikan's value they didn't look so hard. And so they eliminated the numbers that were too far off, and did other things like that."
http://www.lhup.edu/~DSIMANEK/cargocul.htm
The entire speech should be read by anybody interested in scientific integrity.
In this case LNT is, like Millikan's case but very very much stronger because it is so heavily politically backed, the official theory which any experiment must conform to. It is to their considerable credit that such a significant number of scientists have found - and published - the evidence for the non-official theory. --- Neil
Labels: hobgoblins, Hormesis, nuclear
