Sometimes when a pundit or politician makes claims that are either contrary to or distort science for ideological or political advantage, I feel the need to discuss those claims, sometimes even sarcastically. Such was the case last week, when Ann Coulter wrote a blisteringly ignorant column, entitled A Glowing Report on Radiation. She wrote this article in the wake of the fears arising in Japan and around the world of nuclear catastrophe due to the damage to the Fukushima nuclear power plant caused by the earthquake and tsunami that hit northern Japan on March 11. Coulter was subsequently interviewed by Fox News pundit Bill Oa??Reilly on The Oa??Reilly Factor on Thursday evening:
Yes, according to Coulter, radiation is good for you, just like toxic sludge! Even more amazing, in this video Bill Oa??Reilly actually comes across as the voice of reason, at least in comparison to Ann Coulter. Hea??s very skeptical of Coultera??s claims and even challenges her by saying, a??So by your account we should all be heading towards the nuclear reactor.a??
So, fellow SBM aficionados, is Coulter right? Are all those scientists warning about the dangers of even low-level radiation all wrong? Should we start hanging out in radioactive mine shafts, as Coulter mentions in her column (seriously) in order to boost our health and decrease our risk of cancer?
Not so fast, there, Ann. Herea??s a hint: If Bill Oa??Reilly can lecture you on science and look more reasonable than you, youa??re off the rails.
Coulter, hormesis, and a??Dona??t worry, be happy!a??
Actually, the scientific assessment of what levels of exposure to ionizing radiation are dangerous is, as you might imagine, a wee bit more complicated than my little sarcastic rejoinder makes it, but youa??d never know that from Ann Coultera??s article and her interview with Bill Oa??Reilly. The reason for my sarcastic characterization of Coultera??s scientific nonsense is because her article uses many of the same tactics as any denialist. Chief among these is that Coulter takes the germ of a scientific controversy and then uses it to try to imply that the scientific consensus is fatally flawed. In this case, the scientific controversy is over how dangerous low level exposure to radiation is used to imply that the radiation from a nuclear disaster is not potentially harmful. All you former residents of Chernobyl, take note! Ita??s fine to move back to your homes that you were forced to abandon 25 years ago!
Here is what Coulter claims in her article:
With the terrible earthquake and resulting tsunami that have devastated Japan, the only good news is that anyone exposed to excess radiation from the nuclear power plants is now probably much less likely to get cancer.
This only seems counterintuitive because of media hysteria for the past 20 years trying to convince Americans that radiation at any dose is bad. There is, however, burgeoning evidence that excess radiation operates as a sort of cancer vaccine.
As The New York Times science section reported in 2001, an increasing number of scientists believe that at some level a?? much higher than the minimums set by the U.S. government a?? radiation is good for you. a??They theorize,a?? the Times said, that a??these doses protect against cancer by activating cellsa?? natural defense mechanisms.a??
What Coulter is referring to is the phenomenon of radiation hormesis. This is nothing more than a biphasic dose-response curve to radiation in which the curve initially goes down with increasing dose (less risk of disease with increasing radiation exposure) and then curves upward and at some point crosses a threshold where radiation exposure is no longer beneficial but harmful with further dose increases. Basically, ita??s a scientific model wherein low level exposure to radiation is not only not harmful but in fact beneficial. The reason for this effect, if it exists in humans, is hypothesized to be that low level radiation activates DNA damage repair and other protective mechanisms that are not activated in the absence of radiation; moreover, it is further hypothesized that these mechanisms are activated more than they need to be, so that low level radiation is actually protective against radiation-induced diseases such as cancer.
The radiation hormesis model is markedly different from the currently prevailing model that is used for regulatory purposes by most governments, the linear no-threshold (LNT) model, which states that there is no such thing as a a??safea?? dose of radiation and that radiation dammage accumulates in a linear fashion with dose. For completeness sake, I will note that there is also at least one other model for the biological effects of radiation, specifically a model in which there is a threshold dose under which radiation is not harmful. In practice, distinguishing between a threshold model and a hormesis model can be very difficult.
In order to give you an idea of what hormesis would look like in a radiation dose-response curve, I stole this graph from Wikipedia. Actually, I didna??t steal it; ita??s public domain because ita??s a product of a U.S. government agency. However, it illustrates the concept of hormesis quite well:
Curve A demonstrates supralinearity, in which toxic effects are actually more intense per unit of radiation at lower doses; there is no evidence that this is indeed the case. Curve B is linear, and Curve C is linear-quadratic, in which low doses of radiation are less harmful per unit of radiation than higher doses. Curve D represents hormesis, where low doses of radiation are actually protective up to a certain threshold, where the curve shifts from a protective effect to a harmful effect with increasing radiation. The main contenders for the model that best describes radiation effects are either curve B, C, or D.
The key aspect of Coultera??s article that makes it so irresponsible is what she leaves out. What she neglects to mention is that, even if hormesis is an accurate model for radiation effects in humans, it only applies for very low dose exposures. (More on how low in the next section.) True, Coulter does at one point concede that it is a??hardly a settled scientific fact that excess radiation is a health benefit,a?? throughout the rest of her article she presents the idea of hormesis as though it werea??you guessed it!a??a settled scientific fact. Indeed, Coultera??s earlier assertion that a??excess radiation acts as sort of a cancer vaccinea?? is the sheerest exaggeration, even if hormesis is an accurate model of radiation exposure. Aside from this major exaggeration, how do Coultera??s assertions, which appear to be based largely on studies cited in a single NYT article that is nearly a decade old, stack up against science?
Not very well. Surprise! Surprise! As is the case with many denialists, Coulter takes a germ of actual science and then twists and exaggerates it beyond all recognition in order to support a preconceived notion, namely that those pointy-headed (and, of course, liberal) environmentalists are hiding the evidence that radiation at low doses is good for you. To accomplish this, Coulter cherry picks studies, failing to put them into their proper context with existing research, all for the purpose of advancing her ideological viewpoint.
Radiation hormesis: Ann Coultera??s claims versus reality
Before I discuss what the data regarding radiation hormesis actually show, ita??s essential to discuss briefly why it is that the LNT model predominates when it comes to policy-making and setting limits on what is considered a??safea?? radiation exposure. The reason is not that biased scientists are a??hidinga?? the evidence that radiation is good for you. Rather, it boils down to a few reasons. The first is probably that an LNT model is the simplest, most conservative model that can be fit to currently existing evidence. The problem with the LNT model is the same as the problem with the hormesis model. While at higher radiation doses, effects due to radiation are, like effects due to pretty much any other high-level environmental exposure, much more robust and reproducible, at lower radiation doses, the effects are weaker, and the scatter in the data is much greater. In other words, at low doses the signal-to-noise ratio is much lower due to a lot more a??noisea?? and a lot less signal in the data. Moreover, the data are more difficult to collect, and variability from system to system, organism to organism, and cancer to cancer is likely to be much greater.
As imperfect as it is, the LNT model is a reasonable approximation for purposes of policy-making because it is conservative and safe. Admittedly, there are problems applying such a model when the doses get really low, as in lower than the normal background radiation that we all live in, but ita??s a useful approximation. When it is very hard to distinguish between an LNT model and a hormesis model at very low radiation exposures, until better data can be gathered that clearly demonstrate the superiority of one model over another, the responsible and safe model to choose is the most conservative one that fits reasonably well. Basing public policy on a model that, if incorrect, has the potential to result in considerable harm in the form of increased radiation-induced disease prevalence is not wise policy at all, at least when the alternate model is not demonstrably wrong.
As far as Coultera??s reliance on an old NYT article, I thought Ia??d take a look at the article itself. As an aside, I cana??t help but note that I really hate it when the online version of an article doesna??t include links to cited articles, and Coulter is no different in this regard. However, I do believe I managed to find this 2001 NYT article anyway from November 27, 2001, entitled For Radiation, How Much Is Too Much? Ita??s by Gina Kolata and discusses the controversy that had begun to bubble up about what doses of ionizing radiation might be considered safe. If you read it, youa??ll see that ita??s much more balanced than how it is portrayed by Coulter. For example, here is what Coulter writes about two studies cited by Kolata:
Among the studies mentioned by the Times was one in Canada finding that tuberculosis patients subjected to multiple chest X-rays had much lower rates of breast cancer than the general population.
Here is what Kolata actually wrote about these studies:
Now, some scientists even say low radiation doses may be beneficial. They theorize that these doses protect against cancer by activating cellsa?? natural defense mechanisms. As evidence, they cite studies, like one in Canada of tuberculosis patients who had multiple chest X-rays and one of nuclear workers in the United States. The tuberculosis patients, some analyses said, had fewer cases of breast cancer than would be expected and the nuclear workers had a lower mortality rate than would be expected.
Dr. Boice said these studies were flawed by statistical pitfalls, and when a committee of the National Council on Radiation Protection and Measurement evaluated this and other studies on beneficial effects, it was not convinced. The group, headed by Dr. Upton of New Jersey, wrote that the data a??do not excludea?? the hypothesis. But, it added, a??the prevailing evidence has generally been interpreted as insufficient to support this view.a??
Notice how the finding in a??some analysesa?? that there were fewer cases of breast cancer than might be expected has magically morphed into a??tuberculosis patients subjected to multiple chest X-rays had much lower rates of breast cancer than the general populationa?? in Coultera??s words. Also note that this appears to be the NCRPM report that analyzed the data. Unfortunately, it would have cost me $40 to download the PDF; so I didna??t. But what about these studies?
The first study to which Coulter refers appears to be a study from Canada that was reported in the New England Journal of Medicine in 1989. This study examined the mortality from breast cancer in a cohort of 31,710 women who had been treated for tuberculosis at Canadian sanatoriums between 1930 and 1952. A significant proportion (26.4%) of these women had received radiation doses to the breast of 10 cGy or more from repeated fluoroscopic examinations during therapeutic pneumothoraxes. It should be noted that these sorts of doses of radiation are far in excess of anything likely to be received using modern radiological equipment, in particular given that we no longer perform fluoroscopy and therapeutic pneumothorax to treat tuberculosis. Interestingly, this is how the abstract summarizes the results of this study:
Women exposed to a?￥ 10 cGy of radiation had a relative risk of death from breast cancer of 1.36, as compared with those exposed to less than 10 cGy (95 percent confidence interval, 1.11 to 1.67; P = 0.001). The data were most consistent with a linear dosea??response relation. The risk was greatest among women who had been exposed to radiation when they were between 10 and 14 years of age; they had a relative risk of 4.5 per gray, and an additive risk of 6.1 per 104 person-years per gray. With increasing age at first exposure, there was substantially less excess risk, and the radiation effect appeared to peak approximately 25 to 34 years after the first exposure. Our additive model for lifetime risk predicts that exposure to 1 cGy at the age of 40 increases the number of deaths from breast cancer by 42 per million women.
Oops! Maybe I found the wrong study! On the other hand, this is a Canadian study that looked at women with tuberculosis who received numerous chest X-rays (fluoroscopy, actually), and I cana??t find another one like it. I also couldna??t find other publications with other analyses. The analysis that exists in the published literature, for better or for worse, concludes that the risk of breast cancer is elevated with exposures to radiation greater than 10 cGy. So, what are these other a??analysesa?? that purport to claim that these patients actually had a lower risk of mortality from breast cancer? I smelled a rat.
My first hint came from an article published in the Journal of the Association of American Physicians and Surgeons (JPANDS) by Bernard Cohen entitled The Cancer Risk From Low Level Radiation: A Review of Recent Evidence. Ia??ve discussed JPANDS and how it plays fast and loose with science for ideological reasons before, in particular its antivaccine views and its publishing studies so bad that laughter is the only appropriate response. In his article, Cohen claims that hormesis a??found for breast cancer among Canadian women exposed over longer periods of time to X-ray fluoroscopic examinations for tuberculosis (13); when appropriately evaluated, this evidence shows a decrease in risk with increasing radiation dose at least up to 20 cSv (20 rem).a?? Unfortunately, no evaluation of this evidence is included; Cohen simply asserts that this is so.
Fortunately, it didna??t take long for me to find other JPANDS articles making the same argument. For example, this one by Joel M. Kauffman. In it, Kaufmann divides up the subjects into several radiation dose ranges, while rejecting data from Nova Scotia because a??too fewa?? low radiation points were included. Conveniently he fails to define what a??too fewa?? is. However, if one looks at Table I in the NEJM paper, ita??s obvious that in the dose range between 10 and 99 cSv, the death rate in Nova Scotia was much higher than the other provinces. One wonders if that had anything to do with leaving out the data, rather than writing the authors for a more detailed breakdown of the data between those dose levels, one does. In any case, what Kaufmann appears to have done is what JPANDS writers frequently do: Cherry pick the data. He took the lower end of the dose ranges, used a??eyeballa?? fitting instead of statistical fitting to models, and left out any hint of a statistical analysis. The authors of the NEJM article went to great lengths to demonstrate that a LNT model was the best fit to their data; Kaufmann expects you to a??eyeballa?? his graph and accept his claim of hormesis. Similarly, Jerry Cuttler and Myron Pollycove, in another JPANDS article, plotted the Canadian data on a semilog scale to make a hormesis effect look far more convincing than the actual data support, all the while simply claiming that a hormesis model fit the data better than an LNT model. Unfortunately, they didna??t a??show their work,a?? so to speak. No discussion of how they modeled the data is included. No wonder the NCRPM found these a??othera?? analyses unconvincing. Also, while ita??s not surprising that Coulter would have gotten her data on this from JPANDS, ita??s rather disappointing that Kolata didna??t look deeper back in 2001.
The second study cited by Kolata and exaggerated by Coulter was a study of U.S. nuclear industry workers. Regarding this sort of data, the scientists at the Lawrence Berkley National Laboratory have included on their website this analysis:
The results of individual studies have been inconclusive, and to investigate the matter further a combined analysis has been carried out of seven studiesa??three for sites in the United States (Hanford, Oak Ridge, and Rocky Flats), three for sites in the United Kingdom, and one for Canada. A total of 95,673 workers was included, of whom 60% received effective doses above 10 mSv (1 rem). In the entire population, there were 15,825 deaths, of which 3,976 were from cancer. The comprehensive results for all cancers taken together showed a very slight decrease in cancer rate with increasing dose. However, this result had no statistical significance. Of possible greater statistical significance is a slight increase with radiation dose for some types of leukemia. Overall, the statistical uncertainties were large enough that the analysis did not rule out linearity or any of the other alternative dose-response curves indicated in Figure 15-1a??although it does set an upper limit on the possible magnitude of a hypothesized supra-linearity effect.
The study being discussed it this one, which, by the way, concludes:
These estimates, which did not differ significantly across cohorts or between men and women, are the most comprehensive and precise direct estimates of cancer risk associated with low-dose protracted exposures obtained to date. Although they are lower than the linear estimates obtained from studies of atomic bomb survivors, they are compatible with a range of possibilities, from a reduction of risk at low doses, to risks twice those on which current radiation protection recommendations are based. Overall, the results of this study do not suggest that current radiation risk estimates for cancer at low levels of exposure are appreciably in error.
Coulter also makes much of a study of shipyard workers from 1991:
A $10 million Department of Energy study from 1991 examined 10 years of epidemiological research by the Johns Hopkins School of Public Health on 700,000 shipyard workers, some of whom had been exposed to 10 times more radiation than the others from their work on the shipsa?? nuclear reactors. The workers exposed to excess radiation had a 24 percent lower death rate and a 25 percent lower cancer mortality than the non-irradiated workers.
The reference for this is:
Matanoski, G. M. (1991) Health Effects of Low-Level radiation in Shipyard Workers, Final Report, DOE/EV/10095-T2, National Technical Information Service, Springfield, Virginia, USA.
Unfortunately, I couldna??t get a hold of this report online over the weekend. I did, however, find the more recent reanalysis of the data from 2008 by Matanoski et al published in the Journal of Radiation Research. What Matanoski found wa that most of the differences in mortality and cancer rates found between shipyard workers who serviced nuclear ships and shipyard workers who did not were not significant, although there did appear to be trends towards increased risk of leukemias and other cancers with increasing dose. Overall, as far as saying anything about the association between radiation exposure and cancer, at best this study could be described as inconclusive. Certainly ita??s exceedingly thin gruel to make such definitive statements about hormesis. As for the lower all-cause mortality among the nuclear workers, that is almost certainly due to phenomenon known as the a??healthy worker effecta??; i.e., the selective recruiting of healthier than average persons into the industry who have continued access to better than average health care.
Similarly thin gruel is this claim by Coulter:
In 1983, a series of apartment buildings in Taiwan were accidentally constructed with massive amounts of cobalt 60, a radioactive substance. After 16 years, the buildingsa?? 10,000 occupants developed only five cases of cancer. The cancer rate for the same age group in the general Taiwanese population over that time period predicted 170 cancers.
The people in those buildings had been exposed to radiation nearly five times the maximum a??safea?? level according to the U.S. government. But they ended up with a cancer rate 96 percent lower than the general population.
Not exactly. Actually, not at all. Ita??s not even thin gruel; ita??s misrepresentation, either intentional or through Coultera??s laziness in researching the article. Coulter, as usual, is exhibiting willful ignorance by citing old data. In fact, more recent analyses of the Taiwanese population that lived in these buildings do not support her claims at all. The most recent followup study I could find was published in 2006 in the International Journal of Radiation Biology by Hwang et al. The results were:
A total of 7271 people were registered as the exposed population, with 101,560 person-years at risk. The average excess cumulative exposure was approximately 47.8 mSv (range 5 1 a?? 2,363 mSv). A total of 141 exposed subjects with various cancers were observed, while 95 developed leukemia or solid cancers after more than 2 or 10 years initial residence in contaminated buildings respectively. The SIR were significantly higher for all leukemia except chronic lymphocytic leukemia (n1a??46, SIR1a??43.6, 95% confidence interval [CI] 1.2a??7.4) in men, and marginally significant for thyroid cancers (n1a??46, SIR 1a??4 2.6, 95% CI 1.0 a?? 5.7) in women. On the other hand, all cancers combined, 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.
Hwang et al concluded:
The results suggest that prolonged low dose-rate radiation exposure appeared to increase risks of developing certain cancers in specific subgroups of this population in Taiwan.
So, basically, Coulter is completely wrong about the Taiwan incident. There is an increased incidence of cancer in young people, at least, who lived in those apartment buildings. Science is hard, isna??t it? Coultera??s also on seriously dubious footing when she cites Professor Bernard L. Cohen, whose various studies of the relationship between radon and lung cancer buck the established consensus that radon is a risk factor for lung cancer. (Yes, this is the very same Bernard Cohen who wrote the JPANDS article I mentioned earlier in this post; to me his having published in JPANDS is to me a huge hit on any credibility he might have had.) It turns out that Cohen probably didna??t control adequately for smoking in his studies because a reanalysis of his reported data demonstrated similar, strongly negative correlations between radon exposure and cancers strongly linked to cigarette smoking and weaker negative correlations between radon and cancers moderately associated with smoking. No such correlation was found for cancers not linked to smoking. These results strongly suggest that Cohen didna??t adequately control for smoking in his analysis. Another criticism points out that Cohen fell prey to the ecological fallacy and suggested that county-level data probably do not represent the best units to detect a correlation between radon and lung cancer.
Coultera??s final claims center on the Chernobyl disaster and victims of the atomic bombings of Hiroshima and Nagasaki. In particular, she claims that only 30 people died in the plant as a direct result of the disaster and further downplays the risk of cancer in the survivors, stating:
Even the thyroid cancers in people who lived near the reactor were attributed to low iodine in the Russian diet a?? and consequently had no effect on the cancer rate.
As is usually the case for any scientific claims made by Coulter, this is utter rubbish. Unfortunately for Coulter, her timing in publishing her article was exquisitely bad. On the very next day after her article was published, the National Cancer Institute released the most comprehensive study yet of thyroid cancer in Chernobyl survivors. The findings indicated that radioactive iodine (131I) from the fallout from the reactor was likely responsible for thyroid cancers that are still occurring among people who lived near the reactor and that the risk of this cancer is not declining. In other words, no, Ann, the hugely elevated levels of thyroid cancer among people who live near Chernobyl when the reactor disaster occurred are not due to iodine deficiency in the Russian diet. There is some evidence that iodine deficiency might have increased the risk of 131I-induced cancers, particularly in the youngest, but thata??s not what Coulter said. She implied that iodine deficiency could account for the elevated incidence of thyroid cancer among those affected by the fallout. Much more about the health effects of the Chernobyl disaster can be found here. It should also be noted that most people who lived in the area were not exposed to that much radiation according to the United Nations-sponsored team investigating. Most were exposed to about 9 mSv, about 1/3 the equivalent of a CT scan of the chest, abdomen, and pelvis, once the short-term doses to the thyroid were subtracted
Poor Ann. Thata??s what you get for not doing a bit more research. Basically, every claim she makes in her article can be shown to be either mistaken, grossly exaggerated, or based on old evidence. She even cites Tom Bethell, author of The Politically Incorrect Guide to Science, as a source. Bethell is an all-purpose right-wing science denialist, who, besides viewing scientists as attention whores who trump up alarmist findings in order to secure more research funding and castigates science for its commitment to a??materialism,a?? also denies evolution and anthropogenic global warming. He even rejects relativity and embraces a??AIDS reappraisal,a?? while extending his view on hormesis to argue that hormesis actually protects us from toxic chemicals in the environment that, according to him, we dona??t have to worry about nearly as much as environmentalists say we do. In fact, Coulter includes a paragraph in her article that is so unintentionally hilarious that I cana??t help but cite it:
Although it is hardly a settled scientific fact that excess radiation is a health benefit, therea??s certainly evidence that it decreases the risk of some cancers a?? and there are plenty of scientists willing to say so. But Jenny McCarthya??s vaccine theories get more press than Harvard physics professorsa?? studies on the potential benefits of radiation. (And they say conservatives are anti-science!)
I doubt that Coulter appreciates the irony encompassed by this paragraph, given that this paragraph is further encompassed by an article that uses many of the same deceptive techniques of argumentation that the anti-vaccine movement, as epitomized by Jenny McCarthy, likes to use. She then digs herself in deeper by correctly mentioning that Botox is a poison that is safe to use at high doses (Jenny McCarthy loves Botox, actually) and then pointing out the principle that many poisons are safe and beneficial at low doses but dangerous at high doses. If these arguments didna??t occur within the context of her spewing of misinformation, Coulter might actually be making some sense. Too bad she couldna??t resist adding:
Every day Americans pop multivitamins containing trace amount of zinc, magnesium, selenium, copper, manganese, chromium, molybdenum, nickel, boron a?? all poisons.
They get flu shots.
Perhaps Coulter has more in common with Jenny McCarthy than she would like to admit. Actually, therea??s no a??perhapsa?? about it. Coulter will also say whatever fits her political viewpoint. Last week she was ranting about how radiation is good for you. Back in November, she was complaining that the new Transportation Security Administration scanners do pose a a??radiological danger.a??
These scanners result in a dose of 0.001 mSv for about 5 seconds of full body exposure, and even frequent fliers would be exposed to much less radiation than Coulter is claiming to be just fine. Indeed, Ann Coulter should be lining up to be scanned. After all, that little radiation is good for you!
Is hormesis a real phenomenon?
Despite my irritation, I was rather grateful for Coultera??s article. It did remind me of a rather fascinating debate in radiobiology over what model best describes the biological effects of radiation. Hormesis might indeed be a real phenomenon in humans, but ita??s been very difficult to demonstrate. Even one of the best review articles Ia??ve found that argues for the existence of hormesis as a phenomenon, an article by Tubiana et al entitled The Linear No-Threshold Relationship Is Inconsistent with Radiation Biologic and Experimental Data doesna??t exactly argue for hormesis. Rather, it argues that the LNT model is inconsistent with the data and needs to be modified to more of a threshold model, in which doses below a certain threshold are probably harmless but above a certain threshold start to increase the risk of disease. Arrayed against these sorts of arguments are scientists like Rudi H. Nussbaum and Wolfgang K??hnlein, who call hormesis and the zero-risk threshold dose a??scientifically refuted, but stubborn myths.a?? They even argue that in some cases the risk of low level radiation exposure might well be underestimated. Not surprisingly, in her article Coulter used nearly every myth that Nussbaum and K??hnlein deconstruct in their paper.
Hormesis is clearly an area of science that is as yet controversial. The reason is because ita??s difficult to demonstrate definitively one way or another whether hormesis occurs in humans in response to low dose radiation. As I mentioned above, the signal-to-noise ratio for studies of low dose radiation is very low. Moreover, studies of low dose radiation have been conflicting, although we can say with a fair amount of confidence, based on my review of the literature, that, if hormesis occurs, it probably occurs only below doses of 100 mSv. Remember, 30 mSv is the dose received from a CT scan of the chest, abdomen, and pelvis and can be estimated to increase onea??s lifetime risk of a fatal cancer by 1 in 1000 to 1 in 500 in pediatric patients, while most people receive around 3 mSv per year from background radiation. To put this all into context, XKCD has a very useful chart that describes how much radiation we receive from various sources. Another good perspective comes from a recent AP article on the topic, which takes a much more balanced perspective.
The bottom line is that we just dona??t know whether hormesis is a real phenomenon for radiation response in humans. Lacking that knowledge, we do know that the LNT model is a reasonable approximation for purposes of regulation because it is simple and defensible. Even so, different professional organization bodies have started to question it. For example, the French Academy of Sciences and National Academy of Medicine published a report in 2005 that stated:
In conclusion, this report raises doubts on the validity of using LNT for evaluating the carcinogenic risk of low doses (< 100 mSv) and even more for very low doses (< 10 mSv). The LNT concept can be a useful pragmatic tool for assessing rules in radioprotection for doses above 10 mSv; however since it is not based on biological concepts of our current knowledge, it should not be used without precaution for assessing by extrapolation the risks associated with low and even more so, with very low doses (< 10 mSv), especially for benefit-risk assessments imposed on radiologists by the European directive 97-43.
The Health Physics Societya??s position statement, revised in July 2010, states:
In accordance with current knowledge of radiation health risks, the Health Physics Society recommends against quantitative estimation of health risks below an individual dose of 5 rem in one year or a lifetime dose of 10 rem above that received from natural sources. Doses from natural background radiation in the United States average about 0.3 rem per year. A dose of 5 rem will be accumulated in the first 17 years of life and about 25 rem in a lifetime of 80 years. Estimation of health risk associated with radiation doses that are of similar magnitude as those received from natural sources should be strictly qualitative and encompass a range of hypothetical health outcomes, including the possibility of no adverse health effects at such low levels.
Again, we just dona??t know. My guess is that hormesis, if it occurs in humans in response to radiation, is not nearly as potent a phenomenon as its adherents claim. My further guess is that the way hormesis is invoked as a scientific explanation for homeopathy doesna??t help its reputation. Be that as it may, until science settles the question, I do know that, contrary to what Coulter claims in her nonsensical arguments, low dose radiation is not a magical a??cancer vaccine.a?? At the very best, low dose radiation might not hurt you or might have some very slight benefits. At worst, it might actually hurt you more than the current scientific consensus accepts. Thata??s too wide range of possibilities and too much uncertainty to be laying down a barrage of misinformation as intense as Coultera??s.
ADDENDUM: Herea??s an amusing little takedown of Coultera??s nonsense, for your edification. I had a good chuckle at this comment by Gordon Bloyer, who writes:
Schultz telling anyone about science, LOL. Coulter wrote an extensive column using back-up from science. Sgt. Ed should learn to read.
Coulter didna??t give her a??theorya?? she cited science. She is right and Oa??Reilly just shoots off his mouth before he lets others complete a sentence. In this case he had NO IDEA what Coulter was talking about.
I invite Gordon to read my discussion of hormesis and see that the a??back-up from sciencea?? that Coulter used is anything but. I do thank Gordon, though, for a moment of hilarity in a painful day of grant writing. Ditto felixw, who comments:
I know that Oa??Reilly went to Harvard. And Ann Coulter graduated cum laude from Cornell, where she founded The Cornell Review before getting her law degree at the University of Michigan, where she edited the law review. Then she clerked for the United States Court of Appeals for the Eighth Circuit.
Given how much a law school education has to do with science, by this logic, I should be able to confidently and definitively make pronouncements on the law! After all, I graduated from the University of Michigan, too, just like Ann Coulter!
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