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Just what we needed, Dr Hanson, more divisions among the greens! As I understand you, Sir, you wish to substitute dumping fossil-fuel wastes into the atmosphere with dumping nuclear wastes into the ground (if we are lucky!) Rather insane, I would say.

I have admired James Hansen for decades and support his work on climate change, and his calls to urgent action. However, his work re the health impacts of low level radiation is substandard. In “Prevented Mortality and Greenhouse Gas Emissions from Historical and Projected Nuclear Power” Kharecha and Hansen calculate 4,900 deaths from nuclear power, a mere 43 of them from Chernobyl, and speak of “the generally accepted 100 mSv threshold for fatal disease development”. Annex D of UNSCEAR 2008 is quoted selectively in support. Overall, on the issue of low-level radiation and its health effects, their paper is demonstrably misleading and bad science. CHERNOBYL FORUM In April 2006, the World Health Organisation, having 4 years earlier setup the Chernobyl Forum, published “Health effects of the Chernobyl accident: an overview” ( http://www.who.int/ionizing_radiation/chernobyl/backgrounder/en/index.html ). While acknowledging uncertainties (are there no uncertainties in Kharecha and Hansen’s fields?) re the MAGNITUDE - not the existence - of the health risks, they stated “The Expert Group concluded that there may be up to 4 000 additional cancer deaths among the three highest exposed groups over their lifetime (240 000 liquidators; 116 000 evacuees and the 270 000 residents of the SCZs)”. Re the five million residents of the more highly contaminated areas of Belarus, the Russian Federation and Ukraine, the WHO stated that “Predictions, generally based on the LNT model, suggest that up to 5 000 additional cancer deaths may occur in this population from radiation exposure” . A neutral scientist might be expected to at least refer to this. UNSCEAR 2008 Although the 2008 UNSCEAR document to which Kharecha and Hansen refer does emphasise uncertainties at low doses, it does NOT, as Kharecha and Hansen do, thereby dismiss the risks altogether. UNSCEAR 2008, in contrast to earlier WHO documents, takes a somewhat Pontius Pilate position, refusing to give any estimates for cancer induction, and warning repeatedly of uncertainties, and of “potentially serious misinterpretation in communication with the public”. Whatever about the wisdom of this decision by UNSCEAR - and it looks much more a political decision than a scientific one - the result has been a deluge of blanket statements, many from positions of apparent scientific authority and influence, citing UNSCEAR to the effect that Chernobyl’s death toll is a mere 50, with the implication this is a more or less final figure. This is a "serious misinterpretation" of UNSCEAR 2008, about which UNSCEAR has, to my knowledge, done absolutely nothing. However, even this controversial and somewhat peculiar UNSCEAR 2008 document, quoted approvingly by Kharecha and Hansen, clearly and specifically warns that “Although the numbers of cancers projected to be induced by radiation exposure after the accident are very small relative to the baseline cancer risk, THEY COULD BE SUBSTANTIAL IN ABSOLUTE TERMS” (My emphasis – even a "very small" increase of say, 0.5%, in baseline risk would cause 5,000 extra cancers in a 5 million population, assuming normal cancer mortality of 20% of all deaths. Again, one would expect neutral observers to mention this. Furthermore, Kharecha and Hansen’s source (UNSCEAR 2008) shows in Table B19 that the 530,000 recovery operators received an average dose of 117 mSv, in excess of Kharecha and Hansen’s supposed “generally accepted 100 mSv threshold for fatal disease development”. Using LNT, this would point to over 3,000 excess cancers eventually developing among the recovery workers alone. ICRP - 10mSv CT scan - risk one in 2,000 of fatal cancer Again using Table B19, the 6.4 million inhabitants of the most contaminated areas of Russia, Belarus and Ukraine got an average dose of 9mSv. Even the standard-setting body for the nuclear and radiological industries, The International Commission on Radiological Protection (ICRP), in its "Radiation and your Patient: A guide for Medical |Practitioners” states that “The higher dose diagnostic medical procedures (such a CT scan of the abdomen or pelvis) yield an effective dose of about 10 mSv. If there were a large population in which every person had 1 such scan, the theoretical lifetime risk of radiation induced fatal cancer would be about 1 in 2,000 (0.05%).” The question arises then, of why a dose of 10 mSv is sufficient to warn doctors, and presumably patients, of a risk, but not sufficient for Kharecha and Hansen (or UNSCEAR 2008) to include in their calculations. One assumes that doctors’ patients are no more important and no more vulnerable to radiation than other citizens. Using those ICRP risk estimates would indicate a further 3,000 induced fatal cancers. (Note 1. If the data demonstrate – see Martin et al below - linear effects from 2,500 mSV down through 2,000mSv down through 1,000, 500, 250, 100, 50, 40, 20, and 10 mSV, I hope I can be forgiven for assuming that the graph will continue down to 9mSv. Note 2. UNSCEAR’s 2008, and apparently current, position that LNT (firmly based on decades of research, not least by the Radiation Effects Research Foundation http://www.rerf.jp/index_e.html Life Span Study of survivors from the Hiroshima and Nagasaki bombings) IS suitable as a precautionary measure for radiological protection, in spite of uncertainties, but that the same LNT, based on the same studies, is NOT suitable for ANY estimation of cancer fatalities, because of uncertainties, is, to say the least, somewhat tortured, and likely in itself to give rise to serious confusion, if not outright derision and even outrage, among the public. Note 3. Even UNSCEAR now (2010) admits "Risk estimates vary with age, with younger people generally being more sensitive; studies of in utero radiation exposures show that the foetus is particularly sensitive, with elevated risk being detected at doses of 10 mSv and above." NB 10 (ie TEN) mSv, NOT 100 mSv. http://www.unscear.org/docs/reports/2010/UNSCEAR_2010_Report_M.pdf And UNSCEAR 2013 states "For a given radiation dose, children are generally at more risk of tumour induction than are adults. Cancers potentially induced by exposure to ionizing radiation at young ages may occur within a few years, but also decades later. In its report on its fifty-fourth session, the Committee stated that estimates of lifetime cancer risk for those exposed as children were uncertain and might be a factor of 2 to 3 times as high as estimates for a population exposed at all ages." Volume II SCIENTIFIC ANNEX B: Effects of radiation exposure of children http://www.unscear.org/docs/reports/2013/UNSCEAR2013Report_AnnexB_Children_13-87320_Ebook_web.pdf 100 mSv NOT a threshold Kharecha and Hansen talk of “the generally accepted 100 mSv threshold for fatal disease development “, and based on startlingly limited evidence, suggest that LNT “might not be valid for the relatively low radiation doses that the public was exposed to from nuclear power plant accidents”. They, and ACS Publications, might like to consider the following from "The radiobiology/radiation protection interface in Healthcare" (Martin et al, 2009), published by the Journal of Radiological Protection and available at the Institute of Physics website. "The 21st L H Gray conference gathered leading experts in radiobiology, radiation epidemiology, radiation effect modelling, and the application of radiation in medicine to provide an overview of the subject......... Epidemiological evidence from the Japanese A-bomb survivors provides strong evidence that there is a linear relationship between the excess risk of cancer and organ dose that extends from about 50 mSv up to 2.5 Sv, and results from pooled data for multiple epidemiological studies indicate that risks extend down to doses of 20 mSv. Thus linear extrapolation of the A-bomb dose-effect data provides an appropriate basis for radiological protection standards at the present time..... The Japanese A-bomb survivor group provides data for a population with a wide range of ages who received relatively high doses primarily from external radiation....... The results have proved that there is a linear relationship between cancer risk and organ dose between about 100 mSv and 2.5 Sv (Hall 2009). If data from A-bomb survivors who received doses between 5 and 125 mSv are grouped together and the excess risk plotted against a mean dose, the data give a definite excess relative risk for cancer mortality and a value which agrees with the LNT extrapolation of the A-bomb survivor data for a mean dose of about 40 mSv (Brenner et al 2003)......... Another area of study which is relevant when considering carcinogenic effects at low doses is the induction of childhood leukaemia in children radiographed in utero with doses of 10-20 mSv (Stewart et al 1956, Knox et al 1987). These studies provide further evidence that effects do occur at doses down to 10 or 20 mSv....... . Data from the UK, USA and Canada have been combined to give results for 95 000 radiation workers who received a mean individual cumulative dose of 40 mSv (Cardis et al 1995) and data from 15 countries pooled to give 400 000 workers with a mean cumulative dose of 19.4 mSv (Cardis et al 2005b). Results from both studies indicate an excess relative risk of leukaemia that is statistically significant........... Comparative studies on groups exposed to different levels of natural background radiation do not have the statistical power to detect effects on cancer incidence, because of the small numbers receiving higher doses (BEIR 2006, Hendry et al 2009). Based on current risk estimates a population of 10 million would be required in order to prove whether there was a high incidence of solid cancer in an area where the population was exposed to 10 mSv yr−1, whereas the populations that have been studied comprise less than 100 000 individuals. Populations that have higher doses from radon exposure provide the best indicator of a link between cancer and dose at lower dose levels. Results of a European project, which combined data from a number of individual case control studies in member states, show a clear increase in the risk of lung cancer among residents of homes with an enhanced concentration of radon (above 150 Bq m−3)...... ...the LNT dose-effect model is the most appropriate one to adopt to describe the risks of cancer and provides a workable practical framework for the operation of protection............." . Kharecha and Hansen, and ACS Publications, might also wish to consider the following from the British Journal of Radiology : "The linear no-threshold model In this section we emphasise human cancer data, rather than surrogate end points. The linear no-threshold (LNT) model assumes a curvature at moderate doses, but linearity at low doses or low dose rates. However, for the low doses and dose rates relevant to diagnostic radiology, the curve can be assumed to be linear (Figure 1, curve c). It is consistent with the data for solid tumours at doses <1.5 Gy in the Life Span Study. The central assumption made with the LNT model is that the rate-limiting event in low-dose radiation carcinogenesis is due to “one-track action”, e.g. one or more DNA double strand breaks (DSBs) caused by a single electron track. Dose is directly proportional to track number. Cancer risk owing to one-track action is therefore proportional to dose, with any dose, no matter how small, able to induce cancer (although extremely unlikely to do so). The main rationale for the one-track action assumption is as follows: • Epidemiological evidence from the studies of in utero radiation exposure has shown that a dose of 6 mGy is associated with an increase in cancer risk [4]. • A subsequent comprehensive review in 1997 by Doll and Wakeford [5] concluded that fetal irradiation in utero with diagnostic X-rays giving an organ dose of 10 mGy produced a consequent increase in the risk of childhood cancer. • It is known that, at the dose of 10 mGy, one cell nucleus is typically irradiated with ∼10 electron tracks or fewer, depending on the details of the cell and the low-LET radiation [6]. The tracks are then typically far apart in space (>1 μm) and in time (>1 ms). On biophysical grounds it is difficult (although, as discussed later, not impossible) to conceive how two independent electron tracks that are remote in space and time can cooperate (synergistically or agonistically) to increase or decrease the cancer risk. Thus it can be concluded that in all likelihood the key rate-limiting event at 10 mGy is due to one-track action. • If one-track action can cause cancer, then it follows that reducing the radiation dose by a factor of 10 will simply reduce the number of electron tracks by a factor of 10, and therefore reduce the probability of cancer initiation by the same factor. • A linear model, with no threshold dose below which radiation is safe, is therefore the most appropriate model in the absence of strong evidence to the contrary. There is considerable, though not universal, consensus in the radiation protection community that radiation-induced cancer can occur at the doses and dose rates* encountered in diagnostic medical radiation. Although little epidemiological evidence exists for the precise shape of the dose–response curve at radiation doses <0.15 Gy, mechanistic radiobiological data would support the conceptual canonical theory of a single electron track potentially inducing cancer. Although some theories of radiation risk predict even higher risks at low doses, this LNT model is among the more conservative estimates. It is prudent that the LNT model should continue to be used as the basis for radiation protection policy, including that which is applicable to diagnostic radiology. There is no consistent evidence to support a departure from the LNT model, either by introducing a threshold level of “safe” radiation or by altering the shape of the LNT curve at low doses." Radiation-induced cancer: a modern view D J Shah, MRCS, FRCR1, R K Sachs, PhD2,3 and D J Wilson, FRCP, FRCR4 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3611719/ Richard Doll As far back as 2003, Brenner, Richard Doll (I assume the Richard Doll who finally nailed the link between re cancer and smoking) et al asked “First, what is the lowest dose of x- or γ-radiation for which good evidence exists of increased cancer risks in humans? The epidemiological data suggest that it is ≈10–50 mSv for an acute exposure and ≈50–100 mSv for a protracted exposure. Second, what is the most appropriate way to extrapolate such cancer risk estimates to still lower doses? 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..” Cancer risks attributable to low doses of ionizing radiation: Assessing what we really know Proceedings of the National Academy of Sciences http://www.pnas.org/content/100/24/13761.full Dr. Ian Fairlie The radiobiologist Dr. Ian Fairlie has written "It is dispiriting to read many articles – on both sides of the Atlantic – by media pundits and poorly-informed scientists about low-level radiation risks. These articles commonly assert, with little or no evidence, that there is nothing to worry about radiation and that nuclear projects are encumbered by overly strict safety limits. In particular, they usually state that no risks are seen below 100 mSv; that the Linear No-Threshold (LNT) model is wrong; and that there were only about 50 deaths at Chernobyl with no more expected. There often seems to be a close relationship between the level of ignorance evidenced in articles on this subject and the over-confidence with which they are written." http://www.ianfairlie.org/news/recent-evidence-on-the-risks-of-very-low-level-radiation/ Background radiation A January 2013 study found effects from natural background radiation (a few mSv): “We conducted a large record-based case-control study testing associations between childhood cancer and natural background radiation. Cases (27,447) born and diagnosed in Great Britain during 1980-2006 and matched cancer-free controls (36,793) were from the National Registry of Childhood Tumours. Radiation exposures were estimated for mother's residence at the child's birth from national databases, using the County District mean for gamma rays, and a predictive map based on domestic measurements grouped by geological boundaries for radon. There was 12% excess relative risk (ERR) (95% CI 3, 22; two-sided P=0.01) of childhood leukaemia per millisievert of cumulative red bone marrow dose from gamma radiation; the analogous association for radon was not significant, ERR 3% (95% CI -4, 11; P=0.35). Associations for other childhood cancers were not significant for either exposure. Excess risk was insensitive to adjustment for measures of socio-economic status. The statistically significant leukaemia risk reported in this reasonably powered study (power ~50%) is consistent with high-dose rate predictions. Substantial bias is unlikely, and we cannot identify mechanisms by which confounding might plausibly account for the association, which we regard as likely to be causal. The study supports the extrapolation of high-dose rate risk models to protracted exposures at natural background exposure levels. A record-based case-control study of natural background radiation and the incidence of childhood leukaemia andother cancers in Great Britain during 1980-2006. Kendall GM, Little MP, Wakeford R, Bunch KJ, Miles JC, Vincent TJ, Meara JR, Murphy MF. http://www.ncbi.nlm.nih.gov/pubmed/?term=A+record-based+case–control+study+of+natural+background+radiation+and+the+incidence+of+childhood+leukaemia+and+other+cancers+in+Great+Britain+during+1980–2006.+Leukemia Application of LNT to the 98 million citizens affected by an average dose of 1.3 mSv ( http://www.unscear.org/docs/reports/2008/11-80076_Report_2008_Annex_D.pdf Table B19) would give a further 6,000 fatal cancers. There is currently no strong evidence for effects at the 0.3 mSv average dose level received by 500 million people outside the old Soviet Union, and the enormous size of studies necessary makes it unlikely this question will ever be resolved epidemiologically, but if effects have been credibly demonstrated at lower and lower levels (the 100 mSv “threshold” endlessly touted is ancient history now), right down to natural background level, it would be prudent, logical and scientific, if public health is genuinely a concern, to assume the graph continues. Applying LNT here gives a further 8,000 fatal cancers. Leukemia among cleanup workers Re Kharecha and Hansen’s quote from UNSCEAR 2008 that “reports of an increase in leukemia among recovery workers who received higher doses are inconclusive”, a 2013 study of a very large (110,000) group of Chernobyl cleanup workers by Zablotska et al , might be of interest: “Exposure to low doses and to low dose-rates of radiation from post-Chornobyl cleanup work was associated with a significant increase in risk of leukemia, which was statistically consistent with estimates for the Japanese atomic bomb survivors." Radiation and the Risk of Chronic Lymphocytic and Other Leukemias among Chornobyl Cleanup Workers ( http://ehp.niehs.nih.gov/1204996/ ) Conclusion Kharecha and Hansen’s information is out of date, (as is UNSCEAR 2008), and reads more like naive nuclear propaganda than science. While some people have exaggerated the known risks from radiation, and the public often has exaggerated fears, that is poor excuse for scientifically-trained people to make similar errors of a similar order of magnitude in the opposite direction. Rather than give a range of values with different degrees of confidence, UNSCEAR has used uncertainty to avoid making any estimate at all. Kharecha and Hansen have, incredibly, gone a huge step further, and turned UNSCEAR’s concerns about uncertainty into an completely unwarranted dismissal of risks altogether. By claiming 43 as Chernobyl’s death toll, and with their ill-informed questioning of LNT, they put themselves in dubious “safe threshold”/“hormesis” company, well outside the long-established radiological consensus, increasingly firmly grounded in epidemiology and theory. They are entitled to their minority poorly-informed opinions, but should not be allowed to parade them as established fact or science. Yours sincerely, Chris Murray.

Ben Heard and Geoff Russell have attacked Jim Green over alleged mistakes in Jim's treatment of ExternE reports. They laud ExternE to the hilt (1). However, ExternE actually calculates 0.65 deaths per terrawatt hour from ROUTINE nuclear cycle operation (2), rather than the 0.04 TOTAL deaths per terrawatt hour which has entered urban legend (probably largely through Brian Wang's pro-nuclear NextBigFuture site?). This alone would put nuclear more dangerous than wind and even rooftop solar. ExternE also estimated 10,000 - 50,000 fatal cancers from Chernobyl (3). Have Heard and Russell actually read the ExternE reports or am I missing something? 1. "ExternE was a 15 year research process involving a “multidisciplinary research team, composed of engineers, economists and epidemiologists, to develop an original methodology” and that methodology is 'widely accepted by the scientific community and is considered as the world reference in the field'”. 2. (http://www.externe.info/externe_d7/sites/default/files/vol5.pdf page 5) 3. ExternE Externalities of Energy Methodology 2005 Update Edited by Peter Bickel and Rainer Friedrich Page 205 Figure 9.4)