Some people have interpreted this article as being pro-nuclear. That is not the intention of this article. The intention is to analyse the evidence put forward by Helen Caldicott's recent article in the Guardian. It is that article that mentions only Iodine-131 and Caesium-137, and hence I limit my discussion to that. Anyone who strongly argues their position needs to put forward evidence supporting their position and that evidence needs to stand up to scrutiny. My opinion is that Helen's article does not present reliable evidence that supports her position. There is no doubt that radiation is dangerous to life, and I do not seek to imply otherwise. If the way in which nuclear powerstations are run and operated results in pressure on the companies operating those powerstations to cut corners and endanger the population then that is a fault that needs addressing, but it is a separate issue from the safety (or otherwise) of nuclear power as a technology.

The events at Fukushima have brought into the public's gaze three issues regarding the arguments surrounding nuclear power. The pro- and anti-nuclear groups themselves get attention and the ability to put forth their sides of the story, and the media's science correspondents get accused of knowing next to nothing about the various issues of nuclear power.

In Helen Caldicott's recent piece, which itself was in response to George Monbiot's decision to move from a position of ambivalence to one of supporting nuclear technology, Helen suggests that those in favour of nuclear power misinform the media, whilst many others (such as George) accuse the anti-nuclear lobby of the very same thing. What is clearly obvious is that for both sides to claim the high ground, there must be an awful lot of misinformation going around, and as with any complex issue, there are intricacies and subtleties that the media and the public at large do not have time to dwell on at length.

Comparing the two articles reveals some interesting differences: George states in the first paragraph that he previously defined himself as "nuclear-neutral", but now "supports the technology". In the fifth paragraph he further defines himself as a green who is in favour of renewable energy. Personally, I loathe the term "renewable": it suggests that you can get energy for nothing, which most secondary-school physicists will be able to tell you is a violation of the laws of physics. I would love to see a study considering what would happen if the earth gathered 100% of its energy requirements from wind power. I suspect that the moon would fall out of orbit and destroy human life on earth, but I digress.

Helen, by contrast does not state her position so clearly, although she does link immediately to an article in which she warns of the potential for a "medical problem of very large dimensions". That article very clearly starts by describing her as a controversial opponent of nuclear power. On her website, she describes herself as "The single most articulate and passionate advocate of citizen action to remedy the nuclear and environmental crises", a phrase that leaves little doubt as to what her position is on the matter. A "crisis" is not personally how I'd describe the world's use of nuclear power: famine is a crisis; AIDS is a crisis; the current unrest in the Middle East and north Africa is a crisis; class-A drug abuse is a crisis; and the 100 serious or fatal road accidents that occur in Great Britain every day is probably an oft-overlooked crisis. The ageing population is a crisis; the debt-ridden younger generations is a crisis. Our reliance on fossil fuels is possibly a crisis. I'm yet to be convinced our use of nuclear power is a crisis.

I should clearly declare my own positions at this point. I am a software engineer. I spend a lot of time thinking logically, and I took A-levels in Chemistry, Physics and a lot of Maths before studying Computer Science at Imperial College, London. After completing my Masters degree at Imperial, I completed 2.5 years of a PhD in Computing before leaving and entering industry where I remain today. I am in favour of rigorous science and an unemotional approach to numbers. For example, in 2008, research revealed that the cost to the NHS of treating smoking related illnesses is £2.7bn per year. In the very same article, it states "current UK tax revenue from tobacco is around £10 billion". Thus from a purely numeric point of view, the government seems to get over £7bn per year from smokers that need not be spent on smokers but can be put to other uses. Whilst smoking is a poor health choice on a personal level, is it bad for society given these numbers?

To return to Helen and George. One of the criticisms that George has of Helen in his April 5th article is that after requesting sources of information supporting her claims, there were very few if any peer reviewed papers that were sent back that supported her claims. In Helen's rebuttal, she has provided footnotes and links to studies.

She explains the difference between external and internal radiation. This can be summarised as "if you ate or inhaled something radioactive, you have are going to suffer internal radiation". She then states:

"Hazardous radionuclides such as iodine-131, caesium-137, and other isotopes currently being released in the sea and air around Fukushima bio-concentrate at each step of various food chains (for example into algae, crustaceans, small fish, bigger fish, then humans; or soil, grass, cow's meat and milk, then humans)."

There are two things that are missing here: one is a discussion of half-lives, and the other is a discussion of the different types of radiation.

The "half life" is the time taken for half of an amount of radioactive substance to disappear. If you have 1kg of a radioactive substance that has a half life of 5 days, then 5 days later, you'll have 500g of that substance (you'll very likely have something that weighs more than 500g, because as a radioactive substance decays, it doesn't just disappear: it turns into something else, which may or may not itself be radioactive. But you will have 500g left of the original radioactive substance). Five days after that, you'll have 250g left of the original radioactive substance and so on: it halves every 5 days.

Iodine-131 has a half life of 8.0197 days. Thus if you start with 1kg of iodine-131, then you'll have about 500g of iodine-131 after 8 days. After 30 days, there will have been 3.7 halvings, and so you'll have just 74.8g left of it (1000 / 2^(30/8.0197) = 74.8). After 365 days, you'll have had 45.5 halvings: less than one-billionth of a gram of iodine-131 will remain. When iodine-131 decays, it turns into xenon-131 which is a gas normally on Earth (it becomes a liquid below −108°C), and is not radioactive in this form. Thus after 1 year, your initial 1kg lump of iodine-131 will have turned into almost 1kg of xenon-131. The xenon-131, being a gas and not being radioactive, will disperse into the atmosphere and will not cause any harm.

The other issue is the type of radiation. There are three types of radiation, given the exciting names of "alpha", "beta" and "gamma" radiation. Alpha-radiation is produced by radioactive substances that undergo alpha-decay. Alpha-radiation is very bad for you, but fortunately, alpha-particles are easy to stop: they can't get through a single sheet of paper, and your skin easily stops them. However, alpha-particles are extremely dangerous if ingested. Do not eat. Beta-radiation is produced by radioactive substances that undergo beta-decay. Beta-particles are harder to stop: something like a few millimetres of aluminium is necessary to stop beta-particles, but although they can thus enter the body externally, they are less likely to do you harm than alpha-particles once inside you. Gamma-radiation is produced by substances that undergo gamma-decay. There's no such thing as a gamma-particle as gamma-radiation is an electromagnetic wave: it's very similar to the electromagnetic waves that pass through you when you have an X-ray. They are very difficult to stop: you need quite a lot of lead to absorb gamma-rays, but they're not likely to do you much harm unless you're exposed to an awful lot of them. The Earth receives an awful lot of gamma-rays from the Sun all the time. The Earth's magnetic field (think of the Earth as a large magnet from the South-pole to the North-pole) extends out into Space and deflects a lot of this radiation from the Sun away from us. However, the higher up in the atmosphere you are, the more gamma-rays pass through you from the Sun as there is less atmosphere to shield you. This is why people have been comparing the amount of gamma-radiation workers have been exposed to to what you receive in a trans-atlantic flight, or a flight from Tokyo to New York.

When iodine-131 decays, it releases beta-particles and gamma-rays, but no alpha-particles. Helen doesn't just suggest iodine-131, she also suggests caesium-137. Caesium-137 has a half life of 30.17 years, thus it stays around much longer than iodine-131. Caesium-137, which was released by during the Chernobyl accident, still exists today and is present in, for example, pigs in Germany, rendering them unsafe for human consumption. Caesium-137, like iodine-131, decays producing gamma-rays and beta-particles, and no alpha-particles. However, much of the coverage to date has focused on the iodine-131 released by the reactor at Chernobyl that then got into milk which was drunk. Why has caesium-137, which lasts for much longer, not featured so prominently in coverage of the past and potential future dangers? One of the reasons is that in accidents like Chernobyl, lots of different radioactive substances were released and thus it is difficult to say with any certainty that caesium-137 in particular caused any of the illnesses associated with radiation exposure. It is only because it is known that iodine is absorbed by the thyroid that intake of iodine-131 is known to cause increased rates of thyroid cancer.

Thus the questions we need answers to are: 1) how quickly can iodine-131 pass through the food chain (if it takes too long then the relatively short half-live of iodine-131 will ensure that little iodine-131 reaches organisms high up the food chain)? 2) can caesium-137 and other isotopes similarly pass through the food chain (which requires them to be easily ingestible or absorbed by other organisms; e.g. caesium-137 is water-soluble which means it dissolves in water and thus can be easily ingested by drinking contaminated water)? 3) how much of these radioactive substances need to be ingested for any known radiological health consequences to occur? and 4) is this possible given the rate of contamination coming from the reactors at Fukushima?

After making the earlier statement, Helen links to two studies: 1. J.U. Clark and V.A. McFarland, Assessing Bioaccumulation in Aquatic Organisms Exposed to Contaminated Sediments, Miscellaneous Paper D-91-2 (1991), Environmental Laboratory, Waterways Experiment Station, Vicksburg; 2. MS and H.A. Vanderplog, D.C. Parzyck, W.H. Wilcox, J.R. Kercher, and S.V. Kaye, Bioaccumulation Factors for Radionuclides in Freshwater Biota, ORNL-5002 (1975), Environmental Sciences Division Publication, Number 783, Oak Ridge National Laboratory, Oak Ridge, TN).

As the titles suggest, these two studies are both concerned with accumulation in organisms that live in water. Not humans, or cows. The first paper seems to have absolutely nothing to do with the accumulation of radioactive substances by algae, crustaceans or fish. The paper is about being able to predict the effect of toxic bioaccumulation in aquatic organisms exposed to contaminated sediments caused by dredging operations. It's a report from an army writer, it is not widely cited, and almost certainly not peer-reviewed. The second paper is much more useful, being the analysis of over 200 other "carefully selected papers" studying the bioaccumulation of radioactive isotopes in freshwater environments. We learn that caesium is easily absorbed into an organism from its food and it tends to stay absorbed about three times more easily than it is expelled, which means that if fish A tends to eat lots of fish B, then fish A will end up with a concentration of caesium 3 times higher than found in fish B. It says that "the bioaccumulation factor for caesium is highly variable from one environment to another". It says that iodine is easily absorbed by the thyroid tissue of vertebrates (and thus fishes), but goes to some length to explain that there is limited data available regarding iodine in fish thyroid and ovaries and thus at best, they are reporting approximations. As with caesium-137, fish can easily ingest iodine-131 through the food chain, but the authors report there are very few studies measuring the absorption of iodine-131 in fish, and no mention is made of the dosages required to harm the health of the fish. It should also not be forgotten that this second study, although being the more useful of the two, is nevertheless from 1975. I'm surprised there are not more recent studies in this area.

However, few of our questions have been answered: yes, it would seem iodine-131, caesium-137 and others can be absorbed by fish, but we've learnt nothing about how much of these substances is harmful to the fish, or, more importantly, is harmful to a human. If a fish absorbs some iodine-131, doesn't fall ill, and is then caught and eaten by a human, is that iodine-131 more or less dangerous in the human than in the fish? Given in both organisms, iodine-131 affects the thyroid, and given humans are much bigger than fish, it would suggest that human thyroids can withstand more iodine-131 than a fish thyroid. But this is extrapolation, and might well be wrong. I'm certainly not a biologist. But the fact Helen hasn't provided any references to studies on this subject is telling.

Helen's next paragraph is:

Nuclear industry proponents often assert that low doses of radiation (e.g. below 100mSV) produce no ill effects and are therefore safe. But, as the US National Academy of Sciences BEIR VII report has concluded, no dose of radiation is safe, however small, including background radiation; exposure is cumulative and adds to an individual's risk of developing cancer.

The report mentioned there would cost me $70 to buy, and I'm not going to do that. Yes, being alive on Earth carries the risk of dying from cancer caused by naturally occurring radiation. I'm not sure it's possible to do much about that. If the risks were significant then a) life would probably have not developed at all on earth; and b) all the perv-scanners that they're installing at airports which use ionising radiation (X-rays) would likely be banned because they'd increase the risk of cancer. The only thing that is of interest is: given the rate at which illnesses occur without exposure to additional forms of radiation, how much additional radiation is necessary before any of those illnesses become statistically more likely to occur? It is clear that the report she references here is not setting out to answer that question.

In Helen's third paragraph, she compares the 2005 World Health Organisation report on Chernobyl (which states 43 people died directly from the disaster, and about 4000 developed cancers caused by radiation released from the reactor), with the widely discredited report in 2009 which claims 980,000 deaths can be attributed to Chernobyl. This later report is published by the Annals of the New York Academy of Sciences, but as George discovered:

'A devastating review in the journal Radiation Protection Dosimetry points out that the book achieves this figure by the remarkable method of assuming that all increased deaths from a wide range of diseases – including many which have no known association with radiation – were caused by the Chernobyl accident. There is no basis for this assumption, not least because screening in many countries improved dramatically after the disaster and, since 1986, there have been massive changes in the former eastern bloc. The study makes no attempt to correlate exposure to radiation with the incidence of disease.

'Its publication seems to have arisen from a confusion about whether Annals was a book publisher or a scientific journal. The academy has given me this statement: "In no sense did Annals of the New York Academy of Sciences or the New York Academy of Sciences commission this work; nor by its publication do we intend to independently validate the claims made in the translation or in the original publications cited in the work. The translated volume has not been peer reviewed by the New York Academy of Sciences, or by anyone else."'

Helen then tries to suggest that pointing out these flaws in the work is "shameful". Quite why that is shameful, but claiming deaths due to disease that have no known association with radiation exposure have nevertheless been caused by Chernobyl isn't shameful, is beyond me. She finishes by claiming the World Health Organisation is an advocate for the nuclear industry.

Nuclear submarines are very common: at least the USA, British, French and Russians operate submarines which have nuclear reactors within them. In the confined spaces of nuclear submarines, many hundreds of mariners are in much closer proximity to a nuclear power-station than any of us are ever likely to be. Should not the incidence rate of cancer (or other diseases that can be caused by long-term exposure to elevated levels of radiation) be much higher than of the general population? Sadly, studies of this area are few and if data is collected on this subject by the various navies, then it's difficult to imagine them releasing the data. However one report looking at the illnesses suffered over a 13-year period by various crews on board nuclear submarines suggest the majority of issues are dermatological and musculoskeletal with the most common serious issue being acute appendicitis. It is a shame there seem to be no studies I can find that look at causes of death amongst mariners who spent time on board nuclear submarines.

As with most complex subjects, the public on the whole is ill-equipped to understand the likely impact of an event such as Fukushima, and people with vested interests will try to bamboozle by only presenting a very choice set of papers and reports to support their arguments. The public must be able to trust neutral and diligent reporters in the media to present the truth: with something as well understood as nuclear physics, this is not an area where opinion or debate is of much worth: there are hard facts which are easily understood but have been seldom seen in print regarding the actual dosages of radiation that are considered "safe" (and these are several hundred times higher than naturally occurring background radiation).

If I die two years earlier that I would have otherwise, due to cancer caused by increased radiation as a result of nuclear bomb tests carried out in the 1960s and 1970s, before I was born, a) how will I know that's what caused it? b) how will I know I wouldn't have died the next day anyway when crossing the road? and c) will I really care anyway? I'll finish with one further interesting fact: in 2007, 7.075 billion short tons of coal were burnt on Earth. In America alone, 134,000 people are employed mining coal, of which about 30 die every year in mining related accidents (compared to 8000 deaths a year in coal mines in China). Nuclear power stations are mainly fuelled by uranium, which also has to be mined. The worldwide production of uranium in 2009 amounted to 50,572 tonnes. Every year, which form of energy causes more deaths: coal, or nuclear?


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