The Low Level Radiation Campaign

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Pollution v • d • e

Air pollution

Acid rain • Air Quality Index • Atmospheric dispersion modeling • Chlorofluorocarbon • Global dimming • Global warming • Haze • Indoor air quality • Ozone depletion • Particulate • Smog

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Actinides in the environment • Environmental radioactivity • Fission product • Nuclear fallout • Plutonium in the environment • Radiation poisoning • Radium in the environment • Uranium in the environment

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Related topics

Environmental Science • Natural environment

The Low Level Radiation Campaign is primarily focused on advancing the theory that there is a relationship between Low Levels of radiation and negative health effects. Although the primary focus is on ionising radiation, there have recently been studies on the possible negative health effects of non-ionising radiation.

An idea central to the claims made by the LLRC, is that the negative health effects of radiation have been considerably underestimated by official agencies. While LLRC maintains that the risks of external radiation dose are reasonably well described by the International Commission on Radiological Protection, the LLRC also maintains that the risk due to radioactive material uptake is underestimated. The LLRC theorizes that, in many circumstances, internal radiation is far more dangerous than predicted by the ICRP's models.

Studies endorsed by the LLRC relate to cancer induction on the cellular level caused by radioactive isotopes released by industries which use the radioactive material. The LLRC web site [5] contains a variety of articles on the subject.

The LLRC was started in 1993 under the aegis of the Green Party but in 1996 it became independent due to a grant from the Goldsmith Foundation. In 1999 it was registered by Companies House as a Company Limited by Guarantee.

Contents 1 Central thesis of the LLRC 1.1 The hot coal analogy 1.2 Is radiation dose meaningless? 2 Impact on interpretation of epidemiology 3 Scale of implied error in risk estimates 3.1 Childhood leukaemia 3.2 Infant leukaemia after Chernobyl 3.3 Cancer in Sweden after Chernobyl 3.4 An internal study 3.5 Chernobyl studies 3.5.1 LLRC view of "the TORCH report" on Chernobyl 4 Personnel 5 "Non-research" methods 5.1 Civil disobedience 5.1.1 Satire 5.1.2 Cartoons and lampoons 6 Criticism from other scientists 7 Disagreement with other greens 8 Microwaves and mobile phones 9 Radioactive marine pollution 9.1 Thesis 9.2 Comparison with the findings of other workers (environmental radiochemistry) 9.2.1 Natural background 9.2.2 Sea and river silt 9.3 Hot particles 10 Americium in smoke detectors 11 The Second Event theory 11.1 Split dose experiments 11.2 Dose-rate experiments 11.3 Timing as a crucial aspect of the Second Event theory 11.3.1 Examples of isotopes which undergo several decays 11.3.1.1 132Sn 11.3.1.2 90Sr 11.3.1.3 222Rn 11.4 Reactions to the theory by other scientists 11.4.1 Against 11.4.2 Neutral 11.4.3 For 11.5 Alpha emitters 11.5.1 A cheap detection technique 11.6 Preexposure to radiation with regards to acute health effects and other good effects 11.7 Cadmium poisoning as a model 12 External links 13 References

[edit] Central thesis of the LLRC

LLRC contends that radiation protection standards are fundamentally flawed based on two basic grounds. First is the idea that radiation dose is an average energy transfer into large volumes of undifferentiated body tissue separate from internal radiation sources and from the radioactive decay of unstable elements within the body. LLRC cites a number of authorities who have criticised this on conceptual grounds (see [6]).

Second, is the idea that estimates of health hazards are based primarily on the Life-Span Studies (LSS) of the health of people who survived exposure to acute external irradiation from the Atomic Bombs detonated on the Japanese cities of Hiroshima and Nagasaki during World War II. LLRC points out that the LSS suffers from a series of methodological flaws which include

• Selective recruitment of the study group, as the studies didn't begin until five years after the bombings. This has resulted in many early deaths being excluded wrongly from the study.

• Poor choice of the control group. The LLRC consider this a very serious flaw as the control group (a supposedly unexposed population) was drawn from the populations of the bombed cities, so that both the study group and control group were equally contaminated by activation products and fission products. For this reason the Life-Span Studies are held to be silent on the effects of fallout and informative only on the effects of acute instantaneous external irradiation by gamma-rays, X-rays and neutrons from the explosion of the bombs. The LLRC states that it is not scientifically valid to believe that the effects of high dose, high dose rate, acute external irradiation reliably predict the effects of low dose, low dose rate, chronic internal irradiation.

The official French radiation risk agency IRSN (Institut de Radioprotection et de Sûreté Nucléaire) and the [7] European Committee on Radiation Risk (ECRR) have given support to the point of view of the LLRC. The IRSN have reported (see [8], and English edition) that it is reasonable for the ECRR to have reservations about ICRP's recommendations on radiation risk, since ICRP bases its advice on the health effects of external radiation from atomic bombs. However, IRSN have stated that arguments of the ECRR are not convincing" and that the ECRR "are not using a strict and constant scientific approach. The main conclusion of the IRSN is that further research is required on a series of topics before a final conclusion can be made.

The LLRC's response, as stated in a number of public meetings including a mass lobby of the House of Commons, London in February 2007, is that the European Committee accepts that its approach is an approximation but that there is a pressing and present need for further and more strict regulation of radioactive releases. They argue that waiting for the results of research (which may take many years to perform) is not a reasonable option. The ECRR propose new weighting factors for immediate, interim use to compensate for the shortcomings of the ICRP approach. Below is shown a table in which the ICRP and ECRR risk factors are compared.

The key differences between the risk factors of the ICRP and the ECRR ^[1].

Outcome	ICRP risk factor per sievert	ECRR risk factor per sievert
Fatal cancer	0.05	0.10
Non-fatal cancer	0.10	0.20
Severe hereditary defect	0.013	0.026
Malformation after in utero exposure	Threshold of > 0.1 Gy	No threshold
Cancer after in utero exposure	0.20	0.40
Severe mental retardation after in utero exposure	0.40	0.80

[edit] The hot coal analogy

LLRC holds that on biological and radiological grounds internal contamination of body tissue by some types of radioactivity is inherently more dangerous than predicted on the basis of the Hiroshima and Nagasaki studies. According to the LLRC the reason for the discrepancy is that external irradiation is uniformly distributed on a macroscopic level, with all cells receiving the same amount of ionising energy, while many forms of radioactivity when inside the body deliver their energy exclusively to microscopic volumes of cells; some types of radioactive decay are heterogeneous even on the far smaller molecular level. LLRC's favourite analogy for this heterogeneity of energy distribution is that external irradiation is like a person sitting by a fire and warming himself. If the person were to reach into the fire to take a burning coal and eat it the local tissue effects would probably be fatal, even if a similar or smaller amount of energy had thereby been absorbed by the person's body.

[edit] Is radiation dose meaningless?

On such logic as the hot coal analogy LLRC holds that radiation dose is virtually meaningless in some circumstances. In support of this they cite ^[2] Chapter 2.1 paragraph 11 of the CERRIE Majority Report:

Indeed, the actual concepts of absorbed dose become questionable, and sometimes meaningless, when considering interactions at the cellular and molecular levels.

LLRC also cite IRSN

... it should be noted that the assessment of the risk induced by internal contaminations is associated with a number of uncertainties due to the lack of data in certain domains, the complexity of dosimetric calculations, and the quality of epidemiologic investigation data. In addition, various phenomena may complexify the assessment of doses and risks, or even totally mislead the interpretations. As an example, we can mention the heterogeneous distribution of radionuclides, the validity of weighting factors applied for calculating internal doses, the impact of the radionuclide speciation on their behavior, and the chemical toxicity of certain elements.

^[3]

LLRC also cites section 3.2. Summary of health effects caused by ionising radiation of the 2004 draft of the ICRP's latest Recommendations ^[4] and the 2003 Recommendations of the ECRR ^[5]

[edit] Impact on interpretation of epidemiology

LLRC states that, since official radiation risk agencies universally quantify risk in terms of average dose, there are many types of exposure for which official reassurances are highly questionable and that it is not tenable to assert that disease phenomena like the Seascale cluster of childhood leukaemia could not be caused by radiation on the grounds of low doses.

[edit] Scale of implied error in risk estimates

[edit] Childhood leukaemia

COMARE (the UK Government's advisory Committee on Medical Aspects of Radiation in the Environment) has reported ^[6] that, on the basis of data for leukaemia derived from study of the Japanese bomb survivors, doses from Sellafield were between 200 and 300 times too small to cause the number of cases observed in Seascale. LLRC states that this is not evidence that radiation did not cause the Seascale cluster, but evidence that the risk model is in error by a factor of 200 – 300.

[edit] Infant leukaemia after Chernobyl

LLRC also points to infant leukaemia after the Chernobyl accident ^[7] as unequivocal evidence of an error of two orders of magnitude in ICRP risk factors.

[edit] Cancer in Sweden after Chernobyl

LLRC states that there is a large amount of evidence of this nature Another study cited by LLRC is the Tondel et al. study of cancer in Sweden after Chernobyl ^[8]. According to the LLRC's publication Radioactive Times, this demonstrates an error in ICRP of between 125 and 600. LLRC states that the extra cancers which were registered in the 9 post-accident years 1988 to 1996 are at least 125 times the incidence predicted by ICRP on the basis of doses from Caesium in Sweden, which was measured and mapped in detail. This 125-fold figure is based on the assumption that the effect is transient and that there would be no excess after 1996. However, the lifetime follow-up of Hiroshima survivors shows a consistent upward trend and it is likely that the effect seen in Sweden is typical of the distribution of risks throughout life and that cancer incidence will continue to be higher than expected. According to LLRC's calculations this would imply a 600-fold error in ICRP’s modelling.

The official Swedish radiation protection institute, SSI, has criticised the Tondel study [9], rejecting any suggestion that it shows a cancer increase caused by or related to the Chernobyl fallout.

[edit] An internal study

A further example relating specifically to internal radiation is a published study of nuclear industry workers diagnosed with prostate cancer ^[9]. This shows a statistically significant and substantially increased risk of prostate cancer associated with internal contamination. Responding in the British Medical Journal^[10], UKAEA calculated that, if the internal radionuclides were causing the cancer, then internationally accepted risk factors were probably in error by more than 1000-fold.

[edit] Chernobyl studies

The LLRC web site has summaries [10] of Russian, Belarusian and Ukrainian studies since the Chernobyl disaster.

The Campaign is severely critical of the ICRP for failing to cite or discuss any epidemiological findings from Chernobyl affected territories. They refer to this [11] as systematic theft of the greatest opportunity the human race has ever had to study the health effects of a major reactor accident.

[edit] LLRC view of "the TORCH report" on Chernobyl

The LLRC condemns the TORCH report as a theoretical review of a small part of the evidence accrued in twenty years since the Chernobyl disaster [12]

[edit] Personnel

Christopher Busby

Dr. Christopher Busby is the principal scientific adviser to the Low Level Radiation Campaign. Dr. Busby is a Director of research consultancy Green Audit [13], a past member of CERRIE (the UK Government's Committee Examining Radiation Risks of Internal Emitters [14]) and the Ministry of Defence Depleted Uranium Oversight Board ([15]). He is Scientific Secretary of the European Committee on Radiation Risk [16]. His curriculum vitae can be viewed at [17].
He holds a PhD in Chemical physics issued by University of Kent {Canterbury on the topic of Raman spectroscopy at metal surfaces^{[11][12][13][14]}).
Dr. Busby has been interested in the relationship between radiation and human health since 1987.

Richard Bramhall

Richard Bramhall is a founder member of the Low Level Radiation Campaign and is its Company Secretary. He is a retired professional double bass player, originally trained at the Royal College of Music in London in the 1960s. He worked in many orchestras beginning with the Royal Opera House when he left the RCM in 1969, then the Royal Philharmonic Orchestra, and at various times the English Chamber Orchestra and the London Symphony Orchestra.
According to the Cerrie web site [18]he holds the view that he is an informed non-scientist with a considerable track record of reporting developments in the field of radiation protection to an actively interested constituency of policy makers, journalists and members of the public both in the UK and abroad. He has had many years experience of Stakeholder Dialogue in the United Kingdom, working with representatives of government, regulators, the nuclear industry and other non-government organisations on issues concerned with radioactive waste, contaminated land and contaminated materials.

Others

Since the Low Level Radiation Campaign is a company under UK law, the identities of the directors are in the public domain and can be seen on the Companies House website.
A number of people contribute to LLRC's work, as published in Radioactive Times and in the proceedings of various dialogues.

[edit] "Non-research" methods

[edit] Civil disobedience

Christopher Busby gave an annual South Place Ethical Society lecture in London in 1994 on non-violent direct action. He also argued the Green Party into embracing non-violent direct action in the same year as a legitimate political strategy. He has engaged in civil disobedience, for instance he organized the chain up at Trawsfynydd. This was an event where Chris Busby, together with a number of other protesters, chained himself to the gate to protest against the restart of the power reactors under conditions which Dr Busby and others considered to be unsafe. This chaining by a person of themselves to an object is a method of protest which has been used by suffragettes in the UK and by other groups including Bertrand Russell's Committee of 100. Dr. Busby was a prime mover in setting up a Green Committee of 100 in 1994. The last known action of the Green Committee of 100 was the invasion of the British Nuclear Energy Society's 1997 International Conference on Low Level Radiation and Health in Stratford (England). In this, Richard Bramhall, dressed and made-up as the Grim Reaper, chained himself to the podium while epidemiologist Sir Richard Doll was delivering a keynote address. Other activists distributed copies of Dr. Busby's book Wings of Death to delegates.

[edit] Satire

In contrast to nuclear / radiological organisations (such as the International Atomic Energy Agency and the ITU) LLRC regards itself as a campaigning organisation and uses modes of communication appropriate to that status. Richard Bramhall has described parts of the LLRC web site as satire. Another Wikipedia editor has identified the following three quotes, taken from the jargon buster of the LLRC [19].

Committee Examining Radiation Risks of Internal Emitters. An oppositional committee set up by the UK Environment Minister in 2001. Notable for caving into legalistic threats from Departmental lawyers right at the end of its two-and-a-half year deliberations.[20]

and

The LLRC also describes the ICRP as the Incestuous Cabal for Radioactive Pollution

and

The LLRC comments that the idea of Controllable Dose is "(the) ICRP's idea for allowing the nukes to pollute anybody and everybody with radioactivity up to an arbitrary threshold ".

[edit] Cartoons and lampoons

Other styles are cartoons, including a Teddy and Dolly series and Roger Radon penned by Chris Busby. A series by Richard Bramhall features a fictional detective called Sergeant Mercer and his sidekick Constable Joskin (see [21]). There are lampoons of poems such as Owen's Strange Meeting and of the Wombles' Song. Good King Roger is a fairy story about ICRP's 1999 proposal to abandon the concept of collective dose.

[edit] Criticism from other scientists

In 2002 it was claimed by David Cartwright (a spokesperson for the British Nuclear industry)[22] that Dr Busby runs his own anti-nuclear company and makes a living out of producing these anti-nuclear reports
In addition other scientists in the field have attempted to recreate the work of Busby and have been unable to do so,[23] which they claim implies that Chris Busby's hypothesis may be incorrect and even that data has been wrongly manipulated and that numerous methodological problems exist within Chris Busby's paper on the relationship between the proximity to the Irish Sea and cancer. Dr. Busby and his colleague Professor V. Howard have even suggested ^[15] that the paper cited above was based on an elementary error which inflated the base population [24]. However the reply to that letter [25]showed that this apparent error was in fact closer to reality of the LLRC data. This was was coded using an obsolete and inaccurately system, now superseded by postcodes and it can be shown that coders tended to allocate rural addresses to the nearest town. Sometimes they allocated them to locations miles away. So the cases actually came from a much wider area than the census wards listed by LLRC. They do not fit any census boundaries. In other words they were comparing proverbial "apples with oranges". COMARE (the UK advisory Committee on Medical Aspects of Radiation in the Environment) acknowledged the apparent error but unanimously supported the alternative findings based on individually post coded data which can accurately be related to census ward boundaries. Using these data no cluster can be found.[26]. In a presentation to COMARE Dr Busby's work has been shown to be fundamentally flawed [27].This is a feature of most of his work considered by COMARE (see relevant Statements). In fact Dr Busby has made numerous well documented statistical and data manipulation errors in this and similar work. From his own book he admits to using two versions of the Welsh leukaemia data one correct one and one incorrect one with twice the number of cases,which he used to publish his misleading and erroneous reports on the Irish Sea. Neither Dr Busby or Professor Howard have had any training in statistics or epidemiology. Dr Busby's curriculum vitae may not be what it appears to be at first sight [28]This lack of knowledge is apparent in tthe poor standard of their work. Dr Busby made elementary statistical errors in his own book which illustrate this deficiency (see comment on this 17/05/08) [29] The final conclusion of a government committee, which included LLRC members, and met at public expense over three years, was that there is not a shred of scientific evidence to support the LLRC theory [30]. As science progresses by rejecting such flawed theories, most scientists would by now have consigned it to the waste bin. LLRC however unable to contemplate that their theory is wrong have developed an over-elaborate and implausible explanation in the Pre-Copernican mould e.g. wheels within wheels[31].They explain the discrepances between the real data and that predicted by their theory by claiming the existence of a conspiracy by cancer registries to cover up data[32]. In the final analysis it is all a matter of personal belief - even if this is the radiobiological equivalent of a naive belief in a "Flat earth with turtles all the way down",[33], This would all be a hugely funny satirical joke (as Bramhall suggests above)if the parents of childhood patients had not been needlessly upset and cancer registries overloaded by investigation of these badly flawed studies.

[edit] Disagreement with other greens

The LLRC is in disagreement with a "Greenpeace consultant (named Pete Roche) who is quoted as having stated an important report written by the The Low Level Radiation Campaign was "...was not included [in the CERRIE final report] because it was not factually correct". The LLRC publicly invited Pete Roche to enter into a debate (December 2004), but according to the LLRC to date "Mr. Roche has never responded".[34]

[edit] Microwaves and mobile phones

In the past the LLRC has normally avoided the subject of non-ionizing radiations such as microwaves, Ultra-Violet, Infra-red and radio waves as it has considered itself to be an organisation which should deal with ionizing radiations. However in 2007 it has done some work on the subject of a proposed mobile phone transmitter (base station) which was proposed to be sited within a church in Aberystwyth(Wales).[35] This work consisted of an epidemiology study of human health using a health questionnaire, it was planned that a study before the equipment was installed would be followed by a second survey after the equipment had started operations but as the planning application for the equipment to Ceredigion District Council was withdrawn the study was terminated at an early stage.

This activity has continued[36] recently in the USA Chris Busby has been involved in a campaign against a phone tower which was to be established in a town.

[edit] Radioactive marine pollution

[edit] Thesis

One of the key areas LLRC is concerned with is releases of radioactivity to the world's seas. They claim ([37]) that increased risks of cancer and leukaemia near the Irish Sea are discernible in official statistics and they believe this provides evidence of a large error in conventional radiation risk estimates. Chris Busby, LLRC's main scientific adviser, has published a book on the subject. This book is full of defamatory rantings but devoid of any scientific content.(Wolves of Water, 2006).

It was reasoned years ago that if any form of waste was added to the sea that the substance would be diluted to a very low concentration which would not be able to pose a threat to humans (or other organisms).^{[citation needed]} Chris Busby argues that even if waste is added to the sea then it is likely to be reconcentrated by physical and biological processes and then pose a threat to humans and other organisms.^{[citation needed]} This reconcentration thesis is not totally new, other scientists who are unconnected to Busby have found that some radioisotopes can be reconcentrated.^{[citation needed]}

[edit] Comparison with the findings of other workers (environmental radiochemistry)

[edit] Natural background

As much of LLRC's work involves a discussion of the levels of radioactivity within the environment it is important to note that that radioactivity is present everywhere (and has been since the formation of the earth). According to the International Atomic Energy Agency, one kilogram of soil typically contains the following amounts of the following four natural radioisotopes 370 Bq ⁴⁰K (typical range 100-700 Bq), 25 Bq ²²⁶Ra (typical range 10-50 Bq), 25 Bq ²³⁸U (typical range 10-50 Bq) and 25 Bq ²³²Th (typical range 7-50 Bq).^[16] It is important to note that these values are average values and some soils may vary greatly from these norms.

LLRC's view is that comparisons with natural background are largely spurious [38], since nuclear technology has created novel isotopes such as Plutonium and Strontium-90 which have unique characteristics not found in nature. They also state [39] that technologies such as the use of uranium in weapons create relatively insoluble particles smaller than 5 micrometres which are not found in nature. It should be noted that very fine particles of clay minerals (5 to 0.1 µm)^[17] are often present in soil and because the K_d (for binding to clay) for many natural radioisotopes is high it is possible that fine particles of clay bearing radioisotopes could be found in soil (K_d values for clay Ra >1000, Th 90-10000, U 2-490000^[18]). The behaviour of uranium in soil depends on many factors (such as concentration of humic acids and redox conditions), when the uranium is mobile it is possible that uranium may leach out of soil minerals into the soil water where it will decay thus forming radium and thorium which can bind to the surfaces of soil particles.

[edit] Sea and river silt

It is well known that some plants are able to absorb and concentrate metals within their tissues (see hyperaccumulators for further detail) and it is known that iodine was first isolated from seaweed in France which suggests that seaweed is an iodine hyperaccumulator.

For instance a study on the radioactivity found in oysters found in the Irish Sea, these were found by gamma spectroscopy to contain the fission products ¹⁴¹Ce, ¹⁴⁴Ce, ¹⁰³Ru, ¹⁰⁶Ru, ¹³⁷Cs, ⁹⁵Zr and ⁹⁵Nb. In addition a zinc activation product (⁶⁵Zn) was found, this is thought to be due to the corrosion of magnox fuel cladding in cooling ponds.^[19] It is likely that the modern releases of all these isotopes from Windscale is smaller as the waste water is now routed via an ion exchange plant where the many of metal ions are removed from waste water using the Enhanced Actinide Removal Plant (EARP) and with faujasite (Zeolite X) in the Site Ion Exchange Efficient Plant (SIXEO).

For instance Busby quotes Garland et al. 1989 who reported the plutonium activity in Welsh inter tidal sediments which suggests that the closer a site is to Sellafield the higher the concentration of plutonium in the silt is. Some relationship cen be seen but the scatter of points is large (R² = 0.3683) if the data is fitted to an exponential line.

In order to keep the levels of plutonium which are at the lower end of the concentration rage in the above diagram in perspective it is important to note that all materials (such as soils and silts) contain some natural alpha emitters. For instance a recent report on the sava river in serbia suggests that many of the river silts contain about 100 Bq kg^-1 of natural radioisotopes (²²⁶Ra, ²³²Th and ²³⁸U).^[20] Also according to the United Nations the normal concentration of uranium in soil is 300 µg to 11.7 mg.^[21]

[edit] Hot particles

Busby in his book (Wolves of Water[40]) has written that hot particles (plutonium) have been found in the Irish Sea and that these particles are migrating onto the land,^[22]. It is interesting to note that the International Atomic Energy Agency report on Mururoa states on page 43 (chapter 4) that some particles containing 1 mg (100 kBq) of plutonium are present on the island that was used for French nuclear experiments.^[23] On page 220 it indicates that such a particle could deliver a dose of between 1 and 300 Gy per hour to a worm which lives in the silt. From an examination of the book by Busby it is likely that the hot particles which he has reported are smaller than those reported at Mururoa, but Busby suggests that official health statistics show the Irish Sea hot particles are causing effects in human populations along the coast.

[edit] Americium in smoke detectors

One article by Rose Tilly, which is reprinted[41] on the site, suggests that the gamma rays from the americium present in smoke detectors is a grave threat to the general public. She claims that a count rate of 500 events per second can be recorded near a smoke detector using a scintillation counter. The LLRC reply that they have repeated her measurements and have been unable to observe such a high radiation level, they have observed a smaller increase of radiation when a smoke detector is placed one inch away from a detector. They suggest that the smoke detectors used by Rose should be subjected to a more detailed radioanylsis to determine if the radioactive sources within them contain some additional radioisotopes. It is interesting to note that the article by Rose has a clear error which suggests other errors might be present in the article, this error is her assertion that americium is a fission product, americium is an activation product of plutonium and hence is very different from the fission products.

[edit] The Second Event theory

One of the major ideas presented in the LLRC web site is the hypothesis, first advanced by Chris Busby in his 1995 book Wings of Death ^[24], that radionuclides which decay sequentially may have an enhanced ability to cause heritable genetic defects.

[edit] Split dose experiments

In some 1970s experiments comparing the effects of a single X-ray exposure with two exposures at the same total dose it was observed that the transformation rate was increased by a factor of two when two 250mGy doses were administered (with a 7.5 hour time between the doses) compared with a single dose of 500 mGy.^[25][26][27] In Wings of Death Busby claims that these results support his Second Event hypothesis.

However no consensus has been reached regarding the question of "does exposure to radiation increase or decrease the radiosensitivity of cells?", it has been shown that for large doses of X-rays fractionation can induce radioresistance in tissue^[28], while it has been shown that preexposure to radiation (50 to 100 mGy) results in four hours time in a small reduction of the ability of a 8 Gy dose to damage DNA in intact cells due to a shift in the cell cycle^[29]

[edit] Dose-rate experiments

Mainstream science is divided on the question of does division of a radiation dose into smaller doses reduce or increase the likelihood of the induction of cancer. In a recent paper^[30] a dose of 1 Gy was delivered to the cells (at constant rate from a radioactive source) over a series of lengths of time. These were between 8.77 and 87.7 hours, the abstract stated for a dose delivered over 35 hours or more (low dose rate) no transformation of the cells occurred. Also for the 1 Gy dose delivered over 8.77 to 18.3 hours that the biological effect (neoplastic transformation) was about 1.5 times smaller than that which that had been observed using a single high dose rate of X-ray photons of similar energy. Likewise it has been reported that ^[31] that fractionation of gamma irradiation reduces the likelihood of a neoplastic transformation. It is clear that the findings in these two papers do not agree with the hypothesis of the second event theory. But in a further paper^[32] it is reported that for both fast neutron and gamma rays from Cs-137 that preexposure can increase the ability of a second dose to induce a neoplastic transformation.

[edit] Timing as a crucial aspect of the Second Event theory

As described in the CERRIE Majority Report

The second event theory (SET) is that two radiation hits (by electrons or alpha particles) in a cell within a particular time window greatly enhance mutagenic effectiveness and, by implication, cancer risk. The hypothesis suggests that the cancer risk from specific sequentially decaying radionuclides (such as Strontium 90 and its daughter Yttrium 90), and from particulate forms of plutonium, has been greatly underestimated.

The biological basis of the theory is that the first radiation hit (for example, from the initial beta decay of Strontium 90) activates a resting cell and causes it to move into what Dr. Busby terms a repair-replication cycle. According to the theory there would be a great enhancement in radiation effect if a second hit (for example, from the subsequent beta decay of the Strontium daughter Yttrium 90) were to impact the same cell some hours later when it is in a phase postulated to be >100 times more radiosensitive.

This part of the argument is based on experimental results with cell cultures demonstrating the postulated sensitive phase.^[33], ^[34]

It should be noted that radiation affects tissue in the form of discrete track of charged particles. As Professor Dudley Goodhead puts it

Insult from ionising radiation is always in the form of individual structured tracks. At the level of cells the possible responses are limited by the numbers and variety of these tracks and the time interval between them.^[35]

Also, it is important to be aware that the enhancement referred to in the theory concerns relative probabilities; the probability of two tracks (or events) affecting any target tissue from a sequential emitter, compared with the probability of two tracks from another type of exposure always assuming, for the sake of the comparison, that the dose from the sources is the same.

[edit] Examples of isotopes which undergo several decays

[edit] ¹³²Sn

The decay of ¹³²Sn and its decay products (daughters)

Element	Isotope	decay mode	half life (minutes)
Sn	132	β	40 seconds
Sb	132	β	2.8
Te	132	β	3.2 days
I	132	β	2.3
Xe	132	-	stable

The above table illustrates that not all steps in a decay chain are potential second events; here only the decay of Antimony to Tellurium results in a candidate. This is because only the Tellurium has a sufficiently long half-life to have much chance of providing the second decay at the critical point in the cell repair cycle. The others are too short. The above decay chain is only likely to be important for a consideration of nuclear warfare and serious nuclear accidents involving criticality (eg chernobyl) as the half lives of all the isotopes are relatively short (minutes and days). Also normal operating conditions in a power reactor it is likely to be the case that the antimony is unlikely to be released from the uranium dioxide fuel unless the fuel was badly damaged.

[edit] ⁹⁰Sr

The formation of ⁹⁰Sr and its decay products (daughters)

Element	Isotope	decay mode	half life	direct fission yield
Se	90	β	very short < 1 µs	0.0000%
Br	90	β	1.9 seconds	0.0000%
Kr	90	β	32.3 seconds	0.0178%
Rb	90	β	158 seconds	0.0794%
Sr	90	β	28.8 years	2.2416%
Y	90	β	64 hours	0.3309%
Zr	90	Stable	-	0.000%

Note that these fission yields were calculated for ²³⁵U assuming thermal neutrons (0.0253 eV) using data from the chart of the nuclides.[42]

[edit] ²²²Rn

It is noteworthy that in the decay chain of radium-226/radon-222 a large number of shortlived radioisotopes exist which could subject a cell to repeated radioactive events. This is because the daughters of radon often become attached to smoke and dust particles and are then able to lodge in the lungs.[43]

The decay of ²²²Rn and its decay products (daughters)

Element	Isotope	decay mode	half life (minutes)
Rn	222	α	3 days
Po	218	α	3.1
Pb	214	β	27
Bi	214	β	20
Po	214	α	0.164 seconds

[edit] Reactions to the theory by other scientists

[edit] Against

Busby's views are often seen as controversial. The NRPB published a counterblast against the second event theory in which they suggest that it is a theory which is unlikely to be correct.^[36] [44]. Busby in an open letter to the editor published a rebutal of this paper which can be read on line.^[37], this in turn resulted in the NRPB writing a letter of their own to the journal in which they rebut the rebuttal letter (Again this can be read on line).^[38]

The Committee Examining Radiation Risk of Internal Emitters (CERRIE) concluded in its Majority Report ^[39] that the available studies to date offered little or no support to the second event theory […] Instead the evidence substantially contradicted it. The Report found a lack of biological plausibility for the basic preconditions of the SET; a lack of supporting evidence in the proponents’ reviews of the SET; weakness in the few studies cited in support of the SET; and absence of supporting evidence from experimental studies in an independent review of commissioned by the Committee.

[edit] Neutral

Speaking at a 1996 Symposium in the House of Commons, London, Professor Dudley Goodhead of the Medical Research Council said the theory was nicely specified and open, by its nature, to a variety of experimental tests.^[40] He added that he and his colleagues would be happy to discuss ways in which it could be tested. Another issue, he said, was that if the hypothesis were to be valid

... it would have significant applications not only for artificial radionuclides from the nuclear industry but also for external radiations in occupational situations, because there would be quite a number of situations where [there would be] two tracks [to a cell], by virtue of the diagnostic radionuclide used, or an X-ray examination, or the occupational exposure; where people might be exposed successively over a period of hours — ten hours or so …^[41]

However this should not be understood as an endorsement of the theory as it does not comment on the question of is the theory correct or incorrect. It is simple to understand that other theories (if correct) would have far reaching effects upon our understanding and experience of life.

[edit] For

The Minority Report ^[42] answers the CERRIE majority report by arguing that the SET's critics on the Committee, who had conducted a theoretical analysis of the theory (which is not reported in the Majority Report) had misunderstood the significance of the doses needed to move a cell out of quiescence. They further argued that the critics had used wrong data for cell packing and inappropriate dose criteria. When these errors were corrected there were enhancements of hazard. The Minority Report also states that the Committee had accepted that a 1 micrometre plutonium particle would give a track rate so high that each cell within range of the decays would receive a second event in a year. According to the Minority Report, this inevitably meant that there is a particle size which would provide second events at very high efficiency at doses too small to kill the cells. A study presented to the Committee but not reported by it showed synthetic beta-emitting particles in mice produced more mutation than alpha-emitting particles, contrary to ICRP expectations based on Relative Biological Effectiveness. The Minority Report states

These results suggest that the higher flux of events in the beta-emitting particles were more carcinogenic than the lower flux of events in the alpha-emitting particles

The CERRIE Minority Report states, contrary to the Majority Report, that the review of Strontium-90 studies which the Committee commissioned to investigate the plausibility of the Second Event theory did find studies compatible with the theory, as well as some that were incompatible with it. "In addition", the Minority Report says, "the review left out some studies which showed such effects."

[edit] Alpha emitters

The published work of Chris Busby includes an assertion that a hot particle of ²³⁹Pu is able to subject the biologcal tissues to a series of alpha particles. He suggests that this is one of the reasons why hot particles are able to cause health effects. In the CERRIE Minority Report (page 68) he writes:

... the Committee accepted that a plutonium particle of 1 micrometre would give a track rate so great that each cell in range of the decays would receive a second event in a year. But this, it was argued, would cause cell killing so there would be no transformation. If both these arguments are taken as true, it must follow that somewhere in between natural background dose and the 1 micrometre particle there is a window for very high efficiency second events which are also at a low enough dose not to kill the cells. This could be from smaller Plutonium particles or from warm particles of another, less active, isotope. Indeed, if hot particles are conceded to cause cell killing then the fact that they produce effects similar to the equivalent external dose must mean that the non-cell killing radiation they emit is, for some reason, very much more mutagenic than low density ionisation.

[edit] A cheap detection technique

For people who are interested in testing environmental samples for the presence of alpha emitting substances such as Plutonium and Uranium LLRC advises a method based on plastic sheet [45]. This is widely used for the measurement of radon gas and other alpha emitters. CR39, a plastic sheet which is damaged by the action of alpha particles, is exposed to the samples and then etched with sodium hydroxide (a strong base). It is examined by optical microscopy. The methodology is inexpensive and robust and can be used by citizen groups.

[edit] Preexposure to radiation with regards to acute health effects and other good effects

Some studies have suggested that preexposure to radiation exerts a protective effect upon cells ^[43] and whole animals^[44]. In mice it has been shown that a 200 mGy X-ray dose protects mice against both further X-ray exposure and ozone gas.^[45] Furthermore it has been shown in a rodent study that low level (1 mGy hr^-1) gamma irradiation prevents the development of cancer (induced by chemical means, injection of methylcholanthrene).^[46] Also it has been shown that irradiation with gamma rays increases the concentration of glutathione (an antioxidant) found within cells, this is likely to lead to an adaptive response.^[47]

While it is clear that a large single exposure to plutonium dioxide powder is able to cause a fatal lung cancer in monkeys (and thus it is likely that PuO₂ powder is carcinogenic in humans),^[48] some studies have shown that moderate internal exposure to plutonium results in a reduction of the risk of getting cancer,^[49]. Other studied have suggested that a small dose of radiation may be good for you.^[50] However one explanation for this effect is the fact that the majority of radiation workers are subject to greater number of health checks than the general population, and thus as a result any sign of disease is more likely to be seen at an early (curable) stage. Also see the "healthy worker hypothesis". In plants radiation hormesis has been observed^[51] However the existence of radiation hormesis in humans has been questioned, it is reasonable to state that for late effects (such as cancer) that the scientific community has not come to an agreement regarding this matter.[46] But in one recent case it was claimed (In Journal of American Physicians and Surgeons) that the persons living in a apartment block in Taiwan which was constructed using concrete which contained rebar contaminated with cobalt-60 experience a better state of health than the average person.^[52]

[edit] Cadmium poisoning as a model

It is known that many toxic metals can induce oxidative stress in tissue which may result in free radical induced damage. Also it is known that prior exposure to a small dose of cadmium can mitigate the effects of a second larger dose, this suggests that the first lower dose of the poison stimulates the DNA repair processes in the exposed tissue.^{[53][54][55][56]}

[edit] External links

• The Low Level Radiation Campaign
• The European Committee on Radiation Risk

[edit] References