Response to IRSN

The Institut de Radioprotection et de Surete Nucleaire has issued a report(1) on the Committee’s 2003 Recommendations. Here we present the Committee’s initial response.


The French IRSN report, published on 9th Dec 05 is the culmination of its study of the arguments and recommendations contained in the ECRR2003 report (2). These arguments were also presented to the UK’s Committee Examining Radiation Risks of Internal Emitters (CERRIE) between 2001 and 2004, to the UK Ministry of Defence Depleted Uranium Oversight Board, to the Royal Society Depleted Uranium Committee (2001-2002) and in addition have been the subject of many conference presentations and reports and books from Green Audit since 1995.

Since the IRSN is an organ of the French State, the new IRSN report represents a sea change in official thinking on the matter of the security of the risk models of the International Commission on Radiological Protection (ICRP) as applied to chronic internal radionuclide exposure at low doses.

The IRSN report was the result of two years research by a committee of 15 senior radioprotection experts collected together with the express purpose of examining the arguments and claims made in ECRR2003. This research was aimed at the scientific content of ECRR 2003 and left aside examination of its philosophical and ethical chapters. The IRSN report begins in its preface by agreeing that the questions posed by the ECRR are

valid and deserve a debate

and that the ECRR have raised

fundamental questions with regard to radioprotection.

It begins by contrasting the approaches of the ICRP and the ECRR to radioprotection and agrees that for certain internal exposures the approach of the ICRP is strictly invalid, citing (p6)

heterogeneous distribution of radionuclides, the validity of weighting factors applied for calculating internal doses, the impact of the radionuclide speciation on their behaviour and their chemical toxicity.

Apart from the matter of chemical toxicity (which except for uranium is not an issue) these are all aspects of the issue questioned also in ECRR2003. They further specify issues that are raised by ECRR (p7) and agree that they are valid and need addressing. These include the pertinence of the use of the external Hiroshima based risk factors, the lack of direct epidemiology of internal chronic exposures and the problems of the new scientific discoveries which ECRR and the CERRIE Minority Report (3) state falsify the ICRP model. The IRSN report tentatively agrees, stating (p7)

since the ICRP60 publication, improvements in radiobiology and radiopathology or even general biology finally might impair[falsify] the radiation cell and tissue response model applied to justify radioprotection recommendations.

The IRSN report criticises the ECRR report for what it categorises as many inaccuracies, unsupported statements and various types of errors. Many of these criticisms are accepted in part: they result from the ECRR Committee members’ need to develop a pragmatic system that could be used for radioprotection purposes here and now. The ECRR2003 report conceded the levels of approximation that had to be incorporated and in particular the fact that any useful system would have to deal with historic data calculated on the basis of the original ICRP model. IRSN state that they believe it’s

unacceptable to state (as ECRR do) that the linear no threshold model is patently not true and then go ahead and use it for risk assessments.

The ECRR takes this occasion to repeat and emphasise that its approach was and remains pragmatic, given that (1) the system had to use historic dose data and (2) the necessary knowledge of internal radionuclide dose distribution was not yet available. IRSN attempt to show (p8-9, p12-14) that there is inconsistency in the application of this system when applied to Belarus, but their example appears to be invalid since they use ECRR risk factors for infant deaths and apply them to cancer incidence.

Much of their criticism of the model developed by ECRR to overcome the shortcomings of the ICRP is based on IRSN’s belief that the ECRR’s new biophysical and biological weighting factors are conceptually insecure as they involve a mixture of epidemiological and purely physicochemical parameters. There is some validity in this argument, but again, the system was advanced as a practical response to the problem. IRSN themselves advocate the other approach considered and rejected by ECRR, that of attempting to base such weightings on hard data. ECRR argued that such data did not exist and on the basis of its precautionary approach needed to develop a workable model; it should be noted that the ECRR 2003 volume is subtitled “Regulators’ Edition”. It was also arguable that data to substantiate the weightings could never be obtained in a way that would enable a perfectly rational system to be developed. Nevertheless, ECRR did argue for research to be urgently carried out to obtain such data. IRSN has now supported that call.

The problem with human exposure epidemiology (which IRSN agree) is that of negotiating the various components of hazard when there are exposures to mixtures of isotopes (e.g. weapons fallout/ Chernobyl). The ERCC hazard weightings are obtained from mixtures of differential contamination epidemiology and biophysical considerations.

On p16, IRSN agree with ECRR that the ICRP reasoning on averaging dose

may be criticised as we are now aware that numerous radionuclides are highly heterogeneously distributed among all tissues They continue: The ECRR considers that particle concentrations in tissues, locally generating high radiation doses, are more carcinogenic than when the same amount of energy is uniformly deposited in tissues. A set of studies, basically conducted in in vitro systems, appears to confirm this assumption.

The IRSN report goes on to examine many areas where the ECRR has called into question the risk models of the ICRP and agrees that the questions are valid and may have resulted in the misapplication of risk analysis, citing Chernobyl as an example. IRSN agrees that other end points apart from cancer should be considered as outcomes of chronic internal exposure and cites the discoveries of Bandashevsky regarding childhood cardiac and other pathologies. IRSN continues with its own discussion of chronic internal exposures, pointing out that for some isotopes, particularly uranium, chronic internal exposure carries greater harm, dose for dose, than acute internal exposure.

In summary, the IRSN report is a pretty complete validation of the things members of the Committee have been saying for many years about internal irradiation. Its only divergence is in its disagreement with the way the Committee has dealt with the issue, which IRSN sees as rather ad hoc and insecure. We reply that the semi-empirical epidemiology/ biochemistry approach was predicated on our need to provide some system of modelling in the absence of any other secure system and to draw attention to the total insecurity of the ICRP approach.

C. Busby
Scientific Secretary, European Committee on Radiation Risk


References

1 DRPH/2005-20: Health consequences of chronic internal contamination by radionuclides. Comments on the ECRR report “The health effects of ionising radiation exposure at low doses for radiation protection purposes” and IRSN recommendations. Downloadable on this site (in pdf format).

Française (1.4 Mb) English (1.2 Mb)

2 2003 Recommendations of the ECRR: The Health Effects of Ionising Radiation Exposure at Low Doses and Low Dose Rates for Radiation Protection Purposes: Regulators’ Edition. Edited by Chris Busby with Rosalie Bertell, Inge Schmitz-Feuerhake, Molly Scott Cato and Alexei Yablokov. Published on Behalf of the European Committee on Radiation Risk/ Comité Européen sur le Risque de l’Irradiation, Brussels by Green Audit, 2003. ISBN: 1 897761 24 4

3 CERRIE MINORITY REPORT; Minority Report of the UK Department of Health / Department of Environment (DEFRA) Committee Examining Radiation Risks of Internal Emitters (CERRIE); with additional material. Richard Bramhall (CERRIE member), Chris Busby (CERRIE member), Paul Dorfman (CERRIE Secretariat).
Introduction by Michael Meacher MP. Sosiumi Press Aberystwyth. ISBN 0-9543081-1-5
External link: http://www.llrc.org


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