putting the record straight on CERRIE uncertainties

Committee Examining Radiation Risk of Internal Emitters (CERRIE)
Minority Report

Setting the record straight on CERRIE's uncertainties

Here is the text of a letter submitted to New Scientist after the draft CERRIE Majority Report was leaked to them in July 2004 - four months before publication - in an obvious attempt to upstage the dissenters.
New Scientist finally published a short version of the letter on 11th September 2004.

Sir,
As members of the Committee Examining Radiation Risks from Internal Emitters (CERRIE) we dissociate ourselves from the interpretation of the Committee's report embodied in the article "Plutonium cancer risk questioned" (New Scientist vol. 183 issue 2456 17 July 2004, page 12).
The draft report leaked to New Scientist is an anodyne and confusing document but it does at least identify that there are uncertainties at every stage of estimating risk. To pick out the statement that risks of plutonium and similar radionuclides inside the body could extend over at least an order of magnitude and then to suggest that this means "risk from exposure inside the body could be 10 times higher than is allowed for in calculating international safety limits" is a significant understatement. The uncertainties cannot be picked at random and their values have to be multiplied, not added.
CERRIE ascribes values to uncertainties due to variation in internal distribution and retention (these "extend over at least an order of magnitude") and to uncertainties in dose coefficients ("an order of magnitude or more" with three orders attributable to uncertainties over the chemical forms that might be ingested or inhaled). Uncertainty over the risk derived from the Japanese A bomb data was "agreed to cover an order of magnitude". That's at least three orders before we have to compound matters with the things CERRIE knows it doesn't know. There are uncertainties in environmental dispersion and intake; the report does not quantify them. On the vexed question of whether the external paradigm is at all relevant to internal exposures, where heterogeneity of energy deposition can be very great, the report says "... the actual concepts of absorbed dose become questionable and sometimes meaningless when considering interactions at the cellular and molecular levels." This factor is not quantified, nor are the uncertainties inherent in the relatively new discoveries of radiation induced genomic instability, the bystander effect and minisatellite mutation.
Faced with the vast range of uncertainty which results, we prefer to look at what is happening in the real world, and we see many signs of disease and death associated with low doses of internal radiation. The persistent 10-fold excess of childhood leukaemia in Seascale is merely the most notorious. The current radiation risk model fails to account for it by a factor of 300 or 400 and there is no credible alternative explanation. The sharp increase in infant leukaemia in several countries after Chernobyl has no confounding factors and again the current risk model fails to account for it by a factor of several hundred. This phenomenon is not explained by the CERRIE report in its present form.
Richard Bramhall, Low Level Radiation Campaign, The Knoll, Montpellier Park, Llandrindod Wells Powys LD1 5LW
bramhall@llrc.org (address for correspondence).

Chris Busby, Green Audit, Glyndale, Trinity Road, Aberystwyth SY23 1LU.


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