ENISS- Comment
ICRP Draft Report for Consultation: The Use of Effective Dose as a Radiological Protection Quantity
“The concept of ‘effective dose’ (E) was developed by ICRP as a risk-adjusted dosimetric quantity for the management of protection against stochastic effects, principally cancer, enabling comparison of planned or received doses with dose limits, dose constraints, and reference levels expressed in the same quantity. Its use allows all radiation exposures from external and internal sources to be considered together and summed, relying on the assumptions of a linear-non-threshold dose-response relationship, equivalence of acute and chronic exposures at low doses or low dose rates, and equivalence of external and internal exposures.”
So far, so good. The ambition to find a quantity which comprises all radiation effects in one number had a very practical meaning in the practice of radiation protection. But from the very beginning it was known that this quantity is not measurable and has its purpose only for overriding aspects of regulating radiation protection. And it served for that purpose now for decades very well.
“Considering exposures incurred by patients during medical procedures, E is of practical value for comparing: doses from different diagnostic examinations and interventional procedures; the use of similar technologies and procedures in different hospitals and countries; and the use of different technologies for the same medical examination, provided that the representative patients or patient populations for which the effective doses are derived are similar with regard to age and sex. As stated in the 2007 Recommendations (ICRP, 2007a), “… risk assessment for medical diagnosis and treatment … is best evaluated using appropriate risk values for the individual tissues at risk and for the age and sex distribution of the individuals undergoing the medical procedures”.
Even in the medical field E was of value. It was also quite clear that E was not the appropriate quantity for planning and doing radiation therapy. In this field the absorbed dose in Gy was always the right quantity. So good, so far.
“Publication 103 (ICRP, 2007a) provides detailed explanation of the purpose and use of E and of equivalent dose to individual organs and tissues. However, questions have arisen regarding practical applications, highlighting a clear need for further guidance on specific aspects. This publication draws on the explanations provided in Publication 103 and emphasises that E has proved a valuable and robust quantity for use in the optimisation of protection, to set dose criteria and verify compliance.”
This statement can only be endorsed. The results are seen everywhere worldwide in a reduction of occupational exposures.
“Conclusions are drawn that: a) Equivalent dose (H) is not required as a protection quantity.”
This statement of ICRP is astonishing having in mind that the Equivalent dose has been part of the radiation protection practise for decades with the international result that we now have the safest radiation protection conditions ever, worldwide, in terms of exposure. From a scientific point of view this statement might be acceptable, but not from the point of practical radiation protection.
“It will be more appropriate for limits for the avoidance of tissue reactions for the hands and feet, lens of the eye, and skin, to be set in terms of absorbed dose (Gy) rather than equivalent dose (Sv).”
This statement might be scientific correct but it lacks any sensitivity regarding its implication for the radiation protection practice. Provided the whole world would follow this direction a tremendous amount of workforce would be distracted from the really important things, unnecessary, wasted work and costs would be the result to change all the regulatory framework and the licenses and the working procedures and the measurement procedures and, and, and. But what for? To satisfy the will of some scientists? There will be no gain in safety, nothing, not a little thing.
And this is what ICRP in the last years did not enough (or not at all?) recognise: the consequences of its doing. ICRP focusses too much on science and does not care enough about the consequences taking into account the very high standing of ICRP within the world of regulators. And this needs to be changed. Recommendations have been issued about the risk on Radon and the dose limit for the lens of the eye that had and will have significant consequences. And the criterion for the reduction of the limit for the lens of the eye was not even a scientific one. It was pure arbitrariness.
ICRP needs to rethink its role and must avoid to recommend things which are nice but costly and without any gain for safety.