Submitted on behalf of David Pawel, Julian Preston and myself:
We would like to express our appreciation to the ICRP for providing the opportunity for public consultation on the excellent Task Group 102 report and for providing more transparency regarding the process used to define radiation detriment. The use of the detriment concept, particularly for defining tissue weighting factors, has allowed for notable refinements in the evolving definition of effective dose. Effective dose is, arguably, an appropriate quantity for managing the radiation exposures of adult workers and estimations of radiation detriment are essential for its calculation. For management of chronic radiation exposures of populations, especially in situations where special populations such as pregnant women and children are a concern, we believe that the tools for calculating age- and sex-specific excess cancer risks (and the integral, age-averaged population risk) are already available and provide a less subjective approach for managing detriment.
This concern is highlighted in lines 182-186, of the report “(e) The calculation of radiation detriment is based on a weighting procedure in which nominal cancer risks are adjusted by three parameters reflecting lethality, quality of life and years of life lost. These three parameters are independent of radiation dose. Their determination is partly based on expert judgement, and the values used do not consider differences with age, sex, or between populations.” This approach is fraught with uncertainty which is inherent in the detriment values obtained. The sensitivity analysis emphasizes this. Section 5.2. (Variation with sex and age) seems to acknowledge the problems with applying one set of tissue weighting factors across sexes and age groups. We suggest that, in the future, consideration be given to adopting a simpler definition for detriment (e.g., detriment equal to the average of morbidity and mortality lifetime attributable risks). There would appear to be little overall value to the adjustments associated with lethality, quality of life, and years of life lost, when: 1) for most cancers the adjustments ultimately have limited effect on tissue weight; 2) the adjustments are based on data that do not reflect recent/future improvements in treatment; and 3) tissue weights are obtained only after rounding of “precise” tissue-specific detriment calculations. A simpler detriment formulation would be consistent with risk communication principles (e.g., one that all radiation protection professionals could remember).
Whether through refinements to the application of weighting factors or by directly applying excess cancer risk estimates in the management of population exposures, we encourage the “future evolution and possible ways of improvement” in the detriment methodology that is part of Committee 1’s current program of work. Thank you again for the opportunity to provide these comments, which are independent from and do not necessarily reflect the views of our employer, the U.S. Environmental Protection Agency.
David Pawel
Julian Preston
Michael Boyd