Dose Coefficients for External Exposures to Environmental Sources

Draft document: Dose Coefficients for External Exposures to Environmental Sources
Submitted by TADA, Jun Ichiro, N. P. O. Radiation Safety Forum
Commenting as an individual

  • Although the sophisticated age- and gender-dependent phantoms would be fine technological achievement and the procedure for evaluating their tissue and organ absorbed doses, except for standing new-borns, seems to be reasonable, this report is absolutely nonsense.
  • Since advances in a system can be achieved only by balanced improvement throughout the entire system, the same is necessary for advancing the system of dose used for radiological protection. The age- and gender-dependent effective doses intended to be introduced in this report use tissue and organ absorbed doses derived from sophisticated age- and gender-dependent phantoms, while keeping age- and gender-averaged tissue weighting factors as before. Cancer induction risk in tissues and organs from exposure to low level ionising radiation, however, varies significantly with age and are different between genders, and the age-dependency differs among tissues and organs. Therefore, the procedure assessing age- and gender-dependent effective doses in this report is completely out of balance and provides a deceptive fake accuracy.
  • It is essential to show the expected improvements in the system of radiological protection when a new dose assessment procedure is going to be introduced. However, even with age- and gender-dependent tissue weighting factors, the merit for radiological protection of showing the difference between child and adult doses is unclear. In the case of people living in the affected areas of the Fukushima Daiichi nuclear power plant accident, the knowledge of an approximately 50 % larger dose estimate for children cannot provide any practical improvement in their radiological protection strategy since their annual dose levels are far below those that necessitate radiological protection intervention.
  • Four “expected applications” of the age- and gender-dependent effective dose coefficients for external exposures to environmental sources are shown in the report, but none of them necessitate age- and gender-dependency when assessing effective dose.
  • Based on seven years of experience in assisting people living in the area affected by the Fukushima Daiichi nuclear power plant accident, it should be emphasised that focusing on possible insignificant underestimation of children’s dose could cause devastating effects to the lives of residents; as mothers having small children or expecting babies become more reluctant to stay, and conflict of opinion in the family and unnecessary relocation (sometimes only the mother and children) brings mental and economic damage that may cause disruption of the family in extreme case.
  • While the “possible risk” of the stochastic effects assessed by the LNT model are already small in the valid dose range of effective dose, i.e. below 100 mSv, and while the stochastic effects at low doses is no more than a virtual health effects used for designing radiological protection practices, it is by no means useful to discuss the even smaller dose differences between the standard child and adult. It should be kept in mind that most members of the public are prone to misunderstand that stochastic effects at low doses are actual harm awaiting those exposed just like deterministic effects. Being naked and taking unnatural posture of the phantom in the simulation are not an acceptable excuse that the estimated age- and gender-dependent effective dose do not reflect actual exposures of individual (as written in lines 2201~2204) since the dose coefficients in this report on the other hand pursued "reality."
  • In my understanding, the principal role of the ICRP is to establish the philosophical basis and fundamental concepts for radiological protection, and protection technologies should comply with the philosophy and concepts. No matter how brilliant the technology would be, it is outrageous if the ICRP were to shake its radiological protection philosophy and concepts by being dazzled by technology.
  • Neglecting insignificant detail in the assessment of protection dose should have been the wisdom of the ICRP when it re-defined effective dose as an artificial human dose for the tool of optimisation in the 2007 Recommendations, based on the bitter experience of prevailing inadequate use of effective dose such as predicting future cancer risk. The idea of using effective dose as an indicator of possible risk of radiation exposure for a communication tool is contrary to the wisdom.
  • A heavily contaminated environment with radionuclides that may cause tissue reaction such as the consequences of a nuclear terrorist attack is the situation beyond the application of effective dose, but the triage and treatment of victims should be conducted with suitably estimated tissue and organ absorbed doses. The effort expended for obtaining age- and gender-dependent tissue and organ absorbed doses by Task Group 90 will be duly utilised for such purposes.