|Comments on 2005 ICRP Recommendations Draft
César F. Arias, University of Buenos Aires
(In these comments p. means paragraph)
Style and philosophy
The 2005 Recommendations draft shows a different style of presentation and a slightly different vocabulary when compared with ICRP 60. However the philosophy is essentially quite similar and its practical application will probably not introduce significant changes in everyday radiation protection.
The draft has the declared intention of making the System “more coherent and comprehensible… and more transparent” (p. 6). However the draft may still needs some revisions to attain such remarkable proposal.
An interesting characteristic of this draft consist on the attempt to derive every possible real situation of radiation protection from a general conceptual frame. Protection of workers and members of the public in normal, existing and emergency exposures are presented as particular aspects of a general scheme of “need for action” (Fig. 5).
This sort of holistic approach is notable ambitious. However the use of the same words for every combination of people, kind of exposures and circumstances might not help to easily realize the great differences in attitudes and procedures to be adopted in so different situations. In particular, the persistent use of the expression “Dose Constraint” as a concept applicable to every situation may introduce some confusion. This comment seems to be particularly pertinent due to the apparent reluctance of present draft to explicitly keep the distinction between “practices” and “situations that require intervention” introduced by ICRP 60. The word “intervention” is mentioned only in p. 197 and in Fig. 4.
Attitudes to keep normal situations as normal, confronting doses and risks against the pertinent dose and risk constraints are quite different from attitudes that must be adopted to reduce exposures and risks created by emergency situations or from preexisting exposures taking the proper action levels as reference for actions. In the first case the situations are “constrained” to keep the characteristics of normal situations. In the second one the situation can not be immediately controlled and exceptional intervention measures must be adopted to reduce exposures and risks according to some “reference levels” or “action levels”.
Therefore while “Dose constrain” is a good expression for normal situations “Action Levels” would be a more understandable expression to apply in emergencies and preexisting exposures.
An ethical difference?
Ethical different positions are suggested between an “utilitarian approach” attributed to ICRP 60 and present draft that would be more focused on protection of individuals (p. 6). It does not seem to be a real dilemma. ICRP 60 has enhanced the significance of individual protection far beyond the protection warranted through limits and constrains by stressing the requirement of optimizing radiation protection. Social considerations have been taken into account to find the reasonable level of risk reduction beyond dose limits or dose constrains. Along last decades this System has lead to protection of individuals much beyond the protection warranted by individual dose limits as it is explicitly recognized in paragraph 156.
Justification of practices as a concept should not be out of ICRP recommendations despite who is in charge of analyzing its application (paragraph 18). Not only justification but every aspect of ICRP recommendations will be responsibility of governments and especial agencies. It does not seem to be an argument to exclude justification as a concept from ICRP recommendations.
The question is: Every source of radiation cause or may cause some detriment to people. The only way of completely avoid such detriment would be to forbid their use. There must be a good reason to allow them, and this is justification. For the same reason ICRP has stressed the significance of optimizing radiation protection. It is not expected that ICRP develop procedures to formalize justification criteria in particular circumstances but such concepts should not be outside the core of the recommendations of the main international organization on radiation protection.
How to keep the particular application of the justification criteria in medicine if the concept itself is no retained in general recommendations?
Is optimization broader now?
It is suggested that optimization is conceptually broader now (p. 189) because it includes “the avoidance of accidents and other potential exposures”. Optimization as explained in ICRP 60 means the reduction of doses, number of exposed people and “the likelihood of incurring exposures were these are not certain to be received” that is potential exposures. Therefore safety culture was implicit in optimization conception since then.
Medical exposure. Characterization and potential exposures.
The chapter devoted to medical exposure should start (p. 213) with a description of what can be considered the main characteristic of medical exposure from the radiation protection point of view as follows:
“Medical exposure (patient exposure) is the only practice with radiation sources were persons (patients) have to be deliberately exposed to obtain a benefit. Exposure is necessary in order to benefit the persons exposed by obtaining tissue information (Diagnosis and Interventional Radiology) or by inducing tissue modifications (Theraphy). Besides this necessary exposure patient may be exposed to additional exposures, in the same or different tissues, that are not strictly necessary but that may be difficult or impossible to avoid completely, depending on equipment and techniques employed. They are unnecessary exposures”.
New ICRP Recommendations should point out the relevance of reducing the probability of potential exposures in medicine, that is, unexpected overexposures and underexposures of patients. Very severe accidents have occurred by delivering wrong exposures to patients.
Table of contents
The chapter devoted to Potential Exposures is a very significant and broad component of the basic radiation protection system. Its concepts must be applied to every situation were radiation protection should be considered. Potential Exposures should be presented before Medical Exposure in the Recommendations, since medical exposure is a particular aspect of radiation protection where potential exposures must also be considered.
p. 15) The identification of “controllable exposure and controllable source” may be confusing. To say that in a severe accident (Chernobyl for instance) the source is controllable because people can be evacuated may be misleading.
Exposures in emergency situations can be controlled through exceptional actions in the pathways. But the source itself usually can not be controlled at least immediately.
p. 132) Optimization should not be presented as a complement. It sounds too soft. Optimization is an essential criteria of the recommendations.
p. 135 - Fig 2) A constrain is a particular value of dose or risk to be applied for exposures in relation to a particular source. Its value can be derived from dose limit by taking account of all sources that can contribute to exposures and also by adopting reduction factors from optimization criteria applied to each of them. Therefore it may not be true that the dose limit is equivalent to the sum of dose constrains for different sources as it could be understood from Fig. 2. Optimization may introduce significant reduction of total allowable dose. Dose limit is a ceiling for the addition of dose constrains but it is expected that such addition will be much lower than the ceiling.
Therefore Public and Workers are protected from all regulated sources by dose constrains, by dose limits and by optimization (Figure 2).
p. 137) Constraints for emergencies.
The word constraint may not be the best word to suggest the almost instinctive reaction to manage situations that uncontrollably evolve out of constrains. Those situations require exceptional actions to avoid exposures that may be significantly higher than those adopted as constraints for normal situations and even higher than dose limits.
p. 138) Primary dose constraints. What does “primary” mean? Would there secondary dose constraints be?
p. 145) It should not true that the regulator does not have the information about all the sources that can contribute to public exposure.
p. 148) The emphasis should be not only on justification but also on optimization of the medical procedures.
p. 155) “…dose constraint to set primary level of protection”. What does “primary” mean?
Fig 2 and Table 7 Fig 2 shows that Dose Limit is the ceiling of dose constraints addition in normal situations. It might be difficult for a person who is becoming a new specialist in radiation protection to understand from Table 7 that there could be dose constraints much higher than dose limits in other situations. The convenience of employing different expressions appears again.
Table 7 recommends maximum values of dose constraints for “all type of exposure situations than can be controlled”. Accidental situations and emergencies that require evacuation are included here as well as normal exposures. To consider accidents or emergencies as controllable situations might be questionable.
p. 160) “Individual doses above several tens of milisiverts … requires that action be considered” This is too soft for normal exposure where occupational exposure should be substantially lower than 20 mSv/y and public exposure substantially lower than 1 mSv/y.
p. 161) The sentence “practices that have not been judged to be frivolous” makes an explicit reference to justification of practices, criteria that has been not included from the recommendations.
p. 164) First paragraph, last sentence: “ Any action taken may lead to both direct benefits and disadvantages” It is confusing.
p. 164) Second paragraph and Table 7: A constraint may be understood as a reference level that triggers an action when exposures are higher, but nothing should be done if exposures are below. 20 mSv /year is the dose limit for occupational exposure. From optimization procedures actual doses should be substantially lower and constraints established by regulatory agencies or operators will then be lower. To say that 20 mSv/y is the maximum constraint for occupational exposure may create the false impression that nothing has to be done if doses are no higher than 20 mSv /y. Constraints should be lower than dose limits. “Constraints are more restrictive than dose limits in normal situations” (p. 185)
p. 168) Patients are usually informed individuals also (otherwise their exposure could not be considered voluntary). It does not seem useful to introduce here the category of informed individuals since what really justify the classification in three groups is the relation between risks and benefits for each of them.
p. 190) “The optimization of protection is a forward-looking iterative process aimed to preventing exposures before they occur” It should say “to preventing or reducing exposures before they occur”.
New recommendations should explain once again somewhere what “social and economic factors being taken into account” means in reference to the mandate of “keeping doses, number of persons and potential exposures as low as reasonably achievable”. For instance: “In every country excessive protection costs might compete with other social needs and therefore economic restrictions may impose a reasonable balance among them”.
p. 192) “Intervention actions” is an expression mentioned by first time and has not been explained before in this draft. And “Levels for intervention actions” are called “constraints” in p.164 and table 7. It may be confusing.
p. 193) “Quantitative methods for optimization….may overemphasize societal aspects…” This is not necessarily true. Methods provide tools were relative influence of social and individual factors can be adjusted.
p. 200) “Collective dose…may aggregate information excessively” To aggregate information should not be a handicap. The question is that collective dose in the long term could aggregate too much uncertainty creating a false expectation of predictability.
It must be taken into consideration that collective dose is a tool also to evaluate other aspects of radiation protection such us protection of workers against the tendency of employing more people to reduce individual doses instead of adopting better radiation protection technology.
Collective Dose may be representative of Collective Detriment at least in the low range of individual doses according to present assumptions on stochastic effects. It may be difficult to decide whether 100 individuals receiving effective doses of 0,1 mSv/y represents a better o worse situation than 1000 individuals receiving effective doses of 0,01 mSv/y.
p. 213) “…..the emphasis is then in justification of medical procedures” The emphasis must also be in their optimization.
p. 217) This paragraph is not related to justification (chapter 9.1) but to optimization of protection for patients (chapter 9.3). Therefore this paragraph should be moved to chapter 9.3
p. 220 and p. 221) These paragraphs refers to pregnant patients that deserve particular considerations. They should not be positioned between justification and optimization concepts that are of generic nature.
p. 251) Fig 4 Practices and Interventions. Intervention has not been defined