|Thank you for providing again the opportunity to comment on the ICRP draft recommendations. This draft has been considerably improved in response to comments made at the earlier consultation, but in my view there are still some areas for further improvement, as outlined in the comments below.
Section 2.3 The scope of the recommendations
In this section, the Commission introduces the terms planned, emergency, and existing to characterise the different exposure situations, instead of practices and interventions. The Commission argues in (37) that the latter distinction is now considered as being artificial. I am not convinced that this change is justified with this argument, certainly not because the terms practices and intervention are still used by the Commission. Moreover, as stated in (38) and (39), both the terms practices and interventions have become widely used in radiological protection and have been incorporated in national and international standards. I therefore believe that such a change is in contradiction with the third primary aim of the revised recommendations, as stated in the Preface, unless the reasons are better explained.
In (37), there is a reference to section 5.4, but I believe that the right reference is to section 5.2.
Section 2.4 Exclusion and exemption
The description of the concept of exemption in (42, ii) is in contradiction with (43) and (46). A negligible, or trivial, risk is just one of the reasons to exempt a source. As is stated in (43), regulatory control is not warranted if the societal efforts needed for its application would be disproportionate. This is specifically the case for practices with natural radionuclides, where the source may be exempted from control at much higher doses than 10 µSv/y, which are certainly not trivial. A trivial risk of 10 µSv/y should therefore only be considered as a level below which every source should be exempted. The Commission should consider rewording of (42), (43), (45) and (46) in order to make the application of the concept of exemption more transparent.
Section 4.5.3 Occupational exposure
The last three sentences of (133) (starting with "In the calculation ...") are very important, specifically for inhaled natural radionuclides in a matrix where radon and\or thoron do not escape from the particles. In ICRP publication 68, when calculating the dose coefficient for 226Ra, this situation has been taken into account, but later on the Commission has taken a different position. In ICRP 72, Annex B, a correction is made for the dose coefficient of 226Ra, by stating that this assumption appears to be overly cautious for 226Ra, where a substantial fraction of 222Rn decay products would be expected to escape from the lung. Many NORM materials, such as mineral sands, show a radionuclide composition where 238U or 232Th are in secular equilibrium. This implies that the radionuclides of radon do not escape from the matrix and therefore contribute to the dose coefficient when inhaled. The Commission should reformulate the last sentence of (133) in order to make clear for which situations the original assumption for using the dose coefficient of 226Ra, as taken in ICRP 68, is better reflecting reality.
Section 5.4.1 Workers
In (171) the Commission states that "Other workers .... are more similar to the general public and are treated as such". This may be the case, but they are still radiation workers, as defined in (170). Does (171) imply that for such workers a dose limit for members of the public should be applied?
Section 5.4.3 Member of the public
In (175), the Commission introduces the concept of the representative individual, which is defined in (176) as an individual that "receives a dose that is representative to the more highly exposed individuals in the population". The Commission continues with stating that such an individual exhibits the "typical habits of a small number of individuals representative of the most highly exposed", although it is not the individual that shows "the extreme habits of a single member of the population". Also in (184) and other paragraphs, the Commission refers to the most highly exposed individuals as being the representative individual. This is very confusing. The group of most exposed individuals include by definition the extreme, and I understand that this is not the purpose of the Commission. The Commission should be transparent and use the word "more exposed" instead of "most exposed" when referring to the representative individual.
Constraints (Sections 5.8.1 and 5.8.2)
The extension of the concept of constraints to emergency and existing situations, thereby replacing the intervention action levels, is still a matter of concern. In the current recommendations the action levels represent the dose above which an intervention is almost always warranted, i.e. the upper level of an intervention band, and the intervention should be optimized to achieve the highest benefit of the action. In the proposed system, the constraint represents the dose level below which regulatory action, i.e. optimization, should be exercised. Does this imply that for every existing situation causing an exposure below the dose constraint, and which is not excluded or exempted, an optimisation is required?
The concept of dose constraints for planned situations has been introduced in the current recommendations, but the implementation of the concept in national regulations has shown to vary considerably in different countries. A recent survey of the European ALARA Network to the implementation of the concept in European national regulations showed that the concept is misinterpreted in quite some occasions, sometimes caused by difficulties in translating the term constraint in the national language. It is highly questionable if the extension of the concept to emergency and existing situations will be seen as a simplification of the system and thus leading to a better understanding. As stated earlier, such a change in the applicability of the concept is in contradiction with the third primary aim of the revised recommendations and the need for it should be clearly explained.
In (201) the Commission refers to dose constraints for existing and emergency situations that, in some rare exceptional situations, could be higher than any dose limit. It is confusing to make this comparison with dose limits, which are only applicable to planned situations. It strengthens the impression that the dose constraints can play the role of dose limits in certain situations. This impression comes also from (198) in which it is stated that the dose constraint is the most fundamental level of protection, and that the intention of the optimisation process is to result in exposures that are below the relevant dose constraint. The use of the dose constraint should be flexible, certainly for existing and emergency situations. The Commission places too much emphasis on the role of constraints in the radiation protection system. In my view, it is the other way around: the most fundamental level of protection is provided by the optimisation process, in which the dose constraint is only a tool to avoid inequity.
In (205) the Commission states that "the second band .... applies in circumstances where individuals receive direct benefits from the exposure situation ...". This is not very likely to be the case in the emergency situations to which the last sentence refers. This should be reworded.
Also the last part of the first sentence of (206) ("... where the source cannot be controlled.") should be reworded. It is no use to set constraints on such a source. This is also the case for Table 4, where in the band 20-100 mSv the situation is characterised as "either not controllable or where actions to reduce doses would be disproportionately disruptive".
Section 5.8.7 Application of optimization and constraints
In (231) the word "could" should be replaced by "should".
Section 7 EXPOSURE TO NATURAL SOURCES
Paragraph (280) deals with exclusion and exemption for natural sources and it refers to section 2.2. I assume that reference should be made to section 2.4.
Section 7.1 Type of exposure
This section (as well as (288) in the next section) does not address recommendations, but only gives an overview of natural exposure situations. It should be deleted, or else revised drastically.
Section 7.3 Controllability of natural sources
Paragraph (294) deals with exclusion of natural sources, and should be redrafted considerably for the following reasons. Although I welcome the adopted values for activity concentration of the natural radionuclides below which the sources should be excluded from control, the Commission does not give any explanation why these values are considered to be the right dividing line between controllable and uncontrollable sources. Neither do I understand why these values are only applicable for exclusion of unmodified concentrations. What happens when such materials are modified and the concentrations are still below the values quoted in this paragraph? Are they no longer excluded after modification? It should also be mentioned that natural radionuclides in building materials, just as in food stuffs, drinking water and animal food, should be regulated in a separate way, instead of being exceptions of the exclusion level values.
Furthermore, I do not understand the introduction of an exclusion level of 40 Bq/m3 for radon. The exposure to radon is controlled by the application of the optimisation process when the radon concentration exceeds the action levels. The resulting radon concentration is the optimum, and therefore it is useless to introduce an exclusion level.
The reference to Chapter 10 in (294) is unclear.
Paragraph (295) deals with exemption, but is of a generic nature and has nothing to do with natural sources. Instead of that, a paragraph should be written which specifically deals with exemption grounds for natural sources. Exemption should be possible for natural sources above the exclusion levels, but where the resulting exposure leads to doses below a certain constraint, say 1 mSv/y. Even above such a constraint, the natural source might still be exempted when the dose is considered to be the optimum. When the source is not exempted, a graded approach or regulatory control, as mentioned in paragraph (290), should be applied.
Section 7.4 Constraints for radon in dwellings and workplaces
Paragraph (296) and (297) deal with epidemiology and should be placed in Chapter 3.