| EUROPEAN COMMISSION
DIRECTORATE-GENERAL FOR ENERGY AND TRANSPORT
DIRECTORATE H - Nuclear Energy
Commission position paper on the draft 2005 Recommendations of ICRP
The European Commission was represented as an observer at the meeting of Main Commission and Committee 4 in Beijing. A draft position paper was posted on the “members only” website of ICRP. The paper has now been updated on the basis of the discussions in Committee 4, and was presented at the EU Conference on the ICRP Recommendations on 4 November. The Group of Experts established under Article 31 of the Euratom Treaty subsequently encouraged the European Commission to submit this paper to ICRP.
1. Maximum dose constraints
1.1. Exemption levels
A dose of 0.01 mSv in a year has been widely considered to be a good basis for exemption on grounds of individual dose (control may still be warranted on grounds of collective dose or because the practice is not inherently safe). It is appropriate to regard this dose as a minimum value of any constraint (while obviously optimisation may give rise to doses below the constraint). However, it should be deleted from table 7 (last row), since it is not a “maximum dose constraint”.
1.2. Concept of maximum constraints
Paragraph (163) rightly states that according to the type of situation to be controlled the authorities may set [specific] constraints below the maximum values. The word “maximum” and in particular the wording of (S7) replacing “the resulting values” with “national values of constraints” will be understood to mean that national regulations could set whatever “maximum” constraint if it is in the range down to one tenth of the ICRP value. This puts international harmonisation at risk.
1.3. Rationale for the situations to which dose constraints apply
1.3.1. Regulatory use
The proposed wording is not suitable for regulatory purposes. It gives examples rather than a strict rationale that allows one to judge unambiguously which level applies to the situation. In particular, it is not meaningful to make reference to the level of exposure (e.g., 100 mSv for “high levels of controllable existing exposures”, i.e., “if the level is high we raise the constraint”).
1.3.2. Relationship with intervention levels
The constraints match levels at which in the old vocabulary “intervention is almost always justified”. Lower intervention levels may be set on the basis of actual circumstances and specific cost-benefit analysis. The intervention level materialises in a contour line, e.g., on a map of a contaminated area. Outside this line there is no benefit for the individual to suffer the adverse effect of remedial action. Inversely, within this boundary there is “neither individual nor societal benefit” from maintaining existing exposure levels.
It is not clear how this relates to the concept of an individual dose constraint. In terms of equity, the uneven distribution of doses is the result of uncontrollable, accidental parameters and meteorological conditions. Inequity may only be perceived by the population living close to but outside the contour line: after remedial action on (for instance, evacuation of) the more exposed population the “borderline” population will have suffered the highest dose. This population will only accept this if it is fully informed and associated with the decision, i.e., aware of the actual risk and the adverse effects of the countermeasures. It will more readily accept high residual doses if it is empowered to be in control of exposure at an individual level.
1.3.3. The concept of benefit
It is probably true that exposure will be better accepted if the individual has a benefit from the practice giving rise to the exposure. This offers no sufficient basis, however, for setting constraints to individual dose. The individual will only accept high exposures if there is both a benefit for him remaining in the exposure situation (keeping his job or continuing to live in a radon-prone house) rather than avoiding it, and he fully understands that the resulting doses are reasonably low.
In situations where there is no individual benefit (a societal benefit is assumed for all justified practices) the dose constraint should be at the lower level of 1 mSv. The same lower level would seem appropriate even if there is a benefit to the individual but he has received no information or training to be in a position to assess or understand the net benefit, or if it is not judged worthwhile to provide reassurance through individual (or workplace) monitoring.
1.3.4. Revised Table 7
A new version of Table 7 is proposed that tries to overcome the problems discussed. It should both better explain the use of different constraints and be better suited for regulatory purposes. The conditions determining the use of different constraints should indeed be clear and prescriptive, rather than descriptive. In addition it may be useful to give examples of situations where earlier guidance has put constraints in a given range and explain why the rationale is appropriate to this situation. The earlier guidance may also need to be reviewed as a consequence of the new system of constraints.
REVISED TABLE 7
Maximum constraint (mSv in a year)
Criteria determining the acceptability of this constraint to the exposed individual
1 The practice has a generally understood societal benefit, but the individual himself has no direct benefit. The constraint also applies to situations where assessment of the actual exposure of a single person is not warranted or not practicable (the constraint may apply to a hypothetical reference individual or critical group), or where it is not judged appropriate to make the individual aware of his exposure.
20 There is a direct benefit for the exposed individual from the practice that gives rise to the exposure (e.g. in occupational exposure) or from not avoiding the exposure in existing situations (e.g., living in a house with high radon levels or in a contaminated area). The individual must be aware of his level of exposure, and, where appropriate, receive individual monitoring and training, and must be empowered to take adequate measures or adjust his lifestyle to reduce the exposure.
100 The situation is such that a high individual exposure of workers is justified in exceptional circumstances for the benefit of the undertaking (“specially authorised exposures”) or for remedial action in an emergency situation (rescue workers). It also applies to existing situations where it is not possible to reduce the exposure substantially without severe or prolonged disruption of an individual’s normal living habits. The exposure will be deemed acceptable only if it results from informed consent of the individual and society provides appropriate accompanying measures and health surveillance.
Exposures above the maximum constraint may be justified only in very exceptional circumstances, e.g., for live-saving action where a high risk to the rescue worker may be put in balance to a higher lethal risk to other people (or their almost certain death).
1.4. Regulatory implementation
For regulatory purposes the wording of the conditions applying to different constraints may need to be made even more prescriptive, e.g., “where no individual monitoring and information is provided, the dose constraint shall be 1 mSv”, or, “where doses exceed 1 mSv appropriate information shall be provided to each exposed individual".
It should be emphasised that nevertheless the dose constraints should not be regarded in all cases as a rigid boundary, nor that exceeding the constraint would be a regulatory imfringement. Indeed, the new system of constraints would allow the introduction of measures to ensure that the conditions warranting a higher constraint apply.
This may have implications for the definition of the “reference individual” for the assessment of exposures resulting, for example, from planned discharges of radioactive effluent. While it is conceivable that a few individuals would have doses that are higher than the constraint of 1 mSv, because of their unusual dietary habits or the unfavourable location of their home or work or leisure activities, such individuals should receive adequate information, be involved as stakeholders, and possibly receive compensation or benefit from mitigation measures.
The constraints should not be binding in case of existing situations or radiological emergencies. Optimisation, to the benefit of the individual, prevails.
1.5. Dose limits
It should also be explained how the dose constraints relate to dose limits, where the latter remain in force. While dose constraints relate to a single source, dose limits relate to the individual, possibly being exposed to more than one source.
Occupational exposures should still not be added to public or medical exposure. In general, the practice conducted by the worker’s employer is the sole source of exposure. Hence the dose constraint and the dose limit coincide (at 20 mSv per year). Exceeding 20 mSv is an infringement, unless it is a specially authorised exposure (with informed consent).
For outside workers there are multiple practices in different undertakings to be considered. It is the employer who should verify compliance with the dose limit.
1.5.2. Members of the public
The dose constraint applies to all exposures resulting from sources from which there is no benefit to individuals. The typical example is the release of radioactive effluent from nuclear installations. The exposure from all such sources must be added and compliance with the limit of 1 mSv must be demonstrated. In fact it will only be in exceptional cases that individuals belong to reference groups of the population for different installations. Where appropriate a lower constraint may apply (0.3 mSv). In general, other installations will contribute only by a few micro Sv, and these contributions can be ignored.
Exposures from (justified) consumer goods will in general be very small, most often the sources will be exempted. Consumer goods for which exposures are close to 1 mSv will only be purchased by informed individuals, for their own benefit. Hence a higher constraint is applicable and exposures should not be added to those from other sources, for compliance with the dose limit of 1 mSv. The same argument applies to exposures from building materials.
1.5.3. Existing and emergency situations
As before, dose limits for members of the public do not apply. However, the highest constraint, 100 mSv, may very well be regarded as a binding constraint (i.e., take remedial action even if, on the basis of optimisation, no action seems to be warranted, or impose building codes or radon mitigation works).
2. EXCLUSION OF SOURCES FROM THE SCOPE OF THE RECOMMENDATIONS
2.1. Relationship with exemption
It has already been explained in chapter 1 that 0.01 mSv is not a constraint, but a lower boundary for setting constraints. Nevertheless, optimisation may lead to levels below, even far below, 0.01 mSv. At such low doses no formal optimisation is warranted, and a common-sense approach is advised. Therefore, for justified practices, the level of 0.01 mSv can be used as a reference for generic authorisation, with exemption from some or all of the regulatory requirements.
This is very different from exclusion. No exposure pathway involving concentrations below the proposed exclusion level should, in fact, be included (especially for foodstuffs; it should be noted that the CODEX 2004 values are not yet endorsed and that some of the exemption/clearance levels calculated so far assumed these to apply to solid materials, not to food or liquids).
While for compliance with dose limits it may be judged appropriate to exclude exposures resulting from past practices and accidents, now part of the “background”, this argument is no longer relevant within the new system of source-related constraints.
Hence, there is no need for exclusion levels for artificial radionuclides.
2.2. Contaminated land
The draft 2005 Recommendations do not clearly state that exclusion levels do not apply to concentrations in soil as a result of planned release of radioactive effluent or from a nuclear accident. On the one hand such contamination is included in a regulatory control scheme, hence the concept of exclusion does not apply, on the other hand soil is not a material or commodity and the scenarios for exemption, which are the basis for the proposed exclusion levels, do not apply. In fact a territory with soil at the proposed concentration levels would cause doses of a few mSv.
2.3. Natural radioactive substances in environmental materials
The arguments in paragraph (208) are not convincing and relate more to the setting of high constraints than to the concept of exclusion.
It is not explained why it is reasonable to set exclusion levels somewhere towards the high end of the range of actually occurring concentrations. One should not avoid, however, mentioning the doses corresponding to such concentrations, even if it is not easy to explain that these doses are much higher than the exemption criterion. A useful reference is the European Commission’s publication RP122 part II.
2.4. Reference to DS161
A lot of work went into the careful formulation of the Safety Guide from which Table 10 is taken. All the nuance of DS161 is lost in the ICRP formulation. Also, the warnings are lost, e.g., that the levels for naturally occurring radionuclides should be applied with caution for bulk materials, especially building materials.
It does not seem meaningful to try and edit chapter 8 of the recommendations, since obviously the current wording reflects immature ideas. It is proposed to delete it and to replace it with a short paragraph explaining the meaning of “exclusion”, keeping close to the wordings of ICRP-60 (exclusion of exposures, not sources or materials), and emphasising the concept of “amenability to control”.
3. THE REPRESENTATIVE INDIVIDUAL
In the draft 2005 Recommendations, the Main Commission is “considering the use of age-averaged effective dose coefficients and age-averaged habit data for the individual in the case of continuing exposures of the public… Methods to assess such doses will be addressed by a Task Group of Committee 4” (178).
The draft report of this Committee envisages instead maintaining three age categories: 0 to 5 years (infant), 6 to 15 years (child) and 16 to 70 years (adult), represented respectively both for the dose coefficients and habit (intake) data by 1-year-olds, 10-year-olds and adults.
While there seems to be a large degree of consensus preferring this approach to the over-simplification of a single age-averaged individual, it may still be worthwhile to consider for the definition of the reference individual or group of the population an averaging over all ages.
The underlying idea is that dose constraints apply to a hypothetical individual in the reference group of the population who continues to be exposed to the same environmental pathway for a number of years into the future. A useful integration/averaging time could be 5 years, as in the 1990 Recommendations, or a lifetime.
A simplified picture of the age spectrum of the reference group of the population would be that all age categories are present as in the overall population. This assumption is more valid the longer is the accepted integration period. For modern western societies a rectangular distribution (all ages equally represented) can be assumed up to 70 years. Thus the averaging over a sufficiently homogenous group of actual people in a given location for a given pathway of exposure may reasonably be extended to an averaging over all ages.
This is not the same as the “lifetime” dose coefficient considered earlier. The integration should allow for the different intake parameters (diet, breathing rate) of different age categories.
While this concept may seem useful, it is important to identify in which situations the concept breaks down (e.g., because doses to one category are very much higher than to other, or because the reference group is predominantly composed of one age category).
A possible criticism could be that actual individuals might belong to different reference groups at different ages, and conservatively each time get the highest dose. This assumption does not seem realistic.
The optimisation of protection is still regarded as an important component of radiological protection. Optimisation is both a principle and a process, but while in the wording of the principle it is difficult to avoid words such as, “as low as reasonably achievable”, the process should not be confounded with “ALARA”, with the connotation of cost-benefit analysis. The process is now broadened, and new emphasis is put on societal aspects and stakeholder involvement.
4.2. Collective dose
Along the same line the concept of collective dose, defined as the integral of individual doses over space and time, is no longer considered useful. Indeed, the concept ignores all parameters except dose and thus is not a suitable tool for incorporating societal values and perception. Instead emphasis is now put on the distribution of individual doses, where such information is available, and the consideration of different groups with similar exposure and social characteristics.
4.3. “Weighted” collective dose
On the other hand, it is still advocated that a single indicator (different from collective dose) is more appealing than a “matrix” approach. For example, doses can be weighted as a function of time on a logarithmic scale or by the magnitude of the dose (e.g., a dose of 0.010 mSv would be given a weight of merely 1% compared to doses of 1 mSv). While the weighting over long time spans reflects in general societal perception, the weighting of doses may be criticised on the following grounds:
– there is a practical difficulty of “double weighting”, i.e., doses in a distant future are also much smaller;
– there is a risk that the weighting be wrongly understood as reflecting a less than linear dose response (avoiding the idea of a threshold but introducing it in a different form).
It should be underlined that very small doses (below 0.010 mSv) are only a small increment to the natural background, so that the biological effect is bound to be proportional to this increment. This is not a matter of biology but of mathematics.