Comments on the ICRP Draft for Consultation on “Protection of the Environment under Different Exposure Situations” (17 July 2012)
The draft is generally well prepared and the objective of presenting environmental radiation protection within the context of the existing system of radiological protection is helpful and marks a significant step forward. The draft (and Annex A in particular) also provides useful contextual information on the broader nature of environmental protection requirements. However, the proposals are significantly more complex than warranted by either the available effects data or the accuracy of the available assessment methodologies.
Key points are identified below in sequence (although many are interrelated):
-There is recognition (paras 47, 48, 52, 56 and 57) that the environmental radiation protection is less mature than the existing system of radiological protection, and that the proposed system should complement controls to protect the public and not add unnecessarily to its complexity. However, this is exactly what the proposals presented appear to do, particularly with the introduction of further reference levels and the establishment of a potentially competing system of optimisation to ‘environmental exposures’.
-It would be advisable to undertake further analysis of the need for and impact of imposing additional criteria/costs to ensure that this is not done without clear added benefit, particularly during a time of economic and environmental stress.
Optimization of Protection
-The focus on the scope of optimisation, and guidance on the applicability of the DCRL bands, is or appears to be inconsistent with that included in ICRP Publication 108. In that publication, the values were presented as ‘point of reference to optimize the level of effort expended on environmental protection’ for all exposure situations. This broader and less formal scope of optimisation (and the role of DCRLs) is more appropriate for the less mature system of environmental radiation protection than those presented in the current draft.
-In this draft, it is proposed that the principle of optimisation of protection should be extended to ‘environmental exposures’, thereby inappropriately applying an approach that has been developed primarily to limit the occurrence of stochastic effects in individuals, whereas the impact on populations of biota are functionally described more by thresholds. The recommendation to optimise within and below the DCRL band implies a continuum of effects, which is unlikely to be the case.
-In most cases, it would be more appropriate to include ‘environmental considerations’ within the factors that need to be considered in making management decisions about releases to the environment (e.g. in optimising protection of the public). This would also be more consistent with the International Basic Safety Standards.
-It would also be more helpful to refer to overall protection or management decisions rather than optimisation of protection (which has a very specific meaning within radiological protection).
-There is some inconsistency in the specification of the object of optimisation; it is variously described as relating to the level of effort and of environmental protection (line 652). This should be clarified.
-The argument for applying the optimisation principle to ‘environmental exposures’ is particularly weak; optimisation is said to apply to all types of exposure and therefore also to apply to ‘environmental exposures’, though these have only been defined in this draft and had certainly not been considered when the scope of optimisation of protection was defined (line 582).
Environmental Reference Levels
-Environmental Reference Levels (ERLs) are proposed for planned exposure situations at a level below the DCRLs. These values are presented as analogous to dose constraints (or more accurately the historically defined ‘source upper bound’, which preceded them). There are insufficient data to support the lower DCRLs in many cases and the derivation of even lower levels could only be arbitrarily determined. If such levels were to be defined, they would be more usefully specified as screening levels (analogous to exemption) rather than as quasi-limits, as presented in the current draft. The fact that the acronym ‘ERL’ has previously been applied by many countries to ‘Emergency Reference Levels’ is also confusing.
-The principle of limitation is said not to apply to environmental exposures, although the description of the lower DCRL and ERL for planned exposures comes perilously close. Furthermore, ‘equity’ was given as the basis for limitation in the existing system of radiological protection, where limits have been based on the concept of ‘tolerability’; equity was used to define the basis for constraints and constrained optimisation.
-As indicated above, guidance on the applicability of the DCRL bands is or appears to be inconsistent with that included in ICRP Publication 108. In this draft, DCRLs are presented mainly in the context of existing exposures or where environmental exposures of significance arise from any major nuclear facility. It is unclear why large non-nuclear facilities are excluded (mines, oil and gas facilities).
Environmental protection and biota dose assessments
-The linkage between environmental protection and the assessment of dose rates to biota is dealt with in Section 2.3, but the distinction between the objective of protection of the environment (incl. environmental media, resources etc) and a focus on the assessment of harm to living organisms is so fundamental that it would be useful to have been introduced earlier. The discussion of the distinction between environmental media, as often the legally defined object of protection and the nature of harm (which leads to ICRP treating these as pathways of exposure) is useful, but could be taken further.
Environmental Exposures
-The use of the term ‘environmental exposure’ implies that biota are the object of protection, but the linkage between protection and assessment goals is not sufficiently described (although there is some information presented in Annex A).
-Environmental exposures are said to run parallel to the other exposure situations. However, in reality, they are parallel only to public exposures arising from radioactive materials released to or present in the environment, and it would be helpful to make this clear. The integrated context is insufficiently recognised (although the potential application of combined criteria is referred to in Para 52).
Potential Exposures
-There appears to be some confusion between the consideration of potential accident situations and emergency preparedness and response (e.g. lines 708 – 709). In this draft, the considerations are included in the discussion of emergency exposures and in the context of ‘severe effect levels’. It is also not clear how these would be applied in a probabilistic assessment.
Justification
-The inclusion of environmental considerations within justification is positive. There are, however, inconsistencies in the way in which this is presented. In line164, reference is made to the assessment of impacts to biota, while ‘the environment’ is referred to in the following sentence.