Protection of the Environment under Different Exposure Situations

Draft document: Protection of the Environment under Different Exposure Situations
Submitted by Diego Telleria, IAEA
Commenting as an individual

1)      The Derived Consideration Reference Levels (DCRLs) have been defined by ICRP as ‘bands of dose rates to assist, inform and guide efforts on environmental protection’ and (the band) is referred in ICRP 108 as to be used as a “point of reference”. I believe that DCRLs could be now perceived in a much more restrictive way in this new ICRP document, as a sort of region of doses whose boundaries cannot be exceeded. This perception could be inferred from the fact that, for planned exposure situations, the lower boundary of the band is mentioned as “the appropriate starting point for optimization” (and not the full band as it can be understood from ICRP 108). I believe that it would be more appropriate, for planned exposure situations, to have the lower boundary as the level below which there is no need to optimize further, while if doses to animals and plants are within the band, optimization may be considered, taking into account management objectives and other factors already mentioned in ICRP 108. If doses are above the upper boundary, probably the situation should be considered more carefully, but it would not necessarily be a breach of the rule’ (as DCRLs are defined by ICRP as ‘not a limit’). Furthermore, optimization below the lower end of the bands of DCRLs has a conceptual mistake that I will explain later.

2)      The definition of a new concept -not included in the ICRP 108- for consideration of multiple sources, the Environmental Reference Level (ERL) below DCRCLs for individual sources, clearly contributes to the improper perception of DCRLs as limits.  Furthermore, while multiple sources could affect same individuals of animals and plants it is much more improbable that multiple sources during planned exposure situations could affect more significantly at the level of their populations. The “cumulative impacts” of multiple sources, which are clear for impacts on human individuals, are not necessarily similar in the case of plants and animals populations. For example, if the same limited number of individuals of animals and plants were to receive more radiation doses due to multiple sources this would not necessarily have cumulative impact on their populations. In addition, the introduction of the ERLs with some parallelism to ‘dose constraints’, which is used for human protection as an upper limit for optimization, is a conceptual mistake (see next comment). Consideration of multiple sources could be mentioned in the document as an issue to be considered, probably needing some practical solutions, but this does not need to lead to the introduction to a new possible misleading reference level.

3)      I believe that optimization below DCRLs or below ERLs is a conceptual mistake. DCRLs are generally defined on the basis of information on deterministic effects at the level of individual plants and animals. Deterministic effects are likely to have thresholds and, at lower level of doses, a linear relationship between radiation dose and effect cannot be established (similar to, for example, the linear non-threshold hypothesis assumed for stochastic effects for humans which is the basis for optimization in this case). This is even more important for planned exposure situations because, a higher threshold in terms of distribution of doses for radiological effects at the level of populations could be considered, since increased levels of radiation doses affecting a few individuals of plants and animals (a typical situation for planned exposure situations) would not necessarily be considered to affect the entire populations. Without a dose-effect function, ERLs would be set in an arbitrary way; optimization below the lower boundary of DCRLs or ERLs would reflect an arbitrary and possible unnecessary additional precautionary approach, especially considering that the lower ends of the bands of DCRLs were already select in a precautionary way. Optimization within DCRLs band could also present the same problem of a lack of a dose response function but in this case such an approach could be considered as part of reasonable ‘agreement by consensus’ by the international radiation protection community until the current lack of information in some areas of the radiological impact at the level of population is resolved. For instance, it could be established that If doses are within DCRL bands consideration should be given to try to reduce exposures by mean of any practical option; this approach would be much more in line with the spirit of what a ‘consideration’ level is.

4)      The document seems to contain an incorrect interpretation of some international instruments which include consideration on protection of the environment. Some of these instruments were created well before ICRP and the international community discussed new possible approaches to radiological protection of the environment (a broader field than protection of plants and animals alone). The ICRP document seems to wrongly conclude that the requirements to protect the environment set in some of those international instruments include the need of explicitly demonstrate protection of animals and plants. I could refer in particular to the 1997 Joint Convention on the Safety of Spent Fuel Management and on the Safety of Radioactive Waste Management. (Note: It should be remembered that this international convention is similar to other conventions signed by contracting parties - e.g. the Basel Convention and the Kyoto Convention- and is not an IAEA standard as it could be interpreted in the way it is referenced in the document). When the text of Joint Convention was approved, the assumption that ‘standards for protecting humans implicitly protect the flora and fauna living in the same environment’ was considered valid. This assumption is still likely to be correct (as it is said in ICRP 103), particularly for planned exposure situations and is still considered a valid option in the IAEA safety standards and in the regulations of many countries worldwide. For example, the revised IAEA Basic Safety Standards published in 2011 (IAEA BSS) mention that the system of radiological protection set in the standards generally provides for adequate protection of the environment, but adds that, nevertheless, international trends indicate an interest on an explicit demonstration rather than an assumption. The IAEA BSS leaves to its Member States the option to demonstrate explicitly rather than implicitly the protection of plants and animals. An implicit demonstration would be, for example, to use a generic overarching consideration that takes account of releases, dispersion, environmental transfer and the requirements for the definition of the Representative Person. I believe that this new ICRP document in preparation should avoid a retrospective interpretation of legislations already in place and, furthermore, the interpretation of what radiological protection of the environment should imply for regulatory purposes and the development of international standards and the related practical guidance should be left to other international organizations.

5)      The document emphasizes the differences between ‘actual plants and animals’, the ’Reference Animals and Plants’ (RAPs) and the ‘Representative Organisms’. While it is understandable from a scientific point of view that this differentiation is indicated in the ICRP document, as this could be a valid advice for some special environmental situations, the insistence within this more practical guidance in preparation about the need to consider real plant and animals when assessing radiation doses may create some uncertainty in the international radiation protection community that the RAPs defined by the ICRP can be used in general and most of the cases in a straightforward way. The way this topic is discussed in the document, gives the idea that, for animals and plants, a similar approach to that used worldwide for protection of the public in planned exposures would not be possible (e.g., the use of a ‘Representative Person’, based in a ‘Reference Person’ and more or less realistic habit data). It is important to remember that, the same limitations exist in the concepts of ‘Representative Person’ and ’Reference Person’ when used to determine the radiological impact on actual human beings around a nuclear installation, but, nevertheless, the approach used to define discharge limits, which uses reference individuals rather than real people, has demonstrated its effectiveness to protect real people and would be similarly effective to protect real populations of plants and animals. In a report which intends to give a more practical advice, like the one submitted for consultation, I think that a better approach would be to give the message that ‘using these RAPs that ICRP provided, has some limitations which must be known, particularly for some special environmental situations (e.g. in the presence of species includes in a particular legislation, endangered species, particular ecological niches, etc.) but it would work in most of the cases’.

6)      It is important to remark that, a discussion on the concept for plants and animals corresponding to the concept of ‘critical group’ (or ‘representative person’) for humans is still missing. This necessary discussion is more related to the exposure scenario than to the limitations on how to model organisms (as it is in the case of radiation protection of public, where, in general, it is accepted that the numerical values derived from Reference Individuals are used to calculate the exposure to the Representative Person when the location and habit data is agreed). For example two of the most important discussion for the case of plants and animals in planned exposure situations which are missing in this document are where the RAPs identified as critical to ensure a proper evaluation of the impact at the level of population are located and which fraction of the population that should be considered for the assessment of the radiological impact and its control. Without this discussion, practical applications would be difficult to be developed and applied in international standards.