Reference animals and plants

Draft document: Reference animals and plants
Submitted by Stephen L. Domotor, U.S. Department of Energy, Office of Air, Water and Radiation Protection Policy and Guidance
Commenting on behalf of the organisation

General Comments, Observations, and Recommendations - • The U.S Department of Energy (USDOE), Office of Air, Water and Radiation Protection Policy and Guidance, appreciates the opportunity to review the current ICRP document on concepts for the use of reference animals and plants for assessment of non-human species. In this regard it is noted that opportunities for fostering U.S. understanding, input, and potential consensus on the document could be improved through involvement by ICRP of a corresponding member from the U.S. Currently there are no U.S. corresponding members identified; as such the ICRP may be missing an important opportunity to obtain and resolve U.S. concerns and issues early-on in the document preparation and consensus-building process. Absent this opportunity, U.S. government and industry organizations are placed in a more reactive mode in commenting on potentially problematic approaches somewhat “after the fact.” • Further, there continues to be a perception that the ICRP is “bypassing” or giving little consideration to technically peer-reviewed approaches developed in the U.S. (and Canada) that have shown through several years of implementation experience to be successful in demonstrating compliance and assessing radioecological risks to non-human species. As an example, DOE’s “graded approach” to biota dose evaluation currently utilizes a system of reference organisms, kinetic-allometric equations for deriving Biv values that are often not empirically available, and DCFs and associated environmental transfer parameters for a suite of 8 organism geometries as contained in the RESRAD-BIOTA code. This system and its elements could be considered for their lessons learned value to the ICRP process, and for use as contributing elements of an ICRP system of reference animals and plants. We would encourage ICRP to take a less Eurocentric or “not invented here” approach and to give all methods currently available (e.g., those within the U.S.; Canada; and others) appropriate consideration and inclusion so that the final ICRP approach arrived at reflects a technically sound, rational, and implementable system. Doing so will foster the greatest opportunity for wide international consensus that includes views and consensus from regulators and industry stakeholders. • As stated in previous DOE and U.S. federal agency consensus comments provided to ICRP by the Interagency Steering Committee on Radiation Standards (ISCORS), consideration should given to a graded or tiered approach, to include screening levels, to cost-effectively eliminate those situations which pose no harm. In this regard it is not clear how the current ICRP document on reference animals and plants would be used to implement such an approach. • We continue to recommend to ICRP that changes or additions to the radiation protection system for the public and the environment should produce benefits that are equal or greater than the costs of development and execution of such a system. This criterion should be a key factor in considering any new guidance for application to protection of non human species and should be integrated into any process for the development of such guidance, to include the concepts for use of reference animals and plants. Specific comments on this overarching theme follow. Specific Comments, Observations, and Recommendations - • The title of the document is not consistent with the aims of the document as stated in section 1.1, the latter of which is much more encompassing than the title suggests. Further, it is suggested that the title be changed from: “The Concept of….. for the purposes of Environmental Protection,” to: “The Concept of ….. for the purposes of Estimating Radiation Doses [or perhaps Potential Radiological Impacts] to non-human species.” The point here is that reference animals and plants are not necessarily solely needed to demonstrate “environmental protection;” this can be accomplished through other means (e.g., as stated on page 8, section (6), first sentence of the document). • After considering the stated aims of the document in section 1.1, we make the observation that: (a) the aims are too broad for this document and are not reflective of the title given to the document; and (b) many of the aims of the document were not adequately addressed in the document. • Page 9, section (8), last sentence: “The question of whether one should protect individuals or populations from harmful effects of radiation in any particular circumstance, however, is not an issue of direct concern to the Commission.” Comment: This question is indeed of significant importance as it may impact the manner in which we determine if plants and animals are negatively impacted by radiation. In general, for both technical and regulatory applications in the U.S (e.g., as applied under CERCLA), it is the population that is used to determine if impacts have occurred; not the individual. Current radiological and non-radiological methods and the expected safe levels of exposure are intended for use in protecting natural populations of biota, rather than individual members of a population. The ICRP will need to address this question, or identify the appropriate organization that is best suited to address this question. This issue will impact some of the ICRP’s proposed approaches in the use and interpretation of dose estimate results from application of reference organisms relative to dose rate guidelines, effects benchmarks, increments of background concentrations, or other measures of effects to biota ultimately selected to determine “risk” or harm to non-human species. • We applaud the ICRP in their acknowledgement and inclusion in their more recent documents that “…a framework is needed that can be a practical tool to provide high-level advice and guidance, and thus help regulators and operators demonstrate compliance with existing or forthcoming environmental legislation” (page 9, section (10), first sentence). This is a comment and concern we have been making regarding the ICRP’s preliminary concepts on this topic for the past several years. However, there is little in the current ICRP document to substantiate this well-intended statement. For example, the concepts for reference organisms, derived consideration levels, and their application do not represent “high-level advice and guidance.” Further, the concepts, overly-specified set of reference organisms, and proposed use of increments of background for relating doses to potential impacts do not “provide practical tools that will help regulators and operators demonstrate compliance with existing or forthcoming environmental legislation.” The document needs further work to either: (a) re-cast the information in a way that can be used as high-level advice and guidance; or alternatively, (b): provide a rational, easy-to-implement, cost-effective standardized analysis method that can be used “out of the box” by regulators and operators to demonstrate compliance. Currently, the document does not accomplish either of the stated objectives. • Page 10, section (13): We see the proposed use of dose rates relative to increments of background as problematical. This is in part due to the wide spatial and in some cases temporal variation in background levels of radiation (e.g., within a region; and across differing regions of the U.S. and elsewhere); and in the fact that different organisms will be exposed to varying levels of background dependent on their habitat, home range, and behavior (e.g., degree of time spent above or below (e.g., varying depth) the soil or sediment surface for certain terrestrial and aquatic and riparian animals; migratory birds spending differing amounts of time in areas of different background levels) • Table 1 on page 18. The concept of identifying key factors or criteria for the selection of primary reference organisms is a good one. However, some key criteria are lacking: the organism’s relative radiosensitivity. Based on this and other criteria, one would question why earthworms and other organisms were selected. We suggest that the following criteria be added in addition to those provided: The organism should (1) be expected to receive a comparatively high degree of exposure (e.g., expected to receive a radiation dose to reproductive tissues which is relatively high per unit of radionuclide present in the ecosystem, in comparison to other receptors in the same community); (2) have a comparably high degree of radiosensitivity (e.g., radiation effects of concern occur at relatively low doses, in comparison with other receptors in the same community); and (3) exhibit a high degree of bioaccumulation. • Table 1 on page 18. The various criteria used to identify reference organisms should be weighted or divided as “major” and “minor” categories. For example, just because an organism is amenable to further study and is easy or available for use in toxicity testing (e.g., two of the ICRP criteria used), these factors should not drive the selection of the organism for use as a key reference organism. We suggest that other factors (e.g., to include: degree of radiosensitivity regarding reproduction; high accumulators; availability of accumulation data (e.g., Bivs); quantified, high-pedigree data on radiation effects for population-relevant attributes such as reproduction) should be “major” criteria for reference organism selection. The criteria applied, and the proposed set of reference organisms identified, need to be re-visited. • We are curious regarding the degree of consensus that was applied by the ICRP on the current set of proposed reference organisms. Given that ICRP Committee 5, to our understanding, has not yet officially met as a full committee, are the concepts and recommendations proposed in this ICRP document truly a set of ICRP consensus-based recommendations, or only of the document’s principal author(s)? We recommend that the criteria and rationale applied, and the current proposed set of reference organisms, be re-considered by all members of ICRP committee 5, and a consensus-based set of reference organisms arrived at from the committee be put forth. We also suggest that this committee-derived set of reference organisms then be made available for international stakeholder review for further consideration, comment, and consensus. The acceptability of the final ICRP reference animals and plants will be essential and critical for obtaining overarching international consensus by regulators and industry groups. As such the appropriate process and amount of time in working through the technical and implementation issues associated with reference organism selection needs to be taken by the ICRP. • Page 23, section (53) states that, regarding previous modeling approaches by IAEA and NCRP, “All of the approaches used have had to strike a balance between the complexity of the modeling that is theoretically possible, and the practical availability of relevant data to apply to them.” This is certainly a key consideration that we applied in the development of DOE’s graded approach to biota dose evaluation, and of the RESRAD-BIOTA code. However, the ICRP does not seem to be applying this key point they themselves stressed in the sentence above. The current set of ICRP reference organisms is too complex and impractical (e.g., 12 reference organisms; indirect inclusion of juvenile and life stages for a total of about 23 reference organisms). Further, lack of environmental transfer factors (e.g., Bivs) and adequate knowledge with known uncertainties of radiation effects for all of the proposed organisms and life stages will prevent practical and credible implementation of the proposed system. Further comments on this key comment are provided below. • The proposed set of reference animals and plants remains overly complex and is being advertised as “…..the development of a small set of Reference Animals and Plants, plus their relevant databases, for a few types of organisms that are typical of the major environments.” (page 10, section (11), lines 4-6). We observe that: o The suggested set of 12 reference organisms remains too complex and numerous. At IAEA Specialists’ Meetings over the past several years we recall that several experts from other countries suggested that a set of reference organisms should be in the range of 6, with no more than 10, for practical and implementation purposes. o The suggested set of 12 reference organisms appears to be Eurocentric in its origins and several of the proposed organisms (e.g., flat fish; brown seaweed) may not be optimal or serve as key indicator organisms for use in the U.S., or North America in general. o We question the appropriateness of selecting earthworms and bees as primary reference organisms. In particular, the selection of earthworms, while they may be an appropriate indicator organism for hazardous chemicals, is not appropriate for radiological impact assessment because they and some other invertebrates are generally not very radiosensitive. The same question may apply to other organisms selected for use. o We also note that missing within the ICRP’s proposed set of reference organisms is a geometry size suitable and representative of a large mammal (e.g., a grizzly bear; a whale). Several large mammals that are much more radiosensitive compared to other taxonomic groups (e.g., birds, fish, amphibians; reptiles; crustaceans; see UNSCEAR 1996; Whicker and Schulz 1982), and that are long-lived, have typically low numbers of offspring, and low frequencies of reproduction, would be important indicator organisms for North America and elsewhere. There are no provisions in the proposed ICRP system to permit analysis of these organisms because there is no ICRP geometry representative of the mass and dimensions for these organisms. o Regarding Table 3 (page 22), we recommend that the ICRP simplify its reference organism approach by first selecting a smaller subset of geometry sizes that could then be assigned to various specific organism types. For example, the geometry dimensions given for a rat pup and a bee are largely the same; and the same applies to the bee larva and the bee. Our experience has shown that there is very little variation in DCFs for geometry sizes of similar dimensions. One could simplify the system by selecting a core set of geometries (e.g., say 6 – 8) that could be used to calculate DCFs, and then assign the geometry size that most closely matches the actual organism geometry size selected for analysis. These concepts were successfully applied in the DOE methodology and in the RESRAD-BIOTA code. o Through inspection of Table 3 (page 22) we learn that there are actually 23 reference organisms, not 12. This is because several juvenile stages (e.g., eggs; tadpoles; larva) or larger organizations of organisms (e.g. bee colonies) are also included. Further, the expanded set of 23 reference organisms is complicated by the lack of availability and reliability (e.g., level of uncertainty) of effects data and environmental transfer parameters (e.g., Biv values) for these juvenile, egg, and larva stages of proposed organisms Do we really know with high confidence and uncertainty the radiation effects on bee larva and bee colonies? On crab larva and crab eggs? If our knowledge in these areas is incomplete, then once we calculate an estimated dose to these life stages, how will we then determine if the doses pose any potential impact to: (a) that particular life stage; (b) its relevance to the adult form; and (c) to the population of organisms? Do we have any means to determine what the impact of losing a few to several to a few hundred individual eggs or larva would be to the survival of the species in the context of the normally observed survival rate of individual eggs and larvae (e.g., of those lost through natural causes; predation; and other stresses such as thermal stress and chemical toxicity rather than radiation)? On this point, NCRP Report 109 (Effects of Ionizing Radiation o Aquatic Organisms; 1991) states that, “In most aquatic organisms, in which reproductive rates are generally very high and on which selective pressures are strong, the value of one or even thousands of individual organisms to the population is rather insignificant insofar as the long-term structure and fate of the population is concerned.” • Figure 1, page 11. We continue to recommend as we have in past comments that the ICRP not pattern their approach to radiation protection of non-human species solely for consistency with their proposed approach for humans as indicated in Figure 1. There may be sound technical, policy, and regulatory reasons why the approach for protection of biota should be different than that for humans. “Force-fitting” the approach for non-human species solely for consistency (e.g., the suggestion of Derived Consideration Levels using increments of background for both human and biota) may not be appropriate. See also section (14) of the report regarding this concern. • Page 24, section 4.2. (57 – 64) We were curious as to the lack of discussion of other “approaches to dosimetry” (e.g., those of Canada and the U.S.) at all or where noted in the same level of depth and detail as those for European approaches. • Page 28, section (72). Regarding dose rate recommendations. The statements that the dose rate guidelines developed by IAEA “….did not constitute official IAEA guidance” is misleading. The applicable IAEA reports on this subject, as well as those from UNSCEAR, and several other organizations all concurred on the 1 rad/d and 0.1 rad/d levels for protection of populations of organisms, and did indeed use the words “recommended” levels and “expected safe levels of exposure.” As another example, as directly quoted from IAEA-TECDOC-1091, “A general conclusion of the 1992 IAEA Technical Report was that there is no convincing evidence that chronic radiation dose rates below 0.1 rad/d will harm animal or plant populations. It was also stated that in the aquatic environments, limiting chronic dose rates to 1 rad/d or less to the maximally exposed individuals in the population would provide adequate protection of the population.” Other organizations and advisory committees have arrived at similar conclusions. For example, in 2002 the Advisory Committee on Radiation Protection (ACRP) charged with providing advice to the Canadian Nuclear Safety Commission (CNSC) recommended that the generic dose rate criterion for protecting biota should be in the range of 0.1 – 1 rad/d. The ACRP indicated that this dose rate criterion is based on population-relevant effects and, given the current state of knowledge and consensus views of radiation effects on biota, represents the level at which ecosystems will suffer no appreciable deleterious effects. Finally, in 2001 the UK Environment Agency concluded (in Copplestone et. al., Impact Assessment of Ionizing Radiation on Wildlife; 2001) that it is unlikely that there will be any significant effects in populations of freshwater and coastal organisms at chronic dose rates below 1 rad/d; terrestrial plant populations at chronic dose rates below 1 rad/d; and terrestrial animal populations at chronic dose rates below 0.1 rad/day. These are consistent with the findings of the NCRP, IAEA, and UNSCEAR. If the ICRP believes their statement at the end of section 72, “More generally, however, such summaries of the existing data have found it difficult to draw up a clear picture of the relationships between dose and effect for different types of animals and plants within the context of their normal, environmental, life histories” then what basis does the ICRP intend to use for identifying effects levels for radiation effects on biota, and for setting their “derived levels of consideration” using increments of background? • We encourage the ICRP to give consideration to DOE’s comments provided on previous versions of ICRP draft documents on a system for radiation protection of biota, as those comments continue to represent our viewpoints and recommendations on this topic, and are applicable to this current ICRP document on reference animals and plants. The set of DOE comments (submitted to ICRP on 12/29/04) on the “Protection of the Environment” section of the ICRP 2005 Recommendations are again provided below in their entirety for your consideration. Background as Context for DOE Comments - DOE comments provided are based on our experiences and lessons learned in developing and implementing methods and dose rate guidelines within a graded approach for evaluating radiation doses to non-human species, our development of the RESRAD-BIOTA code, participation in the ICRP Task Group on Protection of the Environment (ICRP Publication 91, 2003), participation in related IAEA Specialists’ Meetings and symposia on this topic, and our ongoing participation in the newly-formed Biota Working Group of the IAEA Environmental Modeling for Radiation Safety (EMRAS) initiative. Summary Comments and Suggestions Regarding the ICRP 2005 Recommendations on Protection of the Environment: Much of the material presented in the draft is not appropriate for a recommendations document because it lays out a plan of work rather than recommended actions. The presence of this material seems to imply a much greater degree of finality than would appear to be warranted. Several U.S. Federal Agencies have previously commented to ICRP on the topic of environmental protection. The concerns expressed in those comments remain valid. Given that the ICRP has stated that their activities have not been driven by any particular concern over environmental radiation standards, proceeding with the development of a framework parallel to the recommendations for human protection, including a complex, comprehensive biota research and dosimetry development program, appears somewhat premature. An assessment of where, under what exposure scenarios, and to what degree the current system of radiation protection for humans may not be protective of non human species may be warranted. A capability to compare and benchmark the results of the biota dosimetry methods and tools already developed and readily available through many countries would also be useful. From this assessment of current circumstances and capabilities, the potential need for and degree of complexity of future proposals can be better determined. The ultimate approach for protection should be flexible such that decision makers and users can select and use those dose evaluation and modeling tools that match to the specific purpose and data quality objectives of their assessment. As stated in previous DOE comments, consideration should be given to a graded or tiered approach, including screening levels, to cost-effectively eliminate those situations which pose no harm. The ICRP is encouraged to clarify its intent, and avoid detracting from on going efforts to improve, integrate, and harmonize the existing assessment tools and framework of protection of the public health and safety and the environment. The ICRP is also encouraged to engage in an ongoing dialogue on their proposals, and take the time necessary to develop an international consensus, since it is not obvious that there is a need for a framework for protection of non human species that parallels the current framework for protection of humans. Changes or additions to the radiation protection system for the public and the environment should produce benefits that are equal or greater than the costs of development and execution of such a system. This criterion should be a key factor in considering any new guidance for application to protection of non human species and should be integrated into any process for the development of such guidance. Specific Comments: 1. We continue to believe, as expressed in earlier comments to ICRP in 2002 on this topic (December 13, 2002; RE: ICRP Draft Publication 91) that the ICRP’s decision to proceed with a complex, comprehensive biota research and dosimetry development program is somewhat premature. An ICRP-sponsored, resource-intensive comprehensive biota dosimetry development program is further questioned, given the suite of biota dose and risk assessment methods and tools currently under development or now widely available and implemented by many countries. A logical step in determining the nature, scope, and complexity of any ICRP-proposed protection system is to first review and assess the suite of biota dose evaluation methods and tools already developed and readily available through many countries, to include the U.S. (e.g., the Department of Energy’s Graded Approach for Biota Dose Evaluation and RESRAD-BIOTA code), Canada (e.g., methods to support the Canadian Nuclear Safety and Control Act), the United Kingdom (e.g., Impact Assessment of Ionising Radiation on Wildlife R&D Publication 128; 2001), and Sweden (e.g., the FASSET and ERICA Programs). From this assessment of current capabilities, the need for and degree of complexity of an ICRP-proposed system can then be determined. On this note we are pleased that the ICRP is cooperating with the IAEA’s EMRAS Program of methods and model comparisons regarding many of these available biota dose estimation approaches, and we are an active participant in the Biota Working Group through which these comparisons will be conducted. 2. Consistent with comment (1), an assessment of where, under what exposure scenarios, and to what degree the current system of radiation protection for man may not be protective of the environment should first be conducted. Such an assessment would provide insights on the degree of need for and appropriate complexity of a new ICRP dosimetry program for non-human species. 3. If a general framework for environmental radiation protection is advanced by the ICRP, we believe that an important component should be the inclusion of screening levels - levels of radioactivity or radiation dose that are clearly not harmful to non-human species under bounding conditions - within a graded or tiered assessment approach. Such a general screening level approach is common to many regulatory programs and can quickly and cost-effectively eliminate from further consideration those contaminants which pose no harm to the environment while allowing resources to be directed towards those contaminants having the potential to put non-human species at risk. As an example, DOE applies screening concentrations, termed “Biota Concentration Guides” or BCGs, in its graded approach for evaluating radiation doses to biota. Implementation experience using this approach since 2002 indicates that screening evaluations were successful in demonstrating biota protection, are cost- and time-effective, and in most cases eliminated the need for more detailed and resource-intensive dose and ecological risk assessments. 4. The ICRP development of a standardized set of reference organisms and related dosimetric models should carry a much lower priority of activity than the development of a revised policy statement, the development of a generalized protection framework, and development or re-affirmation of acceptable effects endpoints and dose rate guidelines for protecting populations of non-human species. 5. Care should be taken not to pattern the approach for biota protection solely for its ability to integrate with and be consistent with the ICRP’s proposed recommendations and approaches for human protection. There many be cases where such consistency and common level of complexity is either not appropriate, or where the protection system for non-human species - for technical, policy, and implementation reasons - should indeed be different than the ICRP’s approach for man. 6. As highlighted above, we believe that a number of dose modeling approaches for non-human species already exist. Rather than focusing on the development of comprehensive ICRP dosimetric models for biota, we believe that the ICRP’s first priority should be to develop high-level umbrella policy, and put forth a generalized framework and set of guiding principles (e.g., employing Data Quality Objectives considerations) through which currently existing biota dosimetry methods and tools can be selected and implemented. We believe that the second priority should be to provide recommendations on acceptable effects endpoints and dose rate guidelines (or acceptable ranges of guidelines) for protection of biota. Virtually all evaluation methods are based on the calculation of a dose to biota, which is then related to or compared with dose rate guidelines or a unit of measure/threshold (e.g., radionuclide concentrations in environmental media) that is determined to be protective of biota. Consensus-based effects levels and dose rate guidelines (whether for broad groupings of biota types, for individual taxa, or expressed in terms of environmental media concentrations) will be needed for the implementation of any framework that contains as an element the estimation of doses to biota. 7. The dose rate guidelines recommended by the NCRP (in 1991) and IAEA (in 1992) for protection of populations (using reproduction as the critical endpoint of concern) have generally been well received, validated, and implemented by a number of countries and organizations. As a starting point these dose rate guidelines, along with additional data available from recent studies (e.g., through the FASSET effects database) and from other countries (e.g., Canada through the CNSC efforts) could be re-evaluated. Up-front discussions and agreements regarding the data quality objectives for inclusion and interpretation of available data (and the planned approach to be taken, such as generation of No Observed Adverse Effects Levels, NOAELs) would need to be carefully and thoroughly discussed and agreed upon prior to this effort. Without the validation and/or re-affirmation of the currently applied NCRP and IAEA dose rate guidelines, or the development of consensus-based ancillary or alternative dose rate guidelines (or “benchmarks,” “consideration levels,” or some other acceptable terminology), risk assessors, regulators, and nuclear facility operators will be faced with many different and contradictory protection guidelines for biota that will complicate decision-making, particularly when working with stakeholders. 8. The ICRP Recommendations Document states in section 248, last sentence, “the question of whether one should protect individuals or populations from harmful effects of radiation in any particular circumstance is not an issue of direct concern to the Commission.” We suggest that this type of policy consideration is indeed an appropriate issue of direct concern to ICRP and its stakeholders, and one that ICRP should provide a position on. The standard and accepted practice regarding demonstrations of protection of the environment (i.e., non-human species) from stressors or agents (e.g., chemicals) is at the population level. As such, we believe that the development of acceptable dose rate guidelines (or environmental media concentrations corresponding to acceptable dose rates) should be based on population-relevant attributes (e.g., effects on reproduction; mortality; morbidity). They should not be based on effects that, while observed at the individual or sub-individual level (e.g., cytogenetic effects), have no relevance to protection of populations or cannot be quantified in terms of their impact to populations. As an example of the difficulty and misapplication of effects observed at the sub-individual level, consider the point made by Dr. Norman Gentner, chairperson of UNSCEAR, at the NEA Forum in Sicily (February, 2002) and as quoted from his presentation abstract: “A special caution is urged if data on radiation-induced mutations per se are utilized as part of environmental assessments, as the average rate of radiation-induced mutation applicable in the context of environmental risk assessment is likely to be much lower than assumed from studies of induced mutation in non-essential genes, which is usually what is involved. Findings from the UNSCEAR 2001 Report (‘Heredity Effects of Radiation’) illustrate this point.” 9. This comment concerns the discussion on the ICRP’s proposed “Derived Consideration Levels” and proposed use of background concentrations. Given the wide range of uncertainty in our ability, based on the current state of science, to determine the relevance of impacts at the sub-individual level (e.g., cytogenetic effects) to effects on individuals, and the relevance of impacts on individuals (and their numbers impacted) to populations, along with the uncertainties associated with the presence of other environmental stressors, it is not clear how the proposed scheme would be implemented.