Reference animals and plants

Draft document: Reference animals and plants
Submitted by Yoshito Watanabe, National Institute of Radiological Sciences
Commenting on behalf of the organisation

2005 July 22 Comments on FD-5 <General comments> - As a primary step, from pragmatic and feasible viewpoints, the reference animals and plants proposed in the foundation document are favorable to represent taxonomic families of wild lives in the environment. While, as the reference man should have its secondary sets to adjust the individual attributes (Caucasian or Mongolian, life stage (embryo, infant, child, adult) sensitivities, regional properties (life style, food, etc)), reference animals and plants should have secondary reference animals and plants, which could demonstrate the soundness (well balance) of the ecological system of the specific (target) environment. - Secondary reference animals and plants should be nominated for each target environment (or ecosystem) on the basis of the specific knowledge of the target environment, i.e., population balance of the species, food chain structures, material cycle fluxes, intra-specific and inter-specific interactions (competitions, predation, cooperation, etc.). Natural disturbances and stresses and their following population dynamics should also be analyzed to find the key issues for the sustainable self-organized mechanisms of the target ecosystem. Monitoring should be made on the key biological markers of the selected key species based on their ecological positions. It depends on the specific assessment of the environmental impacts, so procedures how to narrow down to nominate the ecological indicators should be developed by ICRP on the basis of scientific judgments of the ecology and toxicology. - Secondary references may include ecological indicators, keystone species or umbrella species of ecological systems from the viewpoint of sustainable balance. For example, phytoplankton and zooplankton could be secondary references, because unicellular algae (phytoplankton), Daphnia (Zooplankton) and fish occupy major trophic levels in aquatic ecosystems. They are also used as a basic set for toxicity testing of chemicals, and amenable to further studies for radiation and radionuclides. - Microorganisms can also be candidates for secondary references, since they play a lot of important roles in the ecosystem. Microorganisms live everywhere on the earth, and any animals and plants cannot live without microorganisms. They are also key species for material cycles in ecosystems. Possible accumulation of radionuclides in the microorganisms, such as Cs in fungi and U in bacteria are also important to be considered. Selected references in this draft cannot be the reference of microorganisms. Although the present data set for microorganisms are limited, they are amenable to further studies. - Plants are so diverse that it should be difficult to cover the whole plant kingdom only with two references. In addition to gymnosperm of pine trees and monocots of grasses, dicots would be selected as secondary references. Brassicaceae may be a possible candidate of the reference. It includes not only vegetables such as rape but also various wild plants. It also involves arabidopsis, which is a typical model organism in plant biology with a large quantity of biological information. There are some data about radiation effects, and still more can be expected in future. - There should be another criterion for secondary references, that is the value judgment by the human society which should be open for the socio-economical stakeholder involvement and social decision-making processes. It may nominate the flagship species and/or vulnerable species instead. Flagship species are generally beautiful and charming, which appeal for the human as gvaluableh and it is essential to protect their habitats for conservation. - In Japan, Medaka fish is a flagship as a symbol for the society to purify the stream. Medaka should be also an unbrella species whose survival depends on the soundness of the ecosystem. This fish has been well studied for radiation effect and is widely used for the toxicity testing of chemicals. It is possibly used for the evaluation studies at the ecosystem level, because of its adaptability to the laboratory experiment in different systems. Medaka is a possible candidate of secondary reference fish. <Specific comments> - Both Gy day-1 and Gy h-1 are used in the text. It would be better to use just one unit. - Paragraph (3), line 5: ICRP, 2003 => ICRP, 2003a - Paragraphs (22) and (25) indicate that the objective of the reference organisms is to provide points of reference for various organisms. Therefore, applicability to assessments for different organisms should be also an important criterion for selecting reference organisms. - Paragraph (23), line 6 in page 14: EPIC => EPIC (Environmental Protection from Ionising Contaminants in the Arctic), FASSET => FASSET (Framework for Assessment of Environmental Impact) - Paragraph (32): Generalization at the level of family seems reasonable. Among species in a family, there is wide variation in radiosensitivity. It would be helpful to add an explanation about the way to treat the variation for assessment of radiation effects and for risk management. - Paragraphs (40-49): It would be helpful to add an explanation of the main sources of nutrition, including the food chain of each reference subject, to the individual description in order to understand their internal exposure (i.e., intake of radionuclides via food consumption). - Paragraphs (40-49): The status of each reference subject in the ecosystem and the relationships between them should be clearly described. - Paragraph (49): Barley type grass: It is unclear what it means. Wheat, rice and other grasses with spike (or ear) are included? - Table 1 (Use in toxicity testing): Frogs should be regarded as g+h, because these organisms are used in toxicity tests fixed by ASTM (American Society for Testing and Materials) and US EPA. - Table 3 (possible dimensions): For plants, pine and grass, only a part of their bodies are appeared in the table. In addition to trunk, needle and root are also important part of pine. It is understandable that there is almost no background data for root. However, it would be better to put needle on the table, since the part appears to be sensitive. It is also not clear the reason why only the spike appears for grass. In case of the other references, just the whole bodies are listed. - Table 3: Frog egg and pine tree trunk: Sizes of frog eggs and pine tree trunks showed in Table 3 seem to be bigger than typical ones. Flatfish egg, crab egg and crab larva: Sizes of flatfish eggs, crab egg and crab larva seem to be smaller than typical ones. Earthworm (elongated): Minor axes of earthworms showed in Table 3 seem to be longer than typical ones (0.5 cm?). - Table 3: Brown seaweed: 0-5 => 0.5 - Page 21 g3.5.10. The Reference Pine Treeh: Paragraph number is required. - Paragraph (49), line 1: Graminaea => Gramineae - Paragraph (65), line 2: gICRP, 2003ch is not in the References. - Paragraph (83), line 1: CNSC => CNSC (Canadian Nuclear Safety Commission) - Paragraph (99): It is reasonable to keep the data sets separate at this stage. However, it would be worth describing a species sensitivity distribution (SSD) concept, which is generally used for estimation of protective concentrations of chemicals. This concept was recently applied to ionising radiation, and the HDR5 (hazardous dose rate 5%; Dose rate at which 5% species might be affected but the other 95% species will be protected) was estimated as 3.48 mGy/d for aquatic invertebrates (Garnier-Laplace, J., Denison, F., Gilbin, R., Della-Vedova, C., Adam, C., Simon, O. and Beaugelin, K.: Bioavailability in ecological risk assessment for radionuclides. ECORAD 2004-IRSN Collection Series, Suppl. 1, 39, in press (2004)). - Page 35 g7.3. Creating a Reference Seth: Paragraph number is required. - Paragraph (103) and (105): Duplication - Extrapolation from one organism to another is only discussed in paragraph (108) about its difficulty. It would be better to describe the possible approach how to do it and what kind of information will be required for the extrapolations. - Paragraph (109): Mathematical modelling is important to extrapolate individual-level effects to population- or community-level effects. For example, a Dynamic Energy Budget (DEB) model (Kooijman et al.) would be useful for estimation of population-level effects, and a Comprehensive Aquatic Systems Model (CASM; Bartell et al.) would be useful for estimation of community-level effects. These models have been used for chemicals. Model ecosystem experiments would be necessary for validation of mathematical modelling. - Paragraph (109): Radiation effects on interactions among species should be discussed in some types of organisms. The changes of such interactions as ginterspecific competitionh and gallelopathyh can have a dramatic effect on the local ecosystem. When a species loses in an interspecific competition, it can lose an ecological niche and become extinct in the local area. - Page 43, line 24: Real et al.: J. Radiol. Prot. 24, A139-155 => J. Radiol. Prot. 24, A123-137. Tadaaki BAN-NAI Masahiro DOI Kenzo FUJIMOTO Shoichi FUMA Shino HOMMA-TAKEDA Nobuyoshi ISHII Yoshito WATANABE Satoshi YOSHIDA