Reference animals and plants

Draft document: Reference animals and plants
Submitted by Christepher McKenney, U.S. Nuclear Regulatory Commission
Commenting on behalf of the organisation

Continued - Page 2 of NRC comments The proposals for Derived Consideration Levels are important from several perspectives. These are outlined as follows: • These proposals have been made without any consensus having been developed on the particular end points of concern. While the draft report outlines some of the possible measures of environmental protection, this information does little to advance the actual discussion of what measures may be important or relevant for measuring environmental impact in various situations. The report should make it clear that defining such end points was not a goal of the document and that identifying the appropriate end points would need to be resolved before Derived Consideration Levels are established. • The proposals have been made with much uncertainty in the actual doses at which effects may occur and with minimal information on radiation effects in some reference biota. Moreover, the impacts of other confounding variables, such as temperature or chemical hazards, are not presently addressed. More work is needed to reduce these uncertainties before Derived Consideration Levels can be considered as anything more than topics of discussion. • The criteria for selecting a reference plant or animal in the report appears to be based, in part, on whether information was available on radiation effects. A more risk informed approach, whereby the influence of the reference plant or animal on the overall ecological system is considered in defining the reference biota, could be explored. • The suggested initial set of Derived Consideration Levels support the long standing assumption that protection measures established to assure adequate protection of humans provides adequate protection of animals and plants in that environment. The Derived Consideration Levels are all greater than any dose criteria used for humans. Thus, we continue to find that existing systems of control for radiation and radioactive materials are adequate for protection of the environment. We reiterate our position (last stated in our comments on ICRP Report 103) that additional standards do not need to be established to protect the environment. • An approach of utilizing Derived Consideration Levels could potentially become a useful adjunct to existing methods used for environmental impact considerations by providing additional information regarding the protection of non-human species. However, any consideration of the use of any tools or methods utilizing such an approach cannot be considered until it is fully developed. • This document is the first step in collecting and analyzing the available information for the ICRP and as acknowledged in Section 5.4, there are several data sources that have not been included in the report. Therefore, we recommend that the ICRP evaluate and discuss the results of the environmental monitoring data, and the relevant effects on the local non-human species, collected at the large nuclear sites around the world. Specific Comments • Modeling of internal exposure assumes that none of the exposure results from ingested material inside the digestive system, although paragraph 86 does mention the use of cylinders to represent animals. For some types of animals, exposure from material in the digestive system, even if not absorbed may be significant. For example, deer (terrestrial herbivores) eat leaves, which have a very high surface to volume ratio and therefore can accumulate significant quantities of contaminants on their surface. So for herbivores, the gut as an internal source may be significant. Worms may be as exposed internally through the gut due not only to their eating habits but also their geometry. An expanded discussion of the advantages of different shapes in this analysis and the sensitivity of results to the shape assumption would be helpful in or after paragraph 86. • Concentrations of Strontium-90 (Sr-90) after the Kyshtym accident (referenced in paragraph 153 and 278) appear to have an error in units. According to “Radiation Effects in Wild Terrestrial Vertebrates – the EPIC Collection” by Tatiana Sazykina and Ivan I. Kryshev in the Journal of Environmental Radioactivity, Volume 88, Issue 1, 2006, pages 11-48, the relevant concentrations of Sr-90 should be much greater than 14 becquerels per kilogram (Bq/kg) and 1 Bq/kg, cited in paragraphs 153 and 278, respectively. • It is unclear what dose (for each species) is to be compared to the tables of derived consideration levels. Should the comparison be to the reference animal/plant that receives the highest exposure, the mean or median exposure? A discussion of this would be useful in Section 6. • Section 7, “Applications and Extrapolations,” paragraph 366 argues that it seems appropriate to focus on the effects on the individual organism for the purpose of developing an ecological framework because radiation effects at the population level are mediated through the effects at the individual level. However, the discussion provided is limited. Additional discussion on the issues related to this assumption of focusing on the individual organism would be beneficial in or subsequent to paragraph 366. These issues could include the effects of low-level doses and chronic effects on individual organism behavior, population fitness and survival (perhaps with examples from nonradiological literature), the uncertainty due to paucity of data on such effects in nonhuman species and how chronic effects that alter population fitness might influence Derived Consideration Levels.