|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.
• 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.