This paper provides a bridge
between the fields of ecological risk assessment (ERA) and radioecology by presenting
key biota dose assessment issues identified in the US Department of Energy's
Graded Approach for Evaluating Radiation Doses to Aquatic and Terrestrial Biota
in a manner consistent with the US Environmental Protection Agency's framework
for ERA. Current radiological ERA methods and data are intended for use in protecting
natural populations of biota, rather than individual members of a population.
Potentially susceptible receptors include vertebrates and terrestrial plants.
One must ensure that all media, radionuclides (including short-lived radioactive
decay products), types of radiations (i.e., alpha particles, electrons, and
photons), and pathways (i.e., internal and external contamination) are combined
in each exposure scenario. The relative biological effectiveness of alpha particles
with respect to deterministic effects must also be considered. Expected safe
levels of exposure are available for the protection of natural populations of
aquatic biota (10 mGy d_1) and terrestrial plants (10 mGy d_1) and animals (1
mGy d_1) and are appropriate for use in all radiological ERA tiers, provided
that appropriate exposure assumptions are used. Caution must be exercised (and
a thorough justification provided) if more restrictive limits are selected,
to ensure that the supporting data are of high quality, reproducible, and clearly
relevant to the protection of natural populations.