Estimating the biological half-life for radionuclides in homoeothermic vertebrates: a simplified allometric approach

The application of allometric, or mass-dependent,
relationships within radioecology has increased with the
evolution of models to predict the exposure of organisms
other than man. Allometry presents a method of addressing
the lack of empirical data on radionuclide transfer and
metabolism for the many radionuclide–species combinations
which may need to be considered. However, sufficient data
across a range of species with different masses are required to
establish allometric relationships and this is not always
available. Here, an alternative allometric approach to predict
the biological half-life of radionuclides in homoeothermic
vertebrates which does not require such data is derived.
Biological half-life values are predicted for four radionuclides
and compared to available data for a range of species.
All predictions were within a factor of five of the observed
values when the model was parameterised appropriate to the
feeding strategy of each species. This is an encouraging level
of agreement given that the allometric models are intended to
provide broad approximations rather than exact values.
However, reasons why some radionuclides deviate from what
would be anticipated from Kleiber’s law need to be determined
to allow a more complete exploitation of the potential
of allometric extrapolation within radioecological models.