Evaluating summarised radionuclide concentration ratio datasets for wildlife

Concentration ratios (CRwo-media) are used in most radioecological models to predict
radionuclide activity concentrations in wildlife from those in environmental media. This simplistic
approach amalgamates the various factors influencing transfer within a single generic value and, as a
result, comparisons of model predictions with site-specific measurements can vary by orders of
magnitude. To improve model predictions, the development of 'condition-specific' CRwo-media values
has been proposed (e.g. for a specific habitat). However, the underlying datasets for most CRwo-media
value databases, such as the wildlife transfer database (WTD) developed within the IAEA EMRAS II
programme, include summarised data. This presents challenges for the calculation and subsequent
statistical evaluation of condition-specific CRwo-media values. A further complication is the common
use of arithmetic summary statistics to summarise data in source references, even though CRwo-media
values generally tend towards a lognormal distribution and should be summarised using geometric
statistics. In this paper, we propose a statistically-defensible and robust method for reconstructing
underlying datasets to calculate condition-specific CRwo-media values from summarised data and
deriving appropriate summary statistics. This method is applied to terrestrial datasets from the WTD.
Statistically significant differences in sub-category CRwo-media values were identified, which may
justify the use of these CRwo-media values for specific assessment contexts. However, biases and
limitations within the underlying datasets of the WTD explain some of these differences. Given the
uncertainty in the summarised CRwo-media values, we suggest that the CRwo-media approach to
estimating transfer is used with caution above screening-level assessments.