Approaches to providing missing transfer parameter values in the ERICA Tool--how well do they work?

Area of Science:

• Environmental Radioactivity
• Ecological Risk Assessment
• Radiological Protection

Background:

• Concentration ratios (CRs) are crucial for the ERICA Tool, estimating transfer from environmental media to organisms.
• Many CR values in the ERICA Tool were derived using extrapolation due to data gaps.
• Existing assessment systems use similar extrapolation methods, but their performance is poorly understood.

Purpose of the Study:

• To compare CR values from the ERICA Tool's extrapolation methods with empirical data from the IAEA wildlife transfer database.
• To evaluate the conservatism of extrapolation methodologies for screening assessments.
• To provide recommendations for improving the application of extrapolation approaches in the ERICA Tool.

Main Methods:

• Comparison of ERICA Tool CR values (derived via extrapolation) with empirical data from the IAEA database.
• Analysis focused on the 95th percentile CR values to ensure conservative screening assessments.
• Evaluation of over- and underprediction by extrapolation methods across different ecosystems.

Main Results:

• Extrapolation methods do not consistently provide conservative estimates of empirical 95th percentile CRs.
• For terrestrial ecosystems, under- and overpredictions occurred with similar frequency.
• Substantial underestimations (orders of magnitude) were found in some cases across all ecosystems, compromising screening assessment integrity.

Conclusions:

• Extrapolation approaches are vital for screening assessments due to inevitable data gaps.
• Diligence is crucial when applying extrapolation methods to ensure reliable results.
• Recommendations are provided to refine the guidance for using extrapolation approaches within the ERICA Tool.