The selection of parameter values in studies of environmental radiological impacts

The ERICA Tool has become widely accepted as an appropriate approach to assessing radiological impacts of environmental concentrations of radionuclides on wildlife. Although generally a comprehensive and state-of-the-art approach in this type of assessment, its treatment of uncertainty at Tier 2 is extremely limited and is not likely to be valid in the assessment contexts in which it will typically be employed. A more appropriate approach to the treatment of uncertainties is described. This leads to the conclusion that where data are lognormally distributed, it is appropriate to use the arithmetic mean of the distribution in reasonably cautious assessment calculations (as is done in the ERICA Tool) rather than to use the geometric mean, but that the uncertainty factor adopted should be larger than the range of 3 to 5 currently recommended at Tier 2 of the ERICA Tool.