However, for protection purposes, the ICRP prefers to use the average tissue dose
. The ICRP argues that the absorbed dose (calculated at a point in tissue) is an unsatisfactory predictor of risk because it does not account for the average tissue dose
or differences in tissue radiosensitivity.
When a pharmacokinetic model is used, however, and the tissue dose
is expressed in terms of total metabolism, the dose response for toxicity becomes linear, improving the accuracy of dose-response modeling.
The expansion to the 50,000 factor seen in the mouse assays is probably associated with disparities in target tissue dose
due to differences in serum protein binding and excretion of the two chemicals in vitro and in vivo, differences that would need to be evaluated separately for humans.