Table 4.

Hierarchy of model structures for dosimetry and extrapolation (US EPA, 1994).

Hierarchy of model structures for dosimetry and extrapolation
“Optimal” or preferred model structure
Structure describes all significant mechanistic determinants of chemical disposition, toxicant-target interaction, and tissue response Uses chemical-and species-specific parameters Dose metric(s) are described at level of detail commensurate to toxicity data
Default model structure
Limited or default description of mechanistic determinants of chemical disposition, toxicant-target interaction, and tissue response Uses categorical or default values for chemical and species parameters Dose metric(s) are described at generic or categorical level of detail