Recommended Use of Body Weight 3/4 as the Default Method in Derivation of the Oral Reference Dose presents Body Weight ¾ as the default methodology for interspecies dosimetric extrapolation for use in toxicological studies using animal data to assess effects on humans. The document lays out the scientific rationale for such an approach, the modifications to the application of interspecies uncertainty factors, and provides the methods for computing the Dosimetric Adjustment Factor to determine the human equivalent dose. This document has undergone both internal (within EPA) and external peer review and public comment. The final document reflects the comments submitted through the review process.
Historically, EPA has applied a direct cross-species extrapolation based on body weight (BW1/1) for noncancer endpoints while applying a body weight3/4 extrapolation for cancer endpoints. By modifying the scaling to BW3/4 for noncancer endpoints this document harmonizes the default methodology for assessing risks for cancer and noncancer endpoints.
