EPA has published its guidance on using Quantitative Data to Develop Data-Derived Extrapolation Factors for Interspecies and Intraspecies Extrapolation. This document lays out methods for calculation of factors compensating for the application of animal toxicity data to humans (interspecies) and for compensating for sensitive populations (intraspecies). The use of data to conduct these extrapolations rather than rely on default values advances EPA’s policy of considering relevant data first when conducting its chemical assessments.

EPA’s guidance is available here.