3.2 Quantification of uncertainty within and between species and the role of uncertainty factors

Uncertainty and uncertainty factors (UFs) are important topics in toxicology, which likely become relevant for evidence-based toxicology (EBT). In general terms, the aim of assessing uncertainty is to evaluate the limits of our knowledge. In particular, uncertainty analysis (UA) addresses the type and extent of toxicological knowledge used, model selection, choices of modeling assumptions, statistical options during modeling, and statistical and computational assumptions during analysis (technical uncertainty). In contrast to UA, the purpose of UFs is specific, namely, to convert a defined risk-characterizing parameter into a relevant risk management or health risk guidance parameter in the presence of uncertainty.1 This article discusses uncertainty and UA methods as well as UFs and their refinement as specific tools.