Response to Decision-Making with New Approach Methodologies: Time to Replace Default Uncertainty Factors with Data

We appreciate the opportunity to respond to Drs Rusyn and Chiu (Rusyn and Chiu, 2022) and agree with their basic premise that default uncertainty factors should be replaced with data whenever possible. Information from new assessment methods is one likely source of such data. Notwithstanding our general agreement, however, we were somewhat surprised at several statements: First, we note that Dourson et al. (2022)may be inadvertently contributing to the longstanding conflation of uncertainty and variability. We respectfully note that we did not conflate these intertwined issues. The extensive literature on uncertainty factors, spanning over four decades and with over 100 publications, some of which we cited, routinely describes the “uncertainty and variability” aspects of these factors. Figure 2 of our paper Dourson et al. (2022) was intended to show both variability and uncertainty, with two of these factors seen to reduce the projected risk due to population...