Guidance document on evaluating and expressing uncertainty in hazard characterization, 2nd ed

Overview

For ethical reasons, the potential health effects associated with exposure of humans to toxic substances cannot normally be assessed directly in a planned experimental setting. Instead, the process of evaluating human health effects usually needs to rely on data that are only indirectly relevant. For instance, the data may relate to another species, to an exposure scenario that differs from the one applicable to humans or to a specific subpopulation of humans with many interindividual differences, apart from exposure to the chemical of interest. Therefore, the process of evaluating human health effects as a function of (potential) exposure, denoted as hazard characterization, necessarily involves uncertainties associated with extrapolating indirectly relevant results to humans. Ignoring these uncertainties may lead to incomplete risk assessments as well as suboptimal decision-making and risk communication. Risk assessors have to take uncertainty explicitly into account. Effective risk management does not require the elimination of uncertainty; rather, it requires that any such uncertainty has been made visible and taken into consideration.