Variability Between Datasets and Statistical Approaches—Rethinking Estimation of Default Dermal Absorption Values for Risk Assessment

In risk assessment, deriving dermal absorption values is essential for evaluating plant protection products. Applicants submit study data, which authorities assess during the authorisation process. If no data are provided, default values from the European Food Safety Authority 2017 Guidance on dermal absorption (EFSA GD2017) apply. The German Federal Institute for Risk Assessment compiled an updated dermal absorption dataset of 356 more recent human in vitro studies evaluated under to the newest guidance. We applied the same empirical and modelling approaches used to derive default values for concentrates (commercially available product concentrations) and dilutions in different formulation type categories in EFSA GD2017 to the new dataset and compared the resulting values. We also assessed the impact of applying the alternative definition of 'concentrate' (>50 g/L) according to SCoPAFF. Default values obtained by analysing the new dataset were considerably lower than current default values, particularly for solids applied in dilutions. The alternative definition of 'concentrate' did not have a large impact on default values. Our results suggest that a revision of the default values based on newer studies evaluated under the most current guidance may be warranted.