Dose Setting for Dermal Absorption Studies on Dried Foliar Residues

Abstract

Currently, the standard approach to estimate systemic exposure of workers after contact with dried pesticide residues on crops during re-entry activities relies on using the highest identified dermal absorption value for aqueous spray dilutions. However, recent dermal absorption studies with dried residues and their respective in-use dilutions have shown that this is likely to significantly overestimate their dermal penetration potential and, thus, predicted systemic exposure. The choice of appropriate dose levels for these dermal absorption studies has not been defined. Moreover, actual skin loading during re-entry tasks may differ significantly from that achieved by applying a fixed volume of an aqueous dilution, which is the standard practice in generic dermal absorption studies. To address this, we propose an approach to dose setting for dried residue studies within the current European risk assessment framework. Skin loading for studies can be calculated from the existing exposure algorithms and by taking appropriate body surface areas into account. Thus, skin loading in studies will vary depending on the exact nature and duration of the task and the region of the body exposed, reflecting actual exposure scenarios.

A new conceptional model for deriving average dermal absorption estimates from studies with multiple tested concentrations for non-dietary risk assessment of pesticides

“…This is also considered in exposure models, e.g. , the European worker re-entry risk assessment and could be used to determine relevant doses for dermal absorption testing (Morgan et al 2020 ). Accordingly, assuming dermal absorption estimates for low doses and thus extrapolating the dermal absorption assay skin dose to an exposure scenario with higher locally defined doses will rarely result in realistic risk estimates, but conversely likely overpredict risk.…”

“… It simplifies exposure estimation as the in-use dilution sprayed in a scenario can be disregarded—the in-use dilution concentration is often not relevant for risk assessment, e.g. , for re-entry scenarios and designing exposure-driven dermal absorption studies might be challenging (Morgan et al 2020 ). Uses with dilutions outside of the tested range can be assessed without generating new dermal absorption data.…”

“…This results in unrepresentative assessments, for example for re-entry workers. While corresponding dermal absorption tests can be adapted for re-entry scenarios (Aggarwal et al 2019 ; Morgan et al 2020 ), those are rather complex and depend on the specific exposure scenario.…”