The ICPPE initiative: development of default dermal absorption values for use in conjunction with a new global operator exposure model for pesticides

The new International Center for Personal Protective Equipment (ICPPE) operator exposure tool, like tools used in Europe and the United States, relies on passive dermal dosimetry exposure data to support risk assessment for the professional use of pesticides via handheld spraying equipment in regions where locally appropriate safety tools have been lacking. The objective of this study was to derive dermal absorption values for use with the tool when substance-specific data are unavailable. Using a database of 680 human in vitro studies covering 23 formulation types and 217 active ingredients, 4 statistical models were applied to derive fixed percentage absorption values for concentrated and diluted pesticide formulations. Furthermore, individual linear dose-absorption equations were generated based on the statistical relationship between applied dose and absorbed dose per µg/cm2 for the same formulation groups. As fixed percentages of the applied dose, 75th percentile values for concentrated products were 2.2% and 1.2%; for spray dilutions 1.0% and 24%; for solvent-based, water-based and solids 13% and 15%, respectively. Corresponding 95th percentile values for concentrates were 8.3%, 6.0%, and 3.8%; for spray dilutions 58%, 38%; and 41% for solvent-based, water-based and solids, respectively. The resulting fixed percentage defaults provide robust values for conventional use within the ICPPE tool. The alternative dose-based approach incorporates dose-based absorption properties and allows the implementation of the current dataset in future iterations of the risk assessment tool, in alignment with the novel modular dermal exposure prediction model (MODEXMO) concept.