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This Scientific Report was carried out in the context of the self‐task mandate (M‐2023‐00097) of the EFSA's Scientific Committee on 'Guidance on the use of biomarkers of effect in regulatory risk assessment of chemicals'. In the first phase, the project on biomarkers of effect started with a feasibility study (EFSA‐Q‐2024‐00128), with the intention to look closer at definitions and descriptions of biomarkers of effect, as well as to explore several concepts related to the context of application and other scientific principles to be further considered for its development. In addition, relevant activities, initiatives and knowledge in this area were collected and analysed within a complementary mapping study. The outcome of this phase aimed to create a structured basis for future guidance, to identify challenges and to recommend a way forward for its development. The recommendations refer especially to terminologies, the scope of the guidance and several scientific and technical aspects of the selection and interpretation of biomarkers of effect that need to be addressed in future guidance. Moreover, further recommendation refers to the collaborative process to be established with other regulatory organisations that should support the harmonisation and reduce divergencies in the application of methodologies across organisations or sectors. [ABSTRACT FROM AUTHOR]

Pesticides must not pose unacceptable risks to human health, so risk assessments are conducted before products are authorised. Dermal exposure is often the main route of intake, so estimating realistic and trustworthy dermal absorption values is crucial for risk assessment. Although there are agreed test guidelines for in vitro dermal absorption studies, not every product is tested due to cost reasons. The present dataset consists of 945 individual in vitro experiments on the dermal absorption of human skin with 179 active substances of pesticides in 353 different mixtures, including concentrates and dilutions. The dataset was evaluated to identify the possible impacts of experimental conditions and physico-chemical properties on dermal absorption. The dataset was also analysed to assess the appropriateness of the pro rata correction for untested dilutions, and the set concentration cut-off to decide on the dilution status for choosing a default value on dermal absorption. The study found that the implementation of specific guidelines improved the harmonisation of study conduct, with support for approaches such as pro rata correction and default values. Further analysis of the specific co-formulants may identify influencing factors that may be more important than the experimental variables. [ABSTRACT FROM AUTHOR]

This guidance on the assessment of dermal absorption has been developed to assist notifiers, users of test facilities and Member State authorities on critical aspects related to the setting of dermal absorption values to be used in risk assessments of active substances in Plant Protection Products (PPPs). It is based on the ‘scientific opinion on the science behind the revision of the guidance document on dermal absorption’ issued in 2011 by the EFSA Panel on Plant Protection Products and their Residues (PPR). The guidance refers to the EFSA PPR opinion in many instances. In addition, the first version of this guidance, issued in 2012 by the EFSA PPR Panel, has been revised in 2017 on the basis of new available data on human in vitro dermal absorption for PPPs and wherever clarifications were needed. Basic details of experimental design, available in the respective test guidelines and accompanying guidance for the conduct of studies, have not been addressed but recommendations specific to performing and interpreting dermal absorption studies with PPPs are given. Issues discussed include a brief description of the skin and its properties affecting dermal absorption. To facilitate use of the guidance, flow charts are included. Guidance is also provided, for example, when there are no data on dermal absorption for the product under evaluation. Elements for a tiered approach are presented including use of default values, data on closely related products, in vitro studies with human skin (regarded to provide the best estimate), data from experimental animals (rats) in vitro and in vivo, and the so called ‘triple pack’ approach. Various elements of study design and reporting that reduce experimental variation and aid consistent interpretation are presented. A proposal for reporting data for assessment reports is also provided. The issue of nanoparticles in PPPs is not addressed. Data from volunteer studies have not been discussed since their use is not allowed in EU for risk assessment of PPPs.This publication is linked to the following EFSA Supporting Publications article: http://onlinelibrary.wiley.com/doi/10.2903/sp.efsa.2017.EN-1250/full [ABSTRACT FROM AUTHOR]

Based on the "Human in vitro dermal absorption datasets" published as supporting information to the revised EFSA Guidance on Dermal Absorption, in silico models for prediction of absorption across the skin have been evaluated. For this evaluation, a systematic literature search and review was performed, identifying 288 publications describing mathematical models for prediction of dermal absorption. Eleven models potentially relevant to the regulatory assessment of pesticides and which cover a range of approaches were selected for in depth evaluation. This included three mixture models taking into account physicochemical properties of the co‐formulants such as polar surface area, hydrogen bonding or octanol‐water partition coefficients. Additional data on the pesticidal active substances and information on the composition of some of the formulations covered in the dermal absorption dataset were gathered, as these were required as input parameters for the selected models. The models were implemented with settings reflecting as much as possible realistic exposure scenarios and the experimental conditions under which the measured data were obtained. As the majority of the models predicted either maximum flux or the permeation coefficient, further combination with a model achieving translation into percentage absorption was required. This was done with and without consideration of the lag time. Only one model directly predicted percentage dermal absorption, which was a spreadsheet‐based single substance model taking into consideration several skin parameters, experimental conditions, various physicochemical properties of the active substance and the type of vehicle. Statistical analysis of model predictions revealed overall low concordance with measured values, thereby limiting regulatory acceptance. Additional analysis was performed on the results of two mixture models and the above mentioned complex single substance model which showed moderate correlation between predicted and measured data. Options to improve model performance were discussed and Bayesian random effects modelling was explored to adjust predicted percentage dermal absorption to measured data as was model combination. When taking into account observed uncertainties of predictions, one of the models may provide a Tier 2 tool to estimate dermal absorption value in the absence of adequate experimental data when the predicted values are in the range of 10 to 70%. However, further work is needed to better understand the effect of co‐formulants on dermal absorption of pesticides and to improve model predicitivity. [ABSTRACT FROM AUTHOR]