PWC tool to estimate pesticide soil concentrations for risk assessment of nontarget soil organisms

In Brazil, as of 2024, regulatory authorities are discussing establishing new guidelines for environmental risk assessment (ERA) of plant protection products (PPPs) for nontarget soil organisms. A critical aspect of this process is exposure estimates of nontarget soil organisms to PPPs. The present work investigates the potential application of the U.S. Environmental Protection Agency Pesticide in Water Calculator (PWC) modeling platform to estimate the predicted environmental concentration in the soil (PECSOIL) as an option for exposure assessments. The objective of this exercise is to investigate the practicability and adaptability of PWC within the framework of a tiered risk assessment approach in Brazil. The PWC PECSOIL values were compared with two soil residue kinetics models: the United Kingdom Health and Safety Executive (HES) PECSOIL Calculator and ESCAPE. As a validation step, PWC PECSOIL estimates were compared with measured soil residue data from two Brazilian locations. The impact of location-specific local data-soil physical-chemical properties, meteorological data, application methods, and crop parameters-on PECSOIL is also discussed, especially parameters that are inherent to PWC but absent in other soil kinetics calculators. Based on this work, we found the PWC model useful for soil exposure determination, especially when it becomes necessary to refine the exposure estimates using locally relevant conditions to bring more realism to the evaluation process.