Evaluating Brazil's Tiered Approach for Estimating Pesticide Exposure to Soil-dwelling Organisms

Brazil's 2023 implementation of mandated ERA frameworks for pesticide registration requires the development of exposure assessment methodologies for soil organisms relevant to local conditions. This Brief Communication evaluates exposure assessment approaches within Brazil's ERA framework, comparing an ESCAPE Climate specific standard local worst-case scenario with locally developed crop-specific scenarios for high-tier exposure tools. Local scenarios were developed by the Brazilian authority for pesticide registration agency (i.e., IBAMA). We analyzed ten pesticides using a tiered approach, beginning with ESCAPE Climate screening and progressing to the USEPA PWC model for higher-tier refinement. Soil exposure was assessed at different depths (i.e., 5 and 10 cm) for earthworms, collembola, and soil microorganisms, incorporating both constant and variable temperature conditions. Initial screening using IBAMA's tier 1A standard scenario showed that temperature variability significantly influenced PECSOIL values, with differences up to 17% between constant and variable conditions.Most of the pesticides failed the risk assessment at this stage. Local scenario development using crop-specific parameters in both ESCAPE Climate and PWC demonstrated refined exposure estimates, with PWC generally producing lower PECSOIL values due to more comprehensive environmental fate mechanisms being considered. This study highlights the importance of incorporating local scenarios and appropriate refinement tools in regulatory risk assessment schemes for soil organisms, particularly for tropical agricultural conditions. The findings support a tiered exposure assessment framework that balances conservative screening with realistic refinement options for Brazilian agricultural conditions.