Re-evaluation of the Brigg’s plant uptake model for predicting nectar and pollen residues for soil applied systemic compounds

In US EPA risk assessment process for pollinators, for soil applications of crop protection products, the Tier I method for estimating exposure involves the use of a modified Briggs’ soil‐plant uptake model (Briggs et al. 1982, 1983), which is designed to estimate pesticide concentrations in plant shoots. These estimated concentrations in plant shoots are then used as a surrogate for concentrations in pollen and nectar. The use of the modified Brigg’s model equation has served as the tier I screen estimate for soil
treatments in BeeREX with the idea that this method would be re-evaluated once a considerable pollen and nectar residue dataset becomes available. In the last few years, a substantial amount of pollen and nectar residue data, particularly for the neonicotinoid class of insecticides, has been generated, including residues resulting from soil applications. Therefore, now seems an appropriate time to re- evaluate this approach using field generated data. It is also timely to review the literature to identify
additional modeling tools, including the Briggs model, that are available to predict pollen and nectar residues and whether these mechanistic modeling approaches based on chemical specific parameters are appropriate in predicting residues for soil application of systemic pesticides or, instead, rely exclusively on available empirical data.