Correlation between dietary and dislodgeable foliar (DFR) crop residues decline data; A proposed approach to refine non-dietary risk assessment

Pesticide residues in crop plants are routinely measured in an edible commodity or in feed items to determine safe use. Pesticides present as dislodgeable foliar residues (DFR) are measured for use in non-dietary risk assessments where worker, resident and bystander re-entry may lead to contact with the treated foliage. Possible correlations between dietary and DFR residue decline have been investigated considering data from 177 dietary residue trials along with 56 DFR trials from outdoor studies on the same crops besides residue decline data available in the Plant Properties Database (PPDB).The residue studies proved to follow the non-normal distribution and the comparison between DT50 of both types of residues for all the active substances revealed higher numerical DT50 mean values of the dietary residue compared to the DFRs. The dissipation from dietary residue studies is slower with a higher population mean compared to the mean for DFR studies for most active substances studied. A DT50 value from dietary residue studies could potentially act as a conservative surrogate DT50 for DFR which could be useful in determining the length of DFR studies and benefit both the agrochemical industry and the regulatory bodies in supporting non-dietary pesticide risk assessment.