Dissipation of Foliar Carfentrazone Residues after Application to a Tall Fescue Lawn and Implications for Human Exposure

Abstract

Dislodgeable foliar residues (DFR) are a primary route for human exposure after pesticide application to turfgrass areas. The portion of applied pesticide available for human exposure via dislodgeable residues depends on various factors. In this study, DFR were determined over a 15‐d period after carfentrazone application to an established stand of ‘Confederate’ tall fescue (Festuca arundinacea Schreb). Dislodgeable foliar residues were determined by wiping treated turfgrass with a distilled‐water‐dampened cheesecloth and analyzing samples using gas chromatography–mass spectrometry. Less than 20% of the applied carfentrazone (18,000 ng dm−2) was dislodged, with 13.8% dislodged immediately after application. Dislodgeable foliar residues as determined 1, 4, and 8 h after treatment contributed an additional 5.5% to the applied carfentrazone dislodged from tall fescue foliage. One day after treatment (DAT), carfentrazone dislodgeable residue levels had declined to below 1% of that applied and were nondetectable 3 DAT and after. Carfentrazone residues resulted in a maximum estimated hazard quotient <1 for the duration of the study, indicating that potential human toxicological effects associated with maximum field residue levels are unlikely. This work indicates that carfentrazone poses minimal risk to human health via dermal exposure applied per label recommendations.