Development of a new Dislodgeable Foliar Pesticide Residue (DFR) Laboratory Method: A standardized approach to investigate factors that may influence DFR.

Dislodgeable foliar pesticide residue (DFR) is the amount of pesticide that exists on foliage after the pesticide has dried and which could dislodge to the skin or clothes of workers and so forms a key parameter for non-dietary pesticide risk assessments required for pesticide registration and safe use. DFR data in the literature is described as insufficiently reliable, limited, and encompasses statistical uncertainties. The purpose of this article is to describe a newly developed laboratory method for the estimation and quantification of DFR with an illustrative example. The lab method recapitulated available field DFR methodology but involved controlled application of droplets to leaves, and validation of the wash-off solution used to rinse off the residue from the leaf surface before the analytical quantification of the residue. A very high level of accuracy (99.7-102.1 %) and precision (±1.5%) was achieved. Residue data generated from the illustrated application of the method showed a strong normal distribution unlike the field studies. The method is deemed to be controllable, cost-efficient, and time-saving that enables the generation of more publicly available data points to allow further extrapolation between the laboratory and in-field experiments. As the proposed technique is quite rapid and could be performed within hours rather than days, this could also allow investigating multiple factors that may influence DFR, which eventually allow for a better understanding of such residue to save time, money, and resources for both the industry and the pesticide registration authorities.