Human post-application dermal exposure to pesticides is usually measured by direct dosimetry (using exposure matrices such as clothing dosimeters, hand and face wipes) or by biomonitoring. When direct exposure data is not present, dermal exposure can be determined as a multiple of the transfer coefficient, the exposure time, and the dislodgeable foliar residues (DFR). The transfer coefficient may be thought of as the amount of treated foliage that a person contacts while performing a specific activity in a given period (usually expressed in units of cm2/hour). Dislodgeable foliar residue is defined as the pesticide residue that can be removed from both sides of treated leaf surfaces using an aqueous surfactant, and is expressed as �g/cm2. Pesticide residues dissipate from treated surfaces with time and can be predicted from regressions of DFR measured over several days following an application. While the regression allows reentry exposures to be estimated on days when sampling was not conducted, the variation in results between applications and crops has not previously been investigated. Our study focuses on how well residue dissipation curves adequately predict DFR on various days following application. The California Department of Pesticide Regulation has conducted spot sampling of DFR following multiple pesticide applications in various crops. These data are compared with dissipation studies conducted by the Department, submitted by registrants, or published in the open literature. This comparison helps to assess the confidence in reentry exposures calculated from DFR.

Predicted vs. measured dislodgeable foliar residues on crops

248th National Meeting (2014)

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