Measurements of the dermal exposure to bystanders from direct off-crop drift during the application of plant protection products

We determined the dermal exposure of plant protection products containing prothioconazole (PTZ) after spraying a standard crop using a tractor-operated boom sprayer. Dermal exposure of adult and child bystanders to PTZ and its metabolite, PTZ-desthio was quantified in bystander drift studies. Exposure was greater on mannequins placed 2 m from the zero line, compared with 5 m or 8 m. When the overall boom height above the ground was the same, the relative boom and canopy heights had no impact on the spray drift, allowing pooling of data from different studies. Wind tunnel experiments were used to compare two flat fan nozzle types, which allowed dermal exposure measured in early bystander field studies using the flat fan TeeJet XR 110 03 nozzle to be adjusted using a conversion factor to reflect exposure from Hypro F110-03 nozzles. Values from studies using both flat fan nozzle types were pooled and compared with exposure using drift reduction nozzles. For the first time, 3D life-size mannequins used in field studies have shown that drift reduction nozzles exceed the EFSA-recommended 50% reduction in drift (potential exposure was reduced by 58-67%). The BREAM2 (Bystander and Resident Exposure Assessment Model) model resulted in better predictions of measured dermal exposure of PTZ equivalents than BREAM, albeit producing more conservative values for the 75th and 95th percentiles of potential dermal exposure compared to field studies (2.6-fold higher than measured values). Our results using measured potential and actual exposures indicate that the EFSA calculation of 18% protection by light clothing was too conservative.

Automated summary

This study investigated the dermal exposure of plant protection products during spraying, focusing on the impact of nozzle types on spray drift. The use of drift reduction nozzles was found to significantly reduce potential exposure, exceeding the EFSA-recommended drift reduction threshold.