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An assessment of field worker exposure, mixer-applicator exposure and off-target drift of chemigated insecticides

Matthew Emmett Byers, University of Nebraska - Lincoln

Abstract

Estimated dermal and respiratory exposures of workers in chemigated corn to carbaryl, chlorpyrifos, and permethrin decreased as re-entry interval increased. Dermal exposure was primarily confined to the hands. Based on these data, insecticide impregnable gloves are recommended for workers. Carbaryl and permethrin were not detected in air and chlorpyrifos was below 0.2 $\mu$g/1 (ACGIH 1989). Estimated respiratory exposures were below 0.013 mg/kg/day. By 24 h, all chlorpyrifos estimated margins of safety were greater than 10-fold, and carbaryl and permethrin exceeded 10-fold at 2 h indicating the risk of sub-lethal toxicity was low. Based on the estimated percentages of acute toxic dose data (all $<$ 0.00033%), the risk of acute toxicity to workers at any interval was low. Estimated dermal exposure of a mixer-applicator to the aforementioned treatments was primarily confined to hands, but other body regions were also exposed. High wind increased dermal exposure. For all treatments, estimated respiratory exposures were below 1.0% of dermal. All estimated percentages of acute toxic dose were beneath 0.032%, and indicated a low risk of acute toxicity. Based on the estimated margins of safety for permethrin and carbaryl (162 and 350, respectively) the possibility of sub-lethal toxicity was low, but all chlorpyrifos margins were $<$1.0, indicating the need for caution. Based on these data, protective outerwear including insecticide impregnable gloves are recommended for applicators. Chemigation of chlorpyrifos, permethrin and carbaryl resulted in insecticide drift and mean levels of drift during application were 680.0, 21.2 and 25.7 ng/cm$\sp2$, respectively, which exceeded post-application amounts of 109.6, 0.0, and 0.7 ng/cm$\sp2$, respectively. During application, detected drift was reduced to trace amounts ($<$20.4 ng/cm$\sp2$) by 24 m downwind. During this study, gauze surfaces were preferable to smooth glass for drift monitoring. Chlorpyrifos chemigated with and without crop oil was detected 100.0 m (maximum distance monitored) downwind (13.0 and 0.3 ng/cm$\sp2$, respectively). Crop oil increased drift detected on gauze. Maximum estimated dermal exposure to chlorpyrifos downwind from chemigation was 0.04 mg/kg. The estimated risk of acute toxicity was low.

Subject Area

Entomology|Environmental science|Agricultural engineering|Public health

Recommended Citation

Byers, Matthew Emmett, "An assessment of field worker exposure, mixer-applicator exposure and off-target drift of chemigated insecticides" (1990). ETD collection for University of Nebraska-Lincoln. AAI9030111.
https://digitalcommons.unl.edu/dissertations/AAI9030111

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