Scholarly Work - Research Centers
Permanent URI for this collectionhttps://scholarworks.montana.edu/handle/1/9236
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Item Risk assessments for the insect repellents DEET and Picaridin(2008-06) Antwi, Frank B.; Shama, Leslie M.; Peterson, Robert K. D.For the use of topical insect repellents, DEET and picaridin, human health risk assessments were conducted for various population subgroups. Acute, subchronic, and chronic dermal exposures were examined. No-observed-effect-levels (NOELs) of 200, 300, and 100 mg/kg body weight (BW) were used as endpoints for DEET for acute, subchronic, and chronic exposures, respectively. For picaridin, a NOEL of 2000 mg/kg BW/day for acute exposure and a NOEL of 200 mg/kg BW/day for subchronic and chronic exposures were used. Daily exposures to several population subgroups were estimated. Risks were characterized using the Margin of Exposure (MOE) method (NOEL divided by the estimated exposure), whereby estimated MOEs were compared to an MOE of 100. Estimates of daily exposures ranged from 2 to 59 mg/kg BW/day for DEET and 2 to 22 mg/kg BW/day for picaridin. Children had the lowest MOEs. However, none of the estimated exposures exceeded NOELs for either repellent. At 40% DEET for acute exposure, children ⩽12 years had MOEs below 100. For subchronic and chronic exposures children at ⩾25% DEET and at 15% picaridin had MOEs below 100. Therefore, we found no significant toxicological risks from typical usage of these topical insect repellents.Item Toxicity of δ- phenothrin and resmethrin to non-target insects(2009-03) Antwi, Frank B.; Petterson, Robert K. D.BACKGROUND: The susceptibility of adult house cricket, Acheta domesticus (L.), adult convergent lady beetle, Hippodamia convergens (Guérin-Méneville), and larval fall armyworm, Spodoptera frugiperda (JE Smith), to resmethrin and δ-phenothrin synergized with piperonyl butoxide (PBO) was evaluated in a laboratory bioassay procedure. RESULTS: The 1 day LC50 values for resmethrin + PBO were 23.2, 32.08 and 307.18 ng cm−2 for A. domesticus, H. convergens and S. frugiperda respectively. The 1 day LC50 values for δ-phenothrin + PBO were 26.9, 74.91 and 228.57 ng cm−2 for A. domesticus, H. convergens and S. frugiperdarespectively. The regression relationship between species mortality and concentration explained 51–81% of the variation for resmethrin + PBO and 72–97% of the variation for δ-phenothrin + PBO. The LC50 values decreased with time for these insecticides for all surrogate species. In terms of sensitivities among the insects to resmethrin + PBO and δ-phenothrin + PBO, A. domesticus was most sensitive, followed by H. convergens and then S. frugiperda. CONCLUSION: The results indicate that resmethrin + PBO was generally more toxic than δ-phenothrin + PBO. Based on the results, A. domesticus seems to be a good surrogate species for estimating potential non-target terrestrial insect impacts from exposure to pyrethroids used in public health applications.