Evaluation of Surface versus Total Permethrin Content in Permethrin-Treated Clothing: Considerations for Mosquito Repellency

Abstract

Permethrin is a synthetic pyrethroid insecticide that has been used to treat military uniforms to protect personnel from pests such as mosquitoes, ticks, and lice. Permethrin-treated clothing (PTC) can also be used by the public and outdoor workers such as foresters. Pests contacting the surface of PTC may be repelled or killed, depending on exposure dose and duration of exposure. Hence, it is important to assess surface permethrin concentration of clothing for repellency and/or control. Fabric swatches prepared using two commercially available permethrin treatments (Insect Shield® and Sawyer Repellant) and one laboratory permethrin-treated fabric (4 g/L) were tested to respectively compare surface and total permethrin content using a Martindale Abrasion and Pilling Tester and an Agilent Technologies 6850 Gas Chromatograph. Findings indicate that surface permethrin content (after 1000 rubs) for Insect Shield® and Sawyer, and 4g/L permethrin groups was significantly lower than total permethrin content (P=0.011, P[less-than] 0.001, and P=0.001, respectively). The relationship between surface permethrin content (SPC) and total permethrin content (TPC) varies widely between the different treatment methods evaluated here and practical implications for this are discussed. Mosquito repellency tests indicate that Insect Shield®, Sawyer, and laboratory-treated (4g/L) permethrin fabrics showed a higher repellency rate than control (untreated) fabrics (P-values: P=0.001, P[less-than]0.0001, P[less-than]0.0001, respectively). Assessing the SPC can be correlated with the amount of permethrin that comes into contact with human skin when wearing PTC. Exposure to high concentrations of permethrin may cause rashes and increase the absorption of the pesticide into the body.