Enhanced Skin Absorption and Fly Toxicity of Permethrin in Emulsion Formulation

Abstract

In the course of developing new formulations for fly control, we examined the skin disposition of insecticide permethrin, using excised pig skin and evaporation/penetration cells. This model has been shown to be predictive of human skin absorption (Reifenrath et al. 1984;Reifenrath and Hawkins 1986). Since permethrin formulations are intentionally applied to the skin of livestock, we also studied the disposition on cattle skin using similar methods. In many cases, dermal absorption studies of pesticides are conducted in simple solvents, such as acetone or ethanol (Shah et al. 1987), and may not be representative of skin absorption from other types of vehicles. Dust formulations of pesticides are frequently used for fly control in livestock. Emulsifiable concentrates (EC) are diluted and water and the resultant emulsion is applied as space sprays to inanimate surfaces as well as to livestock. Therefore, we determined the evaporation and skin penetration characteristics of permethrin in ethanol solution, clay dust (cattle skin only), and emulsion vehicles. Since the evaporation and skin penetration properties of the insect repellent N,Ndiethyl-m-toluamide or DEET have been extensively studied, we included this compound in our study for reference purposes.Finally, as a parallel to the skin absorption measurements, we examined the knock-down ability of permethrin formulations against house flies. Formulations which enhanced mammalian dermal absorption may also have enhanced insect absorption and toxicity. Materials and Methods[ 14 C-carbonyl]N,N-diethyl-m-toluamide was originally synthesized by New England Nuclear, Boston, MA and repurified by Moravek Biochemicals, Brea, CA. [ 14 Cbenzyl ring UL] cis, trans permethrin (cis/trans ratio 46/ 49) was obtained from Sigma, St. Louis, MO. Technical grade permethrin (97%, cis/trans ratio 43/57), and permethrin in emulsifiable concentrate (Permethrin 10% EC 2784) were obtained from McLaughlin Gormley King Co. (MGK), Minneapolis, MN. Permethrin analytical standard (cis/trans 46/52) was obtained from Chem Services, West Chester, PA. N,N-diethyl-m-toluamide (97%) was obtained from Sigma-Aldrich, Milwaukee, WI. All other chemicals/solvents were of reagent grade.Radiochemical purities were determined by HPLC/ radiometric flow detector by the manufacturer (95% for permethrin, 99.3% for DEET) and similarly re-determined in-house at the conclusion of this study (95% for permethrin in EC, 100.3% for DEET in ethanol solution). HPLC conditions for permethrin analysis were as follows: the solvent methanol:water (85:15) was pumped under isocratic conditions through a C18 column (Discovery C18, 15 cm · 4.6 mm, 5 l) using a Spectra Physics SP8800 pump. Column effluent was monitored at a wavelength of 254 nm. The UV monitor output was processed with a PC using Turbochrome software (Perkin Elmer). A Perkin Elmer NCI 900 was used to interface the monitor with the PC. A Spectra-Physics SP8780XR auto sampler with an Alltech 500 lL sample loop was used to inject 25 lL samples onto the column. Und...

Estimation of the Percutaneous Absorption of Permethrin in Humans Using the Parallelogram Method

“…The human skin results for permethrin are consistent with a previously published value (Reifenrath, 2007;2.7% for excised pig skin at 40 µg/cm 2 permethrin) and show a relatively low and constant percent absorption over the dose range relative to U.S. EPA's previously assumed value of 15%. Results are further validated by the rat in vivo absorption of permethrin, which fell within the range of values published previously by Shah et al (1987).…”

Dermal Exposure Associated with Occupational End Use of Pesticides and the Role of Protective Measures

“…Liquid formulations are generally more hazardous than solid state products because it is more difficult for a solid to pass through the skin or mucous membrane [7]. Acute health effects may include irritation of skin or eyes or respiratory irritation.…”

Effect of Propolis Preparations on Transepithelial Electrical Potential, Resistance, and Ion Transport in In Vitro Study

“…From 16 chemical substances classified as irritant for rabbits' skin, five were significantly irritant for the same human tissue. Reinferath et al [43] suggest that with hair density growth in animals, permeability of tissues also increases. Our study suggests that human skin has lower transepidermal permeability for xenobiotics in comparison to skin fragments excised from abdominal surface of experimental animals [43].…”

“…Reinferath et al [43] suggest that with hair density growth in animals, permeability of tissues also increases. Our study suggests that human skin has lower transepidermal permeability for xenobiotics in comparison to skin fragments excised from abdominal surface of experimental animals [43]. Influence of preparation containing propolis on electrophysiological parameters rabbit skin is a referential model to specify the influence on electrophysiological parameters of human skin considering existing interspecific differences.…”