Permethrin persistence

Ismail, B.S. and Kailasam, K., Measurement and prediction of permethrin persistence in six Malaysian agricultural soils, Aust. J. Soil Res., 40, 817, 2002. 

Schimmel SC, Gamas RE, Patrick JM, et al. 1983. Acute toxicity, bioconcentration and persistence of AC 222,705, benthiocarb, chlorpyrifos, fenvalerate, methyl parathion and permethrin in the estuarine environment. J Agric Food Chem 31 104-113. 

The agent of choice for scabies is permerthrin 5% (Elimite) cream. Alternative agents in subjects who cannot use permethrin are crotamiton 10% (Eurax) and oral ivermectin (Stromectal) 200 mcg/kg as a single dose. To initiate the treatment with permerthrin, the skin should be scrubbed in a warm soapy bath to remove the scabs. The permerthrin lotion should then be applied to the whole body, avoiding the face, mucous membranes, and eyes, and left on for 8 to 14 hours. A single application eradicates 97% of scabies. All close contacts should be treated appropriately. The pruritus associated with scabies may persist for 2 to 4 weeks because of the remnants of mite parts in the skin. 

Yoo, J.Y. and K.R. Solomon. 1981. Persistence of permethrin, atrazine and methoxychlor in a natural lake system. Canad. Tech. Rep. Fish. Aquat. Sci. 1151 164-167. 

Marei, A.E.M., L.O. Ruzo, and J.E. Casida. 1982. Analysis and persistence of permethrin, cypermethrin, deltamethrin, and fenvalerate in the fat and brain of treated rats. Jour. Agricul. Food Chem. 30 558-562. 

Gambrell et al. [223] have discussed the recovery of DDT, Kepone and Permethrin added to soil suspensions incubated under controlled redox potential and pH conditions to determine the effect of time on the levels of the insecticides and their degradation products. Samples were analysed by gas chromatography, pH and redox potential affected the persistence of pesticides to different degrees. The recovery of DDT was affected by redox potential but not by pH. 

Permethrin is toxic to Pediculus humanus, Pthirus pubis, and Sarcoptes scabiei. Less than 2% of an applied dose is absorbed percutaneously. Residual drug persists up to 10 days following application. 

The persistent pyrethroids such as permethrin, cypermethrin, cyfluthrin, and fenvalerate are effective mothproofing agents when applied as spot treatments from ready to use (RTU) formulations. Sodium fluosilicate [16893-85-9] is an effective mothproofing agent used at 0.5 to 0.7% in water solution with 0.3% potassium aluminate and 0.03% oxalic acid, and applied to fabrics by spraying or dipping. It is not removed by dry cleaning. 

In laboratory microcosms, ira 5-permethrin was selectively degraded compared to the other diastereomer, cw-permethrin, by six bacterial strains [19]. These strains also preferentially biotransformed 15-cw-bifenthrin over their antipodal l/ -cw-enantiomers, which were more toxic to daphnids [19]. Enantioselectivity was more pronounced for cw-permethrin than for cw-bifenthrin, and was strain-dependent. The (—)-enantiomer of both pyrethroids was preferentially depleted in sediments adjacent to a plant nursery, suggesting that in situ microbial biotransformation was enantioselective [20]. Although all enantiomers of permethrin were hydrolyzed quickly in C-labeled experiments in soils and sediments, the degradates of both cis- and irara-permethrin s -enantiomers were mineralized more quickly than those of the 5-enantiomer, while degradation products of cA-permethrin were more persistent than those of the trans-isomex [185]. Enantioslective degradation of fenvalerate in soil slurries has also been reported [83]. These smdies underscore how enantiomer-specific biotransformation can affect pyrethroid environmental residues, the toxicity of which is also enantiomer-dependent [18-20]. 

Permethrin is of low to moderate persistence in the soil (half-life of 30-38 days). Permethrin is readily degraded in most soils except those rich in organic matter, with microbial degradation predominant. Permethrin is tightly adsorbed to soil with little leaching and low mobility. Permethrin degrades rapidly... 

Prior to the advent of DDT and the organophosphates, the natural pyrethrins (32.33) found considerable use but were limited by their instability. The discovery of permethrin by Michael Elliot (3 4) proved a turning point for the new synthetic pyrethroids. Here were very active compounds that did not suffer from the stability problems of the natural compounds. And even now pyrethroid-like compounds continue to interest synthetic chemists due to their high insecticidal activity and relatively low mammalian toxicity. You would think that by now most of the very active compounds would have been found. but it seems that persistence and originality pay off. Workers at du Pont and FMC detail the structure-activity relationships for two groups of new pyrethroid-like compounds. Chemists at Dow reveal some of the intricacies in the synthesis of the cyclopropane carboxylate end of the molecule. 

PBO is now added to commercial termite formulations based on permethrin in Japan. The PBO performs two functions firstly, it acts as a solvent so that unacceptable volatile solvents are excluded from treatments applied on or near dwelling houses and secondly, it acts as an effective but also very persistent synergist, since anaerobic conditions apply where the permethrin is impregnated in wood (see Chapter 6, this volume). 

Permethrin (1% to 5 %) for pediculosis and scabies is the preferred agent and remains the safest agent, especially in infants and children. One application of permethrin is consistently effective in eradicating more than 90% of all infections. However, pruritus may persist for 2 to 4 weeks because of the remnants of mite parts in the skin. 

Derivatives of chrysanthemic acid such as (H ,3f )-permethrinic acid 143 are in demand for the manufacture of highly specific insecticides that do not persist in the environment. Mixtures of the esters 142 are easy to make and contain various proportions of the cis and trans diastereoisomers. Pig liver esterase accepts only the trans esters as substrates so complete hydrolysis gives the unchanged cis esters and hydrolysed but poorly resolved trans acids. At 50% conversion, kinetic resolution of the trans esters occurs.36... 

Schimmel, S.C., R.L. Gamas, J.M. Patrick, Jr, and J.C. Moore. Acute Toxicity, Bioconcentration, and Persistence of AC 222,705, Benthiocarb, Chlorpyrifos, Fenvalerate, Methyl Parathion, and Permethrin in the Estuarine Environment, J. Agric. Food Chem., 31(1) 104-113 (1983). 

In the last century, the development of organophosphorus, carbamate, and organochloride insecticides was followed by synthetic pyrethroids. As a result, pyrethroids are now used frequently in the domestic milieu. Pyrethroid insecticides are synthetically derived from the molecular structure or sharing the same mechanism of action of natural pyrethrins that have broader spectmm of activity, more stability, and residual activity (persists longer than that of natural pyrethrins) and include the following allethrin, cyfluthrin, cyhalothrin, cypermethrin, deltamethrin, fenvalerate, flumethrin, fluvalinate, tau-fluvalinate, and permethrin (see structure in Fig. 137.2). They are lipophilic compounds and generally of low acute oral toxicity to mammals but are very toxic to aquatic organisms. When synthetic pyrethroids are administered to mammals parenterally, the synthetic pyrethroids are neurotoxic. 

Olyset nets which have been used daily in Tanzania for 7 years were randomly collected through WHO and analyzed for permelhrin.. Results indicated that the average persistence of permethrin in the collected nets was 42.0% (Table V). 

The effect of washing fabric on the persistence of permethrin (Figure 17.2) has been shown in Thailand, " Australia, United States, and recently in Europe. Permethrin treatment of military uniforms has been used by U.S. and coalition forces, including Australia, for the last 18-20 years. The first field evaluations showed freshly treated unwashed uniforms in combination with the application of deet to the exposed skin provided the best protection against mosquitoes. i Treatment of U.S. battle dress uniforms (BDUs) and Australian Disruptive Pattern Combat Uniforms was achieved initially by dipping or spraying in a water/permethrin emulsion. The U.S. BDUs are also... 

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