Carbaryl, dermal absorption

Baynes RE, Riviere JE. Influence of inert ingredients in pesticide formulations on dermal absorption of carbaryl. AmJ Vet Res 1998 59(2) 168—75. 

Baynes at al. (1997) Rodent, pig stin DEET. permethrin, carbaryl DEET does not enhance dermal absorption of permethrin... 

Tos-Luty, S., Tokarska-Rodak, M., Latuszynski, J., and Prczcbiruwska, D. (2001). Dermal absorption and distribution of C-carbaryl in Wistar rats. Arm. Agric. Environ. Med. 8( 1), 47-50. 

Rgure 9.2 Inhibiting effects of DEET on the dermal absorption of (a) carbaryl and (b) permethrin. 

In another dermal penetration study, it was shown that the absorption of the insecticide carbaryl was enhanced by the solvent acetone and the surfactant sodium lauryl sulfate. The synergist PO significantly increased the absorption of carbaryl when added to the acetone-carbaryl rnixJ31 This study points out both the enhanced absorption of pesticide by individual inert additives as well as the further enhanced mixture effect. 

Dermal dose-ChE response and percutaneous absorption studies were conducted with parathion, carbaryl, and thiodicarb in the rat. Parathion and thiodicarb inhibited 50% of the red cell cholinesterase activity at dose levels of 3.2 and 33 mg/kg of bw. Carbaryl at the highest dose level tested (417 mg/kg of bw) produced no detectable red cell cholinesterase Inhibition. 

Thlodicarb is a new insecticide being marketed by Union Carbide as Larvin for the control of insects on cotton. Thiodicarb is metabolized in the rat to acetamide, acetonitrile, CO, methomyl, and methomyl metabolites. No illnesses have been reported among applicators or field workers coming in contact with this carbamate insecticide. Thiodicarb is somewhat more persistent on crops than methomyl and is less toxic dermally in rabbit studies. The dermal dose-CliE response study showed that a dose of 33 mg/kg produced 50% ChE inhibition 24 hr. after the application of the dose, while a dose of 87 mg/kg of thiodicarb did not produce more inhibition than a dose of 44 mg/kg. The poor solubility of this carbamate in water/lipid most likely prevented the absorption of additional quantities of thiodicarb, thereby reducing its toxicity. Thiodicarb was found in lower concentrations in skin than either parathion or carbaryl during the percutaneous absorption studies. The concentrations in plasma. 

In an in vitro percutaneous study performed on rodent and pig skin with DEBT (diethyl-m-toluamide CAS no. 134-62-3), permethrin and carbaryl results were that no permethrin was absorbed. It was believed by the authors that DEBT inhibited the absorption of permethrin (Baynes et al. 1997). Bast et al. (1997) studied the percutaneous absorption of permethrin through the isolated perfused rabbit ear. Permethrin was applied in isopropyl myristate (reference ointment) or in ethanol. The ethanol was evaporated off skin, and the skin was covered with 1.5 (w/w) methyl cellulose in water. The authors measured the appearance rates (pmol min cm ) of 3-phenoxy benzene methanol (CAS no. 13826-35-2) and 3-phenoxybenzoic acid (CAS no. 3739-38-6) in the effusate after dermal application (3.61 pmol cm of skin). No permethrin per se was found in the effusate. The metabolites were believed to be from impurities in the permethrin. From the concentration that permethrin constitutes in a pharmaceutical brand (Ambush ) and from detection limits. Bast et al. (1997) calculated a Kp of 2.63 x 10 cm h . ... 

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