In vitro percutaneous penetration of five pesticides--effects of molecular weight and solubility characteristics.

This study examined the in vitro percutaneous penetration of five pesticides covering a wide range of solubilities and different molecular weights, which allowed discussion of penetration of single pesticides as well as a comparison between penetration characteristics of different pesticides. The five pesticides were the fungicides methiocarb, pirimicarb and prochloraz; the growth retardant paclobutrazol; and the insecticide dimethoate. An experimental model with static diffusion cells mounted with human breast skin was used, and pesticide concentrations were quantified by high-performance liquid chromatography. Molecular weight as well as solubility affected dermal penetration and skin deposition. Thus, we conclude that for the passage of our test substances from the donor phase, through the skin, into the receptor, a too high as well as a too low lipophilicity may limit the rate and degree of skin penetration. Furthermore, the importance of the skin as a potential reservoir for systemic exposure after exposure has ended was demonstrated. Especially in relation to short-term occupational exposures, an exposure assessment based on penetrated pesticide at the end of a work shift may underestimate the exposure.