Physicochemical determinants of linear alkylbenzene sulfonate (LAS) disposition in skin exposed to aqueous cutting fluid mixtures

Abstract

Linear alkylbenzene sulfonate (LAS) is added to cutting fluid formulations to enhance the performance of metal machining operations, but this surfactant can cause contact dermatitis in workers involved in these operations. The purpose of this study was to determine how cutting fluid additives influence dermal disposition of 14C-LAS in mineral oil-or polyethylene glycol 200 (PEG)-based mixtures when topically applied to silastic membranes and porcine skin in an in vitroflow-through diffusion cell system. 14C-LAS mixtures were formulated with three commonly used cutting fluid additives; 0 or 2% triazine (TRI), 0 or 5% triethanolamine (TEA), and 0 or 5% sulfurized ricinoleic acid (SRA). LAS absorption was limited to less than a 0.5% dose and the additives in various combinations influenced the physicochemical characteristics of the dosing mixture. LAS was more likely to partition into the stratum corneum (SC) in mineral oil mixtures, and LAS absorption was significantly greater in the complete mixture. TRI enhanced LAS transport, and the presence of SRA decreased LAS critical micelle concentration (CMC) which reduced LAS monomers available for transport. TEA increased mixture viscosity, and this may have negated the apparent enhancing properties of TRI in several mixtures. In summary, physicochemical interactions in these mixtures influenced availability of LAS for absorption and distribution in skin, and could ultimately influence toxicological responses in skin.