Membrane transport of naphthalene and dodecane in jet fuel mixtures

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Abstract
Jet fuels are formulated with numerous aliphatic and aromatic components that are thought to cause dermal irritation in air force personnel. However, diffusion of these components in such a complex mixture is not well understood. The purpose of this study is to evaluate the physicochemical properties of these mixtures in the context of how they influence partitioning, diffusion, and absorption of aromatic (14C-naphthalene) and aliphatic (14C-dodecane) markers in porcine skin and silastic membranes in vitro. In these 5-h flowthrough diffusion studies, Jet-A, JP-8, and JP-8(100) fuels, and weathered JP-8 (JP-8 (Puddle)) were tested. In both membrane systems and across all jet fuels tested, naphthalene absorption (1.29-1.84% dose) was significantly greater than dodecane absorption (0.14-0.28% dose). However, significantly more dodecane than naphthalene was observed in the stratum corneum (SC; 4.23-7.23% dose vs. 1.88-4.08% dose) and silastic membranes (59.2-81.7% dose vs. 30.5-36.7% dose). Naphthalene was least likely to be retained on the skin surface compared to dodecane, while this trend was reversed in silastic membranes. In porcine skin. weathered JP-8 significantly increased dodecane absorption, permeability (0.19×10−4 cm/h), and diffusivity, and also naphthalene deposition in the SC compared to other jet fuels. In contrast, weathered JP-8 appears to decrease naphthalene flux (1.56 μg/cm2/h) and permeability (1.14×10−4 cm/h) in skin. There were no differences among the three jet fuels in terms of their ability to influence naphthalene or dodecane disposition in skin and, generally, no significant differences among the four jet fuel mixtures were observed in silastic membranes. In conclusion, these transport studies suggest that absorption and deposition of naphthalene and dodecane are different when dosed in various jet fuel mixtures, and disposition in weathered jet fuel is significantly different from that in commercial and military fuels. These interactions may not only be related to the unique chemistry of these components, but also specific membrane interactions in the SC and viable epidermis.