LAUSR

Transdermal uptake models compliment in vitro and in vivo experiments in assessing risk of environmental exposures to semi-volatile organic compounds (SVOCs). A key parameter for mechanistic models is a chemical driving force for mass transfer from environmental media to human skin. In this research, we measure this driving force in the form of fugacity for chemicals in cosmetic cream and use it to model uptake from cosmetics as a surrogate for condensed environmental media. A simple cosmetic cream, containing no target analytes, was mixed with diethylphthalate (DEP), di-n-butylphthalate (DnBP), and butyl paraben (BP) and diluted to make creams with concentrations ranging from 0.025% to 6%. The fugacity, relative to the pure compound, was measured using solid-phase micro extraction (SPME). We found that the relationship between the concentration and fugacity is highly non-linear. The relative fugacity of the chemicals for a 2% w/w formulation was used in a diffusion-based model to predict transdermal uptake of each chemical and compared with excretion data from a prior human subject study with the same formulation. Dynamic simulations of excretion are generally consistent with the results of the human subject experiment but sensitive to the input parameters, especially the time between cream application and showering.