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Penetration of liquid chemicals has been observed and subsequently has been studied through both in vivo and in vitro assays. Although a few chemical vapors have been studied using in vivo assays, there has been no in vitro system for permeation studies. Therefore, the purposes of this study were: (1) To develop an in vitro system for vapor permeation studies; (2) to use the system to investigate vapor permeation of benzene, n-butanol, and toluene; (3) to compare the vapor permeation of these chemicals to their liquid permeation; and (4) to compare permeation of the chemicals within phases.
Radiolabeled chemical vapors were generated by passing purified air in series through two saturators containing liquid radiolabeled chemical. The generated vapor was directed into the donor compartment of commercial liquid permeation cells modified to comprise a vapor chamber. For liquid permeation, two layers of parafilm were used to cover the donor cells to prevent evaporation of the chemical. The receptor fluid was collected serially and analyzed using a liquid scintillation counter.
The variability of the generated concentrations for each chemical over the course of each experiment was approximately 3%. The mean concentration of benzene vapor generated by the developed system was not significantly different from the theoretical concentration, but the mean concentrations of n-butanol and toluene vapors differed significantly from the theoretical concentrations.
The mean permeation rates of the liquid chemicals were significantly higher than those of their vapor phase. For vapor phase, permeations of toluene and benzene were not significantly different. The mean permeation rate of n-butanol was significantly lower than the rates of benzene and toluene. For liquid phase, the mean permeation rates of the studied chemicals were not significantly different.
The results of this study suggest that: (1) The developed vapor generator system is appropriate for in vitro study of vapor permeation; (2) For the studied chemicals it is not likely that skin exposure to vapor at the TLV (Treshold Limit Value) level represents a health hazard.