Abstract for Poster 39

 

 

A description of the dermal absorption of aromatic and aliphatic hydrocarbons in jet propulsion fuel 8

D.Kim, L.A. Nylander-French*
Department of Environmental Sciences, School of Public Health, University of North Carolina at Chapel Hill, Chapel Hill, United States

Background

Jet Propulsion Fuel 8 (JP-8) is the single largest source of chemical exposure on military bases. JP-8 contains chemicals that are less volatile than previous jet fuels used by the military. Also, it does not contain the lower molecular weight compounds found in gasoline.  Human exposure to JP-8 occurs predominately via inhalation, but the dermal route has recently been implicated as a significant contributor. However, the characterization and quantification of how quickly JP-8 is absorbed by the human skin in vivo is poorly understood. The objective of this study is to mathematically model the process of dermal absorption of aromatic and aliphatic components of JP-8.

Methods

A two-compartment model of the skin (i.e. the stratum corneum and the viable epidermis) is built upon previously published inhalation models for naphthalene and decane. Simulation results of the mass of naphthalene, 1-methyl naphthalene, 2-methyl naphthalene, n-decane, n-undecane, and n-dodecane in the stratum corneum are compared to experimental data. Experimental data came from a laboratory study of human dermal exposure to JP-8.  In this study, the forearms of human volunteers were placed in a chamber and 1 ml of JP-8 was applied for 30 min to two sites with an area of 10 cm² per site. At the end of the 30 min exposure, the two sites were tape-stripped up to 10 times.

Results

The model predicts the rate of absorption into the skin for aliphatic compounds as n-decane > n-undecane > n-dodecane and for aromatic compounds as naphthalene > methyl naphthalene. These are qualitatively similar to results from the human dermal exposure study; however, the amounts absorbed as predicted by the model are inconsistent with the tape-strip data. Sensitivity analysis for the mass of each compound in the stratum corneum identified the parameters body weight, transfer coefficient from stratum corneum to viable epidermis, transfer coefficient from viable epidermis to stratum corneum, and partition coefficient for the viable epidermis to blood as most sensitive for both aromatic and aliphatic compounds. The partition coefficient for the vehicle to the stratum corneum was sensitive only for aromatic compounds.

Conclusions

This study demonstrates that mathematical models, which incorporate the biology of the skin, both with regard to function and structure, are valuable tools for making reasonable estimates of the amount of jet fuel components taken up by the skin. However, the amounts absorbed into the skin may be incorrectly predicted and, thus, optimization of the model parameters for the compound of interest is required.

Content last modified: 18 May 2005