Percutaneous absorption and skin irritation of JP-8 (jet fuel)

JP-8 is the major jet fuel used by US Army and Air Force. The purpose of the present study was to investigate the percutaneous absorption of JP-8 across pig ear skin and human skin in vitro and to study the effect of JP-8 exposure on the skin barrier function and irritation in Yucatan minipigs. JP-8 spiked with 5.0 microCi of radiolabeled (14C) tridecane, nonane, naphthalene or toluene (selected components of JP-8) was used for the in vitro percutaneous absorption studies with excised pig ear skin and human skin. For in vivo studies, 250 microl of JP-8 or two of its components (toluene or nonane) was placed in a Hill top chamber(R) and affixed over the marked treatment area for 24 h. Transepidermal water loss (TEWL), skin capacitance (moisture content) and skin irritation (erythema and edema) were evaluated before treatment and at 1,2 and 24 h after removal of the patches. The components of JP-8 such as tridecane, nonane, naphthalene and toluene permeated significantly through pig ear skin and human skin and the permeation rates were found to be proportional to their composition in JP-8. The steady state flux values of tridecane across pig ear skin and human skin did not differ significantly (P>0.05). Though the steady state flux values of nonane, naphthalene and toluene were statistically different between porcine and human skin (P<0.01), the values were close considering the large variations usually observed in the percutaneous absorption studies. Application of toluene, nonane or JP-8 increased the TEWL, JP-8 being the highest (3.5 times at 24 h compared to baseline level). The skin moisture content decreased after the application of JP-8, though it was not significantly different (P>0.05) from the baseline level. JP-8 caused a moderate erythema and a moderate to severe edema. Though the edema decreased after 24 h, the degree of erythema remained about the same until 24 h. The skin irritation caused by JP-8 was greater than neat toluene or nonane. The TEWL data of toluene, nonane and JP-8 correlated well with the skin irritation data (erythema and edema). Exposure of JP-8, which contains hundreds of aliphatic and aromatic hydrocarbons, caused significant changes in the barrier function of the skin as indicated by an increase in TEWL and produced a significant erythema and edema in minipigs. Furthermore, the disruption of barrier function of skin, as indicated by increased TEWL after exposure to JP-8 might result in increased permeation of its own components and/or other chemicals exposed to skin. The present study provides further evidence that pig ear skin may be used as a model for predicting the rates of permeation of chemicals through human skin.