ToxSci Advance Access published online on May 4, 2007
Toxicological Sciences, doi:10.1093/toxsci/kfm101
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Published by Oxford University Press 2007.
JP-8 Jet Fuel Can Promote Auditory Impairment Resulting From Subsequent Noise Exposure in Rats
1 Loma Linda VA Medical Center, Loma Linda CA 92357 2 The University of Georgia 3 CE-CERT, University of California, Riverside 4 Loma Linda University School of Medicine
Corresponding author: Laurence Fechter, Research Service (151), Loma Linda VA Medical Center, 11201 Benton Street, Loma Linda, CA 92357, Larry.fechter{at}med.va.gov
Received February 28, 2007; revision received April 20, 2007; accepted April 20, 2007
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Abstract |
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We report on the transient and persistent effects of JP-8 jet fuel exposure on auditory function in rats. JP-8 has become the standard jet fuel utilized in the United States and NATO countries for military use and it is closely related to Jet A fuel which is used in US domestic aviation. Rats received JP-8 fuel (1000mg/m3) by nose-only inhalation for 4 h and half of them were immediately subjected to an octave band of noise (OBN) ranging between 97-105 dB in different experiments. The noise by itself produces a small, but permanent auditory impairment. The current permissible exposure level (PEL) for JP-8 is 350mg/m3. Additionally, a positive control group received only noise exposure, and a fourth group consisted of untreated control subjects. Exposures occurred either on 1 day or repeatedly on 5 successive days. Impairments in auditory function were assessed using distortion product otoacoustic emissions (DPOAE) and compound action potential (CAP) testing. In other rats, tissues were harvested following JP-8 exposure for assessment of hydrocarbon levels or glutathione (GSH) levels.
A single JP-8 exposure by itself at 1000mg/m3 did not disrupt auditory function. However, exposure to JP-8 and noise produced an additive disruption in outer hair cell function. Repeated 5-day JP-8 exposure at 1000mg/m3 for 4 h produced impairment of outer hair cell function that was most evident at the first post-exposure assessment time. Partial though not complete recovery was observed over a 4 week post exposure period. The adverse effects of repeated JP-8 exposures on auditory function were inconsistent, but combined treatment with JP-8 + noise yielded greater impairment of auditory function, and hair cell loss than did noise by itself. Qualitative comparison of outer hair cell loss suggests an increase in outer hair cell death among rats treated with JP-8 + noise for 5 days as compared to noise alone. In most instances, hydrocarbon constituents of the fuel were largely eliminated in all tissues by 1 h post-exposure with the exception of fat. Finally, JP-8 exposure did result in a significant depletion of total glutathione that was observable in liver with a non-significant trend toward depletion in the brain and lung raising the possibility that the promotion of noise-induced hearing loss (NIHL) by JP-8 might have resulted from oxidative stress.
Key Words: JP-8; jet fuel; auditory function; ototoxicity; inhalation exposure; rats.
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