Evaluation of Jet Fuel Induced Hearing Loss in Rats

Abstract

Abstract : The objective of the current work was to evaluate the potency of JP-8 jet fuel to enhance noise-induced hearing loss (NIHL) using inhalation exposure to fuel and simultaneous exposure to either continuous or intermittent noise exposure over a 28 day exposure period using both male and female Fischer 344 rats. In the initial study, male (n=5) and female (n=5) rats received inhalation exposure to JP-8 fuel for 6 hr/day, 5 days/week for 28 days at doses of 200 mg/m3, 750 mg/m3, and 1500 mg/m3. Parallel groups of rats also received non-damaging noise (constant octave band noise at 85 dBlin) in combination with the fuel, noise alone (75, 85, and 95 dB), fuel alone (200 mg/m3, 750 200 mg/m3, and 1500 mg/m3) , or no exposure to fuel or noise. Significant dose related impairment of auditory function measured by distortion product otoacoustic emissions (DPOAE) and compound action potential (CAP) threshold was seen in rats exposed to combined JP-8 plus noise exposure when JP-8 levels of 1500 mg/m3 were presented with trends toward impairment seen with 750 mg/m3 JP-8 + Noise . JP-8 alone had no effect on auditory function. In a subsequent study, male (n=5) and female (n=5) rats received 1000 mg/m3 JP-8 for 6 hr/day 5 days/week for 28 days with and without exposure to 102 dB octave band noise that was present for 15 min out of each hour (total noise duration 90 min). Comparisons were made to rats receiving only JP-8, only noise, and those receiving no experimental treatment. Pronounced impairment of auditory thresholds especially for high frequency tones were identified in the male rats receiving combined treatment.