Evaluation of Jet Fuel and Noise-Induced Hearing Loss in Rats (Rattus norvegicus)
Final rept. Oct 2010-Oct 2013
AIR FORCE RESEARCH LAB WRIGHT PATTERSON AFB OH HUMAN PERFORMANCE WING (711TH) HUMAN EFFECTIVENESS DIR/ BIOEFFECTS DIVISION
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This study investigated whether JP-8 jet fuel contributes to hearing loss when combined with noise below the exposure limit for noise injury. Two whole body 28-day inhalation exposures were conducted to determine the combined effect of noise plus JP-8 on hearing. Both studies included control, JP-8 only, noise only, and noise JP-8 groups 10 male and 10 female rats, N20 per group. The JP-8 exposure was 1000 mgm3 and the noise dose was an 8 kHz octave band noise at 85 dB sound pressure level exposures lasted 6 hours per day, five days per week for 4 weeks. The first study used 80 Long Evans LE rats, while the second study utilized 80 Fischer 344 F344 rats. Four weeks post-exposure, LE and F344 rats exposed to noise and JP-8 separately and in combination displayed no permanent peripheral hearing impairment at JP-8 exposure levels within the range that previously showed changes in F344 rats with higher sound levels. Auditory function was not different between groups, as assessed by distortion product otoacoustic emissions DPOAE and compound action potential CAP testing of the cochlear nerve. Inner ear hair cell loss was also not affected. Peripheral JP-8 ototoxicity may depend on the presence of damaging higher dB levels of noise. However, a pilot assessment indicated a central auditory processing dysfunction i.e., impaired brainstem encoding of stimulus intensity among LE rats exposed to JP-8 alone and JP-8 with noise further research of this effect is warranted.
- Anatomy and Physiology
- Medicine and Medical Research