Subchronic JP-8 Jet Fuel Exposure Enhances Vulnerability to Noise-Induced Hearing Loss in Rats
AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH HUMAN EFFECTIVENESS DIRECTORATE
Pagination or Media Count:
Both laboratory and epidemiological studies published over the past two decades have identified the risk of excess hearing loss when specific chemical contaminants are present along with noise. The objective of this study 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 4-wk 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 hd, 5 dwk for 4 wk at concentrations of 200, 750, or 1500 mgm3. Parallel groups of rats also received nondamaging noise constant octave band noise at 85 dBlin in combination with the fuel, noise alone 75, 85, or 95 dB, or no exposure to fuel or noise. Significant concentration-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 mgm3 were presented with trends toward impairment seen with 750 mgm3 JP-8 noise. JP-8 alone exerted no significant effect on auditory function. In addition, noise was able to disrupt the DPOAE and increase auditory thresholds only when noise exposure was at 95 dB. In a subsequent study, male n 5 per group and female n 5 per group rats received 1000 mgm3 JP-8 for 6 hd, 5 dwk for 4 wk 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 noise, and those receiving no experimental treatment. Significant impairment of auditory thresholds especially for high-frequency tones was identified in the male rats receiving combined treatment.
- Anatomy and Physiology