Effects of Co-Exposure to Noise and JP-4 Jet Fuel on Hearing Loss in Rats

Autotoxic substances such as JP-4 jet fuel can have negative effects on the auditory system by the various means such as cochlear dysfunction. The purpose of this study was to investigate the combined effects of exposure to JP-4 jet fuel and noise on hearing loss in rats, to determine the possible interference effects of these two risk factors on rat auditory system.

For this purpose, 24 healthy adult male Wistar albino rats, weighing 230±25 g, were selected and randomly divided into four groups of six. One group was exposed only to noise with a bandwidth of 500-8000 Hz with a sound pressure level of 95± 2 dBA and the second group was exposed to JP-4 jet fuel with a concentration of 1100±10 mg / m3 for 8 hours per 14 consecutive days. The third group also experienced both noise and jet fuel exposure to the same conditions and the fourth group was also considered control. The assessment of hearing system in male rats was used by Distortion Product Otoacoustic Emissions testing (DPOAE). Changes in the temporal and permanent distortion emissions (TTSdp and PTSdp) in the frequency range of 0 to 8.5 kHz were compared between groups.

In the exposed group to noise, the level of temporary and permanent hearing loss was 6.24 and 5.35 dB, respectively. Temporary and permanent hearing loss in rats exposed to jet fuel (JP-4) was measured as 3.02 and 2.85 dB, respectively.  In the group co-exposed to noise and jet fuel, permanent and temporary hearing loss were reported being 13.43 and 12.02 dB, respectively.

The results of the present study showed that independent exposure to noise and jet fuel (JP-4) can lead to temporary and permanent hearing loss; moreover, there was the stronger effects on auditory system in co-exposure condition. The exposure to Jet fuel may increase risk for noise adverse effect on hearing loss. However, more comprehensive research is required to reveal more aspects of the interference effect of co-exposure noise with different characteristics such as level and frequency and jet fuel with different types and concentrations.