Abstract

OBJECTIVE: Nonylphenol is a neurotoxic substance widely present in the environment. Although its neurotoxic effects are well-known, to our knowledge, the ototoxic effects of nonylphenol on hearing have not been published in the literature yet. We aimed to investigate the effect of nonylphenol on hearing function in rats. 

MATERIALS and METHODS: Fifty rats were randomly divided into five Groups each containing 10 animals. Group 1 was a control Group and Group 2 was a solvent control containing ethanol alone, whereas Groups 3, 4, and 5 were treatment Groups exposed to the different concentrations of nonylphenol dissolved in ethanol for six- weeks. Distortion product otoacoustic emission measurements were evaluated at the end of exposure.

RESULTS: In the distortion product otoacoustic emission measurement, signal-to-noise ratio values did not show any statistically significant differences between the control and ethanol Groups (p>0.05). But, we found significant differences between signal-to-noise ratio values of control and nonylphenol Groups at 4000 and 6000 Hz frequencies (p<0.05). Also, we found statistically significant difference between signal-to-noise ratio values of ethanol and nonylphenol Groups at 4000 and 6000 Hz frequencies (p<0.05). There was no statistically significant difference for signal-to-noise ratio values among nonylphenol Groups (Groups 3-5) (p>0.05). 

CONCLUSION: Our study showed that nonylphenol has negative effects on hearing function in rats but the effects do not seem to be dose-dependent. Further studies are needed to find whether nonylphenol has an effect on hearing loss in rats as well as hearing in human beings.