Abstract
Problem statement: Noise Induced Hearing Loss (NIHL) is one of the most important occupational disease in worldwide. NIHL has been found to be potentiated by simultaneous Carbon monoxide (CO) exposure. Exposure to noise plus CO is common in occupational and environmental settings. Free radicals have been implicated in cochlear damage resulting from exposure to noise and due to CO hypoxia This study examined whether N-Acetylcysteine (NAC) administration cause attenuation of Auditory Brainstem Response (ABR) threshold shifts resulting from noise exposure and noise plus CO exposure. Approach: Forty-two rabbits were divided into seven groups including control, noise+ saline, noise+ CO +saline, noise+ NAC, noise+ CO+ NAC, CO+ NAC and NAC alone. ABR was assessed before exposure, 1 hour and 14 days post exposure. Results: The administration of 325 mg kg-1 of NAC prior, following and post exposure to noise or noise plus CO recovered permanent ABR threshold shift at 1 and 2 kHz almost to the baseline and provided significant attenuation in permanent ABR threshold shift at 4 and 8 kHz in subjects which were exposed to noise but it did not block the potentiating of threshold elevation by CO exposure (extra threshold loss by combined exposure) at 4 and 8 kHz. Conclusion: NAC provides protective effect against hearing loss resulting from noise exposure and simultaneous exposure to noise plus CO.
Highlights
Excessive noise can cause many health problems in the workplace but Noise-Induced Hearing Loss (NIHL) is the most important effect of noise on the auditory system in occupational settings
The results showed that, when NAC was administered 3 days prior, following and 3 days post exposure to noise by i.p. injection (325 mg kg−1 body weight), adequate protection was provided against noise induced hearing loss and appropriate protection was provided against combined exposure-induced hearing loss in rabbits
Preliminary experiments demonstrate at least 700 ppm of Carbon monoxide (CO) exposure is required to provide more Auditory Brainstem Response (ABR) threshold elevation than the noise alone
Summary
Excessive noise can cause many health problems in the workplace but Noise-Induced Hearing Loss (NIHL) is the most important effect of noise on the auditory system in occupational settings. Applied Sci., 7 (2): 201-207, 2010 unclear but combined exposure to noise and CO is stem Response (ABR) threshold at 1, 2, 4 and 8 kHz believed to increase free radical levels in the cochlea were measured at three time points: day 1 (prior to (Fechter et al, 2002; Rao and Fechter, 2000b). The present study has been designed to test the hypothesis that injury resulting from simultaneous exposure to noise plus CO is reduced by NAC in a rabbit model. Group 2-5 were exposed to octave band noise centered at 4 kHz, 100 dB SPL, 8 h day−1 for 5 days consecutively This octave band noise was generated and controlled with a custom software program (signal software) and amplified and delivered with a computer system using Cool Edit software to two load
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