Original Article © The Author(s) 2022; All rights reserved. Published by Rafsanjan University of Medical Sciences Press. JOHE, Winter 2022; 11 (1) 67 The Concurrent Effect of Lead and Noise on Noise-Induced Hearing Loss at 4 kHz Frequency: An Experimental Study Batol Masruri 1 , Iraj Alimohammadi 2 , Jamileh Abolghasemi 3 , Parvaneh Yekzamani 4 , Azadeh Ashtarinezhad 5* 1. PhD Student in Occupational Health and Safety, Dept. of Occupational Health, School of Medical Sciences, Tarbiat Modares University, Tehran, Iran. 2. Professor, Dept. of Occupational Health, School of Public Health, Iran University of Medical Sciences, Tehran, Iran. 3. Associate Prof., Dept. of Biostatistics, School of Public Health, Iran University of Medical Sciences, Tehran, Iran. 4. MSc in Occupational Health and Safety, Dept. of Occupational Health, School of Public Health, Iran University of Medical Sciences, Tehran, Iran. 5. Assistant Prof., Dept. of Occupational Health, School of Public Health, Iran University of Medical Sciences, Tehran, Iran. Abstract Article Info Background: Hearing loss is an occupational chronic disabling and is due to complex processes of numerous risk factors such as excessive noise, ototoxic agents and aging. We aimed to examine the concurrent effect of lead and noise on rats' noise hearing function as a sub-acute exposure. Materials and Methods: In this experimental study, 40 male rats were divided into 4 groups as 1) control group 2) exposed to 105 dB noise at 4 kHz frequency 8h/day, 6day/week for 4 weeks 3) exposed to 4 mg/kg lead acetate by gavage 6day/week for 4 weeks 4) exposed to both lead and noise. Blood lead levels were evaluated by Graphite Furnace Atomic Absorption Spectrometry. In addition, before and after exposure, the auditory brainstem response (ABR) was performed to examine the hearing loss in rats. Results: The hearing threshold at noise exposure (105 dB at 4 kHz frequency) group indicated a significant increase (10 dB and 11.5 dB with click and tone burst stimuli, respectively) compared to the control group (p<0.0001). Moreover, there was a significant difference between the lead concurrent noise-exposed group and the control group regarding the latency of waveform II with both stimuli (p<0.0001). There was a positive correlation between Blood Lead Level in lead-treated rats with Auditory Brainstem Response threshold by tone burst stimulus (r = 0739, p = 0.015). Conclusion: we concluded that lead and noise have a synergistic effect and can exacerbate hearing loss. However, additional studies at various doses are needed to confirm this finding. Keywords: Hearing Loss, Lead, Heavy Metals, Noise, Blood, Auditory Brainstem Response * Corresponding author: Azadeh Ashtarinezhad, E-mail: ashtarinezhad.a@iums.ac.ir Article history Received: Oct 2021 Accepted: Jan 2022 Print ISSN: 2251-8096 Online ISSN: 2252-0902 Peer review under responsibility of Journal of Occupational Health and Epidemiology Introduction Hearing impairment is an occupational chronic disability all over the world [1, 2]. Accordingly, hearing disorders have been recommended as one of the high priority research areas of the 21st century by the National Institute for Occupational Safety and Health (NIOSH) [3]. Hearing loss is a Citation: Masruri B, Alimohammadi I, Abolghasemi J, Yekzamani P, Ashtarinezhad A. The effect of Lead and Noise on Noise-induced Hearing Loss at 4 kHz Frequency: an experimental study. J Occup Health Epidemiol 2022; 11(1):67-75. 10.52547/johe.11.1.67