en Occupational Health Original Article <div style="text-align: justify;"><span style="font-size:12px;"><span style="font-family:Arial;"><span style="line-height:250%"><b><span style="color:black">Background:</span></b><span style="color:black"> 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&#39; noise hearing function as a sub-acute exposure. </span></span><br> <span style="line-height:250%"><b><span style="color:black">Materials and Methods: </span></b><span style="color:black">In this experimental study, 40 male rats were divided into 4 groups as 1) control group 2) <a name="_Hlk105287011">exposed to </a>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. </span></span><br> <span style="line-height:250%"><b><span style="color:black">Results:</span></b><span style="color:black"> 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).</span></span><br> <span style="line-height:250%"><b><span style="color:black">Conclusion:</span></b><span style="color:black"> 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.</span></span></span></span><br> &nbsp;</div> Hearing Loss,Lead,Heavy Metals,Noise,Blood,Auditory Brainstem Response, 67 75 http://johe.rums.ac.ir/browse.php?a_code=A-10-449-1&slc_lang=en&sid=1 Batol Masruri batolmasruri@gmail.com 22400319475328460011272 22400319475328460011272 No PhD Student in Occupational Health and Safety, Dept. of Occupational Health, School of Medical Sciences, Tarbiat Modares University, Tehran, Iran. Tarbiat Modares University Iraj Alimohammadi irajrastin1@gmail.com 22400319475328460011273 22400319475328460011273 No Professor, Dept. of Occupational Health, School of Public Health, Iran University of Medical Sciences, Tehran, Iran. Iran University of Medical Sciences Jamileh Abolghasemi abolghasemi1347@yahoo.com 22400319475328460011274 22400319475328460011274 No Associate Prof., Dept. of Biostatistics, School of Public Health, Iran University of Medical Sciences, Tehran, Iran. Iran University of Medical Sciences Parvaneh Yekzamani yekzamani71@yahoo.com 22400319475328460011275 22400319475328460011275 No MSc in Occupational Health and Safety, Dept. of Occupational Health, School of Public Health, Iran University of Medical Sciences, Tehran, Iran. Iran University of Medical Sciences Azadeh Ashtarinezhad azadeh_ashtarinezhad@yahoo.com 22400319475328460011276 22400319475328460011276 Yes Assistant Prof., Dept. of Occupational Health, School of Public Health, Iran University of Medical Sciences, Tehran, Iran. Iran University of Medical Sciences