Tehran University of Medical Sciences International Journal of Occupational Hygiene 2008-5109 17 2 2025 12 09 108 115 Tahereh Vahdati Center for Research on Occupational Diseases, Tehran University of Medical Sciences, Tehran, Iran Ramin Mehrdad Center for Research on Occupational Diseases, Tehran University of Medical Sciences, Tehran, Iran Mahsa Naserpour Department of Environmental Engineering, Mehr Alborz University (MAU), Tehran, Iran Omid Aminaian Department of Occupational Medicine, School of Medicine, Occupational Sleep Research Center, Tehran University of Medical Sciences, Tehran, Iran Gholamreza Pouryaghoub Department of Occupational Medicine, School of Medicine, Center for Research on Occupational Diseases, Tehran University of Medical Sciences, Tehran, Iran Maryam Saraei Department of Occupational Medicine, School of Medicine, Baharlou Hospital, Tehran University of Medical Sciences, Tehran Iran Sahar Eftekhari Department of Occupational Medicine, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran Hamidreza Pouragha Center for Research on Occupational Diseases, Tehran University of Medical Sciences, Tehran, Iran | Department of Environmental Engineering, Mehr Alborz University (MAU), Tehran, Iran 2025 05 05 2025 06 09 Background: Noise-induced hearing loss (NIHL) is among the most prevalent occupational disorders in industrial settings, particularly in the automotive manufacturing sector. Despite extensive noise exposure, variability in hearing outcomes suggests the presence of multiple occupational and non-occupational contributing factors. Purpose of the study: This study aimed to evaluate the hearing status of employees in a major automobile manufacturing company and to compare the prevalence and severity of hearing loss between noise-exposed production (blue-collar) workers and non-exposed administrative (white-collar) staff. Methods: A cross-sectional study of 2,312 male workers (2,136 blue-collar, 176 white-collar) assessed hearing thresholds via pure-tone audiometry. Hearing loss was defined as >25 dB HL. Demographic and occupational data were analyzed using descriptive and inferential statistics. Results: The mean age was 42.9 years. Hearing loss >25 dB HL was under 10% across all subgroups. No major differences in overall thresholds were found, though white-collar workers showed slightly greater hearing loss at select low and high frequencies, despite no occupational noise exposure. Differences were statistically, but not clinically, significant. Conclusion: These findings suggest that occupational noise exposure alone does not fully explain hearing loss among industrial workers. Better hearing outcomes in noise-exposed blue-collar workers may reflect the effectiveness of structured hearing conservation programs and pre-employment screening. In contrast, white-collar staff may experience hearing decline from non-occupational sources. The results underscore the importance of the Healthy Worker Effect and highlight the need for future research to account for worker selection, health surveillance practices, and prior noise exposure beyond the workplace. https://ijoh.tums.ac.ir/index.php/ijoh/article/view/692 https://ijoh.tums.ac.ir/index.php/ijoh/article/download/692/866