Association between combined occupational exposure to coal dust and noise and high-frequency hearing loss among workers: a cross-sectional study.

BACKGROUND: Occupational environments contain a wide variety of harmful factors, with noise often coexisting with other physical, chemical factors, leading to combined exposure that may increase the risk of hearing impairment among workers. This study aims to investigate the association of occupational noise and coal dust combined exposure on noise-induced hearing loss in workers, providing evidence for the prevention and control of occupational noise-induced hearing loss in occupational populations. METHODS: We conducted a cross-sectional study of 1,187 occupationally exposed workers. These workers who underwent occupational health examinations at a certain occupational health examination institution in Baiyin City in 2023 were selected as study subjects and divided into a noise only group (276 participants) and a combined noise-coal dust exposure group (911 participants). Pure-tone air-conduction audiometry was used to assess hearing loss, and the χ 2 test and multivariate logistic regression analysis were applied to identify risk factors for high-frequency hearing loss (HFHL). RESULTS: The prevalence rates of HFHL were 35.5 and 46.8% in the noise group and the combined noise-coal dust exposure group, respectively, with a statistically significant difference (p < 0.001); the prevalence of speech-frequency hearing loss was relatively low. Hearing abnormalities were primarily concentrated in the high-frequency range, with a marked decline around 4,000 Hz. Multivariate logistic regression analysis indicated that age, gender, and exposure to occupational hazards were independent risk factors for HFHL. After multivariable adjustment, combined exposure to occupational noise and coal dust was associated with higher odds of HFHL compared with noise exposure alone (OR = 1.620, 95% CI: 1.198-2.190, p = 0.002). CONCLUSION: Occupational noise-induced hearing loss is predominantly HFHL, and Workers classified as jointly exposed to occupational noise and coal dust had higher adjusted odds of HFHL than workers classified as exposed to occupational noise alone. Comprehensive protection and occupational health surveillance for workers exposed to combined hazards should be strengthened.