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Effects of mixed blood metals on hearing loss among steel workers: a case-control study
Jian Zhang1, Junwei He1, Yifan Zhang1
1Department of Epidemiology and Health Statistics, Xiangya School of Public Health, Central South University, Changsha, Hunan, China.
Objectives:
To investigate the associations of single and multiple blood metal exposures with hearing loss, and evaluate the interactions between metals and noise exposure, thereby providing scientific evidence for the prevention and control of hearing loss in occupational populations.
Methods:
This study investigates the associations between 17 blood metals and hearing loss among steel workers. A matched case-control study was conducted, including 300 cases with hearing loss and 300 age- and sex-matched controls, selected from 4,081 eligible workers. Metal concentrations were measured by inductively coupled plasma mass spectrometry (ICP-MS). Associations were estimated by multivariable logistic regression, LASSO regression, weighted quantile sum (WQS) regression, and Bayesian kernel machine regression (BKMR). The most important metals were identified, and their additive interactions with noise exposure were further assessed.
Results:
Cases and controls were comparable in age, sex, and work tenure (all P > 0.05). Blood levels of Mn, Cu, As, Se, and Sr were significantly higher in cases than in controls (all P < 0.05). Logistic regression showed that Mn (OR = 4.68, 95%CI: 2.88-7.59), Cu (OR = 3.30, 1.55-7.04), As (OR = 1.14, 1.05-1.22), Se (OR = 4.25, 2.16-8.37), and Sr (OR = 8.22, 4.56-14.80) were associated with increased hearing loss risk. WQS analysis indicated a positive association between metal mixture and hearing loss (OR = 6.52, 95%CI: 3.61-11.78), with Se (0.261) and Sr (0.256) having the highest weights. BKMR further identified Mn and Sr as the most important predictors. Significant additive interactions were found respectively for Mn and Sr with noise exposure: RERI = 11.36 (5.72-39.38) and 17.53 (8.07-66.64).
Conclusion:
Noise and multiple metals (particularly Mn and Sr) were significantly associated with hearing loss in steel workers, with potential additive interactions observed between these exposures. Therefore, comprehensive occupational health strategies addressing both noise and metal exposures may be important for hearing loss prevention.
