The effects of combined exposure of solvents and noise on auditory function – a systematic review and meta-analysis

Background: Chemical substances can negatively affect the auditory system. Chemical substances alone or combined with high-level noise have recently become a major concern as a cause of occupational hearing loss. Objective: To assess the combined effect of solvents and noise versus solvents only, or noise only, on the auditory function of workers. Method: Published articles which included noise and/or solvent exposure or combined effects of solvents and noise, studies conducted on human beings only and the use of audiological tests on participants. Results: Thirteen papers were eligible for inclusion. The participants’ ages ranged from 18 to 68 years. Results revealed that 24.5% presented with hearing loss as a result of noise exposure only; 18% presented with hearing loss owing to solvent exposure only; and a total of 43.3% presented with hearing loss owing to combined noise and solvent exposure. Furthermore, the prevalence of hearing loss in the noise and solvent group was significantly (p < 0.001) higher than the other groups in 10 out of the 13 studies analysed, with a pooled odds ratio (OR) of 2.754. Of the 178 participants (total of all participants exposed to solvents), a total of 32 participants presented with auditory pathology as a result of exposure to solvents only. There was a significantly higher pooled odds of hearing loss in noise and solvent-exposed group compared to solvent-only group (pooled OR = 2.15, 95% CI: 1.24–3.72, p = 0.006). Conclusion: The findings revealed significantly higher odds of acquiring hearing loss when workers were exposed to a combination of solvents and noise as opposed to solvents only, motivating for its inclusion into hearing conservation programmes.