Hearing loss among workers exposed to moderate concentrations of solvents

Objectives It is known that some industrial organic solvents are ototoxic. This study was aimed at evaluating the hearing effects of a mixture of orga nic solvents alone or in combination with noise on employees in paint and l acquer enterprises. The concentration of solvents was below the occupationa l exposure limits (OEL) for most of the subjects. Methods Altogether 517 subjects were divided into the following three group s: persons with no risk due to noise or organic solvent exposure at the wor kplace, workers exposed to organic solvents only, and workers exposed to bo th organic solvents and noise. Results The relative risk (RR) of hearing loss in the solvent-only exposure group was significantly increased (RR 4.4 and RR 2.8 for noise exposure of < 80 dB-A and < 85 dB-A, respectively) in a wide range of frequencies (2-8 kHz). No additional risk in the solvent + noise exposure group was found ( RR 2.8). Hearing thresholds were significantly poorer in a wide range of fr equencies (1-8 kHz) for both groups exposed to solvents, when compared with the reference group. The mean hearing thresholds at frequencies of 2-4 kHz were poorer for workers exposed to solvents + noise than for the solvent-o nly group; this finding suggests an additional effect for noise, However, t here was no correlation between hearing loss and the extent of solvent expo sure. Conclusions The results indicate that occupational organic solvent exposure at moderate concentrations increases the risk of hearing loss, and the oto toxic effects should be considered when the health effects of exposed worke rs are monitored.