Introduction The effect of combined exposures to noise and solvents on hearing has been studied for decades, but the characterization of the risk is incomplete.

Objective To assess the temporary and permanent auditory effects associated with occupational co-exposures to low levels of solvents and noise.

Method Cross-sectional study with 25 printing industry workers (mean age 36.2 years) simultaneously exposed to low levels of solvents and noise ( < 8 0 dBA TWA). The control group composed of 29 industry workers (mean age 36.7 years) without exposure to noise and/or solvents. Participants answered a questionnaire and underwent pure-tone audiometry (PTA), acoustic immittance tests, auditory brainstem response (ABR), dichotic digit test (DD). We examined auditory fatigue through the EchoScan test.

Results Exposed workers had worse thresholds bilaterally at 4 kHz (p=0.0253 in right ear - RE; p=0.0436 in left ear - LE). Ipsilateral acoustic reflex levels were different between groups at the frequencies of 500 Hz (p=0.02 in RE; p=0.04 in LE) and 1 kHz (p=0.04 in LE). The only differences detected by the ABR was for the interpeak interval III-V (p=0.03 in RE; p=0.02 in LE). DD means (exposed= 89.5±13.33; control= 96.40±4.46), were only different in the LE (p=0.05). Echoscan detected a difference (p=0.0317) between the means of the exposed (4.58±6.8) and control (0±4.62) groups, indicating possible hearing fatigue in the exposed group.

Conclusion Each of the hearing tests indicated differences between the groups, suggesting that occupational co-exposure to low noise and low concentrations of solvents can be harmful to hearing functions. The temporary effect of the exposure was detected by the EchoScan and the acoustic reflex of the stapedius muscle. The permanent effects were identified mainly at the level of the high brainstem and in the auditory ability of binaural integration. The EchoScan, can facilitate the early identification of auditory effects, while these are still temporary.