Mixed solvent exposure and hearing impairment: an epidemiological study of 3284 men. The Copenhagen male study

Animal experiments and human studies have indicated an effecton auditory functions from exposure to organic solvents. Inthis study the relationship between self-assessed hearing problemsand occupational exposure to solvents was investigated in across-sectional design with 3284 participating men aged 53–74years. Exposure to solvents for five years or more resultedin an adjusted relative risk (RR) for hearing impairment of1.4 (95 per cent Cl: 1.1–1.9) in men without occupationalexposure to noise. Factors adjusted for were age, noise traumas,chronic middle ear infection and family history of hearing impairment.The prevalence of hearing impairment in men not exposed to organicsolvents was 24 per cent and the attributable risk from solventexposure was 9.6 per cent. Exposure for less than five yearshad no effect on hearing capacity. Occupational exposure tonoise for five years or more had an effect twice that of solvents,RR: 1.9 (95 per cent Cl: 1.7–2.1). In men exposed to bothsolvents and noise the effect of the latter dominated and noadditional effect from solvents was found. A subsample of 51men was examined with pure tone audiometry and 20 of 21 menwho reported abnormal hearing also fulfilled an audiometriccriterion for hearing impairment. In conclusion a damaging effecton hearing ability from long-term solvent exposure was foundin the present study. The relative effect was moderate but witha high background frequency of hearing problems in the unexposedsample the absolute effect, ie attributable risk, was considerableand of both clinical and preventive importance.