[Hearing function and solvent exposure: study of a worker population exposed to styrene]. / Udito ed esposizioni a solventi: studio di una popolazione di lavoratori esposti a stirene.

The aim of the study was to investigate the ototoxic effects of occupational styrene exposure, in absence of other risk factors. Pure-tone audiometric thresholds of 32 workers exposed to styrene, but not to noise, in fibreglass reinforced plastic boat manufacturing process were detected and compared to audiometric thresholds of a control unexposed group composed by 60 subjects. Exposure to styrene was measured by urinary mandelic + phenylglyoxylic acid (mean value 149 mg/g crea, SD 80 mg/g crea). For all the frequencies investigated (0,5-1-2-3-4-6-8 KHz) the exposed group showed slight higher mean (median) audiometric thresholds (p < 0.05) compared to controls matched by age and sex, except for 8 KHz in the right ear. The present experience seems to confirm the hypothesis that styrene exposure alone can determine a weak sensorineural high-frequency hearing loss. Such slight impairment, even if statistically significant, does not remarkably limit social hearing and do not involve legal medical aspects. Sample expansion and objective diagnostic tests (auditory brainstem evoked potentials, acoustic otoemissions) are needed.