Audiological findings in workers exposed to styrene alone or in concert with noise

Audiological testing, interviews and exposure measurements were used to collect data on the health effects of styrene exposures in 313 workers from fiberglass and metal-product manufacturing plants and a mail terminal. The audiological test battery included pure-tone audiometry, distortion product otoacoustic emissions (DPOAE), psychoacoustic modulation transfer function, interrupted speech, speech recognition in noise and cortical response audiometry (CRA). Workers exposed to noise and styrene had significantly poorer pure-tone thresholds in the high-frequency range (3 to 8 kHz) than the controls, noise-exposed workers and those listed in a Swedish age-specific database. Even though abnormalities were noted on DPOAE and CRA testing, the interrupted speech and speech recognition in noise tests were the more sensitive tests for styrene effects. Further research is needed on the underlying mechanisms to understand the effects of styrene and on audiological test batteries to detect changes in populations exposed to solvents.