Ototoxic effects of styrene alone or in concert with other agents: A review

Styrene is an organic solvent employed in many manufacturing industries, as well as in other economic sectors. Recently, evidence is beginning to accumulate on the hazardous effects that styrene exposures have on the auditory system. In rats, a well-suited metabolic animal model for these studies, aromatic solvents seem to affect the auditory sensitivity mainly in the cochlear mid-frequency range. Outer hair cells are the primary targets within the organ of Corti, although the spiral ganglions are not spared. Therefore, styrene must be considered as an ototoxic chemical agent that can be potentially neurotoxic. Finally, noise-styrene exposures can have synergistic effects on the auditory system. The findings reported in both human and animal studies indicate that exposures to styrene, or to styrene associated to noise, may dramatically impact occupational hearing conservation practices and legislation. Human and animal studies will be summarized in discussing the effects of styrene alone or in combination with noise and other chemicals. Gaps in scientific knowledge are highlighted to assist future research.