The European Directive 2003/10/CE, regarding the workers’ protection against the risks caused by the exposure to high levels of noise, recommends to point out the simultaneous exposure to noise and other ototoxic agents (organic solvents, vibration).
INAIL Research is the leader in a national research project, funded by the Italian Ministry of Health entitled: “Objective diagnosis of the hearing functionality and of the hearing loss susceptibility in workers exposed to noise and/or ototoxic agents, by development of advanced techniques for the acquisition and analysis of otoacoustic emissions. Evaluation of the dose-response relation in populations exposed to synergistic ototoxic risk factors, by development of advanced chemical analytical techniques and experimental animal model studies”.
The project is close to its conclusion and some results can be summarized. Otoacoustic emissions (OAEs) are simple, objective, quantitative and non-invasive biomarkers of healthy cochlear function. They are sound detectable in the ear canal as a by-product of the activity of the cochlear amplifier. The ototoxic effect of the exposure to styrene was evaluated in a sample of workers, in the presence of simultaneous exposure to noise close to the European first action level of 80 dB(A), using otoacoustic emissions as biomarkers of mild cochlear damage. Otoacoustic emissions were able to discriminate the exposed workers from the controls, providing also a rough estimate of the slope of the dose-response relation between otoacoustic levels and styrene exposure. The study of the polymorphisms of the styrene metabolism should be able to individuate the indices of individual susceptibility to the styrene exposure.