Ototoxic substances exacerbate noise-induced hearing loss

Since more than twenty years, research has shown that certain substances, called ototoxics, can provoke a chemical-induced hearing loss, or exacerbate the noise-induced hearing loss. And it is quite common that an individual is exposed to several chemical agents (drugs, chemicals), or to a co-exposure such as a noise and chemical exposure. Aminoglycosides and anti-neoplastic drugs are well-known ototoxic substances. Aromatic solvents, heavy metals, or asphyxiants can be also cochleotoxic. Noise conservation programs consider that only noise exposures are traumatic. Moreover, the legislation is based on statements obtained with subjects without fragility of the inner ear. But an ear contaminated by an ototoxic substance is more vulnerable to a noise exposure that an ear exposed to noise only. What about the pertinence of the threshold limit values determined for noise (LEX,d), or for ototoxic agents (TLV), when people are exposed to two or several nuisances? On the other hand, the diagnostic of deafness is mainly based on pure-tone auditory thresholds, technique dedicated to the perception of auditory inputs. But this technique might be sometime inadequate because of the plasticity of the central nervous system which is capable of compensating peripheral traumatisms. Indeed, plasticity process can mask peripheral trauma, when they are not too severe. In the present article, a new approach is presented to objectively measure the peripheral auditory fatigue and to assess early cochlear suffering. As a result, the prevention against the risks of auditory deficits would be improved.