[Ototoxic effects of carbon monoxide exposure: a review].

BACKGROUND Ototoxic effects of carbon monoxide exposure: a review. AIM To analyze the literature on hearing and Carbon Monoxide (CO). METHODS To describe the physical properties, the absorption, distribution and metabolism of CO, as well as its origin, production, sources and the international standards for occupational exposure. Several studies about the effects of CO exposure to the auditory system of humans and experimental animals were discussed. The main economic sectors where the combined exposure to noise and CO takes place were identified. A description of the basic CO toxic mechanisms that are able to raise occupational noise-induced hearing loss was given. CONCLUSION The review of the literature indicated the following: 1. Examples of CO exposure sources include air pollution, smoking and second-hand smoking, and occupational exposures. 2. CO's main toxic mechanism can lead to hypoxia due to the conversion of oxyhemoglobin to carboxyhemoglobin. 3. Rats have been the most used experimental animals in CO auditory effects studies, this group of studies has demonstrated the combined effects of acute exposure to CO and noise. 4. Studies about the negative effects of CO exposure over the human auditory system were mainly carried out after acute exposures to CO. These studies did not control or report exposure to noise as a contributor to the observed hearing deficits. Currently the available evidence indicates the need for further research on the effects of CO exposure to the auditory system, alone or in combination with noise.