Mercury Exposure in a Riverside Amazon Population, Brazil. A Study of the Ototoxicity of Methylmercury
Background: The mercury poisoning causes hearing loss in humans and animals. Acute exposure and long-term produce irreversible peripheral and central auditory system damage and that mercury in its various forms of presentation in the environment is ototoxic.
Aims: We investigated the otoacoustic emissions responses in a riverside population exposed to environmental mercury by analyzing the inhibitory effect of the medial olivocochlear system (MOCS) on transient otoacoustic emissions (TEOAE).
Methods: The purpose of the research was to evaluate the entire community independently of variables of sex and age. All of the participants were born and lived in a riverside community. After otolaryngologic evaluation, participants were submitted to tympanometry, contralateral acoustic reflexes, pure-tone audiometry, and recording of TEOAEs with nonlinear click stimulation. Hair samples were collected to measure mercury levels.
Results: There was no significant correlation between the inhibitory effect of the MOCS, age, and the level of mercury in the hair.
Conclusions: The pathophysiologic effects of chronic exposure may be subtle and nonspecific, and have a long period of latency; therefore, it will be important to monitor the effects of mercury exposure in the central auditory system of the Puruzinho population over time. Longitudinal studies should be performed to determine whether the inhibitory effect of the MOCS on otoacoustic emissions can be an evaluation method and diagnostic tool in populations exposed to mercury.