Saúde auditiva de trabalhadores expostos a ruído e inseticidas Hearing health of workers exposed to noise and insecticides

OBJETIVO: Avaliar as alterações auditivas periféricas em um grupo de trabalhadores exposto a inseticidas, organofosforados e piretróides, utilizados em campanhas de controle de vetores. MÉTODOS: Estudo de prevalência de uma população de 98 indivíduos que pulverizavam venenos nas campanhas de prevenção do dengue, da febre amarela e da doença de Chagas. A amostra foi de tipo finalística, considerando o universo dos trabalhadores de um distrito sanitário, em Pernambuco, no ano de 2000. Utilizou-se questionário contendo questões de identificação de riscos ocupacional e não ocupacional, medidas de segurança utilizadas, antecedentes de problemas auditivos e sintomas referidos. Foi investigada a historia pregressa de exposição ao ruído, por ser um fator de confusão para a perda auditiva. Todos os indivíduos foram avaliados pelo teste de audiometria tonal. RESULTADOS: Dos expostos apenas aos inseticidas, 63,8% apresentaram perda auditiva. Para o grupo com exposição concomitantemente aos inseticidas e ao ruído, a perda auditiva foi de 66,7%. O tempo mediano para o desenvolvimento de alterações auditivas nas freqüências médias altas, para as exposições combinadas de inseticidas e ruído, foi de 3,4 anos e para as exposições apenas aos inseticidas foi de 7,3 anos. A perda auditiva para as exposições concomitantes aos dois fatores foi de maior intensidade nessas freqüências, do que o observado na exposição apenas aos inseticidas. CONCLUSÕES: Há evidência de que a exposição aos inseticidas induz dano auditivo periférico e que o ruído é um fator que interage com os inseticidas, potencializando seus efeitos ototóxicos. Faz-se necessário avaliar essa possível associação através de estudos epidemiológicos de caráter analítico.<br>OBJECTIVE: To examine the peripheral auditory disorders in a group of workers exposed to organophosphate and pyrethroid insecticides, used in vector control campaigns. METHODS: The prevalence study examined a population of 98 individuals who sprayed insecticides in campaigns for the prevention of Dengue, Chagas disease and Yellow fever. The sampling approach was finalistic, and included the workers in a health district of Pernambuco, during the year 2000. A questionnaire was used to collect data on occupational and non-occupational risks, safety measures utilized, family history of auditory problems and health symptoms. Previous noise exposure history was also investigated, since noise can be a confounding factor for hearing loss. Hearing sensitivity and middle ear function were assessed by pure tone audiometry. RESULTS: Among those exposed to insecticides, 63.8% demonstrated a hearing loss. For the group of workers exposed to both noise and insecticides, hearing loss was observed in 66.7% of the cases. The median exposure time necessary to detect high-frequency losses was 3.4 years for workers exposed to both agents and 7.3 years for workers exposed to insecticides only. Hearing thresholds were poorest among workers exposed to both agents. Auditory damage for those with combined exposures to the two factors was more severe than the hearing losses observed among those exposed only to insecticides. CONCLUSIONS: There is evidence that exposure to insecticides was associated with peripheral sensorioneural hearing loss and that noise exposure can potentiate the ototoxic effects of insecticides. It is necessary to evaluate this possible association through epidemiological studies

Self-reported hearing performance in workers exposed to solvents

OBJECTIVE: To compare hearing performance relating to the peripheral and central auditory system between solvent-exposed and non-exposed workers. METHODS: Forty-eight workers exposed to a mixture of solvents and 48 non-exposed control subjects of matched age, gender and educational level were selected to participate in the study. The evaluation procedures included: pure-tone audiometry (500 - 8,000 Hz), to investigate the peripheral auditory system; the Random Gap Detection test, to assess the central auditory system; and the Amsterdam Inventory for Auditory Disability and Handicap, to investigate subjects' self-reported hearing performance in daily-life activities. A Student t test and analyses of covariance (ANCOVA) were computed to determine possible significant differences between solvent-exposed and non-exposed subjects for the hearing level, Random Gap Detection test and Amsterdam Inventory for Auditory Disability and Handicap. Pearson correlations among the three measures were also calculated. RESULTS: Solvent-exposed subjects exhibited significantly poorer hearing thresholds for the right ear than non-exposed subjects. Also, solvent-exposed subjects exhibited poorer results for the Random Gap Detection test and self-reported poorer listening performance than non-exposed subjects. Results of the Amsterdam Inventory for Auditory Disability and Handicap were significantly correlated with the binaural average of subject pure-tone thresholds and Random Gap Detection test performance. CONCLUSIONS: Solvent exposure is associated with poorer hearing performance in daily life activities that relate to the function of the peripheral and central auditory system

Cells in Auditory Cortex that Project to the Cochlear Nucleus in Guinea Pigs

Fluorescent retrograde tracers were used to identify the cells in auditory cortex that project directly to the cochlear nucleus (CN). Following injection of a tracer into the CN, cells were labeled bilaterally in primary auditory cortex and the dorsocaudal auditory field as well as several surrounding fields. On both sides, the cells were limited to layer V. The size of labeled cell bodies varied considerably, suggesting that different cell types may project to the CN. Cells ranging from small to medium in size were present bilaterally, whereas the largest cells were labeled only ipsilaterally. In optimal cases, the extent of dendritic labeling was sufficient to identify the morphologic class. Many cells had an apical dendrite that could be traced to a terminal tuft in layer I. Such “tufted” pyramidal cells were identified both ipsilateral and contralateral to the injected CN. The results suggest that the direct pathway from auditory cortex to the cochlear nucleus is substantial and is likely to play a role in modulating the way the cochlear nucleus processes acoustic stimuli