Avaliação do sistema auditivo em agricultores expostos à agrotóxicos

Hearing Difficulties Among Farmworkers in the México-US Southwest Border Region

Migrant and seasonal farmworkers are a vulnerable population with a potentially high risk for hearing loss due to farm-related noise exposures. Occupational noise-induced hearing loss (NIHL) is permanent, and it is associated with an increased risk for injuries on the job, as well as communication difficulties, isolation, and depression. The México/US border region is one of the most productive agricultural regions in the country, however, no known studies have explored hearing loss among farmworkers in this area. This pilot study was a first step toward measuring and addressing hearing loss and noise exposure among this region's farmworkers. We conducted a cross-sectional survey to estimate the prevalence of subjective hearing difficulties among Yuma County, Arizona farmworkers. Survey interviews took place during a late-night farmworker health fair from 2 am to 6 am to accommodate local farms' labor schedules. Multivariable regression adjusted for demographic and work covariates estimated subjective hearing loss prevalence ratios. Among 132 farmworker participants, 36% reported they have or might have hearing loss, and 62% reported no hearing loss. Subjective hearing loss prevalence was lower in farmworkers who report not working in noise compared to prevalence in farmworkers who work in noise [prevalence ratio, 0.44 (95% CI 0.23-0.82)]. This report contributes to understanding the perception of hearing-related health and occupational exposures among farmworkers in the México-US Southwest border region. The information from this line of research will inform appropriate safety measures known to lower the risk of experiencing occupational NIHL.

Audiological findings of family farmers exposed to pesticides

PURPOSE

To analyze the possible differences among the hearing of farmers and their families when compared to the population not exposed to pesticides.

METHODS

Cross-sectional study with 70 smallholder family farmers (research group), with the mean age of 39.7 years, of both sexes and a mean of 23.7 years of exposure to pesticides. We included a control group with 71 participants of both sexes with the mean age of 39.5 years, not exposed to either noise or chemical substances, to compare the results. In stage 1, both groups were submitted to conventional and high-frequency audiometry, and acoustic immittance. In stage 2, only people with normal hearing were submitted to the evoked otoacoustic emissions and suppression effect on transient otoacoustic emissions.

RESULTS

Significant differences were observed between the groups in the conventional pure-tone and in the high-frequency audiometry, as well as in the acoustic reflex. The most affected frequencies in the conventional pure-tone audiometry ranged from 3 to 6 kHz and, in the high-frequency audiometry, from 9000 to 11200 Hz. As for the transient otoacoustic emissions, the worse suppression effect results were found in the research group.

CONCLUSION

There were differences among the hearing of family farmers and the control group. The conventional auditory thresholds are related to the group, age and sex. Farming is associated with impairments in the basal region of the cochlea, absence of acoustic reflex, reduced signal-to-noise ratio of the transient otoacoustic emissions, and dysfunction in the olivocochlear efferents of the auditory system.

Effects of subchronic inhalation exposure to an organophosphorus insecticide compound containing dichlorvos on wistar rats' otoacoustic emissions

Introduction

Considering that previous studies suggest that pesticides may cause hearing disorders in humans, as well as the lack of studies proving the specific mechanisms of injury and the difficulty of separating concomitant etiological factors of the hearing damage, such as noise and vibration, it is important to develop studies using animal models to elucidate the effects of exposure to those substances isolated from other hearing damage etiologies.

Objective

To evaluate if the exposure to a dichlorvos based organophosphorus insecticide may induce ototoxicity.

Methods

36 male Wistar rats were assigned to 3 groups (12 rats/group): control (exposed to water), positive control (treated with cisplatin to induce hearing damage) and experimental (exposed to dichlorvos based organophosphorus insecticide). The amplitude of distortion product otoacoustic emissions in the frequencies of 4, 6, 8, 10 and 12 kHz was evaluated before and after exposure, as well as systemic toxicity signs, body mass gain and plasma cholinesterase. Open field and plus maze tests were performed in 24 rats: experimental (n = 8), control (n = 8) and positive control group (n = 8 introduced new rats to induce anxiolytic activity) to evaluate the locomotor activity and anxiety, respectively.

Results

There was no significant change in body mass gain and plasma cholinesterase in the dichlorvos based organophosphorus insecticide group, however, the animals showed transient piloerection, depression and dyspnea during exposure. The behavior was not affected in any group. The frequencies of 8 and 10 kHz were significantly affected bilaterally in the insecticide group, which also showed a significant difference of the control in 10 kHz on the right and 8 and 10 kHz on the left ear.

Conclusion

Subchronic inhalation exposure to dichlorvos based organophosphorus insecticide induced ototoxicity in the cochlear function of rats without relevant systemic toxicity.

[High frequency hearing among rural workers exposed to pesticides]

Pesticides may cause a number of health problems and are considered oto-agressive agents. The objective of this study was to investigate the high frequency hearing characteristics of workers both with and without exposure to pesticides, that presented normal conventional audiometry. It involved a cross-sectional study with 87 workers, of both genders, between 19 and 59 years, with formal or informal jobs and some of whom worked with family agriculture, either using pesticides or not, who had taken High-Frequency Audiometry tests. The use of glyphosate was reported by 73% of workers and several pesticide mixtures occurred in 78% of them. There were no cases of proper use of personal protective equipment recommended for the activity. The workers exposed to pesticides had worse results in High-Frequency Audiometry tests in comparison with those who had no contact with pesticides (p < 0.0001). High-Frequency Audiometry has proved to be a useful and effective tool in the early detection of hearing loss caused by pesticides.

Hearing Loss in Agricultural Workers Exposed to Pesticides and Noise

Agricultural workers who have concurrent exposure to pesticides and noise are at increased risk of hearing loss. We recruited 163 Thai conventional and 172 organic farmers to answer our questionnaires about personal demographics, agricultural activities, and pesticide and agricultural machinery use. This information was used to calculate the years of conventional (pesticide use) farming and the years of agricultural noise exposure, and to estimate semiquantitative metrics for pesticide exposure (cumulative intensity score-years) and cumulative noise exposure (dB(A)-years) for each conventional farmer. All participants underwent pure tone audiometric testing. The mean hearing threshold in the low-frequency band (0.5-2 kHz) and high-frequency band (3-6 kHz) were used for analysis. Years involved in conventional farming and years using agricultural machinery were associated with an increase in the average hearing threshold for the high-frequency band after controlling for age, ever exposed to industrial noise and cigarette smoking. The highest category of cumulative insecticide exposure (score-years), cumulative organophosphates exposure (score-years) and cumulative noise exposure (dB(A)-years) were also associated with an increased high-frequency band hearing threshold among conventional farmers. Results from the full cohort and the subcohort of conventional farmers support each other and the hypothesis that pesticide and noise have an additive effect on hearing, since no model interactions were significant.

Ototoxicity of cypermethrin in Wistar rats

Introduction

This study presents the effect of cypermethrin on the cochlear function in Wistar rats post-subchronic inhalation exposure. Worldwide several pesticides are described as causing health disorders. Cypermethrin is currently one of the most commonly used, however, little is known about its harmful effects, especially related to hearing. Human studies have associated pesticides with hearing disorders, but they present limited conclusions due to the multiple factors to which the population is exposed, such as noise.

Objective

Mimic human exposure to cypermethrin and to verify the effects on cochlear function.

Methods

It is a subchronic inhalation animal study (6 weeks, 4 hours/day), using 36 male Wistar aged 60 day. Rats were randomly assigned into three groups: Control (12 rats exposed to inhalation of water); Positive Control for auditory lesion (12 rats administrated with 24 mg/kg intraperitoneal cisplatin); Experimental (12 rats exposed to inhalation of cypermethrin – 0.25 mg/L). Animals were evaluated by distortion product otoacoustic emissions pre- and post-exposure.

Results

The frequencies of 8, 10 and 12 kHz in both ears (right p = 0.003; 0.004; 0.008 and left 0.003; 0.016; 0.005 respectively) and at frequencies 4 and 6 in the right ear (p = 0.007 and 0.015, respectively) in the animals exposed to cypermethrin resulted in reduction.

Conclusion

Subchronic inhalation exposure to cypermethrin provided ototoxicity in rats.

Autopercepção de dificuldade auditiva, hábitos e fatores de risco para perda auditiva em agricultores

RESUMO Objetivo: investigar e associar a autopercepção de dificuldade auditiva, os hábitos e os fatores de risco para a perda auditiva em agricultores. Métodos: trata-se de um estudo transversal, de caráter descritivo e exploratório. Participaram do estudo 57 agricultores, de ambos os gêneros, faixa etária entre 19 e 69 anos, e tempo de atuação agrícola entre um e 45 anos. Os sujeitos responderam um questionário com questões relacionadas a dados de identificação, ocupacionais, saúde geral, saúde auditiva e assistência médica. Os dados foram analisados utilizando-se os testes não-paramétricos Man-Whitney, Igualdade de Duas Proporções e Qui-quadrado (p≤0,05). Resultados: observou-se que a maioria dos agricultores relatou não possuir queixa auditiva; em relação aos fatores de risco para a perda auditiva a maioria relatou ter contato com agrotóxicos e não receber orientações sobre os riscos audiólogicos da prática agrícola; houve maior relato de exposição ao ruído e contato com agrotóxico em sujeitos do sexo masculino; grande parte dos sujeitos faziam utilização de equipamento de proteção individual quando trabalhavam com instrumento ruidoso e tinham contato com agrotóxico; não houve diferença estatística entre os fatores de ouvir e os fatores de risco. Conclusão: conclui-se que a população estudada não possuía percepção de dificuldade auditiva, apesar de ter contato direto com agrotóxicos e nunca ter recebido orientações sobre os riscos audiológicos da prática agrícola. A maioria dos sujeitos que fazia uso de instrumento de trabalho ruidoso e que tinha contato com agrotóxicos, utilizava equipamento de proteção individual.