Otoneurological symptoms in Brazilian fishermen exposed over a long period to carbon monoxide and noise

Abstract

Fishing, one of the oldest productive activities, is an important sector of the Brazilian economy as well as the world economy. To evaluate the vestibular behavior in population of fishermen. It was realized as a retrospective and cross-sectional study. Thirty fishermen [mean age 49.5 (±8.5) years] whose age ranged from 33 years to 67 years were submitted to anamnesis, otorhinolaryngological evaluation, and vestibular examination through the electronystagmography (ENG). The most evident otoneurological symptoms were: Tinnitus (66.7%), dizziness (63.3%), and hearing loss (53.3%). The most evident clinical symptoms were: Fatigue (36.7%), anxiety (23.3%), and depression (16.7%). There were alterations in the vestibular examination of 13 (43.3%) fishermen in the caloric test. There was a prevalence of alteration in the peripheral vestibular system and there was a major frequency of the peripheral vestibular irritative syndrome (30.0%). Conclusion: The otoneurological complaints were frequent in the population studied that verifies the importance of allowing labyrinth examinations and the need for adopting preventive measures related to noise exposure to carbon monoxide (CO), since they can cause and/enhance various manifestations of labyrinthine vestibular impairment that can affect the quality of life of these workers.

Introduction

Fishing is one of the oldest productive activities and is an important sector of the Brazilian economy as well as the world economy.[1] The fishing industry is an important source of employment and exists in both traditional and industrial settings.

The industrial setting that is the focus of this study occurs in vessels over 24 m long where the fisherman remains at sea for weeks at a stretch. In most cases, he has constant exposure to noise from the boat's engine as well as exposure to carbon monoxide (CO) and tobacco products.

Fishermen remain in boats for many hours, being exposed to high noise levels, localized arm and whole body vibrations, and prolonged CO exposure that can cause health problems both in general and in hearing.[2,3] Studies[3,4] report that the fisherman is exposed to auditory and extraauditory effects from noise over long periods, in addition to inherent problems in the development of industrial fishing.

Among the illnesses that occur in this population, noise-induced hearing loss (NIHL) should be highlighted. In a study in Brazil with 52 industrial fishermen, 61.5% were found to be with audiograms below normal, with characteristics of NIHL and tinnitus reported by 46.1% of the fishermen evaluated.[4]

NIHL is caused by an accumulation of the exposures to noise, usually daily that are repeated continuously for a certain period.[5]

For Nudelmann et al.[6] and Gonçalves,[7] NIHL is preventable and can have negative consequences of different natures, leading to hearing impairment, auditory dysfunctions such as tinnitus and important vestibular changes, both from direct causes (professional disorders) or through multiple etiologies (occupational disorders). In Brazil, despite the evolution of knowledge and legislation about NIHL, there are still cases of injured workers.[8]

Exposure to CO can lead to both early and later neurological side effects that may occur as diffuse, white matter demyelination and ischemic lesions of the globus pallidus.[9,10] When 30 consecutive days of exposure are exceeded, it can lead to chronic poisoning even in low concentrations.[11] CO poisoning can cause toxic effects such as insomnia, headaches, fatigue, decreased physical capacity, dizziness, vertigo, ataxia, mental impairment, nausea, vomiting, visual disturbances, hearing disorders, respiratory diseases, and other less frequent effects.[10,11,12,13]

Several studies emphasize the effects of the combined exposure to CO and noise. Authors[14,15] reported that simultaneous exposure to these two factors can lead to a potentiation of the effects of noise affecting not only the ears but also the mechanisms responsible for the body's balance.

Due to their profession, several fishermen refer to strain in the arms and wrists and pain in areas involving the neck and shoulders. The tests that make up the vestibular examination permit the assessment of the relationship between balance and the function of the posterior labyrinth, vestibular branches of the eighth cranial nerve, vestibular nuclei of the floor of the fourth ventricle, the vestibular pathways, and especially the vestibuloocular, vestibulocerebellar, vestibulospinal, and vestibulo proprioceptive-cervical interrelationships.

The aim of this study was to evaluate the vestibular behavior in a population of fishermen.

Methods

We evaluated 30 fishermen whose age ranged from 33 years to 67 years [mean age 49.5 (±8.5) years]; we were directed by the Jorge Duprat Figueiredo Foundation for Safety and Occupational Medicine (FUNDACENTRO) of the Ministry of Labor and Employment for the Otoneurology sector of an educational institution.

It is a cross-sectional study and the fishermen were evaluated irrespective of the time they had spent at sea.

Fishermen without otoscopic alterations were included in the survey and fishermen with musculoskeletal changes that prevented the examination were excluded.

The study was approved by the Institutional Ethics Committee under the protocol number 094/2006 and following authorization through the signing of a consent form, the fishermen were subjected to the following procedures.

Anamnesis

A questionnaire was given with an emphasis on the otoneurological signs and symptoms.

Ear, nose, and throat (ENT) evaluation

It was performed in order to rule out any alteration that could affect the test.

Vestibular assessment

The fishermen were subjected to the following tests that make up the vestibular examination: Initially, vertigo and position/positioning nystagmus, spontaneous and semi-spontaneous, were researched.

Then for electronystagmography (ENG), a thermosensitive Berger Eletromedicina model VN316, made in the São Paulo, São Paulo, Brazil unit was used with three recording channels. An active electrode was attached with an electrolytic paste at a lateral angle for each eye and the frontal midline, forming an isosceles triangle that allows the identification of horizontal, vertical, and oblique eye movements and especially, the calculation of the angular velocity the slow-component eye velocity (SCV) of the nystagmus.

We used a Ferrante model COD 14200 made in São Paulo, São Paulo, Brazil, an adjustable height swivel chair, a model EV VEC visual stimulator, and air calorimeter model NGR 05; both the visual stimulator and air calorimeter were manufactured by Neurograff Eletromedicina, São Paulo, São Paulo, Brazil.

We compared the results with the normal standards obtained from epidemiological studies for the Brazilian population.[16,17,18] Table 1 shows the criteria used to analyze each test as well as to distinguish central vestibulopathy from peripheral vestibulopathy.

Table 1.

Normal standards and criteria used to analyze the vestibular tests and distinguish central vestibulopathy from peripheral vestibulopathy

Vestibular tests	Normal vestibular examination	Peripheral vestibular examination	Central vestibular examination
Position nystagmus (Brandt-Daroff maneuver)	Absent	Present (rotatory, horizontal rotatory, and oblique) with latency, paroxysm, weariness, and vertigo	Present (vertical inferior, superior, rotatory, horizontal rotatory, and oblique), without latency, paroxysm, weariness, and vertigo
Calibration of the ocular movements	Regular	Regular	Irregular (alterations in latency, accuracy, and velocity of the saccadic movements)
Spontaneous nystagmus	Present (<7º/s) with closed eyes; absent with open eyes.	Present (>7º/s) with closed eyes; absent with open eyes.	Present with open eyes (vertical inferior, superior, rotatory, horizontal rotatory, oblique, cyclic, dissociated, and retractor)
Gaze nystagmus	Absent	Absent	Present, unidirectional, bidirectional, or mixed; presents a variety of nystagmus types
Oscillatory track	Types I and II	Type III	Type IV (pathognomonic); alterations of morphology and gain
Optokinetic nystagmus	Symmetrical, <20º/s	Asymmetrical, >20º/s, having superposed spontaneous nystagmus with open eyes that justifies this alteration	Asymmetrical, >20º/s, absent and reduced
Rotation test	>33%, after stimulation of the lateral and superior semicircular ducts	>33%, after stimulation of the lateral and superior semicircular ducts	>33%, after stimulation of the lateral and superior semicircular ducts and absence of induced oblique nystagmus
Air caloric test	Absolute value: Between 2º/s and 24º/s Relative values: Labyrinth preponderance <41% Nystagmus directional preponderance <36%	Absolute value: <2º/s (hyporeflexia), >24º/s (hyperreflexia) and areflexia Relative values: Labyrinth preponderance >41% Nystagmus directional preponderance >36% (Jongkees formula)	Absolute value: <2º/s (hyporeflexia), >24º/s (hyperreflexia) and areflexia Relative values: Labyrinth preponderance >41% Nystagmus directional preponderance >36% (Jongkees’ formula). Different nystagmus types may be observed: Dissociated, inverted, perverted, and absence of the fast component of the nystagmus
Inhibiting effect of ocular fixation	Present	Present	Absent

Source: Based on Padovan and Pansini,[16] Mangabeira-Albernaz et al.,[17] and Ganança et al.,[18]

The diagnosis of peripheral vestibulopathy was achieved by comparison with the normal standards and the absence of pathognomonic signs of central vestibular alterations:

• Calibration of eye movements, at this stage of the examination, the clinical aspect evaluated was the regularity of motion, making the study data comparable.

• Study of spontaneous nystagmus (eyes open and closed) and semi-spontaneous (eyes open). In this stage we evaluated the occurrence, direction, and inhibitory effect of ocular fixation (IEOF), and the maximum SCV value of the nystagmus.

• Study of pendular tracking for evaluation of occurrence and type of curve.

• Study of optokinetic nystagmus at a speed of 60^°/s, horizontally counterclockwise and clockwise. We evaluated the occurrence, direction, and maximum SCV counterclockwise and clockwise movements of the nystagmus.

• Study of pre-and postrotatory nystagmus in swivel chair testing, stimulating the lateral, anterior and posterior semicircular canals. For stimulation of the lateral (horizontal) semicircular canals, the head was bent forward 30^°. In the next step, to sensitize the anterior and posterior (vertical) semicircular canals, head positioning was 60^° backward and 45^° to the right, and then backward 60^° and 45^° to the left. The occurrence, direction, and counterclockwise and clockwise rotation frequencies of the nystagmus were observed.

• Study of pre- and postcaloric nystagmus were carried out on the patient positioned such that the head and trunk were inclined 60^° backward for adequate stimulation of the lateral semicircular canals. The irrigation time of each ear with air at 42^°C and 20^°C lasted 80 s for each temperature and the responses were recorded with eyes closed and then with eyes open to observe the IEOF. In this evaluation, the direction, the absolute values ​​of the SCV, and the calculation of the relationship of directional preponderance and labyrinthine preponderance of postcaloric nystagmus were observed.

Sound pressure level assessment on vessels

The evaluation of sound pressure levels followed the criteria and procedures set out in technical standard International Organization for Standardization (ISO) 9612: 1997 — Acoustics — Guidelines for the measurement and assessment of exposure to noise in a working environment and the standard developed by FUNDACENTRO, Normas de Higiene Ocupacional (NHO) 01. As described in Table 2, the evaluation of sound pressure levels was carried out in four different kinds of job with one specific location on board and three types of industrial fishing vessels in 2007. The vessels used were: A seiner, a drift net boat, and a trawler. The evaluations were carried out in the compartments of vessels where CO assessments were made. For comparison with the tolerance limits, a calculation was made of the standard exposure level (SEL) for 8 h of exposure while taking into account that the exposure for fishermen was 24 h. The measurement equipment for sound pressure levels used in the assessment of occupational exposure to noise belonged to FUNDACENTRO. To determine the dose or the average level, we used integrating meters for personal-use (noise dosimeters) that meet the specifications in ANSI S1.25 (1991), and integrating meters for the evaluator (sound pressure level meters) that meet the specifications of ANSI S1.4 (1983) and IEC 651 (1993) and are type 2.

Table 2.

Presentation of the CO concentration and the sound pressure level

Job title	Types of vessels based on fishing type
	Drift Net	Trawler	Seiner
	CO concentration (ppm) and SEL (dBA)
Cook/pilot’s assistant	<10 ppm/ 94 dB(A)
Pilot		10 ppm/97.3 dB(A)	15 ppm (smoker);
94.8 dB(A)
Cook		10 ppm/ 81.2 dB(A)	10 ppm;
82 dB(A)
Deckhand			23 ppm (smoker);
87.7 dB(A)
Deckhand			15 ppm;
91.1 dB(A)
Machinery room		<6 ppm/107 dB(A)

SEL = Standard exposure level, dB = Decibel, TL = Tolerance limit = 39 ppm (NR 15, annex no. 11, decree 3214/78 of MTe)[19]

Chemical agent evaluation for CO in vessels

CO environmental assessments [Table 2] were carried out in 2007 on board when the three fishing vessels were on normal fishing activity by a researcher from FUNDACENTRO. The evaluated vessels belonged to fishing companies located in the municipalities of Itajaí, Santa Catarina, Brazil and Navegantes, Santa Cararina, Brazil and were of different types of fishing categories. Vessel A was a drift net boat and vessel B was a trawler, both with 6-men crew; vessel C was a seiner, with a 14-men crew.

For the environmental assessment, the reagent tubes for direct reading by diffusion, specific to CO, manufactured by Dräger, CO 50/a-D was chosen. The evaluations carried out on fishermen were personal sampling and environmental assessment and an environmental sampling to check for CO emissivity in the engine, the most likely location for emissions, and the risk it posed to the occupants. The exhaust pipe of the engine is usually above the ceiling of the vessel control room and is less likely to reach the crew due to its dissipation by wind. For personal sampling, diffusion tubes were attached to the lapel of the fishermen selected for evaluation, and at the time the evaluation began, the tube was broken on one side allowing CO existing in the environment into the tube by a diffusion process permitting it to react with the indicator layer, coloring it. The tube remained open throughout the sampling period and was positioned in the breathing zone of the fisherman. Sampling was carried out during the working day, from the moment it was attached to the worker's lapel until the time he returned to port upon completion of work. However, this time the sample was limited to a maximum 8-h period specified in the instructions provided by the tube manufacturer and removed at this time by the worker who then made a mark on the tube using a permanent ink pen. Once on land, the concentrations were calculated.

To calculate the concentration versus time of assessment, the following formula was used:

[CO concentration (ppm) = Indicator on detection tube/evaluation period (hours)].

The fishermen selected were pilots, cooks, fishermen who were smokers, and deck hands who had indicated that they often smell gases from the burning fuel, diesel oil. For environmental sampling, the tubes were placed on the machinery near the central location of the pilots at their breathing zone level. The sampling time was also limited to a maximum of 8 h, according to the instructions accompanying the diffusion tubes. During the CO assessments, it was observed that the fishermen smoked often.

Statistical analysis

We applied the Difference of Proportions and Fisher's tests in order to compare the results of the vestibular examination (analyzing normal and abnormal results and correlating them with age and length of service) and the Fisher's and chi-square tests (correlating the results of the vestibular examination with the symptoms of tinnitus, dizziness, and hearing loss). It was set at 0.05 or 5% as the level for rejecting the null hypothesis.

Results

The frequency of diverse otoneurological and clinical signs and symptoms are seen in Table 3.

Table 3.

Distribution of the frequency of otoneurological signs and symptoms and clinical findings in 30 fishermen evaluated

Otoneurological signs and symptoms	N	Frequency (%)
Tinnitus	20	66.7
Dizziness	19	63.3
Hearing loss	16	53.3
Headaches	9	30.0
Tingling in extremities	6	20.0
Cracking neck	4	13.3
Pain radiating to the shoulder and arm	4	13.3
Difficulty or pain when moving neck	3	10.0
Imbalance when walking	2	6.7
Lightheadedness	1	3.3
Tremor	1	3.3
Sweating	1	3.3
Diverse clinical signs and symptoms	N	Frequency (%)
Fatigue	11	36.7
Anxiety	7	23.3
Depression	5	16.7
Insomnia	3	10.0
Agitation during sleep	2	6.7

N = Number of cases

The study of positional nystagmus, eye movement calibration, investigation of spontaneous nystagmus with eyes open and closed, semi-spontaneous nystagmus, pendular tracking, and optokinetic nystagmus showed no changes.

In the caloric test, there were 17 cases (56.7%) of normal responses, seven cases (23.3%) of unilateral labyrinth hyperreflexia, three cases (10.0%) of unilateral labyrinth hyporeflexia, two cases (6.7%) of bilateral labyrinth hyperreflexia, and one case (3.3%) of bilateral labyrinth hyporeflexia, as shown in Table 4.

Table 4.

Results obtained on caloric analyzing absolute and relative values ​​and the entrance examination for 30 fishermen evaluated

Caloric test	N	Frequency (%)
Normoreflexia	17	56.7
Unilateral labyrinth hyperreflexia	7	23.3
Unilateral labyrinth hyporeflexia	3	10.0
Bilateral labyrinth hyperreflexia	2	6.7
Bilateral labyrinth hyporeflexia	1	3.3
Vestibular exam	N	Frequency (%)
NVE	17	56.7
PVID	9	30.0
PVDD	4	13.3

N = Number of cases, NVE = Normal vestibular examination, PVID = Peripheral vestibular irritative dysfunction, PVDD = Peripheral vestibular deficit dysfunction

The use of the Difference of Proportions test demonstrated that there was no difference between the proportions of the normal and abnormal examinations (P = 0.5565).

In 13 (43.3%) cases, there were peripheral vestibular disorders, nine cases (30.0%) of irritative peripheral vestibular dysfunction, and four cases (13.3%) of peripheral vestibular deficit dysfunction. The test was normal in 17 cases (56.7%), as described in Table 4.

The use of the Difference of Proportions test demonstrates that there was no difference between the proportions of the normal and abnormal examinations (P = 0.5565).

The correlation between the results of the vestibular examination and tinnitus, dizziness, and hearing loss can be seen in Table 5.

Table 5.

Correlation between the results of vestibular examination and tinnitus, dizziness, and hearing loss in 30 fishermen evaluated

Exam	Otoneurological symptom		P
	Tinnitus
	No	Yes
NVE	8	9	0.0743
AVE	2	11
	Dizziness
	No	Yes
NVE	10	7	0.0047
AVE	1	12
	Hearing loss
	No	Yes
NVE	10	7	0.1269
AVE	4	9

NVE = Normal vestibular examination, AVE = Abnormal vestibular examination

The use of Fisher's test proves that there was no significant difference between the proportions of fishermen with normal vestibular examination (NVE) and abnormal vestibular examination (AVE) with and without tinnitus (P = 0.0743).

The use of Fisher's test shows a significant difference between the proportions of patients with NVE and AVE with and without dizziness (P = 0.0047).

The use of chi-square test proves that there was no significant difference between the proportions of fishermen with NVE and AVE with and without hearing loss (P = 0.1269).

The correlation between the result of the vestibular examination with the age and length of service of the fishermen was significant in Fisher's test where a significant difference between the proportions of fishermen with NVE and AVE and age (P = 0.0051) and a significant difference between the proportions of fishermen with NVE and AVE and length of service (P = 0.0002) were found.

Discussion

Information that is already known on this topic

In analyzing the medical history, the occurrence of multiple diverse clinical and otoneurological symptoms was verified that were mainly tinnitus, dizziness, and hearing loss. According to the literature, tinnitus is the first warning of exposure to excessive sound stimuli and may indicate an increased susceptibility to injury. This is an important symptom in preventing NIHL and is one of the main predictors of disadvantages generated in workers exposed to noise. Tinnitus is one of the three major otoneurological manifestations, along with sensorineural hearing loss and dizziness.[20,21] It is regarded as a physiological disorder resulting from abnormal neural activity in the auditory pathways.[22] Current conceptions suggest the existence of involvement of the peripheral and central auditory systems, afferent and efferent, and the interaction with other systems.[22] Dias et al.[23] evaluated 284 workers and found a prevalence of 63.0% in NIHL and tinnitus in 48.0% of the cases evaluated. In another study[24] carried out among 20 factory workers exposed to occupational noise for more than 10 years, the authors found that prolonged exposure to noise could cause vestibular symptoms that are initially neglected most of the time for being subtle.

Several structures are involved in balance and changes in vestibular and/or auditory systems can often be the cause of body instability.[25] Okamoto and Santos,[26] in correlating noise with vestibular symptoms, observed that during or after exposure to noise, many patients had vestibular disorders such as vertigo with or without neurovegetative symptoms, an unsteady gait, nystagmus, fainting, and pupil dilation. It is known that the auditory impulse, before reaching the cerebral cortex, passes through several subcortical stations that explain the presence of nonauditory effects induced by noise.[26]

Studies carried out[27] on 258 men from the military service in Israel who were exposed to intense impulse and impact noises showed a vestibular dysfunction (not specifying type) when asymmetric hearing loss occurs. According to the authors, there is an association between the severity of hearing loss and vestibular symptoms.

In the present study, we observed a change in the peripheral vestibular system in 17 patients; this change was found in the caloric test, with predominance of irritative peripheral vestibular dysfunction. In the literature, there was a scarcity of studies involving the vestibular system and the activity of fishing. We emphasize the research of Kumar, Vivarthini, and Bhat[15] who applied vestibular evoked myogenic potentials (VEMP) in individuals with NIHL and observed significant changes in elongation and reduction of n23 latency in p13-n23 intervals, thus demonstrating an involvement of this important otoneurological examination. VEMP was abnormal in 67.0% of the cases with NIHL. The authors concluded that the possibility of vestibular dysfunction, especially in the saccule, was high in these cases. This result is in accordance with the study of Tseng and Young[28] that observed a large number of saccular changes in 30 patients with NIHL. Teixeira, Körbes, Rossi et al.[29] assessed a balance by examining the computerized dynamic posturography (CDP) in 16 workers exposed to occupational noise of a printing company and observed alterations in balance in the assessment of all the stages tested that evaluate somatosensory, visual, vestibular, and balance functions. The authors reported that high levels of sound pressure can alter balance by the activation of the saccule's sensory cells that are sensitive to both labyrinthine and acoustic stimuli.

With respect to CO poisoning, Kowaska[30] studied 50 patients and the results showed bilateral hearing loss in different degrees in 42.0%, retrocochlear impairment in 80.0%, deafness in 6.0%, and vestibular dysfunction in 86.0% of the patients. In another study[31] conducted on workers exposed to CO, 66.0% had hearing loss and 76.5% had vestibular dysfunction. According to the author, these data confirmed the toxic effects of CO.

When comparing the results of the vestibular examination with complaints of dizziness, this difference becomes relevant. According to Cohen,[32] dizziness may hinder the performance of the individual in performing activities requiring rapid movements of the head and also on tasks involving trunk and head flexion. This explains the significance that occurs with the symptom of dizziness since this type of profession sometimes requires jerky movements of the trunk and head.

When we compared the results of the vestibular examination to the age and length of service, we observed the results to be significant. This demonstrates that the individual enters this profession early and works for a long period in most cases, going through several generations that entails combined exposure to CO and NIHL for a long period. These characterize fishermen as a risk population for future vestibulocochlear problems.

Main finding of this study

The most evident otoneurological symptoms were: Tinnitus, dizziness, and hearing loss while several more clinical symptoms reported were: Fatigue, anxiety, and depression.

Alterations in the vestibular examination occurred in 43.3% of the fishermen and were found in the caloric test, with predominant dysfunction of the peripheral vestibular system of the irritative type.

The otoneurologic complaints were frequent and allowed to verify the importance of the labyrinthine examination and the need to adopt preventive measures regarding exposure to noise and CO, as they may cause and/or enhance several manifestations compromising the vestibular system that may affect the quality of life of these workers.

What this study adds

According to the Ministry of Health in Brazil,[33] some chemical exposures may pose a potential health risk causing serious ototoxic effects and damaging a person's hearing and balance functions. Ototoxins can be ingested, inhaled, and absorbed. The chemicals may have endogenous and exogenous origins, the latter including aminoglycosides, diuretics, and chemicals used at work as well as cigarette smoke and alcohol. For the authors,[34] the distinct ototoxic effects of substances in the chemical composition of smoke can synergistically affect the auditory and vestibular systems when combined with noise exposure. Studies of 100 fishermen in Greece[35] reported that health risk factors included alcohol, consumption of fatty foods, smoking, and lack of exercise. Fort, Massardier-Pilonchéry, and Bergeret[36] suggest that stressful working conditions can lead fishermen to higher consumption of and dependence on tobacco and alcohol.

Regarding vibration, the authors[37] investigated the effects of sound on body stability and found that sounds with higher amplitudes and low frequencies can vibrate the vestibular system more than sounds at a high frequency, leading to increased instability. Each structure of the human body responds to different vibratory stimuli; however, the risks to health caused by vibrations are poorly known but can, in general, cause discomfort, pain, nausea, and vomiting.[38]

Exposure to any of these factors (smoking, alcohol, and vibration) can significantly increase the risk of developing major vestibulocochlear alterations, thus demonstrating the importance of clinical monitoring and control tests in the fishing industry. In this way, we can develop educational activities and thereby minimize the effects caused by the interaction of these harmful agents to occupational health.

This study is important for the preservation of workers’ health, its social and economic aspects, and the importance of fishing in Brazil as a job. This is especially true for some coastal municipalities where fishing plays an important role and in places that offer few economic alternatives, where manual laborers are employed who have little or no qualification; in some cases, fishing is the only employment opportunity.

In the literature, we found few Brazilian and international references that addressed the study of vestibulometry in industrial fishermen with which we could have compared our findings. This alone demonstrates the relevance of the subject studied, thus encouraging the continuation of research and new studies on the subject. In this way, we may in the near future plan actions that can minimize the symptoms caused by combined exposure to CO, tobacco, alcoholic beverages, and NIHL for a long period in the performance of this profession.

Limitations of this Study

The fishermen were from colonies that were located in remote coastal areas that often made it difficult to drive them to the institution to be evaluated. Some fishermen after having just returned after spending several weeks at sea did not want to walk away from their families or in other words, participate. Fishermen who presented alterations in the ENT examination were excluded to avoid any changes that could affect the test.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.