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 Table of Contents  
ORIGINAL ARTICLE
Year : 2016  |  Volume : 22  |  Issue : 1  |  Page : 14-18

Prevalence, awareness, and preventive practices of noise-induced hearing loss in a plywood industry


Department of Otorhinolaryngology, Yenepoya Medical College, Deralakatte, Mangalore, Karnataka, India

Date of Web Publication16-Feb-2016

Correspondence Address:
Mukesh Edward
Department of Otorhinolaryngology, Yenepoya Medical College, Deralakatte, Mangalore - 575 018, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0971-7749.176569

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  Abstract 

Introduction: Noise exposure is the most common preventable cause of occupational noise-induced hearing loss (NIHL); however, once acquired, it is irreversible. The predominant damage occurs to the hair cells and their associated nerves leading to the hearing loss. Objective: To determine the prevalence and also to evaluate the awareness and practices regarding prevention of occupational NIHL in the selected industry, to emphasize the critical importance of educating industry workers regarding NIHL and its prevention. Methodology: All staff working in the selected plywood industry excluding the ones with chronic otitis media were included. Relevant history, demographics, and clinical data were collected using prestructured questionnaire based proforma. All of them underwent pure tone audiometry. Results: Of 111 workers who were exposed to noise, 51.85% had NIHL, the average ambient noise being 80.5 dB. The most common complaints in workers with NIHL was hearing loss (52.6%), difficulty in hearing in noisy surroundings (43.9%), and difficulty in telephonic conversations (38.6%). There was a significant number (47.4%) who were asymptomatic. The majority had mild (56.1%) and moderate (38.6%) hearing loss. Majority of them with NIHL belonged to the age group of 30–60 years. This study showed a positive correlation between duration of noise exposure and degree of hearing loss. No one has ever used any sort of ear protection devices nor aware of health effects associated with noise exposure and its prevention. Conclusion: Considering zero awareness, screening, education, and prevention methods are emphasized to reduce the impact of noise exposure at workplace.

Keywords: Hearing conservation program, Noise exposure, Occupational noise-induced hearing loss


How to cite this article:
Edward M, Manohar S, Somayaji G, Kallikkadan HH. Prevalence, awareness, and preventive practices of noise-induced hearing loss in a plywood industry. Indian J Otol 2016;22:14-8

How to cite this URL:
Edward M, Manohar S, Somayaji G, Kallikkadan HH. Prevalence, awareness, and preventive practices of noise-induced hearing loss in a plywood industry. Indian J Otol [serial online] 2016 [cited 2021 Apr 19];22:14-8. Available from: https://www.indianjotol.org/text.asp?2016/22/1/14/176569


  Introduction Top


The term noise-induced hearing loss (NIHL) refers to reduction in auditory acuity associated with noise exposure. Noise exposure is the most common preventable cause of occupational NIHL; however, once acquired, it is irreversible. The predominant damage occurs to the hair cells and their associated nerves leading to the hearing loss. Hair cells along the cochlea map directly to the frequencies that humans can hear, with certain cells responding to low frequencies, others to high frequencies. When hair cells are repeatedly exposed to excessive stimulation from intense sound, they become fatigued and fail to respond properly. This manifests as a temporary hearing loss after noise exposure known as temporary threshold shift, which recovers within 16–24 h of the exposure. If the excessive stimulation is repeated or sustained for long enough, the hair cells are permanently damaged or die. Hair cells cannot regenerate, and they currently cannot be repaired or replaced by treatments, meaning that NIHL is permanent, called permanent threshold shift.[1],[2]

The patient is far more likely to be male, usually in early middle age.[1],[3] A long-standing observation in NIHL has been that some ears are more easily damaged by noise than others.[4]

Individuals with NIHL may experience significant morbidity due to hearing loss, concomitant tinnitus, and/or impaired speech discrimination adversely affecting worker's communication and safety leading to depression, social isolation, and accidents.[5],[6] Control measures at source, path, and persons exposed to hazards are the means of preventing occupational diseases and injuries among workers. However, worker's awareness and knowledge about job associated hazards and personal protective equipment will reduce risks of some occupational hazards.[7]

Occupational NIHL may result when there is prolonged constant exposure to noise of 85 dB or more for 8 h/day or 40 h/week exposure. At this level of exposure, the employer is obliged to monitor the hearing of his workforce and the noise levels. When the noise level reaches 90 dB or more, the employer should provide a hearing conservation program (HCP).[8]

The World Health Organization reports that occupational NIHL is second only to accidental injury in terms of years of healthy life lost.[9] Many countries enforce general health and safety legislation that specifies maximum exposure levels and requirements for action, including noise assessments, regular audiometric testing, protective equipment, and monitoring, which are intended to protect both workers and the public from excessive noise exposure.[10]

The cornerstone of investigation is a pure tone audiogram, with both air and bone conduction to identify and quantify the hearing loss. The usual clinical frequencies should be tested as well as 3 and 6 kHz. The classical audiometric pattern is of a high-tone hearing loss with a notched appearance centered on 4 or 6 kHz, with some recovery at 8 kHz. However, the notch is often absent, but a significant audiometric loss at frequencies below 2 kHz is uncommon.[11],[12] In older population, the effects of noise may be difficult to distinguish from age-related hearing loss (presbycusis) without access to previous audiograms.[13]

This study was conducted to know the prevalence of NIHL in an industry in South India. The awareness and practices regarding NIHL were also taken into account.

Objectives

  • To determine the prevalence of occupational NIHL in the selected industry
  • To evaluate the awareness and practices regarding prevention, of NIHL in the selected industry
  • To emphasize the critical importance of educating industry workers regarding NIHL and its prevention.


Study design

This is a cross-sectional study carried out by the Department of Otorhinolaryngology of a Tertiary Care Medical College.

Subjects

All the staff working in the selected plywood industry located in the outskirts of a city.

Inclusion criteria

  • All the staff working in the selected plywood industry.


Exclusion criteria

  • Staff with chronic otitis media or other causes suggestive of conductive/sensorineural hearing loss
  • Staff who do not give consent to the study.


Ethics

Ethical clearance was granted by Institutional Ethics Committee.


  Methodology Top


  • Written informed consent was obtained
  • Relevant clinical data and demographics including history were obtained and detailed ear examination performed in the selected subjects
  • Ambient noise level in the factory was obtained prior to the examination of the subjects
  • Prestructured questionnaire based proforma, validated by discussion in the Department of Otorhinolaryngology, was used to collect data
  • Pure tone audiometry was done in a suitable place with calibration where ambient noise is least using Elkon 3N3 Milli pure tone audiometer.



  Results and Analysis Top


There were 114 workers in the selected plywood industry. The study included 111 cases, and 3 cases were excluded as they had chronic otitis media.

Ambient noise level in the factory obtained was 77.7–83.5 dB (average 80.5 dB).

Of 111 cases, 57 workers were confirmed with NIHL (51.4%). All the workers with NIHL were males and was statistically significant (P = 0.023). In total, there were only seven females [Table 1].
Table 1: Gender versus NIHL


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The lowest age of the subject confirmed with NIHL is 20 years and the highest is of 66 years. The average age in years of the 57 patients confirmed with NIHL is 46.35.

In workers with NIHL, the most common symptom was hearing loss seen in 30 (52.6%), closely followed by difficulty in hearing in noisy surroundings in 25 (43.9%), and difficulty in telephonic conversations in 22 (38.6%). Twelve (21.1%) were adversely affected with social life. There were no symptoms in a significant number (47.4%) [Table 2].
Table 2: Symptoms associated with NIHL


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With respect to degree of hearing loss, 32 workers (56.1%) had only a mild hearing loss and 22 (38.6%) had moderate hearing loss. The rest 3 workers (5.3%) have moderate to severe hearing loss [Table 3].
Table 3: Degree of hearing loss in NIHL


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There was a positive correlation between duration of noise exposure and degree of hearing loss. That is, with increase in number of years and hours of noise exposure, there was an increase in prevalence of NIHL [Table 4].
Table 4: Duration of noise exposure versus degree of NIHL


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There was a positive correlation between presbycusis (age-related hearing loss) and NIHL, which was statistically significant (P = 0.001) [Table 5].
Table 5: Presbycusis versus NIHL


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None of the workers were aware that noise can cause hearing loss. In addition, preventive measures were not practiced by anyone as well.


  Discussion Top


NIHL is a commonly seen occupational hazard. The sound pressure levels (SPLs) that are required to produce hearing loss are much less compared to what is required to cause discomfort to the exposed individual, so the affected person is unaware that his hearing is being damaged.[14]

A study by Ahmed concluded that about 89% of the workers were exposed daily above the permissible level which is 85 dB and 45% of them had never used any hearing protection devices. About 58% of the workers experienced a moderate or high degree of noise annoyance. Only 4.1% and 1.9% of the workers were aware of the health effects of noise and the methods of prevention, respectively, and awareness was positively associated with noise exposure.[15]

Musiba identified in her study that the prevalence of NIHL was 47% with 12% poor hearing and 35% mild hearing impairment. Furthermore, the proportion of NIHL increased with total years of exposure to noise. Underground miners were more affected (71%) than open pit miners (28%). The highest proportion of miners with NIHL (60%) was among the youngest age group (20–29 years).[16]

Nelson et al. said that the effects of the exposure to occupational noise are larger for males than females in all subregions and higher in the developing regions. Moreover, occupational noise is a significant cause of adult-onset hearing loss. The majority of this NIHL burden can be minimized by reducing the generation of noise at its source.[17]

In a study, Lalande et al. concluded that NIHL is found far more often in men and produces particular difficulties in social functioning. There is often a history of social withdrawal although this will rarely be volunteered. There is often increasing reliance on the spouse for social and family interaction and this can lead to marital stress. There may be embarrassment, loss of confidence, anxiety, and frank depression.[3]

Rabinowitz mentioned in his study that noise can cause permanent hearing loss at chronic exposures equal to an average SPL of 85 dB or higher for an 8-h period. Based on the logarithmic scale, a 3 dB increase in SPL represents a doubling of the sound intensity. Therefore, 4 h of noise exposure at 88 dB is considered to provide the same noise “dose” as 8 h at 85 dB.[18]

In their study, Kirchner et al. stated that the occupational and environmental medicine physicians should understand a worker's noise exposure history and become proficient in the early detection and prevention of NIHL. Also states that hearing loss due to continuous or intermittent noise exposure increases most rapidly during the first 10–15 years of exposure, and the rate of hearing loss then decelerates as the hearing threshold increases. This is in contrast to age-related loss, which accelerates over time.[19]

Shrestha et al. in their study found that age has a cumulative effect on hearing loss. Furthermore, duration of service gives an additive effect to noise in causing NIHL. Frequency area 4–6 kHz is usually affected first with maximum at 4 kHz. Any level of NIHL may muffle high-frequency sounds such as whistles or buzzers and may result in difficulty discriminating speech consonant sounds such as those in the words fish and fist, particularly in noisy environments with background noise, many voices, or room reverberation.[20]

In a study, Reilly et al. stated that the number of patients with occupational NIHL is likely a gross underestimate of the true magnitude of the disease. However, the surveillance system has identified workplaces with hazardous levels of noise and no HCP, thereby protecting similarly exposed coworkers of the index patients from further exposures to noise and hearing loss.[21]

Steenkamp in his study concluded that while noise continues, second-level noise control (hearing conservation) needs to be effective. To make this work, a new management approach, re-engineering, redesign, and new HCP technology are required.[22]

Contributors to a Cochrane collaboration review concluded that “higher quality prevention programs, quality studies, and better implementation of legislation are needed to prevent NIHL.”[23]

An HCP has four main features: sound measurement, engineering and administrative controls, personal hearing protection, and audiometric monitoring of the population at risk, with the following elements: noise hazard identification, engineering controls, personal hearing protection, monitoring, record keeping, health education, enforcement, and program evaluation. A good HCP is multidisciplinary involving the industrial hygienist, engineer, nurse, audiometric technician, and frequently supervisory audiologist and otologist.[24]

Sataloff and Sataloff mentioned in their study that techniques for advancing and implementing technology to control environmental noise require greater research and development. They concluded that otolaryngologists should continue to serve as advocates for prevention of occupational hearing loss and other preventable causes and should continue to collaborate with basic scientists, engineers, geneticists, audiologists, occupational physicians, and the many other professionals whose insights and actions should eventually eliminate occupational noise as a cause of hearing impairment.[25]

In this study, out of 111 workers who were exposed to noise, 57 (51.85%) had NIHL, the average ambient noise being 80.5 dB. Forty-nine (44.15%) were bilateral and 8 (7.2%) were unilateral NIHL with equal distribution in the right and left sides. This must be due to machine operators where one ear is near to the machine. Majority (84.2%) of them with NIHL belonged to the age group of 30–60 years. All of them with NIHL were males. There were comparatively less female workers, but none had NIHL.

The most common complaints in workers with NIHL was hearing loss (52.6%), difficulty in hearing in noisy surroundings (43.9%) and difficulty in telephonic conversations (38.6%). Few of them (21.1%) were adversely affected with social life as well. There was a significant number (47.4%) who were asymptomatic.

The majority (56.1%) of them with NIHL had mild, followed by moderate hearing loss (38.6%). This study showed a positive correlation between duration of noise exposure and degree of hearing loss and also between presbycusis and NIHL.

No one has ever used any sort of ear protection devices nor was knowing the health effects associated with noise exposure, showing that the awareness regarding NIHL and its prevention was zero.


  Conclusion Top


This study shows that occupational NIHL is still prevalent in significant number. Even though noise has been shown to cause hearing loss for centuries,[26] and serious efforts were made to reduce excessive noise at work for past 40 years.

Access to state-of-art machines will be a distant dream to majority of the industries in developing and underdeveloped nations. Even most modern engineering may result in near similar morbidity if the practice of awareness is not employed among the workers and the communities exposed to industrial or any other means of noise pollution.

As our study showed zero awareness regarding NIHL and prevention among the noise-exposed workers, the need for health education and prevention methods such as providing ear plugs, ear muffs, regular audiometric screening, adopting legislative standards in exposure time of noise, and implementation of the same is critically advocated.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

1.
Consensus.nih.gov. The National Institutes of Health (NIH) Consensus Development Program: Noise and Hearing Loss; 2015. Available from: https://www.consensus.nih.gov/1990/1990NoiseHearingLoss076html.htm. [Last cited on 2015 Sep 10].  Back to cited text no. 1
    
2.
Dobie RA, editor. Ear and hearing. Medical-legal Evaluation of Hearing Loss. 2nd ed., Vol. 22. Philadelphia: Singular/Thomson Learning; 2001. p. 548-9.  Back to cited text no. 2
    
3.
Lalande NM, Lambert J, Riverin L. Quantification of the psychosocial disadvantages experienced by workers in a noisy industry and their nearest relatives: Perspectives for rehabilitation. Audiology 1988;27:196-206.  Back to cited text no. 3
    
4.
Flint P, Haughey B, Niparko J, Richardson M, Lund V, Robbins K, et al. Cummings Otolaryngology – Head and Neck Surgery. Vol. 151. London: Elsevier Health Sciences; 2010. p. 2140-53.  Back to cited text no. 4
    
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Hétu R, Getty L, Quoc HT. Impact of occupational hearing loss on the lives of workers. Oxford Journals, Occupational Medicine 1995;10:495-512.  Back to cited text no. 5
    
6.
Zwerling C, Whitten PS, Davis CS, Sprince NL. Occupational injuries among older workers with visual, auditory, and other impairments. A validation study. J Occup Environ Med 1998;40:720-3.  Back to cited text no. 6
    
7.
Scott-Brown W, Gleeson M. Scott-Brown's Otorhinolaryngology, Head and Neck Surgery. Vol. 238b. England: Edward Arnold; 2008. p. 3548-57.  Back to cited text no. 7
    
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Roland N, McCombe A, McRae R. Key Topics in Otolaryngology and Head and Neck Surgery. Oxford: BIOS; 2001. p. 192-3.  Back to cited text no. 8
    
9.
Kooistra R. Critical Review: The Effectiveness of Hearing Conservation Initiatives on the Incidence of Noise Induced Hearing Loss Amongst. Industrial Workers. University of Western Ontario; 2015. Available from: https://www.uwo.ca/fhs/csd/ebp/reviews/2011-12/Kooistra.pdf. [Last cited on 2015 Sep 10].  Back to cited text no. 9
    
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11.
Coles RR, Lutman ME, Buffin JT. Guidelines on the diagnosis of noise-induced hearing loss for medicolegal purposes. Clin Otolaryngol Allied Sci 2000;25:264-73.  Back to cited text no. 11
    
12.
Robinson DW. The audiogram in hearing loss due to noise: A probability test to uncover other causation. Ann Occup Hyg 1985;29:477-93.  Back to cited text no. 12
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13.
Consensus conference. Noise and hearing loss. JAMA 1990;263:3185-90.  Back to cited text no. 13
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14.
Nair S, Kashyap R. Prevalence of noise induced hearing loss in Indian air force personnel. Med J Armed Forces India 2009;65:247-51.  Back to cited text no. 14
    
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Ahmed H. Noise exposure, awareness, practice and noise annoyance among steel workers in United Arab Emirates. The Open Public Health Journal Open 2012;5:28-35.  Back to cited text no. 15
    
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Nelson DI, Nelson RY, Concha-Barrientos M, Fingerhut M. The global burden of occupational noise-induced hearing loss. Am J Ind Med 2005;48:446-58.  Back to cited text no. 17
    
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20.
Shrestha I, Shrestha BL, Pokharel M, Amatya RC, Karki DR. Prevalence of noise induced hearing loss among traffic police personnel of Kathmandu Metropolitan City. Kathmandu Univ Med J (KUMJ) 2011;9:274-8.  Back to cited text no. 20
    
21.
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22.
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Verbeek V, Kateman, Morata, Dreschler, Mischke. 260 Interventions to prevent occupational noise-induced hearing loss – A Cochrane review. Occup Environ Med 2013;70 Suppl 1:16-7.  Back to cited text no. 23
    
24.
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25.
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26.
Thurston FE. The worker's ear: A history of noise-induced hearing loss. Am J Ind Med 2013;56:367-77.  Back to cited text no. 26
    



 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]


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