Burden of Noise-Induced Hearing Loss in the Small-Scale Industrial Worker

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Journal of MedVerse Research & Practice

nurexus.com

Burden of Noise-Induced Hearing Loss in the Small-Scale Industrial

Worker

Dr. Sriram

, Dr. Renuka

Professor, Assistant Professor

Department of ENT, Dhanalakshmi Srinivasan Medical College, Trichy.

Email ID: sriram452@gmail.com

Submission Date: 25.04.2025

Accepted Date: 21.05.2025

Published Date: 31.05.2025

article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits

unrestricted use, distribution, and reproduction in any medium, provided the original author(s) and source are credited.

Abstract

Background: Noise-induced hearing loss (NIHL) remains a major occupational health concern, especially among

workers in unregulated small-scale industrial settings. Prolonged exposure to loud machinery noise without adequate

protective measures significantly increases the risk of hearing impairment. This study aimed to determine the

prevalence of NIHL and identify related risk factors among workers in small-scale industries in Trichy.

Methods: A cross-sectional community-based study was carried out among 200 employees working for at least one

year in weaving units, sawmills, printing presses, and lathe workshops. Participants were chosen through

convenience sampling. Data were gathered using a pre-validated structured questionnaire, followed by ear

examinations, tuning fork tests, and pure tone audiometry. Workplace noise levels were recorded using a sound level

meter. Statistical analysis was done using SPSS version 26.0, applying chi-square tests to identify significant

associations. A p-value below 0.05 was considered statistically significant.

Results: The study revealed an 18% prevalence of hearing loss. Significant associations were noted between hearing

loss and working more than 8 hours per day (p = 0.018), and among workers aged 45 years or older (p = 0.009). Only

2% of participants used hearing protection. Frequently reported symptoms included headaches (15%), ear pain

(12%), and tinnitus (9%). No statistically significant correlation was found between hearing loss and use of

protective devices (p = 1.000), likely due to the very limited usage.

Conclusion: This study highlights a notable burden of occupational hearing loss among small-scale industry workers

in Trichy. Extended work hours and increasing age emerged as major contributors. The extremely low use of hearing

protection indicates an urgent need for awareness campaigns, routine hearing checks, and stricter enforcement of

workplace safety norms to mitigate long-term auditory damage in this at-risk population.

Keywords: Noise-induced hearing loss, occupational noise exposure, small-scale industries, hearing protection

Introduction

Noise-Induced Hearing Loss (NIHL) remains a prominent occupational hazard worldwide, particularly

affecting individuals working in environments with high levels of continuous or intermittent noise exposure

[1]. Among these vulnerable groups, small-scale industrial workers are notably at risk due to poor

occupational safety measures, limited awareness, and inadequate implementation of preventive strategies

[2]. NIHL typically results from prolonged exposure to sound levels above 85 decibels (dB), leading to

irreversible damage to the hair cells [3,4].

In many low- and middle-income countries, including India, small-scale industries play a major role in the

economy and employ millions

[5,6]. However, these sectors are often overlooked in terms of occupational

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health surveillance. Workers in textile manufacturing, metal works, sawmills, construction, and weaving

factories are frequently subjected to hazardous noise without proper protective equipment or regular

hearing assessments

[7-10]. The lack of structured occupational health policies in small-scale industries

further exacerbates the risk [11].

Several regional and international studies have highlighted the alarming prevalence of NIHL in industrial

environments. In Puducherry, India, a study among construction workers revealed a 13.2% prevalence of

NIHL, with the most affected individuals being those with longer job durations and no use of ear protection

[12,13,14]. A similar pattern was noted in West Bengal among textile workers, where noise levels exceeded

100 dB and contributed significantly to hearing threshold shifts

[15,16]. Furthermore, studies from other

countries mirror these findings. Research in Malaysia found that 42.7% of palm oil mill workers suffered

from NIHL, while in Ethiopia, over 20% of industrial workers in metal and woodworking industries

reported symptoms consistent with hearing impairment

[17,18].

The public health burden of NIHL is not limited to hearing disability alone. Affected individuals often face

reduced productivity, impaired communication, and diminished quality of life. Moreover, the economic

implications include increased healthcare costs and loss of skilled labour due to premature disability

[19].

Despite this, NIHL is largely preventable. Regular auditory screening, proper use of protection devices

(HPDs), and enforcement of noise regulation standards can significantly reduce its prevalence [20].

Unfortunately, the importance of hearing conservation remains low among small-scale industrial workers.

Many workers are unaware that hearing damage may occur gradually and may not be immediately

noticeable. Additionally, informal employment arrangements in these sectors often exclude workers from

routine health checks or compensation for occupational illnesses [21,22].

Given this context, assessing the burden of NIHL in small-scale industries. A systematic evaluation of

noise exposure levels, prevalence of hearing loss, and existing protective practices among these workers

will aid in strengthening occupational health policies and promoting safer work environments.

Materials & Methods

This community-based cross-sectional study was conducted to assess the burden of noise-induced hearing

loss (NIHL) among workers employed in small-scale industries in Trichy. The study population included

both male and female workers who had been employed for at least one year in weaving units, sawmills,

printing presses, and lathe industries. These industries were selected based on their prevalence and noise-

generating potential.

The inclusion criteria for participation were workers aged 18 years and above with a minimum of one year

of continuous employment in the selected industries and a willingness to participate after informed consent.

Exclusion criteria included those with documented hearing loss before joining their current job, workers

with other known causes of hearing loss such as cerumen impaction, chronic suppurative otitis media

(CSOM), tympanic membrane abnormalities, or those unwilling to participate in the study.

The study was conducted between June 2023 and August 2024. Although an initial sample size of 786 was

calculated based on a reported NIHL prevalence of 33.7% (Ruikar MM et al., Government Medical

College, Nagpur), a final sample size of 200 was chosen for practicality and feasibility. Industries that

permitted access for the study were first identified and enlisted. From these, eligible participants were

selected using a convenience sampling method. Proportional representation was ensured, with a greater

number of workers recruited from weaving units due to their higher density in the area.

Data collection was carried out using a structured and pretested interview schedule. The tool gathered

sociodemographic information, work-related history such as type of industry, years of employment,

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working hours per day, and use of hearing protective devices. It also included questions regarding

symptoms of hearing loss, family history of hearing problems, and previous assessments for hearing

impairment. The tool was validated through expert review and modified after a pilot study with 20 workers

to ensure clarity and relevance.

All study participants underwent a clinical ear examination performed by a qualified ENT specialist using

an otoscope to rule out external and middle ear pathologies. This was followed by tuning fork tests (Rinne,

Weber, and Absolute Bone Conduction) using a 512 Hz tuning fork. Workers with suspected hearing

impairment based on these tests were referred for pure tone audiometry (PTA), which was conducted using

the TRIVENI TAM–25 audiometer at a certified hearing aid center in Trichy. Audiometric testing was

done 16 hours after cessation of noise exposure to eliminate temporary threshold shifts. Hearing thresholds

were assessed at 500 Hz, 1000 Hz, 2000 Hz, and 3000 Hz, and the average threshold level was used to

determine the degree of hearing loss.

In addition, noise levels in the various industrial workplaces were measured using the METRAVI SL– 4010

mini sound level meters. Multiple readings were taken at each location during regular working hours, and

the average noise level was recorded. The collected data were compiled using Microsoft Excel and

subsequently analyzed with SPSS software version 26.0. Descriptive statistics were employed to present

the data summaries, while chi-square tests were utilized to assess relationships between variables. A p-

value below 0.05 was regarded as indicative of statistical significance.

Results

Figure 1: Age Distribution of Workers (n = 200)

The majority of workers were in the 36 to 45-year age group, followed by those aged 25–35. Workers

above 55 years made up a small proportion of the workforce.

Table 1: Sex Distribution of Workers

Sex

Adjusted Count

Percentage

Male

150

75.0%

Female

25.0%

The workforce was predominantly male, reflecting gender patterns in small-scale industrial employment.

30%

40%

25%

5.5%

10%

15%

20%

25%

30%

35%

40%

45%

25–35 36–45 46–55 56–65

Percentage

Age

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Table 2: Literacy Status of Workers

Literacy Level

Adjusted Count

Percentage

Illiterate

11.5%

Primary school

26.0%

Secondary school

105

52.5%

College

10.0%

The majority of participants (52.5%) had a secondary school education, followed by 26% with primary

school education. Only 10% had attended college, while 11.5% were illiterate. This shows that most

individuals had basic to moderate levels of education.

Table 3: Work Hours per Day

Work Hours

Adjusted Count

Percentage

≤ 8 Hours

111

55.5%

> 8 Hours

44.5%

A significant portion of the workers (almost 45%) were working for more than 8 hours per day, possibly

increasing their exposure risk.

Table 4: Symptoms Related to Hearing and Noise Exposure

Symptom

Adjusted Count

Percentage

Headache

15.0%

Ear pain

12.0%

Tinnitus

9.0%

Giddiness

1.5%

Pain and headache

1.5%

Pain & tinnitus

1.0%

Giddiness & headache

1.0%

Pain & giddiness

0.0%

The most common symptom was headache (15%), followed by ear pain (12%) and tinnitus (9%). Less

frequent symptoms included combinations such as pain and headache (1.5%), pain & tinnitus (1%), and

giddiness & headache (1%). Giddiness alone was reported by 1.5% of participants, and no cases of

combined pain & giddiness were observed.

Table 5: Use of Protective Hearing Devices

Use of Protective Devices

Adjusted Count

Percentage

Yes

2.0%

196

98.0%

Only a very small proportion of workers used hearing protection, pointing to poor awareness or

accessibility to protective measures.

Table 6: Association Between Work Hours and Hearing Loss

Work Hours

Hearing Loss (Yes)

Hearing Loss (No)

p-value

≤ 8 Hours

100

0.018

> 8 Hours

Total

164

There was a statistically significant association between longer work hours (>8 hours) and the prevalence

of hearing loss (p < 0.05).

Table 7: Association Between Age Group and Hearing Loss

Age Group

Hearing Loss (Yes)

Hearing Loss (No)

p-value

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< 45 Years

121

0.009

≥ 45 Years

Total

164

Hearing loss was significantly higher among workers aged 45 years and above (p < 0.01), indicating age-

related vulnerability to occupational noise exposure.

Table 8: Association Between Use of Protective Devices and Hearing Loss

Use of Protective Device

Hearing Loss (Yes)

Hearing Loss (No)

p-value

Yes

1.000

161

Total

164

There was no significant association between the use of protective devices and hearing loss in this sample.

However, the extremely low usage of protection (only 4 individuals) may limit the validity of this

comparison.

Discussion

This study assessed the prevalence and risk factors associated with noise-induced hearing loss (NIHL)

among 200 small-scale industrial workers employed in weaving units, sawmills, printing presses, and lathe

workshops in and around Kanchipuram. The findings demonstrate a significant occupational health burden,

with 18% of the workers showing evidence of hearing loss, a pattern that aligns with global occupational

health concerns in unregulated work environments.

The proportion of workers affected by NIHL in this study is comparable to that reported by Rahman et al

[23] in a study conducted among palm oil mill workers in Malaysia, where the prevalence was found to be

17.8%. Similarly, Sinha et al [24] documented a prevalence of 13.2% among construction workers in

Puducherry, India, indicating a consistent trend of hearing impairment in noisy occupational settings,

especially where hearing conservation programs are absent or poorly enforced.

A notable correlation was identified between extended working hours and the presence of hearing loss (p =

0.018). This aligns with findings from Mirza et al [25], who demonstrated that exposure to industrial noise

for more than eight hours daily significantly elevated the risk of hearing impairment. In the current study,

44.5% of workers reported daily work durations exceeding eight hours, potentially amplifying their overall

noise exposure and associated health risks.

Age also played a critical role in the development of hearing loss. Workers aged 45 years and above had

significantly higher rates of NIHL (p = 0.009), which supports findings by Mlynski et al [26] in Tanzanian

iron and steel workers, where age and duration of exposure were key determinants of auditory impairment.

This relationship could be attributed to age-related cochlear degeneration in combination with chronic

occupational exposure.

Interestingly, although the use of hearing protection was extremely limited—only 2% of workers reported

using any form of protective device—there was no statistically significant difference in hearing loss

between users and non-users (p = 1.000). This result, while unexpected, is likely due to the small number of

workers using protection, which restricts the power of the analysis. A study in Ethiopia by Mulatu et al [27]

also highlighted low compliance with hearing protection among industrial workers, attributing it to lack of

awareness, discomfort, and limited access.

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The presence of symptoms such as headache, ear pain, and tinnitus in a considerable number of participants

further underscores the health impact of occupational noise exposure. Similar patterns were observed by

Thapa et al [28] in Nepalese woodworkers, where tinnitus and headache were among the most frequently

reported symptoms.

Overall, our findings reflect the need for stronger enforcement of occupational safety measures, including

mandatory use of hearing protective devices, periodic auditory screening, and health education. Special

attention must be given to workers in unorganized sectors who are often neglected in policy interventions.

Future research should also explore longitudinal outcomes to better understand the progression of NIHL

and the effectiveness of preventive strategies.

Conclusion

This study found that 18% of small-scale industrial workers in had noise-induced hearing loss (NIHL).

Significant associations were observed between NIHL and longer work hours, as well as older age,

indicating the cumulative effect of noise exposure over time. These findings highlight the urgent need for

regular hearing assessments, mandatory use of protective devices, and stronger enforcement of

occupational safety measures to prevent NIHL in vulnerable industrial populations.

Conflict of Interest: Nil

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