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

Ram, G; Renuka

Page 19

Journal of MedVerse Research & Practice

nurexus.com

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

Worker

Dr. Sriram

1

, Dr. Renuka

2

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

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

ORIGINAL ARTICLE

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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

Study Design

A 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.

Study Setting & Duration

The study was conducted in selected small-scale industries in Trichy, including weaving units, sawmills,

printing presses, and lathe industries, between June 2023 and August 2024. These industries were selected

based on their prevalence and noise-generating potential.

Study Population

The study population included male and female workers employed in the selected industries. Workers were

required to have a minimum of one year of continuous employment in their respective industries.

Inclusion Criteria

Workers aged 18 years and above with at least one year of continuous employment in the selected

industries and who were willing to participate after providing informed consent were included in the study.

Exclusion Criteria

Workers with documented hearing loss before joining their current occupation, those with other known

causes of hearing loss such as cerumen impaction, chronic suppurative otitis media, or tympanic membrane

abnormalities, and those unwilling to participate were excluded.

Sample Size and Sampling Technique

The initial sample size was calculated as 786 based on a reported NIHL prevalence of 33.7% from Ruikar

MM et al., Government Medical College, Nagpur. Considering practical feasibility, a final sample size of

200 workers was included in the study. Industries that permitted access were identified and enlisted,

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following which eligible participants were selected using convenience sampling. Proportional

representation was maintained, with a greater number of workers recruited from weaving units because of

their higher worker density in the study area.

Data Collection Procedure

Data were collected using a structured and pretested interview schedule that included sociodemographic

characteristics, occupational history, type of industry, duration of employment, working hours per day, use

of hearing protective devices, symptoms of hearing loss, family history of hearing problems, and previous

hearing assessments. The questionnaire was validated through expert review and modified following a pilot

study conducted among 20 workers to ensure clarity and relevance.

All participants underwent clinical ear examination by a qualified ENT specialist using an otoscope to

exclude external and middle ear pathology. Tuning fork tests, including Rinne, Weber, and Absolute Bone

Conduction tests, were subsequently performed using a 512 Hz tuning fork. Workers suspected to have

hearing impairment were referred for pure tone audiometry (PTA), which was performed using a TRIVENI

TAM–25 audiometer at a certified hearing aid centre in Trichy. Audiometric assessment was performed

after 16 hours of cessation of noise exposure to minimize the effect of 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.

Noise Assessment

Noise levels at the selected industrial workplaces were measured using METRAVI SL–4010 mini sound

level meters. Multiple readings were obtained at each workplace during regular working hours, and the

average noise level was recorded for analysis.

Ethical Considerations

The study was conducted after obtaining informed consent from the participating workers. Confidentiality

of the collected information was maintained throughout the study. The specific Institutional Ethics

Committee approval details were not provided in the study description.

Statistical Analysis

The collected data were compiled using Microsoft Excel and analyzed using SPSS software version 26.0.

Descriptive statistics were used to summarize the study variables. The Chi-square test was applied to assess

associations between categorical variables. A p-value of less than 0.05 was considered statistically

significant.

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.

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Table 1: Sex Distribution of Workers

Sex

Adjusted Count

Percentage

Male

150

75.0%

Female

50

25.0%

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

Table 2: Literacy Status of Workers

Literacy Level

Adjusted Count

Percentage

Illiterate

23

11.5%

Primary school

52

26.0%

Secondary school

105

52.5%

College

20

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

89

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

30

15.0%

Ear pain

24

12.0%

Tinnitus

18

9.0%

Giddiness

3

1.5%

Pain and headache

3

1.5%

Pain & tinnitus

2

1.0%

Giddiness & headache

2

1.0%

Pain & giddiness

0

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

4

2.0%

No

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

11

100

0.018

> 8 Hours

25

64

Total

36

164

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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

< 45 Years

18

121

0.009

≥ 45 Years

18

43

Total

36

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

3

1.000

No

35

161

Total

36

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

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awareness, discomfort, and limited access.

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.

Strengths of the Study

The study assessed NIHL using both clinical examination and objective audiometric evaluation. Workplace

noise levels were additionally measured using sound level meters, allowing occupational noise exposure to

be assessed alongside hearing status. The use of a structured, pretested, and expert-reviewed data collection

tool and standardized ENT examination and audiometric procedures strengthened the reliability of the

findings. The study also included workers from multiple types of small-scale industries, providing a

broader assessment of occupational noise exposure in the study area.

Limitations of the Study

The final sample size of 200 was smaller than the initially calculated sample size of 786, which may reduce

the statistical power and generalizability of the findings. Convenience sampling may have introduced

selection bias. The study was conducted only among selected small-scale industries in Trichy, limiting the

applicability of the findings to other occupational settings. The assessment of hearing loss was cross-

sectional and therefore could not establish a temporal or causal relationship between occupational noise

exposure and hearing impairment.

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.

Declaration

Conflict of Interest: The authors declare that they have no competing interests or conflicts of interest

related to this work.

Funding: Nil

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