Occupational exposure and health risks among traditional copper bell makers in India: a comprehensive assessment with policy and preventive implications

Abstract

Purpose

This study aimed to assess occupational exposures and health outcomes among traditional copper bell makers in Bhuj, Gujarat.

Methods

A cross-sectional design was used to evaluate 89 copper bell makers through environmental monitoring and clinical assessments. Workplace exposures assessed included respirable dust and PM2.5, personal and area noise levels, and heat stress. Corresponding health evaluations included spirometry for respiratory function, audiometry for hearing assessment, and structured questionnaires to capture musculoskeletal and other symptoms.

Results

Respirable dust concentrations (mean 4.93 ± 1.36 mg/m³) exceeded recommended limits, with 16.4% of workers showing abnormal lung function. Personal noise exposure levels were within OSHA (Occupational Safety and Health Administration) limits; however, peak noise during hammering reached 148 dB(C), and high-frequency noise exposure corresponded with a high prevalence (80.7%) of high-frequency hearing loss. WBGT (Wet Bulb Globe Temperature) values near coal-fired furnaces surpassed NIOSH thresholds, indicating considerable risk of heat strain. Musculoskeletal symptoms were reported by 70% of participants.

Conclusion

The study highlights multi-dimensional occupational risks, the need for strengthening occupational health services and targeted interventions in informal artisanal sectors. Craft-specific Standard Operating Procedures and Periodic Medical Examination tools were developed and provided to the Handicrafts Service Centre, extending policy support to artisan sectors.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-026-27657-x.

What are the policy implications of the paper?

This paper presents the first comprehensive field-based assessment of occupational exposures and health outcomes among copper bell makers in India. Using standardized clinical and environmental methods, it links specific hazards with job roles and proposes evidence-based, craft-specific Standard Operating Procedures (SOPs) for copper bell makers. The findings have informed state-level policy discussions, offering a model for occupational health interventions in artisan sectors.

Introduction

The artisanal sector, particularly handicrafts, constitutes a vital pillar of India’s rural economy, providing livelihoods to millions and contributing substantially to the country’s Gross Domestic Product (GDP) and exports [1]. Artisanal crafts, as recognized by UNESCO (United Nations Educational, Scientific and Cultural Organization) and the International Labour Organization (ILO), are characterized by small-scale, labour-intensive production, often within informal, family-based settings and using traditional techniques [2]. Among the diverse crafts practiced in India, copper bell making holds a unique place, especially in regions such as Kutch-Bhuj in Gujarat, where it is both a cultural legacy and a crucial source of income for local communities.

Despite its economic and cultural significance, the working environment in copper bell making is fraught with occupational hazards. The fabrication process involves activities such as constant heating, metal beating, and soldering, which expose artisans to multiple physical and chemical risks [3]. Artisans are commonly subjected to excessive heat from open furnaces, inhalation of metal fumes and dust, high-intensity noise from hammering, and poor ergonomic conditions due to repetitive manual tasks and awkward postures [3–5]. These conditions are exacerbated by the informal nature of the sector, where work is often performed in confined, poorly ventilated spaces, and the use of personal protective equipment (PPE) is rare due to lack of awareness or resources.

Evidence from studies in India and other low- and middle-income countries has highlighted the health risks such as musculoskeletal pain, respiratory symptoms, hypertension, and vision disorders faced by metal workers and artisans [6]. Furthermore, the physical demands and environmental conditions of metal crafts are associated with increased risk of heat-related illnesses, noise-induced hearing loss, and cumulative musculoskeletal disorders [3, 4, 7, 8].

Despite the recognition of these hazards, there remains a significant gap in systematic, context-specific research on the occupational exposures and health outcomes among copper bell makers, particularly in the informal clusters of western India. Most available studies are either limited in scope, focus on broader categories of metal workers, or lack comprehensive exposure assessment and health evaluation. There is also limited evidence on the occupational SOPs (Standard Operating Procedure) tailored to the unique challenges of artisanal settings, where formal occupational health and safety regulations are seldom enforced.

Given the economic vulnerability, low literacy, and lack of access to occupational health services among artisan workers, there is a pressing need to generate robust evidence on workplace hazards and their health impacts in this sector. A comprehensive assessment of exposures and health outcomes among copper bell makers is essential not only to inform preventive interventions and policy measures but also to safeguard the sustainability of this culturally significant craft. This study was therefore undertaken to systematically evaluate the occupational hazards and health risks faced by copper bell makers in Bhuj, Gujarat, addressing a critical gap in the literature and providing a foundation for targeted occupational health strategies.

Methods

Study design and setting

This research employed a cross-sectional observational design to assess workplace exposures and health hazards among copper bell makers in the Kutch-Bhuj district of Gujarat, India. The study focused specifically on artisan clusters located in the villages of Zura and Kunariya, which are recognized centres for traditional copper bell making. The study was conducted between January 2023 and January 2025. The study adhered to the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) guidelines for cross-sectional reporting [9].

Traditional copper bell making in Bhuj is a manual, multi-step process (Fig. 1) carried out in small home-based workshops. Workers are often seated on traditional floor arrangements that are not ergonomic. The nature of their work results in exposure to continuous hammering noise, coal smoke, heat stress, and physical strain, posing significant occupational health risks. A task-based hazard assessment was conducted based on field observations and supported by existing literature. Major work processes were categorized into key job groups, and for each, potential hazards and related health outcomes were identified. The hazard assessment framework is summarized in Table 1.

Fig. 1.

Flowchart illustrating the stepwise process of traditional copper bell making

Table 1.

Task-based hazard assessment of occupational exposures and potential health outcomes among copper bell makers

Job title	Procedure / Task	Identified Hazards	Potential Health Outcomes
Bell Metal Tipping	Metal cutting, tipping/hammering, shaping, assembly, tuning	Sharp edges, high-intensity noise, repetitive work	Injuries, noise-induced hearing loss, musculoskeletal disorders, respiratory diseases
Powder Coating	Mud coating, brass/copper powder application	Metal dust, dermal exposure, wet work, repetitive task	Skin diseases, respiratory diseases, musculoskeletal disorders
Coal Fire Furnace	Furnace firing, cooling, cleaning, polishing	Heat, coal smoke, metal fumes, dust, awkward posture	Respiratory diseases, eye irritation, kidney symptoms, musculoskeletal disorders

Study population and sample size

The study population consisted of copper bell makers with a minimum of two years’ experience in the craft, who provided written informed consent to participate. Individuals were excluded if they had a history of acute respiratory infection in the preceding two weeks, were physically or mentally unable to participate in examinations, or had contraindications to spirometry or audiometry procedures.

A total of 89 copper bell makers were enrolled, representing the available workforce in the selected clusters and providing broad coverage for the assessment of occupational exposures and health outcomes. Dust exposure assessments were conducted on workers operating near coal-powered furnaces, where particulate matter was most concentrated. For personal noise exposure assessment, a sub-sample of nine workers engaged in manual hammering of bells of various traditional sizes (ranging from size 2 to 10) was purposively selected to capture variability in exposure. For area noise monitoring, three copper bell making units were selected (bell sizes of 6, 9 and 12). The distribution of participants and sample sizes for various exposure assessments across job tasks, along with workplace settings and corresponding health outcomes, is summarized in Table 2.

Table 2.

Distribution of sample sizes for different job tasks, exposure assessments, workplace settings, and health outcomes

Job Task / Process	Exposure Assessment	Workplace setting	Related Health Outcome
Bell metal tipping / hammering (n = 47)	Personal noise dosimetry (n = 9); area noise octave band analysis (n = 3)	Indoor workshop	Hearing loss (n = 31) Respiratory symptoms (n = 47) Lung function (n = 44) Musculoskeletal disorders (n = 47)
Powder coating (n = 26)	Exposure to mud slurry	Open courtyard workspace	Hearing loss (n = 11) Respiratory symptoms (n = 26) Lung function (n = 13) Dermatological symptoms (n = 26) Musculoskeletal disorders (n = 26)
Coal fire furnace (n = 16)	Heat stress (n = 3); dust sampling (n = 5)	Semi-open furnace workstation	Hearing loss (n = 15) Respiratory symptoms (n = 16) Lung function (n = 16) Kidney-related symptoms (n = 16) Musculoskeletal disorders (n = 16)

Data collection tools

Questionnaire

A structured questionnaire administered in the local language was used to capture sociodemographic details (including age, sex, education, income, and residence), occupational history (nature and duration of work, daily hours, use of personal protective equipment), medical and family history, and personal habits such as tobacco use and dietary patterns. The questionnaire also included items on self-reported eye, skin, and kidney-related symptoms to capture additional health effects associated with occupational exposures.

Dust exposure assessment

Respirable dust was measured using SKC SideKick-51MTX pumps at 2.2 L/min, equipped with cyclones and 37 mm polyvinyl chloride (PVC) filters with a 5 μm pore size. Sampling was primarily conducted near coal-fired furnaces – identified as key dust-generating sites in the copper bell workshops. Filters were conditioned in a desiccator for 24 h, pre-weighed using a precision microbalance (Shimadzu AUX-220, 0.001 g resolution), and placed in a plastic cyclone attached to a personal sampling pump. The assembly was worn in the worker’s breathing zone and flow calibrated pre- and post-shift using a rotameter (SKC Ltd., UK). Post-sampling, filters were reweighed, and the full-shift 8-hour time-weighted average (TWA) concentration was calculated gravimetrically by dividing the net filter mass gain (W_post − W_pre) by the total volume of air sampled (Q × T), where Q is the mean flow rate (L/min) and T is the sampling duration (minutes). PM2.5 was concurrently assessed using the same pump model at 10 L/min, fitted with a personal environmental monitor (SKC Ltd., UK) containing 37 mm polytetrafluoroethylene (PTFE) filters. Post-sampling, filters underwent identical conditioning, weighing, and TWA calculation protocols. The American Conference of Governmental Industrial Hygienists (ACGIH) in United States recommend a TWA of 3 mg/m³ for respirable dust [10]. Gravimetric analysis of collected dust samples was conducted in-house using standard laboratory procedures.

Respiratory symptoms assessment

Respiratory symptoms were assessed using a modified version of the American Thoracic Society–Division of Lung Diseases (ATS-DLD-78-A) questionnaire, a validated and widely used instrument in occupational respiratory health research [11]. The questionnaire was translated into the local language (Gujarati) and pre-tested for clarity and comprehension without modification of its core symptom items. The adapted version demonstrated good internal consistency (Cronbach’s α = 0.82).

Pulmonary function testing

Spirometry was performed according to ATS-ERS guidelines using a portable, pre-calibrated device (Schiller Spirovit-SP10), with measurements of forced vital capacity (FVC), forced expiratory volume in one second (FEV1), FEV1/FVC ratio, forced expiratory flow (FEF25-75%), and peak expiratory flow (PEF) [12]. At least three acceptable manoeuvres were obtained, and repeatability was confirmed if the two best FEV₁ and FVC values were within 150 ml. The highest values from acceptable and repeatable efforts were used for analysis. Lung function was classified as: Normal (FEV₁/FVC ≥ 70% and FVC ≥ 80%), Obstructive (FEV₁/FVC < 70% and FVC > 80%), Restrictive (FEV₁/FVC ≥ 70% and FVC < 80%), and Combined (FEV₁/FVC < 70% and FVC < 80%).

Personal noise monitoring

Personal noise exposure was measured using calibrated Noise Pro DLX dosimeters (3 M Quest Technologies, USA), following Occupational Safety and Health Administration (OSHA) Permissible Exposure Limit (PEL) settings [13]. An acoustic calibrator (Model AC-300) was used for calibration. The microphone of the noise dosimeter was affixed to the shoulder near the ear of each worker, and exposure was recorded continuously over a full 8-hour work shift. Dosimeter placement was periodically checked to ensure data integrity. Data were downloaded and analysed for TWA, peak levels, and compliance with occupational noise standards. The TWA noise exposure was obtained directly from the dosimeter, which computes TWA internally by integrating noise levels over the sampling duration using standardized algorithms based on predefined instrument settings (e.g., exchange rate, criterion level, and threshold) consistent with OSHA-based measurement protocols; therefore, no separate manual calculation was required. According to OSHA, the permissible exposure limit for occupational noise is a TWA of 90 dBA over 8 h [13]. Prolonged exposure above these limits is associated with an increased risk of noise-induced hearing loss (NIHL), typically bilateral and affecting high-frequency hearing thresholds.

Area noise monitoring and octave band analysis

To assess ambient noise levels and frequency-specific exposure, 1/3 octave band analysis was conducted using a Type 1 integrating Sound Level Meter (Model CEL63X, Casella, UK). The instrument was pre-calibrated with an acoustic calibrator (Model CEL120) and mounted on a tripod stand, carefully positioned away from reflective surfaces to prevent distortion. Measurements were conducted during active hammering, across units handling different bell sizes. Data were analysed according to ISO 1996-2:2017 standards to determine exceedance across frequency bands, particularly at 1k, 2k, 4k, and 8k Hz, which are known to contribute to noise-induced hearing loss [14].

Audiometry

Audiometric tests were conducted in a closed room to ensure minimal ambient noise interference. To ensure acoustic integrity, the sound insulation of the testing room was verified. The transmission loss from the exterior to the interior of the recording room was observed at 27 dB at 1000 Hz, indicating adequate attenuation of ambient noise for reliable audiometric assessment. Pure tone audiometry was conducted using a calibrated GSI 61 clinical audiometer (Grason-Stadler, Littleton, Massachusetts). Earphones were placed on the participants’ ears, and a hand switch was provided for them to record their response on receiving sound signals. The hearing assessment was performed on both ears across frequencies of 0.25, 0.5, 1, 2, 3, 4, 6, and 8 kHz. The assessment commenced with the right ear at 1 kHz starting at an intensity of 30 dB hearing level and progressed to higher frequencies up to 8 kHz. Successively, lower frequencies from 250 to 500 Hz were evaluated. In case of no response at 30 dB, the intensity was increased in 10 dB increments until a response was recorded, after which the descending bracketing technique was employed.

Hearing impairment for normal conversational speech was assessed using the pure tone average (PTA) of the better ear at 0.5, 1, 2, and 4 kHz frequencies. Based on WHO criteria, hearing was classified as normal (< 25 dB), mild (26–40 dB), moderate (41–60 dB), or severe (61–80 dB) [15, 16]. Additionally, PTA for the frequencies 3, 4, and 6 kHz was calculated to evaluate the frequency range most susceptible to noise-induced hearing loss (NIHL).

Thermal microclimate (Heat stress) assessment

Heat Stress was assessed using the QUESTemp°36 Area Heat Stress Monitor (TSI, USA), placed at worker height (0.6 m) near the coal-fired furnace to reflect actual working conditions. The device recorded wet bulb, globe, and dry bulb temperatures, as well as relative humidity, to compute the Wet Bulb Globe Temperature (WBGT) index. According to National Institute of Occupational Safety and Health (NIOSH) USA, continuous work should not exceed WBGT values of 30 °C for light work, 28 °C for moderate work, and 26 °C for heavy work for acclimatised workers [17]. Based on task characteristics and standard occupational workload classifications (NIOSH), the work performed by copper bell makers such as hammering for extended periods and furnace operation for extended periods was considered of heavy intensity [17].

Musculoskeletal symptoms assessment

The Modified Nordic Musculoskeletal Questionnaire (NMQ) was used to identify pain sites and assess severity [18]. Irrelevant items were excluded to suit study objectives. The revised tool showed high reliability (Cronbach’s alpha = 0.885) and strong content validity (CVI = 0.95).

Study variables and measures

Independent variables included sociodemographic characteristics such as age, sex, education level, marital status, and years of residence, as well as occupational factors like type of work performed within the bell making process (e.g., metal tipping, powder coating, furnace operation), years of experience, daily working hours, and use of personal protective equipment.

The dependent (outcome) variables focused on health status and exposure-related measures. Health outcomes included the presence and severity of respiratory symptoms (chronic cough, phlegm, dyspnoea), lung function parameters assessed by spirometry (FVC, FEV1, FEV1/FVC ratio), hearing thresholds measured by audiometry to detect noise-induced hearing loss, and musculoskeletal complaints identified through standardized questionnaires.

Environmental exposure measures included personal and area measurements of noise levels, respirable dust and particulate matter PM2.5, and heat stress assessed by WBGT.

Data management and statistical analysis

Data were checked for completeness and implausible values using range checks and inspection of distributions. Extreme values were cross-verified with field records and retained when considered valid, reflecting real-world variability in occupational exposures. Descriptive statistics were used to summarize sociodemographic, occupational, clinical, and environmental exposure variables. Categorical variables were presented as frequencies and percentages, and continuous variables as means with standard deviations or medians with interquartile ranges, as appropriate. Associations between categorical variables were examined using chi-square tests or Fisher’s exact tests when expected cell counts were small. Prior to examining associations with health outcomes, we assessed the linear relationship between age and duration of occupational exposure and found a strong positive correlation (Pearson’s r = 0.822, p < 0.001, N = 89); therefore, duration of exposure was retained as the primary exposure variable and age was not entered simultaneously to avoid collinearity. Given the limited number of outcome events, we did not fit multivariable regression models and analyses were based on bivariate comparisons. A p-value of < 0.05 was considered statistically significant. All analyses were conducted using SPSS version 26.0 (IBM Corp.). Findings from audiometry, spirometry, personal noise dosimetry, respirable dust and PM2.5 exposure, and WBGT measurements were compared against internationally accepted occupational exposure limits and diagnostic criteria, including those from WHO, ATS/ERS, OSHA, ACGIH, ISO standards and NIOSH.

Results

Participant characteristics

As shown in Table 3, out of the 89 participants, 70.8% were male; mean (± SD) age was 32.6 (± 13.0) years. Most had lived locally for more than 20 years (69.6%) and were currently married (68.5%). Illiteracy was 27%; only 23.6% completed higher secondary education. Median family income was INR 15,000. Tobacco use was high (smoking: 18%, 8.55 pack-years; chewable: 50.6%); none reported alcohol use.

Table 3.

Demographic and occupational characteristics of copper-bell makers (n = 89)

Variables	n (%) or value
Sex
Male	63 (70.8)
Female	26 (29.2)
Age (years)
< 30	46 (51.7)
31–40	22 (24.7)
41–50	12 (13.5)
> 50	9 (10.1)
Mean ± SD	32.6 ± 13.0
Duration of current residence (years)
< 10	7 (7.9)
10–20	20 (22.5)
> 20	62 (69.6)
Mean ± SD	29.72 ± 13.69
Marital status
Never married	26 (29.3)
Currently married	61 (68.5)
Widowed	2 (2.2)
Highest education
Not literate	24 (27.0)
Literate without formal schooling	11 (12.3)
Primary	14 (15.7)
Secondary	19 (21.3)
Higher secondary	21 (23.7)
Tobacco Use
Current smoking	16 (18.0)
Current chewing	45 (50.6)
Nature of work
Bell metal tipping	47 (52.8)
Powder coating	26 (29.2)
Heating in coal-fire furnace	16 (18.0)
Total work hours per day, (mean ± SD)	6.33 ± 2.24
Total work experience (years)
< 5	21 (23.6)
6–10	22 (24.7)
> 10	46 (51.7)
Mean ± SD	14.67 ± 11.13
Having an artisan card
Yes	67 (75.3)
No	22 (24.7)
Use of PPE
No	89 (100.0)

Occupational characteristics

Occupationally, 47 (52.8%) worked in bell tipping, 26 (29.2%) in powder coating, and 16 (18.0%) in coal-fired furnace operations. Mean daily work hours were 6.33 ± 2.24; mean experience was 14.67 ± 11.13 years. Over half had more than ten years’ experience, and 75.3% had an artisan card that provides formal recognition to their craft (Table 3). Observational assessment indicated that workers typically wore routine daily clothing during work activities, without the use of dedicated work attire or task-specific personal protective equipment.

Dust exposure and respiratory health outcomes

Respirable dust concentrations near coal-fired furnaces averaged 4.93 ± 1.36 mg/m³, exceeding the ACGIH threshold of 3 mg/m³ (Table 4). Elevated PM2.5 levels (3.31 ± 1.16 mg/m³) are concerning given their deep lung penetration potential, particularly in poorly ventilated workshops. Spirometry was completed for 73 of 89 participants; exclusions were due to poor effort or contraindications. Of those tested, 83.6% had normal function, while 8.2%, 6.9%, and 1.3% showed obstructive, restrictive, and mixed patterns, respectively (Table 5). This is consistent with the presence of chronic respiratory symptoms – cough (15.7%) and dyspnoea (14.6%) in this population.

Table 4.

Analysis of dust samples at coal-fired furnace workstation (n = 5)

Location	Concentration (mg/m3)
	Respirable Dust*	PM2.5
Coal-fire furnace workstation no. 1 (Semi-Open, Under Shade)	5.90	4.21
Coal-fire furnace workstation no. 2 (Open Bay, Outdoor)	3.29	1.88
Coal-fire furnace workstation no. 3 (Semi-Open, Under Shade)	6.56	4.44
Coal-fire furnace workstation no. 4 (Semi-Open, Outdoor)	4.98	3.71
Coal-fire furnace workstation no. 5 (Semi-Open, Outdoor)	3.89	2.28
Mean ± SD	4.93 ± 1.36	3.31 ± 1.16

*Respiratory dust samples from all five coal-fire furnace workstations exceeded ACGIH threshold of 3 mg/m³. The average measurement time for dust measurements (respirable dust and PM₂.₅) was 294 ± 69 min

Table 5.

Respiratory health assessment among copper bell makers

Respiratory symptoms (n = 89)	n (%)
Cough	14 (15.7%)
Dyspnoea	13 (14.6%)
Dyspnoea grade I	0
Dyspnoea grade II	10
Dyspnoea grade III	02
Dyspnoea grade IV	01
Phlegm	7 (7.9%)
Chest Pain	3 (3.4%)
Lung function diagnosis (n = 73)
Normal	61 (83.6%)
Obstructive	6 (8.2%)
Restrictive	5 (6.9%)
Combined	1 (1.3%)

Noise exposure and hearing loss

Personal noise exposure during hammering in nine workshops (bell sizes 2–10) showed TWA values of 73.3–83.1 dB(A), all below OSHA limits. However, peak levels reached 148.2 dB(C) during metal tipping, posing auditory risk despite acceptable TWA values (Table 6). Octave band analysis in three workshops (bell sizes 6, 9, and 12) showed LAeq 81.6–84.7 dB(A), with LZpk up to 126.1 dB(C) (Table 7). Noise Criterion (NC) limits were exceeded at 4k and 8k Hz across all units; larger bells showed frequency exceedances at 1k and 2k Hz. Noise Ratings (NR) exceeded NR 70 in all units, indicating levels comparable to heavy engineering (ISO 1996-1:2016). Graphic representation for octave band analysis with standard NC and NR curves are given in supplementary Figs. 2–7.

Table 6.

Noise dosimetry at copper bell tipping indoor workshops (n = 9)

Workshop No	Bell size	Lmin dB(A)	Lmax dB(A)	Lpeak dB(C)	TWA dB(A)
1	2	65	110.8	148.2	79.3
2	2	65	115.5	147.3	80.1
3	2	65	112.6	145.6	79.3
4	2	65	112.3	144.9	73.3
5	2	65	119.8	147	81.7
6	4	65	112.9	142.1	80.5
7	5	65	109.1	145.1	76.9
8	6	65	111.1	146.0	77.5
9	10	65	116.6	145.3	83.1

*All samples of personal noise dosimetry were below OSHA thresholds of 90 db(A). The average measurement time for personal noise dosimetry was 462 ± 53 min

Table 7.

Octave band analysis at copper bell tipping indoor workshops (n = 3)

Task/Process	Bell Tipping	Bell Tipping	Bell Tipping
Workshop Location	Indoor Workshop	Indoor Workshop	Indoor Workshop
Workman	2	1	2
	6	9	12
Frequency (Hz)	LAeq dB(A)	LAeq dB(A)	LAeq dB(A)	Noise Criterion Upper Limits dB(A) for selected Frequencies
63	40.3	42.6	40.1	83
125	45	50.9	47.9	79
250	53.8	58.1	53	75
500	59.7	60.6	60.2	72
1k	69	67.9	71.4	71
2k	68.4	73.6*	70.1*	70
4k	70.5*	75.9*	72.8*	69
8k	68.1*	70.4*	70.1*	68
Cumulative
LAeq dB(A)	81.6	83.6	84.7
LAmin dB(A)	65	65	65
LAmax dB(A)	100.2	103.2	98.4
LZpk dB(C)	126.1	125.9	123.4
Noise Rating (NR)	75	80	77

[LAeq dB(A) Equivalent Continuous A-weighted Sound Level in decibels, LAmin dB(A) Minimum A-weighted Sound Level in decibels, Lamax dB(A) Maximum A-weighted Sound Level in decibels, LZpk dB(A) Peak Sound Level in Z-weighted decibels]

*Noise Criterion Exceedances observed in the 2–8 kHz range across all three workshop units indicate predominance of mid–high frequency noise, which is particularly relevant for speech interference and auditory strain which can in turn lead to increased worker fatigue

Audiometry (n = 57) showed 68.4% had > 25 dB(A) hearing loss in the conversational range (PTA 0.5–4 kHz). High-frequency hearing loss (PTA 3–6 kHz), indicative of NIHL, was found in 80.7%, increasing with age and experience (p < 0.05). Powder coating and coal furnace workers had higher NIHL prevalence, likely due to longer exposure (median years: 16 and 18 vs. 10 in tippers) and historical noise exposure among coal furnace workers, many of whom previously performed bell tipping. Powder coaters also work near tipping areas, contributing to cumulative exposure (Table 8).

Table 8.

Prevalence of hearing loss among copper bell makers: distribution by demographic and occupational variables. (n = 57)

Variables	Conversational Hearing Loss (PTA 0.5-1-2-4) n (%)				High Frequency Hearing Loss (PTA 3-4-6), NIHL n (%)
	Normal	Mild	Moderate	p-value	Normal	Mild	Moderate	Severe	p-value
All workers	18 (31.6%)	29 (50.9%)	10 (17.5%)		11 (19.3%)	21 (36.8%)	20 (35.1%)	5 (8.8%)	-
Work Experience in years
≤ 10	10 (45.5%)	9 (40.9%)	3 (13.6%)	0.073	5 (22.7%)	13 (59.1%)	4 (18.2%)	0 (0%)	0.001
11–20	5 (27.8%)	12 (66.7%)	1 (5.6%)		5 (27.8%))	6 (33.3%)	7 (38.9%)	0 (0%)
> 20	3 (17.6%)	8 (47.1%)	6 (35.3%)		1 (5.9%)	2 (11.8%)	9 (52.9%)	5 (24.9%)
Job Profile
Bell Metal Tipping	11 (35.5%)	15 (48.4%)	5 (16.1%)	0.013	7 (22.6%)	15 (48.4%)	6 (19.4%)	3 (9.7%)	0.009
Powder Coating	4 (36.4%)	2 (18.2%)	5 (45.5%)		4 (36.4%)	1 (9.1%)	4 (36.4%)	2 (18.2%)
Coal Fire Furnace	3 (20.0%)	12 (80.0%)	0 (0%)		0 (0%)	5 (33.3%)	10 (66.7%)	0 (0%)

Heat stress

As shown in Table 9, across all three workshops, the mean WBGT values exceeded 30 °C, which is the NIOSH recommended limits for continuous exposure across all workload categories (light: 30 °C, moderate: 28 °C, heavy: 26 °C). The average globe and ambient temperatures and relative humidity indicated significant radiant heat exposure, highlighting a high risk of occupational heat strain. WBGT peaked between 11 AM and 1 PM (35.7 °C), declining to 31.7 °C by 6–8 PM (Supplementary Fig. 1).

Table 9.

Heat stress parameters in coal-fired furnace workstations (n = 3)

Parameters	Coal-fire furnace workstation no. 1 (Semi-Open, Under Shade) Mean ± SD (Range)	Coal-fire furnace workstation no. 2 (Open Bay, Outdoor) Mean ± SD (Range)	Coal-fire furnace workstation no. 3 (Semi-Open, Under Shade) Mean ± SD (Range)
Tw (°C)	29.5 ± 1.1 (27.7–31.0)	29.6 ± 0.6 (28.5–30.7)	28.2 ± 0.7 (27.1–29.5)
Tg (°C)	43.4 ± 4.6 (37.0–49.5)	51.4 ± 5.4 (39.6–57.2)	47.6 ± 3.2 (43.2–53.7)
Ta (°C)	41.8 ± 4.0 (36.1–47.2)	39.1 ± 2.6 (35.2–43.1)	43.0 ± 2.9 (37.7–46.1)
RH (%)	39.5 ± 5.8 (31.0–46.0)	35.8 ± 7.2 (29.0–52.0)	34.0 ± 3.5 (29.0–40. 0)
HI (°C)	53.2 ± 7.4 (43.0–65.0)	45.0 ± 3.5 (39.0–51.0)	51.7 ± 5.0 (43.0–59.0)
WBGT (°C)	33.7 ± 2.2 (30.6–36.2)*	36.2 ± 1.8 (32.0–38.4)*	34.0 ± 1.3 (32.0–36.4)*

[Tw (°C) Wet bulb temperature, Tg (°C) Globe thermometer temperature, Ta (°C) Ambient air temperature/ Dry bulb temperature, RH (%) Relative humidity, HI (°C) Heat Index, WBGT-i (°C) Wet Bulb Globe Temperature (indoor), WBGT-i = 0.7 Tw + 0.3 Tg]

*All samples exceeded NIOSH recommended WBGT limits of heavy work i.e. 26 °C for coal-fire furnace workers

Musculoskeletal disorders

Musculoskeletal pain was reported by 69.7%, most commonly in the lower back (56.2%), upper back (32.6%), and shoulders (22.5%) (Fig. 2). Pain prevalence was higher in powder coating and coal furnace groups.

Fig. 2.

Musculoskeletal pain in copper bell makers (n = 89)

Work-related symptoms

Eye, skin, and kidney symptoms varied by role (Fig. 3). Eye symptoms were most reported in furnace (44%) and coating workers (35%); skin symptoms were more common in tippers (15%). Powder coaters reported the highest prevalence of kidney symptoms (19%).

Fig. 3.

Self-reported symptoms in different work profile of copper bell makers (n = 89)

Discussion

This study provides one of the most comprehensive assessments of occupational exposures and health outcomes among copper bell makers – a metal handicraft industry. The findings reveal a high burden of respiratory, auditory, musculoskeletal, and general health complaints, closely linked to adverse workplace exposures such as noise, heat, dust, and poor ergonomic conditions.

The sociodemographic profile of the study population reflects a vulnerable workforce, with low educational attainment, limited income, and a high prevalence of tobacco use. These factors likely compound the health risks associated with hazardous workplace exposures and limit access to preventive and curative health services. Most artisans had long work tenures, often exceeding a decade, and none reported the use of personal protective equipment.

The mean concentrations of respirable dust (4.93 mg/m³) in the workshops, especially near coal-fired furnaces, exceeded ACGIH threshold limits, indicating substantial risk for respiratory morbidity. Consistent with these exposures, 15.7% of workers reported chronic cough and 14.6% reported dyspnoea, with 8.2% and 6.9% having obstructive and restrictive lung function patterns, respectively. These findings are comparable to those observed among bell metal workers in Odisha and other Indian craft clusters, where chronic exposure to dust and fumes is linked to bronchial irritation, chronic bronchitis, and reduced lung function [19]. Similar studies found that prolonged occupational dust exposure is associated with increased respiratory symptoms and reduced lung function, with risks rising with longer exposure duration and among older workers [20–22]. The lack of ventilation and respiratory protection likely contributes to the observed respiratory impairment, echoing findings from other studies of informal sector workers.

Copper bell makers were found to be exposed to moderate average noise levels (mean TWA: 79.08 ± 2.89 dB(A)), but with frequent and extreme peak exposures during hammering activities (up to 148.2 dB(C)). Octave band analysis revealed that noise levels exceeded NC limits at 4 kHz and 8 kHz in all units, and at 1 kHz and 2 kHz in units working on larger bells. These high-frequency exceedances are particularly concerning, as noise-induced hearing loss (NIHL) typically manifests as a notch at 4 kHz and 6–8 kHz [23–25]. Correspondingly, audiometric assessment showed that 80.7% of workers had high-frequency hearing loss, with severity strongly associated with age and work experience. This is consistent with studies among industrial and handicraft workers, where chronic exposure to impulsive and high-frequency noise is a primary risk factor for NIHL [8, 26–29]. The absence of hearing protection in this population further exacerbates risk, as highlighted in systematic reviews and Cochrane analyses [8, 24], which show that hearing conservation programs and consistent use of earplugs are effective in preventing NIHL.

The mean WBGT of 34.1 °C measured near coal furnaces substantially exceeds NIOSH’s recommended exposure limits for continuous work (26–30 °C depending on workload), suggesting a significant risk of heat stress. Such levels are associated with a high risk of heat strain, dehydration, heat-related illnesses, and reduced work capacity as documented in studies of foundry and metal craft workers in tropical environments [19, 30, 31]. Chronic heat exposure, especially without adequate rest breaks or hydration, can also contribute to renal symptoms [30], which were reported by a notable proportion of workers in this study, though further investigation is warranted. Given that WBGT values peaked at midday but were lower during early morning and late evening, it is advisable for workers to schedule coal furnace operations during cooler hours to reduce heat stress risk, especially since the flexible nature of household industry allows for such adjustments.

As outlined in the task-based hazard assessment (Table 1), workers may be exposed to metal dust, fumes, and coal smoke during various stages of the copper bell making process. While specific metal constituents were not analyzed in this study, these exposures represent potential pathways for both occupational and secondary household exposure. Workers were observed to perform tasks in routine daily clothing without the use of dedicated work attire, raising the possibility of take-home exposure pathways. Simple measures such as changing clothes after work, basic hand hygiene, and regular cleaning of work surfaces and surrounding areas may help reduce this risk.

Musculoskeletal symptoms were reported by nearly 70% of copper bell makers, with lower back, upper back, and shoulder pain being most common. These findings are consistent with studies of handicraft and precision workers, where prolonged static postures, repetitive manual tasks, and inadequate ergonomic support contribute to a high burden of musculoskeletal disorders (MSDs) [32–36]. Risk factors identified in this, and other studies include age, work experience, long work hours, and lack of rest breaks. The higher prevalence of MSDs among powder coating and furnace workers may be due to more demanding physical tasks and awkward working positions.

Based on the study findings, a set of task-specific Standard Operating Procedures (SOPs) was developed by the investigators and shared with the Handicraft Service Centre to support dissemination and adoption among artisan communities. These SOPs provide practical guidance for reducing occupational exposures and improving workplace safety.

Study strengths and limitations

A key strength of this study lies in its methodological rigor and field-based design, being among the first in India to systematically assess multiple occupational exposures and health outcomes in an artisanal craft setting. It employed standardized and validated tools for both environmental monitoring and clinical evaluation, enhancing the reliability and applicability of the findings. By integrating exposure data and specific health effects, the study delivers actionable insights for intervention. The development of task-specific SOPs and periodic medical examination (PME) tools further enhances the translational value of the study.

Despite its strengths, the study has certain limitations. The cross-sectional design limits the ability to establish temporality between exposure and health outcomes. The study was conducted in a limited geographical area, focusing on two villages in Kutch, Gujarat, which may restrict the generalizability of findings to other copper bell-making clusters in India. Additionally, variability in workplace settings and worker practices may have introduced uncontrolled confounding in exposure estimates. The study also did not include analysis of specific metal constituents, limiting the ability to attribute health effects to metal exposures. Nevertheless, these limitations are balanced by the study’s methodological rigor and its contribution to a largely under-researched area.

Policy implications

The study was conducted in response to a priority request by the Development Commissioner (Handicrafts), Ministry of Textiles, and funded by the National Health Mission (NHM) of Gujarat. The SOPs developed by investigators as part of this study offer a practical, evidence-based framework for intervention. These include specific engineering controls such as installation of sound absorbing materials in indoor workshops, use of wet methods and designated coating areas to reduce dust dispersion during powder coating, and heat shielding and improved ventilation around furnace workstations.

Administrative measures include structured work–rest cycles during high heat exposure, periodic maintenance of tools and equipment, and task-specific training programs. Provision and consistent use of appropriate personal protective equipment (e.g., masks, ear protection, gloves) are essential. Ergonomic improvements such as provision of seating with back support and modification of floor-based work practices can help reduce musculoskeletal strain.

Integration of periodic health surveillance through the primary healthcare system, including screening for respiratory, auditory, and musculoskeletal conditions, is recommended. At the primary healthcare level, this integration can be operationalized through training of healthcare providers to identify occupational risk factors, incorporation of basic occupational history in routine consultations, and use of simple screening tools for early detection and referral of work-related conditions. Additionally, culturally tailored worker education and awareness programs can support adoption of safer practices. Adoption of these SOPs by the Development Commissioner (Handicrafts) and NHM, as has already begun, could serve as a scalable model for extending occupational health coverage to similar informal craft sectors across the country.

Practical relevance

This study demonstrates that even in informal, home-based settings, targeted interventions can be designed and implemented. For example, rescheduling heat-intensive tasks such as coal furnace operations to cooler hours of the day can substantially reduce heat exposure with minimal cost. Similarly, simple measures such as positioning workstations to maximize natural ventilation, using cloth barriers or partitions to reduce dust dispersion during powder coating, and regular wet cleaning of work areas can help lower airborne dust levels. Noise exposure during hammering can be mitigated through the use of earplugs tuned to attenuate noise at 4–8 kHz and by introducing task rotation or short rest breaks during extended work hours. Ergonomic improvements, such as provision of low-cost seating with back support or use of raised platforms to reduce prolonged floor sitting, can help reduce musculoskeletal strain.

Health surveillance through periodic spirometry and audiometry, along with basic awareness on hydration, use of protective equipment, and early symptom recognition, can be feasibly integrated through existing primary healthcare systems. Frontline healthcare workers can play a key role by incorporating basic occupational history taking and symptom screening into routine care. Importantly, this study highlights that household-based industries are amenable to structured occupational health improvements without disrupting the artisanal workflow.

Conclusion

This study offers comprehensive insights into the occupational exposures and health outcomes faced by copper bell makers. The findings demonstrate that workers are exposed to excessive heat near coal-fired furnaces, hazardous noise levels – particularly in the high-frequency range consistent with NIHL, and respirable dust exceeding recommended occupational thresholds. There is an urgent need for multi-level interventions such as engineering controls, PPE, ergonomic improvements, health screening, and policy support – to protect the health and livelihoods of these artisans.

For field implementation, the approach used in this study can be operationalized through collaboration with local artisan support systems, such as Handicraft Service Centres and primary healthcare networks, by integrating exposure assessment, simplified health screening, and dissemination of task-specific SOPs. This framework is adaptable and can be replicated in other artisanal sectors with similar informal, home-based work structures by tailoring hazard identification and intervention strategies to specific processes. Further research should explore longitudinal health outcomes and evaluate the effectiveness of preventive strategies across diverse artisanal occupations.

Authors’ contributions

AS, NK, RB and AV conceived and designed the study. All authors contributed to data collection, and manuscript revision. AS, NK, AV and SK performed data analysis and interpretation. AS drafted the manuscript. All authors approved the final version of manuscript.

Funding

State Health System Resource Centre (SHSRC) Gujarat, under the National Health Mission (NHM).

This study was funded by the State Health Systems Resource Centre (SHSRC), Gujarat, under the National Health Mission. The funder had no role in the study design, data collection, analysis, interpretation, or in the writing of the manuscript. The funding supported field implementation and the development of craft-specific occupational health SOPs for submission to relevant authorities. The authors being full time research faculties of the non-profit occupational health research institutes, conducted and reported this study within their independent capacity.

Data availability

The datasets generated are not publicly available due to privacy concerns but are available from the corresponding author upon reasonable request.

Declarations

Ethics approval and consent to participate

The study was approved by the Institutional Human Ethics Committee of ICMR-National Institute of Occupational Health (ICMR-NIOH/EC/2023/2) and conducted in accordance with the Helsinki Declaration. Written informed consent was obtained from all participants, who were assured of confidentiality, anonymity, and their right to withdraw at any time. Participants identified with health problems during clinical assessments were referred to nearby government hospitals for further evaluation and management.

Competing interests

The authors declare no competing interests.