Abstract
Background
Workers in informal grinding industries are frequently exposed to multiple occupational hazards, yet data on their self-reported health effects remain limited. Understanding these perceptions is critical for designing practical preventive interventions in resource-limited settings.
Objective
To determine the prevalence and associated factors of self-reported health effects among commercial grinding workers in Sagamu, Ogun State, Nigeria.
Methods
A cross-sectional study was conducted among 347 randomly selected commercial grinding workers in Sagamu, Nigeria, from January to September 2025. Data were collected using an interviewer-administered questionnaire and analysed using descriptive statistics, chi-square tests, and multivariable logistic regression in SPSS version 25 (p < 0.05). The response rate could not be determined because the number of eligible workers approached was not documented.
Results
Overall, 82.4% of respondents reported health effects, most commonly hearing difficulty (19.9%), respiratory symptoms (16.4%), and musculoskeletal discomfort (16.4%). Longer work experience (AOR = 1.10; 95% CI: 1.03–1.17), longer working hours (AOR = 1.14; 95% CI: 1.02–1.29), and smoking (AOR = 1.62; 95% CI: 1.05–2.56) were associated with higher odds of self-reported health effects, while Personal Protective Equipment (PPE) use was associated with lower odds (AOR = 0.39; 95% CI: 0.21–0.72).
Conclusion
Self-reported health effects were common among grinding workers, particularly hearing, respiratory, and musculoskeletal symptoms. Longer work experience, working hours, smoking, and PPE use were associated with reported health effects. Further studies using objective exposure and clinical assessments are warranted.
Keywords: occupational health, self-reported health effects, grinding industry workers, personal protective equipment, informal sector
Introduction
Work-related health remains a critical but often under-addressed issue in many low- and middle-income countries, especially within informal and small-scale industrial settings. Workers in grinding operations are frequently exposed to a multiplicity of hazards, including physical, chemical, ergonomic, and psychosocial hazards, which may lead to both acute and chronic adverse health outcomes. 1 Yet, equally important is how workers themselves perceive these health risks: their beliefs, experiences, and perceptions shape preventive behaviours, reporting, and uptake of safety measures. 2 Recent evidence highlights the heterogeneous nature of work-related exposures in industrial processing environments. In an Iranian ceramic facility, objective workplace assessments identified respirable dust and noise among the important occupational hazards, with substantial variation in risk across occupational groups, underscoring the need for task- and exposure-specific work-related health assessment. 3
The concept of self-related work health effects refers to the subjective assessment by workers of symptoms, ailments, or bodily changes that they believe are caused or exacerbated by their occupational environment. 4 Such perceptions may encompass respiratory symptoms (e.g. cough, difficulty breathing), ocular irritation, musculoskeletal pain, fatigue, hearing difficulties, or even systemic effects (e.g. headaches, cardiovascular stress). 4
Understanding self-related health effects is important for several reasons. First, self-related health symptoms often precede clinically diagnosed disease and may act as early warning signals.5,6 Second, these perceptions influence workers’ attitudes, hazard‐preventive behaviours, and decisions to seek medical care or modify working conditions. Finally, exploring perceived effects helps bridge the gap between objective measurements (e.g. dust concentration, noise levels) and workers’ lived experiences, thereby informing more responsive work-related health interventions.7-9
In a study of work-related health exposures in African contexts, 14.6% of workers reported eye difficulties, 7.3% nasal irritation, 3.9% difficulty breathing, and 3.4% cough as self-related persistent health issues related to their work environments. 4 In grinding industries, workers are exposed to dust, noise, vibration, and chemicals, all of which have documented associations with respiratory, dermatologic, auditory, and musculoskeletal difficulties.10,11 Recent risk assessments similarly highlight dust, noise, and ergonomic hazards in grinding-related industrial processes.12,13 Poor workplace safety climate and inadequate illumination may further affect workers’ safety and well-being.14,15
In Nigeria, milling and grinding work has been associated with reduced lung function and increased respiratory symptoms.16,17 Sagamu has numerous small-scale grinding enterprises involved in processing grains, spices, and other materials, where workers may experience prolonged exposure to dust, noise, vibration, and repetitive tasks. Despite these work-related health exposures, evidence on self-reported health effects among grinding workers in this setting remains limited.
Few studies have examined how workers perceive the health consequences of these exposures in informal or semi-formal settings. Therefore, this study aimed to determine the prevalence and associated factors of self-reported work-related health effects among commercial grinding workers in Sagamu, Ogun State, Nigeria. The findings may inform work-related health policy and worker education aimed at improving workers’ health in this largely overlooked sector.
Methods
Study Design
A cross-sectional descriptive study design was employed to investigate the self-reported health effects among workers in the commercial grinding industry in Sagamu, Ogun State, Nigeria. This design was appropriate for assessing the prevalence and distribution of self-reported health outcomes and their relationship with sociodemographic and work-related factors at a single point in time. The reporting of this cross-sectional study conforms to the Strengthening the Reporting of Observational Studies in Epidemiology Statement for cross-sectional studies. 18 (Supplementary File 1).
Study Area
The study was conducted in Sagamu, a semi-urban industrial town in Ogun State, Southwestern Nigeria from January 2025 till September 2025. The area is known for its concentration of small-scale grinding enterprises involved in the processing of grains, spices, and metals. These businesses typically operate within open workshops or enclosed stalls with minimal environmental or engineering controls, exposing workers to dust, noise, vibration, and repetitive physical strain. Participant recruitment and questionnaire administration were undertaken during this period.
Study Population and Occupational Characteristics
The study population comprised commercial grinding workers actively engaged in grinding, machine maintenance, loading, or packaging activities within Sagamu. Workers were eligible for inclusion if they had worked in a grinding enterprise for at least six months, were aged 18 years or older, and consented to participate in the study. Workers with pre-existing chronic difficulties unrelated to occupational exposure (e.g., congenital hearing loss or asthma diagnosed before employment) were excluded.
The grinding enterprises in the study area processed a range of materials, including grains, spices, and metals. Given the diversity of materials and work processes, workers were potentially exposed to heterogeneous workplace hazards, which may have included organic and inorganic particulates, noise, vibration, and ergonomic strain.
The work-related characteristics systematically collected at the individual level included years of work experience, average working hours per day, average working days per week, and self-reported Personal Protective Equipment (PPE) use. Detailed individual-level information on the specific material processed, machine type, primary task, degree of workplace enclosure, ventilation characteristics, and engineering control measures was not systematically captured in a form suitable for quantitative analysis. Consequently, these factors were not included as exposure variables in the statistical analyses.
Sample Size Calculation
The sample size was determined using Cochran’s formula for estimating a population proportion. A 95% confidence level (Z = 1.96), an expected prevalence of 71% based on a previous work-related health study,19,20 and a 5% margin of error were used. This yielded a minimum sample size of approximately 316 participants. To account for an anticipated 10% non-response rate, approximately 32 participants were added, giving a final target sample size of 347 workers.
Sampling Technique
The names of registered grinding mills and workshops in the study region were compiled in collaboration with the chairpersons of the relevant associations, forming the sampling frame. All qualified workers within these registered establishments were listed to ensure a comprehensive worker-level frame. A simple random sampling approach was then applied to select respondents. Each eligible worker was assigned a unique identification number, and a random number generator was used to determine the required sample size. This approach was adopted to eliminate selection bias and enhance the generalizability of the findings. The study was conducted using this simple random sampling procedure to obtain valid and unbiased estimates of the knowledge, attitudes, self-reported health effects, and preventive measures related to work-related hazards among workers in the grinding industry.
Participant Recruitment and Response Rate
Eligible workers selected through the sampling procedure were approached and invited to participate after the study procedures had been explained. A total of 347 eligible workers completed the questionnaire and were included in the final analysis. However, the total number of eligible workers initially approached or invited was not documented; therefore, an exact response rate could not be calculated.
Data Collection Instrument
Data were collected using a structured interviewer-administered questionnaire, adapted from validated instruments used in work-related health studies.21,22 It comprised sections on sociodemographic characteristics, knowledge of work-related hazards, attitudes towards work-related health and safety, self-reported health effects, and preventive practices. The interviewer-administered approach was used to accommodate workers with varying literacy levels and facilitate accurate and complete responses.
The questionnaire was developed specifically for this study based on the study objectives and relevant work-related health literature and was not based on a previously validated instrument. Formal psychometric validation and pilot testing were not undertaken prior to its administration.
The self-reported health-effects section assessed self-reported health complaints experienced by the workers, including complaints related to auditory, respiratory, musculoskeletal, dermatological, and headache/dizziness domains. Self-reported health effects were analysed as categorical outcomes rather than as a composite symptom score. No cut-off for “high symptom burden” was applied.
Data Collection Procedure
Trained field assistants, supervised by an occupational health physician, administered the questionnaire in English and Yoruba, depending on participants’ preference. Each interview lasted approximately 20–25 minutes and was conducted on-site during breaks to minimize disruption.
Study Variables and Operational Definitions
The primary outcome was the presence of a self-reported health effect among grinding workers, irrespective of whether the participant attributed the symptom to work-related exposure. Each assessed health symptom was recorded as a binary response (Yes/No). A “Yes” response indicated the presence of the respective self-reported symptom, while a “No” response indicated its absence. Therefore, no Likert-scale transformation, dichotomisation, or frequency-based threshold was applied to the health-symptom variables. Likert-scale responses were used only for the assessment of attitudes towards occupational health and safety and were not used to define the primary health outcome. The assessed health-effect categories included self-reported hearing difficulty, respiratory symptoms, musculoskeletal pain or discomfort, headache or dizziness, and skin irritation or rash. Participants who reported a health effect were classified as having the primary outcome, whereas those who reported none were classified as not having the primary outcome. No composite symptom score or threshold for “high perceived symptom burden” was used in defining the primary outcome.
Perceived occupational attribution was assessed separately using the response categories “Yes,” “No,” and “Not sure.” These categories were retained separately for descriptive analysis. “Not sure” responses were not combined with either “Yes” or “No” and were not used to define the primary outcome.
Explanatory variables included age, sex, educational level, years of work experience, average daily working hours, PPE use, smoking status, and alcohol use. Additional descriptive variables included marital status and average number of working days per week. Age was recorded in completed years. Educational level was categorised as no formal education, primary education, secondary education, and tertiary education. Years of work experience represented the total number of years the participant had worked in grinding-related occupations. It was categorised as <5, 5–10, 11–15, 16–20, and >20 years for descriptive presentation. For the bivariate analysis, years of work experience was categorised as ≤5 years and >5 years, while it was entered as a continuous variable in the multivariable logistic regression model. For the bivariate analysis, average daily working hours was categorised as ≤8 hours/day and >8 hours/day, while it was entered as a continuous variable in the multivariable logistic regression model.
PPE use was defined as self-reported use of any form of PPE during grinding activities (including face masks, gloves, safety goggles, or hearing protection) and categorised as Yes or No based on reported usage. Smoking status was based on self-report and classified as smoker (Yes) or non-smoker (No), while alcohol use was defined as self-reported consumption of alcoholic beverages and classified as Yes or No.
Knowledge of work-related hazards was assessed by assigning one point for each correct response and zero for each incorrect response, producing a total score ranging from 0 to 10. Scores of 0–5 were classified as poor knowledge and scores of 6–10 as good knowledge. Scores below the mean were classified as poor attitude, whereas scores equal to or above the mean were classified as good attitude. Attitude towards occupational health and safety was assessed using Likert-scale items. The overall attitude score was calculated for each participant, and the sample mean score was used as the cut-off point to classify attitude as good or poor.
Data Analysis
Data were entered, cleaned, and analysed using IBM SPSS Statistics version 25. Categorical variables were summarised using frequencies and percentages, while continuous variables were summarised using means and standard deviation as appropriate to their distributions.
Bivariate associations between categorical explanatory variables and the primary outcome were examined using Pearson’s chi-square test, where appropriate. For descriptive and bivariate analyses, years of work experience and average daily working hours were analysed using the predefined categories described in the operational definitions.
Multivariable binary logistic regression was used to examine factors associated with the presence of any self-reported health effect. Although the primary outcome was common, binary logistic regression was retained to examine adjusted associations between participant and occupational characteristics and the odds of reporting the outcome; accordingly, the resulting odds ratios were interpreted strictly as measures of association on the odds scale and not as risk ratios or prevalence ratios. Variables included in the adjusted model were age, sex, educational level, years of work experience, average daily working hours, PPE use, smoking status, and alcohol use, selected a priori based on conceptual relevance and evidence from work-related health literature. Adjusted odds ratios (AORs) with corresponding 95% confidence intervals (CIs) were reported. In the multivariable model, years of work experience and average daily working hours were entered as continuous variables to retain the information contained in their original measurements. Consequently, their AORs represent the change in the odds of reporting a health effect associated with each additional year of work experience and each additional hour worked per day, respectively. Categorical explanatory variables were entered using prespecified reference categories, with absence of the exposure or the lowest applicable exposure category serving as the reference, as appropriate.
Multicollinearity among explanatory variables was assessed using variance inflation factors, with values <5 considered indicative of acceptable collinearity. Model calibration was assessed using the Hosmer–Lemeshow goodness-of-fit test. Missing data were handled using complete-case analysis, with participants with missing values for variables required for a particular analysis excluded from that analysis. All statistical tests were two-sided, and a p-value <0.05 was considered statistically significant.
Ethical Considerations
Ethical approval was obtained from the Health Research Ethics Committee of the University of Port Harcourt (Approval number: UPH/CEREMADE/REC/MM108/083). Participation was voluntary, and written informed consent was obtained from all respondents. Data were anonymized and handled in accordance with the Declaration of Helsinki (2013) on human subjects’ research.
Results
Sociodemographic and Occupational Characteristics of Participants
A total of 347 grinding workers participated in the study (Table 1). The mean age was 41.49 ± 13.6 years, with participants aged >50 years constituting the largest age group (31.4%). Males accounted for 51.6% of participants, and 39.2% had secondary education. The mean duration of work experience was 15.29 ± 8.6 years, with 31.1% having worked for more than 20 years. Most participants (64.3%) reported working 6–10 hours per day. Cigarette smoking and alcohol consumption were reported by 17.9% and 27.1% of participants, respectively. Approximately half (51.0%) reported using PPE during grinding activities. Regarding weekly work duration, 135 (38.9%) worked five days, 89 (25.6%) worked six days, and 123 (35.4%) worked seven days per week.
Table 1.
Sociodemographic, Work-Related and Lifestyle Characteristics of Participants (N = 347)
| Characteristic | Category | n (%) | Characteristic | Category | n (%) |
|---|---|---|---|---|---|
| Age (years) | <20 | 20 (5.8) | Years of work experience | <5 years | 56 (16.1) |
| 21–30 | 66 (19.0) | | 5–10 years | 63 (18.2) | |
| 31–40 | 81 (23.3) | | 11–15 years | 68 (19.6) | |
| 41–50 | 71 (20.5) | | 16–20 years | 52 (15.0) | |
| >50 | 109 (31.4) | | >20 years | 108 (31.1) | |
| Mean ± SD | 41.49 ± 13.6 | | Mean ± SD | 15.29 ± 8.6 | |
| Sex | Male | 179 (51.6) | Working hours/day | <5 hours | 37 (10.7) |
| Female | 168 (48.4) | | 6–10 hours | 223 (64.3) | |
| | | | >10 hours | 87 (25.1) | |
| Marital status | Single | 37 (10.7) | Working days/week | 5 days | 135 (38.9) |
| Married | 116 (33.4) | | 6 days | 89 (25.6) | |
| Divorced | 91 (26.2) | | 7 days | 123 (35.4) | |
| Widowed | 103 (29.7) | | | | |
| Educational level | No formal education | 66 (19.0) | Current cigarette smoking | No | 285 (82.1) |
| Primary education | 108 (31.1) | | Yes | 62 (17.9) | |
| Secondary education | 136 (39.2) | Alcohol consumption | No | 253 (72.9) | |
| Tertiary education | 37 (10.7) | | Yes | 94 (27.1) | |
| PPE considered important | No | 179 (51.6) | PPE use | No | 170 (49.0) |
| Yes | 168 (48.4) | | Yes | 177 (51.0) |
SD, standard deviation; PPE, personal protective equipment.
Prevalence of Self-Reported Health Effects and Perceived Occupational Attribution
A total of 347 commercial grinding workers participated in the study. Table 2 presents the prevalence of self-reported health effects among the respondents. Overall, 286 of 347 participants reported a self-reported health effect, corresponding to a prevalence of 82.4% (95% CI: 78.1%–86.1%). The most frequently reported complaints were self-reported hearing difficulty (19.9%), respiratory symptoms such as cough or shortness of breath (16.4%), and musculoskeletal pain or discomfort (16.4%). Headache or dizziness (15.3%) and skin irritation (14.4%) were also reported. Meanwhile, 61 (17.6%) reported none. However, perceived occupational attribution was assessed separately: 108 participants (31.1%) explicitly attributed their reported health effects to occupational exposure, 108 (31.1%) did not, and 131 (37.8%) were unsure whether their reported health effects were occupationally related.
Table 2.
Distribution of Self-Reported Health Effects Among Commercial Grinding Workers (N = 347)
| Perceived health effect domain | Frequency (n) | Prevalence (%) |
|---|---|---|
| Self-reported hearing difficulty | 69 | 19.9 |
| Respiratory symptoms (e.g., cough, breathlessness) | 57 | 16.4 |
| Musculoskeletal pain/discomfort | 57 | 16.4 |
| Headache or dizziness | 53 | 15.3 |
| Skin irritation or rash | 50 | 14.4 |
| None | 61 | 17.6 |
| Total | 347 | 100.0 |
Legend: Overall, 286 respondents (82.4%) reported a self-reported work-related health effect, while 61 (17.6%) reported none. Among the mutually exclusive health-effect categories recorded, hearing difficulty was the most frequently reported (19.9%), followed by respiratory difficulties and musculoskeletal pain/discomfort (16.4% each), headache or dizziness (15.3%), and skin irritation (14.4%). Each respondent was represented once in the categorical analysis; therefore, frequencies across all categories, including “none,” sum to the total sample (N = 347).
Bivariate Associations
Bivariate analyses (Table 3) showed significant relationships between self-reported health effects and several work-related factors. Workers with more than five years of experience were significantly more likely to report self-reported health effects compared with those with shorter employment duration (p = 0.001). Similarly, respondents who worked more than eight hours per day had higher proportions of self-reported symptoms (p = 0.026).
Table 3.
Bivariate Associations Between Participant Characteristics and Self-Reported Health Effects Among Commercial Grinding Workers
| Variable | χ2 | p-value |
|---|---|---|
| Age | 1.102 | 0.576 |
| Gender | 0.681 | 0.409 |
| Educational level | 2.143 | 0.342 |
| Any PPE use | 9.512 | 0.002* |
| Years of Experience | 11.244 | 0.001* |
| Average working hours/day | 4.951 | 0.026* |
| Smoking | 4.245 | 0.039* |
| Alcohol | 3.838 | 0.051 |
*p-value < 0.05 was statistically significant.
Legend: Pearson’s chi-square test was used to examine bivariate associations between categorical explanatory variables and the presence of any self-reported health effect (p < 0.05). Age, gender, and education were not significantly related to self-reported health outcomes. Alcohol consumption was borderline significant. Cell-level cross-tabulated frequencies were not available for inclusion in the revised table.
In contrast, regular use of PPE was associated with a lower prevalence of self-reported health effects (p = 0.002). Gender (p = 0.317) and education level (p = 0.067) were not statistically significant.
Factors Associated With Self-Reported Health Effects
Multivariable logistic regression analysis (Table 4) identified years of experience, daily working hours, and PPE use as independently associated factors of self-reported health effects. After adjusting for age, gender, and education, each additional year of work experience was associated with higher odds of reporting a self-reported health effect (AOR = 1.10; 95% CI: 1.03–1.17; p = 0.004). Each additional hour worked per day was associated with higher odds of reporting a self-reported health effect (AOR = 1.14; 95% CI: 1.02–1.29; p = 0.027). Conversely, Any PPE use was associated with lower odds of reporting a self-reported health effect (AOR = 0.39; 95% CI: 0.21–0.72; p = 0.003).
Table 4.
Multivariable Logistic Regression of Factors Associated With Any Self-Reported Health Effect
| Variable | AOR | 95% CI | p-value |
|---|---|---|---|
| Age, per year | 1.012 | 0.966–1.051 | 0.612 |
| Years of experience, per year | 1.096 | 1.031–1.166 | 0.004 |
| Working hours/day, per hour | 1.142 | 1.015–1.286 | 0.027 |
| Sex | |||
| Male | Reference | – | – |
| Female | 1.218 | 0.732–2.026 | 0.451 |
| PPE use | |||
| No | Reference | – | – |
| Yes | 0.392 | 0.214–0.718 | 0.003 |
| Smoking | |||
| No | Reference | – | – |
| Yes | 1.621 | 0.882–2.981 | 0.121 |
| Alcohol use | |||
| No | Reference | – | – |
| Yes | 1.284 | 0.712–2.314 | 0.412 |
| Education | 0.934 | 0.701–1.244 | 0.641 |
Note. AOR, adjusted odds ratio; CI, confidence interval; PPE, personal protective equipment; Ref, reference category. Reference categories were male for sex and “No” for PPE use, smoking, and alcohol consumption, based on the comparisons reported in the original analysis. Educational level was represented by a single coefficient in the available regression output; however, the original coding scheme and reference category could not be reliably established and were therefore not retrospectively inferred. For continuous variables, estimates represent the change in odds associated with a one-unit increase (one year for age and work experience and one hour for average daily working hours). Adjusted estimates with 95% CIs are reported as the principal estimates from the prespecified multivariable model. p < 0.05 was considered statistically significant. Model fit was assessed using the Hosmer–Lemeshow goodness-of-fit test.
Age, gender, and education level were not significantly associated with self-reported health effects in the final model. The regression model showed good fit (Hosmer–Lemeshow p = 0.48).
Discussion
The results demonstrate a high burden of self-reported work-related health effects among grinding industry workers in Sagamu. Hearing, respiratory, and musculoskeletal difficulties were most common, and these symptoms were significantly associated with longer work experience, long working hours, and inconsistent use of protective equipment.
A high proportion of participants (82.4%) reported a perceived health effect. Among the mutually exclusive health-effect categories recorded, self-reported hearing difficulty (19.9%), respiratory symptoms (16.4%), and musculoskeletal pain/discomfort (16.4%) were the most frequently reported. These findings should be interpreted as workers’ self-reported health complaints rather than clinically confirmed occupational disorders.
The pattern of self-reported hearing difficulty as a leading complaint is consistent with auditory health concerns reported among workers in other noise-exposed occupational settings. 23 Similarly, a study among grain millers in Benin reported a high prevalence of audiometrically assessed hearing loss (≈87.7%) with minimal PPE use. 24 Although the outcome measures differ, with our study relying on workers’ self-reported hearing difficulty rather than audiometric assessment, both findings highlight auditory health concerns among workers in grinding environments. Work-related noise is a recognised risk factor for hearing impairment, 25 particularly with prolonged exposure to high noise levels. However, workplace noise levels were not objectively measured in the present study; therefore, the reported hearing difficulties cannot be directly attributed to occupational noise exposure.
Respiratory difficulties may be associated with the inhalation of airborne particulates like silica, metal dust, organic dust, or other abrasive respirable particles generated during grinding activities. Perceived respiratory and other health difficulties associated with workplace exposures have also been reported among informal-sector workers in Nigeria.26,27 Similar respiratory symptoms and reduced lung function have been reported among workers in milling and work-related settings.16,17 Our findings are therefore consistent with the existing literature, although the respiratory difficulties reported in the present study were self-reported and were not confirmed by spirometry or clinical assessment.
Musculoskeletal symptoms are also frequently reported in small-scale industrial settings with repetitive or heavy manual tasks. 27 The combination of awkward postures, load handling, and prolonged working hours has been associated with increased musculoskeletal strain affecting the back, shoulders, and limbs. 27 The high prevalence of musculoskeletal disorders has been reported by other Nigerian workers,28,29 and similar findings have also been reported among brewery workers. 30
Our multivariable regression showed that longer years of experience and longer daily working hours were significantly associated with higher odds of self-reported health effects. This was particularly significant for hearing, respiratory, musculoskeletal, and headache/dizziness symptoms.
Any PPE use was associated with lower odds of reported hearing difficulty and skin irritation among workers. This finding is consistent with broader evidence supporting PPE use as an important component of work-related hazard control across industrial settings. 31 The observed association may reflect the potential role of basic protective measures in limiting occupational exposures in informal work settings, although reverse causation and residual confounding cannot be excluded given the cross-sectional design.
The associations of longer work experience and higher daily working hours with greater reporting of perceived health effects may reflect the cumulative influence of prolonged occupational exposures.31,32 Prolonged exposure to dust and repetitive strain with elevated reports of discomfort and fatigue among industrial workers has also been reported in the literature.4,20
Only about one-third of workers attributed their symptoms to work-related exposure, while nearly 38% were uncertain. This uncertainty may reflect limited work-related health awareness, difficulties in distinguishing work-related from non-work-related causes of common symptoms, or the absence of diagnostic confirmation, a pattern also observed among informal-sector workers in sub-Saharan Africa. 4
Informal industries contribute substantially to livelihoods in Nigeria but often operate with limited work-related health regulation and oversight. Strengthening work-related health policies to include informal-sector workers, alongside worker training, workplace inspection, monitoring, and surveillance, may therefore improve work-related health protection in this sector.
The significant association of smoking with both reported hearing difficulty and respiratory symptoms is consistent with previous studies reporting poorer auditory and respiratory outcomes among smokers with work-related exposures. For instance, Pouryaghoub et al. 33 reported an association between smoking and increased hearing impairment risk among noise-exposed workers, with differences according to cumulative smoking exposure. Similarly, Attarchi et al. 34 reported greater hearing impairment among workers exposed to both work-related noise and smoking.33,34
Our findings have several practical implications. Work-related health surveillance and screening should be strengthened in grinding enterprises to facilitate early identification of health complaints. Where feasible, hearing conservation programmes should include workplace noise monitoring, appropriate hearing protection, periodic audiometric assessment, and worker education. 35
Improved dust control and ventilation, appropriate work scheduling, ergonomic interventions, and adequate rest breaks may help reduce work-related exposures and strain. Worker education and appropriate PPE availability and use should also be promoted in informal grinding settings. Given the observed association between PPE use and lower odds of self-reported health effects, interventions to improve appropriate PPE uptake and adherence warrant consideration.
Limitations of the Study
This study has several limitations that should be considered when interpreting the findings. The cross-sectional design limits the ability to infer causality between work-related exposures and self-reported health outcomes; reverse causation or reporting bias cannot be ruled out. The absence of a comparison group of non-grinding workers limits our ability to determine whether the prevalence of self-reported symptoms was higher than that in comparable populations without occupational grinding exposure. Also, the use of self-reported symptoms introduces the potential for recall bias or differential reporting, as respondents may under- or overestimate the severity or work-relatedness of their symptoms. Additionally, the use of a study-specific questionnaire that had not undergone formal psychometric validation or pilot testing may have introduced measurement error and may limit the reliability and comparability of the self-reported findings.
The health outcomes assessed in this study were self-reported symptoms and should not be interpreted as clinically confirmed occupational diseases. No objective clinical or functional assessments, including audiometry or spirometry, were conducted to confirm the reported auditory or respiratory symptoms. Accordingly, the observed associations represent relationships between measured work-related characteristics and self-reported health effects rather than confirmed exposure–disease relationships. An additional limitation relates to the heterogeneity and limited characterisation of work-related exposures. Grinding enterprises in the study setting processed different materials, including grains, spices, and metals, which may involve substantially different exposure profiles. Although duration of employment, daily and weekly working hours, and PPE use were assessed, detailed individual-level information on the specific materials processed, machine types, primary tasks, workplace enclosure, ventilation, and engineering control measures was not systematically quantified.
Furthermore, objective exposure measurements, including workplace noise levels, airborne dust concentrations, particle composition, and vibration measurements, were not undertaken. Consequently, exposure-specific or dose–response relationships could not be evaluated, and residual confounding by differences in work-related exposure profiles cannot be excluded. Residual confounding cannot be excluded because potentially important factors, including objective exposure intensity, workplace ventilation, specific job tasks, socioeconomic factors, pre-existing medical conditions, and environmental or non-work-related exposures, were not measured or adjusted for in the regression models. Finally, given the high prevalence of the primary outcome (82.4%), odds ratios derived from the logistic regression models may be farther from the null than corresponding prevalence ratios and should therefore not be interpreted as risk ratios or prevalence ratios. The regression estimates were retained and interpreted strictly as measures of association on the odds scale. Future studies may consider modified Poisson or log-binomial regression to directly estimate prevalence ratios for common outcomes. Further research should also employ longitudinal designs incorporating appropriate comparison groups, objective health measurements, and comprehensive exposure assessments to more accurately characterise occupational health outcomes among informal-sector workers.
Conclusions
This study found a high prevalence of self-reported health effects among grinding workers in Sagamu, particularly hearing, respiratory, and musculoskeletal difficulties. Longer work experience, longer daily working hours, smoking, and PPE use were associated with self-reported health effects. These findings highlight the importance of strengthened work-related health surveillance, workplace education, appropriate PPE use, and improved workplace safety practices. However, the cross-sectional design and reliance on self-reported outcomes limit causal inference. Further studies incorporating objective exposure assessment and clinical evaluation are needed to better characterise the relationship between workplace exposures and health outcomes among grinding workers.
Supplemental Material
Supplemental Material for Perceived Work-Related Health Effects and Associated Factors Among Grinding Workers in Sagamu, Nigeria: A Cross-Sectional Study by Ayokunle Osonuga, Gloria Chimdinma Okoye, Uthman Okikiola Adebayo, Adewoyin Adejoke Osonuga, Odusoga Adewale Osonuga, Ayotunde Clementina Osonuga, Olalekan John Okesanya, Tolutope Adebimpe Oso, Damilola Akinsulire, Best Ordinioha, Khalifat Boluwatife Obadeyi, Ayantunde Kayode Ayankola, Mohamed Mustaf Ahmed, Oluwatobi Babajide Ayelaagbe, and Afis Akanni Agboola in Environmental Health Insights.
Author Contributions: All authors contributed significantly to the study. AO and GCO conceptualized and designed the study. AAO, OAO and ACO conducted the literature review and data extraction. GCO, AO, DA, and BO led the methodology and drafted the manuscript. UOA, TAO, KBO, AKA, MMA, and OBA supported data verification and synthesis. OJO and UOA provided critical revisions for important intellectual content, while AO and AAA supervised the study. All authors read and approved the final manuscript.
Funding: The authors received no financial support for the research, authorship, and/or publication of this article.
The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Supplemental Material: Supplemental material for this article is available online.
ORCID iDs
Uthman Okikiola Adebayo https://orcid.org/0009-0000-2000-7451
Oluwatobi Babajide Ayelaagbe https://orcid.org/0009-0009-2172-2866
Ethical Considerations
Ethical approval was obtained from the Health Research Ethics Committee of the University of Port Harcourt (Approval number: UPH/CEREMADE/REC/MM108/083). Data were anonymized and handled in accordance with the Declaration of Helsinki (2013) on human subjects’ research.
Consent to Participate
Participation was voluntary, and written informed consent was obtained from all respondents.
Consent for Publication
This study did not collect identifiable personal data, and all analyses were conducted on fully anonymized datasets.
Data Availability Statement
The datasets used and analyzed during the current study are available from the corresponding author on reasonable request.*
References
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Supplemental Material for Perceived Work-Related Health Effects and Associated Factors Among Grinding Workers in Sagamu, Nigeria: A Cross-Sectional Study by Ayokunle Osonuga, Gloria Chimdinma Okoye, Uthman Okikiola Adebayo, Adewoyin Adejoke Osonuga, Odusoga Adewale Osonuga, Ayotunde Clementina Osonuga, Olalekan John Okesanya, Tolutope Adebimpe Oso, Damilola Akinsulire, Best Ordinioha, Khalifat Boluwatife Obadeyi, Ayantunde Kayode Ayankola, Mohamed Mustaf Ahmed, Oluwatobi Babajide Ayelaagbe, and Afis Akanni Agboola in Environmental Health Insights.
Data Availability Statement
The datasets used and analyzed during the current study are available from the corresponding author on reasonable request.*