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. 2023 Jul 21;18(7):e0284551. doi: 10.1371/journal.pone.0284551

Occupational exposure to dust and respiratory symptoms among Ethiopian factory workers: A systematic review and meta-analysis

Zemachu Ashuro 1,*, Habtamu Endashaw Hareru 1, Negasa Eshete Soboksa 1, Samson Wakuma Abaya 2, Yifokire Tefera Zele 2
Editor: Sebastien Kenmoe3
PMCID: PMC10361507  PMID: 37478114

Abstract

Background

Occupational respiratory disorders are a major global public health concern among workers exposed to dust particles in dust-generating workplaces. Despite fragmented research findings on the magnitude of respiratory problems and the lack of a national occupational respiratory disease recording and reporting system at the Ethiopian factory, the prevalence of respiratory symptoms among factory workers were unknown. Therefore, the aim of this meta-analysis was to summarize and pool estimates from studies that reported the prevalence of respiratory symptoms and predictors among Ethiopian factory workers who worked in dusty environments.

Methods

A systematic literature searches were conducted using electronic databases (PubMed, Science Direct, African Journals Online, and Web of Science). The primary and secondary outcomes were prevalence of respiratory symptoms and predictors, respectively. The STATA version 17 was used to analyze the data. A random effect meta-analysis model was used. Eggers test with p-value less than 5%, as well as the funnel plot, were used to assess publication bias.

Results

The searches yielded 1596 articles, 15 of which were included in the systematic review and meta-analysis. The pooled prevalence of respiratory symptoms among Ethiopian factory workers was 54.96% [95% confidence interval (CI):49.33–60.59%]. Lack of occupational health and safety (OSH) training [Odds Ratio (OR) = 2.34, 95%CI:1.56–3.52], work experience of over 5 years [OR = 3.19, 95%CI: 1.33–7.65], not using personal protective equipment (PPE) [OR = 1.76, 95%CI:1.30–2.39], and working more than eight hours per day [OR = 1.89, 95%CI:1.16–3.05] were all significant predictors of respiratory symptoms.

Conclusion

The prevalence of respiratory symptom was found to be high in Ethiopian factory workers. To prevent workers from being exposed to dust, regular provision and monitoring of PPE use, workers OSH training, and adequate ventilation in the workplace should be implemented.

Introduction

According to a 2017 global estimate, 2.78 million workers die each year as a result of occupational accidents and diseases, with 2.4 million of these deaths being disease-related. It is estimated that lost work days account for nearly 4% of global Gross domestic product (GDP), with some countries accounting for 6% or more [1]. Occupational respiratory disorders are a serious global public health problem, accounting for up to 30% of all documented work-related deaths and having a 50% prevalence among employees in high-risk sectors such as mining, construction, and dust-generating works [2].

Dust is defined as small, dry, solid particles that are emitted into the atmosphere by natural forces such as wind and volcanic eruptions, as well as mechanical or man-made processes such as crushing, grinding, milling, drilling, demolition, shoveling, conveying, screening, bagging, and sweeping. Dust particles typically range in size from 1 to 100 micrometer in diameter and settle slowly under the influence of gravity [3].

Organic dusts are dusts derived from microorganisms (bacteria, fungi, viruses, and protozoa) and their metabolites (mycotoxins, peptidoglycans, endotoxins, glucans, enzymes, and so on), animal origin, and plant (vegetable) origin (flour, wood, cotton and tea dusts, pollens vegetable fibers, and epidermis) [4, 5]. The presence of pollutants (bacteria, molds, dust, and pollen) in the workplace pollutes the indoor air quality. Dust exposure in the workplace can have a negative impact on the respiratory health of industrial workers as well as the productivity of industry sectors [6].

A systematic review conducted in Ethiopia revealed that workers’ exposure to dust in textile and cement factories far exceeded the international permissible limits [7]. Inhaling dust causes inflammatory reactions in the respiratory system [8, 9]. In developed, low- and middle-income countries, where industry sectors are expanding, respiratory health problems are becoming more common, as are poor occupational health and safety practices by both employees and employers [10].

Lack of trained occupational health professionals, insufficient or nonexistent health legislation and basic services, as well as weak industrial infrastructure and controls, were the major challenges for occupational respiratory disease surveillance, reporting, and recording in low- and middle-income countries [11]. The magnitude of reported respiratory symptoms varies from country to country and factory to factory. The prevalence of occupational respiratory symptoms among cement factory workers in India was 54.4% [12] and 21.1% in Udayapur cement factory workers in Eastern Nepal [13]. According to findings from flour mill factories, the prevalence of respiratory symptoms among factory workers 22% in the United Kingdom [14], 28% in Iran [15], 45% in Nigeria [16] and 90% in Egypt [17]. The prevalence of respiratory symptoms among textile factory workers was 62% in Nigeria [18], 59% in Egypt [19], 53% in Bangladesh [20], and 26% in Iran [21].

Another study of wood workers found that the prevalence of respiratory symptoms was 29.9% in the North East of Thailand [22] and 68% in South-South Nigeria [23]. Furthermore, 61.54% of paper factory workers in Sweden experienced respiratory symptoms [24]. In Ethiopia, the lowest prevalence of respiratory symptoms was reported among textile factory workers (36.8%) [25], while the highest was reported among wood factory workers (69.8%) [26]. However, due to the fragmented findings of primary studies and the lack of a national occupational disease recording and reporting system, estimating the magnitude of respiratory symptoms and risk factors among factory workers at the national level is difficult. Therefore, the objective of this systematic review and meta-analysis was to estimate the national pooled prevalence of respiratory symptoms and risk factors among Ethiopian factory workers. This systematic review and meta-analysis findings will help in the development of appropriate occupational safety and health policies and programs to prevent occupational respiratory disease by implementing appropriate dust exposure prevention and control measures in factories.

Methods

Reporting and protocol registration

This systematic review and meta-analysis, which is available at: https://www.crd.york.ac.uk/prospero/displayrecord.php?ID=CRD42022363183, was conducted in accordance with the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis statement) guidelines to estimate the pooled prevalence of respiratory symptoms and associated factors among factory or industry workers [27, 28].

Literature search strategy

We conducted a systematic search of various electronic databases, including PubMed, Science Direct, African Journals Online and Web of science, to estimate the pooled prevalence of respiratory symptoms and associated factors among Ethiopian factory workers. In addition, we searched the Ethiopian University electronic library for unpublished studies. The search was restricted to human studies conducted between 2014 and 2022, as well as full English version articles. We used Boolean operators "AND" and "OR.". The search was conducted independently by two authors (ZA and HEH) using the (MeSH) terms and Text Word (S1 Table). We also looked up "grey literature" on Google Scholar (references not found in PubMed, Science Direct, African Journals Online, or Web of Science). In addition, we searched Ethiopian university databases for unpublished studies. Furthermore, when an article lacked sufficient data, corresponding authors of the research article were contacted via email.

Eligibility criteria

Inclusion criteria

Study settings. Only studies conducted among Ethiopian factory workers.

Publication condition. Both published and unpublished articles were included.

Study design. All observational study designs (cross-sectional, case control and cohort) reporting the prevalence of the respiratory symptoms and its associated factors were eligible for this systematic review and meta-analysis.

Language. Only studies published in the English language were considered.

Population. Participants /workers/ whose age was 18 and greater.

Outcome. Studies reported the odds of respiratory symptoms and associated factors related to dust exposure with corresponding 95% confidence interval.

Publication year. Articles that were conducted between 2014 and 2022 were included in this systematic review and meta-analysis to generate more recent information that will be helpful for policymakers.

Exclusion criteria

Studies that did not show clear data regarding the respiratory symptoms, abstract without full-text, qualitative studies, editorials, and commentaries were excluded from this systematic review and meta-analysis.

Data screening and extraction

The studies that met the inclusion criteria were reviewed. To evaluate the identified studies, we used a two-level screening approach. To begin, titles and abstracts were reviewed for eligibility. This was done independently by ZA and HEH. Second, the full articles were assessed. Before starting the data extraction, the extraction format was prepared in Microsoft Excel Spreadsheet. The author’s name, year of publication, type of factory, region, study design, sample size, response rate, and prevalence of respiratory symptoms for primary outcome (magnitude of respiratory symptoms) were all included in the data extraction format. A two-by-two table was used to extract data from included studies for the second outcome (predictors of the respiratory symptoms). Studies that met the inclusion criteria were screened and extracted by ZA and HEH using a standardized data extraction format, and any disagreements were resolved through discussion with the other investigators (NES, SWA and YTZ).

Outcome measurement

Respiratory symptoms are defined as experiencing one or more of the following symptoms as a result of occupational exposure: cough, phlegm, wheezing, dyspnea, bronchitis, shortness of breath, and chest pain [29–31]. The pooled prevalence of respiratory symptoms was calculated by dividing the total number of workers with respiratory symptoms by the total number of workers in the study and multiplying the result by 100. The factors associated with respiratory symptoms were measured using the odds ratio. We used two-by-two tables to calculate the odds ratio from primary studies.

Quality assessment

The Newcastle-Ottawa quality assessment scale was used to evaluate the quality of the included primary studies. This tool has three domains: selection (a maximum of 5 stars), comparability (a maximum of 2 stars), and outcome (a maximum of 3 stars). The studies score ranges from 0–10 for each study. A study can receive a maximum of 10 stars, indicating the highest level of quality [32]. All included studies were evaluated independently by the authors.

Statistical analysis

To analyze the retrieved data, Stata Corporation, College Station, TX: StataCorp LLC, software version 17.0 was used. The I2 test was used to determine the heterogeneity within the primary studies that were included. We used a random effect model to estimate the pooled prevalence of respiratory symptoms among factory workers because there was significant heterogeneity among included studies. A subgroup analysis was performed by region and factory type to reduce the random variations between the primary study’s point estimates. Sensitivity analysis was performed to determine the effect of a single study on the pooled estimate of outcome. Eggers test with p-value less than 5%, as well as the funnel plot, were used to assess publication bias. The pooled point prevalence with 95%Cl was presented using a forest plot. A meta-regression analysis was carried out to identify potential contributors to the between-study heterogeneity. Univariable analysis was performed on variables such as sample size, factory type, and study settings (region). We used p-values less than 0.25 in univariable meta-regression analysis to declare statistically significantly associated variables.

Results

Search results

We found 1596 articles in the databases PubMed, Science Direct, Google Scholar, African Journals Online, and Web of Science. However, for various reasons, only 15 articles reporting the prevalence of respiratory symptoms and associated factors among factory workers were included in the final systemic review and meta-analysis procedure (Fig 1).

Fig 1. Flow diagram of articles search and selection criteria.

Fig 1

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Descriptive results of eligible studies

This systematic review and meta-analysis included 15 primary studies conducted in Ethiopia and published between 2014 and 2022, with a total of 4129 study participants. The majority of the included studies were conducted in Addis Abeba (n = 5) [26, 33–36] and Amhara Region (n = 5) [25, 37–40], with two studies conducted in Southern Nations, Nationalities and Peoples Region (SNNPR) [41, 42]. All included studies in this systematic review and meta-analysis were cross-sectional studies conducted among Ethiopian factory/industry workers, with the smallest sample size of 51 reported from a study conducted in SNNPR in a textile factory [41] and the largest sample size of 496 reported from a study conducted in Addis Ababa among wood factory workers [26]. The prevalence of respiratory symptoms reported from the primary studies ranged from 27.7% among flour mill factory workers [34] to 69.8% among wood factory workers [26]. The included studies’ quality scores range from 7 to 10 (Table 1).

Table 1. Summary characteristics of the included studies to estimate the prevalence and associated factors of respiratory symptoms in Ethiopia, 2014–2022 (n = 15).

Author Year Region Sample size Type of factory Study design Response rate (%) NOQS
Alemseged et al. [33] 2020 Addis Ababa 415 Flour Cross-sectional 97.9 10
Demeke and Haile [34] 2018 Addis Ababa 54 Flour Cross-sectional 100 7
Mekonnen et al. [37] 2021 Amhara 280 Flour Cross-sectional 100 9
Lagiso et al. [42] 2020 SNNPR 196 Flour Cross-sectional 93.3 8
Kanko et al. [41] 2017 SNNPR 51 Textile Cross-sectional 99.7 7
Zele et al. [38] 2020 Amhara 303 Textile Cross-sectional 100 10
Daba Wami et al. [39] 2018 Amhara 270 Textile Cross-sectional 99 8
Reta Demissie [43] 2019 Oromia 70 Wood Cross-sectional 97.8 7
Jabur et al. [36] 2022 Addis Abeba 230 Wood Cross-sectional 100 8
Awoke et al. [26] 2021 Addis Abeba 496 Wood Cross-sectional 99.1 10
Meskele et al. [35] Unpublished Addis Abeba 206 Paper Cross-sectional 98 7
Kifle et al. [25] 2020 Amhara 383 Cement Cross-sectional 91.7 9
Gizaw et al. [40] 2016 Amhara 404 Cement Cross-sectional 100 10
Siyoum et al. [44] 2014 Oromia 266 Cement Cross-sectional 97.8 8
Mekasha et al. [45] 2018 Oromia 309 Cement Cross-sectional 97 8
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NOQS: Newcastle Ottawa Quality Score, SNNP: Southern Nations, Nationalities, and Peoples.

Meta-analysis

In this meta-analysis, individual study prevalence estimates range from 27.70% to 69.80%, with an overall pooled prevalence of 54.96% (95% CI: 49.33–60.59%; I2 = 92.4%, p<0.000) and individual study weights ranging from 5.59% to 7.19% (Fig 2).

Fig 2. Estimates of the prevalence of respiratory symptoms in Ethiopian factory workers using a forest plot.

Fig 2

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Subgroup analysis

Subgroup analysis was carried out for both region and factory type. The sub-group analysis revealed that the SNNPR had the highest prevalence of respiratory symptoms, with a prevalence of 58.65% (95% CI: 51.75, 65.57%), and the Amhara region had the lowest prevalence, with a prevalence of 53.07% (95% CI: 42.62, 63.52%) (Fig 3).

Fig 3. Forest plot on respiratory symptoms prevalence estimates subgroup analysis by region.

Fig 3

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The other subgroup analysis was done for the type of factory involved. The highest prevalence of respiratory symptoms was reported among wood factory workers (60.28% (95% CI: 48.04, 72.51%), and the lowest prevalence was reported among textile factory workers (49.78% (95% CI: 39.56, 59.99%) (Fig 4).

Fig 4. Subgroup analysis by factory type using a forest plot to estimate the prevalence of respiratory symptoms.

Fig 4

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Publication bias and small study effect assessment

We used Egger’s test and a funnel plot to assess publication bias. The analysis revealed a symmetrical funnel plot indicating no publication bias (Fig 5), and Egger’s test for small-study effect revealed no small-study effects with a p-value of 0.214 (Table 2). We did not perform trim and fill analysis because there is no publication bias.

Fig 5. Funnel plot that assesses publication bias.

Fig 5

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Table 2. Eggers test for publication bias assessment.
Standard Effect Coefficient t-value p-value 95% CI
Slope 69.17 7.16 0.000 48.31–90.03
Bias -4.22 -1.31 0.214 -11.20–2.75
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Sensitivity analysis

According to the results of the sensitivity analysis, individual studies had no significant impact on the overall pooled prevalence of respiratory symptoms among factory workers (Fig 6).

Fig 6. Sensitivity analysis of included studies.

Fig 6

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Meta-regression

Meta-regression analysis was performed on the variables included, which were sample size, factory type, and study settings (region). We used p-values less than 0.25 in univariable meta-regression analysis to declare statistically significantly associated variables. However, in this study, all variables were not significantly associated with the prevalence of respiratory symptoms in the univariable meta-regression analysis (Table 3).

Table 3. Univariable meta-regression model.

Variables Coefficient P-value 95% CI
Type of factory
 Cement 0.08 0.843 -0.555–1.216
  Flour mill 0.33 0.464 -0795-0.938
 Textile 0.07 0.872 -0.964–0767
 Wood 0.36 0.425 -0.530–1.259
 Paper Reference
Constant 0.08 0.843 -0.693–0.848
Study settings (region)
 Addis Ababa -0.16 0.698 -0.959–0.642
 Amhara -0.29 0.473 -1.085–0.503
 Oromia -027 0.544 1.138–0.600
 SNNPR Reference
Constant 0.41 0.236 -0.271–1.099
Sample size
 <262 Reference
 ≥262 0.05 0.832 -0.419–0.520
Constant 0.18 0.322 -0.175–0.532
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Factors associated with the occurrence of respiratory symptoms

From the primary studies, we identified a number of factors associated with respiratory symptoms. This meta-analysis included variables found to have a significant association with respiratory symptoms in at least four primary studies. In this systematic review and meta-analysis, occupational safety and health (OSH) training (OR = 2.34, 95%CI: 1.56–3.52), work experience (OR = 3.19, 95%CI: 1.33–7.65), PPE use (OR = 1.76, 95%CI: 1.30–2.39), and working hours (OR = 1.89, 95%CI: 1.16–3.05) were significant predictors of respiratory symptoms among Ethiopian factory workers.

Association between OSH training and respiratory symptoms

In this meta-analysis, we included seven studies [25, 26, 35, 37, 40, 44] to investigate the relationship between workers’ OSH training and respiratory symptoms. According to the findings of these seven studies, workers who did not receive OSH training were 2.34 times more likely to develop respiratory symptoms than workers who did receive OSH training [OR = 2.34, 95%CI: 1.56–3.52) (Fig 7).

Fig 7. Association of OSH training with respiratory symptoms among factory workers in Ethiopia, 2014–2022.

Fig 7

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Association between work experiences and respiratory symptoms among Ethiopian factory workers

We included six primary studies [26, 36, 37, 39, 40, 42, 44] conducted in Ethiopian factory workers to investigate the association between factory workers’ work experiences and the occurrence of respiratory symptoms. The results of a meta-analysis of six studies revealed that the odds of respiratory symptoms were 3.19 times higher among workers with work experiences greater than five years (>5 years) than among workers with work experiences less than or equal to five years (OR = 3.19, 95%CI: 1.33–7.65) (Fig 8).

Fig 8. Association of [40] work experiences with respiratory symptoms among factory workers in Ethiopia, 2014–2022.

Fig 8

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Association between gender and occurrence of respiratory symptoms

Eight studies were used to determine the association between study participants’ gender and the occurrence of respiratory symptoms among factory workers [25, 35–37, 39, 42, 44]. A meta-analysis of the findings of the eight included studies revealed that there was no statistically significant association between gender and respiratory symptoms among Ethiopian factory workers (OR = 1.25, 95%CI: 0.83–1.89) (Fig 9).

Fig 9. Association of gender with respiratory symptoms among factory workers in Ethiopia, 2014–2022.

Fig 9

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Association between PPE use and occurrence of respiratory symptoms

We investigated five primary studies conducted among factory workers in different Ethiopian factories [25, 33, 35, 39]. The findings of this meta-analysis revealed that workers who did not use PPE in the workplace were 1.76 times more likely to develop respiratory symptoms than those who did (OR = 1.76, 95%CI: 1.30–2.39) (Fig 10).

Fig 10. Association of PPE use with respiratory symptoms among factory workers in Ethiopia, 2014–2022.

Fig 10

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Association between working hours and the occurrence of respiratory symptoms

In this meta-analysis, we included four primary studies conducted in different Ethiopian factories [26, 35, 37, 42, 44]. According to the meta-analysis findings, workers who worked more than 8 hours per day in the factory were 1.89 times more likely to develop respiratory symptoms than those who worked 8 hours or less in the factory (OR = 1.89, 95%CI: 1.16–3.05) (Fig 11).

Fig 11. Association of working hours with respiratory symptoms among factory workers in Ethiopia, 2014–2022.

Fig 11

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Association between biofuel use and respiratory symptoms among Ethiopian factory workers

Four studies were included in the meta-analysis to investigate the association between biofuel use and respiratory symptoms among factory workers [25, 26, 35, 44]. According to the findings of this meta-analysis, the use of bio-fuel for cooking at home was not significantly associated with the occurrence of respiratory symptoms among Ethiopian factory workers (OR = 1.65, 95%CI: 0.72–3.79) (Fig 12).

Fig 12. Association of biofuel used with respiratory symptoms among factory workers in Ethiopia, 2014–2022.

Fig 12

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Association between educational status and respiratory symptoms among Ethiopian factory workers

We used six primary studies to explore the association between workers’ educational status and respiratory symptoms among Ethiopian factory workers [35, 36, 39, 40, 42, 44]. According to a meta-analysis of six primary studies, workers’ educational status was not significantly associated with the occurrence of respiratory symptoms among Ethiopian factory workers (OR = 1.18, 95%CI: 0.41–3.37) (Fig 13).

Fig 13. Association of educational status with respiratory symptoms among factory workers in Ethiopia, 2014–2022.

Fig 13

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Discussion

Occupational respiratory disorders are a major global public health concern among factory workers. This systematic review and meta-analysis finding showed that the pooled estimate of respiratory symptoms among factory workers in Ethiopia was 54.96% (95% CI: 49.33–60.59%; I2 = 92.4%, p<0.000). Lack of occupational health and safety training, work experience of over 5 years, not using personal protective equipment, and working more than eight hours per day were all predictors of high prevalence of respiratory symptoms.

The overall estimate of respiratory symptoms among factory workers in Ethiopia is high. The finding of this study was consistent with studies conducted among cement factory workers in India (54.4%) [12], textile factory workers in Bangladesh (53%) [20], and wood workers in Cameroon (51%) [46]. However, the finding of this study was higher than the findings of studies conducted among cement factory workers in eastern Nepal (21.1%), flour mill factory workers in the United Kingdom (22%) [14], Iran (28%) [15], and Nigeria (45%) [16], textile factory workers in Iran (26%) [21], and a study conducted among wood workers in Thailand’s North East (29.9%) [22], whereas the result of this study was lower than those of studies conducted among Egyptian factory workers in flour mills (90%) [17], Nigerian factory workers in textiles (62%) [18], study conducted among South-South Nigerian wood factory workers (68%) [23], and in Sweden, paper factory (61.54%) [24]. Differences in the work environment, the type of factory, and occupational health and safety practices could all be contributing factors to the discrepancy.

The pooled prevalence of respiratory symptoms was higher among wood factory workers 60.28% (95%CI: 48.04, 72.51%) than among textile factory workers 49.7% (95% CI: 39.56, 59.99%), according to a subgroup analysis of studies by factory type. Workers who did not receive OSH training were 2.34 times more likely to develop respiratory symptoms than workers who did receive OSH training. This study finding was supported by studies conducted in Egypt [47] and Norway [48]. The possible explanation could be that training may provide workers with awareness of how to protect themselves from work-related hazards exposure in the workplace, as well as behavioral change in workers toward occupational safety and health practices.

The result of this study revealed that the odds of respiratory symptoms were 3.19 times higher among workers with work experiences greater than five years (>5 years) than among workers with work experiences less than or equal to five years. This study finding was supported with study conducted in Eastern Nepal [13] and in Egypt [17]. The high prevalence of respiratory symptoms could be attributed to increased dust accumulation in the respiratory system as a result of long-term exposure to dust in the workplace.

According to the systematic review and meta-analysis finding, workers who worked more than 8 hours per day in the dust environment of a factory were 1.89 times more likely to develop respiratory symptoms than those who worked 8 hours or less in the dust environment of a factory. This finding was in line with the study conducted in Thailand, Bangkok among garment workers [49]. The possible explanation is that workers who work in dusty environments for extended periods of time without wearing PPE increase their risk of exposure in the workplace.

According to the finding of this systematic review and meta-analysis, workers who did not use PPE in the workplace were 1.76 times more likely to develop respiratory symptoms than workers who did. This study finding were supported with those of studies conducted in Dhaka, Bangladesh [50], the United Arab Emirates cement factory [51], and the furniture industry workers in Indonesia [52]. The possible explanations for the high prevalence of respiratory symptoms might be workers exposed to different dust particles at work environment due to the lack of PPE in work environment increases workers exposure. This systematic review and meta-analysis is timely and will help to improve occupational safety and health practices, as well as promote and maintain worker health in industry. Because low-income countries have a low level of a national occupational disease recording and reporting system, estimating the magnitude of the problem is difficult. However, this result may help policymakers implement appropriate occupational safety and health interventions. The limitations of this systematic review and meta-analysis were that there was a high degree of heterogeneity among the included studies (I2 statistic = 92.4%, p<0.000) and that only studies published in English were included, which may not have traced all studies. Furthermore, the studies included in this systematic review and meta-analysis were from only four regions, which do not adequately represent the rest of the country, and some studies had small sample sizes, which may have an effect on the pooled estimate of respiratory symptoms.

Conclusions

This meta-analysis and systematic review revealed a high prevalence of respiratory symptoms among factory workers. Lack of occupational health and safety training, work experience of over 5 years, not using personal protective equipment, and working more than eight hours per day were all predictors of high prevalence of respiratory symptoms. Therefore, regular provision and monitoring of personal protective equipment use, provision of occupational safety and health training for workers, and provision of adequate ventilation in the workplace should be implemented to prevent workers’ exposure to dust. The included studies in this systematic review and meta-analysis were cross-sectional studies that did not show a causal relationship between dust exposure and respiratory effects. To plan an effective control strategy, studies on factory workers should be conducted using a prospective cohort study design. Furthermore, the Federal Ministry of Labor and Social Affairs of Ethiopia, the Federal Ministry of Health of Ethiopia, and other stakeholders should work together to improve occupational health and safety practices at the factory level.

Supporting information

S1 Table. Summary of search results from PubMed, Google Scholar, Science Direct, African Journals Online, and Web of Science databases.

(DOCX)

Click here for additional data file. (3.3MB, docx)
S2 Table. The PRISMA 2020 checklist (Preferred reporting items for systematic review and meta-analysis) is an updated guideline for reporting systematic reviews.

(DOCX)

Click here for additional data file. (31.5KB, docx)

Acknowledgments

We thank the original study’s authors and participants for their contributions to this systematic review and meta-analysis.

Abbreviations

AOR

Adjusted odds ratio

CI

Confidence interval

GDP

Gross domestic product

NOQS

Newcastle Ottawa Quality Score

OSH

Occupational Safety and Health

PPE

Personal Protective Equipment

PRISMA

Preferred Reporting Items for Systematic Reviews and Meta-Analyses

SNNPR

Southern Nations, Nationalities and Peoples Region

Data Availability

All relevant data are within the paper and its Supporting information files.

Funding Statement

The authors received no specific funding for this work.

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Decision Letter 0

Ghulam Md Ashraf

14 Feb 2023

PONE-D-22-30181Occupational exposure to dust and Respiratory symptoms among Ethiopian factory workers: a systematic review and meta-analysisPLOS ONE

Dear Dr. Ashuro,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

Please submit your revised manuscript by Mar 31 2023 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

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We look forward to receiving your revised manuscript.

Kind regards,

Ghulam Md Ashraf, Ph.D.

Academic Editor

PLOS ONE

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: No

**********

2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: I Don't Know

Reviewer #2: No

**********

3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: No

**********

4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: No

**********

5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: This manuscript performed a systematic review and meta-analysis to estimate prevalence of respiratory symptoms associated with occupational exposure of dust among Ethiopian factory workers. This study is specifically important as it estimates the overall prevalence of respiratory symptoms among workers in different industries whereas the previous studies were confined to specific industries. However, the authors are requested to address the following comments:

1. Paragraph 6 in the introduction section “The prevalence of occupational…….to 69.8% wood factory workers” has some overlapping/repetitive information with paragraph 2 in the discussion section “According to the findings…………contributing factors to the discrepency.” Either paragraph can be rephrased to avoid it.

2. Paragraph 7 in the introdcution section starts with “However, the research findings are inconsitent.” Which research findings are inconsistent and why do the authors think so?

3. In the last paragraph of introduction section, the authors should focus and elaborate on the scope of this manuscript compared to previous studies i.e. pooled estimates of prevalence in different industries vs. industry specific prevalence in previous studies.

4. Research question should be within the text in the introduction section.

5. It is better to put table 1 in the supplementary information.

6. It is better to discuss the limitations in the discussion section rather than having a separate section.

7. Please revise the manuscript for grammatical/language corrections. For example, there should be no “and” in the first line in the result of the abstract “….studies that met inclusion criteria and were included….” Another example, there is no verb in the last line of fifth paragraph of introdcution section “…The reported rspiratory….magnitude…..to factory/industry”.

Reviewer #2: Dear authors,

I have concern with previous published works, which is more convenient than yours. Also, you need to finalize the statistical analysis in the way all the works presents and graph them accordingly.

**********

6. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: No

**********

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PLoS One. 2023 Jul 21;18(7):e0284551. doi: 10.1371/journal.pone.0284551.r002

Author response to Decision Letter 0

24 Feb 2023

Responses

Reviewer #1

1. Paragraph 6 in the introduction section “The prevalence of occupational…….to 69.8% wood factory workers” has some overlapping/repetitive information with paragraph 2 in the discussion section “According to the findings…………contributing factors to the discrepency.” Either paragraph can be rephrased to avoid it.

Thank for your comment. we have revised our manuscript as per your comment

2. Paragraph 7 in the introdcution section starts with “However, the research findings are inconsitent.” Which research findings are inconsistent and why do the authors think so?

Thank you a lot. We revised it. It is necessary to pool the prevalence of respiratory symptoms and associated factors at the factory level due to variations in findings across previously existing primary studies.

3. In the last paragraph of introduction section, the authors should focus and elaborate on the scope of this manuscript compared to previous studies i.e. pooled estimates of prevalence in different industries vs. industry specific prevalence in previous studies.

Thank you very much for your advice. Previous systematic reviews and meta analyses pooled some of the studies conducted outside of industries or outdoor environments, for example, among street sweeping workers. As a result, it is not the correct method because the exposure status and working environment differ in the outdoor and indoor environments. Furthermore, dust control measures differ in the indoor and outdoor environments. Engineering control measures, for example, are inapplicable in an outdoor environment. As a result, estimating pooled prevalence specifically among factory workers was critical in order to implement appropriate prevention and control measures to improve worker and factory owner productivity. Therefore, we conducted this systematic review and meta analysis of studies.

4. Research question should be within the text in the introduction section.

Thank you. We replaced the research questions with the study's objective.

5. It is better to put table 1 in the supplementary information.

Thank you for your constructive feedback. Table 1 was added as supplementary information.

6. It is better to discuss the limitations in the discussion section rather than having a separate section.

Thank you. We revised accordingly.

7. Please revise the manuscript for grammatical/language corrections. For example, there should be no “and” in the first line in the result of the abstract “….studies that met inclusion criteria and were included….” Another example, there is no verb in the last line of fifth paragraph of introdcution section “…The reported rspiratory….magnitude…..to factory/industry”.

Thank you a lot. We revised the the whole manuscript to correct grammatical and language errors.

Reviewer #2

1. I have concern with previous published works, which is more convenient than yours. Also, you need to finalize the statistical analysis in the way all the works presents and graph them accordingly.

Thank for your comment. We changed the entire document in the revised version. This study differs from previous ones in that it focuses primarily on factory workers. However, studies conducted among outdoor workers were included in previous systematic reviews and meta analyses. I believe that including studies conducted among street sweeping workers (outdoor environment) was not the correct approach because exposure status, type of dust generated, and control measures implemented were completely different in indoor and outdoor work environments. As a result, combining outdoor and indoor workplace prevalence is not the best approach. We performed various statistical analyses such as meta regression, sensitivity analysis, and Egger's test.

Attachment

Submitted filename: Response to reviewers.docx

Click here for additional data file. (20KB, docx)

Decision Letter 1

Sebastien Kenmoe

22 Mar 2023

PONE-D-22-30181R1Occupational exposure to dust and Respiratory symptoms among Ethiopian factory workers: a systematic review and meta-analysisPLOS ONE

Dear Dr. Ashuro,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process. While the article presents valuable insights, there are a few areas for improvement.

The authors should provide a PRISMA Checklist to enhance the transparency and completeness of their systematic review. 

The article's methodology should include a clear definition of respiratory symptoms. 

The results of the selection process should be reported as usual for this type of study. Specifically, the study's selection process from L170 to 175 should be presented in the results section.

Please submit your revised manuscript by May 06 2023 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

  • A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.

  • A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.

  • An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols.

We look forward to receiving your revised manuscript.

Kind regards,

Sebastien Kenmoe

Academic Editor

PLOS ONE

Journal Requirements:

Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice.

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

**********

2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

**********

3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

**********

5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: (No Response)

**********

7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

**********

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

PLoS One. 2023 Jul 21;18(7):e0284551. doi: 10.1371/journal.pone.0284551.r004

Author response to Decision Letter 1

1 Apr 2023

Point by point response to reviewers

1. The authors should provide a PRISMA Checklist to enhance the transparency and completeness of their systematic review.

response: Thank for your comment. We provided a PRISMA Checklist as supporting information as per your comment

2. The article's methodology should include a clear definition of respiratory symptoms.

Response: Thank you very much. In the revised version of the manuscript, we defined respiratory symptoms

3. The results of the selection process should be reported as usual for this type of study. Specifically, the study's selection process from L170 to 175 should be presented in the results section

Response: Thank for your comment. In the revised version, we presented the selection process in the results section.

Attachment

Submitted filename: Response to reviewers.docx

Click here for additional data file. (17.9KB, docx)

Decision Letter 2

Sebastien Kenmoe

4 Apr 2023

Occupational exposure to dust and Respiratory symptoms among Ethiopian factory workers: a systematic review and meta-analysis

PONE-D-22-30181R2

Dear Dr. Ashuro,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

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Acceptance letter

Sebastien Kenmoe

13 Apr 2023

PONE-D-22-30181R2

Occupational exposure to dust and Respiratory symptoms among Ethiopian factory workers: A systematic review and meta-analysis

Dear Dr. Ashuro:

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Associated Data

    This section collects any data citations, data availability statements, or supplementary materials included in this article.

    Supplementary Materials

    S1 Table. Summary of search results from PubMed, Google Scholar, Science Direct, African Journals Online, and Web of Science databases.

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    Click here for additional data file. (3.3MB, docx)
    S2 Table. The PRISMA 2020 checklist (Preferred reporting items for systematic review and meta-analysis) is an updated guideline for reporting systematic reviews.

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