Respiratory Research•

Bagasse dust exposure and chronic respiratory symptoms among workers in the Metehara and Wonji sugar factories in Ethiopia: a longitudinal study design

Abstract

Background Ethiopia’s sugar factories are growing by creating job opportunities for thousands of workers with varying educational, professional and socioeconomic backgrounds. These sugar factories are a source of several hazards that severely harm the workers’ health. In this context, there is inconclusive evidence on the level of bagasse dust exposure and chronic respiratory health symptoms. This study aimed to assess the degree of bagasse dust exposure and chronic respiratory health symptoms.

Methods In this longitudinal study, five workstations were selected for dust sampling. A stratified random sampling technique was used to select 1043 participants. We measured the dust intensity using a calibrated handheld real-time dust monitor once a month for 5 months, totalling 50 dust samples. Chronic respiratory symptoms were assessed using the American Thoracic Society’s respiratory symptoms questionnaire.

Results A 1 hour time-weighted average of bagasse dust intensity in the boiler, power turbine and evaporation plant was 8.93 mg/m3, 8.88 mg/m3 and 8.68 mg/m3, respectively. This corresponded to an exposure level to bagasse dust of 85.52% (95% CI 83.2% to 87.6%). The level of chronic respiratory health symptoms was 60.6% (95% CI 59.2% to 61.9%). The most common respiratory symptoms were wheezing (96.8%), coughing (89.7%) and breathlessness (80.9%). The identified risk factors were lack of dust control technology (β= 0.64, 95% CI 0.53 to 0.75), not practising wet spray (β = 0.27, 95% CI 0.21 to 0.41) and not wearing proper respiratory protection devices (β = 0.12, 95% CI 0.30 to 0.56).

Conclusions Bagasse dust exposure and respiratory health abnormalities were worrying concerns. The absence of dust control technologies and no practice of wet spraying elevated the level of exposure. Not wearing proper respiratory protection gear increased the odds of having respiratory abnormalities. Hence, the use of mechanical solutions to stop dust emissions at their sources and the wearing of proper respiratory protection gear are highly advised.

What is already known on this topic

  • Exposure to bagasse dust has been identified as a risk factor for respiratory health. Cross-sectional studies are the foundation of some knowledge.

What this study adds

  • Information on bagasse dust intensity and its deleterious effects on respiratory health contribute to policy thinking for safeguarding industrial employees' health by designing innovative mitigation measures.

  • Area measurements were used in the present investigation. This kind of area sampling is therefore helpful for evaluating the effectiveness of engineering controls in use.

How this study might affect research, practice or policy

  • The study stresses the significance of realising healthcare systems in connection to study outcomes and how, rather than the outcome itself, findings may vary depending on how occupational health and safety services are implemented differently.

Introduction

Bagasse dust (sugarcane fibre) is a by-product of crushing sugar cane. It falls under the category of respirable particles that can enter the lung gas exchange field.1–3 Exposure to these dust particles is supposed to develop bagassosis, a disease specific to the sugar industry.4 The clinical picture of bagassosis resembles that of extrinsic allergic alveolitis caused by other conditions. The disease may appear with increased dyspnoea and cough.5–7 Evidence from India shows that 92% of the employees of the sugar industry were exposed to bagasse dust, and several of them developed respiratory problems.8 The findings in Brazil documented that workers in the sugar industry had lower pulmonary function indices across the spectrum.9 The other finding in India revealed that 32% of workers experience respiratory symptoms possibly linked with exposure to bagasse dust.6 Whereas in Africa, 75% of workers suffered from persistent respiratory symptoms that may be associated with bagasse dust and 54% of the employees presented with pulmonary impairments.10

Regarding the risk factors, prolonged exposure to bagasse dust hurts respiratory health.11 Additionally, the absence of respiratory protection gear and ventilation have been reported to enhance dust exposure.12 Likewise, workers' lack of awareness raised their chances of being exposed to harmful substances and experiencing negative health effects.5 13 Exposure to hazards are also further increased by working more than 48 hours per week, lack of safety training and the failure to use personal protective equipment.14 The existing literature from high sugar producing countries proved the dangers of bagasse dust on respiratory health.15–17 However, some knowledge is based on cross-sectional studies performed.11 18

In the context of Ethiopia, the sugar factories are growing to support the country’s economic development, increasing the need for rural jobs with hundreds of thousands of skilled and unskilled workers with varying educational, professional and socioeconomic backgrounds.19–22 Despite the expected higher exposure levels, there is inconclusive evidence on the level of bagasse dust exposure and its respiratory health impacts among workers in sugar factories in Ethiopia. In this context, this study aimed to assess the degree of bagasse dust exposure and its effects on respiratory health. The findings of this study will help to evaluate the occupational health and safety programme practices and to build a body of knowledge that may have an impact on the Ethiopian public health policy.

Material and methods

Study setting and period

The Wonji Shoa and Metehara sugar factories are two of the biggest sugar factories in Ethiopia, found in the Oromia region, near Adama City, 110 km and 200 km away from the capital city, Addis Ababa, respectively. Wonji Shoa and Metehara sugar factories are designed to have a crushing capacity of 6250 tons and 5100 tons of sugarcane per day, respectively.20 23 24 Nearly 9947 and 10 678 workers are currently employed in the Metehara and Wonji Shoa sugar factories, respectively. The present study was conducted in the Metehara and Wonji Shoa sugar factories from December 2021 to September 2022 (figure 1).

Figure 1
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Figure 1

Map of the study area. Map showing Sugar Estates, including the study areas (Metehara and Wonji), in Ethiopia.

Population

All the workers who were working in the sugar factories in Ethiopia are the study subjects. Workers found in the two factories are also considered as the source and study population. Selected participants from whom the information drawn from was study units.

Study designs

We employed a longitudinal study design (record linkage) to illustrate how bagasse dust exposure intensity and chronic respiratory symptoms change over time at equally spaced time intervals. The advantages of using record linkage study of longitudinal data are the potentially enormous sample sizes, which mean detailed analyses, can be constructed for whole populations and less risk of respondent dropout or reporting errors.25–27 We followed the same units of interest (workstations) to obtain representative and optimal number of observations. Then, we associated a work section-level record of dust intensity for workers in the chosen work sections to determine the level of dust exposure and chronic respiratory symptoms.

Patient and public involvement

The study did not involve patients. Study findings are being made publicly available to participants and the general public through study reports and open access journal articles. The study web pages provide contact details of the research team if anyone wishes to directly request the publications.

Selection criteria

We included all participants above 18 years of age who had direct exposure to sugarcane dust working in a web pages (where bagasse was burned to provide energy). On the other hand, we excluded those who had self-reported history of heart problems, recent surgery of the thorax or abdomen, and had severe respiratory disease, any acute illness before being employed as a sugarcane worker and on medical treatment.

Sample size determination and sampling techniques

The sample size was calculated using Epi Info V.7 by considering different parameters. Accordingly, the factors associated with the outcome variable (working over 48 hours weekly) produced the largest sample size. After considering the design effect of 1.5, adding 5% non-response rate, 95% CI, power=80%, ratio 1:1, and P1=52.3% of percentage of outcome in the exposed group,12 taking OR=1.75, yielded the final sample size of 1043. Using a stratified sampling technique, the calculated sample size was distributed across the selected five departments, assuming that occupational exposure to bagasse dust varies with the work. We allocated the study participants proportionally from each department, and finally, we drew the study units using a simple random sampling technique from each department’s sampling frame. In this study, same departments of interest were followed up for 5 months, and the measurements were performed monthly. Given that, the study took 50 dust samples. In this investigation, the dust sampler was installed in each department of the two chosen sugar factories (Wonji Shoa and Metehara) for a similar duration and time. The dust concentration was measured by the same devices separately for the two sugar factors.

Operational definitions

Bagasse dust exposure

Bagasse dust exposure refers to the measured concentration of bagasse dust exceeding the recommended exposure limit of 5 mg/m3 set by the National Institute for Occupational Safety and Health (NIOSH). Te participants were deemed occupationally exposed,28 29 else were considered as non-exposed.

Chronic respiratory symptoms

The development of one or more of the symptoms of cough, cough with sputum, wheezing, breathlessness and work-related shortness of breath which lasts at least three consecutive months in one year.30

Cough

Participants were considered to have coughed if they answered ‘yes’ to at least one of the following four questions; cough first thing in the morning, cough during the day or night, cough as much as four to six times a day in a week, or cough for most days for as much as three consecutive months during the year.31

Cough with sputum

Participants were considered to have cough with sputum if they answered ‘yes’ to at least one of the four questions: cough with sputum first thing in the morning, cough with sputum during the day or night, cough with sputum as much as four to six times a day in a week, or cough with sputum for most days for as much as three consecutive months during the year.31

Breathlessness

Participants were considered to have breathlessness if he/she was troubled by shortness of breath when hurrying on level ground or walking up a slight hill, or get shortness of breath when walking at his/her own pace on the level ground or get shortness of breath when walking with other people of your own age on level ground.31

Work-related shortness of breath

Participants were considered to have work-related shortness of breath if he/she usually experienced chest tightness while at work or just after work.31

Wheezing

Participants were considered to have wheezing if his/her chest ever sounded wheezy (whistling sound).31

Bagasse dust measurement strategy and exposure assessment method

A static (area) measurements strategy was conducted to measure the concentration of dust. We measured the dust concentration using a handheld real-time (direct-reading) dust monitor (Casella, Model 880 nm, UK) at fixed individual unit operations (workstations) where the workers spent most of their time. Bagasse dust was sampled in all randomly selected areas of the processing plant such as the boiler, evaporation pant, power turbine, vacuum plant and pan out operation. These workstations varied in the exposure status as the monthly sugarcane crushing capacity varied and the amount of dust generated in the department also different. Also the dust control techniques at the sources of emissions and along the paths also had some variations along the selected workstations. We took monthly measurements in the same workstations for five consecutive months on representative working days for the factory operations. To define employees' exposure, the study employed a sampling period (duration) of 1 hour from 8:00 to 9:00 for half the morning shift (for 4 hours), which agrees with the NIOSH manual that considers using either full time or a portion of time with the assumption that exposure was similar.32 For fine particulate matter assessed in this investigation, we used a corrected calibration factor based on outside wood smoke,33 which is assumed to represent a suitable analogue for sugarcane particulate. After the correction, the study calculated 1 hour time-weighted average (TWA) for each of the measurements from the data using the following equation:

Display Formula

Where; C1 is dust concentration during the ith interval and t1 is the duration of the ith interval.

We used a structured interviewer-administered questionnaire to identify the factors associated with exposure to bagasse dust. In this investigation, trained data collectors interviewed the eligible participants at the time the dust intensity was measured. We conducted a daily walk-through survey to observe whether the workers in the sampled work sections used personal protective equipment.

Assessment of chronic respiratory symptoms

The participants were asked about respiratory symptoms in the preceding 12 months and the past 3 months (covering only the current season) during the active sugar-crushing seasons (December through May 2022) and non-active sugar-crushing seasons (after 24 May 2022). We assessed chronic respiratory symptoms with a face-to-face interview using a standardised questionnaire from the American Thoracic Society34 with certain modifications. The study picked a chronic respiratory symptom since the objective was to assess long-term dust exposure and its effects on respiratory health, which are best represented by chronic respiratory symptoms. The questionnaire included sociodemographics, occupational history, past respiratory diseases (pneumonia, tuberculosis, bronchitis, asthma and chest injury), use of respiratory protective devices while working (yes or no), and smoking habits (yes or no). The questionnaire also included questions about chronic respiratory symptoms, including cough, cough with sputum, breathlessness, work-related shortness of breath and wheezing. Participants were considered to have coughed and coughed with sputum if they answered ‘yes’ to at least one of the four questions assessing cough and cough with sputum, respectively. Participants were considered to have breathlessness if ‘yes’ to at least one of the three questions for breathlessness. Work-related shortness of breath and wheezing was defined as present if the participants answered ‘yes’ to a single question assessing work-related shortness of breath and wheezing, respectively.

Data quality assurance

The dust sampler instrument was calibrated based on the manufacturer’s instructions.35 The principal investigator (PI) trained data collectors for 2 days on the purpose of the study, the contents of the questionnaire, measurement instruments, communication skills and research ethics to reduce bias. The PI prepared an observational checklist, monitored the data collectors and informed them of proper protocols. We selected four occupational health and safety experts, two graduate nurses, three safety technicians and one expert in public health research (n=10) as data collectors. For the interview, a standardised questionnaire modified from the American Thoracic Society was used to assure data quality. An expert translated the questionnaires first from English to Amharic and back-translated to English using a standard procedure to check its validity. Pretesting was conducted to check the reliability and validity of the data collection tools and necessary corrections were taken.

Questionnaire data reliability

Cronbach’s α test was used to measure the question or item consistency. It is the most common method used for measuring reliability.36 37 A Cronbach’s α value of around 0.8 was considered good.36 Our results showed that, the anticipated scale item’s overall Cronbach’s alpha coefficients were 0.875. Consequently, the anticipated scales used in this investigation show great dependability indicating that the questions or items have good internal consistency and reliability.

Statistical analysis methods

All statistical analyses were performed using the Statistical Package for Social Sciences software (V.26). A generalised estimating equations (GEE) model was used to model occupational dust exposure and chronic respiratory symptoms. Direction and strength of association were expressed using a beta coefficients with a 95% CI. A value of p<0.05 was considered statistically significant. We chose the best fitting working correlation matrix by looking at the lowest quasi-likelihood under independence model criterion. The working correlation structure chosen in the analysis was auto-regressive order 1. GEE is assumed to be robust against the choice of an incorrect correlation structure.38 In our study, most dust concentrations showed a log normal distribution. Hence, the study summarised the dust concentrations as geometric means (GMs) and geometric SDs (GSDs). Regarding model fitness, the Hosmer-Lemeshow test was used (p = 0.49),39which indicates that the degree of exposure and respiratory symptoms were not significantly different from those predicted by the model and that the overall model fit was good.

Also, we carried out a multicollinearity diagnosis using the correlation matrix method, and all values were well below 0.20, which confirmed that multicollinearity among the predictor variables was not a concern for the model. This paper was reported in accordance with the Strengthening the Reporting of Observational Studies in Epidemiology statement to improve its quality and address the key elements of the report.40

Results

Sociodemographic characteristics of the study participants

All the study participants completed the questionnaire, making a response rate of 100%; of these 96% were men. Almost 70.6% of participants had full-time employment. Also, 57.1% of the participants were over 48 years old. In terms of education, 34% had a college diploma and 22.4% had a secondary (9–12 grade) diploma. Besides, 84.7% of the participants had work experience of over 11 years (table 1).

Table 1
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Sociodemographic characteristics of participants in Metehara and Wonji sugar factories in Ethiopia, 2023 (n=1043)

Engineering and working condition related characteristics

This study found that 679 (65.1%) of the study participants reported there was no practice of wet spraying in the factory to manage dust spread. Also, 682 (65.4%) of the study participants said there was no dust control technology that could control the dust at the sources of emission. This study demonstrated that 685 (65.7%) of the study participants described that there was no enforcement of wearing of respiratory protective devices. Additionally, 691 (66.3%) of the study participants described the absence of work rotation schemes. This study illustrated that 688 (66%) of the study participants indicated a lack of periodic medical examinations or health check-ups (table 2).

Table 2
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Engineering and working conditions related characteristics in Metehara and Wonji sugar factories in Ethiopia, 2023 (n=1043)

Personal characteristics of the study participants

This study revealed that 686 (65.8%) of the study participants didn’t consistently wear respiratory protective devices. The common reasons for not using respiratory protective devices were: 27.5% of the participants said the devices weren’t available; 26.0% of the devices didn’t give adequate protection from dust; and 20.8% of the devices were uncomfortable. We also found that only 32.7% of the study participants received training on respiratory protection device care and utilisation (table 3).

Table 3
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Personal characteristics of the study participants in Metehara and Wonji sugar factories in Ethiopia, 2023 (1043)

Bagasse dust intensity and level of occupational exposure

We collected 5041 valid dust samples from five workstations in the chosen sugar factory. In the last sampling period, the scores of GM±GSD of bagasse dust concentrations were 9.55 (0.11) and 7.89 (0.91) mg/m3 in the boiler and power turbine sections, respectively. We found that the 1 hour TWA of bagasse dust intensity in the boiler, power turbine and evaporation plant was 8.93 mg/m3, 8.88 mg/m3 and 8.68 mg/m3, respectively. This corresponded to an exposure level to bagasse dust of 892 (85.52%), along with a 95% CI of 83.2% to 87.6%, which exceeded the recommended exposure limit (table 4).

Table 4
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Bagasse dust concentration in the area sampled in Metehara and Wonji sugar factories in Ethiopia, 2023

The spectrum of chronic respiratory health symptoms

This study revealed that 632 (60.6%) (95% CI 59.2% to 61.9%) of the participants had experienced at least one chronic respiratory symptom during the active sugarcane crushing period and 24% (95% CI 21.6% to 26.7%) after the sugarcane crushing season was completed. During the active sugarcane crushing phase, the most frequently reported chronic respiratory health symptoms were wheezing (982=96.8%), coughing (910=89.7%), breathlessness (820=80.9%) and work-related shortness of breath (630=62.1%), as compared with non-active sugarcane crushing seasons, which were likely explained by occupational exposure to bagasse dust (figure 2).

Figure 2
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Figure 2

Chronic respiratory symptoms. Percentage of chronic respiratory symptoms among the study participants in Metehara and Wonji sugar factories in Ehiopia.

Determinants of bagasse dust exposure

After controlling for the other factors in the model using multivariate analysis using the GEE model with an identity link function, the absence of routine machine maintenance, the absence of total enclosure of dusty work settings, the lack of dust control technology, the absence of wetting practices, the lack of proper respiratory protective devices, and the absence of a job rotation system, were statistically associated with bagasse dust exposure (table 5).

Table 5
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A generalised estimating equation model for predictors of exposure to bagasse dust in Metehara and Wonji sugar factories in Ethiopia, 2023

This study showed that there was a significant effect of the lack of routine machine maintenance, that is, for every 1-point increase in the lack of routine machine maintenance score, there was about a 0.27 increase in the dust exposure score (β=0.27, 95% CI 0.16 to 0.38). In this study, every 1-point increase in the absence of total enclosure of sources of dust emission score, resulted in a 0.35 increase in the dust exposure score (β=0.35, 95% CI 0.17 to 0.54). There was a 0.64 increase in exposure to bagasse dust for every 1-point rise in the absence of dust control technology score (β=0.64, 95% CI 0.53 to 0.75). For every 1-unit increase in the absence of a job rotation score, there was about a 0.47-unit increase in exposure to bagasse dust score (β=0.47, 95% CI 0.38 to 0.56). For every 1-unit rise in the non-wearing of respiratory protection gear score, the exposure to bagasse dust score increased by 0.36 (β=0.36, 95% CI 0.22 to 0.49). The dust exposure score increased on average by 0.27 points for each day not practising wet spray (β=0.27, 95% CI 0.12 to 0.41) (table 5).

Determinants of chronic respiratory health problems

In this study, not being properly trained in the use of respirators, not wearing respiratory protection masks, being exposed to bagasse dust, failure to follow respiratory safety tips, being over the age of 48 years, and lack of ventilation were statistically associated with exacerbating factors of chronic respiratory symptoms in a fully adjusted model (table 6).

Table 6
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A generalised estimating equation model for predictors of chronic respiratory health symptoms among the study participants in Metehara and Wonji sugar factories in Ethiopia, 2023

The odds of developing chronic respiratory symptoms were 1.86 times higher for workers who weren’t properly trained in the use of respirators than their counterparts (adjusted OR (AOR)=1.86, 95% CI 1.46 to 2.23). The odds of sustaining chronic respiratory symptoms were 2.08 times higher for workers who didn't wear respiratory protection masks than for their fellow counterparts (AOR=2.08; 95% CI 1.30 to 3.08). The odds of experiencing chronic respiratory symptoms were 4.79 times higher for workers exposed to bagasse dust (AOR=4.79, 95% CI 2.46 to 9.33). The odds of developing chronic respiratory symptoms were 2.31 times higher among workers who failed to follow respiratory safety tips than their counterparts (AOR=2.31; 95% CI 1.59 to 3.35). The odds of developing chronic respiratory symptoms were 3.89 times higher for workers who were over the age of 48 years (AOR=3.89, 95% CI 2.19 to 6.90). Finally, the odds of experiencing chronic respiratory problems were 3.50 times higher among workers who worked in areas without mechanical ventilation (AOR=3.50, 95% CI 2.02 to 6.06) (table 6).

Discussions

Data-driven evidence on occupational dust exposure and its respiratory health impacts should provide relevant stakeholders with a better understanding of the issue. This knowledge aids them in creating a safe working environment, enhancing organisational productivity and having a favourable impact on legislators' decisions. This study demonstrated that a significant percentage of employees in Ethiopia’s Metehara and Wonji sugar factories were exposed to a significant amount of bagasse dust that exceeded the recommended limit, resulting in a considerable burden of chronic respiratory ailments. When compared with research conducted in China,42 Pakistan,43 Thailand,2 UK,1 India,44 45 Central America46 and Brazil,47 48 this study discovered a higher level of bagasse dust exposure. The possible explanations for this disparity could be related to the different techniques of controlling dust emissions at their sources, the nature of the machines used, the organisational safety infrastructure, and the sample sizes and sampling strategies used. There was much overcrowding and very old machinery used in the present study area that could be responsible for high dust emissions, which elevated the level of exposure as well. The other difference can be attributed to methodological variation because earlier research knowledge was based on cross-sectional studies.

In this investigation, the level of bagasse dust exposure was lower than in the previous studies in South Africa,49 Indonesia50 and Brazil.41 51 All of these studies showed high levels of bagasse dust intensity. This deviation may be well explained by the numbers and durations of samples collected. As we only sampled for half of the morning shift, the assumption was that exposure was similar. Other causes of disparity in dust exposure levels could be related to the sampling approach used, the monthly sugar crushing capacity of the firms, the size of the sugar plants covered and the sources of population. There was a slight decrease in sugarcane crushing capacity during the sampling period in our study locations, which could reduce dust emissions and possibly the level of exposure. We didn't gather air samples from worker proxies' breathing zones for this study; instead, we collected them from fixed locations, in contrast to earlier studies. This was due to logistical challenges in obtaining air quality devices and lack of time.

In practice, in the majority of the examined workstations, the average mass concentration of bagasse dust was extremely high. This implies that sugarcane workers are subjected to a significant amount of particulate matter exposure. There is a scarcity of information on bagasse dust exposure and its consequences for sugarcane workers' health. Until recently, studies examining the effects of post-meridian exposure have primarily focused on cardiovascular disorders and ocular effects.52 53

In this study, substantial numbers of participants experienced heavy burdens of chronic respiratory symptoms. This could be related to the high concentration of bagasse dust that can affect the nasal passages, causing an irritated and congested nose, and might also cause an irritant cough should it deposit in the throat. This study also illustrated that individual indices of chronic respiratory symptoms, such as wheezing, cough, breathlessness and work-related shortness of breath, were shown to be more common during the active sugar-crushing period compared with the non-operational seasons, which were anticipated to have less dust. As the dust can penetrate beyond the extrathoracic regions, staying in an area with a high dust concentration for a longer duration is responsible for respiratory problems. Our findings were inconsistent with previous studies conducted in India,13 18 54 Croatia,5 Brazil,55–58 Japan,59 Thailand60 and Central America,61 that reported a lower prevalence of chronic respiratory symptoms. This disparity in symptom prevalence could be explained by differences in dust exposure level, duration of exposure, knowledge of the workers, and access to respiratory protection devices. In our findings, because many of the workers lacked the right respiratory protection, it’s more likely that they experienced respiratory disorders. Also, there may have been other factors that influenced the workers' respiratory health that were not found in this study. The observed difference could also be explained by the study setting in which it was done and the large sample size of the current study.

In this study, the prevalence of a cough with sputum, breathlessness and wheezing in our study was higher than in the studies in India.62 63 This can be a result of the two countries' organisational respiratory protection measures being provided and enforced differently; the workers have access to respiratory protection devices in Indian factories, whereas the vast majority of workers in our study area had no access to respiratory protection equipment. For a cough and work-related shortness of breath, we found a higher prevalence than that reported in the studies in Pakistan64 and India.65 66 This difference might be due to higher dust exposure intensity in the present study compared with what was measured in India and Pakistan. In addition, the difference in working environments, sugar processing methods and level of awareness among the workers about the impact of dust exposure could be the reason for the difference in symptom prevalence. The other observation is that there may be differences between these countries regarding the presence of, for instance, lung infections. Infections may cause respiratory symptoms. This possibility is not very likely, as the examined workers are performing hard physical work, but this factor needs to be considered, because of the high prevalence of tuberculosis as well as HIV in East Africa.67 However, we found a higher prevalence of some of the respiratory symptoms compared with the studies conducted in India,68 where the prevalence of cough and breathlessness was very low. Bagassosis belongs to the group of respiratory conditions classified as interstitial lung diseases or hypersensitivity pneumonitis. It presents similarly to other extrinsic allergic alveolitis, such as farmer’s lung. It develops in a patient due to exposure and inhalation of bagasse—the residual fibrous material after sugar is extracted from sugar cane.69

Although we used validated questions in assessing chronic respiratory symptoms, the responses could also indicate acute symptoms. It might be difficult to tell the difference between these two types of symptoms because they often occur at the same time.70 The findings clearly show that these employees are experiencing symptoms that should not be present in the workplace, and their work environment should be investigated further.

Moreover, this study found that the absence of dust control technology was a major contributor to bagasse dust exposure, despite the paucity of information. This means that workers who operate in areas without dust control technologies installed have higher odds of dust exposure than their counterparts (p=0.01). This could be due to the fact that when effective dust control measures are not implemented, dust spreads easily throughout the work area, mainly increasing exposure levels. Employees and others in the area can breathe in the specks of dust that are released into the air. Workers who do not have access to the appropriate respiratory protection equipment are largely exposed to significant quantities of dust (p=0.01). An established set of literature on device-related issues backed up our findings,71–73 which found that workers who don’t get the proper respiratory protection equipment have elevated odds of dust exposure. This could be due to the fact that the devices didn’t provide adequate protection. Yet, the respiratory protection equipment in particular is heavily influenced by factors including training, proper fit, organisational safety culture and workers’ own perception of risk.74 We were unable to locate any study that showed the impact of total enclosure of dusty work areas on reducing bagasse dust exposure levels during our search. However, this study highlighted that there was a higher risk of bagasse dust exposure when dusty work areas were not completely enclosed (p=0.01). The present study revealed that when operating machines aren't consistently maintained as indicated by the manufacturer’s recommendation, they become old, which in turn emitted excessive dust, increasing the odds of workers being exposed to it.

The findings of the present study revealed that every 1-point increase in the lack of practising wet spray considerably raises the odds of bagasse dust exposure (p=0.03). When a system of water sprays was not used, each dust particle’s weight decreased, thus increasing the particle’s ability to become airborne. Every 1-point increase in limited work rotation increased the likelihood of bagasse dust exposure considerably (p=0.02). Job rotation and reduction of work periods can help manage worker exposure, but this method of controlling the exposure to dust must be used with care. As an example, decreasing the exposure duration for one employee below exposure limits may increase the number of other employees exposed to a contaminant. Similar findings to ours have been reported in other investigations.12 75

When proper training in the use of respiratory protection devices was not received, it could increase the odds of sustaining chronic respiratory symptoms, according to the current study (p=0.001). Our results confirmed previously published works, which mentioned that not having sufficient training on personal protective equipment increases the risk of experiencing respiratory symptoms.76 77 One likely interpretation is that workers who are less knowledgeable about how to use and care for respiratory protection devices, have a higher odds of getting chronic respiratory ailments than their counterparts. Previous studies supported our findings which stated that the odds of developing respiratory symptoms were significantly associated with not wearing respiratory protection masks.78 79 The explanation for this could be dust deposition in the airways capable of penetrating the gas-exchange region of the lung.

When compared with employees who are not exposed to dust, those who are exposed to bagasse dust have a higher odds of developing chronic respiratory symptoms (p=0.01). This could be related to the concentration and size of the particles (site of deposition within the respiratory systems) in the current study that determines the respiratory health effects. Some previous research has found that being exposed to bagasse dust increases the likelihood of acquiring persistent respiratory problems as we did.80–82 Inhalation of bagasse dust, which produces deposition in the airways and may weaken the body’s defence mechanisms, could be the cause. Workers are likely to be exposed to high concentrations of bagasse dust and are at risk of respiratory diseases. Another fact is that a lack of local exhaust ventilation also created a condition that generated and suspended dust around the breathing area of the workers.

Despite the lack of evidence linking chronic respiratory symptoms to failure to follow respiratory safety tips, we found that not following respiratory safety tips increased the odds of developing chronic respiratory symptoms and getting sick (p=0.00). The other observation is that, when working around airborne particles or debris, the employees might not be sure to wear either a full-mask respirator or a face shield along with the respirator. In addition, being over the age of 48 years elevated chronic respiratory symptoms. This could be because as the age increases the immunity systems of the workers decreased. Our finding is supported by literature.45 In this study, a lack of ventilation has a substantial impact on respiratory disorders. This could be due to the fact that indoor-generated pollutants weren’t removed from the air or diluted to appropriate levels, which led to an increase in respiratory complaints. Despite the fact that a respirator is the first line of protection, workers in poorly ventilated regions run the danger of contracting respiratory symptoms.

This study has contributed to the body of knowledge on the impacts of bagasse dust exposure on workers' respiratory health by offering crucial empirical research information on the applicability of longitudinal studies. It offered trustworthy information to those who should have access to it, including those who operate boilers, staff members, occupational health and safety officers, researchers and students who are interested in longitudinal research. The utilisation of longitudinal research to improve our comprehension of the level of dust exposure and its impact on respiratory health, which could guide policy planning and the implementation of programmes to promote mitigation techniques, further fills the gap in the literature on dust exposure at work.

To avoid measurement bias, data collectors were trained optimally, and great care was taken at each stage of the sampling process, including monitoring the required flow rate, the position of the sampling head and sampling duration during the entire shift. Great care was also given to tool preparation during questionnaire development, and all the study participants were asked the same questions and we found that they gave consistent answers to the questions.

Strengths of the study

Bagasse dust exposure and chronic respiratory symptoms were investigated in large sugar factories with five repeated measurements. Hence, the results of 5 months of repeated sampling in Ethiopia’s two main sugar factories are probably typical of the whole Ethiopian sugar factory.

Limitations of the study

Our findings should be viewed in light of some limitations. We haven’t done the lung function tests or assessed the degree of personal bagasse dust exposure. Also, the chemical make-up of particles has mostly remained unknown as a gravimetric analysis was not done. Besides, the entire working day should be examined to determine bagasse dust exposure. But we explored employing only half of the morning shift because we thought the tasks were similar throughout the day.

Conclusions and recommendations

The concentration of bagasse dust in this study was confirmed to be above the advised exposure limit. Bagasse dust exposure and respiratory health abnormalities were worrying concerns. This study proved that a lack of routine machine maintenance, an absence of complete enclosure of the dusty work area, a lack of dust control technology, limited job rotation, not practising wet spray, and a lack of respiratory protective gear increased bagasse dust exposure levels. Additionally, not being appropriately trained in the use of respirators, not wearing respiratory protection masks, being exposed to bagasse dust, failing to follow respiratory safety instructions, being over the age of 48 years, and the absence of ventilation elevated the odds of respiratory health conditions. According to our findings, the information on bagasse dust intensity and its detrimental impacts on respiratory health is sufficient to start policy revisions to design innovative mitigating measures. Special attention should also be given during the active sugar production period. Therefore, stakeholders should put mitigation strategies into practice, including mechanical solutions and providing employees with the proper respiratory protection equipment. Finally, future research, including cohort studies, should further address the degree of personal bagasse dust exposure and the status of the ventilatory lung function parameters with a combination of sampling methods of area and personal measurements of dust.

Overview

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