Industrialization has been established to optimally fulfill various human needs. Over the course of time, some industries exert hazardous effect on the health of human beings [
Occupational lung diseases are a broad group of diagnosis caused by the inhalation of dusts and chemicals. As a result, improper control of these substances can result in a severe threat to site workers because most of the workers are unaware of this hazardous effect on health [
Flour dust is a heterogeneous substance with respiratory sensitizing properties and long-term exposure to it may cause acute or chronic respiratory disease [
The study aims to investigate the effect of flour dust on the pulmonary function by analyzing the pulmonary function tests that will estimate the effectiveness of the lung. This study is therefore undertaken to assess the respiratory symptoms and pulmonary function problems related to flour mill workers. It will also encourage communication between various concerned groups and organizations and foster an improved understanding of the potential problems of flour dust in the country.
Comparative cross-sectional study design was employed to assess respiratory symptoms and pulmonary function parameters in workers of flour mills. The study was conducted in Lideta subcity, Addis Ababa, Ethiopia, from August to September 2016. Addis Ababa encompasses 10 subcities and 116 woredas. It is located at altitude of 2,400 meters above sea level. Based on the data from Lideta subcity trade and development bureau and urban agriculture corporation, ten of 116 woredas are located in Lideta subcity containing a total of 76 flour mills during a time of data collection.
The source populations were all flour mill workers in Addis Ababa city, Ethiopia. The study population were all flour mill workers and controls in Lideta subcity in the age range between 18 and 43 years.
Double proportion formula was used for the determination of sample size. The proportions of the sample size were calculated from previous study on association of flour dust on PFTs and prevalence of respiratory symptoms of chronic cough for flour mill workers and control groups (37% vs. 13%, respectively) [
Millers who were available in the workplace between the age range of 18 and 64 years and working in the flour mill for more than one year were included.
Subjects with gross clinical abnormalities of the vertebral column, thoracic cage, neuromuscular diseases, known cases of gross anemia, diabetes mellitus, pulmonary tuberculosis, hypertension, drug addicts, known cardio pulmonary disease, cigarette smokers, tobacco and khat chewers, bakery workers, and those who underwent vigorous exercise or abdominal or chest surgery were excluded from the study.
The sample consisted of all flour mill workers in the mill and matched non-flour mill workers in Addis Ababa, Lideta subcity. Lideta subcity was selected randomly by lottery method of the ten subcities. Lideta subcity contains 10 woredas and 76 flour mills. Among 10 woredas 4 woredas were selected by random sampling. There are 30 flour mills in the 4 woredas and 24 flour mills in the 4 woredas were selected for this study until sample size was saturated. Non-flour mill workers in Lideta subcity matched for age, sex, height, and weight to flour mill workers were selected as controls. Flour mill workers and controls age was 18-64 years selected by convenient sampling technique. Selected flour mill workers and controls fulfilling eligibility criteria were interviewed and anthropometry was measured and finally spirometry was done.
Each participant was informed about the objective of the study and the benefit associated with the study immediately before sample collection. Millers who volunteered to participate in the study have answered questions in the questionnaire, which were relevant to their sociodemographic information. A structured questionnaire was prepared in English and translated into Amharic language and was retranslated back to English by a linguist to ensure consistency. Training was given to the data collectors regarding the objectives of the study and ways of administering the questionnaire by the principal investigator. The prepared questionnaire was pretested prior to the actual data collection on seven (7) informants that were not included in the main survey.
Height and weight of the study participants were measured. The height was measured without shoes by the use of a meter rule and approximated to the nearest one cm. Weight was also measured using weighing scale (nearest to one kg), with light clothing and without phones or any encumbrance that could alter their appropriate weight. Body mass index (BMI) was calculated through this formula: weight/squared height (kg/m2)
Digital pocket-sized Spiro Pro (JEAGER, Germany) was used to measure pulmonary function indices. Spirometric tests in both exposed and control subjects were done based on ATS guideline. Before every test, the mouthpiece was disinfected in standard solution and then attached to the spirometer. Subjects were told to put the nosepiece on the nose to prevent air blowout. Then, they were also instructed to breathe in fully until their lung filled maximally. Precaution was taken to avoid leakage from mouth pieces. The subjects expire forcefully and as fast and complete as possible until there is no more air left to expel. Spirometric measurements were performed in sitting position and at a fixed time of the day at room temperature (20-25°C), to minimize diurnal variations. The measurements were done in three trials, and one of the three trials, which was the best, was taken and interpreted. Prior to the actual tests, calibration with one-liter syringe and familiarization steps were done.
Data was edited, coded, entered, and analyzed by SPSS version 20. Independent sample t-test was used for the comparison of the actual value mean respiratory score of flour mill workers and controls. Bivariate analyses were computed to test whether there was association between FVC, FEV1, FEV1/FVC, PEFR, and FEF25%
The study was carried out after ethical clearance and approval was obtained from research committee of the Department of Physiology, Addis Ababa University. The study participants were briefed about the objective and procedures of the study. Thereafter, both verbal and written informed consents were obtained from those volunteers and were selected for the study. Confidentiality of information was maintained by excluding personal identifiers.
All workers included in the study were males. The age of the flour mill workers ranged between 18 and 43 years with a mean of 27.37±6.71 years while the age of the comparison group ranged between 18 and 43 years with a mean of 28.00±5.33 years (Table
Sociodemographic information of flour mill workers and controls.
Variables | Descriptions | Flour mill workers (n=54) | Control Group(n=54) | P –value |
---|---|---|---|---|
Age range(in years) | 18-23 | (n=20)37.03% | (n=13) 20.04% | |
24-28 | (n=15) 27.7% | (n=20) 37.03% | 0.591 | |
29-33 | (n=7) 12.9% | (n=12) 22.2% | ||
34-38 | (n=6) 11.1% | (n=7)12.9% | ||
39-43 | (n=6)11.1% | (n=2) 3.7% | ||
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Educational status | Illiterate | (n= 9) 16.6% | 0(0) | |
Can write and read | (n= 19) 35.1% | (n=4) 7.4% | ||
Grade 8 complete | (n= 15) 27.7% | (n=1) 1.8% | <0.01 | |
Grade 10 complete | (n= 8)14.8% | (n=15) 27.7% | ||
Grade 12 complete | (n= 1) 1.8% | (n= 18) 33.3% | ||
Diploma | 0(0) | (n= 6)11.1% | ||
| (n=2) 3.7% | (n=10)18.5% | ||
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Marital status | Single | (n=37) 68.5% | (n= 35) 64.8% | |
Married | (n= 14) 25.9% | (n= 17) 31.4% | 0.868 | |
Divorced | (n=3) 5.5% | (n=2) 3.7% |
Personal protective devices used by the workers were investigated in the study area. Among workers, 57.4% (n= 31) do not wear any equipment, 9.3% (n=5) wear safety shoes, masks, and gloves, and 33.3% (n=18) wear only masks (Figure
Bar chart indicating the use of personal protective equipment.
Anthropometric parameters of the study subjects in terms of demographic variables demonstrate the comparison between the flour mill workers and their matched control subjects. There were no significant differences between the means of anthropometric parameters: in terms of age, weight, height, and BMI between the groups. The statistical comparison of the matching variables (age, height, weight, and BMI) shows no difference between the two groups (Table
The anthropometric measurements for flour mill workers and control groups by independent sample t-test.
Parameters | Exposed group( n=54) | Non exposed group (n=54) | P-value |
---|---|---|---|
Age (years) | 27.37±6.71 | 28.00±5.33 | 0.591 |
Weight (kg) | 59.72±7.76 | 61.91±6.39 | 0.113 |
Height (meter) | 1.66±0.07 | 1.68±0.05 | 0.388 |
BMI (kg/m2) | 21.42±2.25 | 21.95±1.82 | 0.185 |
The percentage prevalence of dry cough, productive cough, wheeze, and breathlessness was 27.7%, 11.1%, 14.8%, and 16.6% for exposed informants, respectively, and 9.3%, 5.6%, 3.7%, and 7.4% for control subjects, respectively (Table
Respiratory symptoms of exposed and nonexposed subjects including OR and 95% CI.
Respiratory symptoms | Prevalence | OR | P-value | 95% CI | ||
---|---|---|---|---|---|---|
Lower | upper | |||||
Dry Cough | case | 27.7%(n=15) | ||||
Control | 9.3%(n=5) | 3.58 | .027 | 1.16 | 11.65 | |
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Productive cough | case | 11.1%(n=6) | ||||
Control | 5.6%(n=3) | 1.76 | .467 | 0.39 | 7.98 | |
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Wheeze | case | 14.8% (n=8) | ||||
Control | 3.7%(n=2) | 4.25 | .084 | 0.83 | 21.88 | |
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Breathlessness | case | 16.6 %(n=9) | ||||
Control | 7.4%(n=4) | 2.80 | .115 | 0.78 | 10.09 |
Binary logistic regression was used to compare the respiratory symptoms and measure the strength of the association. The odds of dry cough in flour mill workers exposed to flour dust association were found to be statistically significant (p<0.05).
Percentage predicted values of exposed and control groups were indicated (Table
Percentage predicted lung function tests of exposed and control groups.
Pulmonary function test Parameters | Groups( case n=54 and control n=54) | Mean ±SD | p-value |
---|---|---|---|
FVC(L) | Case | 88.59±19.05 | 0.000 |
Control | 107.98±14.05 | ||
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FEV1 (L) | Case | 87.80±20.47 | 0.000 |
Control | 108.93±16.98 | ||
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FEV1/FVC | Case | 98.56±15.99 | 0.271 |
Control | 102.01±16.35 | ||
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PEFR(L/s) | Case | 59.76±25.37 | 0.000 |
Control | 83.00±27.32 | ||
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FEF25% | Case | 88.83±35.08 | 0.001 |
Control | 115.09±31.34 |
The independent sample t-test (Table
The comparison of the actual value mean spirometric indices of exposed and nonexposed groups by independent sample t-test.
PFTs Parameters | Flour mill workers n=54 and controls n=54) | Mean ±SD | p-value |
---|---|---|---|
FVC(L) | Flour mill workers | | p<0.001 |
Control | | ||
| |||
FEV1 (L) | Flour mill workers | | p<0.001 |
Control | | ||
| |||
FEV1% | Flour mill workers | | |
Control | | ||
| |||
PEFR(L/s) | Flour mill workers | | |
Control | | ||
| |||
FEF25% | Flour mill workers | 3.87±1.61 | p<0.05 |
Control | 4.60±1.60 |
There was slight reduction in pulmonary function indices (FVC, FEV1, and FEV1/FVC, PEFR and FEF25%
Pearson correlation coefficient results between pulmonary function parameters and duration of exposure.
Variables | “r” –value | P-value |
---|---|---|
FVC | -0.417 | 0.000 |
FEV1 | -0.359 | 0.000 |
FEV1/FVC | 0.060 | 0.535 |
PEFR | -0.236 | 0.014 |
FEF25% | -0.156 | 0.123 |
Flour mill workers were suffering from both obstructive and restrictive disorder. Based on PFTs interpretation results indicate reduction in the pulmonary function efficiency among the flour mill workers. Airflow obstruction which reduces dynamic airway collapse makes expiration difficult. FEV1/FVC ratio <0.7 and FEV1 value <80% percentage predicted are considered as obstructive pattern. Restrictive defect needs large amount of elastic work to inflate the lung, which makes inspiration difficult. FEV1 /FVC ratio >0. 7 and FVC value <80% of percentage predicted are restrictive pattern.
Among 54 flour mill workers (n=15), 27.7% developed restrictive and (n=6) 11.1% developed obstructive type of lung disorder. The rest of the study subjects 61.1% (n=33) had normal pulmonary function. Two subjects (3.7%) in the control group developed obstructive type of lung disorder and the rest of the subjects had normal pulmonary function status (Figure
Bar chart showing the number of obstructive, restrictive, and normal patterns of lung function in controls and flour mill workers.
The present study revealed the prevalence of respiratory symptoms of dry cough (27.7% vs. 9.3%), productive cough (11.1% vs. 5.6%), wheeze (14.8% vs. 3.7%), and breathlessness (16.6% vs. 7.4%) in flour mill workers and controls, respectively. In this study, the higher prevalence of respiratory symptoms in flour mill workers may be due to prolonged exposure of flour dust, unhygienic conditions, and poorly ventilated workplaces of the study areas as compared to the controls. A study by Wagh and his colleagues on the influence of flour dust on flour mill workers compared to the nonexposed controls found that flour mill workers had three times shortness of breath and developed four times frequent coughing compared to controls [
Similar findings were reported in Egypt [
The present study investigated the prevalence and the type of pulmonary impairment observed among the flour mill workers. We found 27.7% (n=15) of the workers develop restrictive type of lung disorder while 11.1% (n=6) develop obstructive type of lung disease. On the other hand, there were only two control subjects (3.7%) that showed an obstructive type of lung disorder. Hence, the prevalence of obstructive and restrictive lung diseases was higher in exposed group than in control group. The plausible explanation for the increased prevalence of restrictive lung impairment in exposed group is mainly due to flour dust that reacts with lymphoid and connective tissue in the terminal and respiratory bronchioles and interstitial inflammatory cells.
The results of spirometry done by [
The findings of the present study were in line with others [
A study by [
Similar studies conducted in Nigeria [
We found that majority of the workers do not wear any equipment, some workers wear safety shoe, masks, and gloves, and 33.3% wear only masks. Another similar study found that some workers used a mask [
This study failed to estimate the concentration of organic flour dust in the working area and was unable to determine subclinical cardiopulmonary and other systemic diseases that may affect the result of the study in both cases and controls.
Percentage prevalence of respiratory symptoms was higher among exposed workers as compared to control groups and the difference was more vivid for dry cough. Flour mill workers showed significantly reduced values in the pulmonary function tests (FVC, FEV1, FEV1 /FVC, PEFR, and FEF25%
American Thoracic Society
British Medical Research Council Questionnaire
Body mass index
Forced vital capacity
Forced expiratory volume in one second
Percentage of the FVC
Forced expiratory flow rate at the middle part of FVC
National Institute of Occupational Safety and Health
Occupational asthma disease
Personal protective equipment
Pulmonary function tests
Peak expiratory flow rate
Statistical Package for Social Science.
The data used to support the findings of this study are available from the corresponding author upon request.
The authors declare no conflicts of interest.
Dessalegn Demeke designed the study, conducted field work, analyzed data, interpreted findings, and wrote the manuscript. Dr.Diresibachew W. Haile supervised the development of proposal, data analysis, manuscript writing, and procedure of spirometric measurement. All authors read the manuscript and agreed to its content.
We kindly thank the flour mill workers and data collectors heartfully.