Coffee dust exposure and respiratory health among workers in primary coffee processing factories in Ethiopia

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Addis Abeba University


Background: Dust exposure is one of the major risk factors for health in many work places including coffee processing factories. Dust generates at different stages of coffee handling and processing. Excessive exposure to coffee dust can cause respiratory health problems. Coffee workers in Ethiopia are exposed to coffee dust, but the level of exposure and the magnitude of its health effect have not been widely investigated. Objectives: The aims of this study were to assess the level of personal total dust exposure, factors affecting dust exposure, the prevalence of respiratory symptoms and lung function reduction among coffee workers. In addition, assessing microbial contamination of coffee at different stages of both wet and dry method on farm coffee processing was a part of this dissertation. Methods: Comparative cross-sectional studies were conducted in primary coffee processing factories involving 3 regions: Oromia Regional State; Addis Ababa City Administration; and Southern Nations, Nationalities and Peoples’ Region. The study also included a comparative population in 3 water bottling factories, one from each region mentioned above. A total of 360 dust samples were collected from 12 primary coffee processing factories for dust exposure assessment. In addition, 60 total dust samples were collected from the 3 water bottling factories. Dust samplings were collected from breathing zone of workers using 25mm three piece, closed-faced conductive cassettes with a cellulose acetate filter attached to Side Kick Casella pumps with a flow rate of 2 liter/ minute. Observational checklist was used to identify possible determinants for dust exposure. Lung function tests were performed for a total of 420 participants ( 120 male coffee workers, 120 male controls, 60 hand pickers with tables, 60 hand pickers without tables and 60 female controls) using a portable spirometer (SPIRARE 3 sensor model SPS 320). Lung function parameters such as Forced Vital Capacity (FVC), Forced Expiratory Volume in one second (FEV 1 ), the mean forced expiratory flow between 25% and 75% of the FVC (FEF ) and ratio FEV FVC were measured. Prevalence of chronic respiratory symptoms were assessed with an interview, using a standardized questionnaire adopted from the American Thoracic Society. 1/ Coffee cherries each weighing about 25 grams were sampled from each stage of the wet and dry processes for microbial contamination assessment. Standard Plate Count agar was used 25-75% to grow total bacteria and gram stain technique were used to identify gram negative and gram positive bacteria. Data were entered into an electronic database using EpiData version 3.1 and exported to SPSS version 22 for analysis. Missing values and outliers were checked using frequency tabulation, and then were managed accordingly. The results were described as arithmetic mean, standard deviation, geometric mean (GM), and geometric standard deviation (GSD). A one-way analysis of variance was performed to compare the GM of personal total dust exposure level between different job groups and between tasks. Linear mixed effect regression models were developed to identify significant determinants for personal total dust exposure. Independent t-tests were used to compare the mean values for the continuous variables. The Pearson Chi-square test or Fisher’s exact test, if the expected value was less than 5, were used to test the difference between the groups regarding the categorical variables. Poisson regression analysis with a robust variance was used to determine the prevalence ratio of the different respiratory symptoms between the coffee workers and controls. Analysis of covariance and linear regression were used to compare the mean lung function parameters between the coffee workers and controls while adjusting for confounders. Results: The GM dust exposure among machine room workers ranged from 4.09 to 34.40 mg/m 3 , among transport workers from 3.51 to 24.19 mg/m 3 , and among hand pickers from 0.26 to 5.87 mg/m 3 . Overall the GM personal dust exposure was significantly higher (P = 0.001) for the machine room (12.54 mg/m 3 ) and transport workers (12.30 mg/m ) than for the hand pickers (1.08 mg/m 3 ). In these three groups, 84.6%, 84.1%, and 2.6% of the samples exceeded the occupational exposure limit of 5 mg/m 3 respectively. The result also indicated that pouring coffee vigorously from a dropping height was the determinant with the highest impact on personal total dust exposure with 3.2-fold increase compared to gradually pouring coffee from a very short height. Coffee workers had significantly higher prevalence of most of the chronic respiratory symptoms compared with the controls. For most of the chronic respiratory symptoms, hand pickers without tables displayed a significantly higher prevalence ratio than in hand pickers with tables. 3 Male coffee workers in the age groups 28–39 years and ≥40 years, had a significantly lower FVC and FEV compared to the controls in the similar age groups. There were statistical differences in FEF 1 25-75% between hand pickers and controls. In addition, FVC and FEV were significantly lower among hand pickers without tables than among hand pickers with tables. The results also indicated the presence of gram negative bacteria in dried and stored beans from both the wet and dry process. Conclusion: About 84% of the dust samples among machine room and transport workers in primary coffee processing factories were above the occupational exposure limit value for organic dust. Machine and transport workers in primary coffee processing factories had a higher prevalence of chronic respiratory symptoms and lower FVC and FEV than the controls. Pouring coffee beans vigorously from a dropping height, mixing coffee and feeding hopper were the main determinants for increased personal dust exposure level. The dust exposure was related to reduced lung function and higher prevalence of chronic respiratory symptoms among coffee workers. Gram negative bacteria found in dried and stored coffee beans, might release endotoxin which may cause respiratory health problems among coffee production workers. Recommendations: Coffee workers should be provided with efficient respiratory protective device and training on its importance prior to employment and regularly afterwards as necessary. Changing process of pouring coffee beans from vigorously to gradual could reduce personal dust exposure level in the coffee factories. 1 1



Coffee dust exposure , respiratory health , coffee processing factories in Ethiopia