Personal Dust Exposure and Its Determinants among Workers in Primary Coffee Processing in Ethiopia.

Background: Coffee processing has been shown to cause high dust exposure among the workers, but there are few studies from primary processing of coffee, and none of them is from Ethiopia. The aim of this study was to assess dust exposure and its determinants among workers in primary coffee processing factories of Ethiopia. Methods: A total of 360 personal 'total' dust samples were collected from the breathing zone of workers in 12 primary coffee processing factories in Ethiopia. Dust sampling was performed with 25-mm three piece conductive cassettes with cellulose acetate filters attached to pumps with flow rate of 2 l min-1 for an average sampling duration of 410 min. The dust samples were analysed gravimetrically using a standard microbalance scale. An observational checklist was used to collect information about possible determinants of dust exposure in the work environment. Linear mixed effect regression models were used to identify significant determinants of total dust exposure. Results: Personal total dust exposure levels varied between the three main job groups with a geometric mean (GM) of 12.54 mg m-3 for the machine room workers, 12.30 mg m-3 for the transport workers, and 1.08 mg m-3 for hand pickers. In these three groups, 84.6%, 84.1% and 2.6% of the samples exceeded the occupational exposure limit for organic total dust of 5 mg m-3, respectively. The mixed-effects model for the machine room workers explained 21% of the total variance in total dust exposure, and showed that vigorously pouring coffee from a dropping height was associated with an about two times increase in exposure. For the transport workers, the mixed-effects model that included pouring method of coffee beans, number of huller machine in the room, mixing coffee, and feeding hopper explained 32% of total variance in personal total dust exposure. 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. Proper control measures are necessary to reduce the exposure.