Work Environment and Respiratory Health among Sisal Processors in Tanzania : Studies in six sisal factories
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Background: Very little is known about work and health in the sisal industry. Previous studies on sisal are old and mainly focused on sisal fibre textiles and rope factories. Stationary dust concentration rather than personal exposures has been measured in a few studies but not bio-aerosols content of sisal dust. Globally, Tanzania occupies a third place in annual sisal export. Production methods in Tanzanian sisal factories are still labour intensive, implying that many workers are currently employed in the country’s 82 sisal estates. Yet very little is known about work-related health risks among sisal workers in Tanzania. Methods: Six sisal processing factories were selected for the study. Walkthrough surveys were conducted in the decortication and brushing departments and all 165 sisal processing workers (exposed) in these departments (including 93 decorticators, 72 brushing) and 32 randomly selected security guards (low exposed) were invited to participate in the study. Daily interviews on acute respiratory symptoms arising during or after work, and assessment of peak expiratory flow rates before and after work shifts were performed from Monday to Friday. All sisal workers and security guards were also interviewed for chronic respiratory symptoms. Thirty-eight randomly selected sisal workers were involved to collect personal dust samples using 30 cellulose acetate and 48 polycarbonate filters for gravimetric dust analysis and for bacteria and fungi spore counting, respectively. Furthermore, 138 out of 165 sisal processing workers and 78 conveniently sampled urban-based control participants were skin prick tested with dry and fresh sisal extracts. Serum samples from a subset of 43 skin pricked participants were tested for total and sisal specific IgE, PhadiatopTM, and ELISA. A fresh sisal extract was examined by SDS PAGE (electrophoresis method) to look for sisal allergen proteins. Results: Walkthrough surveys indicated generally poor working conditions in five of the six sisal factories, with workplaces characterized by wet floors, visible dust emissions, long stressful work shifts, monotonous tasks at awkward postures and heavy manual lifting. Use of personal protective equipment and other general occupational health and safety services was almost absent. Old brushing and decortication machinery from as early as the 1890s was still in use. The arithmetic mean exposure of all sisal processors was 1.18 mg thoracic dust/m3, 43x106 bacteria /m3, and 2.35 x 106 fungal spores/m3 . The highest mean thoracic dust (2.06 mg/m3), bacteria spores (230 x 106/m3) as well as fungal spores (15.10 x 106/m3) were measured when cleaning corona drums at the decortication. Personal exposure measurements showed significant differences in thoracic dust levels and bacteria exposures between work departments and workers tasks. Positive correlations were found between fungal and bacteria counts (r = 0.47; p = 0.01; n = 32), but no significant differences were detected among the study groups for fungal exposure. Mixed effect models including the brushing and decortication departments explained 64.7% of the thoracic dust exposure variance between workers. The models also showed that working in the brushing department was a significant exposure determinant (p = 0.04) After the first day of work (Monday), and when compared to security guards, odds ratios for sisal processing workers were for sneezing 4.2 (95%CI; 1.6–11.1) and for dry cough 2.9 (95%CI; 1.3–5.4) after adjusting for age, smoking and past respiratory illnesses. Compared to decortication workers, brushing workers had significantly higher odds ratio for sneezing; 3.2 (95%CI; 1.6–6.2) and stuffy nose 3.1 (95%CI; 1.4–7.0). With the exception of shortness of breath and wheezing, brushing workers had significantly higher prevalence for all acute respiratory symptoms than decortication workers. During the five days of follow-up, brushing workers showed significantly higher severity scores and prevalences for most acute respiratory symptom than security guards and decorticators. Compared to security guards, workers in decortication had significantly higher prevalence of shortness of breath. A significantly decreasing trend across the week was found for the prevalence of shortness of breath among brushing workers (from 39% to 20%: P <0.01). During the study week, brushing workers had consistently lower pre- and post-shift PEF values than decortication workers and security guards. Brushing workers reported the highest prevalence of all chronic respiratory symptoms, and compared to security guards they had a significantly higher prevalence of chest tightness (48% versus 3%) and chronic sputum (30% versus 3%). Decortication workers and security guards differed significantly for chest tightness (30% versus 3%). Brushing and decortication workers differed significantly with regards to the prevalence of chronic sputum and chest tightness. Sensitization to either fresh sisal sap or dry sisal extract was 74% in decortication and 71% in brushing, compared to 17% among urban-based control participants. The prevalence of elevated sisal-specific IgE was about 27% among the 43 tested individuals. Age- and smoking-adjusted relative risk for sensitization to sisal was higher for sisal workers than for control participants (RR 4.0; 95% CI; 2.4–6.7). Comparing sensitized and non-sensitized workers, prevalences of respiratory symptoms were not significantly different. All exposed workers and all but one control participant had elevated (>100kU/L) IgE levels. Analysis of the sisal extract showed two IgE binding protein bands at 45 kDa. Discussion and conclusion: The combined effect of poor working conditions, use of old machinery and lack of protective clothing implies increased health risks due to possible exposures to sisal dust and bio-aerosols among sisal processing workers. Sisal processing workers had significantly higher severity scores and prevalence of respiratory symptoms, and were more sensitized to sisal than controls, indicating a possible association with exposure arising within the sisal fibre processing areas. Dust and bio-aerosol exposure levels appear to be higher for some tasks, emphasizing the need to consider differences in workers tasks when assessing workplace exposures and when planning control measures. Preventive action and more studies are recommended in this industry.
Paper I: Journal of Occupational and Environmental Hygiene 6(3), Kayumba, Akwilina V.; Bråtveit, Magne; Mashalla, Yohana; Baste, Valborg; Eduard, Wijnand; Moen, Bente E., Working Conditions and Exposure to Dust and Bioaerosols in Sisal Processing Factories in Tanzania, pp. 165 -173. Draft version. Copyright 2009 Taylor & Francis. Full text not available in BORA due to publisher restrictions. The published version is available at: http://dx.doi.org/10.1080/15459620802683044Paper II: Occupational Medicine 57(4), Kayumba, Akwilina V.; Bråtveit, Magne; Mashalla, Yohana and Bente E. Moen, Acute respiratory symptoms among sisal workers in Tanzania, pp. 290-293. Copyright 2007 The Authors. Published by Oxford University Press. Full text not available in BORA due to publisher restrictions. The published version is available at: http://dx.doi.org/10.1093/occmed/kqm004Paper III: Archives of Environmental & Occupational Health 63(2), Kayumba, Akwilina Victor; Bråtveit, Magne; Mashalla, Yohana James; Baste, Valborg; Moen, Bente Elisabeth, Prevalence of Respiratory Symptoms Among Sisal Processors in Tanzania, pp. 76-86. Copyright © 2008 Heldref Publications. Full text not available in BORA due to publisher restrictions. The published version is available at: http://dx.doi.org/10.3200/AEOH.63.2.76-86Paper IV: Annals of Agricultural and Environmental Medicine 15, Kayumba, Akwilina V.; Van-Do, Thien; Florvaag, Erik; Bråtveit, Magne; Baste, Valborg; Mashalla, Yohana; Eduard, Wijnand and Bente E. Moen, High prevalence of immunoglobulin E (IgE) sensitization among sisal (Agave sisalana) processing workers in Tanzania, pp. 263-270. Draft version. Copyright AAEM. Reproduced with permission. The article is available online in www. AAEM.