ABSTRACT Byssinosis and other respiratory symptoms and acute and chronic changes in FVC and FEV1·0 were investigated in 77 workers in sisal spinning and 83 workers in sisal brushing departments in six Tanzanian sisal factories. Although the prevalence of byssinosis in spinning departments was found to be low (5·2%), it was very high in brushing departments (48·2%). Workers in brushing were exposed to sisal dust for a significantly longer period (11·77 ± 7·3 years) compared to workers exposed to sisal in spinning (2·85 ± 2·56 years). Although the number of smokers in brushing (42%) was similar to that in spinning (37%), smokers were more prone to byssinosis than were non- or ex-smokers after standardisation for duration of exposure. We were unable to measure dust levels in this study, but dust levels in spinning and brushing are cited from previous studies. These confirm our impression that the dust level in spinning is higher than that in an average cotton carding department and far higher in brushing than in spinning. Acute falls in FVC and FEV1·0 were found during the work shift. The extent of the fall in FEV1·0 correlated well with the severity of byssinosis; 75% of the workers with grade II byssinosis and 33% of those with grade ½ + I were found to have acute falls in FEV1·0 greater than 0·2 litres. However some workers, 10% in spinning and 33% in brushing, who denied symptoms of byssinosis, were also found to have acute falls in FEV1·0. Some workers had slight or severe chronic ventilatory impairment from dust (FEV1·0 less than 80%, or less than 60% of the respective predicted values), and these workers were mostly from the brushing department. The prevalence of chronic cough and chronic bronchitis was found to be negligible in workers in the spinning and in the brushing departments: 9·6% had a chronic cough and 12% had chronic bronchitis. It is concluded that a high prevalence of byssinosis associated with chronic and acute changes in FVC and FEV1·0 occurs in the brushing departments of sisal factories, and that this is related to lengthy exposure, high dust level and smoking.
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