Relative chronic effects of different occupational dusts on respiratory indices and health of workers in three Ethiopian factories.

The respiratory effects of dusts in different sections of yarn, cement, and cigarette factories were studied in 211 nonsmoking male and female workers aged 21-57 years. The controls used were 211 healthy nonsmoking and nonexposed male and female subjects aged 20-57 years from the general population. Forced vital capacity (FVC), forced expiratory volume in 1 sec (FEV1), FEV1/FVC ratio, forced expiratory flow (FEF200-1,200 ml), forced mid-expiratory flow (FMF25-75%) and peak expiratory flow rate (PEFR) were recorded in all subjects with and without respiratory symptoms. Taking exposures to all dusts of different concentrations together, it was found that the frequency of respiratory illness was greater among exposed workers (40.5% in males, 36% in females) than it was among controls (21.6% in males, 18% in females). In exposed subjects, the symptom prevalence was only 4.5% higher in males than in females. The mean lung function indices, including FEV1, FEV1%, FEF200-1,200 ml, FMF25-75%, and PEFR, in subjects exposed to all dusts in general decreased markedly, with dust concentration being more important than duration of exposure, and FMF being affected slightly more consistently. About 38.4% of the dust-exposed subjects developed corresponding respiratory illnesses including chronic cough (24.7%), chronic bronchitis (21.8%) and bronchial asthma (24.2%). The respective control values were 9.0%, 9.5%, and 8.5%. Exposure to different occupational dusts resulted in the development of respiratory illness with different rates of prevalence. The effects of exposure to cotton and cement dusts on respiratory health of exposed subjects were relatively more significant (p < 0.001) than that of exposure to tobacco dust (p < 0.05).