A respiratory epidemiologic survey of grain mill workers in Cape Town, South Africa

Exposure to grain dust may induce acute and chronic respiratory, nasal, and ocular symptoms. The prevalence of respiratory symptoms, atopic status, and lung function changes, as measured by pulmonary function tests (PFT) over the week in 582 grain mill workers and 153 control subjects not exposed to grain dust were studied in Cape Town. Atopic status, smoking habits, and baseline PFT did not differ significantly between grain workers and control subjects. Grain workers showed significant deterioration in lung function values over the week, with forced expiratory volume in one second declining on average by 4.8% compared with an increase of 3.3% in control subjects (p less than 0.001). Forced expiratory flow during the middle half of the forced vital capacity declined by 14.8% in grain workers and by 0.8% in control subjects (p less than 0.0001). Grain workers had significantly higher prevalences than did control subjects of regular cough (46 versus 30%), expectoration (35 versus 17%), wheeze (25 versus 11%), and watery eyes (25 versus 10%) (p less than 0.01 for all). These symptoms were not related to the duration of employment. A dose-response relationship, independent of smoking habits, was demonstrated between reported dust exposure and symptoms as well as between dust exposure and PFT. These results have important implications for the grain mill industry in South Africa where there is insufficient legislation and worker compensation.