Abstract

In order to study the exposure level of silica dust and the effects of silica dust on ventilatory function, respirable dust samples were collected by personal air samplers using NIOSH method 0500 from the selected foundry operations, and ventilatory function tests were performed on 209 male foundry workers and 239 male control subjects. Ventilatory indices such as forced vital capacity (FVC) , one-second forced expiratory volume (FEV1), ratio of FEV1 to FVC(FEV1 %), maximal mid-expiratory flow(MMF), peak expiratory flow rate (PEFR) and maximal expiratory flow at 25, 50 and 75 % of expired FVC (FEF25, FEF50, FEF75 were obtained by analyzing forced expiratory spirogram and maximal expiratory flow-volume curve which were simultaneously measured by Vitalography in standing position. The results were as follows : 1. The average quartz concentrations of respirable dust were the highest in melting operation (0.079 mg/m3) and followed by molding operation (0.051 mg/m3), finishing operation (0.041 mg/m3) and coremaking operation (0.023 mg/m3) in the descending order. 2. No significant differences for mean values of all ventilatory indices expressed as percent of predicted value were demonstrated between smokers and nonsmokers In foundry workers and control subjects. 3. Mean values of all ventilatory indices except FVC of foundry workers were significantly lower than those of control subjects. 4. Mean values of FEV1 %, MMF, FEF25, FEF50 and FEF75 expressed as percent of predicted value tended to decrease with increasing cumulative dust exposure. 5. In foundry workers, proportions of workers with low MMF, FEF50 and FEF75 were markedly higher than those with other indices, and were significantly increased with increasing cumulative dust exposure. 6. In foundry workers, 2 workers(1.0 %) were diagnosed as silicosis and the profusion of radiographic opacities were category 1/0 and q type. With the above considerations in mind, it suggested that increasing exposure of silica dust be associated with progressive deterioration in ventilatory function of an obstructive nature and that MMF, FEF50 and FEF75 be more sensitive indices in the detection of the early obstructive changes of air flow of workers exposed to silica dust.

• Keywords: Silica dust;Ventilatory function;Foundry worker