Abstract

Respiratory symptoms of chronic bronchitis and measurements of lung function were studied in an epidemiological survey of the total population of workers currently employed in granite quarries in Singapore. There were 85 rock drilling and crushing workers with current exposure in high levels of silica dust. Their respiratory parameters were studied with reference to an internal comparison group of 154 quarry maintenance and transport workers with low dust exposure, and an external comparison group of 148 Telecoms postal delivery workers with no granite dust exposure. The highly exposed workers showed greater prevalences of chronic cough and phlegm, a mean reduction of 5% in forced expiratory volume in one second (FEV1) and forced vital capacity (FVC). The increased respiratory morbidity were independent of other factors such as age and smoking. Similar results were also noted after excluding those with silicosis (defined radiologically as profusion greater than 1/1 as read by at least two of three readers). This study strongly indicates a demonstrable risk of "occupational" bronchitis (mucus hypersecretion) and obstructive and restrictive lung function impairment, apart from the "classical" risk of silicosis. Measures taken to protect the health of workers exposed to silica dust should also be based on considerations taken to protect against the risk of these respiratory disorders as well

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