Silicosis among Cape gemstone workers : tigers' eye pneumoconiosis

Silicosis continues to be an important occupational disease in South Africa, particularly in small, poorly regulated industries. A case series is described of six workers who developed silicosis whilst involved in the processing of semi-precious gem stones. They had been employed as stone sculptors in lapidaries where they processed tigers' eye, rose quartz, amethyst, quartz crystal and a variety of other locally occurring semi-precious stones. In five of the cases exposure was in small and poorly regulated lapidaries without specific dust control measures. The sixth was detected during the course of a health and hygiene survey (including dust sampling) that I conducted in one of two lapidaries still operating in the Western Cape. These workers developed serious disease. Progressive massive fibrosis (PMF) was noted in 4 of the 6 cases, three of whom had progression of their disease after cessation of exposure. With the development of PMF the initial restrictive pulmonary function abnormalities were followed by steadily worsening airflow obstruction. Lung biopsies confirmed silicosis in one case and were suggestive in a further two. Tuberculosis was confirmed in two cases and suspected and treated in a third. Workmen's' Compensation was awarded in five cases. The survey confirmed that in semiprecious gem stone processing, the risk of silicosis appears to be confined to stone sculptors. Tried and proven techniques of general and local exhaust ventilation combined with water or oil to control dust at source were capable of effectively reducing dust emission to acceptable levels.