Silicosis among gemstone workers in South Africa: tiger's-eye pneumoconiosis.

Six cases of silicosis in workers involved in the processing of semiprecious gem stones have been seen in our clinic since 1976. They had been employed as stone sculptors in lapidaries where they processed tiger's-eye, rose quartz, amethyst, quartz crystal, and a variety of other locally occurring semiprecious 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 was conducted in one of two lapidaries still operating in our area. Progressive massive fibrosis (PMF) or accelerated silicosis was noted in four of the six 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 three cases. 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.