Silicosis in kaolin workers and firebrick makers

Nine patients with disabling pneumoconiosis were selected over a three-year period for study because of a work history of kaolin exposure. All had worked in the Missouri firebrick industry. Chest roentgenograms from all nine and lung tissue from two were consistent with silicosis. Worksite analysis of airborne dust at several Missouri firebrick factories revealed that some current workers are exposed to both free silica (up to 4.5%) and cristobalite (up to 8.9%) at levels exceeding the threshold limit value (TLV). Analysis of airborne dust from several kaolin processing plants in South Carolina and Georgia revealed that a few workers are exposed to about 1% free silica at levels occasionally exceeding the TVL. We conclude that silicosis is a serious risk for Missouri kaolin workers and a potential risk for workers in South Carolina and Georgia. A prevalence survey is needed in Missouri to assess the problem.