Pulmonary function loss in Vermont granite workers. A long-term follow-up and critical reappraisal.

Previous studies of Vermont granite workers averred that pulmonary function loss was occurring at 2 to 3 times the normal rate. The excess loss was attributed to the current, relatively low concentrations of dust prevailing in the stone sheds. Because the Vermont State Health Department had traditionally provided surveillance of granite workers to detect evidence of occupationally related illness, we offered pulmonary function screening to any currently employed worker. Spirometric data from the first 150 workers, compared with data from the previous studies, showed a large increase in the FVC and a smaller increase in the FEV1. We therefore undertook a survey of the entire stone shed work force, as well as of retired workers tested previously. The results in 487 current workers indicated an overall increase in FVC from 1974 to 1979 of 0.540 L, and an increase in FEV1 of 0.030 L: predicted losses based on the previous studies were 0.350 to 0.400 L in FVC and 0.250 to 0.350 L in the FEV1. Analysis of data in various subgroups, such as retired workers or those with more than 20 yr of work experience, also showed increases in FVC, and either slight gains or minimal losses in FEV1. The possible reasons for apparent improvement in pulmonary function are discussed. We concluded that technical deficiencies in the previous studies led to exaggerated and erroneous estimates of loss. At this time, the actual decrement in pulmonary function values for exposed granite workers is not known and requires further investigation. Because the newly proposed, stricter standard, for silica was importantly influenced by the previous studies, we believe that adoption of this standard would be premature.