Abstract
Following several reported cases of silicosis in the slate industry of Pennsylvania, surveys were conducted by the Pennsylvania Department of Health between 1963 and 1965. Based on the results of these surveys, recommendations were made to reduce dust exposures to safe levels at certain operations. During the summer of 1969, the quarries and processing plants of 10 companies having a combined population of 437 employees were re-evaluated to determine the effectiveness of improvements made in accordance with recommendations from the previous surveys. In general, exposures had been reduced to less than the pertinent threshold limit values. An explanation of how these exposure reductions were achieved is given. A comparison between the analytical methods and findings in 1969 with those of the earlier surveys is also made.