More than one million workers are exposed annually to silica in the workplace. Preliminary analyses of the North Carolina Dusty Trades data, a unique resource for exposure-response studies of the effects of silica exposure, indicates that the highest task-related exposure is strongly related to the development of silisosis; however, an exposure of zero was assumed for unsampled tasks in that analysis. This study is being conducted to investigate innovative ways to estimate silica exposure in unsampled tasks. After a more complete literature review, three methods will be selected to impute missing highest task exposure data. Initially, the following approaches are being considered: the mean exposure at sampled commodity-specific tasks, the lower bound of the 95% confidence interval of the median of commodity-specific tasks, and a maximum likelihood estimate. The results from the final three methods will be described and contrasted. Finally an exposure-response analysis will be conducted for the previously identified cases and controls. Any differences in the odds ratios using the highest task exposure metric and the cumulative exposure metric will be tested. If the highest task metric, with imputed values, is found to be related to silicosis development, changes in sampling methods and targeted control techniques could be implemented to decrease disease in the future.
