Reconstruction of Silica Exposure at a Foundry for Evaluation of Exposure-Response

The reconstruction of working lifetime exposures to silica at a large foundry was described. Through the use of interviews with long-term employees, a history of the facility was developed for the years 1960–90, areas of similar work activities were identified and work locations for those with various job titles were documented over time. Two thousand and seventy historical industrial hygiene measurements of exposure collected during these three decades were linked to work area and an estimate of average respirable silica concentration was calculated for each area, by year. Overall, exposures declined between 1960 and 1990; however, substantial differences in exposure were estimated across work areas. Exposure at a specific job was calculated from the estimates of work-area respirable silica concentration, weighted by the amount of time persons with that job were in the area. These job-related exposure estimates were used to calculate three exposure metrics for persons employed in the foundry: cumulative, working lifetime average and highest daily exposure.