Tiered exposure-assessment strategy in the Semiconductor Health Study

The Semiconductor Health Study included 14 U.S. companies with 82 silicon-based wafer-fabrication rooms and a complex array of processes and chemicals. Its epidemiologic components were a historical examination of spontaneous abortion rates among 902 women, a prospective evaluation of reproductive outcomes in 483 women, and a cross-sectional review of male fertility and of respiratory, ergonomic, neurologic, or gastrointestinal problems among 3,175 men and women. Designing an exposure assessment strategy presented unique problems, and multiple agents had to be evaluated. A three-tiered approach to exposure assessment was developed to reflect increasing specificity of exposures. At the first tier, employees were divided into fabrication and nonfabrication groups. At the second tier, work groups with qualitatively different exposures were determined. At the third tier, intensity of exposures to specific chemical, physical, and ergonomic agents was evaluated. Evaluations were based on worker reports of tasks performed, moderated by fabrication-specific factors observed by study industrial hygienists during site visits.