advisory boards for several government agencies, including the National Toxicology Program and EPA. Dr. Ryan has served on several previous NRC study committees. She received her Ph.D. from Harvard University.

Michael L. Stein is a professor of statistics at the University of Chicago and director of the Center for Integrating Statistical and Environmental Science. His research interests focus on statistical models and methods for spatial and spatial-temporal processes. He is interested in the nature of the spatial-temporal interactions implied by these models and on developing statistical methods for assessing these interactions. Dr. Stein received his B.S. in mathematics from the Massachusetts Institute of Technology and his M.S. and Ph.D. in statistics from Stanford University.

Wendy E. Wagner is a professor of law at the University of Texas at Austin. Before entering teaching, she practiced for 4 years, first as an honors attorney in the Enforcement Division of the U.S. Department of Justice's Environment and Natural Resources Division and then as pollution control coordinator in the U.S. Department of Agriculture Office of the General Counsel. Professor Wagner received her M.S. in environmental studies and her law degree from Yale University. She currently serves as an officer in the Society for Risk Analysis and the American Bar Association's Administrative Law Section and is a Member Scholar of the Center for Progressive Regulation.