Willy Aspinall is a consulting scientist at Aspinall and Associates, which he has led since 1989. He is also a visiting industrial professor at the University of Bristol in England. His principal professional interests are volcanology and seismology, the probabilistic assessment of hazards and risks, and the formalized use of expert judgment in decision-making for low probability/high consequence events in circumstances of uncertainty. He is currently advising the British government about the ongoing volcanic eruption on Montserrat in the West Indies. He also sits on scientific advisory panels concerned with research into the effects of biological agents on humans and the control of SARS and avian flu in healthcare workers. He holds a Ph.D. in physics from University of Durham in the United Kingdom.

Roger Cooke joined RFF in September 2005 as the first appointee to the Chauncey Starr Chair in Risk Analysis. He is recognized as one of the world's leading authorities on mathematical modeling of risk and uncertainty. His recent research has encompassed health risks from oil fires in Kuwait following the first Gulf War, chemical weapons disposal, nuclear risk, nitrogen oxide emissions, and microbiological risk. His current research interests include structured expert-judgment methodologies and uncertainty analysis. He also holds an appointment as professor of applied decision theory at the Department of Mathematics at Delft University of Technology in The Netherlands, where he has worked for more than 25 years. He received a Ph.D. in philosophy and mathematics from Yale University.

John Evans is a senior lecturer on environmental science at the Harvard School of Public Health, where he directs the Kuwait Public Health Project, an effort to estimate the health impacts of Iraq's 1990 invasion of Kuwait. He has served on the Harvard faculty since 1986. His research has concentrated on characterizing uncertainty in estimates of the health impacts of environmental exposure to chemicals, radiation, and particulate matter and on the use of expert judgment and value of information analysis in support of environmental decisions. He is a charter member and fellow of the Society for Risk Analysis. He holds a Sc.D. in environmental health sciences from Harvard University.

George Gray was sworn in to serve as the assistant administrator for EPA's Office of Research and Development on November 1, 2005. He was appointed to this position by President George W. Bush and confirmed-by unanimous consent-by the U.S. Senate. Prior to joining EPA, he was executive director of the Harvard Center for Risk Analysis and a lecturer in risk analysis at the Harvard School of Public Health. During 16 years at Harvard, his research focused on the scientific bases of human health risk assessment and its application to risk policy with a focus on risk/risk tradeoffs in risk management. He has taught toxicology and risk assessment to both graduate students and participants in the school's Continuing Professional Education program. He has a Ph.D. in toxicology from the University of Rochester.

Bob Hetes is the senior advisor for regulatory support at EPA's National Health and Environmental Effects Research Laboratory, where he is responsible for ensuring that science informs agency actions. He is currently serving as co-chair of an EPA Intra-Agency Task Force on the Conduct and Use of Expert Elicitation, and as the health effects lead for the Risk Assessment Forum's Probabilistic Risk Assessment Workgroup. Previously, he served as a senior scientist and technical authority on risk assessment in EPA's Office of Air Quality Planning and Standards Risk Exposure Assessment Group. Before joining EPA in 1997, he spent more than 15 years as an environmental consultant. He received an M.S.P.H. in environmental sciences from University of North Carolina in Chapel Hill.

Alan Krupnick is a senior fellow and director of the Quality of the Environment Division at RFF, where he has worked for more than 25 years. He is an expert on cost-benefit analysis, the valuation of non-market goods and activities, survey techniques, and policy issues associated with the Clean Air Act. He has been a consultant to state governments, federal agencies, private corporations, the Canadian government, the European Union, the World Health Organization, the Asian Development Bank, and the World Bank. He has served as a senior economist at the Council of Economic Advisers during the Clinton Administration. He holds a Ph.D. in economics from University of Maryland.

M. Granger Morgan is a professor and head of the Department of Engineering and Public Policy at Carnegie Mellon University, where he is also University and Lord Chair Professor in Engineering. During his more than 30 years at Carnegie Mellon, much of his research has involved the development and demonstration of methods to characterize and treat uncertainty in quantitative risk and policy analysis. At Carnegie Mellon, he directs the new National Science Foundation Climate Decision Making Center and co-directs the Electricity Industry Center. He chairs the EPA Science Advisory Board, the Electric Power Research Institute Advisory Council, and the Scientific and Technical Council for the International Risk Governance Council (based in Geneva, Switzerland). He earned a Ph.D. in applied physics and information science from University of California, San Diego.

Kate Probst is a senior fellow and director of the Risk, Resource, and Environmental Management Division at RFF, where she has worked since 1990. She is an expert on Superfund and other hazardous waste management programs, with particular emphasis on cost and implementation. She was the lead author of Superfund's Future: What Will It Cost?, a report requested by Congress that assessed the cost of the Superfund program to EPA for fiscal years 2000 through 2009. She has been asked to be a member of the National Research Council's Committee on Sediment Dredging at Superfund Megasites and was a member of a recent EPA Science Advisory Board panel that evaluated an analysis of the benefits of the Superfund program. Before joining RFF, she worked at EPA, the New York City Department of Environmental Protection, and the Environmental and Energy Study Institute. She received an M.A. in city and regional planning from Harvard University.

Phil Sharp is president of Resources for the Future (RFF). His career in public service over the last 35 years includes 10 terms as a member of the U.S. House of Representatives from Indiana and a lengthy tenure on the faculty of the John F. Kennedy School of Government and the Institute of Politics (IOP) at Harvard University. He served as director of IOP from 1995 to 1998 and again from 2004 until August 2005. Sharp is co-chair of the Energy Board of the Keystone Center and a member of the National Research Council's Board of Energy and Environmental Systems. He serves on the boards of directors of the Energy Foundation, the Cinergy Corporation, and the Electric Power Research Institute. He holds a Ph.D. in government from Georgetown University.

Katherine D. Walker is an environmental health scientist with 20 years of experience in public health risk assessment and its application to the regulatory process. She specializes in the analysis of uncertainty in human exposures and health risks. Her most recent work has focused on the use and calibration of expert subjective judgments to characterize uncertainty. For EPA, she has elicited expert judgments for a pilot study of uncertainty in the concentration response relationship between PM2.5 and mortality and is currently beginning elicitations for the full-scale study. As part of this work, she is a consultant to Industrial Economics, Inc. She holds a Sc.D. in environmental health sciences from the Harvard University.