Merrill Eisenbud is the author of more than 200 contributions to scientific journals and books. He is currently Professor Emeritus at the Nelson Institute of Environmental Medicine, New York University Medical Center, where he spent 25 years as professor and director of the Laboratory of Environmental Studies. Dr. Eisenbud has served with the U.S. Atomic Energy commission (where he was the founding director of the Health and Safety Laboratory), the National Academy of Engineering, New York Academy of Sciences, the Brazilian Academy of Sciences, the New York Academy of Medicine, and as Environmental Protection Administrator for the City of New York. He has been a member of many national and international committees concerned with radiation research and is currently an Honorary Member of the National Council on Radiation Protection and Measurements, and a member of the National Research Council Boardon Radiation Effects. Dr. Eisenbud is currently Scholar in Residence at the Duke University Medical center, and is adjunct professor of Environmental Sciences and Engineering at the University of North Carolina School of Public Health. Tom Gesell is a member of the Health Physics Society and the National Council on Radiation Protection and Measurements, and serves on federal advisory committees and is a consultant to the International Atomic Energy Agency. He has made close to 100 contributions to the scientific literature and has edited compendia on natural radiation and on contamination from nuclear weapons testing. Dr. Gesell has directed the Department of Energy's Radiological and Environmental Sciences Laboratory located on the Idaho National Engineering Laboratory site where he managed numerous programs related to protection health and environment. Since 1991 Gesell has been a professor of health physics at Idaho State University where he also directs the ISU Environmental Monitoring Program and serves as University Radiation Safety Officer.