About the Editors John D. Hamilton earned an M.Sc. degree from McGill University and a Ph.D. in toxicology from the University of Cincinnati. He was a scientific group leader in risk assessment with the Rohm and Haas Company. He is currently managing product safety for the Worldwide Professional Products Division of S.C. Johnson Wax. He is certified in General Toxicology with the American Board of Toxicology. Roger Sutcliffe graduated from University College London, England, with a B.Sc. in chemistry and a Ph.D. in organic chemistry. He worked as a research scientist at the National Research Council of Canada and Forintek Canada prior to joining Environment Canada. Presently, he is an evaluation specialist with the New Substances Division, Commorcial Chemicals Evaluation Branch. In 1990, he was elected a Fellow of the Chemical institute of Canada.