ACKNOWLEDGMENTS The authors fully appreciate the fine efforts of Nathanial A. Greenhouse of Lawrence Berkeley Laboratory, Lee V. Kaplan, a student from Yale University, Dr. Fred Brauer of Battelle Pacific Northwest Laboratory, Kendall Peterson of Lawrence Livermore National Laboratory, Dr. Charles Sondhaus of the University of California, Dr. John Baum, Dr. Victor Bond, M.D., Donald Borg, M.D., Robert Conard, M.D., Eugene Cronkite, M.D., Andrew Hull, and Charles Meinhold all from Brookhaven National Laboratory and Dr. Bruce Wachholz from Department of Energy Headquarters in helping to prepare a scientific document. We gratefully acknowl- edge their contributions of ideas and procedures. We are also grateful to a number of colleagues who have read the manuscript for this report and offered valuable comments: William Adams, M.D. of Brookhaven National Laboratory, Dr. William Bair and Dr. Richard Gilbert of Battelle Pacific Northwest Laboratory, Dr. Roger McClellan of Lovelace Inhalation Toxicology Research Institute, and Dr. Jack Healy of Los Alamos National Laboratory.