NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance.

Support for this study was provided by the National Research Council, the U.S. Department of Energy (DE-AT-01-EE41424, BES DE-FG-02-00ER15040, and DE-AT01-03ER15386), the National Science Foundation (CTS-9908440), the Defense Advanced Research Projects Agency (DOD MDA972-01-M-0001), the U.S. Environmental Protection Agency (R82823301), the American Chemical Society, the American Institute of Chemical Engineers, the Camille and henry Dryfus Foundation (SG00-093), the National Institute of Standards and Technology (NA1341-01-2-1070 and 43NANB010995), the National Institutes of Health (NCI-N01-OD-4-2139 and NIGMS-N01-OD-4-2139), and the chemical industry.

All opinions, findings, conclusions, or recommendations expressed herein are those of the authors and do not necessarily reflect the views of the organizations or agencies that provided support for this project.

Library of Congress Control Number: 2003100913