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 competencies and with regard for appropriate balance.

This report has been reviewed by a group other than the authors according to procedures approved by a Report Review Committee consisting of members of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine.

Support for this study was provided by the Department of Energy and the Environmental Protection Agency both under subcontract no. C93-160544 and the National Center for Manufacturing Sciences under grant no. 02-170-000-92093.

A limited number of copies of this report are available from the National Academy of Sciences, Board on Environmental Studies and Toxicology, 2101 Constitution Avenue, N.W., Washington, DC 20418.