1. Oregon Graduate Institute of Science and Technology, P.O. Box 91000, Portland, Oregon 97291, National Exposure Research Laboratory, U.S. Environmental Protection Agency, MD-47, Research Triangle Park, North Carolina 27711, ManTech Environmental Technology, Inc., P.O. Box 12313, Research Triangle Park, North Carolina 27709, and Texas Natural Resources Conservation Commission, P.O. Box 13087, Austin, Texas 78711