1. Office of Research and Development, United States Environmental Protection Agency, Research Triangle Park, Durham, North Carolina 27711, United States
2. SRC, Inc., North Syracuse, New York 13212, United States
3. Office of Research and Development, United States Environmental Protection Agency, Cincinnati, Ohio 45224, United States
4. Pharmacokinetics Branch, Integrated Systems Toxicology Division, National Health and Environmental Effects Laboratory, ORD, US EPA, RTP, NC, Durham, North Carolina 27709, United States