1. National Exposure Research Laboratory, USEPA, Research Triangle Park, North Carolina 27713, United States
2. Centers for Disease Control and Prevention, Atlanta, Georgia 30341, United States
3. Battelle, Columbus, Ohio 43201, United States
4. Battelle, Durham, North Carolina 27713, United States
5. Office of Pesticide Programs, USEPA, Washington, D.C. 20460, United States