1. Departments ofAnesthesiology and
2. Medicine, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill 27599-7010; Center for Environmental Medicine and Lung Biology, University of North Carolina at Chapel Hill, Chapel Hill 27599-7310;
3. Clinical Research Branch, Human Studies Division, National Health and Environmental Effects Research Laboratory and
4. National Center for Environment Assessment, US Environmental Protection Agency, Research Triangle Park 27711; and
5. Department of Biostatistics, School of Public Health, University of North Carolina, Chapel Hill, North Carolina 27599-7400