1. Center for Environmental Medicine, Asthma and Lung Biology, School of Medicine, University of North Carolina at Chapel Hill, North Carolina, U.S. EPA, ORD, National Exposure Research Laboratories, RTP, North Carolina, U.S. EPA, ORD, National Health and Environmental Effects Research Laboratories, RTP, North Carolina, North Carolina State Highway Patrol, and Division of Cardiology, School of Medicine, University of North Carolina at Chapel Hill, North Carolina