1. Center for Environmental Medicine, Asthma, and Lung Biology, School of Medicine, University of North Carolina at Chapel Hill, North Carolina, USA
2. National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, USA
3. Department of Biostatistics, School of Public Health, University of North Carolina at Chapel Hill, North Carolina, USA
4. National Exposure Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, USA
5. Division of Cardiology, Brody School of Medicine, East Carolina University, Greenville, North Carolina, USA