1. Environmental Public Health Division, National Health and Environmental Effects Research Laboratory, United States Environmental Protection Agency, Chapel Hill, North Carolina;
2. Department of Environmental Sciences and Engineering, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina;
3. Center for Environmental Medicine, Asthma, and Lung Biology, University of North Carolina-Chapel Hill, Chapel Hill, North Carolina;
4. Biology Department, Methodist University, Fayetteville North Carolina;
5. Department of Pediatrics, Duke University Medical Center, Durham, North Carolina;
6. Division of Pulmonary and Critical Care Medicine, Department of Medicine, Stanford University Medical Center, Stanford, California; and
7. Division of Pulmonary and Critical Care Medicine, The Feinberg School of Medicine, Northwestern University, Chicago, Illinois