1. Department of Epidemiology, University of North Carolina at Chapel Hill (UNC-Chapel Hill), Chapel Hill, North Carolina, USA
2. Department of Population and Public Health Sciences, Keck School of Medicine, University of Southern California, Los Angeles, California, USA
3. Department of Maternal and Child Health, UNC-Chapel Hill, Chapel Hill, North Carolina, USA
4. Department of Geography, UNC-Chapel Hill, Chapel Hill, North Carolina, USA
5. Carolina Population Center, UNC-Chapel Hill, North Carolina, USA
6. Faculty of Health Sciences, Simon Fraser University, Vancouver, British Columbia, Canada
7. Department of Environmental and Occupational Health, Indiana University, Bloomington, Indiana, USA
8. Department of Environmental and Occupational Health, University of California, Irvine, California, USA