1. Department of Environmental Health, Rollins School of Public Health, Emory University, Atlanta, Georgia, USA
2. Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, Georgia, USA
3. School of Civil and Environmental Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA
4. Atmospheric Research & Analysis, Inc., Cary, North Carolina, USA
5. Department of Biostatistics and Bioinformatics, Rollins School of Public Health, Emory University, Atlanta, Georgia, USA