1. Department of Environmental Health Sciences, Arnold School of Public Health, University of South Carolina, Columbia, South Carolina 29208
2. Department of Obstetrics and Gynecology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois 60611
3. Department of Human Genetics, The University of Chicago, Chicago, Illinois 60637
4. Key Laboratory of Public Health Safety, Ministry of Education, Department of Environmental Health, School of Public Health, Institution for Water Pollution and Health Research, Fudan University, Shanghai 20032, China