1. Department of Epidemiology, Brown University, Providence, Rhode Island 02912, United States
2. Faculty of Health Sciences, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
3. Centers for Disease Control and Prevention, Atlanta, Georgia 30333, United States
4. Department of Epidemiology, Dartmouth College, Hanover, New Hampshire 03755, United States
5. Department of Environmental Health, University of Cincinnati, Cincinnati, Ohio 45267, United States
6. Department of Pediatrics, Cincinnati Children’s Hospital Medical Center, College of Medicine, University of Cincinnati, Cincinnati, Ohio 45229, United States
7. Child and Family Research Institute, BC Children’s and Women’s Hospital, Vancouver, BC, Canada Faculty of Health Sciences, Simon Fraser University, Burnaby, British Columbia V5Z 4H4, Canada