1. Department of Molecular and Cellular Biology; Baylor College of Medicine; Houston Texas
2. Birth Defects Epidemiology and Surveillance Branch, Texas Department of State Health Services; Austin Texas
3. National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention; Cincinnati Ohio
4. Department of Pediatrics; Division of Genetics and Metabolism; University of Texas Southwestern Medical Center; Dallas Texas
5. Division of Epidemiology; Human Genetics and Environmental Sciences; University of Texas School of Public Health; Houston Texas
6. Department of Epidemiology; College of Public Health, University of Iowa; Iowa City
7. Department of Pediatrics; Section of Hematology-Oncology, Baylor College of Medicine; Houston Texas