1. Consultants in Epidemiology and Occupational Health, Inc. (CEOH, Inc.), Washington, D.C. and MotherRisk, Division of Clinical Pharmacology/Toxicology, The Hospital for Sick Children, Toronto, Ontario, Canada
2. Johns Hopkins School of Hygiene and Public Health, Johns Hopkins University, Baltimore, Maryland
3. Consultants in Epidemiology and Occupational Health, Inc. (CEOH, Inc.), Washington, D.C. and Johns Hopkins School of Hygiene and Public Health, Johns Hopkins University, Baltimore, Maryland
4. Biochemistry, Molecular Biology and Pediatrics, Child Health, Howard University College of Medicine, Washington, D.C.