1. Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, USA
2. Channing Laboratory, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts, USA
3. Department of Environmental Health Sciences, University of Michigan School of Public Health, Ann Arbor, Michigan, USA
4. Division of Epidemiology, Statistics, and Prevention Research, National Institute of Child Health and Human Development, National Institutes of Health, Department of Health and Human Services, Rockville, Maryland, USA
5. Departamento de Ecología Humana, Centro de Investigación y de Estudios Avanzados del I.P.N., Unidad de Mérida, Mérida, Yucatán, México
6. Centro de Investigación de Salud Poblacional, Instituto Nacional de Salud Pública, Cuernavaca, Morelos, México
7. Departments of Environmental Health Sciences and Epidemiology, Bloomberg School of Public Health and
8. Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland, USA