1. Center for Population Health Research, Instituto Nacional de Salud Pública, Cuernavaca, Morelos, México
2. Epidemiology Branch and
3. Biostatistics Branch, National Institute of Environmental Health Sciences, National Institutes of Health, Department of Health and Human Services, Research Triangle Park, North Carolina, USA
4. Subsecretaría de Promoción y Prevención de la Salud. Ministry of Health, México City, Mexico
5. Centre de Toxicology, Institut National de Santé Publique du Québec, Québec, QC, Canada