1. Instituto Nacional de Salud Pública, Cuernavaca, México
2. Environmental Epidemiological Research Centre (CREAL), IMIM, Barcelona, Spain
3. Hospital Infantil de México, Federico Gómez, Mexico, D.F., Mexico
4. Comisión Federal de Protección contra Riesgos Sanitarios (COFEPRIS), México, D.F. Mexico
5. Department of Pulmonary Allergy and Critical Care, Emory University School of Medicine, Atlanta, Georgia, USA
6. Human Studies Division, U.S. Environmental Protection Agency, Chapel Hill, North Carolina, USA
7. Department of Occupational and Environmental Medicine, Sahlgrenska University Hospital, Gothenburg, Sweden