1. Department of Epidemiology, and
2. Department of Environmental Sciences and Engineering, University of North Carolina at Chapel Hill, Gillings School of Public Heath, Chapel Hill, North Carolina, USA
3. Facultad de Medicina,Universidad Juárez del Estado de Durango, Gómez Palacio, Durango, México
4. Carolina Population Center, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA
5. Department of Nutrition, and
6. Department of Biostatistics, University of North Carolina at Chapel Hill, Gillings School of Public Heath, Chapel Hill, North Carolina, USA