1. Department of Epidemiology and Biostatistics, Texas A&M University, College Station, TX 77843, USA
2. Department of Geology and Geophysics, Texas A&M University, College Station, TX 77843, USA
3. Interdisciplinary Graduate Program in Human Toxicology, University of Iowa, Iowa City, IA 52242, USA
4. Department of Occupational and Environmental Health, University of Iowa, Iowa City, IA 52242, USA
5. Department of Biostatistics, University of Iowa, Iowa City, IA 52242, USA
6. Center for Health Effects of Environmental Contamination, University of Iowa, Iowa City, IA 52242, USA