1. Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland, USA
2. Iowa Geological Survey, Iowa City, Iowa, USA
3. Department of Biostatistics, Marmara University Medical School, Istanbul, Turkey
4. Southwest Research Institute, San Antonio, Texas, USA
5. Department of Environmental and Radiological Health Sciences, Colorado State University, Fort Collins, Colorado, USA