1. Department of Occupational and Environmental Health, University of Iowa College of Public Health, Iowa City, Iowa, USA
2. Center for Health Research, Kaiser Permanente Northwest, Portland, Oregon, USA
3. National Health and Environmental Effects Research Laboratory, Human Studies Division, Epidemiology and Biomarkers Branch, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina, USA
4. Department of Biostatistics, University of Iowa College of Public Health, Iowa City, Iowa, USA
5. Department of Environmental and Radiological Health Sciences, Colorado State University College of Veterinary Medicine and Biomedical Sciences, Fort Collins, Colorado, USA
6. Department of Epidemiology, University of Iowa College of Public Health, Iowa City, Iowa, USA