1. Radiation and Health Sciences Division, Directorate of Environmental and Radiation Protection and Assessment, Canadian Nuclear Safety Commission, Ottawa, Ontario, Canada
2. Frost & Frost Consultants, Saskatoon, Saskatchewan, Canada
3. Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, New York
4. Department of Epidemiology and Biostatistics, School of Medicine, University of California, San Francisco, California