1. 1Epidemiology Program, Public Health Sciences Division, Fred Hutchinson Cancer Center, Seattle, Washington.
2. 2Department of Epidemiology, University of Washington, Seattle, Washington.
3. 3Epidemiology Branch, Division of Intramural Research, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina.
4. 4Occupational and Environmental Epidemiology Branch, Division of Cancer Epidemiology and Genetics, NCI, NIH, Department of Health and Human Services, Bethesda, Maryland.