1. Cancer Prevention Program, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109
2. Department of Epidemiology, University of Washington, Seattle, Washington 98195
3. Lnterdisciplinary Program in Nutritional Sciences, University of Washington, Seattle, Washington 98195
4. Department of Chemistry, University of Helsinki, Helsinki, Finland 00014
5. Epidemiology Program, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109