1. Sanitation and Radiation Laboratory, California Department of Health Services, 2151 Berkeley Way, Berkeley, California 94704, U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Cincinnati, Ohio 45226, Ashland Chemical Inc., 5200 Blazer Parkway, Dublin, Ohio 43017, and Monsanto Company, 800 North Lindbergh Boulevard, St. Louis, Missouri 63167