1. Occupational and Environmental Epidemiology Branch, Division of Cancer Epidemiology and Genetics, U.S. National Cancer Institute, Bethesda, Maryland, USA
2. Division of Cancer Epidemiology and Genetics, U.S. National Cancer Institute, Bethesda, Maryland, USA
3. Surveillance Branch, Division of Respiratory Disease Studies, U.S. National Institute for Occupational Safety and Health, Morgantown, West Virginia, USA
4. Information Management Systems, Inc., Rockville, Maryland, USA