1. Medical Department, 3M Company, St. Paul, Minnesota, USA;
2. Department of Epidemiology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA;
3. George W. Comstock Center for Public Health Research and Prevention, Johns Hopkins University, Baltimore, Maryland, USA;
4. Prevention and Research Center, Women’s Center for Health and Medicine, Mercy Medical Center, Baltimore, Maryland, USA;
5. Environmental Laboratory, 3M Company, St. Paul, Minnesota, USA