1. Departments of Epidemiology,
2. Department of Epidemiology, Capital Institute of Pediatrics, Beijing, China; and
3. Nutrition and Food Hygiene,
4. Health Statistics,
5. Social Medicine and Health Service Management, and
6. Toxicology, School of Public Health, Shandong University, Jinan, China;
7. Division of Epidemiology and Community Health, School of Public Health, University of Minnesota, Minneapolis, Minnesota