1. Hebei Key Laboratory of Environment and Human Health, School of Public Health, Hebei Medical University, Shijiazhuang, China
2. Department of Occupational and Environmental Health, School of Public Health, Sun Yat-sen University, Guangzhou, China
3. Department of Ultrasonics, The First Affiliated Hospital of Hebei Medical University, Shijiazhuang, China
4. Department of Medical Records, Shijiazhuang Fourth Hospital, shijiazhuang, China