1. Research Center for Public Health and Preventive Medicine, West China School of Public Health, Sichuan University, Chengdu, China;
2. West China Teaching Hospital, Sichuan University, Chengdu, China;
3. Department of Environmental and Occupational Medicine, West China School of Public Health, Sichuan University, Chengdu, China;
4. School of Humanities and Information Management, Chengdu Medical College, Chengdu, China