1. School of Public Health, the Key Laboratory of Environmental Pollution Monitoring and Disease Control, Ministry of Education, Guizhou Medical University, Guiyang, China
2. College of Public Health, Zhengzhou University, Zhengzhou, China
3. Guizhou Provincial Hospital of Maternal and Child Health Care, Guiyang, China
4. Guiyang Center for Diseases Control and Prevention, Guiyang, China