1 Ministry of Education and Shanghai Key Laboratory of Children's Environmental Health, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
2 Department of School Health, Food Nutrition and Safety, Pudong New Area Center for Disease Control and Prevention, Shanghai, China.
3 Ministry of Education and Shanghai Key Laboratory of Children's Environmental Health, Xinhua Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China; Population Health Sciences, Bristol Medical School, University of Bristol, Bristol, UK. Electronic address: zhaojian@xinhuamed.com.cn.