[1] Beijing Univ Chinese Med, Grad Sch, Beijing, Peoples R China
[2] China Japan Friendship Hosp, Dept Pediat, Beijing, Peoples R China
[3] Chinese Acad Sci, Inst Geog Sci & Nat Resources Res, State Key Lab Resources & Environm Informat Syst, Beijing, Peoples R China
[4] China Japan Friendship Hosp, Inst Clin Med Sci, Beijing, Peoples R China
[5] Peking Univ, Inst Child & Adolescent Hlth, Beijing, Peoples R China
[6] Peking Univ, Sch Publ Hlth, Beijing, Peoples R China
[7] Beijing Chaoyang Dist Maternal & Child Hlth Care, Dept Pediat, Beijing, Peoples R China