[1] Peking Univ, Sch Publ Hlth, Dept Occupat & Environm Hlth Sci, Beijing 100191, Peoples R China
[2] Baotou Med Coll, Sch Publ Hlth, Dept Occupat & Environm Hlth Sci, Baotou 014030, Inner Mongolia, Peoples R China
[3] Chinese Med Assoc, Editorial Dept Chinese Journal Prevent Med, Beijing 100710, Peoples R China
[4] Peking Univ, Dept Clin Lab, Hosp 3, Beijing 100191, Peoples R China