a
Department of Occupational and Environmental Health Sciences, School of Public Health, Peking University, Beijing 100191, P. R. China
E-mail: jiaguangjia@bjmu.edu.cn
;
Fax: +86 10 8280 2333
;
Tel: +86 10 8280 2333
b
Jinan Municipal Center for Disease Control and Prevention, Jinan 250013, P. R. China
c
Henan Provincial Institute of Occupational Medicine, Zhengzhou 450052, P. R. China
d
Department of Clinical Laboratories, Third Hospital of Peking University, Beijing 100191, P. R. China