[1] Southern Med Univ, Dept Occupat Hlth & Otcupat Med, Sch Publ Hlth & Trop Med, Guangzhou 510515, Guangdong, Peoples R China
[2] Shenzhen Prevent & Treatment Ctr Occupat Dis, Dept Occupat Hlth Assessment, Shenzhen 518001, Guangdong, Peoples R China
[3] Southern Med Univ, Nanfang Hosp, Dept Resp, Chron Airways Dis Lab, Guangzhou 510515, Guangdong, Peoples R China