1. School of Public Health; China Medical University; Shenyang, China
2. School of Public Health; North China University of Science and Technology; Tangshan, China
3. School of Public Health; Xinxiang Medical University; Xinxiang, China
4. Department of Pneumoconiosis; Beidaihe Sanitarium for China Coal Miners; Beidaihe, China
5. Heart Institute; North China University of Science and Technology; Tangshan, China