Department of Occupational and Environmental Health, Institute of Public Health, Zhengzhou University, Zhengzhou, Henan, 450001, People's Republic of China. Kaifeng Center for Disease Prevention and Control, Kaifeng, Henan, 475000, People's Republic of China. Department of Occupational and Environmental Health, Institute of Public Health, Zhengzhou University, Zhengzhou, Henan, 450001, People's Republic of China. byyue@zzu.edu.cn.