1. Key Laboratory of Environment and Health, Ministry of Education & Ministry of Environmental Protection, and State Key Laboratory of Environmental Health (incubating), School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, PR China.
2. Department of Maternal and Child Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, No. 13 Hangkong Road, Wuhan 430030, Hubei, PR China.
3. Center for Statistics in Medicine, NDORMS, University of Oxford, The Botnar Research Centre, Oxford, UK.
4. School of Population Medicine and Public Health, Chinese Academy of Medical Sciences/Peking Union Medical College, No. 31, Beijige-3, Dongcheng District, Beijing 100730, PR China.