Funding for this research was provided by:
National Natural Science Foundation of China (21190051, 41421064, 41121004, 21507166)
Ministry of Science and Technology of the People's Republic of China (2015CB553401)
Collaborative Innovation Center for Regional Environmental Quality
Text and Data Mining valid from 2018-07-04
Received: 28 December 2017
Accepted: 15 June 2018
First Online: 4 July 2018
Ethics approval and consent to participate
: The study was approved by the Institutional Review Board of the Peking University Health Science Center (approval no. 13073), and written informed consent was obtained from all participants before enrollment.
: Not applicable.
: The authors declare that they have no competing interests
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